4A-GTE -- for fuel efficiency?

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Rogue-AE95
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4A-GTE -- for fuel efficiency?

Postby Rogue-AE95 » Sat Jul 11, 2015 10:30 am

Has anyone tried this? Any ideas or theories on how to go about this? Recently I've been intrigued by an acquaintance's Honda D15 (1.5 liter, SOHC, non-VTEC, 8 valve) fuel efficient build. He also built another 1.5l, but with a less-common 16v head that has one almost-closed intake valve per cylinder at lower RPMs (uses VTEC at higher RPMs to open all valves normally), which induces a swirl effect in the combustion chamber. With the 8v head he achieved between 50-70 MPG, depending on driving style and city/hwy or mostly hwy. He did this using a small turbo, driving style (trying to keep his foot out of the floor), porting the head, and leaning out the fuel/air mixture as much as possible.

So has anyone heard about building up a super fuel efficient 4A-GTE, despite being a performance-oriented engine? Granted there's the 4A-FE, but I'm more interested in the GTE idea since there are more aftermarket options for parts and more easily-acquired engine management. I was thinking smallport head, stock intake & injectors, stock (late bigport/smallport) cams, and the 9.4:1 pistons (tops & skirts coated). This would allow for regular octane gas, unless there's a way to tune the smallport pistons to run with it instead of higher octane. Then there's the turbo choice, of which I know very little, only that it shouldn't be "too big" or "too small." T28?

As far as what car to throw it in, I suppose just about any 80s Corolla would be pretty light, along with the AW11 MR2 and the FX. The FX would probably be ideal if it's lighter than an AW11. Plus, a little more practical.

Thoughts? And what kinds of mileage do you guys get when you throw a turbo on an otherwise-stock GE, and drive it "normal?"

http://www.autospeed.com/cms/article.html?&A=109931
'88 Corolla All-Trac

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Sat Jul 11, 2015 6:48 pm

Basically what you are talking about is maximizing BSFC. Your idea of low compression pistons is going to be a major hit to that.
Compression is one of the best things you can do to maximize BSFC.
For example my AW11 with the stock GZE got about 22 MPG city or moderately hard driving and about 28 highway It was about the same SC and after I converted it to turbo. When I threw in my BT that went to about 28 city/hard driving and about 34 highway. Same ECU, same trans, same car.
Some of this could be attributed to the efficiency of the head but I really doubt it is.
Now the turbo it's self cannot improve efficiency. Again going back to my BT build it got the same gas mileage before hooking up the turbo wastegate as it did after it was boosting. As long as I was driving normally. If you are WOT all the time the turbo gives you the ability to move more air and therefore more fuel. So a turbo does not improve efficency. What a turbo allows you to do is run a smaller motor keeping the efficiency of that smaller motor and making the power of a bigger motor.

If I were going for a fuel efficient build I would definitely go high compression.
One thing I haven't studied is maximizing cams for fuel efficiency. In fact I have seen very little aftermarket discussion on the subject. I do believe you could do better than the stock cams though. One thing to remember is that if done right and paired with the proper compression a bigger cam may not mean less efficiency in your cruising range. In fact a bigger cam that moves the VE up in the RPM curve means you need to use more throttle at lower RPM to hit your cruising speed and more throttle can mean less pumping loss.
So as far as internals go just like with a performance build picking the proper cams and compression would be key. Head work would also help.
Then it really depends on how far you want to take it. Want to try to integrate direct injection? that would help. Other things like VVT/vtech would help.
Custom intake and exhaust would help but these are the kinds of things that would need a lot of testing and development.
So adding a turbo to the above setup wouldn't give you any more efficiency but it would give you the power of a bigger motor without loosing any significant MPG.
Now if you would be happy with say 150 CHP you might be able to do something like an 8A hybrid or for that matter just take an 8AFE and increase compression as much as possible and then throw just a little boost at it to take it from 86 hp up to 150 hp. Now you have Silvertop ish power out of a 1.3 liter motor.

The other thing to remember is that the motor is just a small fraction of the equation and honestly not the most important.
More than a decade ago I read about a group that dropped something like a 200 hp Integra motor into an Insight and got something like 50+ MPG out of it. This is because the chassis is so light and so aerodynamic that the motor barely needs to work to go. The other vital thing is gearing. Take an Insight motor and slap it up to a C52 and throw it in an AW11 and a motor that gets 60-100 MPG in an insight will now get 35-45. This is because the chassis is not aerodynamic. The transmission is geared for performance not economy and the package is not well tailored to the goal.
If you want to make maximum efficiency out of a 4AGE drop it into an Insight with good economy gearing. Do that and do it right and I bet you can get over 60 MPG.
Stick it in any motor that originally came with an A series motor and it will be a struggle to get significantly better MPG than a stock 20v with an economy trans would get.

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Re: 4A-GTE -- for fuel efficiency?

Postby jondee86 » Sun Jul 12, 2015 12:48 am

When you have the engine sorted, drop it in something like this...

Image
http://ecomodder.com/forum/showthread.php/aerocivic-how-drop-your-cd-0-31-0-a-290.html

Cheers... jondee86
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Re: 4A-GTE -- for fuel efficiency?

Postby Deuce Cam » Sun Jul 12, 2015 10:31 am

Slap a 4afe in an fx with 155 tires and you'll easily get 40+ mpg out of the gate. It might even be possible to reach 50 mpg without tearing into the engine by doing some other things.

This dude got 118 mpg in a crx, but probably not something you'd want to drive around in: http://ecomodder.com/blog/20-yearold-mo ... onomy-run/ .

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Re: 4A-GTE -- for fuel efficiency?

Postby ogdougynutty » Sun Jul 12, 2015 11:21 am

Using a turbo can definitely give you great milage. I know a couple d15 hondas that get around 68mpgs with turbos and when you whack on it, it still makes 230hp. It's all on how YOU drive it. With turbos you preferably don't want run an intercooler if possible. Raising the intake temp helps the fuel get closer to it's flash point and gives a little bit better flame propagation. Then using the turbo to keep the intake manifold pressures at 0. This reduces pumping losses in the motor leading to better mugs.
Last edited by ogdougynutty on Sun Jul 12, 2015 12:49 pm, edited 1 time in total.

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Re: 4A-GTE -- for fuel efficiency?

Postby TwamTuning » Sun Jul 12, 2015 12:02 pm

What would be the point in putting in the money and effort fitting a turbo to try and get m.p.g? Take it from me, once you feel the boost you will drive it harder, and if fitting a blow off valve you will want to listen to it all the time lol. Moat of us fit turbo's for power, speed, and most of all fun. Never thought I would meet someone who wants m.p.g and to drive it easy. Especially a steer from the rear 4age member lol.
Each to their own I guess.

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Re: 4A-GTE -- for fuel efficiency?

Postby oldeskewltoy » Mon Jul 13, 2015 8:05 am

BSFC - https://en.wikipedia.org/wiki/Brake_spe ... onsumption


I currently have a friend who hyper miles his AE86 on occasion. He has achieved over 40 mpg in a mostly stock AE86. So, if you optimize the build, run AFRs around 16+, have either a functioning(possibly custom controlled) EGR system, or VVTi, to introduction exhaust into the intake stream (to minimize the oxygen, which will slow the burn)... add the proper gearing(based on dyno time) to find the engines optimal efficient rpm range... you might crack 75ish mpg
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Re: 4A-GTE -- for fuel efficiency?

Postby Deuce Cam » Mon Jul 13, 2015 10:43 am

ogdougynutty wrote:Then using the turbo to keep the intake manifold pressures at 0. This reduces pumping losses in the motor leading to better mugs.


I'm trying to understand this. Manifold pressure won't stay at 0 on it's own. Are you referring to observing a boost / vacuum gauge and altering driving habits to try and keep it near 0?

The comment got me thinking about how a turbo would actually increase fuel efficiency. I know these days a lot of the oem's just slighly delay the transition to open loop at the onset of boost. It's good for emissions and fuel economy but bad for engine reliability because in some cases the a/f ratio is still lean under boost / high load (obviously not a concern for a hyper miler). Anyway, I'm sure there's a lot more to it (especially via a diy approach) so I'm curious.

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Mon Jul 13, 2015 12:15 pm

Deuce Cam wrote:
ogdougynutty wrote:Then using the turbo to keep the intake manifold pressures at 0. This reduces pumping losses in the motor leading to better mugs.


I'm trying to understand this. Manifold pressure won't stay at 0 on it's own. Are you referring to observing a boost / vacuum gauge and altering driving habits to try and keep it near 0?

The comment got me thinking about how a turbo would actually increase fuel efficiency. I know these days a lot of the oem's just slighly delay the transition to open loop at the onset of boost. It's good for emissions and fuel economy but bad for engine reliability because in some cases the a/f ratio is still lean under boost / high load (obviously not a concern for a hyper miler). Anyway, I'm sure there's a lot more to it (especially via a diy approach) so I'm curious.

His post didn't make any sense to me. Using the turbo to keep the manifold pressure at zero makes no sense.
Like I said though adding a turbo will not improve gas mileage. It just gives you the ability to make more power on a smaller displacement motor and running a smaller displacement motor can improve your gas mileage.

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Re: 4A-GTE -- for fuel efficiency?

Postby ogdougynutty » Mon Jul 13, 2015 1:33 pm

Deuce Cam wrote:
I'm trying to understand this. Manifold pressure won't stay at 0 on it's own. Are you referring to observing a boost / vacuum gauge and altering driving habits to try and keep it near 0?


Yeah you got what i was saying. I had it pictured in my head but if forget that people dont have access to that lol. I was just referring to looking at a boost/vacuum gauge and talking about the "0" point on that.

yoshimitsuspeed wrote:His post didn't make any sense to me. Using the turbo to keep the manifold pressure at zero makes no sense.
Like I said though adding a turbo will not improve gas mileage. It just gives you the ability to make more power on a smaller displacement motor and running a smaller displacement motor can improve your gas mileage.


Usually my posts turn into weird ramblings because i will start writing something get too lazy to finish it. Snip out some stuff and keep it, which just makes everything worse. So this time i will actually finish.

Using a turbo CAN improve gas mileage, but you can't use the conventional thinking that people have with turbos. Using it to build pressure in the intake to make more power. Which goes along with what you said on using turbos on a small displacement motor. Giving it more power so it feels like a bigger motor but not using as much fuel.

Using turbos in a true fuel efficiency standpoint is a different story. The turbo is there to help reduce pumping losses in the motor. Taking what would be waisted energy in a N/A motor in the form of exhaust gases. To pressurize the intake to exactly what the motor needs on the intake stroke. (i.e. my "0" in the vacuum/pressure gauge). So the motor doesn't have to use energy from the expansion stroke of another cylinder to pull in the intake charge (vacuum).

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Mon Jul 13, 2015 2:49 pm

ogdougynutty wrote:Usually my posts turn into weird ramblings because i will start writing something get too lazy to finish it. Snip out some stuff and keep it, which just makes everything worse. So this time i will actually finish.

Using a turbo CAN improve gas mileage, but you can't use the conventional thinking that people have with turbos. Using it to build pressure in the intake to make more power. Which goes along with what you said on using turbos on a small displacement motor. Giving it more power so it feels like a bigger motor but not using as much fuel.

Using turbos in a true fuel efficiency standpoint is a different story. The turbo is there to help reduce pumping losses in the motor. Taking what would be waisted energy in a N/A motor in the form of exhaust gases. To pressurize the intake to exactly what the motor needs on the intake stroke. (i.e. my "0" in the vacuum/pressure gauge). So the motor doesn't have to use energy from the expansion stroke of another cylinder to pull in the intake charge (vacuum).


That doesn't work out. The throttle is used to limit the power the motor produces. If the motor makes 60 KW at your cruising RPM but it only takes 30 KW to maintain the speed then you use partial throttle to limit the motor to making 30 KW.
If the turbo overcame that and you were making 0 PSIG after the throttle plate then the motor would be making 60 KW and would start accelerating. More importantly you would be using air and fuel required to make 60 KW when you only need 30.

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Re: 4A-GTE -- for fuel efficiency?

Postby ogdougynutty » Mon Jul 13, 2015 11:05 pm

yoshimitsuspeed wrote:
That doesn't work out. The throttle is used to limit the power the motor produces. If the motor makes 60 KW at your cruising RPM but it only takes 30 KW to maintain the speed then you use partial throttle to limit the motor to making 30 KW.
If the turbo overcame that and you were making 0 PSIG after the throttle plate then the motor would be making 60 KW and would start accelerating. More importantly you would be using air and fuel required to make 60 KW when you only need 30.


So at full throttle and at partial throttle you giving the engine the same amount of fuel??? That's not how it works. You won't begin just accelerating because you won't be giving it enough fuel to accelerate.

And i find it weird you just straight throw out a statement like "adding a turbo cannot increase gas mileage". There have been plenty of builds that use turbos to increase millage. If I remember correctly back in like 2005 a group of people turbo'ed a prius with an EJ20 turbo specifically for mileage. With the proper tuning and driving they saw around a 20% increase in mileage. There are plenty other builds out there on the ole interwebs using turbos for mileage, just have to look.

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Tue Jul 14, 2015 9:04 am

ogdougynutty wrote:
yoshimitsuspeed wrote:
That doesn't work out. The throttle is used to limit the power the motor produces. If the motor makes 60 KW at your cruising RPM but it only takes 30 KW to maintain the speed then you use partial throttle to limit the motor to making 30 KW.
If the turbo overcame that and you were making 0 PSIG after the throttle plate then the motor would be making 60 KW and would start accelerating. More importantly you would be using air and fuel required to make 60 KW when you only need 30.


So at full throttle and at partial throttle you giving the engine the same amount of fuel??? That's not how it works. You won't begin just accelerating because you won't be giving it enough fuel to accelerate.


This depends on a lot of variables but essentially on a gasoline motor the fuel is supplied based directly on how much air is supplied. Without making major modifications to the motor you can't lean it out significantly and still keep the motor happy. There is also a serious point of power loss when you lean out too much. You can lean out a little without loosing much power but not a lot. Also as you lean out you will eventually need to pull timing to prevent detonation. Leaning out and retarding timing both make EGTs higher risking burning valves and melting pistons. This is not a diesel where you can put as much air in as you want and throttle the motor with the gas pedal.

If you study Toyota or Honda's lean burn technology you will realize that it takes a lot of supporting innovation and technology to get it working right and to have notable influence on MPG. This is completely aside from boost and when it comes to MPG find me one of them that uses a turbo on one of their lean burn engines. If the OEMs don't do it then why don't they?

ogdougynutty wrote:And i find it weird you just straight throw out a statement like "adding a turbo cannot increase gas mileage". There have been plenty of builds that use turbos to increase millage. If I remember correctly back in like 2005 a group of people turbo'ed a prius with an EJ20 turbo specifically for mileage. With the proper tuning and driving they saw around a 20% increase in mileage. There are plenty other builds out there on the ole interwebs using turbos for mileage, just have to look.


Adding a turbo gives you the ability to move more air. More air doesn't do any good until you add more fuel.
Your comment about using the turbo to make 0 PSIG boost still doesn't add up because even if you used the fuel to throttle the motor it would still be more efficient to do that without a turbo and just hold the throttle at WOT to create no intake vacuum and then control fuel to control power. This method just doesn't work well on gasoline motors though.
If this is your goal then install a 1NZXFE that can use cam timing to throttle the motor and allow more throttle input and less pumping loss. It would also respond better to lean burn tuning since it was designed for it.
Now if the NZ doesn't produce enough power for your liking you could turbo it to gain more power with minimal MPG loss but you wouldn't see a gain.
If you can find a source that proves otherwise I would love to see it.

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Re: 4A-GTE -- for fuel efficiency?

Postby ogdougynutty » Tue Jul 14, 2015 2:05 pm

You tell me to study lean burn technologies and using that argument pretty much proved me correct. Lean Burn is just keeping the throttle as open as possible to reduce pumping losses (remember this) and giving it very little fuel so it won't accelerate.

Now instead of throttle position lets use a turbo. If you have a turbo that is keeping the intake manifold out of vacuum (at the "0" or even a little pressurized) at cruising rpm. It once again reduces pumping losses (hey there it is) but at the same time it is getting very little amount of fuel so it won't accelerate. When i say little fuel I'm talking about 20:1 AFRs. Also in these conditions you don't pull timing you actually increase it. Because lean charges are very difficult to ignite, so timing will be at 40 BTDC in those conditions ( which has an added benefit of reducing EGTs)

And i love it how people think that using the argument of "just because so-and-so doesn't use it, it must not work". But you seem to be overlooking that companies have very strict rules and regulations to meet. The problem with lean burn cars is that they are not very friendly at the pipe. But to the individual DIY'er they have zero rules to follow.

But just to poke some more fun at this. Lets look at the new civic type r. They kept the same size motor (still a 2.0 L) but added a turbo and were able to get an increase in mileage.

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Re: 4A-GTE -- for fuel efficiency?

Postby oldeskewltoy » Tue Jul 14, 2015 2:50 pm

a KEY to lean burn and running AFR's above 17 is to introduce LESS oxygen... why EGR is a good thing, since you introduce already burnt gasses into the intake stream to reduce the amount of oxygen in the mix.....
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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Tue Jul 14, 2015 4:07 pm

ogdougynutty wrote:You tell me to study lean burn technologies and using that argument pretty much proved me correct. Lean Burn is just keeping the throttle as open as possible to reduce pumping losses (remember this) and giving it very little fuel so it won't accelerate.


My point is that there is a lot more to it than that. There is a reason it has taken so long to get motors that run much leaner than stoich and gain efficiency in doing so. Extremely lean AFRs may need more timing. I do not know a lot about the details on this however somewhat lean AFRs can lead to very high combustion temps and greater risk of detonation so doing it right wold really take careful tuning knowing where to pull timing and where you could add it.

ogdougynutty wrote:Now instead of throttle position lets use a turbo. If you have a turbo that is keeping the intake manifold out of vacuum (at the "0" or even a little pressurized) at cruising rpm. It once again reduces pumping losses

The turbo compressing air (doing work) on the inlet side will require the turbine absorbing energy on the exhaust side. The result is increased pressure before the turbine. IE a new pumping loss.

ogdougynutty wrote:You tell me to study lean burn technologies and using that argument pretty much proved me correct. Lean Burn is just keeping the throttle as open as possible to reduce pumping losses (remember this) and giving it very little fuel so it won't accelerate.

Now instead of throttle position lets use a turbo. If you have a turbo that is keeping the intake manifold out of vacuum (at the "0" or even a little pressurized) at cruising rpm. It once again reduces pumping losses (hey there it is) but at the same time it is getting very little amount of fuel so it won't accelerate. When i say little fuel I'm talking about 20:1 AFRs. Also in these conditions you don't pull timing you actually increase it. Because lean charges are very difficult to ignite, so timing will be at 40 BTDC in those conditions ( which has an added benefit of reducing EGTs)

There is a difference between hard to ignite and a stable predictable burn. It should also be noted that a lot of advance also means much of the combustion process happening before TDC which is another pumping loss because the piston is pushing up against the expanding combustion. That is neither here nor there because it has nothing to do with the thread subject of using a turbo. Since we are talking about not making boost the turbo is nothing but an intake and exhaust restriction.

ogdougynutty wrote:But just to poke some more fun at this. Lets look at the new civic type r. They kept the same size motor (still a 2.0 L) but added a turbo and were able to get an increase in mileage.


This does not prove that the turbo is what gained the MPG. Every generation Honda strives for improvements in MPG. It could be a hundred little changes that all equate to a small gain. Had they stayed NA maybe that gain would have been the same or even greater.

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Tue Jul 14, 2015 4:15 pm

oldeskewltoy wrote:a KEY to lean burn and running AFR's above 17 is to introduce LESS oxygen... why EGR is a good thing, since you introduce already burnt gasses into the intake stream to reduce the amount of oxygen in the mix.....


With fixed cam timing EGR is a good benefit and is a great way to help control combustion temps and preignition. Modern motors like the NZXFE can do this on a much more advanced level via cam timing and overlap.

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Re: 4A-GTE -- for fuel efficiency?

Postby Rogue-AE95 » Tue Jul 14, 2015 7:38 pm

Thanks for the replies guys. Keep 'em coming.

OGdougynutty said something that my friend had mentioned, about the turbo reducing pumping losses.
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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Tue Jul 14, 2015 8:35 pm

Rogue-AE95 wrote:Thanks for the replies guys. Keep 'em coming.

OGdougynutty said something that my friend had mentioned, about the turbo reducing pumping losses.

It will reduce pumping losses on the intake and will add them in the exhaust.
A big turbo will have about a 1:1 pressure ratio between compressor side and turbine side. If you are running 5 PSIG boost that means you would have about 5 PSIG pre turbine backpressure.
A small turbo like mine goes over a 2:1 ratio at high boost. This means that at 6 PSIG boost at redline hits 13 PSI pre turbine backpressure. Granted it's still not much above 1:1 at cruising RPM but the pressure on the exhaust side is still higher than the pressure on the intake side.

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Re: 4A-GTE -- for fuel efficiency?

Postby ogdougynutty » Thu Jul 16, 2015 9:50 am

yoshimitsuspeed wrote:It will reduce pumping losses on the intake and will add them in the exhaust.


I like how you worded that. The way you state it is like all the energy saved on the intake stroke is used to spin the turbo. While I'm not arguing the fact it takes energy to spin the turbo, it does. But what i can say is this:

(the energy required to spin the turbo) << (the energy saved on the intake stroke and by heating up the intake charge)

Now to explain my reasoning behind that statement. It would be great to pair numbers with those statements. BUT, I'm pretty sure no one here has the equipment to do the required experiments and measurements. With the right information I could calculate some of the stuff to give a rough estimate (like for the turbo and intake charge) but not for the intake stroke.

That is why sometimes it is just easier to use the results of experiments for proof. Now with people that have set out to improve milage with a turbo and have seen increased milage (from what i have seen around 20% or more)

So this means one of two things about my statement either

a) my statement is false and people have built physics defying machines

or

b) my statement holds true

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Re: 4A-GTE -- for fuel efficiency?

Postby Rogue-AE95 » Thu Jul 16, 2015 4:54 pm

Turbo for gas mileage... intercooler or no intercooler? You mentioned heating the intake charge, and OST mentioned routing some exhaust into the intake. Would running without an intercooler help with mileage?
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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Thu Jul 16, 2015 6:27 pm

ogdougynutty wrote:
yoshimitsuspeed wrote:It will reduce pumping losses on the intake and will add them in the exhaust.


I like how you worded that. The way you state it is like all the energy saved on the intake stroke is used to spin the turbo. While I'm not arguing the fact it takes energy to spin the turbo, it does. But what i can say is this:

(the energy required to spin the turbo) << (the energy saved on the intake stroke and by heating up the intake charge)


I do not know thermodynamics equations well enough to argue against this but I am confident that even if it's possible it would take filling in a lot of variables with very specific solutions to make it work.
Basically you are talking about adding a restriction in both the intake and exhaust and creating more heat to save energy. Now yes you are taking heat from the exhaust side and putting it back into the intake side but there are always losses when converting energy.
Now if heating up the air charge is really what is gaining the efficiency then it would be more efficient to wrap your exhaust around your intake to directly heat up the intake charge without introducing the restriction and trying to convert heat and pressure into mechanical energy and then mechanical energy back into heat and pressure.

This brings us to Rogue-AE95s question and the answer is that yes some times heating the intake charge can improve efficiency but again it depends on a ton of other variables and designing a complete system that is optimized to work like that.
Too much heat might cause detonation requiring you to pull too much timing which could reduce your BSFC. Then there is how everything ties in together. Are you going to go lean burn with heated exhaust and EGR? If so then how much of which will be ideal? What if one causes issues with the others?
Now if we are going to get into this level of trying to maximize efficiency you would be much better off looking for info somewhere like eng-tips.com where engineers who actually understand the thermodynamics concepts and have studied this can give some input. Even then it's a lot to take in. You could go to get a masters on this subject and when you were done with your education just be beginning to have enough understanding to start learning how to really implement this.

Now sure you could get into these things and just mess around with trial and error and you would learn a lot and could very well gain a lot. Probably not as much as swapping in a motor engineered to do this but maybe close.
I still stand by my belief that a turbo would do nothing or at least so little it would not be a focus for me as far as increasing MPG.



ogdougynutty wrote:
a) my statement is false and people have built physics defying machines

or

b) my statement holds true


Or C) not enough information.

Show me a build where someone did nothing but bolted a turbo to their car and gained MPG.

If anything else was done then too many variables have been changed unless it is well documented and various iterations have been tested to show how it would not be possible without the turbo.

This is the problem with most car culture and "car science". There is not enough documentation or testing for most builds to actually prove what people want it to prove.
This is exactly why car people believe dynamic compression ratio actually means something and that torque on it's own actually does anything.

I wish I knew enough about the laws of physics and thermodynamics to argue a more legit counterpoint but unless you can yourself my only argument is that both our arguments are invalid.

I am confident enough though to say that if there are any gains to be had in BSFC from running a turbo you would have to have a very good understanding of those laws and how to fill in all those variables quite well to have any chance of reaping any notable reward from it.

I would also be confident saying that if you can build a 4AGE that gets X MPG boosted that I could make an NA 4AGE that does as well or better.

Oh and a final point. Using a turbo to heat up the air only works if you are making boost. Heat comes from increasing pressure and the adiabatic efficiency of the compressor. If heat is the main goal there are much more efficient ways of taking exhaust heat and transferring it to the intake charge.

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Thu Jul 16, 2015 8:21 pm

I just realized that I have gotten too caught up in trying to argue against others points and would be better left trying to make my own.

Let's look at this from another perspective.
There is a big downside to a turbo. In fact let's change that to say that there is a major downside to the internal combustion engine in general. It is not well suited to varying conditions in pressure and RPM.
On the note of pressure. The gasoline ICE needs a throttle to regulate air and therefor power. Yes you can regulate fuel to regulate power to a small degree however you still need a throttle. At least in any conventional system. I still want to develop a conversion kit for pneumatic or solenoid valvetrain for the 4AGE but that's another topic altogether.
So with a throttle you are limiting the amount of air going into the motor by controlling pressure and density. This is where it becomes useful to separate mass airflow and volumetric airflow.
It is also important to pay attention to absolute pressure and gauge pressure. Remember that at sea level you have 100 KPA absolute pressure. 50 KPA boost gives you 150 KPA absolute pressure.
So let's say at WOT and atmospheric pressure of 100 KPA a motor has 10 kg/m air going through it. Now if you throttle back until the plenum pressure is 50 KPA the motor will have 5 KG/m of air going through it.
Since that air has to fill the same volume inside the combustion chamber the pre ignition cylinder pressure will be half that of the motor at WOT. Half the cylinder pressure (effective compression) means a less complete burn and less energy is extracted from the charge. A motor that is designed to handle air coming in at 100 KPA is inherently not optimized for 50 KPA.
Now lets add a turbo and run 50 KPAG (gauge pressure or boost pressure) or 150 KPAA (absolute pressure). Now you have 50% higher pressure in the combustion chamber. So now your motor has to be tuned to handle that type of cylinder pressure.

Next let's look at compression.
Compression is one of the biggest things you can do to improve BSFC and therefore MPG. Compression is the main (Nearly sole) reason the NA 4AGE gets about 5% better MPG than the GZE, the SP get's probably 5% better MPG than the LP and why the 20 valves get 5% better MPG than the smallport.
Now you might say it has to do with other things like engine management but on the GZE ECU my GZE got about 28 highway if I really babied it. My BT on the same ECU can hit 36. Not bad for a motor controlled by an ECU 4 generations it's senior running a motor far different than it was designed for.
Yes some of it will have to do with port design, intake design, cams etc but the majority of the gain is the compression. Throw 11:1 pistons in a largeport and if you can keep it from detonating you should see similar gains.

Here's the problem. A turbo isn't always boosting. In fact the only time it's really working at all is at high load which isn't often in an economy cars life. This is especially true if the motor was big enough to do the job in NA form.
So you are driving down the highway at 50 MPH. In the NA car you only use half throttle and let's pretend that translates directly to 50 KPAA inlet pressure.
Now do the same in the turbo car. You are still at half throttle. You are still at 50 KPA inlet pressure. So the turbo is only acting as an inlet restriction. If it's small enough to spool it will be pushing boost at a mostly closed throttle plate and will actually require you to close the throttle further because there is a greater pressure ratio. This means that the turbo is doing work IE using energy to do nothing. All the while the motor has the same 50 KPA inlet pressure to maintain speed.

The difference is that the motor that was designed for 100 KPA inlet pressures can run higher compression. More compression means better BSFC and better MPG.
If I can run my 20v at 11:1 compression and 50 KPA boost then I should be able to run it NA at 12:1. That increase in efficiency will net me more especially at partial throttle and light load than any gains from running boost ever would.

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Re: 4A-GTE -- for fuel efficiency?

Postby jinx » Fri Jul 17, 2015 3:37 pm

4AGTE gotta run rich in boost, so u will drink fuel.
I'd rather pursue a bigger displacement motor that produces strong torque in the rpm range most used.
Perhaps a lightwt sr20DE, or 7A on megasquirt etc
The formula works. When u considersome buick 3800 V6s reportedly approach 40mpg in 3500 pound whales (pontiac grand prix)
Heck I'd love to have a normally aspirated well tuned 3800 Buick V6 in a daily driven corolla. Geared properly, I have no doubt it'll knock down 50+mpg. An added bonus would be, that a slight tap on the throttle would press you firmly in the seat.
A torquey motor can work wonders in the right application

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Fri Jul 17, 2015 8:18 pm

jinx wrote:4AGTE gotta run rich in boost, so u will drink fuel.
I'd rather pursue a bigger displacement motor that produces strong torque in the rpm range most used.
Perhaps a lightwt sr20DE, or 7A on megasquirt etc
The formula works. When u considersome buick 3800 V6s reportedly approach 40mpg in 3500 pound whales (pontiac grand prix)
Heck I'd love to have a normally aspirated well tuned 3800 Buick V6 in a daily driven corolla. Geared properly, I have no doubt it'll knock down 50+mpg. An added bonus would be, that a slight tap on the throttle would press you firmly in the seat.
A torquey motor can work wonders in the right application


Bigger displacement will tend to reduce gas mileage.
Also making more power in the cruising area of the map means you will use less throttle and again increase pumping losses and reduce efficiency in that range. A motor soley optimized for MPG would run WOT at cruise and make just enough power to maintain it. There is a reason that all the cars like the Prius, Insight, Smart etc all cars designed to get great gas mileage use small displacement motors.
Also torque is irrelevant until you apply RPM. Then you can quantify how much work it does over time. IE power.

Where do you get that 40 MPG figure? Looks like the latest gen Grand prix gets about 25mPG on average.
http://www.fueleconomy.gov/feg/PowerSea ... rchtyp=ymm

Top MPG cars are all small displacement.
http://www.fueleconomy.gov/feg/topten.jsp

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Re: 4A-GTE -- for fuel efficiency?

Postby jinx » Fri Jul 17, 2015 9:23 pm

sorting thru GM tuner forums you'd be amazed at what actual mileage they wring outta those motors.
I'm not only talking about the normally aspirated L36, but the supercharged L67 as well.
Actual mpg..... not some rating agency
Quick example; 37mpg auto tranny bone stock http://www.gmtuners.com/85FieroL36/index.htm

A n.a 3800 is relatively compact and used in a lot of rwd rolla swaps down under. Its that effortless 200+ ft-lbs of midrange tq that makes it more lethal than even a full tilt gze.
Pulls strong from just off idle. No puny small displacement gonna give u such perf/response, plus mpg in a package imo

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Fri Jul 17, 2015 10:07 pm

One instance is meaningless especially when it doesn't contain any information. It says best MPG. That could mean one day driving downhill with a tailwind they got 37 MPG.
Fueleconomy.gov has a number of user avg mpg reports and they average around 20 MPG.

Fuelly has 36 Fieros. I didn't look to see which are V6 but the highest is 31 MPG and the average is low 20s.
http://www.fuelly.com/car/pontiac/fiero

On fuelly compare average MPG of Fieros including I4 and V6 to MK1 AW11s and the smaller displacement 4A average much better MPG.

Again 200 lb ft is irrelevant till you apply RPM then you have power. Make that 200 lb ft at 500 RPM and you have a boat anchor.

Pulling strong just off idle has nothing to do with performance, response, or MPG. A turbo 4AGE should easily outperform this motor in every way. Aside from power made between idle and 2500 RPM which is an irrelevant measure when one of the motors spins to 7500 RPM stock.
This is where the turbo theory comes into play. A 1.6 liter turbo can make 3 liter power with 2 liter MPG.

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Re: 4A-GTE -- for fuel efficiency?

Postby jinx » Fri Jul 17, 2015 11:13 pm

Dude, I told u where to look for 3800 mpg..... but of course u would know more than they do..... and everyone else
This is where the turbo theory comes into play. A 1.6 liter turbo can make 3 liter power with 2 liter MPG.

You will only see 3 L performance in boost. You will NOT see 2 L mpg while in boost. Pull your head out of fantasy land!
Again 200 lb ft is irrelevant till you apply RPM then you have power. Make that 200 lb ft at 500 RPM and you have a boat anchor.

Its only irrelevant to anyone dumb enough to envision a 200 ft-lb tq @ 500rpm 3800 V6..... that excludes the "rest of us"
Pulling strong just off idle has nothing to do with performance, response, or MPG.

talking outta your rectum once again (lotsa practice I see). Makes ALL the difference in daily driver stop n go
I cut my teeth on buick V6s. Very 1st swap was a buick v6 4.1/5spd into a chevy vega.... then went onto buick grand nationals.
Just a slight tap on the throttle, scooted away. With the 2.56 monza rear end, it basically idled down the hwy sipping fuel.
No downshift to access a weak tq band, screaming a motor to 7500 rpm or "settleing" for a gutless pos 1.6 off boost. Fact
The later gen 3800 motors are significanly improved over the older 3.8/4.1
Any heathy GTS is garbage by comparison to my vega. Thats from experience owning both. I'm not asking you
You must be fully retarded if u think a 4age can hold a candle to swapped n.a, 3800 in the mpg/performance equation
.....but you believe in 1.0 L 7000 lb trucks, so no surprise there, in fantasy land

and just for fun. Crappy mileage and tire life - lol https://www.youtube.com/watch?v=yePPdPhr8XY

why do u think 3800 swaps r so popular ? ....from mini trucks, to old rwd rollas, to roadsters, to old rwd GM sedans, etc
Maybe u should suggest a 4AGE conversion instead. Would be just as stupid as your 1.0L 7000 pound dually concept

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Re: 4A-GTE -- for fuel efficiency?

Postby yoshimitsuspeed » Sat Jul 18, 2015 7:29 am

jinx wrote:Dude, I told u where to look for 3800 mpg..... but of course u would know more than they do..... and everyone else



I found good MPG numbers. And all of them fell within a nice little window of what I would expect. Anything that falls outside of that is either someone who has seriously modified their setup to try and do better or statistical anomalies.
I can find you people who have claimed 50 MPG on stock 16v 4AGEs. Does that mean I believe it's possible or claim that to be it's average capability?


jinx wrote:You will only see 3 L performance in boost. You will NOT see 2 L mpg while in boost. Pull your head out of fantasy land!


If you want to continue using offensive or personally attacking wording I have no problem deleting your posts. I don't mind a good debate but there is no reason to personally attack each other.
I can maintain stoich in closed loop at full boost. at 11:1 compression my BSFC is going to be pretty ridiculously good. Sure my MPG would be better off boost, making less power and driving or accelerating slower but it stays pretty damn high as long as I can stay in closed loop. More importantly performance and MPG are two separate conversations. Of course you aren't going to get your best MPG when you are WOT trying to get power. The point in the statement is that I can get my 1.6 liter gas mileage driving around all day long but when I want to pass that semi or just get on it a little bit I have a lot more power potential there with an overall very small negative impact on MPG.

jinx wrote:Its only irrelevant to anyone dumb enough to envision a 200 ft-lb tq @ 500rpm 3800 V6..... that excludes the "rest of us"


You just proved my point in that TQ is irrelevant unless it's associated to RPM. In which case you are talking about power.
Call using proper terminology dumb if you want but that just makes you look. Oh wait no personal attacks or name calling. Almost forgot.

jinx wrote:Makes ALL the difference in daily driver stop n go


That is 100% a matter of opinion and if making power at 1500 RPM is what's really important to you then the 4AGE in any form is the wrong motor. Doesn't mean it's less capable of doing the job. It just means you have personal expectations that can't be met by it.

jinx wrote:I cut my teeth on buick V6s. Very 1st swap was a buick v6 4.1/5spd into a chevy vega.... then went onto buick grand nationals.
Just a slight tap on the throttle, scooted away. With the 2.56 monza rear end, it basically idled down the hwy sipping fuel.
No downshift to access a weak tq band, screaming a motor to 7500 rpm or "settleing" for a gutless pos 1.6 off boost. Fact
The later gen 3800 motors are significanly improved over the older 3.8/4.1
Any heathy GTS is garbage by comparison to my vega. Thats from experience owning both. I'm not asking you
You must be fully retarded if u think a 4age can hold a candle to swapped n.a, 3800 in the mpg/performance equation
.....but you believe in 1.0 L 7000 lb trucks, so no surprise there, in fantasy land

and just for fun. Crappy mileage and tire life - lol https://www.youtube.com/watch?v=yePPdPhr8XY

why do u think 3800 swaps r so popular ? ....from mini trucks, to old rwd rollas, to roadsters, to old rwd GM sedans, etc
Maybe u should suggest a 4AGE conversion instead. Would be just as stupid as your 1.0L 7000 pound dually concept


I am not saying 3800 swaps shouldn't be popular. Just saying that your expectations are a little unrealistic.
As for the other stuff. Just because you don't understand the math and physics behind the theory doesn't mean you should attack me and call me dumb for trying to explain them.
Sorry to have so greatly offended you.

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Re: 4A-GTE -- for fuel efficiency?

Postby Respeckmejulie » Sat Jul 18, 2015 5:53 pm

my first hand experience:

bone stock zzw30 spyder, i never saw better than 28mpg on the highway. cruising speed 80-90mph (florida is crazy).

after building a turbo setup, using a/w for intercooling, and most importantly, a professional tune, i saw efficency on the highway jump to almost 40mpg, without altering my driving style.

could tuning alone have achieved this?
My toyota collection: ''82 KP61, '87 AW11

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