4A-GZE supercharged - more power options for Lemons!

[slow_poke]

Hi,

we just finished a Lemon's race and our '88 SC felt a little tired. Turns out running ~100psi compression. Data logger calculated 89WHP. The previous race we were calculated ~120WHP which i take to be a pretty solid GZE.

I'd like some advice as to what to change that would get us a bit more than just a refresh that i think would get us back to the 120WHP range - i'd love to see a endurance race reliable 140-150WHP. of course i'd love more but from reading that sounds like it gets increasingly difficult.

Since we'll be pulling the head to go after at least the valves, we'll have a chance to go after some other things as well: here's my thinking as to what's cheap and effective:

- bigger TB - multiple people have said that the SC TB is small and an NA or MKII is bigger and almost a drop in

- installing NA cams - don't want to spend money on 'real' cams, but heard that NA cams are better than SC. is that true? NA cams can be had for almost free... (like that!)

- JDM SC - 120mm pulley vs. 125mm pulley, gets us a bit more boost at expense of higher SC rpm. worry about reliability and this will cost some money but am contemplating springing for it as it seems like biggest bang for the buck.

- better intercooler / better IC cooling - this we can do, since its lemon's we can likely get different one, move it into air flow, etc. etc.

- SC --> IC --> engine piping - again, this is something we can hacktastically do whatever we need to make better. thinking larger DIA and less bends as much as possible.

that's it for a first cut. remember, we're running the stock ECU and fuel system.

Things that we probably wouldn't do: (or i'd have to be convinced...)

- Headers - i've heard that headers don't help until you're making >200hp which we'll likely never make. also these seem to cost real money, and w/o the shielding likely heat up our engine compartment. thoughts?

- bigger crank pulley - this will overdrive the waterpump which i've heard is a really bad idea (cavitation when >8k rpm) cooling is a big issue for endurance racing... so don't think we'd consider this which is why to get more boost i think we'd have to go the JDM SC above.

- Megasquirt, etc... - these again cost money, are really not that Lemony and i'm nervous of the tuning effort...

- V6 swap - some of guys are advocating that but my hope is the above can get us to the 140-150whp which would put us near to a v6 w/o all the fab work... that's why i'm asking for advice! i'm hoping 'hotted up' SC == v6

Thanks in advance for all your help. we already love balance of the MR2 and now we want to give the thing a little push so we can do some passing in the straights as well!

[yoshimitsuspeed]

It sounds like you are on a budget so first I'll put out what I would consider to be an optimized moderately high budget idea and then I'll try to address some of your questions on more of a tight budget strategy.

The biggest problem with Superchargers and especially these old roots blowers is that they don't like high pressure ratios. Anything you can do to keep the pressure lower and airflow higher the happier it will be.
After driving my GZE on the stock motor and SC, then converting to turbo and then converting to a blacktop running on the GZE ECU I can tell you that high compression, bigger cams and increased VE is almost a magical combination to work with the limitations of the GZE ECU.
Now in stock form anything much over 10 PSI leads to low end leanout. People have run like this with surprising success but in an endurance motor running lean would be the last thing you would want. On the bright side it ends at 3500 RPM so maybe the motor would not see RPM below that to be an issue. People relate the leanout cap to around 10 PSI but it's more about volumetric airflow maxing out the AFM cap so this has to be factored in.
With that said, if I were in your shoes and had money to blow on a good rebuild with proper parts I would go with 11:1 compression and some bigger cams. Probably in the 256 to 264 range. The great thing about compression is that it makes more power per unit of air entering the motor. This means more power under the low end leanout cap. Cams move the VE curve up so even though they allow more air to enter the motor at higher RPM it should actually help stave off the low end leanout a bit. The one thing I can tell you is that my BT turbo running 7 PSI is about a second faster 0-60 than my 16v GZE longblock was at 12 PSI on the same turbo. This kind of puts into perspective how much there is to be had with an optimized setup.
Going with some high comp pistons and aftermarket cams would seriously turn your world around. If that is out of the budget here are my other thoughts.


Run the thinnest headgasket you can. This will increase your compression and reduce your squish gap.
Nominally a .7mm HG would be about as thin as you would want to run but in my experience they seemed to make the deck sit a little on the high side.
Going off factory numbers the 4A pistons should sit at zero deck but all the motors I have seen they sit a little below. So to really optimize the setup you could measure the piston deck and aim for about .7 to .8mm squish gap.
Closer than that and you could risk kissing the head at full temp and RPM.

As for cams, you have to be careful. It's not GZE vs NA. Some time between 87 and 88 they went to the lower profile cam. An 88 NA will have the same cams as a GZE or smallport. So you will want to make sure you get early 4A cams. You will also want to measure to make sure. I am confident that Toyota did a lot of mixing and matching in this era and did things like install x cam until they ran out before switching to the next rev.
Normally I tell people not to waste their time with this mod. I have watched a couple people try it with no notable increase and I have even seen people try to measure or quantify the difference by inspecting the cams with trouble. I do not believe it's enough gain to generally be worth the time but if you have some or can easily find some and are already in there it couldn't hurt.

As for the induction system everything before the SC is definitely the place to focus the most effort. Being fixed displacement restrictions after the supercharger have much less effect since it will try to move the same amount of air no matter what. Of course a big restriction would make the SC work harder and waste more energy but small restrictions are small concerns.
Before the SC however is vital. A pressure drop before the SC is multiplied by the pressure ratio of the SC so if you are running a 2:1 PR at sea level you should be making 14.7 PSIG boost or more importantly 29.4 PSIA.
Now if you have a 1 PSI pressure drop before the SC you have an inlet pressure of 13.7 PSIA and now an outlet pressure of 27.4 PSIA or 12.7 PSIG.
The worst part is that since the pressure ratio is the same your inlet temps will be the same. The advantage is that if you can get rid of that 1 PSI pressure drop you gain 2 PSI boost without any increase in outlet temps.
Once again, probably outside your budget but I believe I have found a 72mm throttlebody that could be made to work without too much trouble. It would need an adapter made which I could do and have wanted to do but I haven't found anyone who wants it bad enough and I haven't been able to make it a priority to take on as a side project.

If you are concerned with overspinning the water pump then a smallport pulley actually wouldn't be the worst idea.
I have been thinking about making a water pump pulley that moved it to the outer belt to alleviate this problem. If you would be interested in this let me know.
This would actually underdrive the WP significantly compared to running on the big inner pulley.

A better intercooler could benefit but most people don't recognize how. As I said earlier being a fixed displacement pump a bigger intercooler won't allow any more air into the motor. It will however mean cooler air which equals a lower pressure ratio which also means even cooler air. The SC doesn't have to work as hard and at least as importantly you can run more compression and timing so even though the volume of air entering the motor is roughly the same you should be able to get more from those cooler temps.

[slow_poke]

Thanks for the quick reply!

let's see:
a) love the idea of a turbo, higher compression, better cams, but just don't want to put in the money.

b) i like the idea of thin HG. i'll look around and see what we can find. when we bring the head in for a valve job maybe we could deck it the tiniest bit as well?

c) cams; that's what i remember, early, '85 cams would be the best. if i can find a set on one of the forums we can add it to the mix. we'll measure as well before we install... if it can't hurt and might help, we'll have the head off so we can add it to the mix.

d) intake. nice. i remember you mentioning this before. we'll work on this alot. seems like free power. someone gave me a TB when i bought a rear sway bar from them so i'll go and try and figure out which one it is...

e) IC: i get the positive displacement thing and also the temp thing so it seems like if we can keep it cooler we still win here as well

f) waterpump / small port pulley. sounds like i need to do some research here. Smallport crank pulley is smaller than larger port? i thought the crank pulley was same for both and only thing that changed was the JDM SC pulley (120 vs. 125). hmmmm interesting idea of moving waterpump to outer pulley. i'll have to look at the engine.

the GZE gen2 was 165 hp but had 8.9:1 compression and the smallport head. what's your gestalt as to resultant whp for this sort of thing?

[oldeskewltoy]

Thanks for the quick reply!

let's see:


b) i like the idea of thin HG. i'll look around and see what we can find. when we bring the head in for a valve job maybe we could deck it the tiniest bit as well?

c) cams; that's what i remember, early, '85 cams would be the best. if i can find a set on one of the forums we can add it to the mix. we'll measure as well before we install... if it can't hurt and might help, we'll have the head off so we can add it to the mix.

Stock 4AG head can be cut as much as 1.25mm (.050") That is approaching the absolute maximum. Cutting the head that much will drop your chamber volume down to about 33cc (stock is 36cc). With that much of a cut you will need adjustable timing pulleys.


As far as the valve job... these are the known TRD angles...





As far as cams are concerned the difference is 6 degrees of duration, 4/10mm of lift.



The difference in lift(4/10mm) isn't as much as you might think.... this is because the stock 4AG ports tend to go "flat" @ about 7mm of lift. This is "seen" better by looking @ the airflow through the 4AG head.



The small arrows (red and blue) are the stock cams lifts plotted - red = 88+, while blue = 87 and earlier You can see that both the stock intake and exhaust ports go flat @ about 7mm of lift.

the GZE gen2 was 165 hp but had 8.9:1 compression and the smallport head. what's your gestalt as to resultant whp for this sort of thing?

In an AW11... about 145 whp

[yoshimitsuspeed]

Thanks for the quick reply!

let's see:
a) love the idea of a turbo, higher compression, better cams, but just don't want to put in the money.

b) i like the idea of thin HG. i'll look around and see what we can find. when we bring the head in for a valve job maybe we could deck it the tiniest bit as well?

c) cams; that's what i remember, early, '85 cams would be the best. if i can find a set on one of the forums we can add it to the mix. we'll measure as well before we install... if it can't hurt and might help, we'll have the head off so we can add it to the mix.

d) intake. nice. i remember you mentioning this before. we'll work on this alot. seems like free power. someone gave me a TB when i bought a rear sway bar from them so i'll go and try and figure out which one it is...

e) IC: i get the positive displacement thing and also the temp thing so it seems like if we can keep it cooler we still win here as well

f) waterpump / small port pulley. sounds like i need to do some research here. Smallport crank pulley is smaller than larger port? i thought the crank pulley was same for both and only thing that changed was the JDM SC pulley (120 vs. 125). hmmmm interesting idea of moving waterpump to outer pulley. i'll have to look at the engine.

I meant smallport supercharger pulley. People call it the JDM version but this is inaccurate because both the largeport GZE and smallport GZE were offered in Japan. The smallport was not offered in the US so people refer to it as the JDM JZE but it's completely inaccurate. The smallport GZE had a smaller clutched pulley on the supercharger making about 10 PSI instead of 8.

[slow_poke]

Wow, great info!!! Two questions, do you know, off hand, the cam pulley DIA, and (noobish question) if we grind the valve seats are we going to need to replace the valves?

[oldeskewltoy]

Wow, great info!!! Two questions, do you know, off hand, the cam pulley DIA, and (noobish question) if we grind the valve seats are we going to need to replace the valves?

Not sure why you want cam pulley diameter... 107.6mm is the outer diameter

You don't NEED to replace the valves unless your machinist says you do.... When you grind (I prefer "cut") the seats you should also grind/cut the valve so you have 2 clean cut surfaces that will mate together. If when cutting your valves, there is not enough material, your machinist will tell you - typically, 4AGE valves have enough material allowing them to be cut

[slow_poke]

would all these changes going to make the engine run lean? my understanding is the SC ECU can handle the JDM SC (10psi), what about the cams and the cleaned up intake (TB?). my guess is at WOT ( determined by TPS, AFM maxed?) the ECU delivers a set amount of fuel and if i'm able to flow more air it'll go lean. if so, what's the fix? remember, this is a race car, so car about 4-7krpm the most. adjustable FPR and just get close?

i'm also guessing head decking has no affect.

btw, a local shop said $650 for head decking / valve job... that sound about right? i was hoping for less... i guess competency costs....

[yoshimitsuspeed]

The leanout condition is only below 3500 RPM. For some reason Toyota put a cap in the ECU on the AFM signal below this. If the AFM opens more than that the ECU will not recognize or compensate for more air going into the engine.
If the cams increased VE below 3500 then they could cause it to get slightly closer to the lean condition. Anything much over a 256 though should really slightly drop the VE below 4500 and increase it above. In this case it should actually move you slightly further away from the low end leanout.
Either way the effects here will be minimal with the fixed displacement SC since it will really be controlling how much air is going into the engine. They will make a bigger difference in the upper RPM where the SC is more taxed. The cams should lower the boost pressure, lowering temps and improving the SC efficiency. This should lead to notable gains especially if you are going to add compression and timing.

Opening up and reducing restriction before the SC should increase the volume of air passing the AFM so it's a valid concern but on the bright side the low end leanout is only in the lower RPMS where the pressure drop and therefore volumetric flow difference will be much less than it will be in the upper RPM.

I don't suspect these mods would have a huge effect on how much boost you could run or how much air you could flow before getting low end leanout but I would strongly recommend getting a wideband before doing these mods so you can monitor their effects. Doing them without it will be somewhat of a gamble.

[saiGone]

Isn't there a $500 limit for Lemons?

[slow_poke]

what?? excuse me? ) this is all theoretical of course. i would never, NEVER do anything that would jeopardize our car's lack of reliability NOR its ability to place in the bottom 25% of lap times... i've got my standards!

more seriously, we found an '88SC about a year and a half ago for $650. terrible. but engine was surprisingly strong and tranny/ clutch were good. sell some parts, cage and all that jazz later and we were running pretty well at the 2013 T-hill race, right up until the engine fire.... now racing costs money... even a 'small' engine fire hurts... rebuilt harness, all new hoses, a couple sensors and it started right up... w/ 120psi compression... grrrr... ok, found a donor car where the P.O. had beached it on a median (front suspension basically toast), and dropped in the working engine... again, around ~120psi. raced that and w/ a slight overheat due to a hose the resultant compression on Engine#2 was ~100psi (89whp calculated)... so here we are. spare engine on the bench, dreaming of being burly, mostly spent engine in car.

as an aside, the Lemon's guys gave us a residual value of $19 after the fire. this meant we had $481 to spend fixing the car. so subtract the hoses,harness,sensors (all in <$100) and we've got some $300 to still be within the rules... they generally give you a pass on 'spare motors' because they don't want to discourage you too much... remember $500 typically gets you a REALLY crappy car.

what are the choices? V6 swap? that's not free, 20V? that's not free... freeing up intake is basically free, new cams, basically free... valve job, required... decking head is ~$50 once its at the shop. adjustable cam gears.... ok, that's money; is there a cheaper way?? JDM SC, o.k. got me there. that's pure cheatery... busted...

again, this is PURELY theoretical at this point... i've just been 'thinking' impure thoughts... don't tell Jay.

Yosh / Oldeskewl, your help has been VERY VERY helpful!! can't thank you enough. was thinking if we started to do this we probably want to invest in a wideband. (saiGone - instrumentation is not tracked in Lemons...)

[oldeskewltoy]

I believe you can get Fidanza cam pulleys for $100 for the pair... but I haven't checked in years. You might find a set of used cam pulleys.....

I'd begin with the busted engine... get it stripped and clean and find out what is, and isn't toast.


Head decking? You mean machining the heads surface... as I pointed out above - a 1.25mm cut will lower chamber volume to about 33cc. Lowering the chamber volume from 36cc to 33cc will raise compression to about 8.6 to 1 (from 8.1 to 1) Since you are likely going to use a stock headgasket, I would also deck/cut the blocks mating surface about .012". This will improve the engines squish, providing for a better burn, and more power.

[slow_poke]

pulling the trigger on the JDM SC, the cams. but what about the BOV / bypass? i read somewhere in passing last night that it goes off at 8psi. is there a JDM one, or can i just disconnect? i remember reading other threads saying it can be bypassed? grrrr... the research never ends...

[yoshimitsuspeed]

For a road going car I would not recommend removing the ABV as it should help greatly with cruising and off boost efficiency.
For a pure track car though it should be okay. With the clutched pulley the biggest advantage of the ABV is that the air has a route around the SC when it's disengaged. This should reduce parasitic loss and improve fuel efficiency while cruising.
You can also look up the GZE ABV mod that modifies it to stay closed under higher boost.

[saiGone]

Mandatory pics of next Lemons, and we wont say anything! lol

[slow_poke]

i'm not going to do anything to incriminate myself but if one was to search "angry hamster racing" they might find an MR2 that 'may' be representative...

lost the super-fab teammate that did most of the work on the z600 and we wanted a car that was more reliable. so far that's true, but we're nowhere, i mean NOWHERE near as fast, but we're working it on the MR2...

another race in DEC at Sonoma, we expect all this work to be done by then and so we'll have a chance to see how it all works out... if they have a dyno on-site at the race (they have in the past), i'll get the thing dyno'd so we'll know where it ended up...

[slow_poke]

Here's what we did:

a) valve job (to TRD shape above)
b) skim head
c) skim block
d) install '85 NA cams
e) JDM SC
f) thinnest MLS gasket we can get

- we think this will get us ~8.6:1 compression ratio (if you want the gory details, i'll do a followup. i'd love someone to check my work)
- we also calculated a 0.5deg cam timing change so ignored it. if we do this again, we'll machine more (see notes above) and that'll get us ~1.0 degree so we'll measure and modify one of our spare cam gears.
- haven't had time to clean up intake / intercooler piping.

Put it all together, started fine, cylinder pressure is: 110,140,140,140 cold. DOH! so Cyl #1 is still down. we had thought the only issues were in the head. Note to self, next time if you've doing an engine, do the whole thing!! So, we'll hit the track day tomorrow and see if we can get a data acq calculated wheel hp that we can compare against previous engines. Was going to do a dyno pull but going to wait until we can get a clean engine build.

btw, shout out to Bruce at Best Machine in San Rafael. did the machining work, looks good and gave us Lemon's a GREAT price for the work!

unless the installed engine explodes or turns out to be crap, we'll do the Lemon's race on this engine and if its not TOO wimpy we'll probably clean up intake / intercooler and go after handling for a bit prior to going back to the engine work... then take our spare engine and hone those cylinders and swap everything over some time in the summer...

[slow_poke]

Ok, so the results...

Sonoma is a great place to race.... technical track, close to the bay area, all that.

Rain stopped Saturday morning about an hour before race start. they cycled us under yellow until 10min after the planned start time and there were 4-5 folks off in the mud just under yellow. The line was SLICK. and we had completely new tires so that also hurt. After ~40min of feeling like I was driving on ice things started to dry out. car had good pickup, better than before. The one thing i noticed was that the power band moved up range; on the stock SC cams the car ran out of steam at 6500rpm, but now pushed on until 7500, and in fact i saw that it would start to pull away from people a bit after 6500... never saw that before.

anyway, car ran great for Driver #1, #2, #3, about 5.5 hrs or so, everyone generally very happy. Then driver #4 got in, turned one lap, heard a knocking. called it in, said he was going to baby it around and then come in. By the time he got to the S's on the back side the engine blew. Per standard engine blow, huge cloud of smoke and then you're coasting... As he was pulling off the track said he saw flames so off into the mud, and a mad dash to the wall... In retrospect, no evidence of fire, but there was a one foot section of the exhaust that was 'curiously' devoid of ANY oil and had a light dusting of surface rust... hmmm....Anyway, while he was calling it in he had the wherewithal to check gauges and good oil pressure and water temp.

That was it for the race...

Upon teardown, looks like piston stuck in the block, wrist pin pulled from piston and that and con rod punched hole in block. con rod could still spin on the crank, and no bluing on that end. Current theory is plugged oil channel that starved the wrist pin which consequently seized and that was that... probably a plugged oil line... Grrrr.... maybe some junk in an oil line, or the oil cooler from the original fire??? maybe from when we machined the block w/ the pistons still in it???

Oh, and insult to injury, no data acquisition data to tell us how the thing actually ran. AND, my other teammate lost the memory chip so no go-pro video of going 3 wide thru 2 or other misc driving heroics!!! double grrrr.....

so... what next... take a deep breath, realized we've done THREE engines in THREE races... and likely slow down w/ the rebuild of engine #2 which is sitting in the garage... likely next race would be June Buttonwillow or August T-hill.

[yoshimitsuspeed]

Post started out awesome then went sad.

That does suck it blew up.
I would love to see pics of the damage, especially the rod, piston and related failure areas. It sounds like a bit of an unusual failure.
Did the piston come out easily?
For the wristpin to pull free there would have had to have been a ton of force on it. I would find it much more likely the piston seized in the bore.

[slow_poke]

Yeah, event order is important. I'm thinking wrist pin seized, cocking piston which seized, and THEN the whole thing pulled apart. Is there another way the piston gets stuck in the bore? I don't have that much experience in this space

[oldeskewltoy]

Upon teardown, looks like piston stuck in the block, wrist pin pulled from piston and that and con rod punched hole in block. con rod could still spin on the crank, and no bluing on that end.

Which piston?? I'm gonna guess #1.

[yoshimitsuspeed]

Yeah, event order is important. I'm thinking wrist pin seized, cocking piston which seized, and THEN the whole thing pulled apart. Is there another way the piston gets stuck in the bore? I don't have that much experience in this space

If the piston expanded too much and or started to gall it could have seized on it's own. That should be pretty obvious with a good smear of piston on the cylinder walls.

[slow_poke]

#3. We expected number one

[sirdeuce]

An option for more boost is to turn the SC pulley down. I know someone out there does it. I know BigMike had his turned down. I still have that 165mm pulley I offered you. But Mikey turned his pulley down to somewhere around 111 or 112 mm. Might find it somewhere here, look towards the last pages. [urlhttp://bigmike.marlincrawler.com/forum/index.php?topic=87.0][/url] .

[yoshimitsuspeed]

Personally and most especially on a race car with an SC12 I would try to keep the boost as low as possible and try to make power with cams and compression at least if that is an option.
I would definitely try to stay under 12 PSI as that is Oguras max rating and the top of their maps. Even there the efficiency does not look good. It's also the longer pulls and higher duty cycle you will see on a track that will really get too hot and potentially damage the SC or at least wear it out much faster.

[aaron_1234]

Hi oldeskewltoy, could you explain why the stock port flow 'goes flat' at over 7mm lift? Is it the valve size or the stock ports or the head design? I have a big port running 288/10mm tomei procams and when I rebuilt it I stuck with standard size valves ( supertech) and silvertop throttles because I figured more air velocity would help driveability but now I'm wondering if I should have gone OS and larger cams because it is very easy to drive. I didn't touch the combustion chambers and just took the casting flaws off the ports but reshaped the bowl slightly and where the valve seats were machined. Also tapered valve guides. At the moment I have the rev limiter set at 9k and power doesn't fall off.

[chi-town]

I always mix up which sc is which but isn't the previa sc just a tad larger?

[yoshimitsuspeed]

I always mix up which sc is which but isn't the previa sc just a tad larger?

The GZE is SC12 the Previa is the SC14 which is larger but that doesn't automatically mean better.
Both have the same factory recommended max pressure ratio of 1.8:1. At sea level that's about 12 PSI boost. Even at that 12 PSI boost both have horrid adiabatic efficiencies and at that pressure the SC14 isn't much better than the SC12.
If you wanted to move 12 PSI on a stockish 1.6 liter motor the SC14 doesn't really give you any advantage. if you wanted to run 12 PSI on a 2 liter motor or an 11k RPM 1.6 the SC14 would be a better choice but if you are going to run 16 PSI on a 4AGE it's so far outside the SC14s design parameters it's not worth the effort it would take to swap it. Sure it may do the job a tiny bit better than the SC12 but it's still very much the wrong tool for the job.

[oldeskewltoy]

Hi oldeskewltoy, could you explain why the stock port flow 'goes flat' at over 7mm lift? Is it the valve size or the stock ports or the head design? I have a big port running 288/10mm tomei procams and when I rebuilt it I stuck with standard size valves ( supertech) and silvertop throttles because I figured more air velocity would help driveability but now I'm wondering if I should have gone OS and larger cams because it is very easy to drive. I didn't touch the combustion chambers and just took the casting flaws off the ports but reshaped the bowl slightly and where the valve seats were machined. Also tapered valve guides. At the moment I have the rev limiter set at 9k and power doesn't fall off.

On the intake side.... port shape, size, quality of casting. bowl shape, as well as bowl to seat placement. On the exhaust side... the port is poorly shaped, as well as bowl shape, bowl to seat, casting quality, and surface finish

[chi-town]

I understand they both have the same max pressure but the volume of air at the max psi is greater with the 14 than the 12.