BT 4age dyno run 133.5 bhp at the flywheel :-(

[Stephen]

Lads,
I put my BT 20V on the rollers today for a power (or lack of!) run at a club track day.

I have a standard BT, standard ecu and open throttles using trumpets. I have 133.5 bhp at the flywheel which ain't good.

Max power was made at 7200 and was flat till 8300 where it dropped off.
The bloke doing the dyno run said she was too rich up high. At 5000 rpm it was 13.2 , at 6500 12.2 and at 7200 rpm it was 12.3.

Now I know the factory standard 165 is not seen very often but I am way off. I will check compression in each cylinder to see if there's an issue there. Engine has great oil pressure and uses no oil.

What are the likely reasons for my low power numbers? I will bring her out again on the rollers to see if there's any difference with changing the ignition timing but I can't see that making any difference to the air/fuel ratio. I also have a spare ecu I could try.

Or am I wasting my time and need to buy after market ecu?

[Deuce Cam]

How does it run overall? ANY mods, or is it 100% oem?

The 165 hp figure Toyota claimed is know for being exaggerated. I think most are actually planting around 145 hp.

Perhaps that dyno is just a heart breaker and low reading.

[yoshimitsuspeed]

By rollers I assume you mean chassis dyno. If so how did you determine your FWHP?

[Yosuke]

What kind of chassis dyno?

[Stephen]

Car is ae86 with transplanted BT 20v.

Yes, a chassis dyno. See here. These are the guys
http://www.westcoastperformance.ie/dyno.html

I suppose that my main point is this, the chap could see that the car was too rich in the high rev range. Is there anything I can do to address that?

One thing I've always noticed is that my temp gauge always shows about 1/3 up on the range. I also found that with the iscv connected that the revs would be too high and only after sitting (which meant temp would increase) for a few minutes would the gauge move towards half way and the revs drop.

So if the car is running cold wouldn't it stand to reason that she could be running rich because of that.

So next I've got to work out why we're not getting to optimum operating temp. The thermostat is probably a good place to start.

[Deuce Cam]

Any cel's?

What's the idle rpm when you say, "too high," and after also after it drops? It's normal for the idle to be higher on a cold start; the idle will drop when the engine gets up to operating temp - the iscv controls this function.

Definitely check the thermostat to make sure it's not stuck open/bad.

Running rich can be a bunch of things. Check ignition timing, o2 sensor, coolant temp. sensor, etc.

[yoshimitsuspeed]

Any cel's?

What's the idle rpm when you say, "too high," and after also after it drops? It's normal for the idle to be higher on a cold start; the idle will drop when the engine gets up to operating temp - the iscv controls this function.

Definitely check the thermostat to make sure it's not stuck open/bad.

Running rich can be a bunch of things. Check ignition timing, o2 sensor, coolant temp. sensor, etc.

O2 sensor is a good point. The ECU doesn't use the information of the O2 once you leave stoich so it's not directly involved in the range you are talking of. However in my experience with the GZE ECU as the ECU remaps the closed loop areas where it is listening to the O2 sensor it also has some effect on open loop areas of the map as well. If the O2 was reading lean the ECU would trim richer and would also remap richer. This remapping could cause it to run a little richer in open loop.

I don't believe it about the temp sensor as described above though I don't have personal experience with the BT ECU. At any rate you do want this system operating properly so if it's not reading right or if the thermostat is bad or something it should be fixed.
I have never believed the statement that changing timing should effect AFRs. This theory never made any sense. I just looked it up and although I can't find definitive facts this thread confirms my suspicions.
Sorry the thread is a bit crazy but sadly in a few minutes of searching, the closest thing I could find to actual information backed by some personal experience and some logical science.
http://www.iwsti.com/forums/ecu-tuning- ... afr-2.html
If you have information that suggests otherwise I would love to see it.
However again it is very important that your timing is set right so it should be checked and confirmed for other reasons.

[LongGrain]

if your car was on a chassis dyno, that HP figure was not measured at the flywheel.

133whp is pretty decent for a stock 20v..

[Stephen]

At the wheels the figure was 102. I asked the guy how the 133.5 number was determined. He said using some calculation within the dyno. So the 133.5 figure may in fact be optimistic, depending on what the transmission loses really are.
No CELs.
Re the idle, when I had the iscv connected it would idle after warmed up at 1200. If you left it idle for 4-5 minutes it would drop down to 850. Consistent with the water temperature rising to mid way on the gauge. But in normal driving you would seldom be at a standstill that long so I got a bit fed up of the high idle and blocked the iscv completely.
I had to bring the idle up with the throttle stop screw so now when cold she struggles a little but give it a minute or two things improve and she settles down to a steady 1000 rpm.
I really don't want the expense of going full aftermarket management. So I'm trying to explore what else I can do.
I notice my power curve is very gradual, there's no step up about 4000 that I'd expect with the vvt. I tested this when I got home by grounding it at idle and it worked, ie it bogged and nearly stalled. So can I be sure the other vvt is working?
Finally, if I did manage to get the upper end richness sorted, would I pick up 5, 10, 15 hp?

[yoshimitsuspeed]

You might gain a little but I doubt more than 5 or 10. I suspect something else is wrong. The fact that the VVT causes a bog is a good sign but it doesn't tell you that the whole circuit is functioning or that the ECU is triggering it. Ideally you would want to dyno it with and without as I posted above. For something like this even a dyno app or Gtech or something would likely be able to show you if it was functioning properly or not.

Most people think that VVT behaves like Vtec but it does not. VVT comes on early in the RPM and stays on till about 6500 or so and then turns off. The crossover points are supposed to be where the lines would crossover on the dyno. At that point it will make the same amount of power with the VVT on or off so you should not feel s significant change. Due to other variables there may be a slight change in power but probably not noticeable. You may be able to hear the VVT engage and disengage as the note does seem to change just a little.

[Deuce Cam]

I forgot to mention that not reaching operating temp. could also cause a rich condition as you mentioned.

Unfortunately I'm not familiar with the BT ecu. Aside from the ignition timing, most of my suggestions are based on the idea that the ecu could be stuck in some type of cold start enrichment mode for not reaching operating temp., or that it's in some type of limp/safe mode due to a bad sensor or malfunctioning component. Since you don't have any cel's it's probably not a bad sensor.

[oldeskewltoy]

At the wheels the figure was 102. I asked the guy how the 133.5 number was determined. He said using some calculation within the dyno. So the 133.5 figure may in fact be optimistic, depending on what the transmission loses really are.

102 @ the wheels isn't 133... it is far closer to 115-120 flywheel hp. Even as rich as you say.... mid to low 12s.... should still plan more power then 102.

Check the engines compression

[Stephen]

Yes I'll start with a leak down test. If that proves ok then I'll try another dyno session (well a proper session not just 1 power run).
I have a spare ecu we can try, we can also look to adjust the ignition timing. We can do a run with and without the vvt connected to determine if that is at fault.

I still think the engine running lower than ideal temp is not helping. We can take a look at the thermostat and see if that explains things there.
I'll report back folks on where this ends up. S

[Duy-]

a picture of the dyno sheet will say a lot, heres mine

t3 stacks
9 lbs flywheel
20v blacktop
for some reason the end gets cut off on my screen, just click view image to see the full picture

[Stephen]

I'll put a pic of my graph up tomorrow. It's similar to yours, quite smooth and progressive, just 20 or bhp less

Today the cylinder leak down test was completed and I have a very very healthy engine. Only 5-7 % difference between the cylinders and they all showed basically no pressure drop.

The mechanic continued to look at things and went to set the ign timing. He crossed T and E1. The CEL flashes but the ecu does not appear to move to diagnostic mode. i.e the timing stays about 16btdc. If we set it to 10 btdc now and temove the cross the timing stays at 10 btdc and it is retarded and feels that way to drive.

So would the ecu (I have 2 and they both do this) not entering this diagnostic mode be indicative of some other issue?

The other finding was that the CEL did at one stage throw an error for the THW while the mechanic worked on the car. This is odd as i checked for errors shortly after the rolling road and there were none. The sensor was checked for resistance and was good. A disconnect of the battery and a reconnect cleared the code.

Plan is to check thw ( water temp sensor) wiring.
Replace thermostat, the mechanic thinks it is opening too soon.
Also investigate rad cap. When squeezing the top rad hose when cold water is pushed out in to the expansion bottle. The mechanic says this should not be the case and should only happen when the system is hot and pressurised.

[Stephen]

Here's my graph, very similar to the earlier one that Duy has up till 6,000 rpm. After that mine fails to produce much more.

[Duy-]

well instantly you can see something went wrong at 5500 rpms, you stopped making power there. the 4age blacktop is a really rev happy engine but your dynograph looks almost like a smallport redtop. do you have an AFR read out to go with the dyno?

edit: nvm your afrs are right there lol

id like to say its because its running lean, do you have an aftermarket fuel pressure regulator installed? what is your current fuel pressure

[Stephen]

No aftermarket fuel pressure reg. Do you have the afr for your power run? The dyno operator said I was too rich up high.

[Duy-]

sorry i meant rich*, thought you might have had an aftermarket fpr and had it cranked up
i lost my afr sheet but it jumps around 13.5 and dips down to 12.8 near the end

[Stephen]

So the question is; given everything is standard what would make the engine too rich up high. I'm wondering re water and air temp sensors. I had the air temp sensor cable tied to my strut brace over at the intake side.
I've now moved that to the exhaust side. So it's going to read air temp warmer and may make things a bit leaner.

[yoshimitsuspeed]

Since this is a MAP motor something that effects VE will effect AFR.
Your VVT should switch off around 6k. If the VVT doesn't switch off it will cause a power dip due to a reduction in VE. That reduction in VE will also cause it to run richer and could cause more of a power dip. That's still where my money is since your graph looks decent right up to that point.
If not VVT then something else that effects VE. Timing belt a tooth off or something else.
Something like a clogged cat might even do it. Too much restriction that increases with volume of flow.

[Stephen]

Thanks for the replies folks.
I don't have a catalytic converter so that defo isn't to blame.
Re the vvt not turning off. How could I check that? I could get a led / bulb wired in. That would tell me when the ecu triggers the on and off but won't actually tell me if the vvt is reacting correctly. But you could be on to something as my vvt is noisey, and clicks especially when hot.
Re the timing belt, I can check that at tdc (a friend has a guage for checking this) the tits/marks on the cam pulleys are lined up correctly.

[yoshimitsuspeed]

Well since you want the VVT off above 6k or so you could just unplug it. If it idles normal you know it's disengaged and should remain so in the upper RPM.
Honestly the best thing would be to get it back on the dyno and do a run with the VVT unplugged and then one with it wired constant on. I belive the VVT should get constant power and be triggered through the ECU on the ground side. If this is the case you could just jumper the ground side straight to ground and that would lock the VVT on for the run.
If you don't want to get it on the dyno you could do the same with a dyno app. If you find your problem it should be visible on a half decent app or Gtech or something.

I should have my first rent a wideband unit built by next week or so. If you don't plan on doing ongoing tuning it may be a good option for a situation like yours.

[Stephen]

Cam timing checked, we used a dial gauge to confirm tdc and the cam pulleys lined up perfectly. That is the dimples in the pulleys with the marks on the head.
Vvt checked also, well I checked it operates at idle by grounding it and the engine really struggles and stalls. We then wired in a bulb and drove the car. At about 6000rpm the light goes off indicating that the ecu has turned off the vvt. The engine note changes but the car doesn't surge on like I believe it should. Could it possibly be the vvt pulley sticking in the on position? Even though the ecu is turning it off for some reason the pulley is staying on. My pulley does tick when it's hot but I reckoned it was still ok. Perhaps not.

I'll try driving with the vvt disconnected, I downloaded the dynolicious app so I'll try that out.
This has me bamboozled.

[yoshimitsuspeed]

Could it possibly be the vvt pulley sticking in the on position? Even though the ecu is turning it off for some reason the pulley is staying on.

I find it pretty unlikely but I would try a run with it unplugged just to eliminate the possibility. I don't know the internals of the VVT well enough but it has made me wonder if the centrifugal force could keep it from turning off if something was wrong.

Even if it's not the VVT I still suspect something is wrong beyond the AFRs. It might be a little rich but not enough to loose you that kind of power.

[Stephen]

Another opinion and I'll check it this weekend is that I'm not getting full throttle on all 4 itb's.

[Stephen]

I checked the throttle opening and I do have full throttle on all 4 ITBs. I also wired in a vvt LED so I can keep an eye on that. The ECU is definitelt turning on VVT and off again at about 7000 rpm. I did notice that vvt is activated only when you go for it, i.e floor it. It can come on a lot lower than 4,000 rpm and if you are just cruising at say 5,000 rpm it won't be on at all. I have a spare vvt pulley so I think I will try that as my own one if clicking a bit, especially when hot.

One thing I did discover is this, see pics. Basically my heater pipe (I am running a BT 20v in an AE86) is touching the knock sensor. I wonder is this a problem, i.e having it hard against the knock sensor. Another thing I checked involved removing the plug of the knock sensor and checking for error codes. Non showed which I though odd. So what do you reckon guys, is this bad. See pics.

[yoshimitsuspeed]

I
One thing I did discover is this, see pics. Basically my heater pipe (I am running a BT 20v in an AE86) is touching the knock sensor

I highly doubt that is any issue. Your knock sensor is designed to detect a very specific frequency and a very high frequency. I would suspect any vibration translated to the knock sensor through the rubber hose would be on a much different frequency than it was able to detect. Not only that but it's rubbing on the connector and any input would have a very minimal impact on the sensor it's self.
It doesn't seem ideal and for longevities sake I would try to fix it but I doubt that's the cause of your problem
That said it is only theoretical so from everything I know I guess it could be possible but I would say very very unlikely.