GT40 owners, please come inside

[ilumo]

Like the title says, if you have a GT40 on your car, with stock internals, I was wondering what kind of setup you have, and what tuning software you use? I am tuning with a DTEC right now, and I am trimming my 100% TPS from 3000 rpm+ to only 20%... does that sound about right? I have a return fuel setup at 40 psi idle, and 750cc RC injectors + 255lph walbro Fuel pump. I know I SHOULD have enough fuel to supply the turbo, which is set to 22 psi, BUT in my wideband, it says that Im sometimes at 14+ AFR!!! I dont know if thats possible, because I dont think I hear any knock, and the engine SOUNDS and runs pretty good. Could this be because im logging in 2nd + 3rd gear, or could this be a bad WBO2 sensor, or what? Any help would be appreciated. This is scaring me... Thanks guys!

[Screamin Demon]

Are you sure your wideband is calibrated correctly? That could be problem if it isnt. When is the last time you had it on a dyno?

[hozay09]

Keep this is on topic please! Stay in war stories if u can't control urselves.

[ilumo]

Are you sure your wideband is calibrated correctly? That could be problem if it isnt. When is the last time you had it on a dyno?

I havent had it on a dyno in a while... the last owner did.... The Wideband seems OK, because in closed loop operation, its staying around stoic... at around 14.4-14.7. So if that means its calibrated, then yea it is... hmmm... if that doesnt mean it is calibrated, then I dont know, I'll have to sit my butt on a dyno and find out...

[Screamin Demon]

I havent had it on a dyno in a while... the last owner did.... The Wideband seems OK, because in closed loop operation, its staying around stoic... at around 14.4-14.7. So if that means its calibrated, then yea it is... hmmm... if that doesnt mean it is calibrated, then I dont know, I'll have to sit my butt on a dyno and find out...

I would especially since it wasn't "your" car when the performance mods were done. Get on the dyno and make a baseline pass and check out their sniffer as opposed to your sniffer. Might be off that 1-2 digit, which may lead to a boom boom boom.:eek:

[ilumo]

yea, im going to check my O2 bung tonight... THe car SEEMS to be running good though. no strange noises, no bucking, the engine temp seems ok (no idea on egts though), and I ran it through 3rd gear last night passing my cousin, and he said he "smelt" a lot of gas, which means its semi rich no?

[Screamin Demon]

yea, im going to check my O2 bung tonight... THe car SEEMS to be running good though. no strange noises, no bucking, the engine temp seems ok (no idea on egts though), and I ran it through 3rd gear last night passing my cousin, and he said he "smelt" a lot of gas, which means its semi rich no?

Hows the back of the car lookin? Reason I ask is if there are alot of carbon (black sut) deposits on your trunk and rear bumper, than yes you are running rich. Just because you can smell gas, doesn't mean you are running rich, it could mean that there is alot of gas not being used in the combustion chamber. Best bet - get on the dyno and use their sniffer as a second opinion. Never good to mess around with boost and fuel if you are not sure.

[ptperformance]

bump the base pressure to 42 or 44 psi and then check your wideband readings.

[ilumo]

Ok, I can do that... Right now the pressure at idle is 40 psi, and without vacuum it goes to 50 psi... I can try increasing the idle pressure a little though.... then the readings should be a little richer, no?
As for my bumpers, no they arent black, but then again, my tipsstick out pretty far, ... the inside of the tips however, are pretty black and sooty..

THe strange thing is, SOME points when I do the log are pretty rich, like 10.9, but then the rpm point right after that would be 14.0 ... I guess I need to go on a dyno, and compare their sniffer to mine, to see if they are the same... gahhh... know any dynos around Danbury, CT?

[ptperformance]

Its an issue with the bigger injectors spattering instead of spraying. They need the pressure to make them work good on our cars. The pcm can adjust up to 66% at idle to keep the fuel trim at stoich, so you will be ok and will just have to adjust with SAFC or map clamp to keep it in the 11.5 range.

[ilumo]

Its an issue with the bigger injectors spattering instead of spraying. They need the pressure to make them work good on our cars. The pcm can adjust up to 66% at idle to keep the fuel trim at stoich, so you will be ok and will just have to adjust with SAFC or map clamp to keep it in the 11.5 range.

Really? Very interesting... stock fuel injectors run at what? 43.5 PSI? I MIGHT have to try this out... I am trying to find some dyno people near me so i can calibrate my WBO2 sensor... I don't know if its accurate or not... I really hope its NOT, or something else is faulty, because those high AFRs scare me, even though the car doesnt seem to be running any different.

[cokey]

eh quick question... right now my turbo's blown and i've got a small coolant leak.. before i would easily get 200+ miles to the tank.. now i'm getting a lot less.. i've got stg2 on there, any idea what could be causing it...? new 60-1 trim is gonna be in this coming week.. it should all be repaired by next week or the following..

[srtjay]

I am trying to find some dyno people near me so i can calibrate my WBO2 sensor...

I don't know you know this. but have you tried going to pruven performance. i don't know that much about them, but i've heard dsm, evo and wrx guys going there

[ptperformance]

Really? Very interesting... stock fuel injectors run at what? 43.5 PSI? I MIGHT have to try this out... I am trying to find some dyno people near me so i can calibrate my WBO2 sensor... I don't know if its accurate or not... I really hope its NOT, or something else is faulty, because those high AFRs scare me, even though the car doesnt seem to be running any different.
I think they run at 58 psi ( i have to check again). Hit the dyno but make sure you bump the fuel pressure as a quick check, setting it 50 psi and then driving around a little wouldnt hurt to see if the gauge strarts to show richer AFR's.

[ilumo]

ok.... well, I went to the dyno on monday... and I guess everything is fine. I'm running pretty rich uptop..

RPM HP TQ AFR BOOST
2800 102.2 191.7 11.8 5.2
2850 106.5 196.3 11.8 5.6
2900 110.8 200.6 11.8 5.8
2950 115.3 205.2 11.8 6.2
3000 119.8 209.7 11.8 6.5
3050 124.4 214.3 11.8 7
3100 129.5 219.4 11.7 7.5
3150 135 225 11.7 8.1
3200 140.2 230.1 11.6 8.7
3250 144.9 234.1 11.6 9.2
3300 149.9 238.6 11.5 9.7
3350 155.4 243.6 11.5 10.2
3400 160.4 247.8 11.5 10.9
3450 165.2 251.5 11.4 11.7
3500 170.1 255.3 11.4 12.5
3550 176.6 261.3 11.4 13.4
3600 184 268.4 11.4 14.2
3650 190.8 274.5 11.4 15.1
3700 198 281 11.4 15.8
3750 205.4 287.7 11.4 16.4
3800 211.9 292.9 11.4 16.8
3850 217.5 296.7 11.4 17.4
3900 223.3 300.7 11.4 17.8
3950 228.7 304.1 11.3 18.2
4000 233.2 306.1 11.2 18.3
4050 237.2 307.6 11.2 18.3
4100 241.9 309.9 11.1 18.2
4150 247.7 313.5 11.1 18.2
4200 253.1 316.5 11 18.3
4250 257.1 317.8 11 18.3
4300 261.1 319 11 18.4
4350 265.9 321 10.9 18.5
4400 272.4 325.2 10.9 18.6
4450 277.3 327.3 10.9 18.7
4500 281.9 329 10.9 18.8
4550 287.5 331.9 10.8 18.9
4600 294 335.7 10.8 19
4650 299.9 338.7 10.8 19.1
4700 304.6 340.4 10.8 19
4750 309.1 341.8 10.8 19.1
4800 314.1 343.6 10.8 19.5
4850 317.7 344 10.7 19.8
4900 320.9 344 10.7 20.2
4950 325.8 345.7 10.7 20.5
5000 331.1 347.8 10.7 20.4
5050 335.3 348.7 10.7 20.1
5100 339.8 349.9 10.7 20.1
5150 343.6 350.4 10.7 20.2
5200 346.4 349.9 10.7 20.4
5250 348.7 348.9 10.8 20.5
5300 352 348.8 10.8 20.5
5350 355.2 348.7 10.8 20.4
5400 358.9 349.1 10.8 20.4
5450 361.2 348.1 10.8 20.5
5500 362.8 346.5 10.8 20.6
5550 363.9 344.3 10.8 20.5
5600 364.7 342 10.8 20.4
5650 365.4 339.6 10.8 20.4
5700 366 337.3 10.8 20.3
5750 366.4 334.7 10.7 20.3
5800 364.7 330.3 10.7 20.6
5850 360.8 323.9 10.6 21.3
5900 357.5 318.2 10.4 21.6
5950 355.6 313.9 10.3 21.4
6000 354 309.9 10.2 21.1
6050 351.6 305.3 10.1 20.8
6100 350.7 301.9 10.1 20.7


So I guess the numbers look OK for my amount of boost (20 psi), and my rich tune. I guess my problem was that my 2nd + 3rd gear runs might have been too fast of runs for my DTEC to handle (sample rate too small). One problem though... my fuel pressure was going down at the higher rpms. Could that be from the stock fuel line being too restrictive? or my walbro pump isnt keeping up? hmm.. also seems like my boost is coming in REALLY slow... i wonder why. I thought these GT40s were supposed to hit max boost at 3900-4000... doesnt look like it here... hmm..

[SPECJ]

eh quick question... right now my turbo's blown and i've got a small coolant leak.. before i would easily get 200+ miles to the tank.. now i'm getting a lot less.. i've got stg2 on there, any idea what could be causing it...? new 60-1 trim is gonna be in this coming week.. it should all be repaired by next week or the following..

If you are is running like crap and the PCM knows this, then it just dumps fuel in a a fail safe and there goes your great MPG. Also coolant leaks tend to raise coolant temps which will tell the PCM to do a whole bunch of crazy things to try to get them down... and dump fuel.

[SPECJ]

ok.... well, I went to the dyno on monday... and I guess everything is fine. I'm running pretty rich uptop..
RPM HP TQ AFR BOOST
2800 102.2 191.7 11.8 5.2
2850 106.5 196.3 11.8 5.6
2900 110.8 200.6 11.8 5.8
2950 115.3 205.2 11.8 6.2
3000 119.8 209.7 11.8 6.5
3050 124.4 214.3 11.8 7
3100 129.5 219.4 11.7 7.5
3150 135 225 11.7 8.1
3200 140.2 230.1 11.6 8.7
3250 144.9 234.1 11.6 9.2
3300 149.9 238.6 11.5 9.7
3350 155.4 243.6 11.5 10.2
3400 160.4 247.8 11.5 10.9
3450 165.2 251.5 11.4 11.7
3500 170.1 255.3 11.4 12.5
3550 176.6 261.3 11.4 13.4
3600 184 268.4 11.4 14.2
3650 190.8 274.5 11.4 15.1
3700 198 281 11.4 15.8
3750 205.4 287.7 11.4 16.4
3800 211.9 292.9 11.4 16.8
3850 217.5 296.7 11.4 17.4
3900 223.3 300.7 11.4 17.8
3950 228.7 304.1 11.3 18.2
4000 233.2 306.1 11.2 18.3
4050 237.2 307.6 11.2 18.3
4100 241.9 309.9 11.1 18.2
4150 247.7 313.5 11.1 18.2
4200 253.1 316.5 11 18.3
4250 257.1 317.8 11 18.3
4300 261.1 319 11 18.4
4350 265.9 321 10.9 18.5
4400 272.4 325.2 10.9 18.6
4450 277.3 327.3 10.9 18.7
4500 281.9 329 10.9 18.8
4550 287.5 331.9 10.8 18.9
4600 294 335.7 10.8 19
4650 299.9 338.7 10.8 19.1
4700 304.6 340.4 10.8 19
4750 309.1 341.8 10.8 19.1
4800 314.1 343.6 10.8 19.5
4850 317.7 344 10.7 19.8
4900 320.9 344 10.7 20.2
4950 325.8 345.7 10.7 20.5
5000 331.1 347.8 10.7 20.4
5050 335.3 348.7 10.7 20.1
5100 339.8 349.9 10.7 20.1
5150 343.6 350.4 10.7 20.2
5200 346.4 349.9 10.7 20.4
5250 348.7 348.9 10.8 20.5
5300 352 348.8 10.8 20.5
5350 355.2 348.7 10.8 20.4
5400 358.9 349.1 10.8 20.4
5450 361.2 348.1 10.8 20.5
5500 362.8 346.5 10.8 20.6
5550 363.9 344.3 10.8 20.5
5600 364.7 342 10.8 20.4
5650 365.4 339.6 10.8 20.4
5700 366 337.3 10.8 20.3
5750 366.4 334.7 10.7 20.3
5800 364.7 330.3 10.7 20.6
5850 360.8 323.9 10.6 21.3
5900 357.5 318.2 10.4 21.6
5950 355.6 313.9 10.3 21.4
6000 354 309.9 10.2 21.1
6050 351.6 305.3 10.1 20.8
6100 350.7 301.9 10.1 20.7
So I guess the numbers look OK for my amount of boost (20 psi), and my rich tune. I guess my problem was that my 2nd + 3rd gear runs might have been too fast of runs for my DTEC to handle (sample rate too small). One problem though... my fuel pressure was going down at the higher rpms. Could that be from the stock fuel line being too restrictive? or my walbro pump isnt keeping up? hmm.. also seems like my boost is coming in REALLY slow... i wonder why. I thought these GT40s were supposed to hit max boost at 3900-4000... doesnt look like it here... hmm..

Ok, maybe i only see this as a problem, but your hitting full boost at 5000 RPMS!!!! You def need to get that mofo tuned. Having too rich of an A/F before you come to full boost actually slows things down. Get those A/F's somewhere around 11.5's after 3950 and you will probably hit full boost at 4500 (unless you only have one spring in the WGA, which if you do :::SMACK:::) Get 11.5's across the board and I see 475-480whp on pump.

[ilumo]

yeaa.. the thing is... before 4000, my AFR are in the 11.5 area. I can retune this myself, but the thing is... I don't know what the EGTs are when I get into the higher Rpms 4500+, so right now im just tapering the fuel down to mid tens there. Now wouldnt 11.5 AFR at 6500 rpm be way too lean? I just dont want to pop a piston ring with detonation... better safe than sorry, because I dont have an extra engine!
What about the fuel pressure problem? thanks!

[SPECJ]

yeaa.. the thing is... before 4000, my AFR are in the 11.5 area. I can retune this myself, but the thing is... I don't know what the EGTs are when I get into the higher Rpms 4500+, so right now im just tapering the fuel down to mid tens there. Now wouldnt 11.5 AFR at 6500 rpm be way too lean? I just dont want to pop a piston ring with detonation... better safe than sorry, because I dont have an extra engine!
What about the fuel pressure problem? thanks!

Your not on a stock turbo. EGT's arent an issue on bigger turbo's because you dont have the bottleneck in the manifold. You shouldnt have EGT issues unless you are running really lean 12.5+. You'll still will have to worry about breaking pistion's if your on a stock bottom end with making too much power. I would really suggest you look into atleast some new pistions.

[ilumo]

what is the weakpoint in these engines then? If I don't run into too much detonation, then what kinda power levels can I look at "safely", and if I DO run into the occasional knocking, how much can these guys take before crapping the bed, and what is the cause going to be? I can actually just up the boost a little, and that should lean up the AFR a little bit , as well as give me some more power. I still do not like the SLOW spoolup time though. Thats crazy...
maybe I'll lean the top up a little bit.. maybe to 11.2-4

[kevinwarren240]

ok, this is how i tune my gt40 right around 4k rpm's lean the afr's to around 13.5: and go from 4-4200 that way then get right into 11.5:1 afr and that gets me the spool up at around 42-4300! i ran 28psi on stock internals and that netted me 493hp. just as of late i got a some detonation and my #1 piston let go, i blame it on bad gas so just be carefull and you can make 500hp all day on race fuel. i ran 20psi on pump all day and that nettet a 12.7@106 at the track!

[cokey]

what is the weakpoint in these engines then? If I don't run into too much detonation, then what kinda power levels can I look at "safely", and if I DO run into the occasional knocking, how much can these guys take before crapping the bed, and what is the cause going to be? I can actually just up the boost a little, and that should lean up the AFR a little bit , as well as give me some more power. I still do not like the SLOW spoolup time though. Thats crazy...
maybe I'll lean the top up a little bit.. maybe to 11.2-4


anyone..?

[N2MB]

are you running a turbonetics wastegate and an mbc?lets put things in perspective though..your running a very big turbo so you will absolutely spool late.however you should spool up around 3800 rpm.if you have the single spring in the w/g then i would swap it out for the double spring.there really are alot of variables that could cause the late spool beyond the tune.you could possibly have a boost leak that is bleeding the boost off as your trying to spool up.
you definately need to lean it out.personally i would tune for anywhere between an 11.5-11.8 afr.that will yield best results and keep you away from detonation.
no kind of detonation is good period!!when you run crazy setups its hard to avoid but i would NEVER tune it above a 12.5 afr ANYWHERE in boost.to answer your question about the weak points of the motor,the first would be the balance shaft which should be removed.its there to absorb crank vibrations and is not made to handle the torque that it is put under on big hp cars.oil pump failure i would say would be the next best culprit in terms of catastrophic trends.when you tune it it is always safer to run on the rich side to keep from melting your pistons but if you should lean it out and go beyond 12.5 + on the afr's then your most likely failure point would be burning holes in the pistons.it is harder to do on a big turbo but by no means is it impossible.
i would spend a good amount of time checking over for boost leaks and if you havent shimmed the wastegate i would do so,you could be just pushing the boost past the wastegate.you might even hear it slightly when boosting up.you shouldnt hear anything from the dump tube until you aproach full spool