A/F Ratio for ZR-1
09-26-2016, 02:19 PM
#1
Heel & Toe
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A/F Ratio for ZR-1
I have a 2010 ZR-1, bone stock. I understand "blown" engines are set rich to avoid a over lean condition. When I floor the throttle I smell a rich/gun powder odor (maybe it's too rich). As 12.9:1 A/F @ WOT is the sweet spot for most engines, I was wondering if you know what the OEM/Factory setting is (A/F @ WOT) for the LS9. I'm planning on running it on a dyno and this info. would be good to know before hand.
Last edited by dan69bbk; 09-26-2016 at 02:20 PM. Reason: spelling
09-26-2016, 04:11 PM
#2
Safety Car
I have a 2010 ZR-1, bone stock. I understand "blown" engines are set rich to avoid a over lean condition. When I floor the throttle I smell a rich/gun powder odor (maybe it's too rich). As 12.9:1 A/F @ WOT is the sweet spot for most engines, I was wondering if you know what the OEM/Factory setting is (A/F @ WOT) for the LS9. I'm planning on running it on a dyno and this info. would be good to know before hand.
How many miles? Any codes for catalytic converter?
Gun powder/Sulphur smell could just be the cats heating up at WOT. The ECM will dump more fuel to cool them off, thus further rich condition.
Let us know how the dyno session goes.
Last edited by Mike's LS3; 09-26-2016 at 04:16 PM.
09-27-2016, 11:00 AM
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St. Jude Donor '15
Looks like 1.397 from 5500 RPM's and up on a stock ZR1 tune, so ~0.716 lambda or 10.5:1 if you're basing it off of 14.7:1 being stoich.
(commanded that is--I can only assume actual would be close to that on a stock car)
In other words--pretty dang rich. You could lean it out a bit for sure.
It's also commanding leaner at lower RPM's.
(commanded that is--I can only assume actual would be close to that on a stock car)
In other words--pretty dang rich. You could lean it out a bit for sure.
It's also commanding leaner at lower RPM's.
Last edited by schpenxel; 09-27-2016 at 11:01 AM.
09-30-2016, 03:32 PM
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Boosted engines are around 11.0 to 11.3:1 A/F ratio @WOT. It depends on the tune and how the engine responds. I wouldn't be surprised if the stock ZR1 A/F at WOT dips in the high 10's at times.
How many miles? Any codes for catalytic converter?
Gun powder/Sulphur smell could just be the cats heating up at WOT. The ECM will dump more fuel to cool them off, thus further rich condition.
Let us know how the dyno session goes.
How many miles? Any codes for catalytic converter?
Gun powder/Sulphur smell could just be the cats heating up at WOT. The ECM will dump more fuel to cool them off, thus further rich condition.
Let us know how the dyno session goes.
10-01-2016, 03:50 PM
#6
Just remember that fuel is cooling, and the TVS-2300 loves to turn into a heat pump quickly since the water intercooler is not the best of design to cool the compressed air back down.
So you can play with the A/F to go leaner, but also keep a close eye on the air intake temps as well, since the added fuel is also being used to cool the air back down in the cylinders.
Truth is, by going to a meth kit, you solving two problems as the same time. The mist will keep the air intake temps down so your not having to run so fat on the A/F ratio during boost for it cooling properties, and the added meth is your safety factor to allow a timing push as well.
So you can play with the A/F to go leaner, but also keep a close eye on the air intake temps as well, since the added fuel is also being used to cool the air back down in the cylinders.
Truth is, by going to a meth kit, you solving two problems as the same time. The mist will keep the air intake temps down so your not having to run so fat on the A/F ratio during boost for it cooling properties, and the added meth is your safety factor to allow a timing push as well.
10-02-2016, 08:46 AM
#9
Le Mans Master
too. Not an expert here, but since setting up my WB on a stock 09 LS3, 11.8 is richest I've seen at WOT under several different temps.
10-07-2016, 05:11 PM
#10
Racer
12.9 is aggressive for a lower power normally aspirated tune. As power levels (and compression ratio) rises more fuel is used as a safety margin and to help cool the intake charge. I don't know the LS3 well but agree that it should never be anywhere in the 10's and even high 11's is rich. Whether 12.9 is good for a tuned A/F or not I'll leave to the LS3 experts. Also, wide band sensors clipped on the back of the exhaust will easily read 0.5-1 point richer than if installed before the cats where the gas is hottest and more accurate. All these numbers are assuming a front mounted wide band reading.
A stock ZR1 will be high 10's at lower RPMs and fattens up to mid 10's at high RPMs. I've owned 2 ZR1s and both curves looked identical the the coolant temps were kept in check. I played with a prototype intake on one of them and lost 30-40HP because it fattened up into the low 10's which would require tuning to fix. Even with the stock intake, leaning out the mix to 11-11.4 or so can yield maybe 30HP with no other changes, but there is increased risk of cat failure. The LS9 pushed so much air at 638HP that fuel is regularly used to cool them down. If you tune it, add boost, or are always in the throttle the cats can fail prematurely. My current ZR1 is stock with just a cat back and my cats failed with under 20k miles.
A stock ZR1 will be high 10's at lower RPMs and fattens up to mid 10's at high RPMs. I've owned 2 ZR1s and both curves looked identical the the coolant temps were kept in check. I played with a prototype intake on one of them and lost 30-40HP because it fattened up into the low 10's which would require tuning to fix. Even with the stock intake, leaning out the mix to 11-11.4 or so can yield maybe 30HP with no other changes, but there is increased risk of cat failure. The LS9 pushed so much air at 638HP that fuel is regularly used to cool them down. If you tune it, add boost, or are always in the throttle the cats can fail prematurely. My current ZR1 is stock with just a cat back and my cats failed with under 20k miles.
10-08-2016, 04:33 PM
#12
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Had it on the dyno today just to get a base line; didn't sniff it. The
#s were poor at best--495 hp/465 torque. Again didn't sniff it but boy did it smell rich. Being an "old-school" guy and believing that no matter how sophisticated an engine is,
3 things will always affect tune: spark, fuel and compression. So I decide to pull a plug. the gap was at .070!!!! (should be .040) WTF. I pull another... that's at .030!!!. This plug had some soot around the base whereas the wider gapped plug did not... wonder if that's what's causing the rich smell and affecting the power??? Can't be good for power.
#s were poor at best--495 hp/465 torque. Again didn't sniff it but boy did it smell rich. Being an "old-school" guy and believing that no matter how sophisticated an engine is,
3 things will always affect tune: spark, fuel and compression. So I decide to pull a plug. the gap was at .070!!!! (should be .040) WTF. I pull another... that's at .030!!!. This plug had some soot around the base whereas the wider gapped plug did not... wonder if that's what's causing the rich smell and affecting the power??? Can't be good for power.
10-08-2016, 05:58 PM
#13
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St. Jude Donor '15
Missing the iridium "puck" off of the plug perhaps? It's not unheard of
10-09-2016, 02:09 AM
#14
Le Mans Master
I have had problems with the Copper plugs gap opening significantly after a few thousand miles. I have also had the iridium tip missing on one plug from the original factory plugs. I prefer the iridiums bc the gap stays more fixed over time.
10-12-2016, 07:43 AM
#15
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Maybe someone can advise on this. I would like to get this thing tuned (the ZR-1 in question) as dyno #s are less than stellar. However, a tech told me that the car is always operating within the factory parameters, i.e., fuel enrichment because the computer is constantly re-learning. If so, as in my case, why does the car smell "pig rich" on the dyno and putting down low #s??
10-12-2016, 08:16 AM
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St. Jude Donor '15
Because the tech is an idiot.
The O2 sensors GM uses can't read AFR @ WOT. They're only used at part throttle.
If it's having to add fuel at part throttle (i.e. fuel trims are positive) then it can carry those positive values into WOT, making it run richer
However, the same is not true for negative fuel trim values. If they're negative prior to going WOT then extra fuel is not subtracted.
Regardless, once at WOT it's in open loop, O2 sensors aren't used, and the ECM really has no idea what the AFR actually is, and it has no real way to correct for it being wrong at that point.
Thus the purpose of tuning.
The O2 sensors GM uses can't read AFR @ WOT. They're only used at part throttle.
If it's having to add fuel at part throttle (i.e. fuel trims are positive) then it can carry those positive values into WOT, making it run richer
However, the same is not true for negative fuel trim values. If they're negative prior to going WOT then extra fuel is not subtracted.
Regardless, once at WOT it's in open loop, O2 sensors aren't used, and the ECM really has no idea what the AFR actually is, and it has no real way to correct for it being wrong at that point.
Thus the purpose of tuning.
Last edited by schpenxel; 10-12-2016 at 08:16 AM.
10-12-2016, 05:07 PM
#18
Le Mans Master
Because the tech is an idiot.
The O2 sensors GM uses can't read AFR @ WOT. They're only used at part throttle.
If it's having to add fuel at part throttle (i.e. fuel trims are positive) then it can carry those positive values into WOT, making it run richer
However, the same is not true for negative fuel trim values. If they're negative prior to going WOT then extra fuel is not subtracted.
Regardless, once at WOT it's in open loop, O2 sensors aren't used, and the ECM really has no idea what the AFR actually is, and it has no real way to correct for it being wrong at that point.
Thus the purpose of tuning.
The O2 sensors GM uses can't read AFR @ WOT. They're only used at part throttle.
If it's having to add fuel at part throttle (i.e. fuel trims are positive) then it can carry those positive values into WOT, making it run richer
However, the same is not true for negative fuel trim values. If they're negative prior to going WOT then extra fuel is not subtracted.
Regardless, once at WOT it's in open loop, O2 sensors aren't used, and the ECM really has no idea what the AFR actually is, and it has no real way to correct for it being wrong at that point.
Thus the purpose of tuning.
10-15-2016, 09:17 PM
#20
Le Mans Master
Quite possible. What are the gaps on the one's missing tips? Like .090+??