Tuning for race gas with different stoich value
10-14-2014, 02:15 PM
#1
Tuning for race gas with different stoich value
Hey guys,
I will be running VP MS109 in my car. This is a highly oxygenated race fuel with a stoich value of 13.4:1. The car is set up for pump gas now and the stoich scalar in the tune is set up for 14.64:1.
To add the necessary fueling for VP MS109, do I just change the stoich scalar in the tune, or is there more to it?
This is a boosted setup and I'm commanding .80 lambda in my PE tables so I would like to maintain .80 lambda on the race fuel (13.4:1 x.80 = 10.7:1 AFR).
Thanks. --Neil
I will be running VP MS109 in my car. This is a highly oxygenated race fuel with a stoich value of 13.4:1. The car is set up for pump gas now and the stoich scalar in the tune is set up for 14.64:1.
To add the necessary fueling for VP MS109, do I just change the stoich scalar in the tune, or is there more to it?
This is a boosted setup and I'm commanding .80 lambda in my PE tables so I would like to maintain .80 lambda on the race fuel (13.4:1 x.80 = 10.7:1 AFR).
Thanks. --Neil
10-15-2014, 03:09 PM
#2
I would think that the O2 sensors will see the effect of the different fuel and drive your fuel trims in the positive direction. Once the new fuel trims have been learned the PCM will add 25% fuel in PE per your .8 lambda settings, assuming you have the needed extra fuel injector/pump capacity.
The main issue I see is how the engine reacts during the learning phase. You may want to pre-tweak your MAF calibration by 9-10% corresponding to 14.64/13.4 such that your fuel trims will not be off by much when you put in the different fuel.
The main issue I see is how the engine reacts during the learning phase. You may want to pre-tweak your MAF calibration by 9-10% corresponding to 14.64/13.4 such that your fuel trims will not be off by much when you put in the different fuel.
10-15-2014, 11:39 PM
#4
I won't have time to learn the fuel trims. I'm having trouble sourcing the fuel I need this week in Tampa. I will probably need to pre-order fuel at the Texas Mile, tweak the stoich values in the tune, and then it's go-time.
10-15-2014, 11:42 PM
#5
There's no MAF. I'm running a 2-bar SD tune.
10-17-2014, 12:24 AM
#7
10-19-2014, 01:45 AM
#8
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St. Jude Donor '13-'14-'15
Not quite sure if simply changing the Stoih value in your tune will do it---The stock narrowband 02's have a very small operating window of accuracy--generally they are only accurate from around .400 and .500 millivolts---( 14.68 is .450 millivolts )
You may have to incorporate the use of wideband 02's which are accurate everywhere
If you are going to drive on the street with the 109 oxy fuel you may have to do more research But if you are only going to use it on track days--then you can forget about all the P/T tuning and simply richen up your WOT AFR in the power enrichment tables--- as well as you main VE table Are you still using your front 02's ??
You may have to incorporate the use of wideband 02's which are accurate everywhere
If you are going to drive on the street with the 109 oxy fuel you may have to do more research But if you are only going to use it on track days--then you can forget about all the P/T tuning and simply richen up your WOT AFR in the power enrichment tables--- as well as you main VE table Are you still using your front 02's ??
10-19-2014, 02:46 PM
#9
Burning Brakes
Not quite sure if simply changing the Stoih value in your tune will do it---The stock narrowband 02's have a very small operating window of accuracy--generally they are only accurate from around .400 and .500 millivolts---( 14.68 is .450 millivolts )
You may have to incorporate the use of wideband 02's which are accurate everywhere
If you are going to drive on the street with the 109 oxy fuel you may have to do more research But if you are only going to use it on track days--then you can forget about all the P/T tuning and simply richen up your WOT AFR in the power enrichment tables--- as well as you main VE table Are you still using your front 02's ??
You may have to incorporate the use of wideband 02's which are accurate everywhere
If you are going to drive on the street with the 109 oxy fuel you may have to do more research But if you are only going to use it on track days--then you can forget about all the P/T tuning and simply richen up your WOT AFR in the power enrichment tables--- as well as you main VE table Are you still using your front 02's ??
If running mixes of fuels then enriched PE maybe easier, but I think the OP is using 1 fuel type and having 2 correct tunes is best IMO.
10-20-2014, 02:42 PM
#10
NB and WB only read O2 which doesn't change with fuel. Stoich table just tells the PCM how much fuel to add per air to meet the AFR setpoints.
If running mixes of fuels then enriched PE maybe easier, but I think the OP is using 1 fuel type and having 2 correct tunes is best IMO.
If running mixes of fuels then enriched PE maybe easier, but I think the OP is using 1 fuel type and having 2 correct tunes is best IMO.
10-20-2014, 11:30 PM
#11
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St. Jude Donor '13-'14-'15
I agree with both points. O2 sensors don't really care what fuel you are using and what it's stoich value is as they are looking for a certain density of O2 in the exhaust which matches what should be seen at stoich. And trying to run both fuels on one tune is probably going to work even less well then GM's trying to have one tune running both straight gasoline and E85.
It's almost similar as running a car on E85 which has a Stoich of about 10.25--However with a car that can use multi Stoich fuels GM rather than have wideband 02's to set the AFR accomplishes the change by using built in multipliers as an adder to the 100% gas table-- In a stock Flex Fuel eng the 02's are still trying to achieve 14.68 but the stock tune is what deviates from that value to match the actual fuel in the tank--- Same goes for the timing adder in the tune---Its done with a multiplier to the gas timing table based on the % of ethonal
In the OP's case where the Stoich deviation is from Oxy gas ---- not by the use of ethonal -- the stock tune's multiplier system won't work
But you are stll missing my point about narrowbands---You can't simply change the Stoich value in the tune and ask for 13.4 because
" The stock 02's" are only centered and set to operate in a very narrow operating range " That's why they are called "NARROWBAND 02's " !!!! ...... and 13.4 is out of that range !!!
10-21-2014, 01:29 AM
#12
The 02's may not care BUT your engine does !!!!!---If you are running a fuel that has a stoich of 13.4---You better have your P/T fueling always trying the achieve that ratio----
It's almost similar as running a car on E85 which has a Stoich of about 10.25--However with a car that can use multi Stoich fuels GM rather than have wideband 02's to set the AFR accomplishes the change by using built in multipliers as an adder to the 100% gas table-- In a stock Flex Fuel eng the 02's are still trying to achieve 14.68 but the stock tune is what deviates from that value to match the actual fuel in the tank--- Same goes for the timing adder in the tune---Its done with a multiplier to the gas timing table based on the % of ethonal
In the OP's case where the Stoich deviation is from Oxy gas ---- not by the use of ethonal -- the stock tune's multiplier system won't work
But you are stll missing my point about narrowbands---You can't simply change the Stoich value in the tune and ask for 13.4 because
" The stock 02's" are only centered and set to operate in a very narrow operating range " That's why they are called "NARROWBAND 02's " !!!! ...... and 13.4 is out of that range !!!
It's almost similar as running a car on E85 which has a Stoich of about 10.25--However with a car that can use multi Stoich fuels GM rather than have wideband 02's to set the AFR accomplishes the change by using built in multipliers as an adder to the 100% gas table-- In a stock Flex Fuel eng the 02's are still trying to achieve 14.68 but the stock tune is what deviates from that value to match the actual fuel in the tank--- Same goes for the timing adder in the tune---Its done with a multiplier to the gas timing table based on the % of ethonal
In the OP's case where the Stoich deviation is from Oxy gas ---- not by the use of ethonal -- the stock tune's multiplier system won't work
But you are stll missing my point about narrowbands---You can't simply change the Stoich value in the tune and ask for 13.4 because
" The stock 02's" are only centered and set to operate in a very narrow operating range " That's why they are called "NARROWBAND 02's " !!!! ...... and 13.4 is out of that range !!!
Even your wideband that displays afr on the display is reading lambda at the sensor, then using the multiplier for pump gas to spit out 14.7 on the display. In the case of a wideband which displays afr, 14.7 is stoich for all fuels because it just multiplies lamda*14.7, which is why I personally prefer to have my wideband display lambda. If you put in e85 or some other gas, the afr reading on the wideband will be very misleading.
Since OP is running a 2 bar SD in closed loop, he can change the stoich scalar in his tuning software to get the results he is looking for. Just check to make sure that your fuel trims are close to 0 with your new stoich scalar before getting on it- that way you can be confident that your stoich scalar, ve table, and all the appropriate fuel multipliers are in line. Then you can tailor your power enrichment or boost enrichment multipliers and timing.
Also, whether or not you run LTFTs will need to be considered. I think that most turn them off. I really don't remember under what conditions, but some LTFTs will add on top of whatever WOT multipliers you already have.
Last edited by LTstewy8; 10-21-2014 at 01:34 AM.
10-21-2014, 07:55 AM
#13
No, you are missing the point on how narrowbands operate, which Joshboody and enoniam already pointed out. It will help if you think in terms of lambda, or its inverse equivalence ratio, since that's what your pcm thinks in. A stock narrowband will read 450 mV as 1 lambda (NOT necessarily 14.68 afr). So whatever fuel you put in, the o2 sensors will adjust the trims to get you to 1 lambda=stoich, ragardless of whether your fuel in the tank has a stoich afr of 20, 14.7, 10, or 3.
Even your wideband that displays afr on the display is reading lambda at the sensor, then using the multiplier for pump gas to spit out 14.7 on the display. In the case of a wideband which displays afr, 14.7 is stoich for all fuels because it just multiplies lamda*14.7, which is why I personally prefer to have my wideband display lambda. If you put in e85 or some other gas, the afr reading on the wideband will be very misleading.
Since OP is running a 2 bar SD in closed loop, he can change the stoich scalar in his tuning software to get the results he is looking for. Just check to make sure that your fuel trims are close to 0 with your new stoich scalar before getting on it- that way you can be confident that your stoich scalar, ve table, and all the appropriate fuel multipliers are in line. Then you can tailor your power enrichment or boost enrichment multipliers and timing.
Also, whether or not you run LTFTs will need to be considered. I think that most turn them off. I really don't remember under what conditions, but some LTFTs will add on top of whatever WOT multipliers you already have.
Even your wideband that displays afr on the display is reading lambda at the sensor, then using the multiplier for pump gas to spit out 14.7 on the display. In the case of a wideband which displays afr, 14.7 is stoich for all fuels because it just multiplies lamda*14.7, which is why I personally prefer to have my wideband display lambda. If you put in e85 or some other gas, the afr reading on the wideband will be very misleading.
Since OP is running a 2 bar SD in closed loop, he can change the stoich scalar in his tuning software to get the results he is looking for. Just check to make sure that your fuel trims are close to 0 with your new stoich scalar before getting on it- that way you can be confident that your stoich scalar, ve table, and all the appropriate fuel multipliers are in line. Then you can tailor your power enrichment or boost enrichment multipliers and timing.
Also, whether or not you run LTFTs will need to be considered. I think that most turn them off. I really don't remember under what conditions, but some LTFTs will add on top of whatever WOT multipliers you already have.
Regarding the LTFTs, the stock PCM will use zero for them when going into Power Enrichment (WOT or close to it) if they were negative, but use them as they are if they are positive. So basically go a little richer if they were running negative and unchanged if they were positive.
I personally don't think it is a good idea to turn them off. They were turned off in my car when I bought it in May. Did a scan and found that my short term fuel trims were running around +25. They go to zero in Power Enrichment which meant my car was going VERY LEAN at WOT. Obviously if one is periodically scanning to make sure that situation isn't happening or keeping tabs on things with a wideband that's less of an issue but my car didn't have a wideband on it and it sure didn't look like anyone was keeping tabs on what was happening at WOT, not to mention going a bit lean at each fuel trim cell transition.
10-27-2014, 11:49 PM
#14
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St. Jude Donor '13-'14-'15
No, you are missing the point on how narrowbands operate, which Joshboody and enoniam already pointed out. It will help if you think in terms of lambda, or its inverse equivalence ratio, since that's what your pcm thinks in. A stock narrowband will read 450 mV as 1 lambda (NOT necessarily 14.68 afr). So whatever fuel you put in, the o2 sensors will adjust the trims to get you to 1 lambda=stoich, ragardless of whether your fuel in the tank has a stoich afr of 20, 14.7, 10, or 3.
Whether use use Lambda EQ ratio or AFR --it's all the same-- Only different terminology ---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
Whether use use Lambda EQ ratio or AFR --it's all the same-- Only different terminology ---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
10-28-2014, 12:15 PM
#15
No, you are missing the point on how narrowbands operate, which Joshboody and enoniam already pointed out. It will help if you think in terms of lambda, or its inverse equivalence ratio, since that's what your pcm thinks in. A stock narrowband will read 450 mV as 1 lambda (NOT necessarily 14.68 afr). So whatever fuel you put in, the o2 sensors will adjust the trims to get you to 1 lambda=stoich, ragardless of whether your fuel in the tank has a stoich afr of 20, 14.7, 10, or 3.
Whether use use Lambda EQ ratio or AFR --it's all the same-- Only different terminology ---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
Whether use use Lambda EQ ratio or AFR --it's all the same-- Only different terminology ---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
10-29-2014, 05:42 PM
#16
Burning Brakes
Whether use use Lambda EQ ratio or AFR --it's all the same-- Only different terminology ---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
Just clarifying in case there's a misunderstanding.
11-02-2014, 02:15 AM
#17
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St. Jude Donor '13-'14-'15
No not a mis -understanding at all-- You are not understanding my post--or believe what I'm trying to tell you---I've explained many times the difference between a narrowband 02 which can only center at .450 millivolts and a wideband that can center anywhere-----If you want to change your lambda to 13.4 and call it good----Then good luck to you--have at it--- 13.4 is approx. .850 millivolts--There is no way a stock narrowband 02 will make LTFT corrections based on a P/T AFR of 13.4 your engine will become LEAN and melt plugs-pistons valves or rings--Not to mention it will ping like crazy being so lean-----I'm done !!
11-02-2014, 10:53 AM
#18
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---Just the here in the US we use AFR----14.68 IS 1.0 lambda---How can it not be--It is always with gas !! which has a Stoich of 14.68 and on a narrowband or a wideband---My point is that stock naroowbands are not accurate very far from 14.68 or 1.0 lambda---That is why they are called naroowbands--
The OP can do whatever he likes--But if he thinks he is gonnna use a fuel with a low Stoich as he has planned---the engine will be horribly lean !!! the 02's will only try to always achieve 14.68--ALWAYS----P/T
Without getting combatant, your statement above tblu92 is just not correct in my understanding. 14.68 is not the constant for Lambda 1.0.....in the US or anywhere. The stoich value of a "perfect burn" is Lambda 1.0 and is representative of the amount of oxygen the O2 sensor reads in the exhaust. Those numbers of oxygen molecules will be the same for Gas, E10, E85 or straight ethanol and will result in the narrowband O2 sensor in outputting around the 450 mv level you stated. But it will do that for any percentage of alcohol fuel uses. The more or less the oxygen molecules, the more or less the O2 sensors voltage will deviate. The term narrowband just means that is is only accurate in a narrow window above and below the stoich target. Based on the PCM's job, that is all that is needed in closed loop operation. The PCM integrates the O2 sensor voltage and increase/decrease fueling in an attempt to maintain the 450 mv level. That is where the trims will come in and adjust themselves accordingly. Now, the trims do have a limit (app 25%) and if the fuel you are using creates this situation than yes you will lean out and cause big damage. As a note, going from Pump Gas to E85 would put you dangerously at this +/- 25% limit. To this you need to tune your MAF and VE values to increase the fueling back to a nominal level and all will be good with the world again.
As further protection, if the PCM see's that the trims are showing a lean condition, it will automatically add this percentage of fuel to your PE fueling to protect the motor.
Hope this helps and again I in no way want to cause any issues, just stating the facts.
Thanks,
Ed M
11-02-2014, 12:14 PM
#19
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Wow, some seriously wrong information here... Lambda is NOT 1.0 = 14.6xxxx AFR
That is the point of using lambda of 1 is it IS the stoich value of ANY fuel. The 14.6 is nothing more than a scalar value for regular pump gas....
lambda is calculated as LAMBDA = AFR OBSERVED / AFR OF FUEL STOICH
So IT DOES NOT MATTER WHAT YOUR FUEL IS... If stoich is 9:1 for your fuel then lambda 1 is when your afr is 9:1 NOT 0.6
This is why AFR must be specified when you refer to a lambda measurement.
The narrowband sensor can be used for lambda 1 of ANY FUEL. It will figure that out and trim it accordingly. HOWEVER, your VE tables etc. still require knowing what stoich is as its used as a scalar value in fueling.
Dont believe it? Put E85 in a car tuned for regular gas.... Your trims will go super positive trying to enrichen the fueling in closed loop. You didn't tell the car the new fuel was in did you? No, the trims are trying to bring fueling back to lambda 1. For e85 ~9.8:1 instead of 14.6:1.... Otherwise the car would not change fueling at all when you put the new gas in..
THE CRITICAL FORMULA FOR MESSING WITH YOUR STOICH IS
lambda = afr/afr stoich
change your stoich value with hptuners... check your tune with wideband to be sure, as there is always some error involved when we change VE and MAF tables due to transitory fueling. Adjust your power enrichment accordingly, afr/afr stoich.
That is the point of using lambda of 1 is it IS the stoich value of ANY fuel. The 14.6 is nothing more than a scalar value for regular pump gas....
lambda is calculated as LAMBDA = AFR OBSERVED / AFR OF FUEL STOICH
So IT DOES NOT MATTER WHAT YOUR FUEL IS... If stoich is 9:1 for your fuel then lambda 1 is when your afr is 9:1 NOT 0.6
This is why AFR must be specified when you refer to a lambda measurement.
The narrowband sensor can be used for lambda 1 of ANY FUEL. It will figure that out and trim it accordingly. HOWEVER, your VE tables etc. still require knowing what stoich is as its used as a scalar value in fueling.
Dont believe it? Put E85 in a car tuned for regular gas.... Your trims will go super positive trying to enrichen the fueling in closed loop. You didn't tell the car the new fuel was in did you? No, the trims are trying to bring fueling back to lambda 1. For e85 ~9.8:1 instead of 14.6:1.... Otherwise the car would not change fueling at all when you put the new gas in..
THE CRITICAL FORMULA FOR MESSING WITH YOUR STOICH IS
lambda = afr/afr stoich
change your stoich value with hptuners... check your tune with wideband to be sure, as there is always some error involved when we change VE and MAF tables due to transitory fueling. Adjust your power enrichment accordingly, afr/afr stoich.
11-03-2014, 06:03 PM
#20
Burning Brakes
Actually I think what tblu is referring to is tuning <1.0 lambda using NB… wording is just confusing. You can tune non-1.0 setpoints without a WB though, although its not easy. Basically once you dial in your trims, you have a bunch of flexibility and can use the NB to make sure you’re on the correct side of lambda… actually NBs can read variations of lambda, BUT you need to have an initial reference point like a WB (so would kinda defeat the purpose). But WB isn’t necessary if you get creative… for example taking NB voltages at various AFR setpoints in the OL table (with a close to 0 trim tune). Once you have a baseline you can use at WOT. Anyway all this is unnecessary when you can just use a WB.
I was thinking about this for an E85 tune targeting lean P/T setpoints, but it could be a hassle with weather changes… although so far cooler air hasn’t effected my trims much at all. In theory it should not, but I’ve read that LSx trims do change with weather.
I was thinking about this for an E85 tune targeting lean P/T setpoints, but it could be a hassle with weather changes… although so far cooler air hasn’t effected my trims much at all. In theory it should not, but I’ve read that LSx trims do change with weather.
Last edited by Joshboody; 11-03-2014 at 06:07 PM.