i was wondering what lambda should i be aiming for with E10 or E85 fuels. i read somewhere that for E100 the stioch is 1Lambda and 9.0AFR, and max power ratio is 0.71/6.42 and its confusing me a little.

my question is if i am using a LC1 setup for gasoline AFRs (14.7 stoich). then what AFR values should i aim for to get max power (eqv to 12.5AFR gas or 11.5AFR) in the following fuels

1) E10
2) E85


thankx

EDIT: what i am getting confused is Lambda for gassoline=0.8503 and E100=0.714 then E85 lambda should be (0.8503*0.15 + 0.714x0.85)=0.7344 but it is supposed to be 0.7143.... maybe i am getting confused and going in circles so i ask the above question.

 

Thats the beauty of Lambda, its the same for all fuels. Lambda 1 is stoich. A lambda of about .85 is equal to 12.5 afr of gasoline, and I think about .78 lambda or so is equal to about 11.5 afr gasoline

 

so when tuning i should be aiming for a lambda of 0.78 whatever the concentration of Ethanol? meaining E0, E5 and E85 (we dont have E85 yet but got E10 & E5 stuff).

 

1 Lambda for gasoline is 14.7 AFR
1 Lambda for E85 is ~9.8 AFR

People tune for a range of AFR's (lambda) -- leaner on spool-up, richer by redline. Not just single value, that's why your question is somewhat vague..

0.78 sounds fine for regular gas (E10 is regular oxygenated gas) depending on its quality. Some people tune leaner, some may go richer if it's crappy gas (non-oxygenated; 91 from california ). That's why it's called tuning -- you have to find values that work for your car.
FWIW I tune for 0.77-0.75 on E85

But again, 0.78 is a good start.


That's correct, and here's what it means: stoichiometric ratio is the AFR at which the air/fuel mixture achieves the most complete burn. That ratio is called 1 Lambda.

So E100 Lambda is 9.0 AFR, and the max power rich AFR means that you can tune down to 0.71 Lambda (9 x 0.71 = 6.39 AFR ) and not lose power production of the mixture. Same goes for E85 by the way, its max power rich is pretty much 0.71 as well (9.8 x 0.71= 6.96 AFR).

To put in in perspective, gasoline's maximum power rich is 0.85 lambda (14.7 x 0.85 = 12.5 AFR) so whenever you're tuning for anything richer than 12.5 AFR you are gonna lose power. But you have to tune richer, for the purpose of cooling the burn, in order to prevent detonation. There's no such trade-off with E85, which is just another nice quality to it.

Hope, that clears it out for you a bit

 

ok i think i get it. yes i should have mentioned what i am aiming for in my car. at spoolup and till it reaches about 200+load the car tries to get AFRs of about 12.5 then i drop it to about 11.5 and then about 6k rpm onwards drop to about 11.2-11ish. all in third gear. lean spool is enabled so 4th gear will be more richer. we do this as gasoline runs hotter and cannot sustane the 12.5 AFRs at higher rpms.

going into lambda, now from the above if i understand you correctly then theoretically running E85 we can keep the car at close to the max power rich lambda of 0.71 as possible throughout the rev range (due to it running cooler and higher knock protection features) to give us higher power.

second question oxyginated gasoline (E10) what lambda value gives the theoretical max rich power (12.5 AFR on gasoline). our two variants of E10 is either eqv to 92 or 94 of US fuel standards.

 

I wouldn't worry about a "max power AFR" very much (max torque afr with gasoline is about lambda=.91 or 13.2-13.4 though). Within a range, afr doesn't make a very significant change in power. This range is smaller/larger in some engines than others, and going too rich or too lean can be dangerous. The biggest thing to think about when choosing an AFR is thermal management. The only real way to know what your motor needs is to test it. There are generalizations you can use and start with though (lambda .8 or 11.7-11.8 afr with gasoline usually works pretty well on most proper turbo setups at WOT). The biggest factor for power is to have timing optimized. You could be tuning timing for MBT and end up running an afr of 11.0 and 15 degrees of timing and make the same amount of power as running an afr of 12.5 and 14 degrees of timing (numbers made up as an example).

Running about the same lambda values as you are on gasoline would probably be ok on E-85 too, I would test it on the dyno though. E10 should be really close to the same as regular gasoline. Remember to optimize timing for these new fuels too.

 

Not necessarily -- richer mixture will most likely burn slower requiring more ignition advance to reach the same timing. Also you're not going to like your MPG. So i think 0.75L is just fine.


Probably a bit richer than 12.5 . Maybe 12. I don't think you need to concern yourself with this number though.

 

thankx guys. you have helped me a lot

 

fuel pump usually fail a lot sooner on ethanol.
We in Brazil have ethanol on pumps for more than 15 years.
90% of high power cars are tunned at ethanol on the streets.9
9 in 10 new cars are flexfuel in Brazil.