AFR with E85

MNwe4

Member
What are people running for their target AFR at WOT? On the gas scale I've always been between 10.8 and 11.0. With aluminum heads and E85 do we need to be this conservative?

The car's gone as fast as 10.70 at that AFR, but I'm wondering if there's more to be picked up. My 80lb injectors are maxed out (100% DC) around 21 psi...
 

MikeS

Active Member
I tried everywhere between 10.5:1 and 12.2:1. I have iron heads. The car felt best on the street between 11 and 11.5. Never saw knock and boost was 25+ with pump gas timing on Eric’s chips.
 

Mr.Spool

Well-Known Member
What are people running for their target AFR at WOT? On the gas scale I've always been between 10.8 and 11.0. With aluminum heads and E85 do we need to be this conservative?

The car's gone as fast as 10.70 at that AFR, but I'm wondering if there's more to be picked up. My 80lb injectors are maxed out (100% DC) around 21 psi...
Your that conservative anyway running low boost.
With duty cycle high you need to look at fuel pump pressure flow and bigger injectors.
The plugs will tell you if you can lean down or not.nothing else.
 

MNwe4

Member
Thanks for the replies guys. I'll keep it under 11.5 for sure then. I realize I need to get more fuel some how.
I know my wiring to the tank is good, the sender is a newer racetronix unit, and the volt booster gets system voltage up to 15v. Fuel pump is the newer walbro 450. Lines are -8 feed, -6 return. 80 lb injectors. Tank is vented through original line with a little filter on the end, but I think I'll vent it at the rear of the car now. Using a 7 year old accufab FPR with an electronic pressure sender, but the offset is off in the powerlogger, so I see it rise and flat line with boost, but the number is wrong.
 

Reggie West

Well-Known Member
TurboBuick.Com Supporter!
You have everything else set for the fuel system.

Go get some 120s before you blow it up.
 

MNwe4

Member
That has crossed my mind especially when I finally upgrade to a modern ECM. I'm also pondering getting a set of 95's because I could drop them in without needing a new chip and just move my base FP back to 43 (50 now). That's around 18% larger and I believe more closely aligns with the capability of the fuel pump.
 

Reggie West

Well-Known Member
TurboBuick.Com Supporter!
So $400 for the right injectors and chip or blow it up and spend $3500 rebuilding it.........
 

MNwe4

Member
Double that for high imp injectors, but that's not the point. It's not going to blow up since I know I can't raise the boost how it sits and it's been this way for 7 years. I'm a proponent of maximizing what I have and trying to fully understand how all the parts are working together. I agree the 80 lb-ers are the weak point in the fuel system and will likely upgrade them. From replies here (thanks everyone) and other web surfing it appears mid 11's AFR on mild boost and E85 is the sweet spot.
 

Mr.Spool

Well-Known Member
Double that for high imp injectors, but that's not the point. It's not going to blow up since I know I can't raise the boost how it sits and it's been this way for 7 years. I'm a proponent of maximizing what I have and trying to fully understand how all the parts are working together. I agree the 80 lb-ers are the weak point in the fuel system and will likely upgrade them. From replies here (thanks everyone) and other web surfing it appears mid 11's AFR on mild boost and E85 is the sweet spot.
Not for higher boost or really high cylinder pressure.
Pull plugs and read them or have them read.
 

TTA976

Active Member
Double that for high imp injectors, but that's not the point. It's not going to blow up since I know I can't raise the boost how it sits and it's been this way for 7 years. I'm a proponent of maximizing what I have and trying to fully understand how all the parts are working together. I agree the 80 lb-ers are the weak point in the fuel system and will likely upgrade them. From replies here (thanks everyone) and other web surfing it appears mid 11's AFR on mild boost and E85 is the sweet spot.
yup go back to alcohol if going run it 11:3/4 ...11:6 is a great spot. Timing usually you can run in the 22-23* area with a stock motor/heads.
 

MNwe4

Member
yup go back to alcohol if going run it 11:3/4 ...11:6 is a great spot. Timing usually you can run in the 22-23* area with a stock motor/heads.
Thanks for the reply. I verified yesterday that my FP rises close to 1:1 by running the fuel pump and then applying 30 psi air pressure to the FPR. A 3rd gear pull on the highway with the AFR dancing around 11.2 showed IDC getting to 97% at 5500 rpm. Timing was 22*, 21 psi boost, and no knock. I'm now convinced that everything is working properly and this combo is maxed out. I agree with the other posters that if I want to go any faster I should just pony up for 120 lb injectors. Right now I'm completely happy with the street manners it has, very enjoyable to cruise.
 

Mr.Spool

Well-Known Member
Thanks for the reply. I verified yesterday that my FP rises close to 1:1 by running the fuel pump and then applying 30 psi air pressure to the FPR. A 3rd gear pull on the highway with the AFR dancing around 11.2 showed IDC getting to 97% at 5500 rpm. Timing was 22*, 21 psi boost, and no knock. I'm now convinced that everything is working properly and this combo is maxed out. I agree with the other posters that if I want to go any faster I should just pony up for 120 lb injectors. Right now I'm completely happy with the street manners it has, very enjoyable to cruise.
97% duty cycle leaves you 0 cushion.
The spray pattern goes away on the injectors.
Weather/humidity changes can really hurt you here.
 

TTA976

Active Member
If you're only going to bring it to the track a few times a year, just throw some race gas like C12..with ur E85.. . That's what I do. Have to tune it yourself thoug, a lot less work than changing stuff.
 
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