I'm thinking alot on converting from alky to E85 on a 20GLT since there's a gas station that sells it less than a mile away and a dozen others close by. If I upgrade to 880 injectors, would that be more than enough to feed the 20GLT? I also have the walbro fuel pump. I will be flahing my ECU for the upgrade. Thanks

 

Buschur would be the ones to ask. I think you will need a twin fuel pump setup and probably around 780's.

 

880's could be enough the single pump could be enough. It will depend on your combination of parts and the power potential of the car. I am guessing since you are going to reflash the car it won't make enough power to use up the 880's and single pump.

 

Thanks Dave. I'll be calling you soon on the 880's.

 

^ See Buschur has the answer.

 

The 20G-LT has a 49 lb/min compressor wheel from what were told and from some logs from people maxing out the turbo. So, if you were to max out the turbo you would need enough fuel to match the 49 lb/min of airflow.

How much fuel you need to match depends on the AFR that you will be running. For a quick example, let's just use gasoline first, then I will explain E85. At 11:1 AFR, you will need 49/11= 4.45lb/min fuel. At 12:1, you would need 49/12=4.08 lb/min fuel.

So, at 12:1, that 4.08 lb/min fuel = 1852 grams/min fuel

4 880cc/min fuel injectors = 3520cc/min fuel = 3520 *.76 (specific gravity of gasoline) = 2675 grams/min fuel.

So, using gasoline at 12:1, 880cc injectors will provide plenty of fuel for the 20G-LT.


Now, with E85, you can use the general rule of thumb that you will need about 30% more fuel for a rough estimate, or you can calculate it again, using the AFR you will run on E85.

Stoich for E85 is about 9.8:1. Alot of people seems to be running e-85 at around .85 lambda. This would mean an E85 AFR of 9.8*.85= 8.33 AFR. Or, if your wideband can't be changed for different fuels, your gasoline calibrated wideband would show 14.7*.85=12.5 AFR.

So, let's see if your 4 880cc injectors can provide enough fuel at this 8.33 AFR. We just do the same calculations as above:

49lb/min airflow / 8.33 AFR = 5.88 lb/min fuel = 2670 grams /min fuel.

4 880cc/min fuel injectors = 3520cc/min fuel = 3520 *.78 (specific gravity of E85) = 2746 grams/min fuel.


So, 880cc injectors will just be enough to max out the 20G-LT turbo at an AFR of 8.33:1 (12.5:1 equivalent gasoline AFR).

The questions now is whether or not your fuel pump can flow enough to match. If it can't, then it will be losing pressure and you will have to increase your duty cylces, which then, the 880CC injectors will not be enough.

Just go through calculations for your fuel pump, too. If you pump is up to the task, the 880CC injectors will be fine.


Eric

 

I don't agree.............sorry. First off, nobody in their right mind is going to tune the E85 that lean for a street car so the 880's won't be enough IF the car makes the amount of power it is capable of. The math is correct but tuning for AFR's that lean on E85 is not the way to go.

I just did an E85 green turbo yesterday. 1,000 cc injectors and a double pumper, car made 422 whp on our dyno and the injector duty cycle was high upper 80% range. The one thing I don't see that you took into consideration is duty cycle on the injectors. You are figuring the maximum flow of the injectors and running them at 100% duty cycle, right? I've done it and still do it (running at 100% duty cycle) but I'd recommend at most figuring running the injector at 90% for some safety. This safety margin can be easily used up with very low air temps and the extra fuel required when hitting these lows.

blah blah blah........

 

Dave, I used .85 lambda because I am simply going off of what I have seen many others tune for with E85 already. I have yet to convert to it, so I can only go on what I have seen and read at this point. But, I at least gave him the ability to calculate for whatever lambda he will tune for.

And, yes, I wasn't calculating a factor of safety of 80% duty cycle. I was merely showing whether the injectors can support that airflow. That's up to each individual, but in general, I agree with you that you should be safe and take the 80% duty cycle approach.


Eric

 

Thanks guys, this is very helpful information.

 

Just FYI, I run 100% E85 on my GSX. I put down over 500whp and tune my AFR for 13:1 (on my gasoline wideband)

This fuel is amazing. I have hit AFR's of 14.5:1 @30psi with no knock...crazy stuff.

 

But, is your EGT save? 13:1 (with is 0.884 lamda) is a behind the max power for E85 so the EGT can be to high, isn't it?

 

Good for you. Just dont suggest running this kind of afrs to anybody else.

 

I wish we had E85 in Jersey. 422hp on Buschur's dyno with a green on gas that can be had at the pump, that is pretty amazing.

 

there bringing this e85 stuff to my local pumps later this year, will i gain quite a bit extra power if i had the green mapped on this over 93 ? any downsides? its the same price as normal pump here when it comes out!

 

so what airfuels do you suggest to tune at on this wonderful stuff? also are you making it yet? thanks for the help!