vertigo262

I'm curious what would happen if you ran e85 on a stock tune on a Z06 with 63lb injectors instead of the 42lb injectors and if anyone knows what the estimated Stoichiometric air fuel ratio would be?

And don't say I'm CORNY for asking

Apocolipse

It would probably work fine if the injector response / delays at low pulse width are the same as the stock injectors. Otherwise the stft will go crazy. The harder part is making sure the e85 you get is actually 85% since many times it’s all over the place.

russ472

I am assuming stock tuning means you will not update the injector data in the tune . it probably won't run at all.

EvanZR1

This. E85 is not actually 85% E. I've seen anywhere from 50-70% E spring-fall, and over the winter I've seen as low as 25%. Without a flex fuel sensor and tune, you're going to grenade your motor.

Apocolipse

Yessir exactly

HowWhyWhyHow

Something happened legally where e85 means flex fuel anywhere between e51 and e85.

vertigo262

Yes Stock Factory tune! aftermarket injectors

Apocolipse

If it’s actual e85 it will be “ok” - outside of that and the stft/ltft will panic

Hib Halverson

I've contemplated the E85 without a flex-fuel conversion and "EvanZR1" is spot on. If you're talking about "E85" from gas stations that have non-race-gas "E85" pumps, it's totally a crap shoot and you seldom get fuel that's actually 15% gasoline and 85% ethanol. The only way to get E85 that's consistently a 15/85 gas/ethanol mix is to buy it from a race gas vendor such as Rockett Brand Racing Fuel or from a pump which dispenses true E85 racing gas.

If you ran true E85, could find an injector with exactly the right flow rate such that engine controls would stay inside the fuel trim bandwidth and had a fuel pump capable of delivering enough fuel flow to support the AFR required with E85, you might be able to run E85 with a stock calibration. The upside is 112-octane. The downsides are significantly lower gas mileage, the cost of the mods and that you could not run fuel with less than 85% ethanol without changing injectors.

Now there are flex-fuel conversions for LS7s. They will allow the engine to run on any mix of gasoline and ethanol, but they require an aftermarket calibration which will cause a car registered in California to fail the Smog Check.

ky13

Agree with most of what others have posted. And even though you don't technically need a flex sensor for Gen 4 ECUs (can use the virtual sensor option with LTFTs, although not as accurate a the actual sensor of course), you'd still need to toggle the enable setting, which would change your tune (from a checksum perspective). Bottom line, I wouldn't play amateur chemist and rely on trims to save you :P

russ472

When Hib mentioned CA emissions and noticed your area, I see what you are trying to do. I believe it is possible to do what you are trying to accomplish, but I think it would take some conversations with an engineer at said injector company that can match an injector that will put you at the needed injector pulse width the stock tune gives with the bigger injector. Whether or not there is an available injector that is close enough to those parameters and fit your engine is the question.

russ472

i think there may be an easier solution. If you have access to HP tuners and replacing injectors is a half an hour job worst case. Go ahead and do a flex fuel setup with new injectors.
when it is time for the smog test, change the tune back to the OEM tune, make sure you are running pump gas and swap back in the original injectors.

C6_Racer_X

That's still risky with CA inspections. I think the PCM tracks how many times it's been reflashed, and I think CA emissions tests on the PCM will fail you for that.

@vertigo262 , the simpler way to do this would be with 2 PCMs. Swap the PCM and the injectors. Install whatever tune (possibly with the fuel sensor) with the 2nd PCM in the car. When emissions inspection time comes around, swap the PCM and injectors back to stock and get your test passed, then swap back. The stock PCM with the stock tune should just ignore the extra flex fuel sensor.

I could never live there.

Apocolipse

No tracking in the pcm

Hib Halverson

The CA smog check will flunk a car with an aftermarket calibration, but the CA smog check does not read the calibration history, only the check sum and CVN of what's in the ECM at the time of testing.

vertigo262

That reminds me, probably for a different topic, haven't seen much reading about CVN bypass in the ecm. I think that would be a good topic

Josh M

I have a flex fuel sensor and monitor on my RS3 and yes, it can be frustrating for sure! I never knew that was a thing until I'd see the E % drop way off. Makes a tune rather interesting for sure.

As far as the OP's question I was kind of under the impression E85 on a lower power NA vehicle wouldn't see much as far as gains as well as add stress to the factory fuel system, aftermarket injectors included unless they were designed for it.

ky13

Colder climates will get a lower percentage ethanol blend to ensure that cars don't have problems starting in the more frigid months.

Apocolipse

Thats probably why Canada doesn’t bother with offering it at stations.

Colonel

Bad idea, IMO. Do it right or don't do it at all.