LSJ E85 conversion

[mike_sno]

Hi Forum,

as I am on the path of converting to E85 I have so many questions. I thought an own threat would be the best way instead of putting it on my build log.

Currently I want to figure out if my fuel system is good enough. On Hp Tuners and Cobalt Forums, you read that the fuel pump is good. However, I have the LAP fuel pump, not the LSJ.

My idea is to just poor some E85 in the tank, connect the fuel pressure gauge to the rail and see how bad it is.

In order to do the minimal tune to E85 is it sufficient to change the AFR ratio to 9.5 and add a few degrees (maybe like 4?? ) of timing due to the slower burn rate?

 

[G Atsma]

One thing to consider about E85 is that it isn't always 85% ethanol. The ratio can be all over the map. This is why engines so equipped have flex fuel sensors. Unless you KNOW the exact percentage of the E85 your using, BE CAREFUL.

 

[Ross]

I'm not sure where you can get an LAP E85 tune, but I would try to find find one if I was you.
Check if other cars have your 32-bit computer E37 engine control module that the LAP is using.
HP Tuners has a compare tune feature, that will give you some good ideas on things you may want to add to your tune.

 

[mike_sno]

I have the LSJ computer, just the LAP Fuel pump and filter.

 

[Ross]

There are a few E85 LSJ tunes listed on post 1 of my build thread.
Check out what others have done compared to your tune!

 

[mike_sno]

Did the test run today. Simply changed the Stoich and that's it. Overall my tune is very rich in PE.(Was it already with my gas tune) Watched my wideband and the Fuel pressure. Fuel pressure dropped to 50psi under worse case conditions and I noticed the pointer on the gauge was shaking quite a bit.

Injector DC up to 108% again. But still I could not see that the wideband picked any of that as a lean condition up. Maybe it's because it such a short time when I am at 7000rpm and high boost before I switch gears.

I think at the moment I can keep my current set up. Fuelpump, Injectors might be at the maximum, but for the moment it works.

Added 2 degrees of timing and still don't see any knock. Next I will lower the PE, as this should help me also with the Injector DC and the fuel pressure.

 

[Ross]

I know the LSJ can benefit from bigger 12V power wires to the fuel pump, and wonder if the LAP is the same. A voltage measurement at the fuel pump would confirm how much voltage drop the fuel pump has. It is a cheap fix to get some more fuel pressure out of the existing pump.

 

[mike_sno]

Does anyone know if a standard fuel line is E85 compatible? I asked at Autzone and the fuel line they sell is just rated as “fuel line” LOL. I would assume that all kind of fuel lines you can by at the moment are E85 compatible. I looked online and couldn’t find a decent answer.

What about the connection line between the fuel tank cap and the fuel tank. Is that E85 compatible?

 

[Gtstorey]

I don’t think there is really such a thing as “standard” fuel line.Anything that you get that isn’t labeled for ethanol will have a chance of not being compatible, although it is probably only a slight chance. Just as important is that it be fuel injection hose for the increased psi.

I wouldn’t worry as bout the filler nick since it seems to be constant immersion that causes problems. Unless you fill your car to overflowing and then park it.

 

[Rttoys]

this is what I used for my fuel lines, but I don’t do e85.

Fuel hose Gates Barracade 4219BF 3/8” x 25’ 27341

straight from Gates website, says it’s compatible:

4219BF Barricade™ GreenShield™ Fuel Hose | Gates Corporation

Before you start your engines, equip them with Gates fuel hoses. We’ve engineered our fuel line hoses at the cutting-edge of fuel-efficient, environmentally-safe design, so your engine will perform with superior power.

www.gates.com

https://www.gates.com/us/en/fluid-power/engine-hose/fuel-line-hose.p.4219-000000-000000.v.4219-05652.html

 

[jirwin]

Don't bother with anything rubber. Go PTFE

 

[mike_sno]

After weeks of logging, tuning, flashing... I think I understand now halfway decent how this all comes together. A few things make me still wonder...

E85 has a high tolerance. I believe somewhere between E50 and E85 would all be acceptable at the gas station. The LSJ has no flex fuel sensor, so it does not know what the ratio is. It is my understanding that depending on the alcohol amount the Stoich number changes. Gas 14.7 and E85 around 9.8 and anything in between depending on the Gas/Alcohol amount..

With that being said, in close loop the short term and long term fuel trims will compensate for the missing flex fuel sensor and adjust fuel so long until the Stoich is reached.

Is the relation between E85, E10 and Stoich linear? Means, can I calculate the correct Stoich number with creating a function out of the 2 points I have?

The way I tuned my car so far:
1. Setting the tune rather rich, low sparc adance and a few other things.
2. Forcing it in MAF only to calibrate MAF curve with my wideband Sensor.
3. Fine tuning the MAF curve with the LongTermFuelTrims in close loop.
4. Forcing VE only and calibrating the VE curve with the wideband Sensor.
5. VE tuning with LTFT in close loop.

 

[mike_sno]

Another question I have:

The LSJ Fuel Trims have 3 RPM and 3 MAP boundaries. That would create a 3x3 table with a total of 9 values. That would tell me that using a LTFT for tuning is not very accurate as e.g. the VE table has many more fields.

Are you guys adjusting the LTFT boundaries if you tune with the LTFT?

 

[Rauq]

Is the relation between E85, E10 and Stoich linear? Means, can I calculate the correct Stoich number with creating a function out of the 2 points I have?

Yes.

Are you guys adjusting the LTFT boundaries if you tune with the LTFT?

I'm not sure how much of a concern this is to begin with, but here's 2 ways I see to mitigate this.

The first is, get a ton of data. If your VE map at 59kPa and 2400rpm is a bit rich and at 53kPa and 2400rpm is a bit lean, with enough logging you should be able to catch that. Smoothing can make up for the remainder.

The second is, log STFT+LTFT. I believe STFT is instantaneous, so it should catch the difference between low RPM + low MAP applying to a whole range vs individual cells being high or low.