I could use a little help understanding my logs with E-85 in my Modified 2015 Z06. From the picture you can see I am running out of fuel in both the low and high side fuel supplies.

Here's my questions:
1. From the picture of the HPTuners log of the run on a dynojet chassis dyno the low side fuel pressure is not at requested levels before I go WOT. It appears to be at about 60 PSI instead of 73. Is that normal?
2. From the dynojet chart the A/F does not go lean even when the high side fuel pressure drops from requested 2,900 PSI to near 1,500 PSI.

I do not have access to HPTuners so any additional info would be from my memory of the runs.

Thanks in advance.
Wayne

 

Are you running full E85?
Looks like the it’s defiantly running out of low and high side. I’m running E40 and its not dropping nearly that much.

 

I am (was) running full E-85 which is actually E-65 out of the pumps here. Seeing the drop in pressure I added some 91 premium to bring the mix down to E-50 till I sort this out.

Did your low side pressure start that low? Did your A/F show or not show signs of leaning out with the pressure drop?

 

My low side starts dropping after 6k rpm but AFR on wideband is right where it needs to be. Id love to run full E85 but I can not afford the fuel system from Crawford Racing right now.

 

A lot of information there. MAN! that graph is hard for a layman to read.

What I THINK I glean from your post is that is your low side pressure is the same as mine, that both the low and high side are below requested, and your A/F didn't change with the drop in high side fuel pressure. Is that correct? If you have HPTuners and could post a graph of just those values before and through the pull I would really appreciate it.

I understand about costs, I am researching fuel systems myself. I will review Crawford Racing, have you looked at DSX's auxiliary fuel system? What others are you looking at?

 

 

No 60psi at WOT is not good. You want a base pressure at 60-65 (I run 65) and at WOT you want 1psi of pressure added per lb of boost. Do the math.

What low side fuel system do you have installed? Absolutely required for running ethanol as for E85 you will need to push or consume 30% more than 93 for example to make the same power.

 

"Do the math." ? Thank you. That's helpful.

My questions were: what was the base pressure, and did the A/F change as the fuel pressure dropped?

I know that running E-85 requires more volume of fuel than straight gasoline. I also know that I can run more mods requiring more fuel than most folks because I am at 6,000 feet, and have less O2 than at sea level. With less O2 the same mods here require less fuel than at sea level. My goal was/is to push the stock fuel system AT MY ALTITUDE. Clearly, from the HPTuners picture, I have reached the point of needing a low fuel assist and will probably install the DSX low side auxiliary fuel system.

My second question remains: Why, with both the low and high side fuel pressures dropping, didn't my A/F go up, showing an overall lack of fuel and, did orrwhat's A/F change as his pressures dropped?

 

Did you log Injectors pulse width? I believe if they are < 6 ms, A/F would remain at the same level

 

Yes I did. The pulse width did go higher than desired, to 7+ ms. What was interesting was watching the width in degrees. The ECM maxed out at 130 degrees, and it was clear it needed more fuel. Still, even with the pulse width in the 7+ ms range, and the duration maxed at 130 degrees, you can see the A/F did not go lean. Again, I'm learning this direct injection tuning and I (stupid me) figured the A/F would tell me I was running out of fuel. It did not.

For now I've dropped the percentage of E-85 down from 65 -67% down to 50% by adding premium E-10 gas to the tank. I will be adding additional fuel volume to the low side, probably the DSX kit. Any other low side fuel systems I should look at?

 

One thing that will help out with pump flow and fuel system longevity is to reduce the base fuel pressure. Most cars run 60psi nowadays but if you add 15 or 20psi of boost that becomes 80psi and its really hard on the majority of 'smallish' in tank pumps. What I do is reduce that to around 40psi of base pressure so that at full boost you get only say 60psi max of fuel pressure.

This will increase fuel pump flow rate. The less pressure, the more fuel pump will flow. As long as there is plenty of injector head room, there is no down side to this approach and it will help all the fuel components last longer. Just like in the human body where blood pressure being high all the time wears **** out and in a transmission the same thing, any fluid system should use the lowest applicable pressure.

 

That's interesting. I have not heard that approach before.

 

Wasn't trying to be a smart ***. I just don't know your max boost so you have to use clearly simple math to understand your max fuel low side psi is generally 60-65 + your max boost.

As for understanding air fuel i would keep in the back of my mind these aren't wideband O2s so they aren't nearly as accurate. Get yourself a wideband or 2 if possible one for each side. I run a holley port system which has a wideband i love it but with my setup I need a lot more accuracy so I am going with Holleys new 8 cylinder EGT system. Monitoring EGT per cylinder will for sure give you dead on readings of how lean or rich each cylinder is running. I would check DI injector pulsewidth also it has a max window of around 5 milliseconds. If you are near 80+ % duty cycles
you are nearing max injector usage. Also check if your tune is pulling timing. That will yank power and keep air fuel on target. There's my input. Hope its helpful.

 

You should be logging EOI, SOI, pulsewidth, Rail Pressure, and lo side pressure. These cars will hit their target lambda all day being under fueled, but that's just because the injector is staying open and blowing fuel out the exhaust. You want at least 500kpa to the hi side feed at all times, so you need a low side at minimum here. Under feeding the hi side pump is a good way to kill it as well.

General rules:
Injector Pulse Widtch 5.5 or less
EOI 180 or greater
lo side 500kpa or better

Rail pressure should match desired rail pressure within a few points if these are true.

 

I run a wideband at all times and a gauge on the OBD II connector giving a lot of data. During the run shown using the shop's sniffer for the A/F and HPTuners hooked up to the OBD II the max boost increased from about 9 PSI to about 11.5 at 6,400 rpm or so. Injector pulse width went to max allowed by the ECM, 7 ms. The A/F did not go lean, the power did not go down, the timing did not get pulled, and there was no KR, from the picture attached.

My theory, that the A/F would show me that the car was or wasn't running out of fuel seems incorrect.

 

Yeah, on these cars A/F is not a good indication of being out of fuel unfortunately.

 

The issue is that when pressure starts to drop and you make up for it with duty cycle, now fueling is always inconsistent.

its hard to explain without a ton of words.
Ill try example
say you desire 50psi of fuel pressure all the time but it drops to 40psi for one run and the engine leans out a little.
So you add some injector duty to bring the a/f back into target, great its 'fixed'.
Problem now is, the pump was 'maxed out', and if you leave it like that for long, all conditionals will wander, i.e. fuel temperature reflects it's density, pump warming (electronics = voltage/resistance) alters max flow, fuel demand of the engine flucutates based on IAT, etc... all those variables will cause the pump to drop more pressure over time, or not. It depends.
So you can't TUNE around a maxed fuel pump. Well, you "can" but only temporarily. because a pump at max flow isn't governed by its set pressure anymore and output will wander as conditions change.

So you could be fine today on the dyno but tomorrow sitting in traffic heating all that fuel up now you lose another 5 or 10psi and your back lean again.

Its not something you want to take a chance will. Never max a fuel pump and tune around it using injector duty cycle for long, its good for some dyno hits while you are watching a/f like a hawk but not reliable for the car in any other setting.

 

I've run mine down in the mid 40's going thru the traps at close to 150 mph on 16-17 Psi of boost. However that was on VP Ms109 and spraying 1000 cc nozzle of Meth/water. Never had any issues but on E you can't do that. Needs to be at least 70 on the low side so maybe you should look into the DSX low side to help bring the PSI up.

 

Yep, that's my next step.

 

Your going in the right direction. Let er eat.