[Ryridesmotox]

Originally Posted by Damian

That sucks with your fuel issues. Do you still have the stock fpr? I can't imagine a 255 not being able to keep up, I could be wrong though.

The tank fuel pump isn't the issue at this point in this power range, although when it does become an issue, walbro makes some bigger pumps I will have to look at. The high pressure pump isn't able to keep up with the demand at this point. The injectors are able to flow enough but there isn't enough fuel getting to them. The is just too much airflow in the midrange to keep a proper air/fuel ratio. I am at work right now but when I get to my personal computer I can post up a screen of the HP tuner log to show what I am talking about. It's crazy how low the pressure drops but I still get no knock. Thats the beauty of E85 though I guess. At this point my tuner and I are makinga few little tweaks to see if lowering the pressure slightly will assist with the issue (we believe the pump may be cavitating causing pressure fluctuation/drop).

[sinaSRT-4]

Originally Posted by Ryridesmotox

I think so too... Since a bone stock lower end can handle up to 500WHP... now the trans is a different story.

Another Update: My car is on the stock Kd04. It is actually running up to 41lbs/min of airflow at the MAF according to my HP tuners logs. The E85 netted me like 30hp and torque at the wheels so I would think that I am right about 425torque and 360-370whp but I have to dyno it to make sure. I may swap turbos but I would have to tune back to straight 91 octane. As it stands right now I might have to run 75% 91 octane to 25% E85 or a 60/40 mix of the two. The 50/50 is just not getting enough rail pressure right now. I am running like 950 psi at WOT through the meat of my powerband from 3500-5500rpm And that is when my computer and my foot are commanding 2200psi of rail pressure. I keep throwing low rail pressure codes. And when I do it throws me into reduced power mode. That being said I am still pulling 4.7 60-100mph runs on average. If I run more 91 I won't need to run as high of a rail pressure since I will be running more "rich" than with the higher E85 mix. But the more I lessen E85 in the mix the less timing advance I run... Right now I am about 20 degrees of advance at WOT.

So we're looking at about 410 hp to the crank if you're flowing about 41 lbs/min (MFR). Times about 10% drivetrain loss approx: 369 whp. Not bad for a stock turbo.

Less E85 will mean more boost to compensate for the reduced timing. But boost is still better than adding timing in tuning terms. Good luck with the pressure issues you have going on.

[Ryridesmotox]

Originally Posted by sinaSRT-4

So we're looking at about 410 hp to the crank if you're flowing about 41 lbs/min (MFR). Times about 10% drivetrain loss approx: 369 whp. Not bad for a stock turbo.

Less E85 will mean more boost to compensate for the reduced timing. But boost is still better than adding timing in tuning terms. Good luck with the pressure issues you have going on.

Yea it is pretty decent for a stock turbo I suppose.

I have been running the same amount of boost on the E85/91 mix as I have on straight 91 octane. The added timing I am getting and the increased fuel volume is where I'm getting most of the power. I can run the motor more rich because of the Oxygen molecules in the E85. Even though I am running alot more fuel in the cylinders it is still at .88 lamda +/- on the wide band sensor. Here are some screenshots of the log in two different shots on the same pull. The first shot is of the MAF at peak airflow and the second is highlighting the high demanded fuel pressure VS. lower actual pressure. If you have never looked at HP tuners before it can be confusing, the actual readings are where the vertical white line is on the graph.

[Damian]

What FPR are you using?

[Ryridesmotox]

Originally Posted by Damian

What FPR are you using?

The computer controls fuel pressure in the high pressure pump. The LNF motor in the cobalt ss is direct injection. There is a "lift pump" in the tank, just like a diesel, and it is regulated to like 60 psi I think. But the low pressure pump is not the problem until like 500whp.

The fuel pressure is set to a certain demand, the high pressure injector pump tries to keep up but the fuel pressure in the rail drops because the injectors are open for so long. The stock injection window opens much later in the intake cycle. It is now beginning to spray at like 320* before top dead center and sprays until it is starting the compression stroke. Since my airflow across the MAF is quite high the HP pump can't keep up with demand since the injectors are open for so long. That is why I am seeing such a drop in fuel pressure in the rail.

[Boosten ya]

Any updates?

[Ryridesmotox]

As requested...

At this point my tuner, terminator2, has me reliably running E85/91 octane blend. He has kicked down the fuel rail demand a little to compensate for the supply issue through the torque range (3500-5500rpm) which is where I normally see fuel issues. That being said I don't make quite as much power as before when my car was always running into pressure issues of 950+/- actual vs. 2200 demanded fuel PSI. I am still showing peak MAF flow of about 41 lbs/minute. I will have some dyno results soon. I am going out of town for a funeral this weekend and the week after that I might be able to squeak into a dyno real quick to get some solid numbers.

Also in case anyone cares (I know I sure don't) fuel economy on my car right now is about 22mpg. That is about 98% highway cruising at 80mph with the cruise control on. From where I live in Carlsbad to Temecula for work. I'm not running the e for fuel economy, I have other tunes for that on my computer, I am running it for the extra 30hp it gives and saving $0.40 per gallon at the pump.

[Boosten ya]

Not bad man. Hope you can get your issues solved soon. I'm having some issues of my own, only able to run 3* of timing to not get any knock. I hope its a bad knock sensor.

[Ryridesmotox]

What car do you have? With HP tuners I can do most Domestics. I haven't tried to mess with any imports.

[Kozak]

I freeway raced a friend of mine from work Friday who has one of these. All he has is downpipe, exhaust and tune...I lost, but he refuses to race me from a dig! Which is my last hope, lol