Originally Posted by Matt M

We fired up my '08 SS today with the new turbo setup, and I had time for a few dyno pulls. I will post the news in another thread. You guys are going to like the results.

Originally Posted by interviewatruins

alright, so lately i've been trying to learn ALL that i can about the lnf, as i'm getting one in a few months.

HOKAY so, about this 400 whp.....i've been wondering about that.
then i saw this post in a trifecta vs gms1
- "I dont see how you can compare custom tunes from trif and htp to the GM stage 1. They are soooo different, your talking a custom tune to get the absolute most out of the car to a tune from the manf. that keeps things very safe. Now trif vs hpt is comparable, they are after a very similar market.

Even as Bill said, once they get the fueling tables unlocked...400whp and up should be pretty easy. "


I was just wondering what you thought of that statement. Is it true that once those are unlocked there is no need to wait for a di upgrade?


So I emailed vince about it as I normally do when I have any questions involving tuning.

This is his response.







Which part? LOL

If you are referring to the comment about the fueling, here’s what I will say about that:

1) People have told me if you try to go past about 400WHP you have fueling problems because the injector pulse is too long

2) A guy on LNFPerformance forum that claims to be a GM engineer alluded to the fuel issues being related to fuel rail pressure and that the stock injectors are good to 700HP

3) The fuel rail pressure is ECM controlled on the TC and can be modified in the ECM calibration

The fuel rail runs at a maximum of around 2200psi on these cars without “fueling tables unlocked”. I don’t know what the maximum rating on the fuel rail equipment is, but in theory more pressure would give more fuel per degree of time in the pulsewidth, which would allow more horsepower without fueling problems. I have been approached several times about making fuel rail pressure changes but not by anybody serious about actually needing it yet (e.g. I am NOT giving fuel rail pressure tweaks to someone who believes the reason he’s not making power at 6600RPM on the stock turbo is because of fueling).

I am also hesitant to put anything out there that modifies the fuel rail pressure until I’ve tested it well. Imagine what would happen if you had a fuel leak under the hood with the fuel at 2500psi.




discuss

Originally Posted by Blk08coupe

I had figured that if it was injector pulse timing related, then why not increase the time of injector duration? Wouldn't that allow more fuel w/out having to raise fuel pressure? Like increasing injector duty cycle on a regular efi system. I'm still learning this new DI stuff so bear with me. I have the basics down, just trying to fine tune the details.

Originally Posted by pt5457balt

My email to vince today:
"Hey Vince,
I came across this thread on cobaltss.net (https://www.cobaltss.net/forums/showthread.php?t=192508) that was talking about fuel tables and things like that. One of the people in the thread states to have received an email from you about one of the reasons you haven't looked into raising the fuel pressure to make more power is that you haven't heard from anyone with a bigger turbo wanting to do it.
Well, as you know, i've felt like there was a lot more power to be made with the car, even with it running the way it is now. Perhaps this is something we can also look into so we can get more out of this turbo swap? On a few occasions, i've had a DTC code telling me that fuel pressure was too low. Perhaps this is causing the hesitation up top when making runs with the car?
Anyways, you know me, and i'd definitely like to get more power out of this swap. I've had serious thoughts lately of going to a rewheeled/ported/clipped k04 with the way this car is performing against heavier cars that should be making less power to the ground than mine.
Hope to hear back from ya!"



Vince: The way your car is currently set up, it does not need fuel modifications.

The fuel pressure tweaks are for people that have trouble keeping the fuel
ratio under control at high RPM / high boost, of which I have not seen any
trouble with your car in the logs.

Me:Well, i'm not sure what to say then. At highboost and highrpm is where the breaking up occurs, and where i'm receiving the fuel rail pressure low codes.
at 26psi, it'll run fine under several wot runs back to back, but it also struggles very hard to pull away from scott's car up top when he only has a tune, and a catted downpipe, and will usually only inch out by about a car. When comparing the two (mod for mod), there should be no comparisson between his car, and a turbo swapped, 3inch catless downpipe, 3 inch catback, hahn intercooler.
The last batch of logs i sent had a run at 26psi, where there was no break up at highrpms/boost. The other two logs, there was break up as the boost went up to 28psi. Also, after those runs, i received fuel pressure low codes.
What would you advise that we do to get this car performing on the level these mods/turbo should be performing at?

Originally Posted by Matt M

Increasing the pulse length is what causes the issue. When you spay fuel directly into the cylinder, you are limited by valve timing events. The cure is to raise fuel pressure or install larger injectors and keep the duty cycle under 30% if possible.


If you have a code set for fuel pressure too low, you have a problem with your pump, regulator, or pressure sensor. You will not be able to fix the issue with a computer swap. That code means that the ECM is already trying to raise the pressure higher than it will go.

Originally Posted by northvibe

The issue on the ms3... it was not fixed or helped much actually at all. The only thing the new internals on the cdfp helped was keeping the pressure at WOT to full psi. I dont have time at this minute to explain the issue as its exactly the same as the ms3 but I will after my work. It has to do with the amount of time you have to inject the fuel/air mix and cam timing. There isnt enough time during a cyle to inject enough in to get more power. Look at vw's they found a way to tune to get more time and they are (on DI engines) able to get 600+whp.

To the OP why didnt you quote the person saying those quotes on post 1? They look familiar to me

Originally Posted by 09CobaltSS1

where's the thread damnit?!?! lol

Originally Posted by Matt M

We fired up my '08 SS today with the new turbo setup, and I had time for a few dyno pulls. I will post the news in another thread. You guys are going to like the results.