I've been thinking about this ever since the LNF CEL codes were posted and I looked through them...

It looks like there is a code that pops up when you go over 2500psi. Being that the engineers designed it to throw a code when that happens, I'm wondering if that's at or near the limit or over the efficiency point for the high pressure fuel pump.

Does anybody know of any definate limitations of the high pressure fuel pump?

I'm thinking that looking into some of these codes provide clues into the inner workings of the ECU (and LNF in general) and therefore give up some tuning hints. This may be a heads-up that even with fuel tables unlocked, we may still be up against a horsepower wall caused by the fuel pump and should therefore look into a solution to meet this possible need for when the tables are finally broken.

Input? Technical info? Discuss...

 

good point.... im pretty bad at tuning... have no idea how to do it... but you do have a point... may be tuners can save time by just looking into the graph and saying " ok we cant go over this amount of psi"...

 

bump

 

That is interesting and crappy at the same time. Max stock pressure is around 2100 psi IIRC.

 

A gm engineer on another forum mentioned the fuel system is capable of supporting much higher pressure, how much he didn't say but 600+ psi easily.

 

Ive seen higher than that stock at WOT near redline. 2400 is about the highest Ive seen, but I wasn't datalogging so I don't know if it went higher - not a good idea to be staring at gages when you are going WOT..

 

That's good to know. It also backs up what worries me in the back of my mind. Are you tuned?

If you're doing 2400psi now and the max from an ECU error standpoint is 2500psi, then that's not much room to work with. There may have to be some fuel pump swapping or ECU reprogramming. Hopefully the pump is just underrated.

 

Fuel pump efficiency range is not a factor in tuning; fuel pump ceiling numbers are. (excluding boost-a-pump hackjobbery which we will leave out of this discussion). In short a modern car fuel pump will either supply enough fuel or it will not, you will not make any more horsepower being at 50% vs 99.9% pump capacity. Naturally hitting the actual pump limits will have consequences

There are 2 pumps on the LNF Cobalt, a traditional electric pump in the back and a second high pressure pump which is driven off the camshaft. Max stock pressure is 2250psi and it will rise with rpm (not necessarily linearly). The high pressure pump on Direct Injected engines like the LNF is there to atomize fuel ; as long as the fuel is properly atomized, more pressure won't really get you anything. More power and higher cylinder pressures will also not impact Direct Injection pressure requirements because it still functions like a traditional four-stroke engine with the fuel being injected opposite the combustion stroke.

Having said that, I wouldn't hold my breath for any aftermarket higher flow injectors anytime soon. There is a fairly small number of DI cars, none of which have heavy aftermarket support. There is also a huge liability in making injectors to safety handle 2250 psi vs 100psi as well as more heat.

Cliffs: Not an issue.

-Mike

 

the reason for the 2500 is because more fuel pressure will cause issues at stock setup .. vince at trifecta is working on some fuel pressure solutions that are looking pretty good so far as well as some map changes so you can do 26psi on stock setup

 

That would be pretty handy when coupled with the newer 3bar TMAPs.

Thanks for the info.

I'm not sure about a max of 2250 though considering IsItFast just stated he's had his up to 2400 already.

I agree that the chances are slim as of now for aftermarket DI products. Hopefully as GM/others put out more engines with DI, the spotlight may shift a bit. I wonder if when we get the fuel tables unlocked if we're going to find the concrete max of the pump. I feel that's going to be a very important factor in performance as we move more to the Stage Kits and larger turbo setups.

 

yea he's looking into some way to get some 3 bar maps .. right now he's actually spiking over 26 psi but he cant tell how much part of the issue is he's using a map rescaling function so as the car revs higher things change .. he said it works great on the turbo upgraded ss/tc he's working on and it works great on his stock hhr ss he's looking to do boost referenced fuel pressure as well

with the 3 bar maps he could accurately control everything above 24 psi very easily and make the fuel pressure much easier as well .. if he can work that out you'll be seeing a CIA/ trifecta stg kit coming out

 

Wow, it sounds like Vince has quite a bit still up his sleeve...

I can't wait.

 

yup man esp now that he has an LNF.. i always bring things up to him .. I mentioned the issues to him and he's been working on it ever sense

 

Well, what's he waiting for?! He needs to start releasing things already.

 

he's testing things to make sure everything works well .. so far he has the scaleable map setup.. he's just ironing out some things and then trying to get the other end of the battle conquered

 

This is getting me all giddy! Vince will be a very rich man if he is the first to crack the fuel tables in the LNF.

 

hehe he's working on it guys.. right now he's hitting 28 psi on his hhr ss lol it falls off to like 26 at redline more then likelye because it's running out of steam lol it's good stuff so far.. he thinks he sees some things to easily work with the fuel table

 

Baldturbofreak was saying that the k04 taps out after about 36lbs/min. With the fueling window being an issue and the turbo not being able to flow sufficient air when you're reaching very high RPM, I'm thinking most improvements will be in the mid-range. Up high you're probably looking at falling off pretty quickly, like is what is happening to most everybody that's tuning it now it seems.

I know it's a long shot, but if Vince can pull something off on offering a 3bar sensor + fuel map something-or-other before the Stage Kit is out, I may go with him instead. ...or is it more of a GM Stage Kit addition?

 

well right now with his map scaling setup he's not needing a 3bar map

 

So can he scale a 06 2.2 cobalt using the 2bar sensor from zzp? Everytime I get a tune from him the low end is lean and the high is ok:
3000-4500 I get 12.5a/f
4500+ I get a 11.9-12.1


So hopefully this Sunday we can tune the car over good, I'm running 1 point to lean now, 13+@wot not good LOL

 

he might be able to i was thinking about that last night.. thats weird you have that issue .. my car is 11.6-12 all the way through..

 

Looks like Vince's secret is out... https://www.cobaltss.net/forums/show...59#post3990459

 

hehe yup... ifiniboost ftw

 

X2. That is not the only thing in the works though.

 

Yeah it's weird, the tuner is coming Sunday to help retune my car....just needs more fuel...sucks not being able to go wot