So does anyone know the specifications on our fuel pumps, like how much they flow max, and since were running 42's and + should we recommend buying a better and much more efficient fuel pump, that way just incase were not getting the fuel we need and were leaning it out, and poping pistons... anyone?

Bump.

 

Han get 60lbs injectors...or go return style

 

Well I am I prolly gonna go 72's for TVS but I donnt wanna run stock fuel pump if it cant keep up with the injectors, and lean it out, and burn up my pistons, and maybe then some

 

Eople have gotten 450hp of stock one, tvs won't get u that high

 

Yeah that maybe true but I wanna know why it is everyone keeps blowing they're pistons/Rings, is it because they're leaning it out to much because of the lack of gph on stock fuel pump cant keep up or is it something else?

 

It's because they can't tune. I've run 79s without meth and a 100 shot of nitrous on the stock pump and it never went lean once. It's just easier to get the car to idle with a return style system. Get some methanol with a 7GPH nozzle and 60s and you will be fine.

 

they blow up bc #4 naturally runs leaner than all the other cylinders, being that its at the end of the fuel rail, a return style fuel system would solve this issue, or you can tune for #4 inkector to give a bit more fuel than the rest...flow match your injectors, tune correctly, and yu shouldnt have a issue running the TVS w/60lbs injectors, if you really wanna be safe about it, get the return style fuel system.

 

Ok makes since thanks for the advice, now where do I buy a return style fuel systm at?

 

This has never been proven to be true. It is a theory.

You can buy one here.

http://www.ottperformance.com/Cobalt...duct_info.html

But you may or may not need one.

The stock fuel pump runs at 60psi up to 17.5 pounds of boost. After 17.5psi the fuel pressure will drop with every pound of boost added.

 

ottp has the returnline system,, do you really need it probably not. if you want a better pump only ottp also has the walbro 255 fuel pumps but you have to modify your sending unit.

umm i dont think it drops, your ecu just cant calculate for anything over 17.5lbs of boost.

zzp also has boost refferance setup but i dont know if anyone has used it, for every lb of boost over 17.5lbs it gives you one psi to match in fuel. they also have s rewire kit but i dont know how long your pumps going to last with a higher voltage going to it..

 

umm nope. The ecu can "calculate" anything over 17.5lbs of boost but it will stop adding fuel pressure past 17.5psi. When the ECU is "calculating" under 17.5lbs of boost it is adding 1lb of fuel pressure for every 1lb of boost to maintain 60psi of fuel pressure.

At 18.5psi of boost the fuel pressure will drop to 59psi. At 19.5psi the fuel pressure will drop to 58psi.

 

and the fuel pressure should be getting higher along with boost shouldnt it. the ecu cant do correct....if im wrong o well im not a tuner

The PCM doesn't compensate for boost over 17.5psi , so the car goes lean after that. This is unless you raise fuel pressure the same amount as boost. You can try and tune around this but it's guess work and a poor solution.

 

Yes it should. Unfortunately it wont after 17.5lbs of boost with the LSJ ECU.

But like mentioned in this thread it is really not a problem with the 79# and 80# injectors now available for the LSJ.

Good Maf tuning can fix that.

 

which like i was saying

 

That depends on the tuner. It should NOT go lean if your tuner knows what he is doing.

Its an educated guess! lol

Oh yeah. This is not necessary true either.

So it depends on the year of the car.

 

im in for no worries on mine i have higher than factory fuel pressure, so im pretty much in the clear on that on, on the current set up.

 

LOLZZZZ you two are arguing over the same thing. just one worded it diferently then the other. lol.

 

know **** sher-lock. did i state that i was having this issue NO.....come on eric dont get all jumpy on my here.

pretty much lol i just like givving eric ****

 

Go with 60lb injectors and leave the stock fuel pump alone as it will be plenty fine for that setup with the TVS. It would also be a good idea to go with the return style fuel system. Absolutely no point in going with the walboro pump, Josh and Sean will prob tell you the same thing. If you go with anything larger than a 60lb injector you are just making it harder on yourself as far as fine tuning goes and its overkill. So just go with the 60's and return style(if you chose so) and call it a day.

 

I never had a fuel pressure issue on my car unless my meth would run out. fuel pressure would stay consistently 58psi. Factory fuel pressure is supposed to be 55-60 psi. and factory computer can control up to ruffly 22 psi. factory map sensor is 2 1/2 bar after that it just uses the last fuel/airflow table hit and just continues on. these computers are very advanced and easy to work with if you get the basic concept of how everything works and how to analyze it

the car can compensate for fuel-boost ratio due to the fact its got several sensors to cross reference with along with base settings if the sensors were to max out. but ive never had a issue with that before

 

Where the hell did you get that from? It's not guess work at all. You stated you weren't a tuner, good, let's keep it that way and keep the thinking stuff to the people with brains. It's posts like that and threads like this that start rumors we don't need. Vaccum based fueling (return style systems namely) is made for one thing, linearity/ease of fueling. Yes as fuel pressure increases, so does the injector flow for the same given PW. This is good for one thing, using smaller injectors to get a good idle quality for feel and emissions. A constant fuel pressure is a great idea, so long as the PCM has the ability to shorten PWs in lower loads and lengthen them at higher loads. This is why returnless systems run much higher PWs and can max out an injector quicker than return style. In a small displacement engine it's very hard to get a solid flow at idle out of a 79lb @ 3bar injector when the car is feeding 4bar to it, effectively making it a 92lb injector. It gets down to PWs in the .5ms range, which most big injectors don't like to/can't do. The easiest way to get a big ass injector like that to idle on a little tiny 4-cylinder that basically requires no fuel to idle, is to simply raise the idle so the PWs on the injectors are closer to around 1ms. Usually 1,000rpm on the LSJ will do. Yes it will use some extra fuel, but that's the trade off to staying returnless. And let's face it, if you NEED to use the 79s, you are probably making at least 400hp so fuel economy probably isn't a big concern to you anyhow.

To the OP, from personal experience with the Harrop on a 2.8 pulley (and even a 100 shot of N2O):

Use the stock fuel pump.
Use the Siemen's 60s.
Do a 7GPH meth nozzle, preferably progressively controlled. The meth will allow you to lean things out a lot and run those smaller injectors.
The LS4 TB is touchy, but makes the car much more responsive than the stock TB.

You will be fine and don't worry about cylinder 4, it's fine. What I find funny is that half the time I hear it's the "infamous" #2 cylinder ring land failure, then it's the "infamous" #4 cylinder. Someone somewhere screwed something up and it turned into FACT that these cylinders blow out commonly. They don't. If ANY cylinder were to have high failure due to lack of fuel it would be cylinder #1. If you ever looked in the LSJ fuel rail, you would see the protrusion over the injector feed hole that would cause fuel to be choked off from it. Even a return style system wouldn't fix that unless it was drilled out, which you could do with the returnless system. But it doesn't have problems, and neither will you if you find someone who knows what they're doing with the car and tuning it.

 

Ok thank you understood, 60's it is, and Im gonna see if wicked will tune for me again lol, I like his tuning well just for the simple fact that I havent had any problems and he's a good guy. But yes you guys all cleared up alot for me that way I can do this correctly an more efficently.

 

from the people of ottp and zzp and along with the people that thump their holy grail, look like i was mis informed by yet another vendor and their nut swingers......its a shame....im not stupid, i know the basics of tuning, i have my own private tuner that knows his **** and has been doing it for years. but thanks for confirming that the info from vendors that i posted was incorrect.

 

Tuning past 17.5 psi is guess work if the FP in the car remains at 60psi. This is because the PCM has no idea how much boost you have and you therefore cannot 'tune' precisely for it. Can you tune around it? Sure but it is not ideal, nor accurate.

For anyone making over 17# of boost or big power, the BRFP system is the way to go. It's $200, fixes the idle issue with all larger injectors and gives you enough room to make 400WHP with a stock pump and 60# injectors.

http://www.zzperformance.com/cobalt_...1015&catid=174

People installing it are loving it. Easy to use and very effective.
"Worked out great i went form 11.8 AFR at 21lbs to 10.1 (possibly lower but guages dont go that low) so i upped the boost to 22.6 and the AFR is still at 10.1 Also it cleaned up the idle ALOT. "- from one customer

 

I rather just spend the extra bucks and do a return fuel system and not have to worry. A I never had a issue tuning my turbo setup up to 30psi. fuel would stay consistent all the way thru the rpm band