Pick up a fuel rail from a 2002 Cavalier LS Sport, a walbro fuel pump with the inlet and outlets aligned with each other (the one that doesn't have staggered inlet/outlet), an adjustable fuel pressure regualtor, a single inlet/single outlet fuel filter to replace the stocker, a couple GM style quick disconnect fittings, some fuel line and remove the stock in tank regulator.

You have yourself a return style fuel system and will be able to stretch smaller fuel injectors to new heights and huge injectors will react well to low map conditions.

 

for a little more then what i spent on the 60's and harness, i could have done that.

what about this idea.

add an inline fuel pump, add a regulator, add a return line. keep the stock pump and tank all happy, while adding more fuel to the system.

hmmmmmmmm.
maybe not, this may throw off the calc tables and all that jazz.

 

You would have to tap the tank or fuel fill tube for the return line. If you replace the pump/regulator/filter you can connect to the return line thats installed from the stock filter back to the tank/regulator via a quick connect fitting.

 

Sooooo who's going to make the return fuel line kit??

I wouldn't hesitate to purchase................. I nominate witt

 

lol, I've got lazy with the car and really don't have the time to invest into it much anymore.

I will however be installing those parts on a certain turboed redline in the next week or two. It now has a built bottom end and high flow/high rpm top end with a need for at least 750cc on a return style system to accomplish the goals he has in mind which includes using the stock PCM, keeping the car as a daily driver and touching 3 bar manifold pressure.

 

lol. i knew that was comming.

now, the question that will lead to a huge gray area with this.

since the fuel pump gets sent varying voltage, depedant on load. taking the stock power leads to the pump itself. moving them to the other pump, like a simple boost a pump, but with factory wiring. whats going to happen to the injector tables, since they are based off what the stock pump does. are we back to square one? my thinking says yes. then again, my thinking has also prompted some really dumb questions before.

or, do we just leave the tables alone, and see what happens with the a/f and tinker with them to get it to where we want them, like what we are pretty much doing now with the 60 lb maps.

 

Its a constant voltage. You're thinking of a PWM (pulse width modulated) pump, which the 2.4 PCM is equipped to handle but no cobalt actually uses. The in tank regulator handles the job of fuel pressure/fuel demand.

Boost a pump would just require fine tuning of the airflow tables at the high end just like any other airflow mod. Return style system requires flat-lining the injector flow rate table.

 

so in short, if we added the return style setup, one could go into hpt, and set the tables at 60.0 across and call it a day. set the regulator at 43.5 and see what happens.

pmed ya d00ders

 

Heres a couple pics I have of some of the fuel components to make it a little easier to understand how the entire system works when it comes to converting to a return system.

Stock in tank regulator located inside the fuel canister at the end of the stock return line:



2002 Ecotec fuel rail, indentical to ours but with a return fitting already tapped:



Stock fuel supply and return lines that both run to the stock fuel filter:



Stock fuel pump with inline fuel inlet and outlets:

 

very interesting to say the least.

the return line smack dab above number 2 bothers me though.
im used to dsm's go figure

 

I agree, I still feel its a better setup than a returnless system though.

I was thinking of a witty DSM joke but I'm having a brain fart, maybe next time.

 

lol im sure you will think of something later and e-mail it to me.
laff

why not take out stock rail, take off that little piece on the end of the rail and just tap a fitting into that?

 

You know I was already aware that I didn't include any calculation for the differential pressure (that VERY important data that I've mentionned tons of time in the past) and there is some reasons for that :

The reasons are :

1 : The Stock SS boost 12 PSI max. I now think this is not a safe and optimal setup to boost more than 15 PSI on the Eaton M62 when not running any methanol or importants cooling mods. Don't get me wrong I've done that before but yesterday I downgrade to a 2.9" pulley which brings me to 12-13 PSI @ 3500+ feets elevation. A lot of guys are getting knock retard and some are not even aware of it. It happens even when running the best 93 or 94 octane pump gas.

2 : It is certainly not the majority that runs (or want to run) with some methanol, a twinscrew swap or a turbo. So those (a lot of people) that put down 250 ishh or less whp (dynojet) should not need injectors as big as 63 pounders if they keep the boost below 15 PSI (2.9 pulley), thus in a raisonnable efficiency range. I'm talking when tuned with an optimal tune, not a crappy 10 AFR for most of the powerband.

A comment on Dan's 310 ishh whp car (on a Mustang Dyno) is a pretty damn good achievment on stock restrictive head because it's somewhere near 60 or 65 % more whp over stock. Was it with methanol injection ?

Also, would that be possible to swap the spring in the fuel sender unit to gain a few PSI on the fuel line ...

Regards.

The GM Stage 3 PCM cannot raise the fuel PRESSURE (as it is set by a mechanical spring in the fuel sender unit) but could raise the flow. Why not someone with the GM Stage 3 logs the fuel pumps voltage under load ...

 

so with this return style setup does this simply optimize fuel output to gain a more reliable afr or does it actually add more fuel and increase power? This stuff is so over my noggin

 

that would be fan freakin tastic!!!!

this would give me the answer im looking for actually.

 

Didn't mean to butcher the quote too much but anyways...

No meth, just turbo and terrible fueling which was discovered later as a bad timing chain tensioner.

Can't swap the spring as its not actually a coil spring. If you look closely to the pic of the regulator I provided above its just a piece of stainless thats bent in such a way that it provides resistance against a ball bearing which acts as a valve.

Fuel pump voltage remains constant under all conditions.

 

is it possible that, once youve pullied down so much that the eaton makes boost faster than the fuel system can keep up, cause while in boost i run a 12:1 and if i mash it from lets say a 40 roll in 2nd gear, by the time i hit 15psi 17:1 blips on the screen then goes back to 12:1 all the way to redline

btw i have a 2.85 pully on 42.5 injectors

 

Hey guys, just want to give you some info. Go to gmtunersource.comgmtunersource.com Scroll down on the home page to the Stage 3 article. Open and read, What is the flow rate of the Stage injectors?? 42.5???

 

The reason is the crappy stock tune. Open loop mode (power enrichment) is only allowed to begin at 3600 RPM with the stock tune. So before 3600 RPM the PCM commands a AFR of 14.7, but the result for you is even leaner because of your mods. Then after 3600 RPM it spikes down to a rich (10ishh) AFR, still caused by another part of the crappy tune (you can see the weird voluntary spike in the injectors offset table).

OK let's resume the problem when running big injectors. We are stucked with a low differential pressure at high boost, but stucked with a very high differential pressure at low boost (vacuum). So the following might be a cheap suggestion. Instead of trying to raise the fuel rail pressure (at high intake manifold boost pressure) to be able to run smaller injectors, here is a simple solution. Will that work ...

1 : First of all calculate the injectors size with the hp goals and the differential pressure at max boost. Fuel rail pressure is 55-60 PSI, let's say then it is 58 PSI. And let's say we wanna boost 18 PSI in the intake manifold, so differential pressure is now only 40 PSI. It will probably end up to injectors like 50#, 55# or 63# injectors. This first step is not an improvement as we are still stucked with the low differential pressure. BUT ...

2 : Let's get the fuel pressure lowered at lower boost (vaccum) with a rising rate fuel pressure regulator (installed inline after the pump, but before the fuel rail), thus still using the stock returnless system. In short the rising rate "reads" the manifold boost (with a vaccuum hose) and adjust the fuel pressure. So it won't be used to raise the fuel pressure, but to get it lowered ! Max pressure would still be 58 PSI.

3 : Adujst the flow rate of the injectors constant (straight horizontal line) in HPTuners.

So the differential pressure (passing through the injectors) would be constant to 40 PSI in either vaccum, idle, high load, max boost ...

A question to Witt : Are you sure that the volts table that your talking about controls the injectors, cause what I see in HPTuners is that it controlls the BATTERY voltage vs injectors PW.

What are your thoughts ...

 

Its just a flow rate modifier as it states. You can have up to double your IFR values before you have to start skewing airflow tables. Multiplying the entire table by 1.3 would give you 30% more overhead on the IFR table. You can go as high as 2.0.