YelloEye

iTrader: (3)

Hah, that's an in tank solution, you'd have to design your fuel cell around how that in tank one mounts. Are you wanting to run in tank or inline? There's plenty of cheap inline options that flow what you're looking for.

This says it'll do 215lph for $115.
Precision Fuel Pumps E16118 - Fuel Pump | O'Reilly Auto Parts

patooyee

I prefer in-tank to keep the pump cool. I have a solution but it isn't as cheap as the free stock sending unit would have been. At the time I was tearing everything out I assumed the stock fuel pump would not work with boost.

YelloEye

iTrader: (3)

I turboed one of the 2.4 LE5's with a friend, we didn't change out the fuel pump. Assuming you're not running some crazy amount of boost the stock pump would be fine. You could always see what you can find at junk yards.

patooyee

I think my biggest issue using a stock sending unit would be the funky tabs that hold it in / making something similar out of aluminum that I could weld into my custom fuel cell.

This is a sending unit made by Walbro that is the same except uses a clamp-ring on top that bolts in place. So it's much easier to put in a custom cell. But I like using things that are available at auto parts stores more. That way if I break down on the trail I just get a ride back to the truck, run to town, grab another one, and continue on with my weekend.



This is my plan if I can't figure out how to make a stock unit work at this point ...

Slowbalt2000

iTrader: (1)

Get at least a 255. I wouldnt use a stock pump for your application.

Slowbalt2000

iTrader: (1)

Hell, wally 450s are $100 on ebay and so are aem 320s

patooyee

That sender unit that I posted a pic of comes with a 255 in it. They also sell one with a 190 in it. You get all that for less than $200.

More isn't always better. If you're not using all the fuel your pump is pumping you're just generating needless heat and wasting energy. Hot fuel is more susceptible to vaporization. At the fuel pickup in the tank there is actually a low pressure / vacuum state. You can boil fuel at room temperature under low enough pressure. Lots of people have heat-induced flash-vapor issues in their fuel systems that they fight constantly. They always think that the rail is absorbing heat. But the real culprit is in the tank at the pickup were there is low or negative pressure and the fuel is most susceptible to vaporizing. Having a massive fuel pump there generating needless heat doesn't help.

There's a few fuel pump calculators out there. Right now I'm calculating that I need about 170lph. Obviously you do want a bit more than that to account for efficiency, etc. The Walbro 190 would seem like a great candidate. But if the stock pump is 225lph I was thinking that it should work fine with the added benefit of being on the shelf. I'm going to keep looking into what it would take to make it work though. I don't need to decide any time soon.

Slowbalt2000

iTrader: (1)

I honestly dont think the stock pump is enough to make 350hp. Just my 2˘, but wouldnt a bigger pump generate less heat because it doesnt have to work as hard to flow the same amount of fuel? I just put a wally 450 in my cobalt.

Sharkey

iTrader: (1)

with something like a rock buggy i would be considering doing something a little different with the fuel system. id be building a surge tank setup and using a lift pump and a main pump. if your on a steep incline, even with a baffled tank, its possible for the pickup to get uncovered. not only can this cause a lean condition, if it bogs it could stall, and on a steep angle it could end up in a bad situation.

patooyee

In a bypass / return system, which these cars are, the pump will flow max volume no matter what. Whatever the engine doesn't use just gets returned to tank. So there isn't a time where it's working less to flow the same amount of fuel. A larger pump will always be flowing more fuel than a smaller pump. A larger pump also has to be able to pick up more fluid. The same amount of restriction will result in a grater vacuum at the pickup on a larger pump and therefore a higher chance of vapor lock.

This has been a huge topic of discussion and experimentation for a lot of us as it is a constant thorn in our sides. A few high end racers run a dual pump system like you describe but the vast majority (including me) are unwilling to devote the time, space, and complexity to that. We have tried multiple Walbro snowmobile pickups in the tank with mixed success. I've done in-tank trap-door surge tanks with decent success as well. (They're kind of noisy.) But no one seems to be able to beat an OEM sending unit. It has a surge tank built into it along with a venturi scavenger pump that seems to just flat-out work. The issue in the past has been the lack of high performance pumps built into those sending units but the Walbro one that I posted above resolves that for the first time. But this is also the first time that I haven't needed a high performance pump.

YelloEye

iTrader: (3)

Actually in stock configuration the Cobalts are return-less fuel systems.

Slowbalt2000

iTrader: (1)

the fuel returns from the filter back to the tank

patooyee

Yup. The filter is a pressure regulator and returns excess fuel back to the surge tank inside the sending unit.

Slowbalt2000

iTrader: (1)

Well technically the pressure regulator is on the canister on the return side inside the tank. I just removed mine for a boost referenced system.

patooyee

Oh, is there a separate filter? On the V8's the regulator is built into the filter. Can't replace one without the other.

Anyway, it should look something like this, correct?

Slowbalt2000

iTrader: (1)

Kinda, not exactly

Slowbalt2000

iTrader: (1)

On our cars there is a filter on the canister and there is one outside the tank as well.

patooyee

Meh, there may be on the trucks as well. I wouldn't know as all I've ever done with them is rip the engines out and put them in buggies.

Nevertheless, we have firmly established that the fuel system is a return-style system.

Slowbalt2000

iTrader: (1)

when you say return style, most think of running the fuel all the way to the rail, through an aftermarket regulator, and then all the way back to the tank. I just installed one of those systems on my car

patooyee

Oh. Sorry for the confusion.

Sharkey

iTrader: (1)

the correct term would be a dead headed fuel system. yes fuel is fed to the filter and back to the tank, but fuel is dead headed at the rail.

patooyee

Yes, deadhead would be the correct term I guess.

I'm a fan of neither, really. I understand why some don't like dead-heading. But flow-through takes the heat from the engine and brings it back to the tank where vaporization is most likely to occur. It also means that there is a low pressure return line running the length of the vehicle which makes it more likely to run close to hot things, like exhaust. As already discussed, low pressure = more likely to vaporize. I've ran both in the past, had heat issues with both to be honest.

This rig is going to be very small and centralized. The engine will be in the middle and I have an idea of how I may put at least part of the fuel cell underneath the engine. If that works out my fuel lines will only be about 2 feet long and ont run anywhere near anything hot. Time will tell ...

YelloEye

iTrader: (3)

Doh. I forgot about the external filter return, thanks for the correction guys. I should have remembered that from when I did a filter on my LT, had to find the right one that had the correct pressure regulator in it.

patooyee

Since I'm stuck at work and can't play for a while I decided to start going through the wiring schematics to ultimately cut my harness down. Just to help myself mentally organize I make a spreadsheet with each wire going to the ECM & TCM, it's original function, it's new function, wire color, and circuit number. I've got almost everything worked out but have one question, hoping someone might know something.

Both the ECM and TCM have an accessory power wire coming into it from the BCM but no obvious output. This is new to me as none of the V8's I have worked with had that. That means that both modules use accessory power as some sort of internal logic test to determine some other less obvious output function. Since my rig will not have "accessories" I know that something new needs to happen with this circuit. It either needs to go to ignition power or be left out completely. Does anyone know why the ECM & TCM need to know when the key is in accessory power position?

patooyee

Could this just be retained accessory power? (RAP)