When is a twin pump needed?
 

I would like to know at what whp is it needed to have a twin pump? If my goals are around 550-600whp then can I get away with a single walbro or are twins a must?

Depends in the dyno. At 550whp on our dyno we can start seeing some slight pressure fluctuations at high rpm. If you are talking 600whp on a dynojet then a single pump will get you by. You will be near it's limits for sustained use.

sorry for newbie question, but seeing pressure fluctuation at higher rpms can cause damage?

^^ Of course it can because changing pressure = changing/uncontrollable AFR

i c. So I shouldnt push it more than 550whp on DD.

I've run into issues before that. You need to log fuel pressure as you tune. I found that I could keep adding injector pulse width at high rpms above 16 psi and 6000 rpms and could not get the AFR to come down. Took a quick look at my fuel pressure gauge and saw that it dipped down to 28 psi. Oops. I'm currently looking at going from a CJM stage 1 to stage 2 (thanks cersoft and phunk!). But I then realized I already had a Ken Bell boost-a-spark unit that wasn't doing anything in my car so I converted it to a boost-a-pump and voila I now have 16.5V pushing my walbro above 4 psi. It seems to be doing the trick.

Time to go back to the dyno... (the most I got out of my car on the dyno was 53x whp on a DJ before I ran out of fuel with my 1000 cc HKS injectors - 5AT and drivetrain losses are higher so maybe that's the same as 550-570 for a 6MT).

I ran out of fuel on injected's dyno at 451hp with my vortech. I had a cjm return fuel and walbro. fuel pressure would bottom out at 7700.

Hal said on his dyno for a turbo'ed car he would see a single walbro on a return system start letting go around 530hp.

I went with a cjm stage 3 twin pump because my goals are on the line for pump gas which means i'll no doubt need the twin pump for my e85 tune. i also decided against running meth and wanted to do it all on straight fuel to simplify the car.

You're in luck with the cjm stage 3. I am the first to have a full stage 3 kit on a g35 therefore all the kinks with measurements on the new lines was worked out. Since i'm battling midterms and still working on finishing all my new build i haven't posted the pics and install instructions that are slightly different for a g35 yet. Now that it's all worked out it should install fast and easy.

thanks for the info guys.

what does stage 3 consist of?

Boost-a-pump LOL what a novel idea.

A SC car will require more fuel at same rwhp than a turbo car (SC has more parasidic loss).

And what you can make on the dyno is not necessarily "safely driveable". If you want to crack into the 600rwhp twin is needed (or additional fuel pumping, however you want to handle it).

Tom

What cjm lists on their site for a stage 2 plus the twin pump and an aeromotive inline filter.

so basically fuel rails, boost reference FPR, 1/2" hard line into an 8an to the back of the fuel rails, 6an return line, 2 6an feed lines into an 8an to the inline filter.

you will need relays and some wire. it is recommended to run a 10 gauge wire to the relays for power and only use the stock wiring to trip the relays. It says you need a bosch 5 pin relay for each fuel pump (2) but since they are 40amp i used just 1 relay for both my pumps and it works just fine. Each pump is fused with a 15amp fuse so that relay will never see more than 30 amps anyways.

this is the truth straight from a man doing 650 on pump. 500 on a single walbro should be ok, i personally wouldn't run anymore then that with just pumpgas if you want to be safe and have your stuff last. You'll also be setup perfectly for e85 later if you ever choose to switch.

Size of your injectors would obviously also change the max power you can "safely" run on a single pump.

I do'nt see how that would influence it if the injector size is already greater than the pump can put out. If the pump runs out and fuel pressure dives an injector change won't help the problem.

I'm actually running the vortech inline pump + the walbro intank with the aam return line so I think I'm good for at least 550whp on DD. I was thinking about ditching the inline for the double pump but it doesn't seem cost affective to do this upgrade and not use it's potential when my goal isn't that high.

^^ what's funny is the triple pump hanger is cheaper than the twin pump one which is :werd:

if i was going to risk using an inline pump it would be no less than a bosch 044. Also, what size are your supply lines? If you are still using the stock 5/16 hard line as a supply line you will be restricted on flow which can affect the amount of power you get. Remember, flow is different than pressure. The pressure will be ok (because small lines) but the flowrate will be significantly reduced with the oem lines.

So in addition to using an 044 pump i would also get the upgraded supply lines from cjm at a minimum. Since you have rails and all that you just need the hardpipe and the 8an to connect to the rails. Charles will sell the pieces separately and that will keep your flow up.

Also, another bad fact to throw out there. I dont trust the walbro inline pumps. I had one, got rid of it as soon as i could. If that inline pump fails when you are hard in it then by by motor. Granted, there is a possibility that a single pump "could" fail in a twin pump intank setup but it just seems less likely. For certain i would wire both your in tank walbro and your inline pump on the same fuse therefore if one of them blows a fuse it takes out the whole fuel system so the car will just die and not starve for fuel and blow the engine.

I know where your head is. I was pondering the inline pump too because my setup will be right on the line for a single pump on pumpgas but i decided that the money in my built block, heads, turbo system was worth spending the extra cash. I wouldn't recover from destroying all of that in one fellow swoop because of a cheap inline fuel pump. but that's just me :werd:

ya i'm not sure about the hard lines but I do know that the AAM lines are all ss and the inline pump is connected to a relay connected to the vpro so if it does fail it tells it to go into limp mode.

I want to get rid of the inline pump bc of the same reason u mentioned but the twins seem a little too complex for my setup and not too friendly on the wallet.

triple pump doesn't include wiring, any fuel lines, or any pumps. Twin pump comes with all of that and already assembled. Look at the triple hanger cost with 3 walbros. It's 100$ more expensive and still doesn't include the plumming or wiring. Both are great pieces though and worth the cash.

Well hardlines is simple, did you or did you not remove the OEM hardline in the car? I actually know the answer because aam uses the oem 5/16" hardline which is way small. just over 1/4" so the cjm hardline is double the size. So that would be a good restriction on your lines. With larger lines you will have less restriction and then you can get more out of your single pump setup.

too complex? it's a drop in fuel pump assembly. definitely not too complex for a full built engine and turbo setup. Granted it is expensive but you won't have to buy the whole stage 3 since you have rails and return lines already. charles will only charge you for what you need.

Either way i strongly recommend upgrading the stock hardpipe to the cjm 1/2" to increase the flow of your single pump setup.

I took a long hard look at my build and after looking at all the money i have into the engine and mods it wasn't even an option to skimp on it. I took a hit on the cost but at the same time there is no way i would recover financially from blowing this engine. There would be no rebuild if that happened.

i'm iffy when it comes to the electric part for the twin pumps :(

I think to be on the safe side, ill get the fuel pressure sensor for the camp2 so at least i can monitor it and have it signal me if it senses low pressure.