Checking Fuel Pump on dyno

[Black33]

Hey all.

when dynoing a car - is it easy to tell if the fuel pump is getting close to reaching its limit?

How would this be done, can a pressure gauge be hooked up to the fuel system to see if the correct pressure is still being supplied??

Will tuning a car using a pump at the top end of it's flow rate mean it is more likely to fail? ie. tuning an r33 gtst stock pump to 190rwkw, if it can supply enough fuel on the dyno, then is this ok or does it mean that because this is getting to it's power limit, it will die sooner?

I would think that this isn't the case seeing as how if your pump is able to supply enough fuel at your peak power, it doesn't really spend much time flowing at that rate in street driving, only for WOT blasts every now and then.

What do u all think??

[4 Doorz]

You can easily tell as the A/F ratios will lean out on the dyno read - it may be sitting on 12:1 all the way to 6000rpm where it leans to 13:1 which I guess isn't ideal

[Black33]

yeah I know that - but I wanted to know if it is bad to push a pump to its limits, does this mean it is more likely to fail.

example: say an r33 gtst fuel pump has a power limit of 200rwkw before it starts leaning out. I tune my car to 195rwkw meaning that at peak power the pump is running at 97.5% of its capacity. Is this bad?

Does this mean it will fail sooner or is it not really a problem seeing as how in reality the pump will only be flowing at this rate very infrequently (not for track use)????

[RBVS]

hard to say, if its flowing at its limit then it prob would be a high chance of stuffing up but i dont think you could push it past its limit and kill it. if your not looking for power past its limit then i wouldnt worry about running it at its limit.

but with a bad AR you'll kill your engine and the price of a gtr pump would be well worth it, pluss give a hp gain with tune.

[GTS-t VSPEC]

I reccomend adding an external pump, and using your standard pump as a lifter pump. That way you will have more than adequate fuel for 400+rwhp, and no messing about in the tank:D

[Black33]

if i'm gonna get a pump i'll get a gtr one, but wanted to know if it's dodgy to push my stock pump a bit further

[GTS-t VSPEC]

Why bother with a GTR pump? The don't flow that much, and 2nd hand there not as reliable as buying a brand new BOSCH one. I pushed my stock GTS-t pump to 297rwhp, and it's still going, although only acting as a lifter.

[Revhead]

As long as there's still fuel coming back down the return line you won't blow up your fuel pump. Well it could die of other causes, but you know what I mean In an EFI system, the fuel pump just, well, pumps, and the fuel pressure regulator allows fuel to exit the rail to keep fuel in the rail at a given pressure.

If your pump can't supply enough fuel at high loads to keep the rail at the right pressure, you need a bigger one. I don't think it does the pump any good in this situation either, they're designed to pump into pressure, maybe someone with a bit more mechanical knowledge can verify?

[JimX]

The pump has a low and high stage of running. The low stage is for idle, and the rest of the time is at high speed. The biggest thing the pump has to fight against is fuel pressure. If you start maxing out the capacity of the pump, its job gets easier because the pressure gets less and it doesn't have to work as hard. So I would say hammering your car all over the place probably extends its life But not by any significant margin. It's more a case of how long it runs in total before it fails.

[Revhead]

Yep forgot to mention the half-voltage deal at idle - they run 6V to keep them quiet.

I like the idea of fangin it extending the life of at least one part of the car Dunno whether that's true though, the pump is actually designed to run against pressure, running it outside of specification couldn't do it any good surely? Without the pressure, maybe it can overspeed or the bearings or whatever ride in a different/wrong location? Anyone know for sure?

[JimX]

I guess that's possible, but as long as it didn't get starved of fuel (ie, run empty or over 100% of capacity) it should be ok.

[Sydneykid]

Hi Guys, we have used the std GTST pump as a lift pump from the tank to a surge tank. When you remove the pressure they easily flow enough to keep the 2 litre tank full, even with 2 X GTR pumps supplying the engine. I know they are rated at 135 litres per hour when used at 38 psi plus boost, say 50 psi, at 12 volts. When you take the 50 psi resistance away, and increase the voltage (by using a relay) to 13.8 volts, the flow is way over 200 litres per hour. I'll have to measure it one day, but it is more than enough for the 650 bhp which the 2 X GTR pumps supply to the injectors easily.

I have a few times plumbed a larger fuel pump into the hose between the fuel tank and the engine. So you have the std pump in the tank supplying fuel to the larger pump (in this case a Bosch 044) which is mounted under the boot floor. The 044 then feeds into the std hoses to the engine. The std pump in the tank has no resistance, so it flows enough to keep the 044 supplied with fuel. The 044 supplies the engine with enough fuel because of its higher rating, plus it is getting fuel supplied to it with no effort (it doesn't have to suck).

Some people prefer this method as it means you don't have to have a surge tank, in the boot usually. But it has a down side in that there is no surge protection, so when the main tank runs low the engine can starve for fuel with heavy cornering braking or accelerating.

As for dyno checking, we have a fuel pressure gauge which we plumb into the hose from the fuel filter to the fuel rail with a T piece. It only takes a few minutes to hook up. This shows the pressure in the fuel rail, if the pump is getting close to its capacity the fuel pressure drops. You can see the pressure start to drop way before the A/F ratios start to lean out.

Hope that adds to the thread.

[Revhead]

Thanks SK! Glad that's cleared up... I'd always wondered about running a fuel pump into zero pressure, looks like it doesn't cause any probs (actually a good thing). Sweet, I stand corrected

[Sydneykid]

Hi revhead, I haven't seen a real world scenario were you run absolutely ZERO resistance. Even pumping to a surge tank has a few psi, as it has to go through the pipe and upwards against gravity. Most pump manufacturers say that their pumps need some resistance to work against, but it has been my experience that only a tiny bit is required.

[TrevR32GTS-T]

Here a little fuel pump info:

GTS-T or -4 is 135 LPH

GT-R is 190 LHP

[Busky2k]

Yeah but LPH really means nothing unless you know the pressure too. A crappy pump could flow 200 LPH at zero resistance, and 20 at 60psi.

The best way to check is just to see how much fuel return your getting at WOT. Or, hook up a fuel pressure gauge, and make sure it stays consistant, and doesnt drop as the revs go higher.

[TrevR32GTS-T]

Going that way, he needs a fuel regualtor and guage to set resistance for a higher liter per hour pump. Also a fuel computer help to get a proper fuel to air ratio. Say power FC to e-manage to S-AFC.

[Black33]

thanks for the info guys, so if i tune my car to around 190 rwkw's and the A/F ratio's are looking ok and the pump is supplying enough fuel with enough pressure - then I assume all should be ok!!