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post #1 of 18 (permalink) Old 12-04-2017, 01:47 AM Thread Starter
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Fuel pump pressure

on my GSXR 1000 i started to check Fuel Pump pressure with gouge and . Its 3 bar on idle , when just only increasing rev at 6000 or more rpm it dropes to 2.9 bar . Is it normal ?

After that i try to check pressure at runing bike and on high way i used 3rth gear for test and pressure was droppimg some time from 3 bar to 2.7 bar when fast using of trotthle .

I am using my bike for drags and speed , is it normal to drop from 3 bar to 2.7 when fast acceleration or not on runing , ?
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post #2 of 18 (permalink) Old 12-04-2017, 02:05 AM
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Re: Fuel pump pressure

As far as I know, it should stay at 3 bar. It sounds like the main filter is in the early stages of clogging. Time to do the flow test.

Is this still the K9? How are you hooked up to measure the pressure while riding?
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post #3 of 18 (permalink) Old 12-04-2017, 02:13 AM Thread Starter
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Ye i think also about 3 bar always but i am not sure mabe its normal drop 0.3 bar with fast acceleration , flow test was normal on idle of course i can not check on runing mode .

I used 3 fuel line + pressure gouge + 3 pin connector , guge line was long and i put gouge near my speedometer to see pressure while runing .

Yes it K9 gsxr 1000
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post #4 of 18 (permalink) Old 12-04-2017, 05:06 AM
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Re: Fuel pump pressure

Is the drop only transient, i.e. does the pressures only drop shortly, when you open the throttle, quickly rising back to ~3bar, or is it sustained during the whole period of acceleration? In other words, if you accelerate for 5" using full throttle, or thereabout in 3rd gear, (starting at sufficiently high engine speed, to substantially load the engine) will the fuel pressure be at 2.7bar during the whole period, or only for a second or so after you whack the throttle open? I'm asking to establish the nature of the pressure drop; please don't take this as a suggestion to perform that specific experiment. Hard, prolonged acceleration on the road, while looking at instrumentation, is not the best of ideas.

In any case, if the drop is only transient, it might well be natural, and be due to the time it takes for the pressure regulator to react. If it's sustained, it would suggest, that the pump can't meet the pressure specification, even though the regulator has fully opened. (But then again, the pressure specified in the manual, is specified at zero flow, so that last statement is not necessarily entirely accurate.)
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post #5 of 18 (permalink) Old 12-04-2017, 10:56 AM
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Re: Fuel pump pressure

What is result of your fuel flow test in ml?
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post #6 of 18 (permalink) Old 12-04-2017, 11:36 AM
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Re: Fuel pump pressure

"flow test was normal on idle" This doesn't make sense. The flow test is done with the fuel line disconnected from the engine. See the service manual.

Another possibility is that the pressure drop isn't real but is due to the weight of the fuel in the line to the gauge as you accelerate. It's a water hammer type of effect. If so, the pressure drop should go away if you re-position the gauge further back. I realize that it won't be nearly as easy to check then.
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post #7 of 18 (permalink) Old 12-04-2017, 04:11 PM Thread Starter
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In fast acceleration it goes 2.7 bar for 2 or 3 sec then coming to 2.9 bar - 3bar .

I tested flow without lines and in 2 time start fuel pump 200ml time for 1 open was 3.8sec that means that 7.4sec flow was 200ml when in manual 220ml for 10sec

Anyway i am going ro replace fuel pump but i dont know it would be same 2016 fuel pump like mine 2009 year ? Becouse i found 2016 pump with low miles on it
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post #8 of 18 (permalink) Old 12-04-2017, 06:57 PM
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Re: Fuel pump pressure

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Originally Posted by Antonio_beqa View Post
In fast acceleration it goes 2.7 bar for 2 or 3 sec then coming to 2.9 bar - 3bar .

I tested flow without lines and in 2 time start fuel pump 200ml time for 1 open was 3.8sec that means that 7.4sec flow was 200ml when in manual 220ml for 10sec

Anyway i am going ro replace fuel pump but i dont know it would be same 2016 fuel pump like mine 2009 year ? Becouse i found 2016 pump with low miles on it
Does the manual say to hit the prime button and extrapolate data, or does it say to connect a 12v source for 10 seconds and measure the flow? Because I'm 100% positive it doesn't say the former, and you doing what you did entirely defeats the purpose of doing the flow test in the first place.

Go do the fuel flow test the right way, then report back.
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post #9 of 18 (permalink) Old 12-04-2017, 11:06 PM Thread Starter
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Oh nick you are right i will do the properlly test today , and i will write results

Anyway if anyone can say is 2016 year pump same as 2009 year ? To replace with it ?
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post #10 of 18 (permalink) Old 12-05-2017, 05:38 PM
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Re: Fuel pump pressure

^It probably is but you need to check that out by comparing the K9 and L6 parts fiches. Oftentimes the pump assembly PN is different because the level sensor or its mount is different but the actual pump is the same. The PNs provide a lot of insight on such matters.
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post #11 of 18 (permalink) Old 12-06-2017, 02:19 PM Thread Starter
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So i did test , took 12v from battery woth wores like in manual and result was 390ml in 10Sec

In manual its written 220ml in 10 sec why mine is doing so much ?

After that i tested another motorcycle like kawa 636 and it does 370 ml in 10sec ))
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post #12 of 18 (permalink) Old 12-06-2017, 05:16 PM
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Re: Fuel pump pressure

The 220 ml spec is a minimum. They flow more if in good condition.

I continue to suspect that the pressure variations that you're seeing are due to motion induced surging in the line. A dyno run would tell for sure. Alternately get a solid state pressure sensor that you can mount at the pump.
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post #13 of 18 (permalink) Old 12-06-2017, 09:19 PM
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Re: Fuel pump pressure

Quote:
Originally Posted by Antonio_beqa View Post
So i did test , took 12v from battery woth wores like in manual and result was 390ml in 10Sec

In manual its written 220ml in 10 sec why mine is doing so much ?

After that i tested another motorcycle like kawa 636 and it does 370 ml in 10sec ))
If you do a calculation based on your extrapolated data, look at the fuel flow difference: converting that to 10 seconds would indicate only 263ml, while you got 50% more than that when you ran the actual test. This makes a big difference, and shows your pump is flowing just fine.
Remember that 220ml is a bare minimum, and you want it to be higher. But if it's too high, you need to verify that the fuel pressure is controlled, which you already saw was at 43 PSI as you wanted to be.

So, what issues are you having that made you test this? Have you put it on a dyno to see if you notice fluctuations in the AFR? I would not be all that concerned if you have no issues and the AFR is still safe.

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post #14 of 18 (permalink) Old 12-07-2017, 06:57 AM Thread Starter
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I was just testing no issue )) for interest
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post #15 of 18 (permalink) Old 12-07-2017, 10:48 AM
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Re: Fuel pump pressure

Quote:
Originally Posted by Antonio_beqa View Post
I was just testing no issue )) for interest
Well, in that case, there's no reason to worry. Like I said, you can throw it on a dyno for safe measure to view the AFR, but it's not like you need to do anything unless you're getting a lean spike.
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post #16 of 18 (permalink) Old 12-07-2017, 11:18 AM
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Re: Fuel pump pressure

Don't worry about it. Your flow and pressures are fine. The reason you see a drop initially is because of the delay between sensor, ECU, and signal to the pump. If you slowly put power on, then you probably wouldn't see a drop. The pressure drop is because of Bernoulli's principle. The sudden flow of fuel drops the pressure until the pump responds and THEN the pump has to not only increase flow to keep up, but must replace the volume of fuel in the line that it lost due to the lag.

TL;DR- Increase flow=decreased pressure until the pump adjusts.

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post #17 of 18 (permalink) Old 12-07-2017, 08:23 PM
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Re: Fuel pump pressure

I installed an on board fuel pressure gauge while I was trouble shooting my K2's drop in power above 1/2 throttle, and it was totally die'ing @ WOT.

At half throttle the fuel pressure was dropping from 43psi down to around 35psi (where you could start to feel the power loss slightly), and at WOT it was dropping all the way down to 20psi where it would totally die, close the throttle and the fuel pressure would recover back to 43psi within less than 2 seconds.

Long story short... clogged HP fuel filter (400mls per 30 seconds, should be 1200ml per 30 second) I bypassed the OEM HP fuel filter, with external HP fuel filter, retested with original OEM fuel pump, flow test very close to 1200ml per 30 seconds, bike back to full power...

I have retained my on board fuel pressure gauge with my external HP fuel filter setup, and the bikeís running awesome / normal again.


This is what I have seen...

Cruising around bike maintains 43psi no problem.

While @ WOT in any gear, fuel pressure drops slightly to around (41psi to 42psi) and maintains this figure the whole time @ WOT. Never goes any lower.

Only on initial fast cracking of WOT, fuel pressure quickly dips to about 40psi, then quickly recovers back to around (41psi to 42 psi)...

The OEM setup has the fuel pressure regulator Downstream of the HP fuel filter. (This is a good thing, as it compensates as much as it can as the HP filter slowly clogís over time, until it canít compensate enough anymore. Also it compensates if there is any pressure drop from the filter inlet to the filter outlet.)

My external HP fuel filter setup has the OEM fuel pressure regulator Upstream of my external HP fuel filter. (Only way it can be done, unless you run an external aftermarket fuel pressure reg.)

It would be great to test a brand new (OEM Fuel pump / filter assembly), to see if there is any variation in the fuel pressure, while maintaining WOT...

But... Iím not going to fork out $800US for a new OEM fuel pump / filter assembly to find out...........


The best spot for the fuel pressure regulator, would be at the end of the fuel rail, after the last injector, for the best control.

I have a Nissan SR20DET turbo, and this is the exact location of the OEM Nissan fuel pressure regulator from the factory.


Here's my On Board Mechanical fuel pressure gauge...

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post #18 of 18 (permalink) Old 12-07-2017, 09:13 PM
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Re: Fuel pump pressure

That liquid fill will dampen any brief surges. There are also issues related to any orifices that might be in the gauge or the line to it. As I understand it, the pump runs at full blast all the time and any excess fuel gets dumped through the pressure regulator. So recovery due to a sudden increase in demand for fuel should be very fast - as fast as it takes the regulator's poppet to adjust. I'd generally expect to see just what you do. The slightly lower pressure during times of higher demand is associated with less fuel being pushed through the regulator, i.e. single stage regulators aren't perfect. Mounting the regulator at the end of the rail might help a bit, but it would require an extra line back to the tank and that's unnecessary complexity on a bike.

P.S. I realized that the effect on the gauge pressure due to the bike's acceleration can be calculated. A 0-60 time of 2.5 sec translates into a maximum acceleration rate of around 1.1 G. Gas weighs about 6 lb/gal and the horizontal distance for the line from the pump to the gauge is 2 ft at most. All that translates into a head loss of .7 psi. So it's there but it isn't much.

Last edited by BillV; 12-08-2017 at 11:30 AM. Reason: Added P.S.
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