Fuel pump issues

[Commuta_Busa]

So here's another result I had from the last Maxton event I thought I would share with everyone. It seems I may have to look for a new fuel pump. I've been running the same pump for many years now. This might be a good time to try a bosch 044 to see how well it runs in my fuel system.

The first graph is a graph I always plot for fuel pressure and oil just to see at a glance if there are any major issues going on with fluid pickup. If during accelaration there's a drop in either it could indicate that the pickup is not completely submerged/covered.

In the second graph I look at the pressure and include the throttle position. This tells me how hard the fuel system is working. You can see that once I go to full throttle there's a drop in pressure.

I also check fuel pressure vs voltage to see if a drop in pressure may be caused by a drop in voltage to the pumps. That one checks out fine with the new electrical system.

Before things get worse with this pump I'll swap in a different one to see if this goes away.

 

[Thyg0d]

Impressive charts!! What sw do you use??
Is it the stock pump or an upgrade??

 

[Commuta_Busa]

I just did the charts real quick in excel from my datalog data.
Yes, it's an aftermarket Walbro pump. It's a good pump it just may be getting tired after so many years.

 

[Thyg0d]

What datalogger are you using?
External pump I guess??
Probably going to need one since in a somewhat near futurer since mine is 11 yrs and they're known to loose pressure when they get hot..

What datalogger are you using? It's always nice to find out things before you sit there with a camshaft or other internal part up your ass...

 

[Commuta_Busa]

I use the AimSports MXL datalogger system. Yes it's an external pump. I had tried their internal pump but it was heating the fuel to much. I agree it's always good to stay on top of things. Hot pumps never last long. There are always some things you can watch out for while other things just happen. I hate finding a failure point after the fact.

 

[Thyg0d]

Talk about it...
Right now I'm waiting for a ported & fixed head since the intake valves on the 1st cylinder decided to eat them selves (sp?) into the head and leak like freaking crazy..
But when something like that happens I just replace it all, including injectors, Tb's vaccumlines, anything that can have anything to do with it.. Kinda like "spray and pray" machineguns..

Got a Walbro pump in the T-bird.. has worked for five yrs so far..

What about the alternator.. Does it keep up with the fuelpump?? Just so you don't find yourself stranded on the road with a dead battery...

 

[Commuta_Busa]

I'm running a total loss system. My battery voltage has very little fluctuation in it. Not enough to to drop fuel pressure. In the past I didn have that issue at full song for long durations. I had wired to batteries together to take up the slack that the stator couldn't handle.

 

[Draco1340]

Ken,
Great use of logging. Couple of questions. What does a 2.5 psi drop in pressure correlate to flow. If it consistently drops to 40 psi and you are tuned for that, is that OK? When my pump started to fail, the pressure would continue to drop going into 3rd, then 4th, then 5th gear. It couldn't keep up. Yours looks more like a base line shift. That might actually be caused by the regulator.

Secondly, when you measured voltage drop did you measure it right at the posts of the pump? Even if the battery doesn't fluctuate (much) the line loss at 10+ amps or so could be significant.

Finally, Is that a Walbro 255?

 

[Commuta_Busa]

Draco - good observations I may have to dig into all of this further. I haven't looked at the flow rate since I would have to calculate the number. I used to run a higher pressure which also had a pressure drop during runs so I lowered the pressure and just changed my fuel map to compensate. With the current setup the pressure does consistently drop on every run so I do tune for this as well but I would prefer more consistent pressure. do you think the regulator may be causing a flow restriction? I've got x1 -8 line from the tank & pump to the rail, from the rail there are x2 -6 lines to the regulator but only x1 -6 line back to the tank. Maybe I should swap the -6 return line from the reg to the tank with a -8 and measure for changes?

As for the electrical side of things, I've upped the wire awg on the pump. It has a direct connection to the battery through a relay and the pump ground is shared with the battery. I measured voltage at the battery and the pump. Everything checks out on that end. There is a small variance but they run parallel to each other. When I rewired everything I could have gone bigger but I didn't think it was necessary. I might revisit this as well to see if i can decrease the variance some more.

Yes, this is the 255 pump. How do your logs look with fuel pressure? Have you measured flow on your system? How did the calculation look?

 

[Draco1340]

I've got x1 -8 line from the tank & pump to the rail, from the rail there are x2 -6 lines to the regulator but only x1 -6 line back to the tank. Maybe I should swap the -6 return line from the reg to the tank with a -8 and measure for changes?

Yes, this is the 255 pump. How do your logs look with fuel pressure? Have you measured flow on your system? How did the calculation look?

The smaller return line from the regulator wouldn't cause you to drop pressure under load, but I suppose could cause your static pressure to be a bit high. Different cause - same result. For what its worth, my lines are all -8. Changing one line is cheaper than a $200 pump.

I stopped logging FP after I switched to the Walbro 255. I was only logging FP to diagnose the problem I was having with multiple OEM Pumps. They are all crap for any application over 220 HP. MY A/F right now is a perfect 12.0 to 12.2 in all gears (using ECU Editor), and my injectors arn't close to being maxed, so my dynamic pump pressure isn't really a concearn.

My (arguably worthless) opinion is that a 2 psi drop in pressure isn't a big deal as long as its consistent, and is part of your tune.

 

[Thyg0d]

Sorry for not contributing to the discussion but where do I get my hands on a datalogger? Compatible with a 99...

 

[Commuta_Busa]

Draco - I value your opinion and others as well. Two heads are better than one. I agree the 2psi drop isn't a big deal. If it were a bigger drop I would have some concerns. I just gets nuts sometimes trying to eliminate variables. I'm a bit curious to see if swapping the single return line to the tank with a -8 to see if it has any effect. I've got plenty of line and fittings so there isn't any costs involved. Swapping pumps would allow me to compare one against the other.

Thygod - there are lots of loggers on the market. There are plenty of standalone systems that can be installed on any bike. It all depends on what your needs are and what kind of budget you have.

 

[Thyg0d]

Thygod - there are lots of loggers on the market. There are plenty of standalone systems that can be installed on any bike. It all depends on what your needs are and what kind of budget you have.

Well, since I'm more or less a streetguy it hasn't got to be anything that advanced.. I'm more interested in catching a malfunction before it happens.. I.e. checking the logg after a hard day in the twisties to see if the oilpressure dropped, 'cause it's sucking air, changes in the fuelpressure due to f*cked up filter, if the injectors touch 100% dutycycle, stuff like that..
The reason is 'cause I've already trashed an engine on my gixxer and the head on the busa..
The gixxer was easy, tech that put the cam chain wrong, valve said to the vavle..
The Busa however is worse.. Can't find any reason for the valves to chew into the top..

 

[bobber]

thygd
what caused the busa head /motor failure? how old is the bike and how many miles ect,,what do you think happened ? what yr bike?
Commuta,,,,A OEM pump should handle a PC with an average demand of 3 ,5 ,7 % xtra fuel in the cells in the custom map correct? and I feed it 16% more fuel at 7000 rpm only at WOT only to compensate for a 40 shot Nos,,,,,Factory motor,,but drac mentioned about anything over 220 hp will affect the pumps ability to keep up,,,I assume he was factoring in internal mods,which I dont have,,,Is this correct fellas,,,,the nos isnt constantly used,,its a street cruser,,,

 

[Commuta_Busa]

The 220hp mark is a good rule of thumb with the OE busa pump. If you're hp goes above this area the pumps start running into problems with the consistancy of the fuel delivery.

 

[bobber]

So in your opinion,,,,,a stock motor,,,PC with added fuel 3% -5% thru out the custom map,,but then starting at 5500-6500 rpm {only at 100% full throttle postion} 7% is added,,, and then 16% added fuel at 7000 on up,,
DO you think then OEM pump can handle this,,I wasnt too concerned about the 3-5% and my gut tells me that 16 is getting there,,but I dont run the bike hard,,,and just wanted to know your opinion and others,,,ussually when your street rideing,,,you dont have it up past 7K very long or often anyway,,

 

[Commuta_Busa]

16% addded in fuel compensation to your map shouldn't be a problem at all. Of course, IMO.

 

[bobber]

thanks communta
peace of mind,,I didnt think it would matter ,But it pays to ask,,,,,after builds of bigger cams and pistins with head work}cars only] Ive seen upgrade on f/pumps then,,,,, Taken into consideration with a busa,,you would think suzuki OE pump would be High Volume out put anyway,,and you should be safe to sneak in a PC will alittle xtra fuel,,,,
It would be nice to have a #2 busa to build for the track,,,,but one,,im older than dirt,,and dont have deep pockets ,#2 I enjoy the ride and stable ,dependability of the factury bike,,,and #3 Ive seen the more horsepower i used to strap on my cars and raced,,you pay to play,,,some were money pits ,,But I built a few,,that were blessed by God and they took alot of race abuse,,,But I couldnt exscape buying quite a few clutchs and pressure plates either in those days,,,,,,,but they were welcomed,,when a twin 4 barrel bigblock held together for yrs without a rebuild,,only minor stuff broke,,,
Do you think suzuki makes a 4barrel intake for the busa that would hold a 1050 cfm Holley Dominator ? thanks commuta

 

[Commuta_Busa]

I hear ya! except the ol' holley. I'm so glad to be able to play with FI systems now.

 

[Thyg0d]

thygd
what caused the busa head /motor failure? how old is the bike and how many miles ect,,what do you think happened ? what yr bike?

It's a 99 with 25k miles on it..
From what I've been told the 99-03 heads are a bit to soft in the valveseats..
The other problem with the 99-03 heads are that they are thinner so they can't be milled again.. Or what it's called.. 'cause it you do you won't be able to shim in the valve because it sticks up to much...

Combine the soft valveseats with 11 year old valvesprings and a high rpm motor and you end up with valves floating trashing the head...
That's my guess..
Another factor could be that I've had a PCII on it which aren't the best since they fool the ECU... instead of actually mapping it per rpm and throttle position.. That could have created a lean out somewhere in the rpm range..
The reason for that guess is that the number one cylinder exhaust port is white while the other 3 are black..
Could also be an injector that's dirty or malfunctioning so I'm replacing those as well..