I'll make this as short as I can. Built engine and supporting mods. Single walbro 255 and dual nozzle alky. car should be low 10, not there. 5mph short and injector duty cycle is 100% + going through traps. Alky pump is only putting out 120 psi engine off, 140 psi engine running using razor's tester. I've talked about this with Julio and he's telling me that pressure is enough. How can the instructions say "250 psi with water and 200 psi with alky on a healthy system" and 140 is enough? 50-60 psi is a BIG difference to me. This is with a 6 month old pump. Opinions and experiences please......
alky pressure....how low is too low?
- Thread starter trbojo
- Start date
- Joined
- Aug 1, 2003
on my 86 im running less than 135 tested key off - gain where i normally run at 5-6 , and around 145 WOT through duals , remember the logged pressure includes the running psi
as for your injectors at 100% , thats the commanded , whats your AF and whats your fuel pressure . is pressure holding 1-1 . you may have a delivery issue . ive run single walbros out past their limit at 85% with 50# inj and power just into the 10s on alky , fuel pumps go bad especially when pushed hard which is why they too need to be tested or replaced regularly like alky pumps
im running about 50lb hr per injector (and im a little rich) for the times in my sig (60%duty 83# injector ,twin walbro 340 (255lph) ATR dbl pumper at 43psi base) .........50s at 100% is 50lbhr
if your pressure holds 1-1 and you're injectors indicate you're using more fuel than should be for the hP id look into the fueling being too rich killing HP . also the a/f reading could show fine but actually be really low (rich) due to missing on at least one cylinder , ignition needs to be working 100% on all 6
as for your injectors at 100% , thats the commanded , whats your AF and whats your fuel pressure . is pressure holding 1-1 . you may have a delivery issue . ive run single walbros out past their limit at 85% with 50# inj and power just into the 10s on alky , fuel pumps go bad especially when pushed hard which is why they too need to be tested or replaced regularly like alky pumps
im running about 50lb hr per injector (and im a little rich) for the times in my sig (60%duty 83# injector ,twin walbro 340 (255lph) ATR dbl pumper at 43psi base) .........50s at 100% is 50lbhr
if your pressure holds 1-1 and you're injectors indicate you're using more fuel than should be for the hP id look into the fueling being too rich killing HP . also the a/f reading could show fine but actually be really low (rich) due to missing on at least one cylinder , ignition needs to be working 100% on all 6
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First of all you should be logging a lot more. I don't think you'll see much more than 150psi with a dual nozzle unless you use very small jets. Real world experience I just worked on a car that had an old non booted pump from at least 5 years ago. I noticed right away the injector duty cycle was higher than it should have been. So new pump went on it was fine up to 25psi. 131-132mph in 55* air. But at anything over that dc jumped to 100% with 10.5:1 target. Owner stated it had dual xp pumps. The pressure switch wires were cut. So I thought possibly that the XFI was controlling the second pump. Well it turns out someone that worked on the car didn't understand the dual pump and cut the leads off the pressure switch and ran the second pumps 12v lead directly to 12v. Then this ace likely couldn't figure out why the pump wouldn't turn off and pulled the blade fuse out of the holder! Big fail. The second pump was never on. Once fixed all was well. Expected dc was observed. We are looking for 9's next time out.
BPE2013@hotmail.com
BPE2013@hotmail.com
Bison.. Please take a look at my threads here and on Eric's board both with the same title "racetronix fuel pump issues?"... I'm chasing a fueling problem that's driving me insane at this point... 10+15 nozzles on my alky kit....
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You know what... I just thought of something... The tester i'm using only utilizes a single 15 nozzle and that's what I'm taking the pressure reading from.. I'm spraying with 2 nozzles... Wouldn't that drop my pressure even more?
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So if that's where you're at then I may have an issue... You say 5-6 on the gain.. I'm testing at 8 on the gain along with the initial bumped up from the factory setting.. I don't have a pressure logger and cannot afford to spend another dime on this thing until I figure out what's going on
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http://64.91.238.100/~turbotws/forum/index.php?threads/racetronix-fuel-pump-issues.2452/
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http://www.turbobuick.com/forums/index.php?threads/418644/
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With these types of issues Id be sure the fuel pump(s) are properly grounded and the alternator charging properly at wot/high load/rpm. Also be sure the feed line is in good shape. It's worth drilling the fittings out for reduced restriction. I often run a ground wire from the rear of the car to the engine block because I feel the fuel pump(s) are not adequately grounded. Then I verify the engine ground wire is in good shape. Without logging it's hard to know for sure what's really going on at WOT. You could flow test a fuel pump under controlled conditions but it won't fix any of the things I mentioned above unless al the testing was done on your car under the same conditions. Not going to happen at high load/rpm. All it will tell you is if the pumps are putting out what they should be based on the test. Most cars I work on usually have 2 or more things wrong that contribute to fueling issues.
BPE2013@hotmail.com
BPE2013@hotmail.com
- Joined
- Aug 1, 2003
the gain has very little effect on the alky pressure above 22psi boost, its more a control for the early boost up to 15 psi area and its limited there as well on how much can be trimmed out with the gain knob
.. once im at 23psi boost or so im all in as far as alky pressure rise and turning the gain up has no effect
and i'm only running two 10gph nozzles
The only way to get accurate data here is to use calibrated pressure transducers to determine the pressures you're dealing with. Get a 0-200 for the alky, 0-100 for the fuel system, and a good accurate AEM MAP sensor for the manifold pressure or another 0-100 pressure transducer. Then log all of them. You will get definite answers to is the alky pump output enough, is the fuel pump output enough through my lines, is my manifold pressure actually 26psi. All while under fully loaded operating conditions. I know on my cars 2-3psi increase in manifold pressure in 20-30 degree cooler air than I typically run in may raise injector dc 10% and that's with 72lb/hr injectors and 48psi base pressure. A smaller injector with lower pressure would increase quite a bit more. A good example of this I noticed before i ran at cecil in September was that 2 nights earlier we had a cool night where I logged inlet air temps of 57 degrees. Injector dc was about 4% higher than when I ran at cecil where I saw 75-80 degree inlet temps. This was at the same manifold pressure as the cool night 2 nights earlier. If boost were to be higher which it often is with cooler air I wouldn't be surprised to see a 10% jump in fuel consumption. I also log exhaust pressure and will say as the air gets a lot better the ex pressure increases a lot even at the same manifold pressure. Very definitive of increased mass flow and much higher fueling requirements. Also a new part doesn't necessarily mean it's a good part. I've had plenty of new stuff fail to perdo as it should
BPE2013@hotmail.com
I've noticed this also when using a 3 bar MAP sensor Paul. Switching to a 3.5 bar kept it more tapered.
BPE2013@hotmail.com
I appreciate all the help and info but again.. I need to figure out what's going on without throwing more money at this... I know fuel pressure is good under load.. Hood mounted gauge off end of rail... Boost.. Are you telling me the 3 bar that comes with the alky kit isn't Good enough? That's what's being used to log boost pressure.. And it compares the same to my vdo boost gauge... The million dollar question I'm trying to get an answer to is alky pressure ..I guess I'm just going to have to pull both nozzles out and tee the tester gauge in and see what pressure I'm getting with both nozzles spraying...
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I just told you everything I do so I can determine what is or isn't functioning as it should and also some safeguards/updates to the wiring and and fuel lines I often do. The answer to your million dollar question is quickly answered by following my last post. No need to throw more money at it. Turn the boost down where your dc is in check and enjoy the car.
BPE2013@hotmail.com
I think you are worrying about nothing with the alky pressure. 140-150psi is normal on a new pump. Verifying there are no leaks is just as important though as you can lose prime faster with even a small leak.
I think I tested 150psi or so on my new pump recently. I use Razors pressure tester and verify my pressure transducer that I log against it. If you are truly worried, then borrow or buy transducers to verify while under boost like Bison suggested.
As far as enough alky pressure, 150psi was good enough for me to go mid 9s so I am gonna go ahead and say you are good.
I think I tested 150psi or so on my new pump recently. I use Razors pressure tester and verify my pressure transducer that I log against it. If you are truly worried, then borrow or buy transducers to verify while under boost like Bison suggested.
As far as enough alky pressure, 150psi was good enough for me to go mid 9s so I am gonna go ahead and say you are good.
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Its even easier. The alky kit is to suppress knock. Not fuel the car. You get fueling as a second effect, but not the reason to use it.
So if the system makes lets use even a smaller number 80 psi.. and there is no knock, you have enough alcohol.
If the duty cycle goes through the roof.. and you have no knock.. then you have a fuel delivery issue. Pump, injector, pressure, etc..
99% of the time its fuel pump not keeping up or injectors too small for the given engine.
If you get knock and the air fuel is gliding up.. then your out of gas.
Now if you start getting knock and the air fuel is stable.. then you need more alcohol.
3 bar on the kit is perfectly fine. Just that when you crank the controls up it ramps the pressure up sooner and then doesnt really add much more pressure past the lower 20's. Still back to issue one.. knock. No knock.. you have plenty.
I also wonder what power(voltage) is at your fuse box when the tests are being performed. Your battery may be at 11.9 but the box could be way lower if there are a lot of drops. So when you run the tester put a meter on the red wire where it gets power from the fuse box and see what voltage you have when the system is making 100+ psi pressure. If your fuse box is at 11.0 your pump would technically be at 10.6-10.8 as there is drop across 12ft of pump wire. This would then explain lower readings. Be surprised to see actual voltage across the red/black pump wires "at the pump"
When we test pumps on the bench its done using washer fluid and a variable power supply going up to 14v. The pump must make in excess of 250 psi on an M15 nozzle or it doesnt go out. You go to meth, that drops pressure 20%. You drop voltage and that will then drop pressure further. Voltage will drop across any length of wires. That is what it is.
Maybe need to make a Hot Wire relay kit for the pump right from the battery to give it that little extra OOMPH
So if the system makes lets use even a smaller number 80 psi.. and there is no knock, you have enough alcohol.
If the duty cycle goes through the roof.. and you have no knock.. then you have a fuel delivery issue. Pump, injector, pressure, etc..
99% of the time its fuel pump not keeping up or injectors too small for the given engine.
If you get knock and the air fuel is gliding up.. then your out of gas.
Now if you start getting knock and the air fuel is stable.. then you need more alcohol.
3 bar on the kit is perfectly fine. Just that when you crank the controls up it ramps the pressure up sooner and then doesnt really add much more pressure past the lower 20's. Still back to issue one.. knock. No knock.. you have plenty.
I also wonder what power(voltage) is at your fuse box when the tests are being performed. Your battery may be at 11.9 but the box could be way lower if there are a lot of drops. So when you run the tester put a meter on the red wire where it gets power from the fuse box and see what voltage you have when the system is making 100+ psi pressure. If your fuse box is at 11.0 your pump would technically be at 10.6-10.8 as there is drop across 12ft of pump wire. This would then explain lower readings. Be surprised to see actual voltage across the red/black pump wires "at the pump"
When we test pumps on the bench its done using washer fluid and a variable power supply going up to 14v. The pump must make in excess of 250 psi on an M15 nozzle or it doesnt go out. You go to meth, that drops pressure 20%. You drop voltage and that will then drop pressure further. Voltage will drop across any length of wires. That is what it is.
Maybe need to make a Hot Wire relay kit for the pump right from the battery to give it that little extra OOMPH
