Need some thoughts on lean condition

BLOWN38

BLOWN38

SCCoA Member
I checked the car out this weekend and found a busted hard vacuum line, fixed that, nothing changed still runs 13:1 at WOT.

installed autometer electric fuel pressure gauge took car out for a spin and saw 54 psi. It may go higher but am worried about the AFR so didn't push it for a long distance. So the fuel pump and regulator seem fine. I did install a new fuel filter.

Snow kit functions, not sure if the nozzles are clogged will check them tonite.

? i have is am I just maxing out the tune with the cool dense air? And if I am could I throw a 625ml snow jet in it and run straight meth instead of the 50/50 and get the AFR to the proper level until i get back to the dyno? the jets it have now are 125ml before blower and 325ml after blower. I would replace the 325 with the 625. I have one more race this season this weekend. Or do I order an adjustable regulator and bandaid it that way.

A few weeks ago the car ran 11.63 at 118 with nitrous holding 11.2:1 AFR and nothing has changed on the car just the temp outside. Car runs great other than what the LM1 is telling me.

I did a search and saw a thread by Charles at Magnum Powers talking about maxing the 255 fuel pumps at 400 rwhp, thats about where I'm at. but then again it was fine a few weeks ago on a dry shot of nitrous.

I have a 225 HP fuel pump in the car. Its a few years old with maybe 10000 miles on it.

Thanks for any input
 
Fuel pressure is not directly correlated to fuel flow. If all else is the same, just suddenly looking lean going down the track, I'd say check for a restricted fuel filter, or sock filter in the tank. I'm guessing fuel flow is down.
 
Oh and Ken Wagner or someone can you post a pic of where you cut the hole in your floor under the rear seat to be able to get to the fuel pump hat so I don't have to drop the tank?
 
I think your fuel pump isn't able to keep up. Few things you could do.

* Run a dedicated electrical circiut for the fuel pump to increase pump voltage. Run a 10 gauge wire from battery to a relay mounted beneath rear seat. Use existing pump power wire to switch the relay.

* Install a KB boost a pump to increase pump voltage.

* Change stock pressure/supply line to 6AN to increase flow.

David
 
Chris,

It may be that with the cooler denser air you aren't getting enough fuel to the rails with the stock system.

Don't know if you have an adjustable regulator or not but that would be the first thing I'd try, If I were adding parts. If that don't work you may want to step up to a larger feed line from the tank to the rails. It may not be pressure so much as not enough volume to feed the beast. I'd definately make sure that the sensors are reading correctly first though. It may be you actually have no problem at all just a false reading from a sensor. Might be worth a shot to take it to a shop and have an AF ratio run without the LM1 to see what it comes up with.

I'd hate to see you throw lots of money in parts at it for no reason. That would certainly verify the fact whether it is lean or not.

Just some thoughts on my part.

Get her fixed, I want to see you get her on down there this fall.

:)
 
1MTNCAT said:
It may not be pressure so much as not enough volume to feed the beast.
Click to expand...

If your pressure stays steady at WOT, then you have enough volume. If the injectors were running the rail dry, the pressure would drop.

I too am wondering if the AF reading is correct. It would be good to verify it.
 
David Neibert said:
I think your fuel pump isn't able to keep up. Few things you could do.

* Run a dedicated electrical circiut for the fuel pump to increase pump voltage. Run a 10 gauge wire from battery to a relay mounted beneath rear seat. Use existing pump power wire to switch the relay.


David
Click to expand...

Thats a good thought. Been there many a times on a blown marauder. Know exactly what to do.:cool: And its cheap.

Might be worth a shot to take it to a shop and have an AF ratio run without the LM1 to see what it comes up with.
Click to expand...

Yeah been contemplating that too. I think the LM1 is correct tho. It switches back and forth at idle and part throttle stays around 14.7:1. and goes good and fat at just under WOT. And I don't have an adjustable FPR yet.

* Install a KB boost a pump to increase pump voltage.
Click to expand...

What is the preferred setup for a return style system for the BAP? Run it at the upped voltage all the time like on a returnless before the FPDM or reference it to boost to only up voltage when its needed?

I would think only when its needed to extend pump life, but not sure so I'm asking.

Still have the ? of why the fuel system supported the dry nitrous shot to whatever HP it takes to run 11.63? Was it because the regulator upped the fuel pressure?

I'm assuming ZEX uses bottle pressure to send pressure to the regulator to get more fuel pressure at the injectors.?
 
S_Mazza said:
If your pressure stays steady at WOT, then you have enough volume. If the injectors were running the rail dry, the pressure would drop.

I too am wondering if the AF reading is correct. It would be good to verify it.
Click to expand...

Don't really know what the pressure does at WOT cause my eyes are glued to the LM1 and not the fuel pressure gauge. And I see 13:1 and out o the gas i go.

what gas are you on? leaded race gas can mess up the reading

also do you have cats?
Click to expand...

Never run leaded over the LM1 or thru my car at all. No cats in race form.
 
BLOWN38 said:
Thats a good thought. Been there many a times on a blown marauder. Know exactly what to do.:cool: And its cheap.



Yeah been contemplating that too. I think the LM1 is correct tho. It switches back and forth at idle and part throttle stays around 14.7:1. and goes good and fat at just under WOT. And I don't have an adjustable FPR yet.



What is the preferred setup for a return style system for the BAP? Run it at the upped voltage all the time like on a returnless before the FPDM or reference it to boost to only up voltage when its needed?

I would think only when its needed to extend pump life, but not sure so I'm asking.

Still have the ? of why the fuel system supported the dry nitrous shot to whatever HP it takes to run 11.63? Was it because the regulator upped the fuel pressure?

I'm assuming ZEX uses bottle pressure to send pressure to the regulator to get more fuel pressure at the injectors.?
Click to expand...

Chris,

I'm using a KB boost a pump in my 91 and have it set to supply 10% more voltage at all times (30% if using nitrous). It comes with an adjustable pressure switch, but I didn't use it. I mounted the control box and voltage adjustment knob in the trunk (set & forget).

Even cranking the voltage 50% higher, has no impact on fuel pressure at idle...just doesn't drop off on the top end.

Yes...Zex and other dry nitrous kits use nitrous pressure to jack up the signal to the fuel pressure regulator. The higher pressure provides more fuel (if the pump can keep up). On my car, 475 rwhp was about the limit the 255 lph HP pump could keep up before getting dangerously lean (with 6AN supply line).

I've heard that running a dedicated circuit can increase voltage at the pump by as much as 3 volts, so that's what I would try 1st.

David
 
Boost a pump can put more than 12v to the pump. Most pumps can accept up to 16v without burning up.

anyone notice there is a mustang triple fuel pump setup? Doubt it would fit in our tank, the top diameter seems a little large but it's an idea.
http://www.mustang50magazine.com/techarticles/m5lp_0810_ford_mustang_fuel_pump/index.html

You can test fuel flow with a 5 gallon tank and a stop watch and a wire jumper. pull the fuel inlet line off the rail and clamp a longer hose onto it. Stick the outlet of the hose in your 5 gallon pail, and then jumper the fuel pump lead in the EEC test connector. Start your stop watch and see how long it takes to fill to 3, or 4 gallons. Use that to calculate your gallons per minute and see how close it is to the pump spec.

That is a flat flow test. If you want to check it at a pressure, you can try and clamp on a small valve with a fuel pressure gauge plumbed in and adjust the valve to keep 43psi in the line. then try and fill the tank to see what your fuel flow is at 43psi.
 
Chris

Like Dave said the ZEX kit increases the fuel pressure when the system goes to WOT.

Make sure you check all your vacuum lines from the kit to the Fuel regulator. If a vacuum line has come off or has a hole it may not be pulling enough vacuum at the regulator for the pressure to adjust or stay where its supposed to.

If it was working correctly when you were running on the Nitrous before you may want to try it again and see if its running correctly. But check all the other things first. If I remember correctly, you should actually be able to activate the system without the bottle turned on. If so it should still fatten the fuel regardless of the nitrous valve being open or not. It should show a rise in the Fuel pressure at WOT and the LM1 should show the same thing and it should be fat since there is no Nitrous present.

Just something to try.
 
S_Mazza said:
If your pressure stays steady at WOT, then you have enough volume. If the injectors were running the rail dry, the pressure would drop.
Click to expand...

I am quoting myself because I had another related thought. I should have said that holds true unless you have some sort of blockage in the return line. But if you did, I would expect fuel pressure to spike under certain conditions. So that's probably not your problem.

Is there some way that you can check the injector pulse width?
 
1MTNCAT said:
Like Dave said the ZEX kit increases the fuel pressure when the system goes to WOT.

Make sure you check all your vacuum lines from the kit to the Fuel regulator. If a vacuum line has come off or has a hole it may not be pulling enough vacuum at the regulator for the pressure to adjust or stay where its supposed to.

If it was working correctly when you were running on the Nitrous before you may want to try it again and see if its running correctly. But check all the other things first. If I remember correctly, you should actually be able to activate the system without the bottle turned on. If so it should still fatten the fuel regardless of the nitrous valve being open or not. It should show a rise in the Fuel pressure at WOT and the LM1 should show the same thing and it should be fat since there is no Nitrous present.

Just something to try.
Click to expand...

I would think the bottle would have to be on to send pressure to the regulator to get more fuel pressure. But I could vent the nitrous nozzle to atmosphere so I don't get the extra air in the motor to make it even leaner if there is a problem and see how fat the AFR gets.

Is there some way that you can check the injector pulse width?
Click to expand...
If I can do it with common tools or the basic LM1. Someone would have to tell me how to.

I'm gonna rewire the pump tonite or tomorrow and check the pump sock. Still have to look at the alky jets too.

I'm also wondering if the filters on teh injectors are getting clogged. I work on outboards and go to a technical update seminar for Yamaha every year. And yamaha says that going from mtbe (the additive they used to put in gas to oxygenate) and then going to ethanol (the new clean oxy additive) reacts with each other and forms a plaster like substance on filter screens. In effect clogging the filter. But its been awhile since they went to ethanol around me but I also don't know whats in race fuel either.

But I may have some more time to figure this out. Looks like its gonna rain on saturday.
 
1MTNCAT said:
Like Dave said the ZEX kit increases the fuel pressure when the system goes to WOT.

Make sure you check all your vacuum lines from the kit to the Fuel regulator. If a vacuum line has come off or has a hole it may not be pulling enough vacuum at the regulator for the pressure to adjust or stay where its supposed to.

If it was working correctly when you were running on the Nitrous before you may want to try it again and see if its running correctly. But check all the other things first. If I remember correctly, you should actually be able to activate the system without the bottle turned on. If so it should still fatten the fuel regardless of the nitrous valve being open or not. It should show a rise in the Fuel pressure at WOT and the LM1 should show the same thing and it should be fat since there is no Nitrous present.

Just something to try.
Click to expand...


Steve,

It needs bottle pressure to increase the signal to the fuel pressure regulator. How much signal strength (positive pressure) sent to the regulator is dictated by how much nitrous you are spraying and how much bottle pressure you have at the time.

So with the bottle turned off, there won't be any line pressure supplied to the regulator to increase the fuel pressure, except for the trapped pressure between the bottle and nitrous solenoid/control box.

David
 
Well we figured I may be pegging the MAF. So I ordered a BA2400 an AFPR and a chip to go with the new MAF. I also ran a 10 gauge wire to the fuel pump.

Took it to the track friday and ran a 12.27 first pass with the AFR at 9.5 - 10:1. So I put some race fuel in it and turned off the alky inj. and ran 12.3x with the AFR at 10- 10.5:1. Let dad drive the car while I drove his, turned the alky back on so he wouldn't have to worry about anything, he ran a 12.37. So I turned the alky off an ran 2 identical 12.158's. So while it was running well for a mail order tune I noticed that the fuel pressure was only hitting 50psi and did confirm that the boost gauge was hitting 18psi so the fuel pressure should have been at 58psi during WOT.

I Did not get a chance to check teh vacuum line from the return plenum to the zex box or the regulator jet in the zex box or the line from box to regulator to see if something is clogged. I plan to do that tonight.

So I may have been pegging the MAf or i have a restriction in the vacuum reference line to the regulator which was making me not get enough fuel.
 
No never did log the maf. but I would like to if I find a restriction in the vacuum line. before i sell it.
 
Well, If it is stuck at 50psi I would check for restrictions. If it is falling to $50, the pump wire might not be enough for you. For example if it peaks and then drops while boost stay at the 18psi then there is still a volume problem.
If its stuck at 50 and does not go past it. I could be a vac reference problem. Or maybe the FPR is busted and has a leak.
 
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