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Old 09-04-2006, 09:07 PM   #1
reddevil
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goes 12.387 @ 116.5

Default Should I be maxing out 430 cc injectors at 12 psi @ 5k rpm?

ask this because I am now going lean over 5000 rpm. Not badly, but bad enough, 13-1, instead of the 11-1 that I want.

I am using a 1990 NA Legacy ECU with 430 cc injectors (stock are 270 cc) and Perfect Power 6.

I hit 5 volts (modified via the SMT6) at 5000 rpm, and it is at this stage that I start the leaning out. The MAF signal is about 4.3, but I am adding massive fuel along the whole way.

I go from 11-1 ratio and at 5k or so I jump to 13-1.

I suspect that the DOHC heads are letting in WAY more area, causing the leaness problem. Over 5k you can feel the increase in power due to the massive increase in airflow, but you can also feel the lack of fuel......

What do you think?

I have a RRFPR but I need to change it from the 12-1 rate down to 3(4)-1 rate.
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Old 09-04-2006, 09:18 PM   #2
cdvma
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If you are maxing out the MAF sensor either by adding voltage or in actual flow while trying to add more fuel via MAF modification there is no more fuel to add. If you are running a 12:1 RRFPR already you are pushing a lot of fuel pressure at the problem and I'd find a sure fix. Sounds like you might need larger injectors or a fuel system that can drive injectors without modifying the MAF. Any idea how your duty cycles are?
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Old 09-04-2006, 09:21 PM   #3
reddevil
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Sorry, I HAVE the 12-1 rrfpr, but not USING it. haha.

No I don't know the duty cycles
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Old 09-04-2006, 09:59 PM   #4
hippy
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What fpr are you using now? If it's not rr, then a rr one might help. It might be good to see if a 1-1 rise would give you the headroom you need, cause if it does, there's no real reason to make the rate go up quicker. At least that's how I see it.

peace
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Old 09-04-2006, 10:03 PM   #5
reddevil
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Yeah, I got the 1-1 ? brand one. The Bosch style that is 1-1 rr.

I NEED to hook up my fuel pressure guage again. I had misplace the sensor and it hops around the damn shop all the time.
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Old 09-04-2006, 10:52 PM   #6
cdvma
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Yea if you aren't using the RRFPR then a bump in fuel pressure might give you the overhead you need. With enough pressure you could end up removing MAF volts...but thats probably a chunk of pressure. What fuel pump are you running?
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Old 09-04-2006, 11:19 PM   #7
reddevil
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Walbro 255

I have 550 STI injectors coming in on loan. We will see how those work. But I will be getting the rrfpr working soon.


Using this page

http://www.witchhunter.com/injectorcalc1.htm

I can get upwards of 550-580 cc at 70-80 psi. But damn that is some pressure!
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Old 09-04-2006, 11:20 PM   #8
Jaxx
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+1 for maxed maf

i am guessing you have hit the top of range of the map as far as duty cycle goes

so at spool/low rpms you are still are able to make adjusments up but once you hit 5000 you can't add any more maf voltage so any adjustments are ignored and the ecu put out the duty cycles for the top row of the fuel map


the solution would be a bigger maf
you will have to do big negitive corrections at low load but there will still be range to work with at the top end

-j

edit:

even with bigger injectors you won't be able to adjust the fuel as the maf will satuate at 5000 rpm... i see a legacy turbo maf in your future .. or a nice speed density stand alone
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Old 09-04-2006, 11:32 PM   #9
reddevil
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No, the MAF is good. The actual MAF voltage is only hitting 4.5 or so at 14 psi! Stock, the Jecs MAF probably would have hit 5 volts just at 4k!
I am adding signal to it to get to 5 volts max, and thats where I run out of fuel when I hit 5k, the big DOHC heads are just letting in more air than the injectors can either handle, or the stock ECU is allowing the injectors to open up?
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Old 09-05-2006, 08:56 AM   #10
ride5000
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Quote:
Originally Posted by reddevil View Post
Walbro 255

I have 550 STI injectors coming in on loan. We will see how those work. But I will be getting the rrfpr working soon.


Using this page

http://www.witchhunter.com/injectorcalc1.htm

I can get upwards of 550-580 cc at 70-80 psi. But damn that is some pressure!
fwiw, i run 65psi across the injectors.

walbro gss342.



that gets me around 510cc/min according to the injector scale in the oem ecu... and it jives with the witchhunter online calc.
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Old 09-08-2006, 11:07 PM   #11
reddevil
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I have upped my base fuel pressure to an obscene 50-54 psi static. Had to seriously mess with the base map to get it to not have a 11-1 afr at idle!

So on boost I am 66-69 psi. This "should" fix my lack of fuel problems. And if it doesnt, we know something is wrong elsewhere!
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Old 09-09-2006, 01:37 AM   #12
hippy
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Not really. You might need some bigger injectors to get the a/f ratio you want while running 12psi on a 2.5 liter engine.

peace
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Old 09-09-2006, 11:57 AM   #13
reddevil
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2.2 liter
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Old 09-09-2006, 02:33 PM   #14
reddevil
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Moot point.

Broke a ringland on the freeway.

500 miles on that motor.

4000 rpm, 14 psi and 11-1 AFR and it just went.
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Old 09-11-2006, 09:10 AM   #15
Jaxx
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dam for an many pistions you blown you could have had a real ems by now :P
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