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Subject: "About fuel system tuning (after turboed)"

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gilee_8	Nov-23-03 04:45 AM
Member since Jun 11th 2002 1441 posts,

#61193, "About fuel system tuning (after turboed)"
Nov-23-03 04:47 AM by gilee_8

Sup guys.
I know you guys will say "SEARCH", but I did. Maybe I am just stupid about fuel system. so plesae HELP!
But I do'nt get some things.

Some backgroud info: 6PSI boost, 30lb injectors, Walbro 255HP, Vortech SFMU with no bleed valve
(1995 Eclipse GS) (removed stock FPR)
Currently: 22PSI at idle, 60PSI at 5PSI boost, 75PSI at 6PSI boost

OK, I really have to get the followig question straighten out so I can tune my car right.

1) How do I know 22PSI is the correct idle fuel pressure for my setup? I can't use my A/F gauge coz it only works at WOT. but if I make it WOT, my car is in boost already??? HOW?

2) when at WOT, my A/F gauge read at .99x so I know the range should be .88 - .92 so I am rich (do I consider as super rich?)

3) So I definitely know when I am boosting, I am rich, but I don't know if I am rich or lean at the idle part. Also, if my boosting is rich, do I keep lowering my idle pressure till my boosting part is in the .88-.92 range??

Thanks everyone.
I know I am a novice on this fuel things.. .THANKS!
Gil:thumbsup emoji

~~~~~~~~Modification~~~~~~~~
Performance: MegaSquirt v3.0 Fuel & Spark, 8.6:1 JE piston, Eagle Long Rods, SPEC III Clutch, EVOIII B16G, FMIC, Aeromotive 1:1 FPR, Walbro 255HP, 680cc Injectors, 2.5" DP, 3" Magnaflow Cat, 3.5" Greddy EVO CatBack, Greddy Electronic EGT,FUEL,BOOST,A/F gauges...
Interior: Racing Seats, Metallic Interior, 15-Speakers System, Keyless, Dynomat Insulated, Neons...
Exterior: 1999 Body with turbo wing, Halo Projector Headlight, 4300K HID, 17" Mille Rims, GSX Calipers...
Coming Soon: Water Injection, Redo Undercarriage, Repaint Exterior

$240 For New Complete GSX Calipers Kit (Calipers, Bracket, Shim, Pad, Bolts, etc) Email Me If Interested!

1995 RED Eclipse GS-'T': Stage VI 20PSI
2010 Audi S5 Quattro

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Replies to this topic

RE: About fuel system tuning (after turboed), gilee_8, Nov-23-03 01:16 PM, #1

RE: About fuel system tuning (after turboed), Team

MetalJim, Nov-23-03 06:29 PM, #2

RE: About fuel system tuning (after turboed), gilee_8, Nov-23-03 06:52 PM, #3

RE: About fuel system tuning (after turboed), Team

Avenger, Nov-23-03 09:04 PM, #4

RE: About fuel system tuning (after turboed), gilee_8, Nov-24-03 01:09 AM, #5

RE: About fuel system tuning (after turboed), DSMRoadster, Nov-24-03 05:49 AM, #6

RE: About fuel system tuning (after turboed), corsagsbo, Nov-24-03 06:19 AM, #7

RE: About fuel system tuning (after turboed), gilee_8, Nov-24-03 11:30 AM, #8

gilee_8	Nov-23-03 01:16 PM
Member since Jun 11th 2002 1441 posts,

#61220, "RE: About fuel system tuning (after turboed)"
In response to Reply # 0

No one?

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MetalJim	Nov-23-03 06:29 PM
Donating 2GNT member 2135 posts,

#61252, "RE: About fuel system tuning (after turboed)"
In response to Reply # 1

It sounds like your A/F gauge is working fine. Thats the way they work - only at WOT. When the car is at idle or part throttle the computer will try to maintain an efficient fuel ratio - an A/F gauge will bounce back and forth from rich to lean while its doing this.

As far as the actual voltage is concerned, yeah .99v at WOT is real rich.

95 Eclipse RS : 5 speed
15.7 @ 87.9mph
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

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gilee_8	Nov-23-03 06:52 PM
Member since Jun 11th 2002 1441 posts,

#61253, "RE: About fuel system tuning (after turboed)"
In response to Reply # 2

THanks alot MetalJ..
You answered my #2 question.
Anyone for #1 and #3?

I really have to konw how I can know my idle fuel pressure is at the correct fuel pressure currently if A/F gauge only work for WOT, how do I know my current idle fuel pressure is right?

And if I know I am too rich at WOT (under boost) do I change to a smaller disk and ring or etc? to lower it? or just keep lowering right idle fuel pressure?

Thanks everyone emoji

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Avenger	Nov-23-03 09:04 PM
Old School 2GNTer 2453 posts,

#61254, "RE: About fuel system tuning (after turboed)"
In response to Reply # 0

Originally posted by gilee_8
1) How do I know 22PSI is the correct idle fuel pressure for my setup? I can't use my A/F gauge coz it only works at WOT. but if I make it WOT, my car is in boost already???

You really don't. What you want to do take your injector size, idle FP, and as much information as you can over to some of the equations found on RC Engineerings site. Given that our stock injectors are rated at 235cc/min @ 43.5 psi you should be able to calculate what FP you need to have your 30lbers (315cc/min) to flow apromiately the same. Lets look at the equation ...

SQRT(NEW_PRESSURE/OLD_PRESSURE) * Old_Flow_Rate = New_Flow_Rate

Take a look at your knowns and your unknowns ... you know everything but the NEW_PRESSURE. 43.So modify the equation to solve for that variable. The reqorked equation should look like this (it's very late so you'll need to double check my math).

SQR(New_Flow_Rate/Old_Flow_Rate) * Old_Pressure = New_Pressure

Now lets plug in variables ...

Old_Flow_Rate = 235 cc/min (but we want to use lb/hr so its 22.4lb/hr)
New_Flow_Rate = 30lb/hr
Old Pressure = 43.5 psi (because thats what hte stock injectors are rated at)

Solve and you shoud get 24.3 psi. So basically this only means to get your 30 lb/hr injectors to act like 235cc/min injectors that are running at 43.5 psi you have to run your 30lb/hr injectors at 24.3 psi. Unfortunately this is all moot unless your idle FP with your stock injectors were 43.5 psi. But if you know what your old idle FP was you can figure out the proper pressure by using the formula above a few more times.

Originally posted by gilee_8
2) when at WOT, my A/F gauge read at .99x so I know the range should be .88 - .92 so I am rich (do I consider as super rich?)

You really can't mess with it too much because you have nothing for fine tuning your fuel curve. The bleed valve on the SFMU would help but you don't have that so you can't. Some sort of piggy back fuel computer would help also. But to answer your question ... yes you are running rich, no you can't change that with out screwing up your rise rate. I would leave it alone.

Originally posted by gilee_8
3) So I definitely know when I am boosting, I am rich, but I don't know if I am rich or lean at the idle part. Also, if my boosting is rich, do I keep lowering my idle pressure till my boosting part is in the .88-.92 range??

I doubt your are rich or lean at idle. The ECU will compensate (=-25% LT and ST) while running in open(or is it closed ... I always forget which way it goes ... not at WOT) loop so you'll see the A/F gauge going back and forth. If you want to know if it's maxing out the ECUs compensation you'll need to get a datalogger to monitor the ST and the LT.Even though you see your A/F gauge it doesn't mean it's not working. Just seeing it cycle is a good sign. If you had an A/F gauge that didn't cycle at idle it would be bad. To answer your question NO DO NOT LOWER YOUR IDLE FP to get it the proper A/F reading at WOT. That's not what adjusting your IDLE FP is for.

-"Easy Mac"
05 Mazda RX-8 (RR8 #88)
99 Eclipse RS 398whp & 372lb-ft emoji

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gilee_8	Nov-24-03 01:09 AM
Member since Jun 11th 2002 1441 posts,

#61257, "RE: About fuel system tuning (after turboed)"
In response to Reply # 4

THank You so much Avenger!
I greatly appreciated! You Got a POINT!

Ok, so you saying, right now, my idle fuel pressure and the disk, and spring I am using (largest disk, silver spring) at 24 idle fuel pressure is at the right spot!

So the only way to make my car not running TOOOOOO rich (1.03x at WOT) is to add a bleed/check valve?
So where can I get one?
I searched through the archieve, and they have like "new ways" from the vaccum hose, or like directly from the bleed valve part.

So how exactlly do I install one? and where can I just buy a kit (set) and screw it on?

Thanks alot!
Gil:thumbsup emoji emoji

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DSMRoadster	Nov-24-03 05:49 AM
Donating 2GNT member 3445 posts,

#61278, "RE: About fuel system tuning (after turboed)"
In response to Reply # 5

eclipse2ner actualy did a write up for diy bleed valve from the directions I gave him. Search for it I'm sure it'll pop up. He even has pics.

intricatelines.com/ -graphics and vinyls

"Tell them of us and say,
For their tomorrow,
We gave our today."
-- The Kohima Epitaph

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corsagsbo	Nov-24-03 06:19 AM
Old School 2GNTer 390 posts,

#61281, "RE: About fuel system tuning (after turboed)"
In response to Reply # 6
Nov-24-03 06:22 AM by corsagsbo

Go to www.clippard.com, and get the bleed valve mnv-1k. (It's like $4.50) This will allow you make further fine tuning adjustments.

boosted 420a and ej2o..(my 2liter v8 eaters)

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gilee_8	Nov-24-03 11:30 AM
Member since Jun 11th 2002 1441 posts,

#61312, "RE: About fuel system tuning (after turboed)"
In response to Reply # 7

THANK YOU ALL!
Gil

I appreciated the help!

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