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Old 07-19-2002, 07:24 PM   #1
tsfxRS
Scooby Specialist
 
Member#: 8442
Join Date: Jul 2001
Chapter/Region: NESIC
Location: back in eastern mass
Vehicle:
98 2.5 RS
blur of red

Default Fuel injector upgrade - Comp. questions

I have a 98RS I am trying to make sure its gettting enough fuel for a nitrous application. When running the 55 shot from the Zex kit my EGT's run cooler and stay around 1400, my AF ratios are still full rich lol BUT I want to push a larger of a shot and tune the car a bit. What Im doing is putting in a set of injectors that will flow 330-350 cc/min which should be enough fuel for 230-270 according to someone ive spoken with about it.

The question I have is with this injector upgrade as is the cars going to run super rich so it will need to definitely need to receive some negative correction. NOW can this be done by reporgramming the stock computer to get it close and then tuning it with the SAFC? Or should I leave the stock program alone and just tune it all with the SAFC?

Performance mods done to the car:

WeaponR intake (in a UPS truck as we speak)
Zex Nitrous kit currently pushing 55 shot but might up to 65 or 75)
High flow fuel pump
Fuel pressure riser
330-350 cc/min injectors (waiting to install)
2 stages cooler NGK plugs
One stock cat to highflow cat
Custom 2.25 back to a stromung dual tip
SAFC
EGT gauge and probe
A/F Ratio Gauge
Short throw


Any help or suggestions are greatly appreciated
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Old 07-19-2002, 09:07 PM   #2
Kevin Thomas
Street Racing Instructor
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Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
Vehicle:
1989 1989 XT6

Default Playing with numbers

I am not sure about the 2.5RS's cc number but I think it's 280cc right?

If so, according to RCeng site fuel injector worksheet:

@ 80% duty cycle, with a BSFC of .43 (naturally aspirated), fuel pressure of 70psi (nitrous raises the fuel pressure to around this number), using 4 injectors.....you wouldn't hit the max duty cycle until about 251hp. With a 75hp shot of nitrous, you'd be around 235-245 range. You should be ok!

But to answer your question, "The question I have is with this injector upgrade as is the cars going to run super rich so it will need to definitely need to receive some negative correction. NOW can this be done by reporgramming the stock computer to get it close and then tuning it with the SAFC? Or should I leave the stock program alone and just tune it all with the SAFC?"

Yoshio in Canada can 'flash' your ECU to handle the new injectors (so I was told). I don't know what the limit is that the ECU's flashing can handle as far as injector cc's go.

From reading here at the I-club, I learned that the SAFC is supposed to be able to handle upwards to 50% more than the stock injectors can handle. In other words, if your stock injectors are 280cc's, then the SAFC should hypothetically be able to handle upwards to 420cc's and no more. Beyond the 50% more fuel than what you were running stock, the SAFC wouldn't be able to lean out the fuel mixture enough for decent drivability. This is the way I understood it.

What I'm saying is from what I have gathered here, the SAFC would be a good option to go with as far as leaning out the fuel mixture for tuning. It should be able to handle it fine.

That's what I learndeded.
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Old 07-19-2002, 11:58 PM   #3
tsfxRS
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Join Date: Jul 2001
Chapter/Region: NESIC
Location: back in eastern mass
Vehicle:
98 2.5 RS
blur of red

Default

Quote:
What I'm saying is from what I have gathered here, the SAFC would be a good option to go with as far as leaning out the fuel mixture for tuning. It should be able to handle it fine.
Those were my thoughts but to be honest my concerns revolved around someone smashing my window and the easiest things to grab are the gauges and the SAFC Will I be able to drive home on those injectors without the SAFC in the car lol. I guess I will just bury in the console somewhere and make it easier to just steal the whole car. Thanks
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