'86 L98 injector size for a modified engine?

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Jul 4, 2011 | 10:44 AM

86REDC4

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From: JACKSON NJ

'86 L98 injector size for a modified engine?

I'm trying to figure out what size injector I need for my 86 L98 motor. I've read about the formulas to do the calculation. But, do I use a .4 or .5 BSFC (brake specific fuel consumption) or something inbetween?And I have no way of knowing exactly what my horse power is. I'm guessing around 350 hp. Here is what my car has for modifications: heads: Trick Flow "Twisted Wedge" aluminum 2.02'/1.60", 9.0:1 comp. Cam: Crane .451"/.476", 204/214/110 degrees with 1.6:1 roller rockers. Intake: Edelbrock TPI 3860, SLP runners, port matched plenum and Holley 52mm throttle body, Bosch MAF with no screens or heat sink and smooth coupler, K&N filter with a cut open cover. Accel 30 lbs injectors, adjustable regulator and guage. Lingenfelter headers, hi flo cat, Flowmasters, crossover pipe. Hypertech chip and 160 stat. Rear gears are 3.73:1. Based on 350 hp I calculate, I should need between a 22 and 27 lbs injectors, but I read about numbers all over the place. Can anyone help me with some real sound or real world experience or advise? Am I off on the hp guess? The 30 lbs I have now are too large?

Jul 4, 2011 | 10:49 AM

ddahlgren

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From: Mystic CT

I ambetting the 30's will be fine and you use .5 and should only run the injector to 90% duty cycle. If the 30s are too big buy the 27s but why spend the money for such a small change?

Jul 4, 2011 | 11:01 AM

86REDC4

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From: JACKSON NJ

The car used to run the 1/4 in 13.7 (spinning the tires off the line and not shifting into 4th gear at top end) before the intake Mods (base plate, SLP runners, 52mm throttle body, 30 lbs injectors). Now it runs a second slower, But I get more RPMs with power. Before maybe 4,800 was the max power, but now maybe between 5,000 and 5,200 RPM. I'm thinking the injector are too much or the chip can't handle it and needs to be reprogrammed (not many doing C4s).

Jul 4, 2011 | 11:09 AM

cumbercr

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From: Santa Maria, CA

Have you done any datalogging? That will tell you if the chip needs to be modified and give the tuner the data he needs to make the changes.

Jul 4, 2011 | 11:22 AM

86REDC4

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From: JACKSON NJ

No data logging has been done. I found 2 local tuners that will charge between $ 600 and $1,100 to put it on a dyno and reburn a chip to match the car. I looked into systems to plug into the computer, but I don't have my own lap top, only a desk top computer at home.

Jul 4, 2011 | 11:32 AM

cv67

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From: altered state

St. Jude Donor '05

You need to talk with member mseven before tossing that kind of money out the window. Hes among the best imo.

Jul 4, 2011 | 11:38 AM

86REDC4

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From: JACKSON NJ

O.K. Thanks, ddahlgren, cumbercr, and cuisinartvette.....

Jul 4, 2011 | 12:05 PM

ddahlgren

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From: Mystic CT

Quote:

Originally Posted by 86REDC4

For around 700 you can get everything you need to make any changes you ever want for forever and you are in charge and not at the mercy of anyone else. It is a bit up front but not when you realize you may end up at the dyno 4 or 5 times over the life of the car. Even if you sell the car you should be able to recover 75% of the investment in tuning tools so they end up cheap in the end. BTW the Hypertech chip is more Hype than Tech..
Dave