Finally got car dynoed

John Smith

New Member
Dec 3, 2005
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Hi,

I finally got around to getting the car dynoed. I did this in anticipation of getting a supercharger (I have never trusted my cars health) The results of the dyno were mixed: The car seemed to make the right amount of power (233HP@around 4500rpm/274TQ@around 4300rpm) So, the power looked good, but the reason we didnt run higher RPM's was because the car was running pretty lean (AFR was 14.8 pretty much the whole time) and started to ping. The HP was still going up when we let off the gas(so, it looks like this car may actually be pretty strong for a near stock car) I was told to either get the car tuned, or try running 91 octane (highest we have here in CA) I am going to run 91 for a while and see if that helps.
 

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Do you have your AF graph? 14.7 is stioch which is what it should be at idle and cruising, but WAY too lean to run WOT even on an NA car.

Your AF should be 13:1 for NA, 12:1 with a power adder.
 
Well, I would get a tune except for the fact that I am going to add a supercharger within the next few months. I will of course be getting the car tuned at that point. I just dont want to pay to get it tuned twice. Can I just use the predator to add fuel. The guy who had my car on the dyno said he would add 20% more fuel if he was tuning the car.
 
91 octane

Don't even bother putting 91 octane in the car. The car set up for 87 and 91 won't make any difference except to waste money. I had my car dynoed also and after 2500 rpm it got real rich. A retune with a chip (diablosports) or whatever brand you decide to use is the only way to fix it permanently.
 
If youve got a predator you can correct this yourself easily. Id go out there right now and modify the fuel tables. Add like 5% to both ranges. That wont be an accurate tune, but it will be a lot safer than what you're running now. You risk destroying it at any moment with that lean of a tune.

One reason you're making so much power is because you're running so lean. Lean = mean, but also ='s BOOM.
 
triggz said:
If youve got a predator you can correct this yourself easily. Id go out there right now and modify the fuel tables. Add like 5% to both ranges. That wont be an accurate tune, but it will be a lot safer than what you're running now. You risk destroying it at any moment with that lean of a tune.

One reason you're making so much power is because you're running so lean. Lean = mean, but also ='s BOOM.

What exactly do I do? I assume that I modify the Factory HP Tune. Do I add 5% to both the 2000-4000 RPM WOT and the 4000-7000 RPM WOT ranges?

Thanks,
 
John Smith said:
What exactly do I do? I assume that I modify the Factory HP Tune. Do I add 5% to both the 2000-4000 RPM WOT and the 4000-7000 RPM WOT ranges?

Thanks,


Yeah thats all. Make sure you're ADDING fuel, going to the RICHER side.

Since you've got it though, you can gain another ~10lb-ft of torque by boosting the timing if you want. Thats where the big HP gain is.

If you add timing (by using the performance tune and then maxing the spark advance) i havent heard of anybody pinging on 93 with this, but you need to bring the AFR down some more to a safer level, say add 10% across the range

I'm trying to find my old dyno sheets to see exactly how much the fuel %'s increase the AFR. Itll differ slightly with each car, but I think I leaned mine out 6% to adjust from ~12:1 to 13:1. I'll get back to you on that.