Wally39

I took my car out to the same dyno shop I did last year to see how it's running. I went from a 3.6 pulley down to a 3.4 pulley and added the kennebelle boost a pump. So I thought I'd see how much more horsepower I had. Well, my horspeower went down and they said I was running very rich. In the 9's and it's robbing my horsepower. I don't get it, because back in November with the larger pulley and no BAP the air/ fuel was in the 11's. Right where it should be and horsepower was up. We tried turning the BAP way down and it made no difference. The guy at the shop said I should call JDM and get a different tune. He said if they reduce my fuel pressure by a couple pounds I should be right in there.
Any thoughts?

cheftjpeck

IMO, I think you ahve wisely invested so much money into it....why not invest into a custom dyno tune if it is available in your area...if it is running too rich then there is definitely some potential there....but if you can get a custom tune....otherwise...I agree work with Jim at JDM and see what they can do....whats your boost like now with the new pulley...??

drbobvs

Did you retune??? It sounds like from your post all you did was change a pulley and add a BAP. If that's the case, it's definitely not the way to do it. Our cars are extremely tune sensitive, so don't expect the previous tune to work well with the new parts. You definitely need to get a new tune from JDM or take it to a good dyno tuner who has experience tuning supercharged S197s.

Wally39

I wish I knew of a dyno tune shop around here. I'd go all the way to Chicago if I had to. My boost on a good air day will reach 9.5 and other times around 8lbs

hawgman

First off, let me say that you will NEVER hear me recommend a mail order tune over a custom tune. So I agree with the second part of your statement.

Having said that, JDM does know what they are doing. And they do make their average Joe's mail order tune a little fat. There should be no concern going down one pulley size with a JDM tune.

But yes, if your car is running rich and you don't want to get a custom tune or don't have the resources available to you to get a custom tune, then definitely call JDM and I am sure they will help straighten it out. But it would probably be a good idea to have data logs from the run along with the dyno info so they know what needs changed and where to change it. Just calling up and saying it is rich isn't going to help them much.

Wally39

I think I may have found the problem. I took out my spark plugs to gap them to .030 and one of the spark plugs smelled like gas and had some gas on it. It was gapped at .040 so I figure it wasn't sparking under boost. I gapped them all and stuck'em back in. Seems to run ALOT better. Hard to believe that 1 spark plug was robbing me of about 100HP lol I'm going to get the car dyno'd again just to make sure.

hammeron

cool......i'd be interested in seeing, if there
is a hp difference as well

GT Bob

I wouldn't count on that being your culperit. A BAP is going to make your Fuel Pressure go alot higher, and if it was added after your tune, then I garentee your still leaving alot on the table by running rich. One customer came to me to fix his Vette he had SCed by a local speed shop. By the time I was done re-tuning it, I picked up nearly 140 hp and 110 ft/lbs, just by leaning him out to a 11.8:1 from the 10to 10.3 the speed shop had him at.

Seriously.... you spent all that money on an SC, and your going to cheap out and get a mail order tune? Take the time to find someone who local and get it done to the exact needs of your car... not what someone 100's of miles away who has never laid eyes on your car thinks it needs.

hawgman

I think you are being a little hopeful in gaining 100hp from 2psi.

Wally39

No, what I meant was last year with a bigger pulley I put down over 400rwhp. Then when I just went yesterday with a smaller pulley it was running very rich and only putting 320 to 330 HP.