First, the car has a street port, T78, 550/1600, Power FC, 9 plugs, greddy 3 row.

Did a baseline at 11psi to make sure all readings were right on the log and dyno wideband. Oh, by the way, this is on a DynoMITE dyno, instead of a Dynojet or Mustang so the numbers will appear low anyway (usually by about 15% I was told). So we get to 279 on the first run. Air fuel on the LM1 wideband showed that at 5200rpm the afr dropped to 9.5, but the dyno wideband read 11.7. We finally figured out the LM1 sensor is dead. So now tuning off the dyno and "estimating" in my maps.

My target from max boost (3500) to 7500 was to consistantly richen from 11.5 to 10.8 hopefully a straight line.

Results: from 4200-5200 afr dipped to 10.8, then from 5200-6200 afr increased up to 11.8!!!!! and then tapered back down towards 11.5 by 7k. However, the power curve is dying as the rpm gets higher. In many cases we would get skips or pops from 6k up. I haven't had a chance to look, but I'm wondering if the plugs are fouled.

After turning up the boost to 14.5 and having the same dips and curves with the afr over the rpms, I only managed 332rwhp. Adjusted to a dynojet it's 389. Does this seem good for a t78/street port setup or low? Also, the flat-lining and hesitation from 6-7500 has me concerned.

Ideas? Thanks!

Richard

 

Is the dyno's wideband in the tailpipe? If so, put it in the downpipe. Rest of your problems are going to be hard to nail down over the internet..

 

The wideband is in the tailpipe, however, it's the longest sensor I've ever seen put in a tail pipe. Looks extremely suggestive... ie, my car was violated! It ended up about halfway in the midpipe. It also has a vacuum hooked up to it, so pulls the exhaust through its sensor. I was skeptical as well, but I think it may actually be a good reading.

 

You're seeing 11 psi by 3500 with your setup?

Could be an ignition problem. Look into the b10egv's from www.sparkplug.com. I run them on my setup up to 19psi with no problems (also have a jacobs amp on the leading). You'll need a thin-wall socket to use the plugs, which you can get from www.kgparts.com.

 

at 14.5psi, what should I see for rwhp on a dynojet? If the conversion is 389, is that right? My dyno sheet has a hp peak at like 6200rpm... so if 389 is low, it's gotta be in the upper rpm area, aka ignition.
I'll try out the egv plugs, no amp on the coil, what would y'all recommend? Thanks for the help!

 

The HKS twinpower is a decent choice, very easy install. I'm told it's not a true amp though, it is a double strike system.

 

definitely sounds like an ignition issue, regardless the power is lower than expected. i just did 365rwhp@ 12psi (mustang dyno) on a street ported engine i built using a busted up gt500r (same specs as a t78).

regardless you should be very close to 400rwhp on the scale you dyno'd on, around 430 or so on dynojet if you want to go that far.

T78 is a great turbo, you just need the rest of your system to be up to par with it you'll get there!!!

 

As Rich is saying ur having spark problems. And belive me ive had plenty of em.

Same thing happend to me on Greddy 10's with stock coils and Twin Power. The car would go fine up to about 7200 rpm, then fall flatt down on it's ***. Next year it would not even go above 6000 rpm.

Then i got some new coils, Mercury boat coils(god only knows why i bought em) and a MSD to power them for leading coils. And i had rock steady ignition again up to about 7500 rpm. But it was jerking above that. Was making 380rwhp at 15 psi of boost at 5500 rpm with stock coils.

Then i changed to Autronic 500R CDI box and Crane Cams LX92 coils this year, and hello 9000 rpm. Ooops, not tuned to that . Resault was a clean pull to 9000 rpm without any hesitation at all. But the other resault was low compression on the front rotor. So now it's comming out. And the and in putting in the RPM limit now :P

Well im guessing u got ignition problems. Oh and i tried stock 9 plugs with the new setup, and i had alot of ignition problems. I don't like stock plugs at all, except on stock enginges. Im running B11EGV all around.

JT

 

Oh and another note, the stock coils don't like amps in the long run. They will eventually fry out. The Twin Power works with them tho.

JT