Back from the Dyno

[LSR Mike]

Had some fun with the dyno, been needing a re-tune for boost increase (30PSI) and change of fuel to VP C-16 (117 octane).
The truck was having problems going lean at the top end. After a few pulls, Buschur was scratching his head until he looked at the injector duty cycle, 104%, so the old 880CC injectors were replaced with 1200CC units, duty cycle down to 64% AFR much more consistent.
The truck is still having a problem above 6500RPM, put in a new set of Iridium Plugs gapped at.018, better, but still something there.
Theory is the boost is blowing out the spark at high RPM. headed out to the junkyard for a new coil this weekend. We'll see what happens over the July 4th weekend.

In this state the truck made 335 HP and 312 ft/lbs Torque, that's Mustang Dyno Numbers, not DynoJet;).

5980

[mopar_ja]

Wouldn't you be better off with aftermarket coil pack.

[camoit]

Used coil LOL.... How could the boost blow out the spark? The valve is closed when it sparks. at 6500 RPM what is the shock wave doing inside the intake? It might be you hit the limit the manifold can run. How is it modified? It could be the shock wave is travailing up one runner bouncing around and into another at the wrong time. It could be somthing as simple as changing the length of turbo pipe before the throttle body to break up the shock wave. Then there is the amount of time it takes for the valve to accelerate and the spring Frequency causing the valve to hesitate on closing by 1 or 2 thousands. This could translate to more as the cam ramp falls away from the follower and the frequency bounce is in the wrong direction.
You need to talk with an Indy car engine builder or a motorcycle engine builder and pick there brain.

[LSR Mike]

Aftermarket coil pack? what's that? Actually I've looked, nothing out there. the recommendation is a MSD DIS-2 box... $600. I'm thinking the old coil I have is getting weak. Camoit, intake is heavily modified, no runners, Plenum. At those RPM's and my cam profile (284 degrees) and advance there is a lot of air moving.

5984

[Rahtid]

I would change the coil i have plenty of dsm buddies running 600hp with a new stock coil and the spark plug gap set at .18-.22

[camoit]

Maybe it's to much turbulence with out any runners? Just tossing that out there. At that RPM the volume of air is about 5000 gallon. Thats sucking a Hot Tub dry every minute. Thats not very green now is it? Even with 30 PSI of boost you need to think about the wave form that is created by the stopping of flow. You need to build a mock up engine top out of clear plastic. So you can run it like a wind tunnel and work out the kinks of flow. Get a nice laminar flow running through it. But then again you hold a record so what do I know. But if you want to make it have lots of suspension travel and go 165+ MPH then I'm your guy. ;)

[LSR Mike]

"But if you want to make it have lots of suspension travel and go 165+ MPH then I'm your guy. "

ROFLPIMP....