Mark Anderson

I just put my engine in my 928 race car and went to the dyno yesterday. From 2000-5200 torque and hp are almost the same as previous test but after that i've lost tons and air fuel ratio was good. Any ideas? Another strange thing is when I pull 1 spark plug at a time on the passenger side the idle drops noticibaly but on the drivers side it does not. I did do a compression test.

Randy V

Check the brown car - Jim took it.

Tony

You have one of theose PORKEN timing tools? worth a check

We gained a WHOLE bunch on Dariens car when we checked and then set them correctly. His power loss started sooner in the rpm range though.

I see "dastek" in the notes. Did you fiddle with that at all?
Have you tried the Sharktuner on it?

Jim bailey - 928 International

That would nearly double my power

Mark Anderson

That was one reason I did the compression test to see if both sides were similar but we may have to check cam timing next. Seeing as Greg Brown built the motor I'm sure it is correct.
The notes at the bottom are not correct. The dyno operator forgot to erase then from a previous test.

BC

You had to uninstall and reinstall the intake right?

With playing on the engine analyzer pro software recently, I learned that those kind of power losses can happen when the intake flow was screwed with intentionally or unintentionally.

Those runners are so large and long that if there is any reduction in total velocity, which may be kind of borderline anyway, it may hurt it easily.

Mark Anderson

The motor was just fully assembeled.

Rick Carter

Maybe the intake collapses a little and flow is altered.

soupcan

Mobil 1?

Darien

Easy to check CAM timing with Porkens.

Also could be a simple fouled spark plug or wire.

How about the fuel filter?

Throttle linkage preventing WOT??

soupcan

Loose engine vs. Tight engine, dyno after some miles are on the engine and the HP might be back.

Jim bailey - 928 International

What was changed was rods and rod bearings.

Darien

Forgot to add...how snug is the rear end on the dyno? I was loosing HP/TQ due to wheel spin.

worf928

Apples to Oranges comparison..... but, when my '89s Hall Sensor was bad I lost a ton of power in the upper range. It felt pretty flat above about 4.5k.

I think the Hall Sensor connector could be easily damaged during an engine R&R, especially if the sensor is more than a few years old. On the other hand I would think that would apply more to lifting the engine out rather than - IIRC - yours that has to drop out the bottom. On the gripping hand there ain't much room there no matter how the lump comes out.

Can you still use a Hammer on your beast?

Prior to the motor rebuild did pulling a wire result in different behavior?

Tim Murphy

Is the supercharger belt tightened properly?

Bad coil wire?
Bad coil ground?
Injector harness ground?