Originally Posted by SharkSkin

Having seen the chart, I can see that it's the incosistency from 4000-5500 RPM that is of primary concern. Lots of good suggestions above -- while on a dyno(of any kind - even a smog dyno) you could watch for erratic timing numbers as you pass through that RPM range. You could also pop the cover on the flappy pivot shaft and put a piece of tape on the shaft to see if it behaves erratically. Dyno tuning/diagnosing can get expensive; if you can borrow a smog dyno you can make the observations above without actually needing to have HP/Tq info. Something else you might try if you're willing to round up the necessary hoses/tees/etc is to bypass the breather hoses; IOW connect them together into one large hose that leads to a coffee can full of pot scrubbers, then plumb another hose back up to the intake fittings. This would at least eliminate oil ingestion as a possible cause. Might be a lot of work for nothing, as oil ingestion would be very unlikely to affect just the first and third runs in such a bizzare way. OTOH, oil ingestion could lead to detonation, retarded spark, and all that that implies but again I would expect it to do so more consistently.

If I were betting, I would put my money on an intermittent flappy or knock sensor system being the problem in the 4-5.5K region. Most likely electrical, but possibly vacuum on the former.

As to the generally low numbers.... no bet. Another suggestion though would be to check for worn bearings that might increase the driveline loss. Any transaxle/CV/bearing noise? Also, unusually heavy rear tires/wheels could account for a difference in measured RWHP on a roller dyno.

Originally Posted by mark kibort

nah, flappy seems to be working, and its not just coincidence that the mixture went real fat right where the dip in torque was. if flappy isnt working, there is no attempt of the hp or torque to climb back up after 3500rpm.

Yes, i did the e-brake thing once. the vibration killed the transmission on the 3rd run and broke 5th gear!! (3rd run we found the ebrake slightly on, and released it.)

MK

Originally Posted by SharkSkin

Working, sure... but maybe it's sticking or fluttering in some indeterminate state occasionally.

about the e-brake... was it a matter of "WTF is that smell?" or did you bump into the issue some other way?

Originally Posted by Ketchmi

Since you were speaking from personal experience, I guess it can happen. I can honestly say that with more than a few hundred dyno runs under my belt that I have never left the e-brake on.