Well guys, I changed from a GM 245mm converter to a 9.5" Nissan that locks HARD. It was in a car with 140 more cubes and a couple hundred more hp, but he felt it was too loose in his setup. Anyway on to the chatter.

When I make the 1-2 shift it works fine, and comes on like gang busters. But on the 2-3 shift the turbo starts chattering and the boost gauge goes ape crazy. It recovers from it after a second but it still slows it down. When its chattering the wb shows lean. So I jetted it up and now when it chatters the wb shows 11.5-11.7 and after it recovers it goes back down to 10.0. It was only dropping around 200-300 rpm with the other converter and this one drops 1000-1200. I gapped the plugs down to 0.015" with no change. I have tried holding 2nd gear longer and it still does it. Anyone have any ideas?

 

Compressor surge?

 

That's what we are thinking, but what is the solution?

 

I thought compressor surge was only an issue when the throttle is closed? Since its an automatic I'm guessing you are not letting off between shifts. Could you be over spinning the turbo from the exhaust side? IE: need more wastegate?

 

If you look at a compressor map, and the lb's per min for your engine at a given pressure ratio is located to the left of the surge line, you may have surge. Basically means compressor is too large at that rpm, and pressure ratio. I had a 7.3 Powerstroke, with a programmer, and a stock turbo that would surge on 2-3 shift.

This is not accurate, but something like this.....

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Yep that's pretty much what it sounds like. It has a turbonetics Godzilla bov that is working correctly BUT I have the adjustment ran down as tight as it will go.

 

I backed off the bov. Took it for a spin and it still did it, but when I turned in the driveway the engine stalled. Popped the cap off and the screw holding my mechanical advance locked was gone AGAIN. That will be getting welded when I bring my welder back home. Anyway I put the boost up on kill and it pulled it even with a 10.0 afr, so I think the timing was bouncing around causing the problem.