Rpm drops between shifts

[Dwayne]

At the track the other night, the car was shifting at 6000 at the 1/2 and then falling to 4900. the 2/3 shift was at 5850 and then fall to 4800. These were all 10.90 runs at 124 mph. The car was very slow to spool until it got to about 7 lbs, then it would fly up to 24 lbs. I'm using a precision n/l supposed to be 3500 stall. This conv. has the "0" pump........Any suggestions

 

[Slow91z]

Suggestions for what??? The slow spool??? Maybe you need to lean out the bottom end.

 

[ijames]

The rpm drops sure make it sound tighter than 3500 stall - I would have predicted more like a 400-500 rpm drop even shifting at 6000. What is your zero psi boost rpm (brake torque up until the boost gauge just goes from zero to 1 psi)? Is this a new-to-you converter or have you been running it for awhile with different results and now something's changed?

 

[Dwayne]

i was having alot of tuning issues with the combo I had .(read here if you want some backround) I'm just getting the handle on how to tune this and I'm just about as low as I can go with my spool-up curve. I got this turbo about a year ago from John Craig, when I first put it on, it spooled faster than any turbo I ever had. It seems to be getting slower all the time, and I'm confident that nothing is wrong with the turbo. I looked at some Direct Scan runs from last summer with the same conv, less the ME-R, and the rpm drops were only in the 300/400 range

ijames; yes I have had this conv. for about 5 years and now I think it may be going south on me....I'll try the 1 pound of boost/rpm check this weekend

 

[norbs]

whats the rpm at 1 psi boost on the foot brake?

 

[TurboJim]

Originally posted by BigDaddy
At the track the other night, the car was shifting at 6000 at the 1/2 and then falling to 4900. the 2/3 shift was at 5850 and then fall to 4800. These were all 10.90 runs at 124 mph. The car was very slow to spool until it got to about 7 lbs, then it would fly up to 24 lbs. I'm using a precision n/l supposed to be 3500 stall. This conv. has the "0" pump........Any suggestions

Thats because an 0 pump is 2800-3000 at 0psi and not 3500. 3000 is a bit tight for a 70 turbo. I have a 3500 at 0psi and it is quite a bit looser than a 0 pump, my 63 spools like yesterday

 

[Dwayne]

update

.....I had a friend in the car with me 2nite and we took turns looking at the boost gauge and the tach.....with the car up to temp; it would build 1 lb of boost at 2,200/2,300.......a little tight to me ?

 

[norbs]

how much boost do you get on the footbrake? and how high rpm can you go? while holding the brakes?

 

[Dwayne]

..the other night at Muncie Dragway, I was at 5500 at the tree with only about 8 lbs of boost built up, it just took to damn long to start building boost........i can set on the footbrake until it hits the rev-limiter but it won't have much boost built up........i called precision and they said it would be 225$ to restall the converter.......I've got the big Ford drums on the rear so holding boost is not a problem, it's like being tied to a tree

 

[ijames]

Sure sounds to me like it's time to send the converter in for a checkup.