Locking converter in 2nd gear with bigger turbos.

turbows6

Member
Joined
Feb 8, 2006
Ok, general question.

I want to lock the converter in 2nd gear. I have a bb6765 CEA turbo with .85 hot side (big hot side style) and if I lock the converter in 2nd with the transmission in "D" it will shift 2-3 at 5400 rpm.

With the gear split in a 200-4r with the converter locked that pulls the rpm down to 3500 in 3rd gear. That rpm is low enough that you can hear some minor compressor surge occurring and the motor is noticeably below the power band. The surge clears up at about 4000 rpm, it's not a terrible amount of surge, but you can hear some audible fluttering.

Has anybody else had this issue and what did you do? I plan on trying to manually shift the car up around 5800-6000 to increase the 3rd gear shift RPM (car has a quicksilver shifter, so I won't be "walking on egg shells" trying to shift it manually) , but I could also just leave it unlocked until it's rolling faster in 3rd, but I think the car pulls noticeably harder with the converter locked.
 
Getting the correct converter would alleviate it and likely make the car faster throughout the quarter mile. I would be very cautious with the timing having the engine rpm that low with the converter locked. Keeping the engine as close to peak power as long as possible will produce the quickest times.


BPE2013@hotmail.com
 
It has a zero-pump vigilante multidisk. It slips quite a bit. The RPM's drop about 800-1000 when you lock the converter at over 5000 rpm.

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It has a zero-pump vigilante multidisk. It slips quite a bit. The RPM's drop about 800-1000 when you lock the converter at over 5000 rpm.

Posted from the TurboBuick.Com mobile app
That's not going to be able to hold the engine in the power band. Unlocked
Will be above and locked it's pulling it way down
 
What is a desireable percentage of converter slip you are seeing with PTC stuff? (Seems like a lot of people are using those now)

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I need to look back at my last log. Mine may not actually drop by 800-1000 rpm by locking the converter. It's not easy to pay inredibly close attention to details like that going down the road.

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I've always locked mine at top of 3rd, I have same "0" pump vigilante. I've sent mine back in couple times to get loosened up with no change. It's the best converter for locking up @wot but is also the most$$$$ and the hardest to get right with a given combo. If I remember correctly i didn't see that much of a drop in rpm when i locked mine( maybe 7-800 rpm). If your shifting yours manually @58-6000 rpm i assume your not running a stock cam?
 
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What is a desireable percentage of converter slip you are seeing with PTC stuff? (Seems like a lot of people are using those now)

Posted from the TurboBuick.Com mobile app
The slip at the end of the pass is generally between 5 and 8%. that's not the most important thing though.what's most important to get the car down the quarter-mile is having it spend as much time as possible right at or the peak power. If the peak power is at 5000 then you'd want the engine to sit around 5000 RPM as the car is accelerated down the quarter-mile. You could have zero RPM drop and still accelerate the car down the quarter-mile just fine
 
I've always locked mine at top of 3rd, I have same "0" pump vigilante. I've sent mine back in couple times to get loosened up with no change. It's the best converter for locking up @wot but is also the most$$$$ and the hardest to get right with a given combo. If I remember correctly i didn't see that much of a drop in rpm when i locked mine( maybe 7-800 rpm). If your shifting yours manually @58-6000 rpm i assume your not running a stock cam?

Yeah, it doesn't have the stock camshaft. I looked back at my last data log and locking the converter at 5375 rpm pulled the motor down to 4550 (825 rpm drop)
I'm in agreement based on analysis of my last data log that I'd almost certainly be better off to lock the converter once the car is about 1/2 way through third gear. Locking the converter in 2nd results in a serious "bog" down to about 3500. Even if you manually shifted the car at 5900 it would still pull the motor down to 3950 rpm, which is a little too low for a heads/cam build.
 
Yeah, it doesn't have the stock camshaft. I looked back at my last data log and locking the converter at 5375 rpm pulled the motor down to 4550 (825 rpm drop)
I'm in agreement based on analysis of my last data log that I'd almost certainly be better off to lock the converter once the car is about 1/2 way through third gear. Locking the converter in 2nd results in a serious "bog" down to about 3500. Even if you manually shifted the car at 5900 it would still pull the motor down to 3950 rpm, which is a little too low for a heads/cam build.
Time for a converter
 
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