Tuning question
Thread Starter
Teching In
Joined: Apr 2012
Posts: 38
Likes: 0
From: East Michigan
Tuning question Hello guys I'm having some issues with my converter. My question to you guys is : at what speed do you usually lock the converter and when you race it do u keep it locked or not. Or do you lock it immediately after the 2nd shift at WOT. Thanks ahead.
There is no set answer.You need to dyno the car with the converter locked and unlocked. Here is an example of an auto car with a 3500 converter dynoed both locked and unlocked. You need to plot the results vs mph, not rpm. In this example the only gains locking the converter would occur at 103 mph in 3rd gear. Below that mph the car makes more power to the rear wheels with the converter unlocked and slightly more with the converter locked above 103. This car would probably only trap 110-112 mph anyway. And this is on a Dynojet inertia dyno. What it actually does on the street may differ from what it actually shows on the dyno. As a general rule if locking your converter anytime makes the car faster you probably have the wrong converter in the car.
I have never seen an NA car run quicker with the converter locked @ WOT. Tested that several times. Another instance of "we don't race dynos". I have seen a couple run the same times either way. Have seen several turbo cars like the converter locked.
Cars with loose converters will usually repeat closer on the dyno with it locked, due to taking out the variable of converter slippage changing due to ATF temp variations. Makes your dyno numbers bigger too. :-)
Cars with loose converters will usually repeat closer on the dyno with it locked, due to taking out the variable of converter slippage changing due to ATF temp variations. Makes your dyno numbers bigger too. :-)
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TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
Na People have to understand that the converter multiplies torque while slipping...
there are several things going on here:
- slipping/stalling allows engine to spin up to where it makes the most torque,
- multiplying torque going into the transmission gives engine more leverage,
- the greater the slip the greater the torque multiplication,
- engine speed is not pulled down after each upshift;
(this is why a converter/cam would be a matched install)
this is why an NA car goes quicker with converter unlocked as Ed said.
there are several things going on here:
- slipping/stalling allows engine to spin up to where it makes the most torque,
- multiplying torque going into the transmission gives engine more leverage,
- the greater the slip the greater the torque multiplication,
- engine speed is not pulled down after each upshift;
(this is why a converter/cam would be a matched install)
this is why an NA car goes quicker with converter unlocked as Ed said.
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Go figure. Thread Starter
Teching In
Joined: Apr 2012
Posts: 38
Likes: 0
From: East Michigan
Thanks a lot for all your input guys. I had the car tuned the other day by Dr. Phil and I'm pretty pleased with his work and I recommend him to anyone here in east Michigan, he really knows his stuff. So by him tuning the car found that smth is wrong with my converter maybe smth broke or burned, it seems to be very lose, almost at 4000rpm and it's a 2800 billet converter from performa build. I still have a warranty on the full trans and converter since it hasn't been over 2 years so I'm hopping to get this fixed as soon as possible. The other thing I found out is that all this year and a half that Iv been driving the car without the speedometer fixed knowing that the guys that installed my gears they haven't put a 3.73 gear in there but a 3.42!!! Very upset about that since I was recommended to them and I was fully trustful. I'm hoping to get this thing straitened out to also. Really glad that Phil have found this things that were wrong with the car, the car feels reall strong after the tune and pulls hard but I'm really bummed out about all this other stuff and it makes me not feel good about the way it is!!!!