Guys we dynoed a before and after on a heads and cam LS1 with a M6 to a Th350 with a non locking PI Vigi. 4000 stall.

M6 402 rwhp SAE
TH350 338 rwhp SAE


What do you guys think about this. Is it normal that you loose this much power or is there something wrong with the tranny. I have heard that a real loose stall like the one used would act funny on the dyno and would lie. We are taking it to the track today to see what it will do.


JK

 

I made 351rwhp NA and 535rwhp on a 150 shot and ran the time in the sig. I also dynoed with 28" slicks at 15psi so that will hurt numbers too. So, Yes a th400/350 will show more loss than an M6. Not sure how much though.

Matt

 

I'm sure the loose converter is the culprit. I plan on putting my car on the dyno next month for a custom tune and I'm sure I'll only see around 350 rwhp because of my 4200 converter, but I don't care as long as it runs the way I want it to at the track because dyno numbers are just for show. Using all the different calaulators for hp I'm suppose to be making 350 at the wheels by my trap speed, but by my et it calculates to 415 at the wheels, so if I had to say the car in question will most likely run about the same as what it did with the M6, just that it will probably leave harder because of the converters tq muiltipication, yet lose a little time on the other end because of converter slip and will lose about 2-3 mph. Of course you may not see these results, but they are what I experienced when I swaped from a M6 to a TH350.

Randy

 

Those numbers look a lot worse than I would expect. I understood the TH350 was more efficient than the TH400, but I saw less of an impact going from a T56/Street Twin/12-bolt to a TH400 with a 5K flash stall non-locking converter.

Engine dyno NA: 486flywheel HP
Chassis dyno, T56: 425rwHP = 12.6% drivetrain loss
Chassis dyno, TH400: 390rwHP = 19.8% loss.

And as you go to even higher HP levels, the T56 losses will drop as a %, while the automatic will increase:

Engine dyno, N2O: 762flywheelHP
Chassis dyno T56: 670rwHP = 12.1% loss
Chassis dyno TH400: 600rwHP = 21.3% loss

Maybe its your converter.... I don't even know what the brake stall rating is on mine, and I haven't tried to brake stall it any higher than 3,200rpm. But it appears you are seeing about 26.5% loss.

 

Well we took the car to the track today and was able to get a 11.84 hitting the limiter on the 1-2 and the 2-3 shift(his first time with the new combo). I think it would easily run a mid 11 but the fuel pump took a dump before we could play with it anymore. Just to through in another car that we have done. A heads and cam LS1 car that makes around 355 rwhp with TH350 and PI Vigi. 4000 only ran a 13.35 @105 today with a 1.96 60'. But when we ordered the converter it was built for the car to use Nitrous. With a 250 shot the car went a 10.23 @128 with a 1.40 60'. That **** was crazy.


JK

 

yeah, i agree. that does seem like a lot of loss with a Th350. i wouldnt expect any more than a 17-20% drivetrain loss on that setup.

 

On Precision Industries' or Yanks' site there is a statement about the losses that show up on a chassis dyno with a loose converter. I believe they said that something in the software made it misrepresent the actual numbers.

On the car that went from a 13.5 to a 10.3 on a "250" shot, that's about what should happen. If it's a NX kit that 250 shot is really more like 300 (at the motor) and it picks up 3 seconds. The numbers it made on motor also seem about right for the time it runs N/A, aren't they? Just curious

 

Converter.

My hunch is the stall is set a bit too high for that combo anyway if you plan on running NA. I bet you do better with 3000-3400 stall without juice.

 

Interesting. More than a little insight on why that silver car only rolled 364 or so with a TH350, heads and cam...about what a buddy of mine made with just a cam and some shorties..
Wonder just how much more power loss a TH350 exacts than a 4L60?...
Whose car are you referring to here JK?

 

Drake it was Brad Boones car.

I got this info from PI's website.

THE TRUTH ABOUT DYNAMOMETER READINGS AND HIGH STALL TORQUE CONVERTERS
There is a misconception and a lot of misinformation about the poor vehicle performance numbers that are generated by testing a car with a high stall torque converter on a dynamometer. Most people that are not familiar with how a torque converter operates will automatically think that the torque converter is inefficient. This is totally false and the following facts are why you should not believe the dynamometer numbers while using an unlocked
high stall torque converter. All late model dynamometers have a software program that commands the loading and speed of the vehicle over a certain period of time while making a test pull. The software used in these dynamometers is setup to be used with a locked 1:1 connection between the engine and the rear wheels, such as using a standard shift transmission in 3rd gear or when an automatic transmission has the torque converter clutch
locked. When an unlocked high stall torque converter is used to make the pull and the dynamometer software has not been changed to allow for the fluid coupling differences the dynamometer readings will all be bogus. For instance, the low rpm torque readings will be high due to the torque multiplication of the torque converter being run in partial stall. Likewise,
the high rpm torque readings will be low due to the long period of time the dynamometer takes to allow the torque converter to transition from partial torque multiplication to a hydraulic locked condition. The only cure for this phenomenon is to rewrite the dynamometer software to prevent this from happening. Torque converters with a low STR or low stall are not as adversely affected by this phenomenon. The high rpm transition problems
never occur when the vehicle is being driven or raced normally. Therefore, worrying about what the dynamometer numbers are is a total waste of time. If your dynamometer operator refuses to alter the software to give correct readings then the only things you can do is (1.) lock the torque converter clutch and do the testing, (2.) use the readings you get with an unlocked torque converter as a baseline and continue to tune the car like normal
until you get the best numbers remembering these are just numbers and not the actual horsepower and torque or (3.) use a dynamometer shop that gives you the service you deserve for your hard earned money. The only really true test of the performance of a vehicle is to take it to the track and see what
ET and MPH the car will run.

 

AMEN
BC