Interesting Info regarding modified torque convertors and dyno readouts

[AZ94Q]

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 unlockedhigh 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 clutchlocked. 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 problemsnever 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 normaluntil 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 whatET and MPH the car will run.

[rsiwicki]

thanks for the info....I don't think that going from a 2100-2300 OEM stall to a fixed 2400 stall will affect the dyno readings. That is a really small jump and I have been thinking that after I get these things all put together that I will probably want a 2,500 stall instead, but I want to err of the safe side first to see what it does as 2400 is the minimum and I can only go up from here. Also a major factor will be traction...If I am smoking the tires from a stop easily at 2,400 then I can't see going higher and putting more hp & torque on the tires. If I have my car on Friday...I am going to the best dyno shop in South Florida...so this should give me a real reliable accurate read out.

[AZ94Q]

I can't wait for your new dyno results. 2,400 seems the way to go. I'm going to go with the PI dragon torque convertor@2400, with the level ten transmission.

So you're going back to dyno with the 4.08/level ten?

[rsiwicki]

well right now UPS lost my 4.08 rearend so I don't know what's up with that. It was fully insured so I am only out the monies on the core I bought off of ebay. I would have absolutely sh_t my pants and would be in jail right now for beating up the UPS people if they had lost my original core becuase then I would be without a car until I could find a replacement core and at the last junkyard I checked...cores were running $400 excluidng shipping. I am going to insure the next one out there for like $2,000 just in case that one get lost also to compensate me for my inconvience of driving a crappy rental car while I find another rearend.

Most likely...it will be just another dyno run with nothing major done except for a throttle body cleaning, new fuel pump, O2 sensors, and if I am lucky a rail flush. The dealer mechanic absolutely refuses to do a rail flush unless something is wrong so I have to find another shop to do it. So other than some standard maintenance...the dyno runs should reflect stock numbers.

The new transmission should arrive Friday or Saturday...I hope to have it installed sometime early next week. Then I will do a dyno run with the new transmission...then after that maybe UPS will find my rearend and I can have that installed and then we do the dyno run with a 4.08...that is the plan for now until something else goes screwy...

[Q45tech]

Lockup TC clutches are not designed to handle much power......like maybe 30 HP at most ...[they unlock on even minor acceleration]....manually locking one up on a dyno is a good way to blow the transmission and $3,000, in a second!

Lockup clutch is only designed to improve mpg at a steady cruise in 3rd, 4th or 5th gear.........on any up grade trying to maintain a steady speed should unlock it immediately.