Converters.....what why how come

[lun40119]

I am not sure if this is the right place to discuss this but I will give it a shot anyway. Recently during a chassis dyno session my converter started to act funny. It is a nitrous holeshot 3600 in a th-400 in a 3200 pound street/strip car. In second gear I was unable to record real numbers until 5000+ rpm. In Third it started to couple around the normal(for that converter) around 4500 rpm. With the transbrake, it still stalls around 4400-4500rpms. What would cause the converter to flash to 5000+ rpms. And how bad is it in first? It is behind a sbc with around .600 lift and 265 duration at .050. Hopefully this is enough info if you need anymore don't hesitate to ask. Thanks

[Awesome Bill]

chassis dyno's are @ best a guess. I have seen some crazy stuff with chassis dyno's. Some are a very good tool for tuning but again, they leave a lot on the table. An engine dyno is really the only thing that you can start with a baseline and then see what it converts to in a real race condition. I know I am going to catch some slack on this but so what. Anyone who can properly detect from dyno sheets to actual track tuning can find out whats missing if anything. With a chassis dyno, they are still stretching a gauge and reporting torque. But with that, it allows for nothing else. Rotational weight is a factor, abnormally loading bearings, pinion angle, air flow sitting still verses 120mph wind? All these things make up the track conditions in real life. Now you can make your changes and see if the dyno makes a difference, don't get me wrong, but for you to plunk down $400-500 for a piece of paper makes no sense to me @ all. Other than an expensive piece of paper. Take it to the track, a playback tach, mph, tire size, weight and racing conditions will pretty much give you an accurate hp of watch you have at the wheel verses a real dyno tested engine. Then you see what your chassis is eating before it gets to the ground. If you notice a problem in second gear like its slipping, then you have a problem internal. But for this symptom to just pop up and you never feel anything, means something in the test was not working properly.

[lun40119]

The car performs on the street and track the same, but like I said it just wouldn't record any numbers below 5000. Like the converter was flashing to a different rpm. I wasn't too worried about it, I just thought that you could possibly have an opinion on what was going on. The dyno time doesn't cost me much of anything. It is just something to do to kill a sunday afternoon. Thanks for the help.

[Awesome Bill]

If your converter was going to slip it would be in high gear, and if it slipped that much, its no good for your application. This is why I am a big proponent on rpm gear tire size all being within the spectrum of no more than 5% slippage. Anything more than that, your loosing e.t. It does sound a little funny because once you start to stretch the load cell, for it to relieve completely or not read @ all is kinda suspicious. If you car performs well at the track then you don't have a problem, but if your mph verses rpm to tire and gear size is way off, the tranny or converter could be the problem. Lost cost dyno pulls like what you get are nice for that type of information.

[lun40119]

In high gear at 6300 the difference between the crankshaft rpm and the driveshaft rpm measured off the drum on the dyno, is 12%. I am having a new convertor built, any suggestions on where to look? I have talked to Hughes, Precision, and Yank. Thanks

[want-a-be]

Not sure but...you might want to look at your trans pump pressure. In the powerglides I have seen strange problems stem from the pump.

As far as converters go....I've had friends have good luck with both Coan and BTE. Some friends have been switching from Coan to BTE with good luck.

[lun40119]

It is a Hughes Performance TH-400 w/ a brake....I have the trans out of the car right now. Took off the pan and there was nothing on the magnets, and the fluid looked as nice as when I put it in. I am sure that there is no slippage occuring inside the trans itself.

[want-a-be]

Think it's more of a pressure/volume thing mainly to the converter. I think the 400 has a port that can be accessed to test the pressure. On heavy cars can be pretty on some of the most odd things. Ask a good tranny guy about his opinion of the pump. Try BTE,... good guys. I'm more an engine/chassis guy then a tranny guy so I'm not much help here.

[Awesome Bill]

you have answered you own question, you have 12% slippage, that only comes from the converters ability to lock up or go as close to 1-1 as possible, anything over 5% is wrong, It is possible that you have the converter into the pump to far. It needs to be a minimum of .125 and I like .150 out of the pump so the converter can be charged correctly. That is the first thing you should check. A lot of times that distance is closed off by the customer thinking it needs to be closer. Farther is better believe me with a trans brake. Pressure would not be the problem because you would have slippage all the time. It is a poorly designed sator, wrong window count for weight or power, could be the wrong pump? Who knows, What I do know is that most converter people build converters, they don't know anything about building engines. Get a person who can add and subtract, build converters and build engines, then you got the right converter. TSI, worlds fastest converter. They are specialist at making a converter slip enough to not kill the bottom end, and make it lock up over 5500 rpm so your mph and hp match closely. We have run their converters for years and only had 1 breakage and that was run for 3 years with no problems and finally broke the ATI aluminum stator that they used to use. We replaced it with a new steel unit. That converter will live forever. Good luck and maybe you should give them a call, talk to Kenny or Paul.

[lun40119]

Thanks for the help Bill. I am going to check into TSI and at least see what they have to offer. The current convertor did always seem kind of soft especially up top. I could do the math, but it was 12% at 6000+ just imagine how bad it is at peak torque :D What do you think about the MRT converter from ATI?

[Awesome Bill]

There is no such thng as luck with Coan or BTE. The converter is either built correctly or not! Its not brain surgery here, its a formula for HP and connecting it to your rear wheels. Weight of car, Gear ratio, tire size etc, all play a part. I always like it when the converter company, "whom do not build engines but sell converters", tell me they got the right one on the shelf for your engine. Most warehouse parts companies fall under this category way more. They don't know anything about the application nor do they care. Always ask questions and more importantly, buy from the people who take time with you, ask a ton of questions and are not quick to sell you their shelf stuff. JMO

[Awesome Bill]

Any sprag type converter is suspect to skipping and locking and unlocking. Its a SPRAG. The Mechanical diode is even still a sprag but is the better of the 2. The spragless TSI converters are what we use with all NOS and big hp engines.

The sprag does work very well under 800 hp and 750 ft lbs of torque and lighter cars. Coan, ATI, BTE etc will give you the excuse you must of abused it in the burn out and that lets them charge you another 500-600 bucks. Bull____!

Sprags are junk when it comes to power and you want consistency. I can run 600 hp worth of NOS with 400 on the tranz brake and letting it go @ over 1300 hp and bringing 200 more in .040 in behind it with a 3500 lb Camaro with a AwesomeGlide. I have never broken any TSI conveter I have ever had made without a sprag.

Bobby Mayes did the world a favor when he designed the real spragless converters. Why do you think all the other converter companies now offer it? Most of them were doing the spragless even while it was patent protected but they never designed and refined it as Bobby done and now TSI has continued to do. They are so far advanced in this method it does not pay to work with any one else. They warranty their stuff against breakage 100% with all my customers I direct to them or they purchase with my engines. I will warranty it if they don't as long as an installation error has not been made.

I don't know how much ATI paid Bobby to go back on what he preached for all those years to say the spragless was not good, but it must of been good. Let me get something straight right here, ATI can make a very good spragless converter as well as spragless. It not a secret every competitor has not had a chance to see a TSI spragless and get the know how. Its just the point of ATI telling TSI they have a product better than theirs.

It would be just like me saying RM engines are not as good as mine. That is silly, we all use the same DART or MERLIN blocks or another brand, we all use the same heads, choice of intakes, pistons rods etc are all out there. So my engine is no better when apples comes to apples. Its a macho man thing or something.

I will say my engines are priced more towards the racer and my tech service and phone conversations are second to none in the industry. I will not sell an engine to a customer if he does not purchase or have the proper equipment to make it work. That is what separates me from my competition. Or they at least listen to what is needed to make a Pro Magnum 565 with 1005 hp work in his car.

With DART Blocks and Heads, how can you go wrong? They really are second to none. I am not saying you can't make good hp with CFE, Brodix, AJ, Profiler etc. I use them all also. But, if you take the best engine and making 950 to 1000 hp with or without spray and put a 8" converter behind it, your nuts. It don't work properly and will not work properly no matter what you do with it.

PROPERLY is th key word. Same thing goes for Dart Blocks, put an inferior crank and rods in it and it breaks a rod, is it the blocks fault, of course not. But when engines don't run in the customers car properly, they always say its down on power bleme the engine builder. I don't have that. Why? Because they get a TSI converter with the engine when I get done with the dyno and they know it going in.

Even when you tell them it won't work, Bobbyjoe's converter company, no one in particular here, who don't build engines, has a lathe, knows a little about converters, usually enough to get you in trouble will say it will. End of story. The torque converter is the most important factor in racing. It is over looked 100 times more and will yield more power to the rear wheels when properly assembled than any camshaft or heads will ever do. JMO

I am not going to say you can get a spragless converter to run as well as a sprag on a SBC with under 750 hp. But it will not be as consistent and with more hp, the chance of breaking it will increase.

Bracket racers need consistency. With the converter correctly out of the pump, you will see very little difference in a properly set up and built right spragless. TSI has been doing it for a long time now. They are without a doubt the best. If I had to choose a Sprag type converter, it would be A1, Marv, ATI ofcourse, as long as they warranty it?, ha ha, or TCI. There are many other good converter companies out there but make them warranty your applicaiton against breakage, and that will separate the men from the wanna bbbbs and see who really cares if you get your monies worth every time. You can't break a spragless converter if you try if it has a steel stator of course.