I got my '93 LT1 396 dyno'ed on Friday. However, there was a problem. The shop said that my converter was flashing up to 5000 RPM very quickly and spining the wheels on the dyno drums. They said they knew if had lot's of power and was pulling fine up to this point but, couldn't get a peak dyno run due to the converter/wheel slippage. They tried twice. (see dyno results below and graph at link provided.)

I have a 9.5" Vigilante converter with 3500 stall. It feels like 3500 on the street. It's obvious from the times in my signature that it's up in the ~425HP RWHP range. They also said that the slippage would actually help on the street/track spinning up so quickly.

Anyone hear of this type of issue before?

Is there a way to workaroud this on the dyno like ramping up the power slower to get peak HP/TQ results?

Is this a dyno operator issue or a real issue that I need to resolve?

Can it be resolved with ECM programming of the converter of do I need to get the converter looked at?

Given the problems the dyno results below were much lower than what would be expected but, given the problems were a good indication that the engine does have power even under these circumstances.

Run #1 Conditions / Results:

94.33 Deg
29.83 in-Hg
18% Humidity
Max Power = 333.75
Max Torque = 359.86

Run #2 Conditions / Results:

93.80 Deg
29.83 in-Hg
18% Humidity
Max Power = 364.13
Max Torque = 384.00

http://picasaweb.google.com/lt1fun93...85013340373218

 

Get a new dyno operator! When you do dyno pulls you should be in third gear 1:1, you will not spin the tires on the dyno in third.

 

It was in 'D' third. I watched as they did the pull. I agree that I need to question the dyno operation but at the same time I can spin the tires in 'D' third on the street and strip so why not on the drums?

I'm supposed to call the shop tomorrow for an online login to get my results. I'm going to ask about getting another pull or two to try and get peak HP / TQ with out the typical ramp curve. I'm also going to see if I can get the setup fee waived for another pull or two to see if they can get it right!

 

Why not get a set of drag radials if you believe your tires are slipping on the drum?
But that being said, your mph IMO indicates about what your second dyno run was pulling. Our numbers are fairly close, and mine is a vert, which is heavier.....

 

Was it straped down tightly?
Add some weight in the back. There are guys w 1000rwhp and they can make dyno runs, yours shouldn't be an issue.

 

You may have had the shifter in Drive but the transmission starts in first and then shifts up to drive (3rd) as the speed increases. Start the car rolling on the dyno and let it shift into third and then at about 60 to 70 MPH floor it, that should stop the downshift and give you a real pull.

 

They said they did that on another Vette putting weight in the back. I think it was operator error and will question them on this. I will also try to find another dyno in the area and see if they have the same problem. If not, I'll go back to them and see what compensation I can get.

 

It had BFG drag radials 315/35's. MPH wasn't accurate due to the alleged wheel spin and converter flashing.

If you calculate my HP based on 1/4 mile time you get the following which is approximately the range I thought it should be:

http://www.onlineconversion.com/horsepower.htm

Horsepower Results - 1/4 Mile Method
Your vette weighs about 3500* pounds and can complete a 1/4 mile in about 11.63 seconds. That means that you've got about 439.76 HP at the wheels, and about 571.69 HP at the flywheel.

*Weight of Vette = ~3330 + 200 for driver.

 

Are you sure your dyno operator is not saying that the converter is loose, which causes the dyno to read less hp at the tires? On newer cars, the dyno operator will often lock the converter so you get a true pull without the adverse impact of a slipping torque converter.

At your power level, spinning the tires at the top of 3rd gear should not be a problem. That's the equivalent of 100+ mph.

 

Good advise!

 

Said another way, yes the dyno operator was saying the converter was loose causing it to flash/spin up to 5000 RPM.

How do you lock the converter?

 

I like your suggestion. I had a similar thought. I'm not as worried abou the hp/tq curve as I 'm peak hp/tq. But maybe I can get both with your suggestion. I'll go back to the dyno with this info and see what they say. I hope to avoid the setup charge and just pay for 1 or 2 more dyno runs.

 

Quote:

Originally Posted by 93lt1fun

.

If you calculate my HP based on 1/4 mile time you get the following which is approximately the range I thought it should be:

http://www.onlineconversion.com/horsepower.htm

Horsepower Results - 1/4 Mile Method
Your vette weighs about 3500* pounds and can complete a 1/4 mile in about 11.63 seconds. That means that you've got about 439.76 HP at the wheels, and about 571.69 HP at the flywheel.

*Weight of Vette = ~3330 + 200 for driver.

Try this calculator http://www.wallaceracing.com/hpcalculatorquarter.php

IMO the calculator you are using would not be very accurate due to it only using ET and weight for its calculations. I have always heard and believe that MPH and weight calculators are more accurate in estimating hp. If you put a set of cheap street tires on your vette, im sure your et would drop by at least 1/2 second, but that does not mean you lost hp.
BTW, there are 2 of the terminals on the diagnostic plug under the dash you can jump out to lock the converter in drive and overdrive. Do a search and you can find them. Its like A and E or A and F.
Good luck, and let us know how it turns out.

 

You have to plug in to the PCM to command the computer to lock the converter. I know it can be done on newer vehicles, I'm not sure if it will work with OBD1.... Typically, you see a nice hp gain with the converter locked.

 

I found the info. on the 93 TC lock up. Make a jumper and put it between pins A and F. You can verify it locks by driving the car. It will not lock in first gear, only in 2 through 4. You will be able to feel it when driving. Its like a manual transmission, no slip at all.

 

OK so I did some a survey of several HP calculators. Lot's of answers but, I think the results show that 1) wallracing.com is very conserbative in the calculation and many are consistent in the their estimate using lbs / ET / MPH.

Based on the results it looks like 440 RWHP is a good estimate. I know dyno will be the most accurate but until then I have a good idea of where my RWHP and EngHP is.

Here the results from various online website calculators:

wallaceracing.com:

• Your HP computed from your vehicle ET is 361.17 rear wheel HP and 401.30 flywheel HP.
• Your HP computed from your vehicle MPH is 414.29 rear wheel HP and 460.32 flywheel HP.

fastcoolcars.com (lbs / ET / MPH)

• 450 RWHP
• 562.5 EngHP

dsm.org (lbs / ET / MPH)

• Using the ET method, I come up with 440 (RWHP) horsepower
  Using the Speed method, I come up with 460 (RWHP) horsepower

fantasycars.com (lbs / ET)

• Your vette weighs about 3500 pounds and can complete a 1/4 mile in about 11.63 seconds. That means that you've got about 439.76 HP at the wheels, and about 571.69 HP at the flywheel

engineersedge.com (lbs / ET)

• Your vette weighs about 3500 pounds and can complete a 1/4 mile in about 11.63 seconds. That means that you've got about 439.76 HP at the wheels, and about 571.69 HP at the flywheel.
  

gordon-glasgow.org (lbs / ET / MPH)

• 450 RWHP
• 562.50 EngHP

dragtimes.com

• 450.04

mustangworks.com

• Peak HP: 439 (RWHP?)
• Avg HP: 460 (RWHP?)
• Peak horsepower is based on your elapsed time (ET). The average horsepower is based on your mile per hour (MPH) and shows you the amount of horsepower, on average, your engine generated throughout a run. It is possible for the average horsepower used to be higher than the peak figure. This occurs based on many factors which come into play. Always use the higher figure to calculate track potential and fuel system requirements.

fordmuscle.com

• Your engine is making approximately 390.74 HP at the wheels, and about 461.08 HP at the flywheel.
• *Keep in mind this calculator estimates horsepower USED to obtain the ET you entered. Engine horsepower assumes approximately 18% loss through the drivetrain. If you spun the tires, missed a shift, etc, you didn't use all of the available horsepower. The calulator is most accurate when you input an ET that is close to the optimum ET your car can achieve. Your car should be accurately weighed at a certified scale as well.

P.S. Thanks for the suggestion and subsequent post from 93 ragtop on the torque converter lockup procedure. I'll make a jumper and take it back and get it dyno'ed. I also have DataMaster scanning softwrawe now and will use it also.

 

I forgot to mention this earlier, but before locking the converter and running full throttle, you may want to check with the converter manufacture and see if its ok to do so. I was told one time that the lock up is designed for cruise conditions and not designed for full throttle conditions. Dont have any experience with problems from doing it, but to be safe you may want to check. Good luck and let us know how it goes!!

 

Dude says in his first post that he has a 9.5" convertor.....I doubt that it can lock at all

 

Here is a link to the converters. http://www.converter.com/vigilante.htm They actually make a lock up 9.5 in converter with stalls all the way up to 6000 rpms.

 

Vigilante makes converters that lock. The Grand National Turbo guys have been jumping and locking their converters for years.
My Vette ran 425rwhp with my 2800 stall Vigilante, 3.75 gears, 396LT1 with LT's, and Comp Cams XE 230/236 cam. Here in Hawaii, SAE corrected.
And this was on street tires, granted they were BFG KD 315's, but street.
Was this a Mustang Dyno, or Dynojet?