Well ..............went to the wheel dyno now I have questions

I went to the wheel dyno last night. It was disappointing to say the least. I may have hurt my motor last summer over a simple mistake. well I only got to put 562hp to the ground and 484 torque. I will be doing a leak down check and a compression check then I may do new pistons and ring etc to be able to bore it out and make it round again. I was thinking about things like stage3 heads or 4? or just keep what I have and have them flowed out more or what any suggestions??o No:

I think I may have a converter on its last legs but I dont know. I have an ATI 10 inch lock up style converter (was 4000 stall new now 5000):eek2: on the dyno it was locking up near 56-5800 rpm.

What would be a good converter to move 4000 lbs of car and be streetable when I want to??????? o No: 10 inch or 9 inch?? o No: Any suggestions?o No:

I also may (if I tear it down) change cams so I will be talking to Mike T about that............

Now I have an electric water pump and fans, is there anyone out there that has it wired to run at a certain temp or just continious??o No:

Thats all for the moment will think about it and ask more questions soon.

 

Mike, my 8 in ATI flashes with my motor to 4200. Seems to lock up nice rpms drop 1000 rpm on shifts. It is apparently the tightest 8 in they can make but I have heard of nitrous converters that are tighter.

Calling ATI right now....they owe me some dough...

Bruce
9.96/133

 

Mike,

To determine if you have a bad converter there are a few bits info needed:

1. Gear Ration
2. Engine RPM
3. Speed mph
4. Tire Diameter

With the four mentioned bits of info I can determine your % of slip in your conver. That is assuming that your trans is working properly.

Here is an example from my car.
1. 4.33
2. 7100
3. 150
4. 32

The Morose Power Speed Calculator says for the above data at 100% lockup my engine RPM should be 6800.

So.... 6750 divided by 7100 = .95 or 95% lockup and 5% slip.

Now I will say this is just an approximation but its fairly close. To monitor this and get the most accurate information then you will need sensors on your drivetrain. Give me the numbers and let me do some figures for you.

Take Care

 

John
What would mine be?

1)4.10
2)6600
3)133
4)29 in tire (was 29.5-worn)

Bruce

 

Bruce,

I dont know that you have worn a 1/2 in diameter off of the tire so I went with the tire size which you said is 29.5.

133mph with a 29.5 tire and a 4.10 gear would have an engine rpm of 6200 if the converter was locked up 100%.

So...

6200 divided by 6600 = .939 or 94% lockup which equals a 6% slipage.

For this to be more accurate you really need to have the rollout of the tire (tire circumference). When I buy tires I try to get the largest rollout for a 32" diameter tire in an attempt to keep the engine rpm down.

Hope this helps.... Anyone else?

 

410
6800
133 average speed
30

 

John..

Good info.

The only thing I would add would be that to do the converter slip calculation accurately, you need to know the grown height of the tire at speed.

For example.. Sweesy's tires, the standard growth 14/32.5's have a static rollout of 102 inches. But at 150 MPH, they grow 2 inches. So do to the calaculation, and come up with the accurate number for converter slip, you need that "grown" rollout.

Doug runs a "high growth" Goodyear, that grows twice as much as George's tire.

A call to your tire manufacture, will get you the growth specs.

JW

 

Mike,

For your combo 100% lockup would be 6150.

So... 6150 divided by 6800 = .904 or 9.6 % slippage

I would not like a converter that has more than 7% slippage. But again.. we are assuming that your tranny is fineo No:

If you make changes be very carefull. Thats a good engine. The more power you make the more complicated it gets!!!

Jim,

I agree with your comments totally! Thats why I mentioned using sensors throughout the drive train to determine actual converter slippage. I am not sure but I have heard there is a fairly inexpensive (I hate that word !!) tach that will record drive shaft speeds (rpm). So.. if you have engine rpm and drive shaft rpm then you could get a real idea of how your converter is working.


I will also say that I dont know how accurate one of wheel dynos are. Does anyone have any input on there accuracy??? At Norwalk this year Brian Earick had me put my car up on the chassis dyno. It made 497 hp and 627 ft lbs of torque with an air fuel ratio of under 12 to1. The guy running the dyno said it was tough to even get a reading because my rear tires didn't have enough air in them and caused funky readings. But hey.. if used as a tool to see if you make a change and the power goes up or down then the information can hopefully get put to good use.

Take Care

 

Mike
What made you put the car on a chassis dyno?

 

Just looking for answers o No:

I keep feeling Im missing something and I was hoping to figure out what the car was doing by holding it on the dynoo No:

I was wondering if the motor was working correctly and I feel it is but I think its down on power since while in Oklahoma I had the best air ever and I couldnt make it run:spank:

 

Mike,

It sucks to be in the lower end of any ET. When I was running 10.0s it drove me crazy trying to get that 9.999. My best ET for the year was a 10.007. Doesn't that just suck!

I would say if your running 10 teens at 4000 lbs then your right where you should be. If you use the .10 for every 100 lb rule then we are running very near the same. My car is 2800 lbs and went 9.00. Well... 1200 lbs different so add 1.2 seconds. That is a 10.20 pass and very respectable. Its time to start looking at weight reduction. Take off 500 lbs and your sitting in the 9.70s and you still have an engine that is very reliable.

Its a sickness Mike..... So many of us have the virus.

Good Luck!

 

I know but I want to be ready for next year so I was thinking a freshen up and a new cam etc we might find some power o No:

 

Hi Mike,

The dyno is a funny thing. What it shows may not, or probably will not, be what you see at the track. Funky readings will come from tire slippage. So you tighten the chassis down and pump up the tires. Not what you would do at a track.

I have a friend who is a "dyno racer". His car is not set up for drag racing, yet puts out 1192 RWHP. He has basically set his car up as a "driver" that will never see it's full potential outside the chassis dyno.

Keep in mind that dyno runs are in high gear and will really be thrown off with alot of converter slippage. I only made 437.99 ft. #'s of torque with a 10" converter that can be pushed to 4600 RPM. The cam quit at 5300. This is where the chassis dyno told my story...'dude your cam sucks. Change me or your converter, or this ain't happening'. I'm going for the cam change.

 

Not to stick my nose in where I dont belong.....but

I've often thought that this "Rule" is a bit vague as to speed range and aerodynamics, as well as starting weight

....as in how does it hold true for a 14 second car AND a 10 second car ???

.... or a Low slung car like yours John compared to a stock height street car like Mikes ??

....or, say a 14 second car starting at 4000# Vs. a 14 second car starting at 3200# ??

HP, weight, and aerodynamics gets alot more serious as the MPH increases significantly. The frontal forces of a 14 second car at the traps are MUCH lower than a 10 sec. one

 

Mike, I would be willing to bet that you are driving through the converter with that 535 and a 4000 pound car. Those 535's make so much torque, it's hard to contain that kind of power , specially in a small converter. I would think you need a 9.5 to 10 inch unit to transfer the power form that engine with that weight.
I watched a local guy here several years back with a 510 inch chevy motor with dual dominators and 500 horse of nitrous who could not get the car to et well. He had a little converter in it, I think an 8 inch, the car weighed 2800 pounds, the converter was supposed to be a 4500 stall, it would go 7000 rpm.
This car was in 3rd gear by 90 to 100 feet out and the rpm just stayed at 7000 all the way down the track. The car wouldonly go like 10.80's at 128. By calculating his rpm through the lights, tire size( not even compensating for growth) and gear ratio, this car should have been doing 150 mph through the traps. Jim Burek P.A.E. ENTERPRISES

 

John, pretty sure the tires were down to 29! Cords were starting to show!

Speaking of frontal forces and aerodynamics. Has anyone made a BETTER front spoiler. Both stronger and more effective?

Mine takes a beating at 130 mph. Washing the car a while back I noticed that the mounting bolt on the lower drivers fender ripped thru the sheetmetal and my support bar under the front of it was bent down.

I was thinking of something with a bit thicker (stronger) fiberglass and maybe one that would direct air around the car rather than a shovelnose like the stock GSX one.
Got to be worth some MPH!

Bruce

 

Converter selection

Mike:

Not to stick my nose in where it doesn't belong,:Browwell maybe) you have seen my car run, and I have a 10" converter in mine that flashes to about 5000 and runs pretty hard out the big end. I don't know what the slip is but 143 @ 6800 rpm in my car is pretty good. I agree with Jim B. on this:

I would suggest having the converter you have rebuilt, ATI should be able to help out. Or, I had JW rebuild my 8" a few years ago, and they were able to lower the stall at least 1500 rpm. A converter can go away for a number of reasons without actually coming apart, and it sounds to me like you are on the verge of this happening.

Just my .02

Hope all goes well, and looking forward to racing again next summer!:beer
Jim

 

I have a 10 inch now it was a 3800-4000 advertized converter.o No:

 

Yeah, ATI is learning about torque. They told me my converter would be 3500 but it ended up being 4200 with the hit of torque.

And your 528 is ALOT torquier still!

I'd send it to them and have it gone thru. If it is a older conv they have some better stators now to lock up better.

Bruce

 

Rambling answers

Mike:

Sorry, I wasn't clear. I knew you had a 10" in there, I just meant to say what Jim B. had said: Stick with the 10", just have it gone through by someone that knows converters. Like Bruce says: the guys at ATI should be able to tighten yours up so it works better with your combo or I believe JW can do the same, if you are not comfortable with ATI.

I would talk to whomever you have do the work, so they know exactly what you need and want.

Good luck:beer

Jim