Calc.. rpm and converter slippage....hlep please

[Amelio]

I just installed a new PTC converter two weeks a 10" 3000 stall....prior to that I had an Art Carr 10" 3000 stall that had some kind of an issue it would only stall around 2000.

Anyway I went to the track last night to make some low boost passes....I was shooting for high ll's on 16psi......I felt this should not be a problem since the car has gone a 12.0@110 with the old converter crappy 60' taking forever to spool.

Well first pass out was a 12.8@ 104 on 15psi it was a bit rich I gave a turn on the wastegate rod.Next pass was 12.5@105 still same amount of boost I was expecting to see 16psi but it stayed the same....no biggie really the car was still rich. I dont have a logger I was just going off how the car feels,sounds and my mv's

Here is where my concern is, on the seond pass the car seemed flat at the top like I was running out of gear I dont know the rpm because I was watching mv's on the scan master the stock digital tach was ompletely lit 3 red bars whatever that means but I felt the car was done and over reving so i bumped it it into overdrive that last few hundred feet.

Then I started to worry about converter slippage....I have never felt like the car was reving too high with the other converter.

my third pass I gave the car 2 degrees in 1st to see if I could help the 60' and I was gonna watch my rpm's at the top this time on the scan master. Well th 2 degrees helped....1.69 60' and 12.4 @107 still on 15psi

now at first I was concerned about the low mph as I said it usually traps 110-112 at this low of bost. but this time I saw my rpms at the line....5575rpm crossing

I have done some calculations from the numbers I have 14.75% converter slippage but what bothers me is when I plug in tire heigth 26" gear ratio 3.42 trans ratio1.1 and rpm 5575 it tells me I should be trappinf 126mph

What am I doing wrong here and what is the possible issue.

Sorry for the long post I am a bit confused.

 

[Amelio]

Been doing more reading on converters and calculating slippage.....it seems once I subtract slippage from the mph the calculater says (126) ! am back in the ball park of what the car actually ran. Now I am not concerned with my e.t because I know the car has a 12.0-11.9 pass in it at this boost level...a few more degrees of timing and taking out some fuel and I am there.....my concern is my rpm vs. my mph

Now if I understand corretly the higher the stall the more you give up on effiiency which means more slipp at the top corret? Also with a higher stall it takes more hp and tq to make the converter work like it should correct? So maybe running this low of boost I am not making enough power for this converter....am I thinkikng correctly?

 

[pacecarta]

unless you are in OD the trans ratio is 1.0
what is your tire ?

once you have those
rear is 3.42 (unless its been changed out)
rpm at traps
then adjust the slippage (try some numbers) until the mph matches your trap mph

rough calc puts you at 19% (107 at 5575, 26 tire ,3.42 , in D)
might be the converter but could also be trans slippage as well

and looser doesn't mean less efficient , depends how its built and at what rpm you operate it..
dusty's 9.5 ptc nonlock are 6%or less slippage (close to 700hp)

 

[Amelio]

I am running a nitto 275/50/15 they are pretty worn I just measured them and they are 25.5" and I do run in D and yes stock gears 3.42's

My tire circumference calculates out to 80" when I plug that in I get 13.95% converter slippage

When I plug in my rear gear, trans gear and rpm it calculates 123mph then I subtract 13.95% slippage and I get 106mph which is just about dead o the car went 107

So now I know it seems like I do have slippage so how do I determine if its my converter or my trans?

Now is that too much slippage? I alwayas thought it should be around 6-8 this is a 10" NLU 3000stall

Now it may be my trans slipping but I doubt it, as I mentioned the car has run 12.0 @110 with the other converter now thre are variables because last nights run of 12.4@107 the car was still pig rich if I was able to make another few passes and pull some fuel and another few degrees I think it would be bak at 12.0@110

So the question becomes...is 13.95% too much slippage and if so is it the converter or trans? Since I just changed my converter I also servicd the trans new filter and fluid, I saw no evidence of problems. There was no material in the fluid and no burnt smell the fluid looked great.

I will call Dusty on Monday and ask where it should be unless he see's this thread.

 

[Dusty Bradford]

What rpm is it falling back to on the gear changes and what rpm are you shifting at? 14% is higher than I like to see so it may need to be tightened up a little. Let me know the rpm data and we'll go from there.

 

[Amelio]

What rpm is it falling back to on the gear changes and what rpm are you shifting at? 14% is higher than I like to see so it may need to be tightened up a little. Let me know the rpm data and we'll go from there.

Dusty I honestly dont know I dont have a logging device I only have a scan master so I was only able to see my rpm as I crossed the line. I can only go off of how the car feels and how it ran with the other converter I have not changed anything else same tires too. As far as shifting I just put it in drive and let it do its thing.....I am pretty in tune with how my car feels and sounds and it was reving way higher than usual at the 1000' mark

I just found my time slips from the last time I was at the track and roughly same boost level I had a slip for a 12.3@113 and 12.0@115

Both of those runs were at 16psi and +4 degrees in 1st......last night the 12.4@107 pass was same boost 16psi but only +2degrees in 1st which is 20 degrees total the only difference is the car was still fat. I am sure I could have leaned it out last night and dropped another few tenths and it put me in the same e.t 12.2-12.0 but there is no way I would pick up 5-8mph

The only thing I can think of is the converter is a lil too loose.....the onverter is the only thing I have changed since it was last at the track

 

[Dusty Bradford]

We know it's looser than what you had. Your other converter seemed to have a broken sprag or was a very low stall. What you have now can be tightened to get it somewhere in between what you had and what it stalls now. We really need to know what rpm it's shifting at to know what kind of move to make on stall speed. Data collection is the key to getting to most out of the combo.

 

[Amelio]

since I do not have data logging capability what is your suggestion? I could take it down the road and watch where my rpms are when the car shifts....its not a precise way of doing it I know but what other option do I have?

This is not a race car by any means.....it is a street car that gets ocassional track time. I am not looking to squeeze every ounce of perfromance out of the car but like you said it needs to be in the middle of what I had and the way it currently is.

Please let me know your thoughts.

Thanks for the help

 

[Chuck Leeper]

Power Logger time! A great Xmas gift to yourself......

 

[Amelio]

Power Logger time! A great Xmas gift to yourself......

oh beleive me Chuck I know a data logger is so way over due its not even funny......I have been trying to buy one for years but every time I get a few dollars stashed away somehing comes up and that money is gone.

I actually had some cash put away for a set of HD rocker shafts and a power logger then found that my converter was crap so that money went to the new PTC converter thats in the car now.

It never fails something always comes up and the logger keeps getting pushed back......uhhhhhh frustrating as hell!

 

[Chuck Leeper]

oh beleive me Chuck I know a data logger is so way over due its not even funny......I have been trying to buy one for years but every time I get a few dollars stashed away somehing comes up and that money is gone.

I actually had some cash put away for a set of HD rocker shafts and a power logger then found that my converter was crap so that money went to the new PTC converter thats in the car now.

It never fails something always comes up and the logger keeps getting pushed back......uhhhhhh frustrating as hell!

Oh ya! BTDT.....