Converter Issue?

One of the most critical areas of a automatic race car

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CHampshire
Posts: 9
Joined: Thu Oct 01, 2015 12:36 pm

Converter Issue?

#1 Post by CHampshire » Thu Oct 01, 2015 6:48 pm

Hello. I am new to this site but was referred by another member. I have been chasing 60 ft times all year and am now wondering if my lack of 60 ft time could be a converter issue. When I first put the engine in the car at the end of 2013 (October) the 60 ft times were between 1.16-1.19. Last weekend I was 1.219 and 1.220 over the span of several hours. The 1/8 mile ET has suffered, but the 1/8 MPH is staying steady at 130-131. I have made changes to the suspension (4 link changes, front strut settings, front spring changes, rear shock settings) but I can not get the car to leave like it used to. When it hits the tires, It flashes the converter at 6400, then the engine RPM drops to about 6200 and then climbs back up again and goes on up in RPM to the shift point (7400). The fall back after the shift is right at 6200 as well.

I run the MSD Grid controller (just installed last weekend) so I have a graph of what the engine is doing. Also, when I watch a video of the car leaving, It hits the tires and picks the front tire up, sets it down, picks it up and then sets it down again before the 60 ft clock. What I see on video corresponds to what I see on the graph.

I don't mean to ramble, but has anyone ever seen a converter that is hurt act like this? I will be happy to answer any questions or provide any info needed to get this issue sorted out.

Below is a link to the graph I mention.

Any help is appreciated.
Last edited by CHampshire on Fri Oct 02, 2015 6:19 am, edited 1 time in total.

CHampshire
Posts: 9
Joined: Thu Oct 01, 2015 12:36 pm

Re: Converter Issue?

#2 Post by CHampshire » Fri Oct 02, 2015 6:18 am

https://www.dropbox.com/s/6pyzltyxj4dgv ... h.jpg?dl=0

Link above didn't work. This one does.

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Marty Chance
Posts: 193
Joined: Fri Sep 19, 2008 6:34 am
Location: Cheney, KS

Re: Converter Issue?

#3 Post by Marty Chance » Wed Oct 07, 2015 3:35 pm

You have a couple of issues your dealing with. I did look at your graph and it doesnt look terrible , only issues according to rpm graph are the rpm pulling back down after the converter flashes and it drops 1200 on the shift. I would recommend having the converter stall raised 200-300 and that would be better, may also help consistency.
As for the 60' slowing down since 2013 that could be from updates to the transmission, have you changed the front pump , stator support or input shaft design? This can effect the converter charge pressures and exhaust flows which can effect flash stall and lock up
As for the front tires coming off the ground twice, that sounds like suspension. Do you have wheelie bars? if it hits the bars to hard you will spin and set front end back down which would explain why the engine rpm comes down after the flash. If the shocks are bottoming out this can cause the tire spin also and so can spline lock from the slip yoke on the drive shaft (Mark Williams billet is best)
Note (my disclaimer) don't take chassis tuning advice from a converter expert
I have thrown several things out there but with out enough info to really see what is going on. In short you may have to try some things
Marty Chance
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

CHampshire
Posts: 9
Joined: Thu Oct 01, 2015 12:36 pm

Re: Converter Issue?

#4 Post by CHampshire » Thu Oct 08, 2015 11:18 am

Marty,

Thank you for taking time to throw some ideas at me. I really appreciate it.

The car has no wheelie wheels so we can rule that variable out. You may be correct that the 60 ft time is off due to suspension issues. I have changed settings a bunch since I initially put the engine into the car in 2013. I have posted a link to a video of the car leaving the line in slow motion so that you can get a better idea of what you are dealing with. I apologize, I should have done this to start, I never even thought of it.

I don't have a data logger yet (Racepak coming soon) so I can't say that it is or isn't an issue with shocks bottoming out or fuel mixture or things of that nature. I was wondering if something could be broken inside the converter? It has a sprag inside but other than that I don't know much about converters. Could it be too tight and that's why the engine rpm gets drug down on launch? I agree with your assessment that it falls too far back on the shift also.

Also you asked about the transmission. It is a powerglide, 1.80 ratio, but it has been untouched also since it was installed. It was installed at the same time as the engine and converter so everything has the same amount of run time on it.

Link to video: https://www.dropbox.com/s/9r686a9exai82 ... M.mov?dl=0

Thanks again!

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Marty Chance
Posts: 193
Joined: Fri Sep 19, 2008 6:34 am
Location: Cheney, KS

Re: Converter Issue?

#5 Post by Marty Chance » Thu Oct 08, 2015 4:09 pm

1) get a data logger in the car and i will be happy to look at it with you and show you how to read it . on my web site there is a SCREEN SHARING app so you can click on it and we can link our computer screens through the internet so I am able to see your computer screen from mine then you pull up your data log and we see what is going on
2) i do not think your converter is broken but it may be too tight
Marty
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

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