RPM DROP

One of the most critical areas of a automatic race car

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top452
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Joined: Mon Aug 17, 2009 7:45 pm

RPM DROP

#1 Post by top452 » Mon Oct 12, 2009 4:24 pm

Converter stalls at 6300 shifting at 7200.and drops back to 6300. There is no gain in RPM for a full second then it starts to clime. Any ideas/ Still went 8.28@164. How much am I loosing?

Marty Chance
Posts: 193
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Location: Cheney, KS

Re: RPM DROP

#2 Post by Marty Chance » Mon Oct 12, 2009 5:46 pm

the 900 rpm drop doesn't sound bad , but the recovery time does. This sounds more like the motor does not like the load on the shift (is it 1.80 p/g?) some cars struggle to recover the large split on a p/g. you may be able to help it some by raising the stall on the converter alittle but i would look elsewhere first.
what is the bore and stroke? cam duration @.050 and LS? is cam installed heads up or retarded or advanced? what is the compression ratio? how much timing? what rear end gear?
marty chance
Neal Chance Racing Converters
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top452
Posts: 9
Joined: Mon Aug 17, 2009 7:45 pm

Re: RPM DROP

#3 Post by top452 » Mon Oct 12, 2009 6:57 pm

Marty Chance wrote:the 900 rpm drop doesn't sound bad , but the recovery time does. This sounds more like the motor does not like the load on the shift (is it 1.80 p/g?) some cars struggle to recover the large split on a p/g. you may be able to help it some by raising the stall on the converter alittle but i would look elsewhere first.
what is the bore and stroke? cam duration @.050 and LS? is cam installed heads up or retarded or advanced? what is the compression ratio? how much timing? what rear end gear?
marty chance
Marty It is a 1.80 The bore is 4.350 and the stroke is 4.50 .The cam is 288int 294 ex with lsa 116 str up. 15.2 compression. 30degrees timing.The rear gear is 3.90 with 33 inch tire. Going thru traps at 6980. I think a 4.30 would help. Was still making power at 7500'and peak torque at 6300.I run methanol and someone told me I was running it to fat.

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

Re: RPM DROP

#4 Post by Marty Chance » Tue Oct 13, 2009 6:00 am

if you are too fat that will make the recovery on the shift bad. you may want to tune the fuel first. the 4.30 gear sounds like a good idea, but the fuel may cure your problem
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

top452
Posts: 9
Joined: Mon Aug 17, 2009 7:45 pm

Re: RPM DROP

#5 Post by top452 » Tue Oct 13, 2009 7:01 am

Marty am I correct in thinking I will have less slippage with the 4.30.Any thoughts on on how much that bad recovery could affect the ET or MPH Thanks Don

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

Re: RPM DROP

#6 Post by Marty Chance » Tue Oct 13, 2009 7:44 am

with a 4.500" stroke it may not be slowing you down as bad as it sounds. I would find out exactly where i am on my tune up first , then i would throw the 4.30 gear at it .
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

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

Re: RPM DROP

#7 Post by Marty Chance » Tue Oct 13, 2009 7:45 am

sorry , slippage with the 4.30 will be less
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

top452
Posts: 9
Joined: Mon Aug 17, 2009 7:45 pm

Re: RPM DROP

#8 Post by top452 » Tue Oct 13, 2009 8:27 am

Thanks Marty :thumb:

top452
Posts: 9
Joined: Mon Aug 17, 2009 7:45 pm

Re: RPM DROP

#9 Post by top452 » Mon Jan 25, 2010 10:01 am

Hi Marty. Engine guy said I should be shifting at 7600 not 7200. This would keep it out of the stall speed . How much do you think it will pick up? Also said a 4.57gear.Thanks Don

top452
Posts: 9
Joined: Mon Aug 17, 2009 7:45 pm

Re: RPM DROP

#10 Post by top452 » Mon Jan 25, 2010 10:06 am

He also said I should be going thru the traps at 7800.

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

Re: RPM DROP

#11 Post by Marty Chance » Mon Jan 25, 2010 2:05 pm

the gear change and higher rpm will help , you are on the right track
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

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