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rklessdriver 08-20-2016 MPC Real Street Race
Senior Guru
Woodbridge, VA
1305 Posts
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2008/1/4 0:00



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Last weekend was just a total disaster. It was one of those days that makes you wonder why you even want to do this...

Car spun or rattled the tires on every hit. It also stumbled again going up on the trans-brake in E1 so I was stuck sitting there as the tree came down waiting for it to either backfire or clear itself out....

I've got to figure the engine stumbling/bumbling when transitioning from idle to WOT on the trans-brake out. Seems most prevalent once the plugs have a few passes on them.

I'm going to work on the carburetor and see what I can do with it. Seems to show OK on the AFR gauge but the plugs look terrible after driving it around the pit a little bit. I'm going to drop some fuel pressure out of it and play around with the float level to see if it helps.

Trying to get the 60ft down I wired my timing retard on a delay timer..... for the past 3 yrs I have been dumping timing once the nitrous comes on (instantaneously at launch) but with the big nitrous shot I am dumping so much timing (30*-15*) that the car kinda bogs for a millisecond then power wheelies..... So with this timer deal, instead of leaving on 15* of timing I am leaving on 30* of timing and then dropping to 15* after a certain amount of time.

I didn't know where to start so I started out with it set the timer to .8 sec.

That's a HUGE timing change for my car... I thought I'd be OK because with the progressive nitrous controller running from 15% to 50% over .5 second I'm killing a lot of power there.... So with 30* of timing during that time period the car should have a more power early in the run and 60ft real good.... but it seems to be way too much power because in Q1 it hit the tire rolled about 1/4 turn and a mili-second later blew the tires off. Went a 6.50@120 MPH

For Q2 I set the timer back to .5 sec and set the progressive nitrous controller down to 10% to 15% for .3 sec then 15% to 100% in .8 sec.

Car left and was rattling the tires really bad so I peddled until it hooked up which was about 100ft out. Another wasted run. Went a 6.05@121 MPH

For E1 I set the timer down to .3 sec and the Progressive Nitrous Controller down to 5% to 10% in .3 sec and 10% to 100% in .9 sec.

Going up on the trans-brake it stumbles/bumbles and acted up so I had to sit there as the tree comes down, my opponent leaves unchallenged.... while I prayed it doesn't backfire and catch on fire (yet again).... it cleared it self out in a second and I let if go.... it bogged for a millisecond at launch then power wheelies a little and goes down the track fine. 5.70@121 MPH with a 1.29 60ft.

So what I am thinking of doing is backing the base timing down some more.... I can only take 15* out with my ignition box and it's all in one step.... So I'm maxed out for timing retard now. Thinking of backing the base timing down to 25* and dumping 10*.... This will make the timing drop not so violent whenever it happens and it will make less power when using the delay timer on the timing retard at the same time as the progressive nitrous controller.

Only thing I worry about is getting the car cleanly up on the trans-brake.... less base timing isn't going to help that situation at all.

I don't have much time to deal with all this because we have a make up race Friday August 26.... Hopefully this works out better than last weekend.

Here is video of the race and qualifying.

https://www.youtube.com/watch?v=zVEBd6gt7Io

As always thanks Gurus!
Will
Posted on: 2016/8/25 15:14
_________________
1984 Corvette. 434 SBC with a Powerglide.
Best pass - 8.48@160MPH 1.23 60ft on MT 275/60R15 Radials.

1972 Corvette. LS5 454 BBC with M20 4 speed.
Best Pass - Doing good to just pass a gas station.
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BillH Re: 08-20-2016 MPC Real Street Race
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Reno
22702 Posts
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Good luck. Will.
I remember when tuning was easier.

We're having similar chit with our car (after 15 minutes it develops a miss at high speed). Test day on Saturday for us.

Posted on: 2016/8/25 15:37
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Every man dies but not every man lives.
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BrianCunningham Re: 08-20-2016 MPC Real Street Race
Senior Guru
Boston, MA for the most part :)
7754 Posts
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2007/12/30 0:00



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Best of luck

You're definitely a tuning expert
Posted on: 2016/8/25 23:08
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Polo Green 95 LT1 6-spd http://mysite.verizon.net/vzevcp74/
383 LT1/Vortech Supercharger/AFR heads/Rod end suspension/Penske-Hardbar dual rate coilovers/Wilwood 6pot brakes
NCCC Governor: http://BayStateCorvetteClub.com
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BillH Re: 08-20-2016 MPC Real Street Race
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Reno
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Good Luck tonight Will.
We're heading to the track at lunchtime.
Posted on: 2016/8/26 14:26
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Every man dies but not every man lives.
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Matatk Re: 08-20-2016 MPC Real Street Race
Webmaster
SW Chicago Burbs
21266 Posts
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2008/1/7 0:00



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Glad you're tuning it and not me! Good luck and I hope it works out.
Posted on: 2016/8/26 17:38
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1989 Corvette...custom 383 stroker, superrammed and cammed, built trans with PeteK 2800 stall. Mustang dyno results: 336 rwhp / 419 rwtq.
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