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  #31 (permalink)  
Old 10-20-2005, 01:37 PM
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I would like to add one more thing.

Most people worry about POWER, when they should be concentrating about getting down the track.

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  #32 (permalink)  
Old 10-23-2005, 12:32 AM
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Finally got my new acceleration program debugged. Wrote it in HTML and JavaScript, mainly as an exercise, as I'm trying to learn JavaScript. It "skews" a generic torque curve to match the peak torque and rpm (at peak torque) figures that are input. It adds the equivalent mass due to rotating inertia and uses a generic force required curve.

With the 3.0 axle, I got pretty close to your figures:

15.014 seconds at 91.875 mph

With the 3.8 axle:

14.64 seconds at 92.41 mph

So, you were a tick slower than you should be, perhaps, but it's not all that far off. You definitely shouldn't be slower in the second furlong, as xntrik pointed out.
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  #33 (permalink)  
Old 10-23-2005, 05:14 PM
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Billy
Good deal.
I don't have a program. Check this out, please.

What I was figuring is the conversion factor for 1/8 to 1/4 mile. Which varies from 1.56 to 1.60 (NHRA) depending on whose is used. These factors are actual observed averages from many time slips. It also depends if the car is 1/8 geared or 1/4 geared. An eighth geared car will be over the peak running the quarter.

Old gear 15.073 actual with 9.753 eighth x 1.56 = 15.215 theoretical.
Based on his actual 1/8 time he was faster than theroretical.

New gear 14.856 actual with 9.511 eighth x 1.56 = 14.834 theroretical.
He is actually close to the theoretical 1/4 time, only .022 slower.

BUT...... in the second half... old = 5.320 / new = 5.345
His new second half was .025 slower than the old gear.

He should not be slower through the second 1/8 with the new gear??????

Aerodynamic drag is still the same (theoretically) so the only explanation for being slower is.... over the power peak.

You and I both agree that he should be mid 14.6xx.

What is this factor telling us? mmmmmmmmmm

What do you think....???????

A.A.Y.A.

Last edited by xntrik; 10-23-2005 at 05:37 PM.
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  #34 (permalink)  
Old 10-23-2005, 05:26 PM
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so what your saying is maybe I souldve went with the 3.55 instead of the 3.80. that im hitting my rpms to fast and running out of power. cuase I think this is the conclusion im coming up with.
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  #35 (permalink)  
Old 10-23-2005, 08:59 PM
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Quote:
Originally Posted by voodoosurfer
so what your saying is maybe I souldve went with the 3.55 instead of the 3.80. that im hitting my rpms to fast and running out of power. cuase I think this is the conclusion im coming up with.

weeeeellllllll..... Now you have a car that you say is hard to drive on the highway and doesn't do what you want in the quarter...

there are a lot of variables in 4 years....

We're only talking 20 hp
a 3.55 gear is not going to make it quicker by any practical amount
I would suggest= 1 through 4 are mandatory

1) cold air intake
2) run through a good parts tuneup.
3) make sure distributor advance curve and carb are dialed in.
4) make sure the trans is not slipping.... it could be undetectable in 3 gear

5) find 20 hp above 3800 rpm. change carb and/or up-the-cam
6) get an AOD
7) live with it like it is, or go to 2.80/3.00 gear
8) build a drag car

It's up to you.

www.readershotrods.com drag cars/ georges
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Old 10-23-2005, 09:20 PM
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No, no, no! You definitely don't want to go in that direction. If you're turning 5000 in the traps, that's about optimum for an engine that has a torque peak at only 2600 rpm. Of course, you're winding beyond the power peak,but that's expected for optimum quarter mile performance. You treat it the same as if you were about to shift into another gear. I would expect your transmission shifts are between 4500 and 5000.

As for predicting eighth mile performance, I'm still optimizing a relationship, but it looks like eighth mile speed is about equal to 190 times the cube root of the ratio of flywheel horsepower to weight. The relationship for quarter mile performance, developed by Chrysler's George Wallace is:

quarter mile speed = 225 (horsepower/pound)^0.318
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  #37 (permalink)  
Old 10-23-2005, 09:42 PM
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well as of this last weekend I instaaled a 750 to replace my 600 and reconfigured my timing curves. I am not sure how I would rig up a cold air intake but that is a thought. and as far as my tranny, well that could be something. other than my shift kit and stall, it is a original 1970 C4 so there is a very good chance that it is slipping and im not noticing it. the fluid doesnt smell burnt or have any debree in it. I really want to get a AOD but dont have 1200 bucks to spend yet. SO I know where I need to go from here I guess. oh and im saving the full blown drag car for when and if my son hits 15 and wants to start racin with me. givin all the info here I think its a combo of my tranny being old, under carbed and needing one more gear to get me where I want, but then I will want faster of course.
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  #38 (permalink)  
Old 10-23-2005, 11:36 PM
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A shift to 3rd under high rpm and high accelerative and aerodynamic loads, it can slip just enough to hurt the time, but never make a mess of the oil, which is a function of temperature. Use Mobil 1 fluid and Lucas. Makes a difference.

Grab an AOD from a late 80s Crown Vic-Town Car. 89-90 Vic-TC is the best, even better is 90-92 HO engine Mark 7 like Mustang is the best... The later ones have a slightly lower first gear ratio. you need a different balance flexplate. Most of them run 180,000 miles with no problems unless the TV cable has gotten disconnected. They bolt right in with maybe a drive shaft length adjustment. They are are on the light duty side but have NOT been abused mostly. Grab one for $ 200 yard price and put it in. I have a beater 90 Town Car with 236,000 on it and it shifts like new (Mobil 1 ATF since 70k) These cars only had 160 hp 5.0 and grandma drove them so the trans is ususally OK. In the yard, if the fluid is ok and the tv cable is hooked on the throttle body, it is probably useable. Put her in. If it is ok after 200 miles, switch to Mobil 1 atf, and slip in Lucas. Rebuild it later.

Remember an AOD only uses the torque converter for 1 and 2.... not 3 or 4 gear. The governor rpm should be ok for your engine.

AOD will make your 3.80 feel like a 2.73..... cut your rpm from 3200 to 2160. That ought to help the cruise. You will like it.

Been there, done that.

pm if you need me.


www.readershotrods.com drag cars/ georges
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