Bear

iTrader: (1)

<strong> <img src="http://207.127.219.37/images/jprbear.jpg" alt=" - " /> </strong>[/QUOTE]
Hey Guys first let me start off by saying that I am overall pleased with my new setup. The car feels much stronger, the problem is it didn't run any faster. I Atapped the last run and here is what I found. The car was crossing the line at 5850 no higher. I have 373 and 26 10.5 16 Et Streets. Based on my graph, am I crossing the traps at too low of an RPM? Seems like it to me. I was thinking of a set of 410s for the car now. I have not had a chance to talk with anyone yet about this since I just got the last run logged. I would appreciate some input onnthis. Today the car 12.03@ 112.97 1.71'
Check Sig for full Details.

JS

iTrader: (4)

Bear its JS,I'll try and explain whats happening.
I've done this math on my car too.

MPH X GEAR X 336 DIVIDED BY TIRE SIZE
So u have 3.73 X 113 MPH X 336 DIVIDED BY 26IN TIRE

The math works out to 5450RPM threw the traps but u have an auto so u get some slippage from the verter.
Your particular verter is PRETTY DARN GOOD

According to your autotap reading u took,I'd say its only slipping 7% which makes it 93% efficent.Now if we alittle add MORE MPH to the car via more gear,then the math changes.

Let me show u...
U should pick up 1 to 2 MPH with the 4.10 so.....

4.10 gear X 115 mph X 336 divided by 26 = 6000RPM
Understand now buddy + about 300 rpm for slippage.
So u should run threw the lights at 6300.

I'd shift the car at 6500 MAX and try to cross at 6400 to 6600 if poss. but that will depend on MPH more than anything else,unless u gear it lower EG. 4.30 or 4.56

This gives u a safe trap rpm of 6500/6600 at 117/118 MPH.

Looking at your dyno sheet it reminds me of my own setup.Its peaking high,mine is ever higher than yours.One of the things I LOVED about my OLD S1 heads is they peaked at 6100.I think this has to do with the way GM designed the LS6 head in the first place.

So how do u cure it?
Well u could shift the car higher than 6500?But u might pay the price (I mightve hurt my motor).I will find out next week when I Ieak it down.

Or run more gear but that makes it less streetable.

IMO I would shift your car at 6500.
I would run 4.10/26 and take some weight out of the car
This should get u above 6200 rpm threw the lights.

The other thing is u could look at a cam that makes its peak alittle lower.I have been searching for one for a while now and still havent made a decision.


Good luck man....
JS

<small>[ March 23, 2003, 12:06 AM: Message edited by: JS ]</small>

2MCHPWR

iTrader: (10)

my less technical suggestion would be to also get 4.10 gears so that you cross the traps at (or near) your peak hp level. at least that is what i do with my m6; different logic for an a4?

Mike Hoffpauir

How tall are those ET streets really?
I would put 4.10's in your car to get the trap rps up. But, it will make the car more difficult to launch. You might need to put a 26X10 slick on the car to keep up.

What are your shiftpoints now? Looking at that graph I'd shift somewhere near 6500.

Bear

iTrader: (1)

Thanks for the input guys. Seems like we are all on the same page. As far as streetability is concerned, that all went away when I got Kim the SS. It is now the cruise around car. The new suspension for her car will make a world of difference too. The Hawk is now the Race car. I don't think 410's would be crazy. As far as switching over to a full slick I have no problem with that as well. Either way I am changing a tire at the track, makes no difference if its a ET Street or Drag. This sounds like a plan for me. JS the vertor is supposed to be 93 94% efficient, so your math is right on. I love the TCS over the vig. Car feels WAY different now than it ever has. it has a 2.7 STR and amn I love it. The funny thing is I picked up NOTHING in the 60' over the Vig3600. The car seems to drive better though as well. When it downshifts there is no more clunking sound as well. I plan on coming down to Atco as soon as I get 410s. All I need to do is find a vendor who sells them. See u soon. Bear
Hey Joe, Any thoughts?

ezss

Bear, I drove a friend's A4 with 4400 stall and 4.10 gears on the street and the car felt great. Suprisingly driveable too. We also raced to about 125mph and he was right there with me.

I would suggest raising the shift point/rev limiter a bit higher...your power curve looks pretty flat to me going to and past 6600 (slight dip), and that will leave you more time higher up on the power curve. 6700ish would seem better in my opinion.

I use 26 x 11.5 x 15 ET streets on bogart racing rims...seems to work pretty good for me, best 60 of 1.61.

It was like 70 around here yesterday too, Im sure that isnt going to contribute for best times. Good luck, keep us posted.

JS

iTrader: (4)

Bear,technically EZSS is correct.
U should be shifting at 6700 like I was (More like 6800)
But I WOULDN'T do it or u know what can happen.

Like I said,I might have a bad set of rings because of this now.Dont do it man,its not worth it..

Instead.....
Shift it at 6500,Run a 4.10/26 and take 150lbs out of the car.It WILL pick up 3 to 5 MPH

That u can bet on.
You'll go threw the lights where u need to,about 6400/6600 rpm..

Good luck bro
JS

<small>[ March 23, 2003, 05:31 PM: Message edited by: JS ]</small>

ezss

I think I did read that you were using 918 springs Bear, so just because of their track record alone JS is definately giving you the safe advise. You need a nice set of double springs, and then feel a bit safer about spinning the motor a bit higher <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Bear

iTrader: (1)

Erik these 918s are brand new. I swapped out the questional pair and got the blue stripes installed. I feel pretty safe spinning it up to 65-66. I would love to see my whole graph shift to the left about 400 Rpms. I think that would give me a more useable power band. Joe and I are already in the works for a possible solution. He would like to see what this setup can do first. I respect that. He took on a BIG challenge with this car <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> and hasn't backed down yet. In all fairness to Joe, My car & I are heavyweights, and Joe is a LIGHTWEIGHT. Between him and Tommy they should call the shop "Skinnies R Us". I think they need to get the munchies some how and eat a little. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> Well back to the drawing board. <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />

JS

iTrader: (4)

Aint that the truth Bear.
I take craps bigger than Tommy and Joe.

JS
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jfm

iTrader: (4)

JS,I used your math with my gear ratio of 3:42x121x336 divide by 26.4=5266rpm.That is very close.

Food for thought,4:10s will use up first and second gear a lot faster than,lets say,3:42s or 3:73s.

You will pull down the track in third gear 1:1 sooner with 4:10s and longer.You will increase your trap RPM but at the expense of using up first and second gear much sooner.

This makes me wonder how much real world ET is gained over 3:42s or 3:73s.I will be going to 3:73s and if everthing stayed the same on my car I would not expect to gain more than half a tenth and if 4:10s went in I would see more trap RPM but about the same ET reduction as 3:73s.

Just my opines,any comments appreciated.