How many MPH from 1/8 to 1/4?

1369 Views 8 Replies 6 Participants Last post by TWIN86GNS, May 31, 2003

TWIN86GNS

Discussion Starter · May 31, 2003

On a mid 11 second GN how many mph should I pick up from the 1/8th to the 1/4? I have run a best of 11.38 and I have looked at some of my runs and I am gaining between 23 and 24 mph in the second half of the track, is this good??? Is this where I should be? Should I be gaining more MPH?

A friend of mine last fall gained about 25 mph in the second half of the track and he also went 11.38. I "believe" he went 97 mph in the 1/8 and then went 122 mph in the 1/4. eek!

We both ran race chips from the same vendor and I have never really been happy with my chips from this vendor. I have since switched to Jay Carter chips but I haven't run my fast car, only my street car with a Jay Carter chip and I am happy with it.

My questions are what should a mid 11 second GN gain in the second half of the quarter mile? What should a low 13 second GN gain in the second half of the quarter mile?

Thanks for any help,

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Steve Wood

· #2 · May 31, 2003

Paul...good question...I think about 124-125% gain.

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Jack Evers

· #3 · May 31, 2003

Here's one of the best runs in my car. MPH from 1/8th to 1/4 is about what you thought.

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Scottie-GNZ

· #4 · May 31, 2003

Rule of thumb with slight variances for gearing, 60', etc:

1/8-mile ET * 1.57 = 1/4-mile ET
1/8-mile MPH * 1.252 = 1/4-mile MPH

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TurboDave

· #5 · May 31, 2003

TWIN86GNS:
On a mid 11 second GN how many mph should I pick up from the 1/8th to the 1/4? I have run a best of 11.38 and I have looked at some of my runs and I am gaining between 23 and 24 mph in the second half of the track, is this good??? Is this where I should be? Should I be gaining more MPH?

A friend of mine last fall gained about 25 mph in the second half of the track and he also went 11.38. I "believe" he went 97 mph in the 1/8 and then went 122 mph in the 1/4. eek!

We both ran race chips from the same vendor and I have never really been happy with my chips from this vendor. I have since switched to Jay Carter chips but I haven't run my fast car, only my street car with a Jay Carter chip and I am happy with it.

My questions are what should a mid 11 second GN gain in the second half of the quarter mile? What should a low 13 second GN gain in the second half of the quarter mile?

Thanks for any help,

Maybe he's locking his TCC and you're not???

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Orlando_87GN

· #6 · May 31, 2003

I think the weight of the car, turbo size and converter slippage will have a big effect on this. I remember the Buick in mostly stock form was getting 21mph difference. Then a bigger turbo was netting 23mph difference.

Now with a healthy motor in this little RX-7, I have seen 30mph difference between the 1/8th and the 1/4mph.

A lot of factors to consider here... powersix

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TWIN86GNS

Discussion Starter · #7 · May 31, 2003

Thanks for all of the replies.

TurboDave both of us were running with locked converters, the chip locks it automatically at WOT in 3rd gear.

I looked through my log book a little more and I found out that I have some passes where I gained 26+ mph in the second half of the track. eek! eek!

My biggest gain was 26.76 mph. The other runs I was looking at I was locking the converter manually in 2nd gear and this run was the computer locking it from the chip in 3rd only.

Here is a pass:

RT 0.815

embarassing
60' 1.617 a little soft
330' 4.790
1/8 ET 7.444
1/8 MPH 93.29
1/4 ET 11.525
1/4 MPH 120.05 gained 26.76 MPH in the second half.

I guess I should try to get the car through the first 1/8th a little quicker. From what I have read if I want to go much faster I will either have to lighten the car (it is full weight) or put a larger turbo and injectors on it, currently it has a TE-44. I won't say what injectors I used to run the above pass (way too small).

If anyone see's any area's where the car isn't performing properly let me know.

Thanks for all responses,

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Steve Wood

· #8 · May 31, 2003

What are your egts in the 1/8th?

Looks like the fueling must be off to me on the bottom end. If I were to bet, I would say you were too rich in first and second. That is based on no facts other than the car is making horsepower on the top end.

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TWIN86GNS

Discussion Starter · #9 · May 31, 2003

Steve,

I don't have an EGT sensor in either of my cars, but I am strongly thinking about getting one for each car. I have been thinking for a while that the chip was rich on the bottom end, but it cleaned up O.K. on the top because we were running a small injector. I have cut numerous 60' times between 1.50 and 1.55 with both my Art Carr 9" and my stock converter. All of the above runs I listed were using the stock converter.

<small>[ May 31, 2003, 04:13 PM: Message edited by: TWIN86GNS ]</small>

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