ET improvement vs HP gain.
Thread Starter
Race Director
Joined: Feb 2003
Posts: 18,484
Likes: 1
From: Everyday you must choose between the pain of discipline and the pain of regret. Fredericktown, OH
ET improvement vs HP gain.
I am considering a heads/cam package on my LT-4.
The way it sits it makes 305 RWHP and has run a best of 12.93 on DRs and 12.94 on SZ50s at 108 and change.
The package I am looking at has made 370 RWHP on two different LT-4 cars.
I am a pretty decent drive and have literally made over 10,000 passes down a drag strip. So assuming I get the additional 65 HP and can get the car to hook relatively the same (with DRs this should be no problem), what do you think I can expect as far as ETs go?
I am thinking 12.30s - 12.40s should be pretty real. My local track is 1/8 mile and my goal would be to go in the 7s. My best 1/8 as it sits is 8.34.
Thoughts?
The way it sits it makes 305 RWHP and has run a best of 12.93 on DRs and 12.94 on SZ50s at 108 and change.
The package I am looking at has made 370 RWHP on two different LT-4 cars.
I am a pretty decent drive and have literally made over 10,000 passes down a drag strip. So assuming I get the additional 65 HP and can get the car to hook relatively the same (with DRs this should be no problem), what do you think I can expect as far as ETs go?
I am thinking 12.30s - 12.40s should be pretty real. My local track is 1/8 mile and my goal would be to go in the 7s. My best 1/8 as it sits is 8.34.
Thoughts?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
The rule of thumb for our cars is that 10chp gain is worth 1mph increase in trap speed and, potentially, .1sec off the ET.
If you have an A4, 17% DT loss is a fair guess. That would put your current power at ~360chp. Going to 370 hp at the rear wheels would bump you up to ~435chp.
That 75chp gain should be worth 7.5mph gain in trap speed and potentially .75sec off your ET, which is about your target.
However you may find that it takes slicks to hook up that much more HP & torque.
If you have an A4, 17% DT loss is a fair guess. That would put your current power at ~360chp. Going to 370 hp at the rear wheels would bump you up to ~435chp.
That 75chp gain should be worth 7.5mph gain in trap speed and potentially .75sec off your ET, which is about your target.
However you may find that it takes slicks to hook up that much more HP & torque.
Race Director
Joined: Jan 2002
Posts: 12,261
Likes: 85
From: O'Fallon Missouri
With 358rwhp, my car has ran.
12.38 @116, 1.88 60'
12.37 @115, 1.85 60'
370 rwhp should get you really deep in the 12's, if not high 11's.
Hopefully, with a better 60' time and the new camshaft, I'll be a little closer to an 11 second run myself.
-Mike
12.38 @116, 1.88 60'
12.37 @115, 1.85 60'
370 rwhp should get you really deep in the 12's, if not high 11's.
Hopefully, with a better 60' time and the new camshaft, I'll be a little closer to an 11 second run myself.
-Mike
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
If you can get a good launch, shift well etc. on a good day, high 11's and mid 7's in the 1/8 are quite possible. With my combo in my signature I have run a best of 7.6x at 92.xxmph in the 1/8 on ET Street slicks. But I am running a auto which makes it easier to make up for my driving skills. 
Oh, at that time I dynoed at 356rwhp on a generic chip. Hope to improve that a little with my new custom chip.
Oh, at that time I dynoed at 356rwhp on a generic chip. Hope to improve that a little with my new custom chip.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
There are many calculators around that allow you to calculate et's, rwhp, mph, weight, etc.
Not sure which one is best......use search engine here or google or whatever and play with a couple different ones.....
http://www.rpmoutlet.com/dyno.htm
http://www.smokemup.com/auto_math/index.php
Not sure which one is best......use search engine here or google or whatever and play with a couple different ones.....
http://www.rpmoutlet.com/dyno.htm
http://www.smokemup.com/auto_math/index.php
Last edited by LT4BUD; Jun 29, 2005 at 12:21 PM.
Burning Brakes
Joined: Nov 2003
Posts: 914
Likes: 1
From: Redding Ca
There are many calculators around that allow you to calculate et's, rwhp, mph, weight, etc.
Not sure which one is best......use search engine here or google or whatever and play with a couple different ones.....
I think we all tend to think our cars make more power than they do, until we actually make a pass down the strip as a reality check. So it is easy to dial in distorted data in a computer drag program. This is not intended to be a slam on anyone, it just seems to work out that way.
I use Quarter Junior and it is very accurate after I adjust the distorted data to match 60', 660' and 1320' performance. Launch RPM and peak HP Rpm are especially critical to get an accurate result. The weather data to key in also has a big impact. On the day you make passes, go by any dragster/altered trailer and ask them for the corrected air so you can have good data for the computer.
Once you have an accurate "base model" for your car, it is great fun to mess with tire sizes, gear ratio's, power curves, etc and a whole lot cheaper than paying for them first only to find out the have no impact or a negative result.
Not sure which one is best......use search engine here or google or whatever and play with a couple different ones.....
I think we all tend to think our cars make more power than they do, until we actually make a pass down the strip as a reality check. So it is easy to dial in distorted data in a computer drag program. This is not intended to be a slam on anyone, it just seems to work out that way.
I use Quarter Junior and it is very accurate after I adjust the distorted data to match 60', 660' and 1320' performance. Launch RPM and peak HP Rpm are especially critical to get an accurate result. The weather data to key in also has a big impact. On the day you make passes, go by any dragster/altered trailer and ask them for the corrected air so you can have good data for the computer.Once you have an accurate "base model" for your car, it is great fun to mess with tire sizes, gear ratio's, power curves, etc and a whole lot cheaper than paying for them first only to find out the have no impact or a negative result.
Last edited by GeosFun; Jun 29, 2005 at 12:04 PM.
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