Drag strip adventure: The sequel!

[Pranav]

So after last time's fun, I decided to take a crack at it again.

My best was a 15.22 @ 87.87mph. I also got a 2.17 60' and 0.0024 reaction time while running in a bracket

On my 2nd bracket run, I had to brake before the finish to avoid breaking out, although looking at the times leading up to the 1/4, I probably could've broken into the 15.1s.

After winning the bracket I tried manually shifting during the late night time trials to see if I could break into the 15.1s, but I just couldn't do it. I'd either bounce off the rev limiter by mistake, or just mess up in general. However, on my 2nd to last run of the night I set my best 60' (2.16), but slowed down just enough between the 330' and 660' marks to end up with a 15.24.

http://home.mindspring.com/~pranavyp2/1117DR.htm

It was a stock '03 Limited 2wd v8, with just a drop-in K&N filter. Temps ranged from the high 50s to high 40s. The only change made from the last event was the removal of the spare tire.

 

[Mark86]

Those are good numbers for an SUV! In addition, it sure sounds like you had a lot of fun. Where are you able to do this testing?

 

[Pranav]

It's a drag strip in Sealy, TX, just a little west of Houston.

 

[Mark86]

It's a drag strip in Sealy, TX, just a little west of Houston.

I wish I had a place like that in NJ! It would be interesting to see a comparison between your truck and an '05-'07 V8 and your truck with a '03-'04 4WD V8.

 

[Koz]

I wish I had a place like that in NJ! It would be interesting to see a comparison between your truck and an '05-'07 V8 and your truck with a '03-'04 4WD V8.

Englishtown!

Koz

 

[OUTRNNR]

Those are good numbers for an SUV! In addition, it sure sounds like you had a lot of fun. Where are you able to do this testing?

Especially with just a K&N filter as the only performance mod...

Its amazing the difference that altitude makes. I have probably 50 HP on you and the best I could muster was a 16.6 up here at 5800 ft. I need to run somewhere at sea level so I don't have to rely on conversions to correct for altitude.

 

[RonMAIDEN]

Yes,sea level is so much different. I ran steady 13.2s in my Eclipse up here and 12.5 down in Houston.

Also don't rely on conversions for altitude since that means little when it comes to what you actually will run asl. Coversion charts are for internet racers.

 

[Threxx~]

For what it's worth, I very rarely come across someone who has actually gone to the drag strip with their automatic transmission vehicle and shifted it manually and produced a better time. Typically the times range from the same to worse depending on how good their reactions were (since you typically have to shift a few hundred RPM before you really want to)

See people often think that the best possible time is shifting any car in every gear right before the rev limiter... but actually that completely depends on the power curve of the vehicle (particularly where your peak power is in the band and how flat the curve is before and after that peak), the gear ratio you are in now, and the gear ratio you are getting ready to shift to, and your rear and gear ratio.

I had a neat pretty accurate physics program on my last computer that computed an amazing number of variables called "cartest 2000" and it would actually tell you based on the above variables where it was best for you to shift. Granted it was almost always somewhere between redline and 600 or so RPM before redline. But my point is a properly programmed automatic transmission will SEE that you are at wide open throttle and it KNOWS when those shift points are. So if you see your vehicle in automatic mode shifted a bit before redline, there's a good chance it's doing that before that's the way it expects to achieve the best acceleration possible.

 

[Pranav]

I actually took that into account when decided where to manually shift, so I made it a point to go all the way to redline on the 1-2 shift, and let the PCM auto shift from 2-3. I did however leave it locked in 3rd gear instead of letting it shift to 4th before the finish, as I felt I'd lose more time letting it shift.

It's a moot point anyways, all of my good runs were made when I let the PCM do the work.

For what it's worth, I very rarely come across someone who has actually gone to the drag strip with their automatic transmission vehicle and shifted it manually and produced a better time. Typically the times range from the same to worse depending on how good their reactions were (since you typically have to shift a few hundred RPM before you really want to)

See people often think that the best possible time is shifting any car in every gear right before the rev limiter... but actually that completely depends on the power curve of the vehicle (particularly where your peak power is in the band and how flat the curve is before and after that peak), the gear ratio you are in now, and the gear ratio you are getting ready to shift to, and your rear and gear ratio.

I had a neat pretty accurate physics program on my last computer that computed an amazing number of variables called "cartest 2000" and it would actually tell you based on the above variables where it was best for you to shift. Granted it was almost always somewhere between redline and 600 or so RPM before redline. But my point is a properly programmed automatic transmission will SEE that you are at wide open throttle and it KNOWS when those shift points are. So if you see your vehicle in automatic mode shifted a bit before redline, there's a good chance it's doing that before that's the way it expects to achieve the best acceleration possible.

 

[Threxx~]

I did however leave it locked in 3rd gear instead of letting it shift to 4th before the finish, as I felt I'd lose more time letting it shift.

That's a good point - often times people DO see better performance by holding the last gear as they cross the line IF their vehicle is shifting into the next gear right before crossing the finish line and IF the TCU (I think the transmission control unit is what generally makes the decision using inputs from the ECU... the PCM I thought was the term for the interface that allows you to change settings on your car and read error codes?) is choosing to shift with some room before redline because it may be assuming that you're still going to be accelerating for a while and thus it doesn't know to just wring the gear out.

 

[Pranav]

Yeah, Honda calls there 2-in-1 ECU and AT controller a PCM (powertrain control module). Different acronyms for different manufacturers, lol.

 

[Fro-Runner]

Dang it! I wish somebody would run a 03-04 V6 Runner w/4 spd Tranny for quarter times on a drag strip.

 

[OUTRNNR]

I actually took that into account when decided where to manually shift, so I made it a point to go all the way to redline on the 1-2 shift, and let the PCM auto shift from 2-3. I did however leave it locked in 3rd gear instead of letting it shift to 4th before the finish, as I felt I'd lose more time letting it shift.

It's a moot point anyways, all of my good runs were made when I let the PCM do the work.

I tried manually shifting from 1st to second at the track last time I was there and when I shifted, nothing happened for about a half a second, enough time to bounce the rev limiter = slower times. Not sure if it was me or the computer, but I swear I shifted before it did...