Question For The Drag Racing Experts: DA's & Trap Speeds (LONG)
 

This question is for the drag racing experts concerning my results from the 1/8 mile drags I usually attend.

My usual trap speed at my local track is around 78-80 mph in my near stock G. My mods include a Drop in filter, 5/16 Spacer (no mrev2, yes I have a revup and NEED the MREV2),Test Pipes, X02 Exhaust. Last night I ran WITHOUT THE X02 and bolted up the OEM exhaust paired to my test pipes. The TP's have an outlet of 2.5 mated to the small restrictive OEM Y-pipe which would hinder flow in that section.

DA's here usually run around in the neg's. Last night, DA's were around -660 which is normal for this time of year. Temps were about 5-8 degrees cooler last night. (50-51 degrees).

What's wired is that I trapped around 83-84 mph in the 1/8 which is VERY unusual. That's a gain of almost 5 mph in the 1/8th!

I was the only one in my group who had a big gain in trap speed. Others gained about 1 mph and they are N/A as well.

Do the DA's/slightly lower temp really effect trap speed THAT much?

:dunno:

yes temp and da affects racing very much so.

Possibly a malfunction....I trap 84 in the 1/8th. 5mph is basically a diff of 4k' DA.

What average DA are using for your "usual" 1/8 mile traps compared to your -660' DA last night? If the difference is great enough, 4mph difference is plausible.

5mph in the 1/4 is more than plausible, but in the 1/8th......I'm thinking a malfunction. Were the 60's the same?

My 60 ft times were pretty consistent. Ranging from 2.1-2.2 on my crappy 19" Goodyear Eagle RS-A's.

I'm going to consider this as a malfunction even though I have multiple slips. I'm only hitting 9.0-9.1 in the 1/8th. 5 mph is just too much of a gain in the 1/8 with one less mod.

What's weird is that I thought I was going to run a slower time since I was on the stock exhaust with TP's. I also had the spare tire in the trunk and a 1/2 tank of gas.

Thanks for the help guys.

When the DA is 2500' here I trap 81-82mph and at 0-(-)500 I am in the low 84's. So 3k' DA is about 2.5-3mph.

Everything effects ET and trap speed. An outstanding run is often accompanied with “Dang how did I do that?” A definitive answer is often impossible:

a. You made intake-exhaust changes which alter the horsepower and torque curves. Possibly a favorable alteration. Remember that a 1/8 mile racer is tuned for 660 feet. That is it. Who cares what the motor does after the finish line.

b. There are several density altitude - 1/8 mile - 1/4 mile calculators available. You can see that density altitude effect both. The effect on 1/4 mile ET and trap speed is greater of course.

My bad, I forgot he was talking about just the 1/8 mile trap. Yes, I agree with you that it probably was a malfunction.

Definitely a malfunction. Your car and my car seems to be nearly identical. Same 60', nearly the same mph consisten mph in the 8th, but my 1/8th time is a bit quicker. I'm in the low 9.0's and stock. I ran my car one night and at the beginning the DA was 800' above and my traps in the 1/8th were 79.7 average and later that night the DA's were -880 and my traps were 79.9 at best and averaged around there. Definitely a malfunction.

I will go out on a limb and say that your car MAY run better with the factory exhaust.

I got to the point of modding NA where my car was barely faster than stock ET wise down the 1/4 but it trapped higher. Same 60ft, same ET's, but I had extra trap with no improvement in time.

More mods untunued isnt helping your performance, so perhaps the mods + stock exhaust + good DA is the ticket to what keeps your ECU happy.

84mph is what I trapped in the 1/8 on my 13.1 @ 107mph run.

For comparison...

3200DA
2.162 60ft
8.786 @ 83.09mph
13.48 @ 104.74mph

-347DA
2.152 60ft
8.646 @ 85.35mph
13.19 @ 108.59mph

Your gain doesn't seem to add up IMHO.