To start, I did a comparison of cut-out closed and cut-out open.
Right off the road with cut-out closed:
60Ft- 2.3
1/8- 9.737
MPH 75.28
1/4- 15.019
MPH- 92.75

The following run I opened the cut-out:
60 ft - 2.4 (Worse than first run)
1/8 9.669 (made up ground already)
MPH- 76.71
1/4 - 14.86
MPH - 94.49
So I almost gained 2 tenths and 2 MPH just from opening the cut-out. My car was tuned with vafc while the cut-out was open.

My personal best run of the night:
60Ft- 2.265
1/8 - 9.389
MPH - 77.8
1/4 - 14.503
MPH - 95.90
Using this da calculator: http://www.dragtimes.com/da-density-...calculator.php
My best run calculated out to be a 14.1 at 98MPH. My second best run was a 14.6 at 95 MPH an hour earlier which also calculated out to be a 14.1 pass at 98 MPH. For kicks I closed the cut-out for the last 2 runs of the night and ran two 15.0 passes again. So, in my case the cut-out is beneficial. Results may vary, but for me it was worth the $45 investment. The rest of my mods are in my sig. I'll be returning to the track in September and october for some cooler weather looking to improve my 60 ft's and hopefully get that actual 13 second time slip.

 

Nice runs man... appearently i need to watch my back for you too huh lol... hopefully with the calculations you get to reach ur goal.... nice run... practise makes perfect... keep at it

 

Nice runs. All these Auto's coming up strong...

 

My goal is 13's for now, but it's clear that I need a very cool day and a much improved 60 ft to get there. I'm also hoping to have a set of 16's with drag radials the next time I get to the track. We'll see.

 

I got a set of 4th gen SE 16's I can get rid of for 100$ plus shipping

 

what were your trap speeds on your last two runs with the cut out closed. if they were down significantly again then it's a pretty good back to back comparison of cutout vs no cutout. what exhaust do you have after the cutout, stock?

 

Last two trap speeds of the night were 92.5 MPH and 93 MPH. So trap speeds were back to being slower as well. I have stock cat-back after cut-out.

 

You have pm.

 

I just bought a pair of 16x8 wheels and ordered some drag radials. Hopefully that will help me get to 13's...if not, then spacers will be next. I've always said when I get my car to break into the 13's that's when I'll be done modding her and just enjoy and maintain it.

 

You're going to keep adding on parts till you're a mid 13 second car watch Good luck!

I've always said the same thing myself, as soon as I break 13s--I'll quit!!! Trust me, you'll get addicted again to going faster, just like you're addicted to break into 13s.

My car should be capable of it in cool weather, best I ran with intake/exhaust/SSIM was 14.4@100 (60ft needs improvement), before the recently added overdrive pulley and TS L-SPEC--might just have to bite the bullet and get headers, OR just gut out the stock ones and get a tune.

I need to be like you and get some track wheels instead of rolling on 19s, but I come to the track like you find me on the street. I'd invest in some cheap 16s, but all my extra funds are going towards my wedding next month .

 

thanks for comparing times with the cutout open and closed! this helps me a lot to make my decision lol

what was the temperature like? good runs btw, summer heat sucks

 

I've had a cutout sitting in my room that I've been thinking about putting on my girls car for a while now. I just might go ahead and do it.

 

Temperatures were near 90 all afternoon. Then when it got dark the humidity went up...Go figure.

 

humidity always goes up with a decrease in temperature.

 

i said the samething last year, if i get a 13.999 then im done, now im saying if i get a 12.899 then im done lol

 

But heat is still worse for performance than RH is correct? I'd rather run @ 60ºF/80%RH vs 90ºF/80%RH, do i have that right?

 

humidity has very little affect on performance. temp and barometric pressure have a huge affect.

 

+1 i agree... still affect it just a tad however

 

in case anyone cares, here's a little explanation about humidity percentages.

Relative Humidity is the amount of moisture that can be held by air of any given temperature. Hotter air can hold more moisture. That is why relative humidity goes up as temp goes down. if you have 40% humidity, that means that the air has 40% of it's maximum allowable moisture content. when the air temp decreases, that % goes up because colder air can't hold as much moisture. the AMOUNT of moisture in the air stays the same (expressed in grams/cubic meter or whatever), but since that cooler air is not CAPABLE of holding as much moisture, the given moisture content is a higher percentage of the maximum allowable moisture content.

anyways, you can play with a density altitude calculator to show this, but generally, given the same temp and barometric pressure, a huge swing in humidity will only change density altitude by a couple hundred feet. that's why it doesn't affect performance that much. a couple hundred feet is not much, as even a small change in temperature or barometric pressure can change density altitude by hundreds of feet, and large swings can change it by thousands of feet (temperature especially).

pilots have to do these calculations often, because the danger is very real that on a cool day you will be able to take off on a certain runway, but on a hot day the engine performance will be degraded to the point that you cannot safely use that same runway and you'll end up crashing off the end of the runway and digging a hole in the ground.

 

Wet bulb/dry bulb. I got a nice glovebox I need to maintain @ less than 1% RH ... Fun stuff...

Also have a barometer as well, and on days we're getting a storm (low pressure), my transfer chamber has a bit of positive pressure in it since I closed it when the pressure was typical, and tried to open it when the pressure went low, and sometimes vice versa. The readings on it are also relative, it's snowing outside, lower than 590, hot outside, 595.

But, back to our cars ...
barometric pressure > me

590mm/Hg here (~10.9 psi), I lose about 30% on a dyno (DJ) on a 60ºF day/typical baro day.


Also, RH does affect dyno corrections factors in the same way, small but noticeable in the values.

As in, typically people on here put down greater STD #'s than SAE, but not me, my SAE values are always greater (obviously RH dependent) than my STD #'s and it's because it seems to always be in the 8-12%RH range when I dyno.

 

Slight update...My nitto drag radials came in today, and my RX7 16's will be here friday. Looking forward to September when I can get back to the track. I'd go sooner, but I have 2 vacations coming up in August.

 

OH ISH MAN IM EXTREMELY JEALOUS!!!!!!!!!!!!!!!!!!!!!! goodluck... lemme know how u like em

 

Will do.