Snake Skinner

I have the 3" Factory SS Exhaust for 98 which is a single 3" inlet and one single 3" outlet going through a 40 series Flowmaster Muffler. Back when I only had SLP LT's and a stall I picked up 19RWHP with the cutout open and now with the Head/Cam setup I picked up almost 34RWHP with it open. Like you said though there Trevor you have the SLP Dual/Dual and I am sure if I had the same exhaust I would show simular results, but I run with the cutout open all the time and have always done it that way. Just sounds good to me and much more powerful. A lot more Torque as well, but I'll have to look up on my dyno sheet to see, I know with it open I pulled 406/419 and with it closed I put 373/??? down.

<img src="graemlins/camaro.gif" border="0" alt="[Chevrolet]" />

Trevor @ Texas Speed & Perf.

iTrader: (3)

Brian,
Yeah, the factory SS exhaust isn't much better than the stock unit that comes on the "regular" LS1 f-bodies. That's some good info, though!

John02SS

iTrader: (47)

At our last dyno day a friend of mine with a 01 WS6 dynoed 326 with open cutout and 317 with it capped. Torque was also better with it open although I don't remember the #'s. I just don't have the heart to cut the B&B yet <img src="gr_grin.gif" border="0"> .

buschman

While your results are interesting I'm not sure if you can draw a solid conclusion from only two runs. So many factors could have contributed to a slower run the second time that would have nothing to do with the cutout. From my own experience I can tell you about my dyno results. I had removed my SLP Dual/Dual and replaced it with a Whisper aggressor and cutout combo. I picked up 4rwhp going from the Dual/Dual to the whisper(I forget how much torque was gained). I gained another 3 rwhp opening the cutout but lost 2 rwtq. Theoretically, with the lower torque/higher horsepower characteristics of the open cutout you should of had had an easier time hooking and a higher trap speed. But every car is different. Good luck with your tests.

Buschman

WILWAXU

iTrader: (6)

Yeah, I did the same test on both my cars... got a consistant 1mph increase in trap speeds. I hate comparing dynos.. but I saw a big increase there too TQ & HP.

11SECSS has run most of his 11.6 passes through a complete whisper cat back!

1dirtyZ

iTrader: (1)

just dynoed my car today, got 350 hp with the cutout on , the took it out and BAM! got 381 hp!!!
i was using a crappy flowmaster muffler though....
now who was saying a cutout doesn't help? <img src="gr_images/icons/wink.gif" border="0">

Lane

iTrader: (1)

On back to back dyno runs, before I had headers, o/r Y, and 02 simms, I lost 2 rwhp by uncapping my cut-out. I know the computer needs to learn, but I wouldn't think it would lose power to start with...

At the track, with the cut-out closed, my car went 13.15 - and on a different night in similar weather it went no faster than 13.30's with it open. Both times mods were only Nittos and lid.

However - now, with headers and o/r Y, my car was such a dog with the cut-out closed - I just cut the whole cat-back off. I now have a cut-off.. <img src="gr_grin.gif" border="0">

onfire

iTrader: (17)

Trevor, my numbers are like yours...through a dual/dual...... cutout open... I went 114.7mph and 114.6mph....with it closed it went 114.4mph twice...I lost 0.30 mph without the cutout...not much. The dual/dual is a very efficient muffler.

hankd

[quote]Originally posted by Trevor D:
<strong>I thought I'd post this since a LOT of guys install cutouts on their cars. I went out to Texas Motorplex this morning to TRY to get some runs in. I managed to get two in with no traction before it started raining, but those two runs showed some interesting stuff for open vs. closed cutouts.
I had an SLP dual/dual 3" catback installed, along with a cutout, this past Thursday to replace the loud 3.5" Mufflex. </strong><hr></blockquote>

Hey Trevor...I saw your car at Nick's on Wednesday when I was there getting my cutout done. Sweet ride! <img src="gr_stretch.gif" border="0">

[quote]Originally posted by Lane:
<strong>On back to back dyno runs, before I had headers, o/r Y, and 02 simms, I lost 2 rwhp by uncapping my cut-out. I know the computer needs to learn, but I wouldn't think it would lose power to start with...

</strong><hr></blockquote>

What's up Lane!! <img src="gr_stretch.gif" border="0">

CRASH 02

iTrader: (3)

Kinda off the subject. But on back to back dyno pulls my car made more hp with open FLP headers than through no cats and a open borla. It even made more power down low, which is what everyone says you will lose. I will try and post a dyno chart with the 2 runs so you guys can check it out.

Lane

iTrader: (1)

What's up Hank? <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

Trevor @ Texas Speed & Perf.

iTrader: (3)

Hey Hank! Thanks for the compliment. <img src="gr_stretch.gif" border="0"> Nick is a BUSY man, but he's well worth the wait!
As for losing 2 RWHP, I think this is just a variance in dyno runs. It's virtually impossible to get the same #'s every run. There are WAY too many factors that could contribute to a very small gain or loss like this. How much torque did it kill? If it was the same amount, I would say that you're making the same power overall w/ open FLP's vs. an ORP and open Borla.

Kristi

Trevor-
Having identical short times on the two runs, if ANY other factor (like weather) played into the difference in your ET, wouldn't AutoTap have shown where it was? Just curious <img src="gr_stretch.gif" border="0">

Trevor @ Texas Speed & Perf.

iTrader: (3)

[quote]Originally posted by Kristi:
<strong>Trevor-
Having identical short times on the two runs, if ANY other factor (like weather) played into the difference in your ET, wouldn't AutoTap have shown where it was? Just curious <img src="gr_stretch.gif" border="0"> </strong><hr></blockquote>
You're absolutely right. I was logging IAT, front O2's, KR, RPM's, blah blah blah, and it was all virtually identical on both runs. I make sure to have the engine temp right around the same (180) when I launch. I even had my electronic weather station at the track with me, and the two different runs showed a density altitude difference of 10'. I don't think that's enough to slow me down. <img src="gr_images/icons/wink.gif" border="0">

2quick4u

Trevor,

You can't exactly reduce exhaust system back pressure and run better times without a little AFR tuning help via MAF Trans unless you are already running way too rich. When I run my cutout open, I increase my WOT fuel by 2%. Without increasing the fuel, I won't see any gains. Your car was probably already running near optimum AFR or slightly lean with the cutout closed. Where did you mount your cutout?

I think you should retest your cutout while using a MAFT to increase your WOT fuel. You will see a gain. I usually see about .08 ET gain and at least .5 mph increase. I run a Dynomax UltraFlo Race Welded muffler, and if there is any better flowing muffler out there for our cars, I seriously doubt it.

Trevor @ Texas Speed & Perf.

iTrader: (3)

John - thanks for the info. I'll have to try it sometime. My O2's were pretty identical from run to run, FWIW. However, I know that they're not 100% accurate. My cutout is located at the back of the exhaust system, right before the pipe curves around to enter the muffler.

Dope

iTrader: (2)

I've got a 3" catback with a Dynomax 17227 muffler (similar flow rates to the stock dual/dual).

On back-to-back runs, opening the cutout gained .6mph and a slight ET improvement. Since then, I have averaged about .7mph better, and maybe .03-.04 better. Previous best before the cutout was a 13.33@105.5. Best after was 13.29@106.28. I've run as fast as 106.67mph. Definitely helps (stock motor with a few bolt ons).

Dope

DriveATransAm

nittos, skinnies, cutout open= high 11s every pass

nittos, regular tires in front, gf, tools, and extra tires in car, cutout closed= 12.4. <img src="gr_stretch.gif" border="0">

thats all i have to compare.

Trevor @ Texas Speed & Perf.

iTrader: (3)

It's definitely different for every car. Just look at the mixed results we have posted. Keep in mind that I'm only making my claims on the SLP dual/dual vs. a cutout on a stock-internal LS1. It's a given that you'll see a gain with all of the bolt-ons and a cutout with the stock catback, and the same goes for any internal work.
I'll have dyno #'s and more track times sometime in January to show what's working best for my setup.

WICKED SS

iTrader: (36)

Question???

Is the Loudmouth pretty much the same as having A cut out?