hey guys........i was wondering if the Cut out was a proven Horse power mod? on lets say..a LS-1 and the LT-1's. i know they shure do sound nice but, do you think you are gaining or loosing Hp with it un capped? thanx!

 

The LT-1 was the old muscle car motor

The general rule is they add about 10hp give or take to a car depending on the application

 

i just installed mine. i lost alittle power down low. i think it had some effect on my gas milage though. or maybe my car is acting up again.

 

Dyno'd mine with it corked and uncorked at Detroit Speedworks a couple years ago. Lost 8hp when I took the lid off.
This was with a complete MAC exhaust, front to back. Headers, Y pipe, off road pipe and cat back.

 

timber......so you lost HP! that sucks! so why does everyone do it if you loose HP? i know they sound cool, but if your loosing power whats the point?

 

The way I understand it you have to install it in the correct place for it to work. It has to be as close to the rear of the headers as poss. Like installing a h pipe or x pipe. If it not in the correct place it doesn't work to the fullest gain I like the electric cut out ideal myself. Just hit a switch and it opens and hit it again and it closes. I have been thinging about one but after seeing what Timberwolf dynoed I don't think I will. I hear they have a problem with them closing all the way though. I hate exhaust leaks when they sound like a engine ticking. I guess you would have to find someone who does race exhaust systems and can install it properly. Also my car isn't that fast to were I can afford to give up any HP.

 

When I had mine Dynoed capped vs. uncapped I had a slight inrcease of 4 H.P. that was with SLP shorties , B&B TRI-FLOW,K/N,
and the free mods . So it was an increase but not what I was expecting

 

On my 1994 Z28 with MAC headers and SLP 2OTL exhaust I see no 1/4 mile time or mph gains with my cutout open. It seems to have no effect.

On my 2002 Z28 with stock exhaust it gives me 1-1.5 mph (0.1 sec or so) in the 1/4 which should be a decent horsepower gain. With an aftermarket exhaust, I doubt it would make much difference, though.

As for where to put it, I always heard the best place to put it is just before the intermediate pipe starts to go up and over the rear axle. That's where I have mine. You can actually have too little back pressure. That's when you start to see the hp loss.

 

Seems like I had mine right in the offroad pipe, or just ahead of it in the y pipe.

 

Perhaps I should elaborate a little further to see if maybe my setup is what made the difference...

My engine was completely stock save for bolt ons. I had never even taken a valve cover off. In fact, the only gasket surfaces EVER exposed were when I replaced the thermostat, and put on a 52mm TB. The car was naturally aspirated too.

I ran a best ever 12.80 at 108 with a 1.76 60' at m5. Shortly thereafter I dyno'd. I was expecting around 350rwhp. I got 285!

I was disappointed. But I think it was Dave at teh time who said... "Sometimes a combo just works well together..."

I had done the usual suspension work (LCAs, Panhard) and a MAC exhaust front to back, some extensive lt1_edit tuning (open loop) and a bunch of bolt ons (MSD, granatelli MAF, CAI, free mods, etc) and a bit of weight loss. Nothing special.

Maybe I lost power because I had just the right back pressure for the amount of exhaust CFM I was moving, and by uncorking the cutout I was reducing the efficiency of the exhaust. Perhaps a bigger cam would have produced different results?

[Linda Richmond] I'm getting a little verklempt! Discuss![/Linda Richmond]

 

on my wifes 2001 SS with cutouts it went from 13.4 to 13.1 with just the cutouts in the Y after the cats! cutouts do work if done right!

 

eh, I would challenge that statement to the point of modifying it to say, "cutouts do work if needed."

 

I put mine in right where the cat goes. I think it sounds just fine untill the open long tubes get here. Think i can make it all summer on open headers

 

You guys arent putting them in the right spots then............ THe guy that installs them in cincinnati, LT1's CONSISTENTLY see 2-3 mph increases as well as .1-.2 off 1/4 time!!!!!

 

Mine is way in the back in the bend going into the muffler. It made a difference at the track, but on a 14 second car it could have just been difference in conditions between runs. Plus I think it sounds like *** uncapped.

Lesson learned: No more cutouts for me thanks