I seem to notice more punch off the line with the cutout closed, is this a normal occurrence?

 

i seemed to notice the same thing.

and theoretically, the drop in back pressure could lead to a lose of low end torque. although i have never seen dyno proof of this.

i always figured it was mental...something to do with the louder noise making it seem like the engine should be pulling harder.

but the 10hp you gain on the top end makes up for it.

 

Sometimes when reducing the mean pressure in an exhaust system you can increase the pressure at that crucial moment of tdc. I've seen evidence of this in the book I'm reading right now. Why b/c your changeing the wave characteristics.
-b

 

How big is your cutout?

If you do a 2" cutout you don't lose as much bottom end.

 

Its a DMH 3" E-cutout.

 

Fix that intake leak yet?

 

I felt a little bit of difference in the very low RPM's but since I got the higher stall converter there is almost no difference, not SOTP anyway!

 

Working at a dyno shop I see a lot of different setups...a few years back a guy brought in a 99 LS1 SS auto...had a cutout and it put down 270'ish power...sounded pretty weak...he had left his caps at home so he could not cap it up, so I grabbed a couple of metal plates, vice gripped them up...next pull if I recall was like 300 rwhp...it was a big chunk in power difference.

I do remember this and laughing about it when he told me..."but I read on the internet everyone is gaining big power"...

But how many think LOUD = FAST

 

I haven't been to the dyno but I know I drop time in my ET with the cutout, I loose about 2-3 tenths between caped and uncapped, anyone who has a cutout will tell you the same thing, that guy must have had something else wrong! Or cutouts don't like dyno's! since it does pull a little TQ and we know HP on a dyno is calculated by TQ!

 

Hey Brent, I actually had the car in the shop (dealership) and the said my intake was leaking and we'll fix it for 650.00, I declined and said friends and I will fix it for a tube of sealant and some food and drinks.

 

Ouch! I'm assuming the dealership is probably "already in the KNOW" about how fun it is to work on LT1's, hehe.

 

Guys..........

There is a great magazine article in Pop Hot Rodding this month (May 2005) where David Vizard talks about exhaust systems and basically covers why you would lose power with a cutout etc.... It's not the cutouts fault but where it's placed along the pipes.

Magazines, the Old Skool Hot Rodders way to share ideas.

Bret

 

Mine is placed after the cat under the rear passenger seat, does that make a difference?

 

I got my cutout on the I pipe right before the bend over the axle. I gained HP/TQ and more MPH at the track. Deffinatly lowered my ETs.

 

well i can tell you from personal exierience, i dyno'd out at like 256hp and 306ftq, on my relativley stock 97 z28, that was with the cutout closed, we did 2 runs witht he cutout closed then we opened it and it dyno'd 266hp and 308ftq. Thats with my flowmaster catback. I'm thinking that it all depends on your catback, because if you already have a high flowing SLP LM or something similar your going to see less of a gain. My cutout is places right under the rear-pass seat. Its a 3 inch DMH e-cutout if it makes a differnece, if i can get my dyno graph scaned i'll post it up here for you all, but it has 11 runs on it so its hard to see anything. We were trying to tweak my nitrous system and did the first 3 runs for a baseline. The guy running the dyno was really suprised at how much i gained by opening it up.