Ok, First off, don't ever dyno one of these things with a hangover...much too loud. I won't be able to post the actual dyno graphs until monday (if anybody wants to see them)because I don't have a scanner. There was nothing done to the truck other than the JDM Full length exhaust system (full length headers, high flow cats, dual magnaflows). Here you go...

Both on street side program:
Before exhaust (Actual): 433.0 RWHP, 542.5 RWTQ
After exhaust (Actual): 441.6 RWHP, 563.6 RWTQ

Street side:
Before exhaust (STD): 420.5 RWHP, 530.7 RWTQ
After exhaust (STD): 431.9 RWHP, 551.2 RWTQ

You can see a gain of 8.6 HP, 21.1 Lb/ft TQ (Actual) and 11.4 HP and 20.5 lb/ft tq (Using standard correction)

Now for the Race Side program (All after exhaust)...

(Actual): 447.2 RWHP, 576.5 RWTQ
(Std): 436.3 RWHP, 562.5 RWTQ

Pretty good numbers I think. Now I just have to get that power to the ground (and it won't be by using ET Streets) See this thread for F1's vs. ET Streets dyno comparison.

 

What mods do you have, aside fom the exhaust? The numbers for more highly modified trucks are better with the LTs and cats added than with those closer to stock. 420 hp is a good place to start for this part to really pay off. Good gains.

I'd bet the gains are even better under the curve than the peak numbers.

 

great numbers, I'm just curious, I am about to install my longtubes/cats this week, how much louder are they over stock headers/cats with a silver bullet?

 

From what I read, it varies based on how hung over you are.

 

That's the set-up I have exactly. There's no comparison! They are extremely LOUD! Definitely not for the 'faint of heart'. I set off car alarms regularly, just by driving by. I can't hear the blower whine at all.

The Silver bullet requires some modification to match up with the JDM headers and midpipes. Mine was about 4-5 inches too long when fully assembled. The tips wouldn't exit through the cutout in the ground effects. I think it must have been designed, as a catback only, for the stock midpipes and manifolds.

 

what did you do just cut the ends of the catpipe where it connects to x-pipe? has JDM updated the catpipe to fix this?
I'm going to order the cat-pipes on monday, i already have the headers, and the silver bullet is already on the truck, ill probably install everything on wed., I can't wait to hear it!

 

See sig
I can just compare to stock exhaust. At idle, you can barely hear there is an exhaust, but when you get on it, everybody knows. I love the sound, it is real deep and doesn't drone when cruising.
Totally agree. I didn't have any problem with fit.

 

Those are some great numbers
My gains where a little lower than yours, but your right about that noise factor at Crazy Horse.......YIPES

 

Ill tell ya...

Someone needs to make a true equal length long tube that starts at 1 5/8 and steps up to 1 7/8 before it meets a slip on collector. That slip on collector would have a firecone inside of it. You will see superior gains. I would pay $1800 for something like that. Hint Hint

 

You don't have the sig turned on.

I don't think you have the Silver bullet exhaust either. It is much more aggresive than stock at idle. The Silver Bullet has two cylindrical Magnapack mufflers as opposed to the dual oval shaped Magnaflows. The catback you received is designed specifically as a complete kit to go with the headers and mid-pipes from JDM. The Magnapacks are even louder. Maybe even too loud. Ouch.

I had to cut some from the mid-pipes so that I could slide the cat-back forward about an inch or so. I removed the ground effect that covers the exhaust area and then took it to a muffler shop where they cut the pipes that extend from the back of the Magnapacks completely flush to the muffler, and welded the exhaust tip assembly directly to the muffler. Perfect fit. Cost me $60.00 though.

 

I see the sig now. Only real difference in our trucks is the 4# pulley. I'll have to remedy that soon. What's a super flipper?

 

Superchips flip chip

Edit: I have the dual oval mufflers

 

I wonder how much of the hp gain is from the high-flow cats versus the long-tubes?

 

Peak Hp changes are not very inpressive adding long tubes, but if you look at the results HALO had when they did same day dyno testing you will see they gained over 30 hp around 3500 rpm. I will go back when I have time and get you the link. Its on the HALO site (WWW.HALOCLUB.COM) message board. This is the only reason I bought the JDM kit. I sure as hell hope the twin Magnaflows (not the round mufflers)in the JDM kit are not too loud!

Jerry

 

3500 rpms is where I made my largest gain, also. I only have a 2# lower and 1# upper; so, I didn't see 30 hp. More like 8-10.