JasonsSS

Truckin magazine dynoed a stock 2001 2500 HD with 6.0 and auto tranny. They then installed the Magnaflow stainless steel exhaust system, which retains the two 3" pipes into a muffler, and a single 4 inch pipe out of the muffler. They did the install and dyno at Car Sounds/Magnaflow shop in CA. They supposedly gained 16 rwhp and 30 rwtq with only the exhaust system. Baseline was 255 hp at 5100 rpms, 296.4 rwtq at 4500 rpms. After exhaust, 273.5 rwhp at 5100 rpms, and 326.9 rwtq at 4500 rpms. I have a 2001 2500 HD 4x4 6.0, auto, 4.10's, with ASP ud pulleys, volant cold air intake, free mods, etc, and wouldn't mind doing the muffler back exhaust system, if it really gives this much gain. But I'm a little skeptical that the stock dual 3" in and 4" out exhaust is really that restrictive. Anyone care to comment?

Thanks,
Jason

GREGGO

iTrader: (2)

The numbers are believable, (a little high IMO) on a bone stock motor. I'm gonna go back and read that one. They also say in the advice section that going with true dual will throw a code. I have had true duals for 3k now and no code, and know several with more miles and no code. I subscribe to the magazine, but I think there engine and drivtrain articles are sometimes misleading. Don't expect duplicate numbers. I would look for 8 to 14 and be happy with that.

JasonsSS

http://www.magnaflow.com/05magazine/05truckinb.htm

This should be a link to the article.

Fast4.8 - As you might already know, the 2500 HDs with 6.0 already have dual 3" from the exhaust manifolds down to the muffler. (the muffler has dual 3" inlets), followed by a single 3.5" pipe out the muffler. The only place I can think of as being a restriction is the muffler. The dual 3" pipes flow more than enough, as should the 3.5 inch tailpipe. I'm just wondering if there's some playing with the numbers on the dyno, as the dyno testing was done at the same place that is a distributor for the Magnaflow exhaust system.

1999stepside

I would not beleive all of the dyno numbers in magazines. I have watched some photo shoots and they faked a dyno, and when it came out in the magazine, it had a dnyo graph on it claiming 13+ horsepower. I am not saying all of them are fake, just don't believe everything you read.

JasonsSS

An independent shop or person needs to test this exhaust system then, to get unbiased numbers. Anybody care to do it? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

CMNTMXR57

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JasonsSS:
<strong>http://www.magnaflow.com/05magazine/05truckinb.htm

This should be a link to the article.

Fast4.8 - As you might already know, the 2500 HDs with 6.0 already have dual 3" from the exhaust manifolds down to the muffler. (the muffler has dual 3" inlets), followed by a single 3.5" pipe out the muffler. The only place I can think of as being a restriction is the muffler. The dual 3" pipes flow more than enough, as should the 3.5 inch tailpipe. I'm just wondering if there's some playing with the numbers on the dyno, as the dyno testing was done at the same place that is a distributor for the Magnaflow exhaust system.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The muffler is the restriction. It's the same setup as my 8.1. Unfortunately Magnaflow didn't come out with this system before I custom installed my Magnaflow's. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

They are both 3" center in on both sides. However, exiting the muffler, the driver's side is still 3" center out while the passenger side exit is 3" OFFSET UP exit out. Both 3" exits then flow into a 3.5" "Y" which then becomes 3.5" the tailpipe.

As such, I had to use two Magnaflow mufflers stacked on end. The driver's side is 3" center in and out and the one on the passenger side is 3" center in and 3" offset (in up position) out and then I merged them into the stock 3.5" Y/tailpipe.

When I get the chance, I'm gonna split them completely. I just need to find someone around here with a 3" mandrel bender.

GREGGO

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JasonsSS:
<strong>http://www.magnaflow.com/05magazine/05truckinb.htm

This should be a link to the article.

I'm just wondering if there's some playing with the numbers on the dyno, as the dyno testing was done at the same place that is a distributor for the Magnaflow exhaust system.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Well I'm sure they didn't just slap it on and pull one dyno and got those numbers. The numbers came from somewhere. Stock mufflers are very restrictive. It's basicly the same as catback systems that make similar claims. I'd have to ask when was the before number done, and how many runs did they take to get the lowest/highest numbers? Is the 16/30 on the same run ? When these reports are put into magazines that are IMO advertisers catalogs they are going to be a little biased about it.

JasonsSS

I did some investigating, and found that the article in Truckin magazine is a little misleading. The article states that a 2001 2500 HD with a 6.0 is used for the test. If you look closely at the pictures of the exhaust they are removing from the truck, that is not an exhaust from a 2001 Chev 2500 HD 6.0. I looked at my 2500 HD, and I went down to my local chev dealership and crawled around under quite a few new trucks, until I verified what I was wondering. The 2500 HD's with the 6.0 have a huge exhaust sytem from the factory, with dual 3" pipes going into one muffler (albeit restrictive muffler), dual 3" pipes going out of the muffler, which then wye into a single 3.5" tailpipe. The 2001 1500HD's with the 6.0 use a different exhaust system, much smaller. If you'll recall, the 1500 HD is the old 2500 rebadged. The 1500 HD uses what appears to be dual 2 1/4 pipes into the muffler, and then a single 2 3/4 tailpipe out of the muffler. A much more restrictive system than what's on the 2500 HD's. This would explain why they were able to get 16 rwhp and 30 rwtq from just the exhaust change. But if you have a 2500 or 2500 HD, you won't see anywhere near those #'s. It appears the best bet is to install that same muffler they used for the test, on the 2500 HD's, and leave the rest of the exhaust system alone. In fact, that's what I'm doing tomorrow, so I'll post back here on how it sounds, and also test it at the dragstrip Saturday (already have baseline #'s from this last Saturday).

Jason

Neil 6.0

I think you are on to something, but the factory exhaust pipes on 1500HD's is actually dual 2¾" diameter going into the muffler.

What caught my eye on the pictures is the rusty looking steel driveshaft. Don't 2500HD 6.0 trucks have a BIG HUGE aluminum driveshaft?

JasonsSS

Yes, the HD's have a large diameter aluminum driveshaft, not sure the exact diameter though. I could be wrong when I said the 1500HD's have dual 2 1/4" going into the muffler, as I didn't measure them, but they are much smaller than the dual 3" pipes on the 2500HD's, which led me to guess they were 2 1/4".

Jason