I am hoping to get some info from members that are currently running straight-thru or straight-thru w/glasspack exhaust. I am wondering what kind of gain i would see in overall horsepower from turfing my stock 3.5 inch exhaust and 60 pound muffler and replacing with a 4 inch exhaust coupled to a glasspack stopping just short of the rear cab with a 90 degree tip dumping downwards. Any reduction in E.G.T.'s???. Any change in the powerband of the truck like significant loss of power in the low end??. How about soot issues...is it possible to pressure wash it off of my undercarriage every 3 weeks or so???

Thanks in advance...."Mad" Mikey

 

I have no experience, but I did stay in a Holiday Inn Express last night.

In theory you will not gain power unless you also add fuel via pump tweaks. The idea of modifying the exhaust is that it allows you to add the fuel without having as-severe EGT issues; it lets you make more power, but doesn't give it to you.

Aftermarket exhaust alone might make the engine a little more efficient, but you're only looking at a few horsepower tops. Coupled with the reduced weight, you're not going to find seat-of-the pants performance.

However, you will be able to add ~25-40 more HP worth of fuel without melting due to EGT's. That would be seat-of-the-pants performance.

Another thing is that I believe the glass pack muffler's aren't effective for use with Diesels. The soot in the exhaust likes to clog up all of the little glass-shards or whatnot and within a few months it looses most of it's muffer ability and restricts airflow to boot. Straight-piping would be best, but if you want a muffler, there are plenty of Diesel-designed mufflers available.

 

The Begle hit it pretty much dead on.

If you don't want soot under the truck, you are best off going with a full exhaust.

 

Considering all the mud and chicken feathers under my truck, a little soot would be an improvement.



Edwin

 

And why would you have chicken feathers underneath your truck???

 

On my early 91, I noticed a big drop in EGT, esp when towing or hard runs at WOT. Maybe 200+ deg peak (could no longer peg pyro, at least til I got new injectors, but that is another story). I also picked up some bottom end- boost came on 150-200rpm sooner. Why would you LOSE bottom end with bigger pipe? Also, you will get an incredible drone and LOUD cab noise without a full system. I had the tailpipe clamp come off my 91 (homemade system- had $50 in the whole thing), and drove it 100mi home without the pipe over the axle, and it was NOT fun.

Daniel

 

[QUOTE=dpuckett]On my early 91, I noticed a big drop in EGT, esp when towing or hard runs at WOT. Maybe 200+ deg peak (could no longer peg pyro, at least til I got new injectors, but that is another story). I also picked up some bottom end- boost came on 150-200rpm sooner. Why would you LOSE bottom end with bigger pipe? Also, you will get an incredible drone and LOUD cab noise without a full system. I had the tailpipe clamp come off my 91 (homemade system- had $50 in the whole thing), and drove it 100mi home without the pipe over the axle, and it was NOT fun.


YUP it is amazine how much noise ....that you can hear, become anoing with out the tail pipe!!!!!!
I servived 2 week before i said enought and had a tail pipe put back on!
wanted to whate till i could afourd the 4", all the way back but just couldn't take it any more!