exhaust questions

[cerberusiam]

Thanks. I didn't know rips company name.



I looked around there. The kit he shows has a 3" down pipe. So I scratched him from the list.

Just curious why you want a 4" DP?



With a good flowing 4" from the DP back I have to question the need for a larger DP, other than trying to match to an HX40 style turbo.



I have not seen any evidence the gain is enough to warrant the price/hassle unless one is on the ragged edge.



Just wondering.

 

[goldminer]

Stan's is the place you need to get your Stainless Steel Exhaust kit from. I got a 4" SS system from him. It fit like a glove and we know how tight it is by the 205 tranfers case. I was very pleased with it. The only thing I didn't like was the 4" clamps. I got some ss band clamps to replace the ones that came in the kit. Just put all the pipes in place before tighting anything up. That's my two cents worth.

Roy Arnold

Phoenix, Az

 

[Philip]

Cerberusiam the 4" gives me better upgrade options later on.



Which pipe size right now doesn't matter to much. But it will be the same size all the way back.



I am waiting for Stan to return my email to see if he can change a couple of items that need corrected because of my flatbed.

 

[Greenleaf]

There is a local truck here who had a local co. build a 4" system. Turbo back. All 4 inch. I had to modify it some time afterwards, due to the install of a different turbo housing and addition of the six inch stacks I built.



The pipe around the transfer case wasn't anything special. Looked like a couple of 30° elbows welded together. There was even room left over.



I would replace the DP regardless of the size. It may look ok, but it will fail (crack) sooner or later. I just built a 3. 5 inch syestem turbo back for my 90 and the otherwise good looking OEM DP was cracked and split apart.

 

[Philip]

Scott this is the 3rd down pipe I have put on this truck. I know about the cracking. Thats why I am looking for a complete system. I want new all the way back.

 

[flathead6]

Texas Diesel Shop had a group buy earlier this year, but they had fitment problems with the downpipe and around the T-case.



Daniel

They did, they used a 5 speed for the prototype and it didn't fit the autos. BUT, they are looking for a 1st gen 4x4 automatic to test fit a new down pipe.



They need a volunteer thats near Dubois WY (or willing to drive) with a 4x4 auto to let them install a FREE Oo. 4" in order to get the DP right. They'll even put you up overnight!



The DP is a 3. 5", rest is 4". Good opportunity for someone in the neighborhood!



Philip, they would probably even turn the tail pipe like you wanted if you could travel there.



I've been in contact with both Texas Diesel and Pinnacle Exhaust about this issue. All we need is to get an auto 1st gen 4x4 in their shop to build one right. Seems that all they can find are manual trannys out there.



Any volunteers? PM me if interested.

 

[Philip]

flathead I know they are looking for a truck to fit an exhaust onto. But it is a 1450 mile trip one way. Plus about 3 nights in a motel. I can get a setup cheaper by mail order. If they were around 750 mile one way I would go.



I just did a 750 mile one way drive on tuesday and thursday this week. Monday was a 500 mile one way drive.

 

[bgilbert]

I don't see a benefit with a 4" downpipe if you don't have a 4" turbo outlet, JMO.



I noticed in the my local phone book a HD/MD truck shop that says they custom bend 4". I plan to pick at their brains next weekend or so for a system for the 91. 5. If the price is equal to or greater than the 'bigexhaust' brand, I'll probly just go with BE.com brand. If it's a good deal, I'll definately let you know Philip.

 

[MMiller]

I don't see a benefit with a 4" downpipe if you don't have a 4" turbo outlet, JMO.

This is what I know. On my brothers 94, we removed the stock 3" exhaust that had been straight piped. We put on a 4" turbo to tailpipe exhaust, on his bone stock p-pumped 5 speed truck. Even with the 3" outlet on the charger, he noticed greatly improved spool up and throttle response. He did not have gauges at the time, but he can run 370's, stock charger, and lots of smoke out of the stacks, and have no pyro problems towing horses in the mountains. I also have seen Joe Donnaley write on here that a guy does not need 4" exhaust until 500+ hp or something like that.





The rest of this is speculation, opinion, and other babble. I don't see the point of 4" exhaust if the first 4 feet of it are 3". I can see how the exhaust gases expanding, will benifit from a 4" downpipe, even thought the outlet is only 3". I guess a guy could also speculate to ask, what is the point of a 4" inlet to the turbo if you are only going to have a 3" exhaust?



Also, like I said before, I plan on ordering a system from Stans soon. I guess with all my gauges and current state of tune, I will be able to report on benifits of the kit. I won't be trying a 3" down pipe first though.



Michael

 

[Greenleaf]

Most of the school buses are Cummins and use the HX-35. Three inch exhaust into the muffler and four inch out. Probably some reason they developed the system that way. I don't know why... .



The IH DT466 is 3. 5 inch system into the muffler and four inch out.

 

[MMiller]

I've learned through the years that larger exhaust pipes are generally quieter, or more mellow. Whenever you can put a larger tailpipe, or larger diameter stacks, the tone gets deeper and more mellow. A 425 hp Cat engine only comes with 5" exhaust. If you put 5" straightpipe on it, it will be VERY LOUD and every law enforcement officer will request it gets fixed. If you put dual 6" straight pipes on it, it will be loud, but more mellow, and less frowned upon by the police. Dual 8" stacks will be very mellow and deep(until you throw on the Jake Brake at 2000 rpms )



I suspect that the designers of OEM are looking to make stuff quite, and keep people happy.



Michael

 

[dpuckett]

One must also consider that OEM is a compromise between performance and cost.





I did notice a little quieting of my 91 when I went from 3" straight pipe to 4" straight pipe.

DP

 

[Philip]

I just ordered 4" system from Stans. Hopefully the weather will warm up in a week or so. That way I can install it when it gets here.

 

[MMiller]

I think I'll intercept that UPS truck! Thanks Philip!



Let me know how it works out. Then you can come out and install mine.



Michael

 

[Philip]

I think I'll intercept that UPS truck!