DynoMax Exhaust

[docksider]

Hello Fellow Explorers -- I bought a Dynomax Exhaust system (catback) that says it fits 93-94 4door Explorer would that fit my 92 4 door? Maybe with minors mods? Most Gracious -- Happy and Safe Independence Day!!!

 

[Anime]

The 17415 Dynomax kit is made for the 93-94, mostly because of the muffler, which was made just for it, and for the single muffler hanger design that changed from the 91-92.

It will work on a 91-92, simply by changing the rear muffler hanger to one from a 93-94.

However, what you want for a 91-92 4-door is the Dynomax 17430 kit. The big difference, besides the bolt-on fit with the stock double muffler hanger, is that the 91-92 is 2.25" pipe from the cat back. The muffler on the 93-94 is 2.00", and only has a 2.25" rear pipe.

If you can't find a full 17430 kit, you can always make it from parts. The front pipe is Walker #43470, the muffler is a Dynomax Super Turbo #17747, and the rear pipe is a Dynomax #45274. The rear pipe seems to be discontinued, so you may have to use the 93-94 pipe, which is Dynomax #45493, and have it modified with the double hanger or rig something up. You could of course just have an exhaust shop bend up some 2.25" tubing to make the rear pipe for you as well, but it would have crush bends instead of the mandrel bends of the Dynomax tubing.

 

[docksider]

Anime - Thanks for the quick response -- any disadvantage to using 2" instead of 2.25? I plan to take it to a muffler shop and have them put it together for me --

 

[Anime]

2.25" tubing flows a LOT more than 2". It's a surprising increase. Dynomax says the difference between the systems is minor but my butt dyno tells me otherwise. The 2" pipe in the middle of the 93-94 system is a bottleneck.

Even though I have a '93, I used the 91-92 front pipe and muffler, and the rear pipe from a 93-94 to make my exhaust. The difference from a 2" was very noticeable, especially in the 1500-2500 RPM range where the 4.0L makes it's torque and is mostly driven.

Part of the reason to use a Dynomax kit is so you can do it yourself. I would not take the kit to an exhaust shop to have them install it unless you don't work on your vehicle at all and know nothing about cars and have no tools. It's REALLY easy to install. The hard part is getting the old exhaust off, but it can be easier with a reciprocating saw if you just hack the muffler and rear pipe off, and unbolt whatever is left of the front pipe from the converter flange.

I would also suggest selling the 17415 kit and either trying to order a 17430 kit from an exhaust shop that sells Dynomax, or buy the Walker front pipe and 17747 Super Turbo muffler if the 17430 kit is unavailable, and have the shop either bend up a custom rear pipe, or use the 45493 pipe from a 93-94 and have them add the double hanger.

I'm sure the shop could install the 17415 kit, but I'd be concerned about how they'd handle the hanger difference. Some shops really don't care and know customers don't look under the vehicle to see their work, and you'll wind up with some sort of cob job hanger welded on there. The only way to do it right would be to get a stock 93-94 hanger yourself and bring it with you for them to install after removing the 91-92 double hanger. Every little thing adds up though, and exhaust shops seem to charge a rather steep rate for even the most minor things, so just be careful about taking the system to them to do everything. You might wind up dumping hundreds into what should really be a $150 DIY bolt-on system.

 

[runningred92]

The smaller diameter pipe you use puts more resistance on exhaust flow. I just replaced mine with a dynomax a couple months back and actually stepped up to a 2 1/2 inch pipe. Larger pipe = better flow = better MPG. Good luck!

 

[Anime]

Larger pipe = better flow = better MPG

Actually, no. Larger pipe isn't always better. What you want is the largest pipe size that maintains exhaust gas velocity at the RPMs the motor is driven at and made for.

You can get away with 2.5", but that's on the large side for the 4.0L OHV V6 in terms of daily driving and wheeling. 2.25" is just about right, which is why the bolt-on systems use it.

One of the reasons some people use 2.5" is to try and make up for the use of crush-bent tubing. The crush bends reduce the internal diameter at the bends to 2.25" or less, so if you're having tubing bent, then 2.5" tubing might be a good idea. Mandrel bends keep the internal diameter at the bends about the same as the rest of the pipe, so mandrel-bent 2.25" pipe, which is what the Dynomax systems use, flows better without having to increase the diameter.

 

[R&T Babich]

... The big difference, besides the bolt-on fit with the stock double muffler hanger, is that the 91-92 is 2.25" pipe from the cat back. The muffler on the 93-94 is 2.00", and only has a 2.25" rear pipe....

I got a '93 rear pipe in the junkyard and was surprised when I put it on our '92 that is was 2". We have since picked up a '93 (both are 4DRs) which still has the factory system and the pipe is 2" from the CAT all the way back.

 

[tweakedlogic]

I just replace my dynomax exhaust. It was 2.25 and had press bends. When I bought mine (7 years ago) Dynomax said all they had was the press bent tubes. They offered a 2.5", but it was press bent as well. I dealt with it. Since the exhaust has mass, it's going to follow the outside of the bend anyway, so it really doesn't make that big of a difference.

I've stepped up to a 2.5. Exhaust shops have gone up. I went to a buddy of a buddy, brought him the new muffler and he bent the pipe and all. $150 cash or $200 credit card. I was shocked. It cost me as much to buy the Dynomax kit, have it shipped, and installed with new cat 7 years ago.

 

[Anime]

I got a '93 rear pipe in the junkyard and was surprised when I put it on our '92 that is was 2". We have since picked up a '93 (both are 4DRs) which still has the factory system and the pipe is 2" from the CAT all the way back.

They may have gone to a 2" in '93 to get a bit more low-end torque out of the motors, but I think it was due to costs. Ford's exhausts aren't that great, they still use mild steel tubing, when lots of other manufacturers use stainless steel and large tubing in their factory systems.

I just replace my dynomax exhaust. It was 2.25 and had press bends. When I bought mine (7 years ago) Dynomax said all they had was the press bent tubes. They offered a 2.5", but it was press bent as well. I dealt with it. Since the exhaust has mass, it's going to follow the outside of the bend anyway, so it really doesn't make that big of a difference.

I've stepped up to a 2.5. Exhaust shops have gone up. I went to a buddy of a buddy, brought him the new muffler and he bent the pipe and all. $150 cash or $200 credit card. I was shocked. It cost me as much to buy the Dynomax kit, have it shipped, and installed with new cat 7 years ago.

The crush bent stuff is from Walker, since everything Dynomax is mandrel-bent. Walker's crush bent stuff is even worse since it uses the rib-style of crush bends that puts wavy ribs on the inside of the bend. Exhaust gas does follow the outside of the bend more, but at higher RPM and velocity it uses the entire opening, and so the crush bend slows down flow compared to a mandrel bend.

The prices of exhaust stuff have more than doubled. 7-8 years ago, The Dynomax cat-back kits were about half the price they are now.

 

[docksider]

Thanks is and understatement - think I'll try to piece my system together starting w the 17747 (haven't been able to find the 17430) -- was trying to do it without the muffler shops but I know they have the lift and other equipment to make it quicker and easier -- you can always get useful feedback on this site -- Thanks again!!!

 

[Anime]

A lift makes it easier, but all you really need is a jack and a pair of jackstands to jack up the rear end to make it a lot easier to remove/install the rear pipe. It's also lots easier if you disconnect the rear sway bar link from the frame on the passenger side.

It'll also be a good idea to buy two new bolts for the cat/muffler flange, get the Dorman Help! ones at the parts store, the ones made for Fords are perfect, and heavier duty than the stockers.

After that just get the front/rear pipes and muffler. I'd also suggest getting stainless band clamps for the front and rear. I used these instead of the cheap u-bolt clamps and they are great. They cost a bunch, but you can re-use them over and over, and because they don't crush the muffler pipe, the exhaust is super easy to take apart the next time. If you use the U-style clamps they crush the pipe, and you'll never get it apart again, especially with the rust that develops between the pipes.

 

[docksider]

Thanks to all who replied - Anime, think I'll take your suggestion and piece together a 2.25 system with the chrome clamps - I've been puttin this off for awhile - think I'll toy with that -- Xplore On

 

[Anime]

You should be able to use a stock rear pipe of any brand from a parts store (Walker, ROL, etc.) since the stock pipe on 91-92's was 2.25". It won't have the mandrel bends, but it should fit perfect with the Dynomax 17747 muffler and front pipe (actually the front pipe could be of whatever brand as well, the Walker pipe is just a stock replacement and isn't anything special). In this case you're essentially just replacing the stock system and putting in a Dynomax muffler.

 

[sector9]

What about the cat? Anything you can do there? I've heard they will restricte lots of air flow!

 

[Anime]

The stock cats are fine and flow plenty as long as they are not blocked. Sometimes it helps to remove the Y-pipe from the manifolds and bang out a lot of the rust and scale that's in there, which gets trapped by the mesh in front of the converter assembly.

You can throw on a new converter assembly from Walker, Magnaflow,etc. (that will run you $200) or even a universal 3-way for less, but generally this doesn't do a whole lot unless you do a lot of other mods, everything from new, ported heads on the engine, to an air intake, headers, etc. If you throw a cam on there and up the powerband into the 3000-5000 RPM range then a much higher flowing cat will do wonders, but at that point you'd also want a higher flowing muffler, something like a straight-through design.

The stock or mildly modded 4.0L OHV does ok with the stock manifolds, Y-pipe, and converters. Really it's the muffler that is the biggest bottleneck, especially on the 93-94. The Dynomax Super Turbo muffler is perfect for this application since it flows more than enough for the low 1500-2500 RPMs the 4.0L sees.

On the '91-92, the stock replacement systems aren't too bad either, but the Dynomax gives a bit more flow. Unfortunately, Dynomax no longer makes the rear pipe for the 91-92 system so you can buy the Walker front pipe and 17747 muffler seperately, but you'll need to use a stock replacement 2.25 rear pipe.

 

[sector9]

Thanks!

 

[Corik]

I bought this #17415 dynomax cat back a little over a year ago. and I noticed the difference in the intermediate pipe size. but I put it on anyway and I used the U clamps that it came with.

So when I read this post I bought the #43470 walker pipe. I think I have an 2 and 1/4 inch to 2 inch adapter laying around. would I need that for the muffler?

I see the rust and I noticed the crush because of the U clamps, so do you think I would have a really hard time switching these out?
The pipe probably wont be here until Saturday.

 

[Anime]

The #43470 pipe is what you want when using the #17747 muffler for the 91-92.

The #43470 will not work with the #14697 muffler in the #17415 kit, because it has a 2" inlet and is at a different angle.

You could rig something up with an adapter, sure, but it won't help anything over the #42300 2" pipe because the muffler still has a 2" inlet which will be the bottleneck.

It would be easier to just use the #17415 kit as-is and simply swap the muffler hanger from a 93-94.

If you want the 2.25" front to back, get a #17747 muffler, use the #43470 front pipe, and either use the #45493 tailpipe that came with the #17415 kit by getting the double hanger welded on, or get a stock replacement 2.25" pipe for a 91-92.

Between the rust and crushed/clamped ends, you will usually not be able to remove them without damage to the muffler and/or pipe. If it's already mounted and secure I would leave it alone and not try to mess with putting a new pipe on the front for no good reason.