Functional offroad exhaust mods

[winkosmosis]

My stock big round cat prevented me from installing a DPG belly skid plate, so I had a muffler shop replace it with a much slimmer Catco cat. I also had a 6" flex coupling put in to isolate the header and head from hits to the exhaust system.
I don't like the idea of a rock hitting the muffler or tailpipe and a long rigid exhaust system multiplying that force many times once it reaches the header and possibly damaging seals. I've heard of headers cracking too, so I think it's a worthwhile mod.

 

[Backwoods Rambler]

Very sensible mods. Good work! :costumed-smiley-007

 

[saburai]

Sweet!

Nice work!

Please post some pics of the skid installed.

 

[winkosmosis]

Will post an update after installing it.

Here is a pic of the clearance problem

Also, I want to extend the skid so it protects the whole cat, instead of just the frontmost 1". An old steel door from a full tower computer case (bent to match the skid) might work--- I know it won't support the weight of the vehicle but it would provide protection from stray objects

 

[Stumpalump]

Nice job! I had to have mine cut and relocated higher to install the same skid. Dirk at DPG was bragging about his life time warrenty on the skids and I said "Come on Dirk! Has anybody ever had a warrenty claim on that bombroof skid? He said "Nope". Then I ordered his bomb proof gas tank skid. Great stuff from a great guy:http://www.dpgoff-road.com/site/armor.htm

 

[winkosmosis]

Installing that skid is extremely difficult. I wouldn't buy it again if I had the choice. The frame and crossmember are HARD to drill. There is some strange material inside some parts of the framerails that you can't drill through. Even ignoring those, each hole takes about an hour. We got 3 bolts in so far today, and I decided to stop working.

Better to get a skid that bolts up underneath, so you only have to go through one layer of steel and put in a self tapping bolt.

 

[winkosmosis]

Got another bolt in, for a total of 4. 2 in the xmember, 2 in the frame.
Then the right angle adapter for the drill broke.

Unfortunately I think I gouged the hell out of the inside of the frame rails thanks to the drill bit walking. I'm afraid I've left the frame much weaker. I don't know what to do now. There is no way to see inside, so the only thing that will make me trust the strength of the unibody is reinforcement. This is the most expensive skid plate install imaginable....

I really wish that DPG guy would tell people how difficult it is to install his skid. I actually think he was dishonest about the rarity of the cat conflicting with the skid. Everyone seems to be saying they had the same issue with the cat, but Dirk said it's very rare.

 

[Root Moose]

Get a proper step drill bit. You can get them at Home Depot, Rona, where ever. Never had a problem drilling the rail using one of those.

Regardless of what you use make sure you use cutting fluid and the correct speed (IIRC ~900 RPM). Set an upright drill press to that speed to calibrate your eyeball to that speed if you are not sure what that looks like - read the placard where you set the speed to see what speed you need. There is normally a little table under the pulley cover that says "for bit diameter X use speed Y".

Again, Home Depot, Rona, etc. will have upright drill presses that you can "try out" to see what that speed looks like.

If the steel on the tip of your bit turns blue you've just destroyed the bit by getting it too hot and taking the heat treatment out of it. This is when drill bits don't work any more... Well, it might work on wood.

HTH

 

[Root Moose]

Btw, what year is your Jeep? By looking at the shape of the frame rail stampings I'm guessing one of the later ones (i..e. `97+)

Did the earlier Jeeps have a smaller catalytic converter? Was the exhaust routed closer to the floor in the earlier Jeeps?

Just curious if the issue you had is due to vintage of Jeep.

 

[winkosmosis]

Get a proper step drill bit. You can get them at Home Depot, Rona, where ever. Never had a problem drilling the rail using one of those.

Regardless of what you use make sure you use cutting fluid and the correct speed (IIRC ~900 RPM). Set an upright drill press to that speed to calibrate your eyeball to that speed if you are not sure what that looks like - read the placard where you set the speed to see what speed you need. There is normally a little table under the pulley cover that says "for bit diameter X use speed Y".

Again, Home Depot, Rona, etc. will have upright drill presses that you can "try out" to see what that speed looks like.

If the steel on the tip of your bit turns blue you've just destroyed the bit by getting it too hot and taking the heat treatment out of it. This is when drill bits don't work any more... Well, it might work on wood.

HTH

I was using a DeWalt titanium bit with a small protrusion at the front to prevent walking. But the big part of the tip isn't cone shaped, so I think that makes it much less effective. Someone on NAXJA suggested carbide bits. I think I'll get a couple Hitachi bits at Lowe's. If I see a good higher power drill I might buy one.

Thanks for the 900rpm tip. I've never seen cutting oil for sale though.

 

[winkosmosis]

Btw, what year is your Jeep? By looking at the shape of the frame rail stampings I'm guessing one of the later ones (i..e. `97+)

Did the earlier Jeeps have a smaller catalytic converter? Was the exhaust routed closer to the floor in the earlier Jeeps?

Just curious if the issue you had is due to vintage of Jeep.

It's a 1999. The earlier ones had a flatter cat, but I don't know if it was closer to the floor.

 

[winkosmosis]

I'm trying to figure out if I should be worried about gouging the inside of the framerails. I don't know how deep the gouges are but I think the worse case is maybe 1/2" above the correct holes.

 

[Root Moose]

Thanks for the 900rpm tip. I've never seen cutting oil for sale though.

You may have to look around for the cutting fluid. If you have a local nut and bolts kind of place (i.e. that is all they sell plus professional grade tools) that is where you'll likely find it. It'll be pricey but cheaper than bluing a lot of drill bits. The Walther [sic] stuff works nicely but is expensive. Must be having the labels in German that causes that. LOL

Our equivalent of Harbour Freight up here (Princess Auto) has cutting fluid for something like half the price. You go through at least twice as much fluid and it makes at least a twice bigger mess so I've given up on the cheap stuff.

Make sure you verify your speed. Your eye likely can't tell the difference between 900 rpm and 1000 rpm but it can sure tell the difference between 500 and 1500. Check the drill bit diameter to rpm chart. I'd google one but am too lazy.

Oh, one good way to make sure you don't over speed the bit is to listen for it "singing". If you hear a high pitched singing sound you are going too fast and/or need more fluid. You don't want blues singing drill bits. LOL - I kill me.

 

[Root Moose]

I'm trying to figure out if I should be worried about gouging the inside of the framerails. I don't know how deep the gouges are but I think the worse case is maybe 1/2" above the correct holes.

I'm not sure I follow what you are concernead about here... you mean like the drill walked while you had it powered for say 15 seconds at a time or whatever?

If that is the case I really wouldn't worry about it. A walking drill bit is not likely to do any real damage to the inner frame.

 

[winkosmosis]

I'm not sure I follow what you are concernead about here... you mean like the drill walked while you had it powered for say 15 seconds at a time or whatever?

If that is the case I really wouldn't worry about it. A walking drill bit is not likely to do any real damage to the inner frame.

Yes that's what I'm concerned about. Basically an extra hole close to the right hole. I guess the bit was dull anyway