'93/'94 exhaust versus '95-on exhaust

[mabrodis]

So from some pictures I have seen it appears the '93/'94 exhaust goes through the cats (two side by side in parallel, whereas the '95-on has two, one after the other, so in series) then goes up OVER the frame rail inbetween the frame and the body, then to the muffler and out the back. Is this correct?

On the '95 and later 80-series the exhaust goes through the two cats (one after the other) then UNDER the frame and to the muffler, etc.

Is this all correct? (I have only had '95 and later Cruisers)

I'm asking because I am desprately trying to figure out how to get my exhaust OVER the frame, which is not easy to do, there is a good area for it, but after the two cats you are too far back to feed the pipe up to the good area with some clearance.

So is there anything special about the '95 and later cats? Meaning, could I put '93 cats on my '97, with some mods ofcourse, but with that setup I think I could easily run the exhaust OVER the frame.

Or, other alternative is to go with only one cat, anyone know what bad things would happen? I know Kumar runs his '96 with no cats at all, just replaced them with a straight pipe, and his does great, no check engine light or anything...so...

Any ideas..
Mark Brodis

 

[cruiserdan]

93-4 are indeed side-by-side and the pipe goes over the top of the frame. The later cats put the outlet too far back to allow it to go over the frame. The earlier exhaust positions both O2 sensors in front of the cats, one in each pipe. You need a pre-cat and a post-cat.

You would likely want to find a single highflow unit that would pass emissions and be short enough to allow you to go over the frame.


Of course you could always dump it and buy a nice '93.....

 

[mabrodis]

Of course you could always dump it and buy a nice '93.....

Trust me I've thought of this, especially seeing the prices now for a darn good vehicle. So I wonder if I can make it over the frame rails with one cat...hmmmm....one is still A cat, so it should pass all the emission stuff...

Thanks,
Mark

 

[landtank]

Of course you could always dump it and buy a nice '93.....

Don't foget the solenoids.

 

[cruiserdan]

Don't foget the solenoids.

Already fixed tater....


Oh, I seem to still have my original headgasket tho....


(Now, watch it crap out on me on the way home tonight)

 

[RavenTai]

what does your emissions consist of on your 97? do they actually sniff the tail pipe or is it just an OBD-II scan?

 

[NorCalDoug]

Mark - I recall someone talking about going through the frame rail. I don't remember if it was done or not. The idea was to cut a hole in the frame rail, then weld a tube in place for the exhaust pipe to attach to.

 

[mabrodis]

Raven:
The emissions on the '97 consist of going to a building with a blue roof, paying a 14 yr old to drive your vehicle onto big rollers where they gun it trying to break something.

They do a tailpipe sniff while you're on rollers, so the vehicle's tires are moving at 30-40 mph or somewhere around that, so it's sposeto measure tailpipe emissions under real-world conditions. Since our's are fulltime 4x4, they have a seperate lane with rollers for front and rear wheels, and they measure your wheelbase then adjust the rollers to fit the vehicle.

Doug:
Hmm...I hadn't through about going THROUGH the frame, but that would be a possibility, and as long as you cut it then welded a nice sleeve in there really shouldn't be much weaker. I think what I'm going to do is remove the 2nd cat, so the exhaust will go through 1 cat, then up over the frame (I can still make that bend after 1 cat, just not after two)...atleast that is the plan.

Later..
Mark Brodis

 

[cruiserdan]

I would not cut or weld on the frame.

 

[bjowett]

I would cut and weld the frame.

I think it was my suggestion a while back(?).

 

[dclee]

That's why `93-`94 are the best years!

- no airbags
- beefy radiator
- beefy tranny
- exhaust over the frame rail

Oh, and I think I also still have my original HG after 146K miles!

 

[NorCalDoug]

That's why `93-`94 are the best years!

Bah!
(now stop coveting Unimogs and go help Scott with the wood dash trim thread! )

 

[Bob_Garrett]

Raven:

Doug:
Hmm...I hadn't through about going THROUGH the frame, but that would be a possibility, and as long as you cut it then welded a nice sleeve in there really shouldn't be much weaker. I think what I'm going to do is remove the 2nd cat, so the exhaust will go through 1 cat, then up over the frame (I can still make that bend after 1 cat, just not after two)...atleast that is the plan.

Later..
Mark Brodis

Wouldn't that add vibration and noise to the truck, since the exhaust is attached to the body using rubber mounts for isolation?

Bob

 

[Doc]

The only real way to pass an exhaust pipe through a frame would be to use a pipe about .5" larger. Cut the hole to fit the larger pipe, weld it it, and pass the smaller exhaust pipe through it. This would eliminate the frame heating and rattling associated with making the frame a part of the exhaust pipe.

 

[mabrodis]

The only real way to pass an exhaust pipe through a frame would be to use a pipe about .5" larger. Cut the hole to fit the larger pipe, weld it it, and pass the smaller exhaust pipe through it. This would eliminate the frame heating and rattling associated with making the frame a part of the exhaust pipe.

Yeah but have you looked at the exhaust when you start the engine, it usually moves alot more than 1/2" (or maybe it's just cause mine is broken.. ). It certainly could be done with a large enough hole in the frame however. A better approach I think would be to just put on a body lift, a 2" body lift would give plenty of room for the exhaust to go inbetween the frame and body just about anywhere you want.

 

[clownmidget]

just put on a body lift, a 2" body lift would give plenty of room for the exhaust to go inbetween the frame and body just about anywhere you want.

Mark, this is what got me thinking about the 1" body lift I posted a while back. I'm putting on a custom 3" exhaust with the turbo install and I'll be damned if I spend that much time and effort for it to sit in the stock location. I've even considered the BFH on the underside of the body near where the underside of the rear seats is. I'm not structural engineer so going through the frame isn't a real option for me since the truck sees a lot of high speed highway travel with the family. I think it will fit above the rail with the single cat but I am most worried about emissions afterwards. It's really strict in CA and only getting stricter. Right now I'm going with one new cat with new 02 sensors in front and back as close to stock locations as possible. The cats I'm looking at are about 16-17" long. Don't know where that puts you on the frame but hopefully in the right spot.
Mike

 

[RavenTai]

They do a tailpipe sniff while you're on rollers,

bummer, in GA they just do a scan on 96+ trucks, no codes=pass emissions, as as long as the computer is happy (or blinded to what is really goign on) you pass emissions, I was hopeing this was more universal

 

[mabrodis]

Mark, this is what got me thinking about the 1" body lift I posted a while back. I'm putting on a custom 3" exhaust with the turbo install and I'll be damned if I spend that much time and effort for it to sit in the stock location. I've even considered the BFH on the underside of the body near where the underside of the rear seats is. I'm not structural engineer so going through the frame isn't a real option for me since the truck sees a lot of high speed highway travel with the family. I think it will fit above the rail with the single cat but I am most worried about emissions afterwards. It's really strict in CA and only getting stricter. Right now I'm going with one new cat with new 02 sensors in front and back as close to stock locations as possible. The cats I'm looking at are about 16-17" long. Don't know where that puts you on the frame but hopefully in the right spot.
Mike

That's funny you mention the BFH, I was down at Meineke last night, just to have them look at it and see what they thought, the guys was under there for awhile, we were both laying on the pavement looking at different things, seeing how many times I can burn myself on the cat and still be dumb enough to hit it again censor: that hurt!). He mentioned about beating up the floor, but not a great place to even do that, plus it's a bit of a jerry-rigged approach he thought, which I agree. I had thought of the body lift previously and he strongly suggested that.

I asked Shawn Jackson ('94 with 3" body lift) about the body lift, he said it wasn't overly hard, he said if only doing a 2" or less it would be alot easier than his. He said the last inch was a pain and required alot of mods to the radiator brackets, and such, then ofcourse anything frame-related (sliders, bumpers, etc) don't look right because they sit lower than the body now.

I think I'll breeze through the emissions since I'll still have one cat under there, so when they put their little mirror stick under there to look, they'll see the cat and be fine with it, ofcourse then there's the actual tailpipe sniff test, which I guess I could be getting different numbers with only one cat, but time will tell there. I'll check about sliding the first cat further forward too, that might be possible, just not alot of room to work under there. I looked up some aftermarket cats which were alot cheaper than I thought, tempted to get one that's larger that my stock ones and put it as far forward as I can so I can still get over the frame but have as big of cat as I can fit.

 

[NorCalDoug]

I'm no mechanic or emissions expert, so I don't know...but is there any reason that the cats have to be right next to each other? Couldn't the first cat be in the stock location and have the 2nd cat farther back? If so, you could route the pipe after the 1st cat over the frame rail, into the 2nd cat, then into the muffler and out the back.

Would this work?

 

[mabrodis]

Not sure, I thought of the same thing, it would probably put more heat under the vehicle, since them damn cats get hot (an my elbow shows it!). If I do the setup I'm thinking about now, then if I did have to put in the other cat on the other side of the frame I still could. I'd probably have to lengthen the wires on the rear-most O2 sensor, but that wouldn't be a problem.

Anyone an emission expert on here???