Replacing the exhaust....

takza · Post by **takza** » Mon Apr 05, 2004 4:18 am

Well it's that time. Been patching on it, but looks like I'll have to find the parts and replace the whole system from the manifold back.

My converter looks to be 20 years old...with the heat shields falling off. Downpipe has a leak (temp fix) where it is mounted after the manifold. Now have another leak at a mounting point further back.

Plan on just buying the downpipe and a generic converter with associated gaskets, using stainless sleeve type exhaust clamps....and then going with 2" ID (?) stainless flexpipe into my current glasspack at the rear.

Looks like Advance AP has the best prices...maybe.

Hope I don't have to mess with the O2 sensor.

Has anyone done this job?

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In the process of finding and ordering parts...added comments:

* downpipe to manifold gasket @ $2. AdvanceAP

* downpipe with 1 3/8" ID (old is same ID)...Walker @ $32. AdvanceAP...a lot of restriction with this pipe..the old one is the same. This is a doublewalled pipe.

* generic converter @ $43...11" long with 2" ID pipes in/out. AdvanceAP...should be a freeflow converter...has a heatshield only on one side...I'll try to modify & weld old one from current converter onto this one...if you drive in grass, it's very important to have a good heatshield.

* 10' 2" ID SS flexpipe @ $43. JCWhitney

* several 2 1/8" exhaust pipe clamps. buy locally...will use regular steel rather than ss steel...pipes are cracking... current clamps OK

* extra hangers. buy locally

* use current non-louvered glasspack muffler...they last a long time

Overall cost around $140...everything from header to ss flexpipe will be welded?...clamps from there on back

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When looking at the old commercially intalled exhaust...I see problems:

* not enough hangers installed (for a solid pipe) resulting in the pipes cracking.

* pipe has cracked in 2 places at mounting points due to the load not being spread enough...or from welding stresses. 1 crack at back of converter due to lack of support.

* clamp in center was not installed for best ground clearance.

My improvements:

* Add as many supports as needed.

* Possible flex joint in front of converter.

* Use the SS flexpipe to reduce damage offroad.

* Make sure clamps are installed for best ground clearance.

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"60HP (at the crank) per square inch of (cross-sectional) flow area.

This 60HP/in^2 is to get you in the general vicinity. It also is based on the inside diameter of the tubing not the OD."

So looks like the Toyota people knew what they were doing by using a 1 3/8" ID downpipe. My system basically has the narrowest areas of 1 7/8" ID in and out of the converter and at the muffler...the rest is 2" ID flexpipe.

1 5/8" ID / 1 3/4" OD all the way back thru a non-louvered glasspack is the best size?

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Got the exhaust installed. No major problems...just a good bit of work.

Made a heatshield for the generic converter (was inadequate as sold) out of light gauge steel and had it wire welded onto the converter. Also had the converter welded to the downpipe.

Made sure all clamps were put on for max ground clearance.

Only potential problem is the nearness of the exhaust to the gask tank where it is approaching the muffler....there is a need to have a serious bend in the exhaust pipe at this point to clear things...probably OK.

The old converter was not plugged at all...not so sure if it actually worked or not.

Complete exhaust with glasspack could be done for $150-160.

icE · Post by **icE** » Mon Apr 05, 2004 12:24 pm

Nope, but i oughta check my exhaust manifold. Probably deteriorated by now!

GTSSportCoupe · Post by **GTSSportCoupe** » Mon Apr 05, 2004 1:16 pm

takza:

That sounds like the perfect plan to me. The 2" diameter should give you some better upper end power, while not sacrificing much of your low end torque. Should be nice. I can't wait to upgrade my exhaust. I think I'll wait to see if I put a different engine in first though.

3A-C Power · Post by **3A-C Power** » Mon Apr 05, 2004 6:53 pm

I wouldn't use flexpipe, it's way too expensive. Exhaust clamps tend to not work very well and leak. I'd really suggest using a brazing torch with MPS gas (hotter than propane) and bronze brazing rods. It's only $20-$30 and works on stainless, sort of a poor man's welder. Then you can get exhaust pipe bends and straight sections and put your own exhaust together.

takza · Post by **takza** » Tue Apr 06, 2004 7:38 am

The advantage with the SS flexpipe is that it is lighter than regular pipe, has no restrictions after it's installed..and I haven't seen it start to deteriorate yet. Also, offroad, if it gets hit by something...it flexes insread of breaking.

Cost is not that bad if you price regular exhaust pipe that is already formed.

Also easy to install if done right. Has to be clamped down OVER solid pipe at each end using regular clamps...and clamped lightly where it is hung.

Is that MPS what they call MAP gas in the US? Can you use it with regular propane torch burners? Might try to braze in the hole I have.

I have a little 110V stick welder...I usually cuss more than I weld though. Hate to think about trying to weld exhaust pipe with it.

3A-C Power · Post by **3A-C Power** » Tue Apr 06, 2004 11:12 am

MAP gas is the same thing. You need a brazing torch because it gets enough fuel flow to braze. It depends how thick the material is but for exhaust pipe you probably need the brazing torch.