91.5 Downpipe - Stainless or Mild Steel??

[Hunter4x4]

Hey Gang -



Anyone know for sure if the downpipe from the turbo is stainless or normal 'mild' steel?



I have a 14cm turbo housing on deck which has an outlet neck about 1" longer than my stock 21cm. I want to cut the 1" out of the horizontal part of the downpipe to make room for the new turbo. If it's mild steel I can just but weld the pipe back together. I'm not sure it I can weld the stainless myself!!



Thanks!!



Mike

 

[bgilbert]

Have you tried just pushing the downpipe back and bolting everything up? I seen on a friends 93 where he got a 12cm in without cutting...

 

[Hunter4x4]

Thanks for the input but that won't work on my '91. 5. Pushing it back will jam the downpipe heatshield into the AC/Heater box and into the T-case down below - there's literaly no room (well, maybe a quarter inch LOL!) to move that pipe back.

 

[swankmetal]

it's just plain old mild steel. have fun with that 14! you're going to be amazed at how much better the truck drives.



dave

 

[BushWakr - RIP]

Hunter, I had the same basic setup as you and I loosened up all the exhaust clamps/mounts, and, with some C-Clamp style vise grips, a cheater bar, hammer etc I was able to move the system back enough to make a non-gated 14cm fit. Yes, the heat shield did touch the rubberized cowling but it did absolutely no damage to it at all.

If you must do some cutting then try the "moving back" process and then measure how much you need to cut. From there trim off the downpipe flange with about 1/2" of pipe stub remaining then shorten the last bit of straight piped section the amount you "measured".

If you do that, you'll likely be able to just jimmy back the exhaust system forward if you want to return to a short 16cm housing for example.



Also, if you really want to take some time and avoid the cutting welding and so forth then mark the area(s) were the downpipe will hit frame rails etc and use a ballpeen hammer to "create some tolerances" for your modifications.

I have done this myself on my 4" system and have had no problems with that type of "tuning".



pb...

 

[Hunter4x4]

PB - Thanks a ton!



On my way to church (really!) and saw your post - got a couple quick questions (breakfast can wait - we're talking diesels now!!)



How'd your truck run with the 14cm? (That's exactly what I have on the shelf waiting to install - 14cm non-wastegated) Did you originally use it with the 3" stock exhaust (which I still have)? How were your EGTs? Is your 4" from the turbo back or only from someplace further back?



Do you tow a load with it? (I do use my truck for towing - trailers up to #7,000 right now). If so, how were the EGTs?



I'm currently running a stock 3" exhaust with no muffler.



There's no better source of data than somone who has been there - Thanks in advance for your input!!



Mike

 

[Hunter4x4]

PS: FOrgot to mention, I DO plan on upgrading the exhaust after the turbo install to either a 3 1/2" or a 4". More on that later - gotta go!!!!

 

[cerberusiam]

Another option would be to cut the heat shield off and wrap the down pipe with some header wrap. Even with the heat shield and enough EGT's it will eventually burna hole in the insulation on the firewall. The gen 2's had a bit of a problem with fires under the hood from the same thing so the insulation will light off. The header wrap should help improve the the exhaust flow also.



My . 02. Have a happy Easter.

 

[CDegner]

How'd your truck run with the 14cm? (That's exactly what I have on the shelf waiting to install - 14cm non-wastegated) Did you originally use it with the 3" stock exhaust (which I still have)? How were your EGTs? Is your 4" from the turbo back or only from someplace further back?



Do you tow a load with it? (I do use my truck for towing - trailers up to #7,000 right now). If so, how were the EGTs?



I'm currently running a stock 3" exhaust with no muffler.

I'm running the non-wastegated 14 and I really like it compared to my 16. I can hit 40psig boost but I do see higher EGT's (I have the fuel turned up just a bit). I can hit 1350 empty up a grade at full throttle. I had mine ported by HDM48 before the install. I also have a full 3 1/2" exhaust system. A full 4" system would probably help a little more. If I were going to be towing much weight, I would probably put my 16 back on, but that would just require some playing to determine.



Carl

 

[BushWakr - RIP]

Hunter,,,,,



When I ran the '14 it was very responsive... the housing coupled with some decent timing advance really made it "jumpy" when you'd get on it. .

I also found that there was actually some "haze reduction" even at idle...

I had generally less smoke right from the get go thru the throttle range... .

The 16cm still does very well but it is not as "clean" at the low/idle range RPM's.

Now as for EGT's... . well you can't have it all... . when I ran the non-gated 14 I had some serious EGT issues at the upper end... . heck, even with the 16cm I have EGT troubles and I do not tow or pack heavy loads.

You really should do some porting on the 14cm..... do some gasket matching on the housing inlet were it joins the exhaust manifold. Take your time and use care as the runner walls are not as thick as you might imagine. Use your thumb/index finger to "gauge" the wall thicknesses...

This will offer some modest help in allowing the gases to enter the housing as quickly as possible. It won't eliminate or provide huge relief to drive pressures but it will help a tad.

Keep in mind that with all you do in terms of porting and smoothing you'll definitely have to use the throttle with care to keep temps in line.

You CAN "tweak down" a tad and have less upper end issues though... the 14cm will help compensate a bit even when you have less fueling at the top end.





The exhaust sytem I had on the truck at the time I used the 14cm was utilizing the stock downpipe with heat shield. I was able to tweak it back enough (as I mentioned earlier) to connect the 14cm. It was a bit of fiddling and hanging your tongue just right but it was do-able with only minimal skin grafting and ice packs for the head lumps... ... (as an afterthought... . never sit right up straight while UNDER the truck... not good )



After you've done the exhaust re-connect, check the connection after a coulple days to see if you have any soot buildup or signs of exhaust leak at the V-Band connection. You may have to do some fiddling to make the connection tight.

In my case, I just loosened the V-Band clamp a tad and used a rubber mallet to help the connection "settle" together then re-tighten the clamp... took a few times but it finally sealed up.



Hope that helps bud... .



pb... .

 

[Hunter4x4]

PB, Carl -



Thanks guys!! I think I'll be getting to it this coming weekend - I'll post back and let you know how it goes!!!



Mike

 

[BushWakr - RIP]

Hunter, if you need help, my phone is always waiting to ring bud... ... . after all, that's how I got started to right. .



pb...



oh... 604-467-6525... . after 7:00 PM west coast if possible.

 

[Hunter4x4]

PB - Thanks!