Make a full exhaust for 420a Turbo

david-b · 08-03-2009, 11:04 PM

When I first started modding my 420a ESi, I thought a 2.5" exhaust was going to be enough. After I turboed, I decided I wanted to get the best flow as possible from the exhaust. Plus after 3 or 4 years of salty Chicago roads, the exhaust was starting to fall apart.

When I went turbo I made a custom turbo->DP sectional. I connected it up with the existing flexpipe that came with the 4-1 header that I had purchased off ebay. The pipe ended up sitting too low and keep bottoming out and cracking the pipe.

Ideally if you're good with a welder, you can make all these pieces yourself. I'm not that great, but getting better each day. But I decided to buy everything and see how well it all fit up.

Parts List
-GST Downpipe 2.5"-3" (Size depends on what you're doing)
-GST 3' Cat-Back (4.5" tip)
-Turbo->Downpipe. I used 2.5" piping
-Turbo flange, O2 bung(s)
-2.5" 2-bolt flanges

I first took out the old exhaust

Here you can see where I kept bouncing it off the ground.

Next I took out the new one and made sure everything was good. Compare the axle back/muffler on the 2.5" to the 3"

I then installed the cat-back first. The axle back section is the hardest to get up in there. The flange is a little too big, but with some proper tapping and jamming, she slides right in

Now my turbo->downpip section was already made earlier, so I kept that as-is and was just going to bolt it up to the flex section. If you're making one from scratch, make sure the O2 sensor(s) are within 16" from the turbo

The GST downpipe/flexpipe is reverse. The 4g63 motor sits opposite the 420a, so the cross member is on the opposite side. So the pipe will not bolt right up. What I decided to do was to flip the pipe over, and then cut off and re-weld the 90* curve going up to the turbo.

Picture shows the DP flipped over to fit around the cross member. I then cut the curved part (currently facing down)

I then welded on a new flange on the downpipe. This is my buddy Kevin welding, and he'll never weld again. Just a note, make sure you tack-weld everything first and make sure it all fits properly before making the final welds. Can't stress that enough. Thus why he's not welding anymore.

After bolting the downpipe up, this is what I was left with.

A nice 3 3/4" gap between my current downpipe and the GST downpipe. I took a 180* 2.5" pipe that I had laying around and cut and welded 2 new flanges on it and ended up fitting perfectly. I don't have pics of that fully completed yet.

And that's about it. Final result looks like this out the back

Will also get a better pic of the rear of the car later. But you get the point. The 3" is actually quieter than the 2.5" I had on prior. Amazingly low rumble at idle and cruise. At WOT the thing is a beast.

steviek · 08-04-2009, 09:05 AM

well done I want to see the pic where the DP meets the MP.

SilvrEclipse · 08-04-2009, 11:34 AM

Looks nice Dave. Did you notice any difference in power after the install?

david-b · 08-04-2009, 11:49 AM

Quote:

Originally Posted by SilvrEclipse

Looks nice Dave. Did you notice any difference in power after the install?

Yes I did. The car is much smoother when accelerating and idle is a little better. I had a cat before as seen in the pic and don't have one anymore. I'm guessing most of that has to do with the cat. But "the beast needed to breath better" as Brian put it.

I have a lot more low-end torque I've notice. Was at WOT, redlining the other day and the thing just keeps pulling great. Very happy with it. My buddy who was losing when I we were on a closed course said I left a nice trail of black exhaust smoke behind the car. Beat his IS300 by over 2 car lengths, after starting off behind him.

Blackcrow64 · 08-04-2009, 03:55 PM

Quote:

Originally Posted by david-b

But "the beast needed to breath better" as Brian put it.

Yes... Yes I did. lol

Quote:

Originally Posted by david-b

My buddy who was losing when I we were on a closed course said I left a nice trail of black exhaust smoke behind the car.

lawl...

Tune it biatch.

david-b · 08-04-2009, 04:01 PM

Once I finish MS then we'll be good to tune. Should get a little more done tonight I'm hoping.

boostjunkie333 · 08-05-2009, 09:38 PM

damn, looking at those pictures, thats a really good job...

wish i had my own shop and welder, ect., im a student so i dont have my own house yet(or garage), i rent

lol

david-b · 08-06-2009, 08:43 AM

Quote:

Originally Posted by boostjunkie333

damn, looking at those pictures, thats a really good job...

wish i had my own shop and welder, ect., im a student so i dont have my own house yet(or garage), i rent

lol

Thanks. I haven't been able to get more pics to show the final result yet. But I'll be under the car tonight so I should then.

I rent too. Nothing wrong with that. No garage, just the little space where the car is parked. It does the job, but if I had a garage the car would be done. I'd be out there at like 3am working on shit.

SilvrEclipse · 08-07-2009, 06:21 AM

Dave when you start messin with MS let me know. I have made some changed to my accel map and a few other things you will probably need to change. Helps the car run smoother when shifting.

boostjunkie333 · 08-09-2009, 11:23 AM

Quote:

Originally Posted by david-b

Thanks. I haven't been able to get more pics to show the final result yet. But I'll be under the car tonight so I should then.

I rent too. Nothing wrong with that. No garage, just the little space where the car is parked. It does the job, but if I had a garage the car would be done. I'd be out there at like 3am working on shit.

lol, same here, i feel like a mad scientist with no laboratory

but yeah, id def like to see the work after your done with it

david-b · 08-09-2009, 05:42 PM

Here is the little curved section I was talking about. Ignore the crappy welds on the turbo piece. My welding has gotten a lot better since then and it kept leaking from hitting it off the ground with the old flexpipe.

I have to loosen everything up one of the days because I tightened it all up before everything was in place. So the cat back actually angles down a little coming to the flex pipe. Not anything bad, but the slight off-ness of it is causing a rattle somewhere, probably coming from the axle back piece.

And here's what it looks like out the back. Is slightly angled which makes it look very aggressive. Excuse the dirty... been raining alot and now hot as hell outside.

And here's a video of it at idle. Will get one eventually on the road.

Also just wanted to show how my welding have progressed. Below is a flange for the curved sectional. The bottom part of it was done oneday. After I did some reading, some more fooling around and some changing of settings, I did the top part. Night and day. All my welds since then have looked like the top part, which is what it should be. Not bad for a $250 Home Depot gas-less welder. I didn't even know I could get results like this from this thing.

SilvrEclipse · 08-09-2009, 06:19 PM

Looks awesome Dave. Those welds look pretty good to

boostjunkie333 · 08-09-2009, 06:52 PM

the angled muffler looks pretty fricken sweet

question...been meaning to ask...when you say welder...do mean the electric stick welder that you can buy like anywhere...

i need one, was wondering what you used, bc thats a pretty clean job you did there...and if you can do that with a regular portable welder, then i might just invest in one myself...

david-b · 08-09-2009, 07:07 PM

That's it. It really does take a while before you start getting good welds. Took me a long time. But it's fun (at least to me).

david-b · 08-09-2009, 07:09 PM

I do recommend if you do get one, gets lots of extra weld and a helmet. It comes with that little shield shown, but two hands are better than one (that's what he said)

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