# 8v exhaust manifold/downpipes - stock replacement options/upgrade questions



## GTi'd (Aug 28, 2003)

I've found a decent amount of information about about upgrading my stock 8v Jetta GL exhaust manifold/downpipe with one from a GTI or a Carat, etc. I seem to keep coming across vague info about MK3 manifolds/downpipes fitting up, and even some about how the MK4 2.0 fits the MK3 2.0 (so wouldn't it then fit an MK2 8v, if so are there clearance issues, etc, etc? Who knows?)
Basically I'm just looking for a list of what mates up to what or at least a better idea of a range of options. Which manifolds I can use, and which donwpipes match.
Which manifolds (other than the rest of thedual outlet MK2 8v manifolds) fit our engines?
Who has successfully done what?
MK3, MK4, anyone know the details?
It would be great to add info and a list into the FAQs.


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## GTi'd (Aug 28, 2003)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

So, just to start I know the dual outlet manifolds and downpipe from a GTi or a Jetta Carat are a decent upgrade for the GL (this info is in the FAQs). I'm 99% sure the manifolds mate up to the downpipes from a 16v exhaust as well, and obviously the rest of the 16v exhaust would fit (obviously a GLI exhaust wont directly fit a Golf, and likewise a GTI exhaust won't directly fit a Jetta)


_Modified by GTi'd at 9:55 AM 2-29-2008_


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## 8valvinsleeper (Jul 13, 2007)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

I think i can help. I currently have 1 of every type of manifold lol. I used a mk3 2.0 xflow manifold and downpipe on my mk2 counterflow and it worked perfectly fine but i had to make a test pipe with an 02 sensor bung welded into it. I will take pictures once a camera is more accessible. The original TOILET BOWL manifold that is a 4-1 is pretty terrible. After installing a camshaft, it actually hurt my powerband because i needed to advance it so far just to get any torque and i had absolutely now power after 4,000 rpm no matter what. Some people say that the dual outlet will flow just as well as a header and i havent seen any specific flow testing done but the parameters of a header are better because of how each cylinder has its own "downpipe" until the collector. People generally see a 5-8 hp increase on a completely stock motor when installing the dual outlet and this is more towards the top end. IF you have a pretty built up motor than it will be felt more noticeably. The 16v and 8v dual outlet manifolds will both bolt up to the dual downpipe so long as its not from one of the earlier smaller 6-bolt setups that use the smaller gasket that isnt "spider" shaped. I find it is easier just to rip off the cylinder head for this project because those exhaust manifold bolts are a PITA. I removed the cylinder head for a rebuild anyways and didnt even need to use a drop of PB blaster, i just put my 12mm socket on and cracked each one HARD for a good quick impulse of torque and each one came loose. Seeing as they are locking nuts on studs that have been in place for 16+ years, the stud will usually come out with the nut. With my camshaft on the motor before installing the dual outlet setup, i saw 95 whp on a 1.8 8v that had a cold air intake and cat-back with no cat. It had alot of other problems (bad 02 sensor, blown valve guides and stem seals, bad CTS and fouled sparkplugs) but still not bad for a toilet bowl manifold. Tomorrow, i am going to bolt the cylinder head on with everything attached out in the blizzard like a man. I hope to see close to 140whp in my current state of tune. (alot of cylinder head work, alot of bolt-ons, chip, test-pipe with wideband 02, raised compression to 11.0:1 and alot of intake mods). Its definitely worth it to swap over to the dual outlet manifold and downpipe because of the kick in powerband for as much as you will be tuning it. Ive seen 2.0 16v use the equivelant 16v manifold and the same downpipe and make 160 whp so i am convinced that the dual manifold and downpipe can handle anything you throw at your 8v. I picked up my full setup for $50 with new studs for the head-manifold and manifold-downpipe, it was all sandblasted and the manifold was ceramic coated, it came with a brand new flange on the downpipe. The only thing i did today was take a piece of 2.25" exhaust piping from a saab intermediate pipe, cut off the flex tubing, beadblast it all, weld on a larger 3-bolt flange (70mm bolt separation) 1" from the flared end of the 2.25" pipe. Cut a hole in the middle of the pipe, welded in a 02 sensor bung, sandblasted it and ceramic coated it. Everything cost me $50 because i got alot of hardware for free and the test pipe was made from junk exhaust pieces in a metal pile. The 4-1 toilet bowl manifold has the 02 sensor right on the back but the dual outlet is meant to have the 02 sensor on the catalytic converter so you'll wanna lengthen the 02 sensor wires. I also wrapped them in aluminum heat resistant tubing. I reccomend using copper locknuts on any studs you use and put high heat copper anti-seize onto the studs themselves so that they release easier with the locknuts when (if) you plan to rip it all apart again sometime.


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## GTi'd (Aug 28, 2003)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (8valvinsleeper)*

Nice, so, to summarize, the x-flow manifold and downpipe will fit the counter flow head, but an 02 sensor bung needs to be added in somewhere.
Do you know the cut off (year-wise) for the "earlier smaller six bolt set-ups that use the samller gasket..." for the dual down pipe.


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## GTi'd (Aug 28, 2003)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

anyone else?


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## 8valvinsleeper (Jul 13, 2007)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

i dont know the cutoff for them, you will notice that the gasket will be rectangular shaped and the 2 exhaust holes will be closer together and smaller. I dont want to spit out any information if im not 100% positive but i think the smaller manifold-downpipe flange was just used on mk1s. The mk3 xflow manifold and downpipe fits the mk2 counterflow setups regardless of what anyone is going to tell you. Some people will say "oh the cylinder head is slightly taller so the downpipe is longer". It still fits. I can see why they would say this. If you look at the cross-section of the xflow head, the exhaust ports are higher up and exit the chamber at an easier angle. Regardless, it still fits and doesnt sag. the fact that it has a flexpipe on it anyways allows you to raise the height of the downpipe-intermediate flange by just pulling the downpipe back slightly when assembling it. the exhaust test tube from the xflow is at a wierd angle because it doenst have clearance issues with the intake manifold, i just bent mine back around the intake manifold to make it fit. It sounds a little deeper and throatier with the dual setup on it and it revs alot quicker.


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## GTi'd (Aug 28, 2003)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

nice. Anyone else?


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## kirochan (Jan 2, 2008)

I just installed a dual downpipe and manifold off a MK3 on my MK2. I have a 91 jetta gl 1.8 8v RV, and everything fitted up fine from the head all the way down till the cat. The flange for the dp is bigger that the flange on the cat. I bought a cat from autotech which will be here friday hopefully. But yes, a MK3 has no problem. It is just a pain in the a$$ to get one of the manifold nuts on with the head still on the car.
oh yeah, the setup is not longer at all, if anything about a 1/2 inch different.


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## GTi'd (Aug 28, 2003)

*Re: (kirochan)*


_Quote, originally posted by *kirochan* »_I just installed a dual downpipe and manifold off a MK3 on my MK2. I have a 91 jetta gl 1.8 8v RV, and everything fitted up fine from the head all the way down till the cat. The flange for the dp is bigger that the flange on the cat. I bought a cat from autotech which will be here friday hopefully. But yes, a MK3 has no problem. It is just a pain in the a$$ to get one of the manifold nuts on with the head still on the car.
oh yeah, the setup is not longer at all, if anything about a 1/2 inch different.

how did you handle the O2 sensor?


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## kirochan (Jan 2, 2008)

I bought the cheap bosch one from german auto parts that had no connector to it and spliced the wires together with 3 "extension" wires using but connectorts and alot of electric tape. I did use solder at first but I fotgot I still suck at that. It is long enough to fit in the plug at the bottom of the DP and connect to the engine harness.


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## GTi'd (Aug 28, 2003)

*Re: (kirochan)*

So the O2 sensor bung is there, just further down? I thought it needed to be added in. Or was it on the cat that you bought?


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## kirochan (Jan 2, 2008)

the thread hole for the O2 is at the bottom of the dp where it connects to the cat. The cat also has a thread hole for an O2 but I have a plug that I bought of german auto parts for it. You could just use a bolt though.


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## kirochan (Jan 2, 2008)

allright, I will update my Dual manifold and DP story. I cat the cat today from autotech but the inlet was a 60mm and the dp is 55mm. I luckily ordered two different size exhaust doughnuts. The smaller one fitted on the dp but was way to small for the cat. The larger one fitted on the cat but was too big for the dp.
I just took a grinding stone and grinded away on the dp until I could get the larger doughnut to fit. The other end of the cat did not fit inside the 2.25 TT cat back so I had to use a tailpipe expander and play around with it until I could get the cat to slide inside the TT cat back. The cat was a 50mm outlet, I think if I got a 55mm outlet it would have fitted over the TT cat back.
If you are wondering why I just didnt return the cat on try something different,,,it is because i didnt feel like waiting anymore. Besides it is a 3speed not manual.....


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## GTi'd (Aug 28, 2003)

*Re: (kirochan)*

nice, anyone know about the rumor that the MK4s fit up to the MK3s and MK2s?


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## 8valvinsleeper (Jul 13, 2007)

*Re: (GTi'd)*

Yeah my setup was pretty easy to fabricate up. the downpipe didnt have any 02 bung or threaded hole in it so i just made that testpipe and its great. I havent been driving the car though because my timing is way out of whack. First, the ignition timing was screwed up so i fixed that but it felt like the powerband was way too messed up. If youre using the dual downpipe, i learn that it balances the powerband out alot more as a whole and advancing the cam timing for more low end torque isnt really necessary. Advancing my 270 cam actually hurt performance more than it helped. Its all about your individual setup though. The easiest way to make a testpipe i find is just to take a SAAB flexpipe piece that has the flared/bulb ends and cut out the flexpipe and just weld a 60 mm flange to the peak of the bulbing. The 60mm flange has the normal 70mm distance between bolts. It was the only thing i had and it worked out great. I'll try to post pics if i get time.


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## GTi'd (Aug 28, 2003)

*Re: 8v exhaust manifold/downpipes - stock replacement options/upgrade questions (GTi'd)*

What about MK4 2.0 exhaust manifolds? Anyone have any knowledge to share. I've heard they fit the MK3s (2.0), and thus the will fit the MK2s (1.8).
Anyone know for sure?


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## Joe Poodle Esq. (Aug 20, 2007)

bump for interest


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## SilverMkII (Feb 9, 2003)

*Re: (Joe Poodle, Esq.)*

I have also heard that the MK3 & MK4 manifolds can be used on the MK1 as well. I would like to see this done since the MK4 is tubular & flows quite well.


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## [pl] (Sep 13, 2003)

http://forums.vwvortex.com/zerothread?id=3781931
http://www.facebook.com/album....20872
here is what it looks like when u use the mk3 non-cast iron type (needs trimming), the cast mk3 manifold fits like a glove. i got both sitting on my table.
The O2 sensor bung sometimes is on the DP and sometimes not, the DP i have does not have bung. I need to add it, and require longer O2 sensor wire.



_Modified by [pl] at 7:38 AM 4-14-2008_


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