There are no decent 8v exhaust threads. just 300 poor ones. So hopefully this is it. We want proper info and useful pics. exhaust system diameters/system weights etc. The thread can be thinned down/ modified at a later date as we collect info. The end result possible being the creation of 'ultimate' 8v gti exhaust. dependant on budget/performance & rolling road testing. OBSERVATIONS The O.E.M 8v System appears to be 50mm OD QUESTIONS Is there anyone who can measure OD/ID of stainless 4 branch Manifold, the pipes off head and the outlet. Is there anyone who knows of larger than 2" system for the 8v? (possibly Jetex)and where is the step up adaptor/ gains here? PICS Standard 8v Exhaust System (manifold not shown) Downpipe, front silencer, Middle box and backbox. O.E.M Downpipe vs. Magnex Downpipe Magnex downpipe O.D outlet 50.8mm I.D 46.8mm O.e.m Downpipe has indentation in one of the secondaries to get around the Steering rack? upsetting flow possibly. Common Stainless Steel 4-2-1 'Manifold' NEED TO POST NEW PIC SO YOU CAN SEE ITS 4-2-1 NOT 4-1 With Mk3 style? sprung joint Replaces O.E.M Manifold and Downpipe Not so common 4-1 stainless steel manifold Possibly TST/Milltek MK3 Style Flange The plate at the top of the pic below needs to be welded to the original pipework on the car if you have a mk2 golf which doesnt use this joint as standard. Then the bolts come from the manifold to the flange and are used to give the correct tension on the joint. there is a small half doughnut made of carbon? type material, seated on the lip of the flage and seals in the flared manifold end. If you've bought a manifold and dont have the top plate and half doughnut sealign ring, I think? you can just buy a mk3 golf de- cat pipe, and cut and/or adapt to fit. Simples.
I'm sure it is the same bore all the way to the rear silencer. With regard to the change in bore size with an aftermarket system, I have a pipe that is standard size bore to the first resonator, after here it goes to 16v size, 2.25" I think and stays the same to the rear box. It's a Milltek btw, probably no longer available now.
The Magnex downpipes in your pic are bad for cracking as they have a pretty thin wall thickness and do not have the flexi joint like the OEM type. They have a sprung compensator joint where they mate to a Magnex system, but this does not really seem to help much. I have 3 or 4 broken ones here that are cracked just below the 6 bolt mounting flange.
I used standard 8v downpipe as per the picture in post 1, matched to a standard 8v Gti exhaust system. This along with a standard 16v manifold was good to take an ABF engine up to 162 bhp I am not saying that the aftermarket parts aren't of any benefit, just that the standard parts are capable of decent outputs. Add pipework lengths to this study as it's the combination of diameter and length that tunes the system to work better at x rpms ( a tape measure down each section of the manifold / downpipe will be sufficient)
Ben S - if you can match a 8v downpipe to 16v manifold?! why cant you attach a 16v downpipe to an 8v manifold? and the whole 16v system being 2.25" not 2". surely they dont mate up. or is ABF manifold flange same as 8v gti mk2? Danster- very interesting they fail. Ive got one going back on. I've got in production a 2" stainless straight through pipe. 1 piece from Magnex downpipe to the backbox. With a braided flexi not sprung mk3 style. Will post some pics at the weekend. Do you think there is the market out there for in a 1 piece item that mates from standard manifold to backbox? It would need to be shorter than the one im working on as standard downpipe is longer. Can be built mild or stainless and with/without flexi (-20). Not got much time to add some of the info Ive gathered to this thread but might get a chance at the weekend.
The oem downpipes for the 8 and 16v differ in that the 16v type has a large resonator box halfway down the downpipes. Makes it a pig to fit and remove. The 16v one also has a slightly larger outlet where it mates to the exhaust system front section (tunnel section). The 8v one can easily be modified to create a larger diameter pipe at this point. The 6 bolt flanges are the same in size and position on both the oem 8 and 16v cast manifolds. Interestingly the XR2s that race in a one make series always chose to have a long secondary downpipe fitted as it was seen to give improved torque over the shorter type. The longer type being very similar to the Golf 8v downpipe in length, but the XR2 ones had larger diameter secondaries.
Good info danster. So an aftermarket 16v downpipe which should have no res. box? would fit the o.e.m 8v manifold and you could go 2.25" the whole way from there + any 16v backbox. Effectivly a 16v system on an 8v. I can seem to fit the damn exhaust im sure i measured 50mm magnex downpipe outlet but its 2", 50.8mm OD so new pipe wont slide over quite, even after some grinding. So got to go back to the machine shop to use the pipe expansion machine and make it 1mm wider! doh! This pipe will at least allow me to test numerous backboxes on the rolling road, before I cut the old pipe off I hadnt been able to remove the back box since I owned the car (5 years!) as the joint was rusted rather tight. Id like to test a completely standard system too, but dont own one so with keep an eye out.
It is a pain that there are so many variations in pipe diameter and wall thickness. This makes the OD and ID of the components critical to allow proper fitting. Yes the oem 16v downpipe with resonator will fit straight onto the cast 8v exhaust manifold. And like wise a oem 8v downpipe could be fitted to the cast 16v exhaust manifold. You could just increase the outlet size of the downpipe to mate to the system diameter, and add a lambda boss too which is useful for testing AFR. I have heard it said that a resonator should be fitted in the mid section around the gearstick area of an exhaust. It is to help calm and dissipate some of the high frequency pressure waves that can effect scavenging, or something along those lines.
My 8v came with a 2.25" Magnex 3 box exhaust mated to an 8v down pipe and i assume its a 16v system. It had a reducer fitted,here's the best pic i could find. You can see where the downpipe went INSIDE the reducer on the left,to compare it with,heres a pic of the same exhaust fitted to a 2.5" downpipe (neater reducer now mind lol)
Can anyone assist with my milltek manifold query pls? http://www.clubgti.com/forum/showthread.php?t=234299
Brilliant!!! (It's deffo Milltek manifold which TSR can still supply I believe). I'll go down the route of carefully cutting the flange off if I can't get a mk3 de-cat pipe. Will report back on final installation. EDIT! Mk3 De-cat pipes appear to have 3-bolt flange........
If you look at the flange on the stainless steel 4-2-1 maniofold in post 1, it also looks like a 3 bolt flange but you you just use the two horizontal bolts. Im sure these manifolds are designed to fit the O.E.M mk3 exhaust system therefore a mk3 de-cat should be right... is the milltek a custom flange and not mk3 that is the question. I doubt it. we need to see a pic of a mk3 8V GTI de-cat pipe if anye can find one...
I think my Milltek manifold "used" to have a resonator connected to it........ Here are pics of someone else's without the resonator and you'll see theirs has that flexible joint with no tube protruding from the downpipe exit.....
Found the Milltek part no's for 16v Version:- TSR/Milltek 4-1 Stainless Manifold - mk2 Golf 16v MSVW3003 - Manifold & Decoupler x1 258-895 - Shoulder Bolt x2 251-860 - Conical Spring x2 256-860 - Olive x1
Have a look on the BBT thread, they're producing the backbox in SS, to the design of the original. https://clubgti.com/forums/index.php?threads/231964 Not sure about the rest of the system. Longlife exhausts would be able to the whole lot I think. Will sound different t othe original though....
