Question as per title really, Will a 4 Branch designed for a Mk3 8v Gti fit A Mk2 8v gti? I've seen a nice 4-2-1 for an AGG engine that I'd like to try on my Mk2. Any advice appreciated
The AGG block is 16mm taller, so this will reflect sitting lower / ground clearance when bolted to a PB.
Ok, as we're on quick fire here. 1.8 8v PB with Piper 285 cam in Std, blueprinted head (not allowed headwork) 4 into 1 or 4-2-1 Manifold ???
Have you got a pic of the 4-2-1 manifold? There are some odd designs of these out there with questionable primary and secondary dimensions. The mk2 Digifant oem cast manifold and long secondary downpipe are pretty good as is. The option to run the shorter mk3 oem secondary downpipe is there too.
I'm currently running an optimised (internally sandblasted) standard PB cast manifold with a BTB custom downpipe into a single box 2.25" mandrel bent custom exhaust. The champioship may be allowing us to run a 4 branch in the 8v class next season so I'm exploring options. Here's the 4-2-1 ebay special: http://www.ebay.co.uk/itm/GOLF-MK3-GTI-8V-STAINLESS-STEEL-EXHAUST-RACE-MANIFOLD-/350477836270?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item519a1b5fee What do you think?
Primaries a bit on the short side? Can't really tell how well it's made from a picture... you really need to have a look inside - especially where it mates to the head ports, and offer it up to a head.
Hmm...... I am no scientist, but to me that is an unusual design with the secondaries being so short compared to the primaries. If you look at most conventional 4-2-1 designs, the secondaries are usually longer than the primaries. If you have access to rolling road then it could be a useful test to compare designs. Then off load whichever one is no use. Personally I would be looking to use longer secondaries as this is known to help torque characteristics. Drunkenalan is using a similar type of exhaust manifold to the ebay one you linked to.
Will that one clear the bulkhead on your tall block Alan? You lads need to buy both types of these cheap manifolds fit them to your cars and find out if they make any odds. Mike_H has a good strong engine and uses a Supersprint 4-2-1 system iirc (my old one?) that has around 12" primaries, and secondaries of around 24". This pretty much mimics the oem type but with better merging of pipes. His is a mk1 platform being a rocco, but I still reckon the OEM stuff is easily good enough for mildly tuned engines. Toyotec and BenS amongst others have pretty much proved this with what the ABFs can put out through the std parts on the various tests. EDIT: Chris, there is the option of long or short secondaries now with the long Mk2 late K Jet & Digifant, or short Mk3 style downpipes too.
Are you suggesting stay as is, just port the manifold? Look at bigger powered 8v s, what about a TSR I have heard good things from Jason
Indeed I do have the Danster's old supersprint manifold. However, for racing, and with a lumpy cam, is a 4:1 (longer primaries) design not more suitable? I was wondering if that still held when the head isn't ported, and whether it'll have the rev range to make full use of a 4:1 / long primary style. Should never be below 4000 rpm in a race, I'd have thought.
I think the two engines of Bomber and Alan are substantially far enough apart in terms of capacity and spec to have differing requirements. Add the fact one is a road car and one is a race car. I can't see Bombers engine making more than your one Mike. But Alan's is a different story and should potentially produce more once things are sorted with it. My thoughts are that when running longer duration cams (not race) that the exhaust pulses should be kept isolated from one another as much as possible. The short primary 4-1 and that odd 4-2-1 with short secondaries in the links above seem at odds with the OEM systems, which work ok and are proved not to be to restrictive on reasonable spec engines. Full race stuff is a different can of worms I would have thought.
So the TSR / Milltek 4:1 design would go further towards achieving that than a 4:2:1 I'm not suggesting that a GTI series spec 1.8 8v will make more power than mine, but it might benefit from being tuned more towards the top end than for low down grunt, in race usage. I'd have to say, coming back to the original question, that I'd be looking for a good 2nd hand 'known' brand, rather than an ebay cheapo special.
I have the Miltek 4-branch and although I would never say I'm technical the result all round is perfect. The difference between my PB's is massive. The car will rev freely and doesn't run out of grunt it just keeps on going right up to the limit. I wouldn't go for an el-cheapo as you can get Milteks for around the 100 mark 2nd-hand. The last one I bought recently cost me 80 with all the flexi joints/rose gasket and adapter. Some people say they have had problems with cracking manifolds during race use but it you use the sprung bolt flange with olive gasket this won't happen. They need a bit of flex, mines been fine (fitted for 4 years) without any issues mated to a jetex with the proper sprung flange. and I have worn engine mounts!
Hi Guys, thanks for getting involved, this is exactly the kind of discussion I wanted Alan, I was lookin at one of those but dont like the look of the collector & the output diameter is smaller than my system so I'd have to cut it back & weld a flange to it. The other option would be to cut all 4 primaries & turn it in to a long primaried 4-2-1 using my current large bore down pipe as the secondaries. I think, realistically though I'll probably end up admitting I don't know enough about the science behind exhaust design & buy an expensive but properly developed race manifold from Retro Gti!!
