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Thread: Mk2 gti exhaust advice

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    Default Mk2 gti exhaust advice

    My 8v is quite "drone-y" at motorway speeds, even though the system looks OK and has no leaks. And it's a stock, albeit non oem system.
    Now shortly the car is getting a TSR 2.0 8v going in, with a tubular system, so I'll have to do some exhaust work anyway.
    Firstly, at what stage does a Digifant exhaust system start holding the car back, and secondly, is the drone most likely to be from the mid section or back box? It's in it on acceleration and deceleration, it eases on light throttle input.
    IRISH Dubber... Mk6 Golf "GT" 2.0 Tdi 3dr
    Mk2 GTI 8v, 3 Dr, Tornado Red
    Mk1 2008cc 16v short lamp , small bumper , under reconstruction
    E39 M5

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    Drone = lack of a suitable duel camber back box and a mid section that is too small.

    You need between 2.25 to 2.5 in dia exhaust to aid exhaust scavenging at higher rpm and say after 150bhp+

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    You can draw you own conclusions from this. I've had two Magnex DTM back boxes due to the first one cracking after a year or so and they both behaved the same with the rest of the system unchanged (Ernst stock). Over the course of six months or so on each new box the drone went from nothing to bellowing at iirc 4500ish upwards in top gear. Presumably in tandem with build up in the silencer material. They also have a terrible internal flow which I'm sure compounds the problem. I think Jason cut a customers Magnex back box open. There used to be a picture of it on here. A 'Y' shaped perforation is all I can remember of it.
    1989 5dr MK II 8v Helios Blue Bodyguards® 4 Nitrile Edition. 21 years of ownage.

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    Interesting. I like the sleeper, subtle nature of a stock exhaust. I suppose I could look for a stock 16v system?
    Even at my wildest dreams, I can't see it breaking 150, even with SEM and a MAF delete. Stock 2.0 bottom end, aside from a slight compression hike.

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    The end of the exhaust is the only bit that most people see so that's the bit you need to make look stock.
    1978 MK1 GL, yellow 2 door, 2.0 16v, twin Delortos. I'll get it back on the road one day.
    1991 MK2 GTI, white 4 door, 2.0 8v. Was my daily driver, over 1000 ks every week. RIP. Replaced by a red MK2 GTI auto. OK it's slow (and red) but at least it's a MK2 + another red 4 door for spares.
    1998 Seat Cupra 2.0 16v, parts car for the MK1.

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    Tbh it's the subtle sound is just as important. I daily this so a loud system isn't ideal.

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    A standard 16v system would be suitable for flow.

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    Thanks Toyotec

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    As per Eddie I'd use a 16v system or an aftermarket 2.5". The stock system is a little small for a breathed on engine, but will work.

    My experience with my 2.0ltr 8v road rally car was this.

    It came with a TSR head big valve head and cam (203 clubsport circa 285 degree hydro), 4/1 mani, home made exhaust (loud) and re mapped fuel chip in the ECU! Otherwise std 2.0 ltr 2E block with a 1.8ltr head, Std air box etc.

    Nothing wrong with the engine, and it felt ok on the road, ran it in a few hillclimbs and sprints and whilst we won a few we were getting killed on the straights.

    Took it to my normal rolling road and it made 115bhp at the crank, about stock! (The Tatty Golf 8v makes 224bhp on the same rolling road!). Took it away, did another event then fitted an adjustable vernier cam pulley. Took it back to the rolling road to have a play and it promptly ran a big end shell!

    Anyway, getting to the point, I took it away and rebuilt the same engine, taking time to deck the block and pistons - getting the squish and compression right, new shells, proper ARP bolts etc, windage tray, baffled sump, matched all the ports, exhaust/inlet manifold etc., got the fuel chip changed, mapped the ECU, fitted an 8v 2" magnex 3 box system (more on that in a minute) and new seals, gaskets etc. etc.

    Basically it was exactly the same engine with the same pistons, rings, head, cam etc. just put together properly and set up.

    Now it made 150bhp at the crank and was on the pace. Won its class for a couple of years - very strong engine.

    That was on a std throttle body, digi injection , 2" Magnex with three boxes, std air box and even std air filter! Was the quietest car in the class by far, about 78dB as I recall. Problem was no one ever took pics of it as it was so quite it didn't sound fast, everyone was always surprised when they were going on about this and that escort in the class, then you told them we actually won the class they didn't believe you Lol, proper sleeper.

    Few mods were to modify the airbox, cut out all the rubbish out and put a cold air feed to it. Also the rear Magnex twin pipe box didn't look too clever in side, so I cut it off and fitted a 2" Formula Renault box I had laying about. The Digi ECU need the chip mapped, but that is just the fuel, with that done and nothing done to the ignition map or rev limit it was flat, sent the ECU away and had a map put on it from a similar spec race spec golf. Livened it up no end. This was before its last dyno run.

    I never played with cam timings and think there was probably another 5>8 bhp in it with a few hrs fiddling.

    So basically std throttle body is fine, Digi is fine, 2" exhaust will work, even with too many silencers (although I would have fitted a bigger dia if I could have found one cheap at the time) and take time in setting it all up.

    Hopefully that is of help....I'm off out to the workshop now.....to weld a morris minor split screen convertible....don't ask - its not mine!!

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    Thanks TonyB, really appreciate that.

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    Quote Originally Posted by TonyB View Post

    Hopefully that is of help....I'm off out to the workshop now.....to weld a morris minor split screen convertible....don't ask - its not mine!!
    Guessing you won’t be back on for a while then?

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    Quote Originally Posted by notenoughtime View Post
    Guessing you won’t be back on for a while then?
    Haha, its not actually that bad, a few new floor panels each side plus the outer panels, and localised repair around the rear quarters and front jacking points. Its fully stripped, braced and on a stand so quite nice work.

    What popped in to my mind after I wrote the post was that I forgot to mention one big issue I had, and that was with the exhaust manifold. Many I see have issues where the port dimensions are bigger than the header flange holes. On this particular manifold, which was a stainless steel TSR copy, the holes was about 75% the size of the exhaust port!! A massive restriction, could well have be 50% of the power gain, if not more.

    Another issue is exhaust gaskets, they can be fitted the wrong way round, again restricting the exhaust port, seen this done. Also there are different sizes, they can be smaller than the port. When you try them, no point centring them on the port, let them drop on the studs (as that is what they will do when you fit them), and check they are clear all round then, and at the extreme left and right. You can machine the centre wrap around metal flange right out, they still work fine, even use a bit of high temp silicon.

    Also have a look where the 4 downpipes meet in the collector, this can be dodgy, I've cut them open in the past and modified them, although the one above was fine, just the header was a disaster!!

    Just thought I would mention that whilst I was in here. Don't get much time these days, and with Photo bucket having messed all the forums up its a bit demoralising.

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    From what I remember, G60 gasketsare bigger in the ports and help.

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    This concern here as I read it, is a suitable system that does not resonate excessively at cruise and at the same time does not create back pressure to hold the engine back.

    Many aftermarket systems can fall foul of this concern and most customers are not picky enough to observe, mainly because of what their cars are used for.

    You can have an exhaust system that is 78 dB at 3/4 throttle and bursting your ears at 70mph, due to the design of the boxes.
    I have been there as I run my fairly modified sleeper as a daily, accumulating 1000s of miles in it. It is not nice when you cannot have a conversation with the children in the back as you cruise to drop them to school having to shout back and forth, due to either drone at 3000-3500rpm or a nasty boom on lift off when you are on fuel cut!

    I spent a lot of time developing a suitable exhaust system at my local guys, Style Dynamics to dial out this phenomenon on two of my cars and it is that experience I can share.
    This has caused that business to change the way they sell exhaust systems for G60 and G40 vehicles.

    JENVEE is more powerful that many modified 16v cars on the road and certainly most 8v engines capable of road usage. So power in reserve can be ruled out.

    Drone is cancelled via the intermediate box, which is from a 320d and a specially ordered duel camber back box that exits as stock looking slanted tail pipes to add to that "sleeper" look.
    I would still debate my idle is still heavy enough to let my son's school know that JENVEE is out in the car park!! . This was less pronouned with the Jetex back box it was previously fitted with, which is also a very large duel camber system.
    This still needs to be worked on.

    Less important but to correlate to my point on static testing at the track, I am @ 82-84 dB at 4500 - 5000 rpm. So quiet-ish for that sort of measurement standard but still noisy in the school car park.

    Hope this helps clear up what is required.

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