GolfGTIforum.co.uk
Model specific boards => Golf mk3 => Topic started by: shepgti on 03 July 2009, 14:26
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right found this video http://www.youtube.com/watch?v=kAdOH-M8rDk and its got me thinking about twin carbs/bike carbs just for something differnt, not really found much info on doing this setup other than needing a manifold to fit the carbs and the fueling side of things(injectors?) what sort of prices are we talking for a carb setup? may have to ask some of the mk2 digi guys as mine is a digi too :undecided:
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could also be intresting to source a cross flow head to get forward facing carbs :undecided: http://forum.performancevwmag.com/viewtopic.php?t=43126&sid=4a14dfeb0f7733abae848f2a2b1e430a
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I was toying with this idea dude, but gave up because I need a reliable (winter carb freezing) and reasonably economic car.
If you are going to do it, then yes get a cross flow head. The gti 8v from the mk4 has one.
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Yamaha R1 seems to the most used set up, I would think the biggest issue would be passing the mot maybe.
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Yamaha R1 seems to the most used set up, I would think the biggest issue would be passing the mot maybe.
Forget carbs...
If you are going to go that way, go with bike ITBs and fit a cheap stand-alone ECU and map the lot up yourself.
Bike ITBs are not perfect for cars due to the way and amount the butterfly opens from idle...but they'll work.
At least if you go with bike ITBs you can get the damn thing to start when cold, run when hot, properly sort out the fuelling as well as ignition and still pass an MOT.
Carbs are just a hit and miss...they always were back in 19 oat-cake...they still are.
As for bike ITBs ideally you want some from a big capacity bike that makes around 200 BHP so you know the injectors flow enough...and get some with a single butterfly - the twin throttle types are a nightmare to map up - you really need to remove one set. It's a problem you can avoid by buying wisely...
Say a set of 46mm inlet taper ITBs, with single butterlies, TPS, FPR, fuel rail and injectors good for 200BHP...and spacing pretty close to a VW 4 pot...
(ZX12R will work... :wink:)
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Yamaha R1 seems to the most used set up, I would think the biggest issue would be passing the mot maybe.
Forget carbs...
If you are going to go that way, go with bike ITBs and fit a cheap stand-alone ECU and map the lot up yourself.
Bike ITBs are not perfect for cars due to the way and amount the butterfly opens from idle...but they'll work.
At least if you go with bike ITBs you can get the damn thing to start when cold, run when hot, properly sort out the fuelling as well as ignition and still pass an MOT.
Carbs are just a hit and miss...they always were back in 19 oat-cake...they still are.
As for bike ITBs ideally you want some from a big capacity bike that makes around 200 BHP so you know the injectors flow enough...and get some with a single butterfly - the twin throttle types are a nightmare to map up - you really need to remove one set. It's a problem you can avoid by buying wisely...
Say a set of 46mm inlet taper ITBs, with single butterlies, TPS, FPR, fuel rail and injectors good for 200BHP...and spacing pretty close to a VW 4 pot...
(ZX12R will work... :wink:)
Friend of my dad has got a 2008 gsxr1000 he has had some head work and a remap and the bike makes 201bhp at thw wheel. bloke who did the work did say that the engine is very good, but what I'm saying is new 1000cc bikes itb are good enough.
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Carbs are good in fact great on the right car! Can be better than injection if you go for 2 twin barrels!
But on an already injected engine you have the problem of the ECU.
You either have to ditch this completely and go for some kind of electronic dizzy set up with a TDC sensor or find an ECU that works with carbs.
Far better in my opinion to go for throttle bodies.
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Yumm.....16V on TBs......idea....
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there was a 16v with jenvey bodies on ebay. looked sexy as fook!
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Carbs are good in fact great on the right car! Can be better than injection if you go for 2 twin barrels!
But on an already injected engine you have the problem of the ECU.
You either have to ditch this completely and go for some kind of electronic dizzy set up with a TDC sensor or find an ECU that works with carbs.
I'm going to have to argue about carbs ever being better than injection bodies, Len.
No matter what carb you use, you need the venturi effect to draw the fuel through, so you need a restriction in order to get it...with ITBs you don't.
Carbs can be set up to work when hoy, or when cold, but most often don't 'do' both well. I've had enough sets over the years to know what a pain they can be.
You simply cannot get precise metering of the fuel, using carbs and a stack of jets...precisely why everything of any importance now uses injection bodies, not carbs.
With an injection car, that has an ECU controlling the ignition and fuelling, you can normally just disconnect the feed to the injectors and run the ignition side as is, to take care of the spark.
But the fuel pump will give FAR too high a pressure for carbs...so that needs to be worked.
Far better in my opinion to go for throttle bodies.
Absolutely.
And if the fitment is going to be on a car that's already injected, with all the sensors already fitted for engine management, I'd not even consider carbs...go straight to stand alone management and ITBs - be they bike ITBs of the likes of Jenvey.
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Carbs are good in fact great on the right car! Can be better than injection if you go for 2 twin barrels!
But on an already injected engine you have the problem of the ECU.
You either have to ditch this completely and go for some kind of electronic dizzy set up with a TDC sensor or find an ECU that works with carbs.
I'm going to have to argue about carbs ever being better than injection bodies, Len.
No matter what carb you use, you need the venturi effect to draw the fuel through, so you need a restriction in order to get it...with ITBs you don't.
Carbs can be set up to work when hoy, or when cold, but most often don't 'do' both well. I've had enough sets over the years to know what a pain they can be.
You simply cannot get precise metering of the fuel, using carbs and a stack of jets...precisely why everything of any importance now uses injection bodies, not carbs.
With an injection car, that has an ECU controlling the ignition and fuelling, you can normally just disconnect the feed to the injectors and run the ignition side as is, to take care of the spark.
But the fuel pump will give FAR too high a pressure for carbs...so that needs to be worked.
Far better in my opinion to go for throttle bodies.
Absolutely.
And if the fitment is going to be on a car that's already injected, with all the sensors already fitted for engine management, I'd not even consider carbs...go straight to stand alone management and ITBs - be they bike ITBs of the likes of Jenvey.
Couldn't of put that any better. Totaly agree
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Is this on an 8V or 16V engine as the ZX12R bodies are perfect for a 16V size wise and injector wise, even if you have to move the outer 2 bodies in by 3mm and do something similar with the fuel rail to make them fit with straight runners. Im in the middle of making a manifold up to do this for a MK1 owning friend and the biggest problem Ive had is getting the outlet of the bodies to fit to the inlet runners as the bore of the body is eccentric to the fixing boss (Ill get a picture once its a bit closer to being done at the end of this week coming hopefully lol).
However, if its for an 8V, ZX12R bodies are far too big (as said, about 46mm at the butterfly, 42-43mm at the outlet and about 48-49mm at the inlet) and the spacing will be way out due to the way the inlet ports enter the head. I want to do a crossflow head on injection in my own 8V Mk2 (Im a student at the mo though so I really dont have the money to do it lol) and Ive been looking at using early Suzuki GSXR600 bodies which are around 36mm bore which should be more than enough for the 8V's relatively rubbish breathing Whichever bodies you use, the spacing will be a nightmare due to the offset inlet ports.
Oh and as Ess Three said, dont bother with carbs, they may be different but they are not nice to set up and will give crap economy and emmisions (a big worry if you run a cat).
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Is this on an 8V or 16V engine as the ZX12R bodies are perfect for a 16V size wise and injector wise, even if you have to move the outer 2 bodies in by 3mm and do something similar with the fuel rail to make them fit with straight runners.
Ahh...here speaks a man who must have a set in his sticky mits! :smiley:
Im in the middle of making a manifold up to do this for a MK1 owning friend and the biggest problem Ive had is getting the outlet of the bodies to fit to the inlet runners as the bore of the body is eccentric to the fixing boss (Ill get a picture once its a bit closer to being done at the end of this week coming hopefully lol).
Please do post a pic.
I did think after I posted that a 16v is by far the easier, and best suited to the ZX12R bodies - that's that I was doing.
I managed to work out the spacings issues with slightly offset alloy tubes welded to a milled down 16v manifold (just the bit that bolts to the head), so leaving the bike ITB spacing the same, and removing all problems of fuel rail spacing etc. The ZX12R bodies are out by approx 2-3mm on the outside bodies as you say.
Not perfect for sure as two runners would be fractionally longer than the others...but easier than re-spacing the bike ITBs and re-doing the fuel rail etc.
However, if its for an 8V, ZX12R bodies are far too big (as said, about 46mm at the butterfly, 42-43mm at the outlet and about 48-49mm at the inlet)
Agreed...although, if you could get the inlet length long enough, you could claw back the torque you'd loose by having oversized ITBs (probably!) but there just isn't room on the 8v head if you stick to a standard head.
and the spacing will be way out due to the way the inlet ports enter the head. I want to do a crossflow head on injection in my own 8V Mk2 (Im a student at the mo though so I really dont have the money to do it lol) and Ive been looking at using early Suzuki GSXR600 bodies which are around 36mm bore which should be more than enough for the 8V's relatively rubbish breathing Whichever bodies you use, the spacing will be a nightmare due to the offset inlet ports.
Very true...
I know a few rally lads who use GSXR600 ITBs on 150-160 BHP cars and they work well.
The early ones as you say...single butterfly again.
If it were me, I'd just swap the engine for a 16v and go from there though...more to start with and much easier to get ITBs on as there's much more room to work with.
Almost always the bike ITB set up ends up longer from head to trumpet, than a similar set of Jenveys etc...which may cause major clearance problems.
Oh and as Ess Three said, dont bother with carbs, they may be different but they are not nice to set up and will give crap economy and emmisions (a big worry if you run a cat).
Amen!
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Finally got round to taking some pics of the finished manifold.
(http://thumb13.webshots.net/t/75/75/2/10/10/2802210100060011853aUGQZU_th.jpg) (http://rides.webshots.com/photo/2802210100060011853aUGQZU)
(http://thumb13.webshots.net/t/55/555/6/14/66/2985614660060011853dfWKeg_th.jpg) (http://rides.webshots.com/photo/2985614660060011853dfWKeg)
(http://thumb13.webshots.net/t/75/75/7/46/56/2917746560060011853illZXl_th.jpg) (http://rides.webshots.com/photo/2917746560060011853illZXl)
(http://thumb13.webshots.net/t/55/555/0/55/33/2470055330060011853pduDzm_th.jpg) (http://rides.webshots.com/photo/2470055330060011853pduDzm)
(http://thumb13.webshots.net/t/75/75/3/52/97/2797352970060011853DPfeQn_th.jpg) (http://rides.webshots.com/photo/2797352970060011853DPfeQn)
(http://thumb13.webshots.net/t/74/174/5/98/24/2366598240060011853wBbAaU_th.jpg) (http://rides.webshots.com/photo/2366598240060011853wBbAaU)
Just needs a paint and its good to go. Fuel rail didnt need any mods after all :smiley:.