Author Topic: thoughts on carbs?  (Read 3666 times)

Offline shepgti

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thoughts on carbs?
« on: 03 July 2009, 14:26 »
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:


Offline shepgti

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Re: thoughts on carbs?
« Reply #1 on: 03 July 2009, 15:01 »
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

Offline Khare

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Re: thoughts on carbs?
« Reply #2 on: 03 July 2009, 15:05 »
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.

Offline Wayne

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Re: thoughts on carbs?
« Reply #3 on: 03 July 2009, 15:19 »
Yamaha R1 seems to the most used set up, I would think the biggest issue would be passing the mot maybe.

Offline Ess_Three

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Re: thoughts on carbs?
« Reply #4 on: 03 July 2009, 15:27 »
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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Offline tweed

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Re: thoughts on carbs?
« Reply #5 on: 03 July 2009, 20:12 »
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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Offline Len

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Re: thoughts on carbs?
« Reply #6 on: 03 July 2009, 20:17 »
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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Offline Adam

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Re: thoughts on carbs?
« Reply #7 on: 03 July 2009, 20:50 »
Yumm.....16V on TBs......idea....

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Offline tweed

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Re: thoughts on carbs?
« Reply #8 on: 03 July 2009, 21:58 »
there was a 16v with jenvey bodies on ebay. looked sexy as fook!

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Offline Ess_Three

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Re: thoughts on carbs?
« Reply #9 on: 04 July 2009, 05:58 »
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.


Quote
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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..but gaining motorcycles.