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Using bike carbs on a Duratec V6
trogdor - 4/2/09 at 05:46 PM

Hi all,

I am planning to use bike carbs on my Duratec V6 I was thinking of using the original injection system or bike throttle bodies but carbs would be simpler. Apart from the manifold that is.

The duratec has a strange two port arrangement where one port has an injector over it and the other has a throttle plate arrangement that is controlled by the ECU. I am not 100% sure what it does but i think Razman would know. I think he removed his to improve breathing.

Anyway to get to the point i need to find a way to mount the single port of the carb to this dual port.

I have taken some pictures to help, I would like to use the original lower manifold if i can, Am planning in the future to possibly merge the two ports but for now will leave them as they are.

So, if anyone has any idea how to mount these carbs to the manifold in the picture i would like to hear it!

Cheers


trogdor - 4/2/09 at 05:50 PM

oops would help to have some pics!




mr henderson - 4/2/09 at 06:36 PM

I have a feeling that the original arrangement is designed to keep the gas speeds up at lower rpm (to improve cylinder filling and torque). Have you considered keeping it as is, I believe it works very well?

John


coozer - 4/2/09 at 07:04 PM

Another plug for Bogg Brothers


grazzledazzle - 4/2/09 at 07:15 PM

Hello,
First thing is ditch the secondary butterflies. They operate via a seperate control unit mounted on the cam cover of the rear bank of cylinders. It's designed to increase torque at low revs but all it actually does it strangle the engine. Plug the holes left with something suitable.

Why carbs? Are you aware you won't pass post 95 emissions with them? Or is the idea to keep the lower inlet manifold with the injectors in and use the carb purely as a butterfly valve? Which ever way you go you will need a new ecu and mapping, so why not got 2 sets of triumph throttle bodies with injectors (they are port shaped and a very good match for the inlet ports on the head) and mount them using some thick ali plate? the good thing is the inlets from the head are turned upwards and are almost horizontal so very easy to do.


jacko - 4/2/09 at 07:19 PM

Do you want the carbs vertical or horizontal ?
How about round tube squashed at one end to make it oval to cover the two holes if you want them horizontal use curved bent tube
Just my input
Jacko


trogdor - 4/2/09 at 07:27 PM

some good ideas there, I did consider triumph triple carbs but they are not so easy or cheap to find. I did not realised they were port shaped tho so may consider them.

Emissions is not an issue as the engine is going in a 1976 saab 96 so will be tested to its original emissions.

I already have a megajolt lying around so is another reason to go with carbs.


grazzledazzle - 4/2/09 at 07:41 PM

Fair enough.
Jenvey do inlet manifolds for the engine for mounting single throttle bodies.
They are mega money though. (about 600 quid!)


trogdor - 4/2/09 at 07:49 PM

yeah I am trying to spend as little money as possible since i don't have any! The four GSXR's cost £21 from ebay, just need another set to make up the other two. Since they split up I can remove one and only need to get shorter bolts to hold them together.

However to match the port spacing of the duratec they need to be more spaced out needing longer fuel pipes etc so am tempted to keep them the standard distance and angling the manifold runners to suit


flibble - 4/2/09 at 08:40 PM

With some flanges welded on would there be any way to utilise the 2 into 1 exhaust collectors?


clairetoo - 5/2/09 at 06:26 AM

I didnt find the Triumph `bodies either expensive or hard to find - I payed a total of £65 for two sets


trogdor - 5/2/09 at 09:12 AM

well admittedly i didn't look much further than ebay! I didn't expect to win these carbs, I have a habit of putting in the bottom bid for stuff that I want and I very rarely win.

This is one of those times.

Those exhaust collectors look like a good way forward, where can I get them from?

Cheers


MikeRJ - 5/2/09 at 10:10 AM

quote:
Originally posted by grazzledazzle
Hello,
First thing is ditch the secondary butterflies. They operate via a seperate control unit mounted on the cam cover of the rear bank of cylinders. It's designed to increase torque at low revs but all it actually does it strangle the engine.


At low RPM it doesn't strangle the engine, since gas flow is low. This is the exact reason for their existence, to raise gas speeds and improve cylinder filling (and hence torque) at lower RPM.


flibble - 5/2/09 at 12:29 PM

Unfortunatly I just pulled a piccie of the exhaust collectors from a random exhaust website:
http://www.coneeng.com/collectors.html
I was making an assumption that they'd be easy to find anywhere but I can't seem to find any in the UK, others must know of such places to buy these things from though


trogdor - 5/2/09 at 01:50 PM

I have found a place in the UK that may do a collector that will be suitable.

i need to measure the sizes i need. There is a place in the USA that will deffo have what i need.


grazzledazzle - 7/2/09 at 10:49 AM

quote:
Originally posted by MikeRJ
quote:
Originally posted by grazzledazzle
Hello,
First thing is ditch the secondary butterflies. They operate via a seperate control unit mounted on the cam cover of the rear bank of cylinders. It's designed to increase torque at low revs but all it actually does it strangle the engine.


At low RPM it doesn't strangle the engine, since gas flow is low. This is the exact reason for their existence, to raise gas speeds and improve cylinder filling (and hence torque) at lower RPM.


I understand the theory. On a rolling road both power and torque were up without the system when mapped properly. Bin it.


trogdor - 7/2/09 at 03:33 PM

don't worry i will, however i am getting tempted with other engines at the mo, the duratec i have at the mo is only really fit to use as a template or dummy block.


major - 11/2/09 at 06:06 AM

It is no carb solution but.........

nice intake
nice intake


RazMan - 13/3/09 at 05:33 PM

quote:
Originally posted by trogdor
I am not 100% sure what it does but i think Razman would know. I think he removed his to improve breathing.




Just found this thread so apologies for the late reply.

On my V6 I removed the secondary butterflies to improve the breathing - they only serve to increase gas speeds at low revs so a lightweight car wouldn't really benefit much - and it was a sod to map


quote:
Originally posted by grazzledazzle
Plug the holes left with something suitable.


On the contrary, open them both up or you will strangle the engine.

As for nailing the carbs on, all I know is that Triumph carbs have been used to good effect ..... but thats all I know

[Edited on 13-3-09 by RazMan]