Craigorypeck
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| posted on 13/12/10 at 12:26 AM |
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Supercharging through bike carbs
Anyone on here done it?
Maybe an M45 geared up to give around 6psi.
Blowing through a set of bike carbs
Can the float bowl be pressurized via the breather vent?
Will the slider operate as normal?
As the pressure will be linear will fuelling be setup as per usual?
What boost will bike carbs handle?
I have a red top and filter king, would that be sufficient?
Any info would be great!
Cheers
[Edited on 13/12/10 by Craigorypeck]
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rayward
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| posted on 13/12/10 at 12:46 AM |
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some interested reading here
Ray
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Craigorypeck
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| posted on 13/12/10 at 01:13 AM |
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quote:
Originally posted by rayward
some interested reading here
Ray
Thanks, it's been book marked!!
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atspeed racing
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| posted on 13/12/10 at 08:21 AM |
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I remember a friend of mine tried this with a stromberg carb years ago and it was a fail!!
The Stromberg carb has a rubber diaphram like a bike carb and we run into all sorts of dramas, we believe due to that.
We gave up in the end with set up, and we replaced it with an SU, wasnt a problem from then on. If you used an SU, you can get one from a MG turbo and
bolt it straight on.
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Craigorypeck
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| posted on 13/12/10 at 12:32 PM |
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I was thinking that would be the case regarding the slider...
A set of turbo 45 dells would be a good option. Expensive and hard to find!
I'll have a look at the MG option maybe.. Is that a draw thru setup?
Thanks
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andkilde
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| posted on 13/12/10 at 01:17 PM |
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Might be easier to setup with bike TB's and a boost referenced fuel pressure regulator. A lot less jiggery pokery than carbs would be. Though
you would need to fit a suitable ECU...
Cheers, Ted
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atspeed racing
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| posted on 13/12/10 at 05:27 PM |
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The MG Metro SU is a blow through. You will need to get a rising rate fuel pressure reg and a high pressure pump, all available of the shelf, easy to
calibrate and reliable. No ECU no trickery....and cheap!!
If you where to take the option of Webers or Dellortos, you will need to modify them as most of them are not suited to blow through.
You could use a 2 inch SU from a Jag, and use this as a suck through. I have calibrated this setup on a Pre war supercharged Bentley. went really
well. Over 250 BHP at the tyres at 1800RPM.
As this is a supercharged engine, this might be the way to go?
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Craigorypeck
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| posted on 13/12/10 at 07:35 PM |
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If at all possible I'd like to keep the ecu and wiring to a minimum.
I have a megajolt for 3D ignition, thats as far as I'd like to go.
I think for turbo motors an injected ecu is prob a must but as a supercharger is linear, fuelling should be easily done on a carb??
A kit can be got from dellorto.co.uk to convert regular DHLA's into turbo models, spindle bearings that seal and a top cover with a float bowl
pressure connection.
Are choke sizes as important when being force fed??
I have a set of DHLA 40s with 34mm chokes, these would be restrictive on my engine if I was to run N/A, but would they work ok being blown on?
Is a blow off valve necessary on a charger?
Cheers
[Edited on 13/12/10 by Craigorypeck]
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FASTdan
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| posted on 14/12/10 at 08:09 AM |
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I would like to convery my XR2 turbo (currently turbo technics converted, using the standard weber 32/34DFT) to turbo-bike carbs. Surely it cant be
that impossible as there are many turbo'd bikes about?
Renault 5 turbo carbs are popular in the XR2 circles for a cheap turbo option, but I want something different.
NEW danST WEBSITE NOW LIVE! Bike carbs, throttle bodies and more......
http://www.danstengineering.co.uk/
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ianjenn
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| posted on 14/12/10 at 09:02 AM |
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here is a supercharged pinto with bike
carbs
Surely it is alos possible with a zetec
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atspeed racing
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| posted on 14/12/10 at 09:40 AM |
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The trouble with other peoples work is you cant see what the end result was like? Did it run but had calibration issues like we had with the
Stromberg? Our car ran, but the mixture was all over the place and the consumption was very poor.
A renault 5 carb is a blow through carb, thats why it is popular on XR2's and the like.
You can use Dellortos or weber 40/45's, but you have to make sure you have blow through modified ones, otherwise it wont work.
If you had a large SU as a suck through, you shouldnt need anything special apsrt from making a manifold up.
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ianjenn
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| posted on 14/12/10 at 11:07 AM |
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rolling road results from pinto
his results look pretty impressive to me from a pinto
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MikeRJ
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| posted on 14/12/10 at 11:28 AM |
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quote:
Originally posted by FASTdan
I would like to convery my XR2 turbo (currently turbo technics converted, using the standard weber 32/34DFT) to turbo-bike carbs. Surely it cant be
that impossible as there are many turbo'd bikes about?
There are very few turbo'd bikes around, the older production ones such as the CX500 and GPZ750 turbo are rare for good reason - they were
pretty rubbish. Modern stuff with aftermarket turbo conversions will most always be fuel injected.
If you are going to all the hassle of changing out the original carb you'd be a lot better off with converting to fuel injection as well.
Setting up bike carbs properly on a normally aspirated engine is bad enough, but add boost correction into the equation and it will be a PITA.
[Edited on 14/12/10 by MikeRJ]
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FASTdan
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| posted on 14/12/10 at 12:56 PM |
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quote:
Originally posted by MikeRJ
If you are going to all the hassle of changing out the original carb you'd be a lot better off with converting to fuel injection as well.
Setting up bike carbs properly on a normally aspirated engine is bad enough, but add boost correction into the equation and it will be a PITA.
[Edited on 14/12/10 by MikeRJ]
I dont fancy fuel injection, I like the uniqueness of the TT kit and going to injection would just make it like the millions of other RS turbo or
zetec turbo'd XR2's.
Plus fitting bike carbs is a relative piece of cake for me, fabricate a manifold and plenum, bolt together. its almost swapping like for like.
My experience of bike carbs on NA has been that they are dead simple to set up? How complex it becomes with boost pressure I am not sure, but given
that you can provide a boost reference to the relevant parts of the carb (floats etc) I thought it would be a decent upgrade over what I have - which
itself is a NA carb boosted. Reckon it'd cost me £100 or so to convert (lots of my time of course), compared to big bucks to go EFI or the
like.
Suck-through carb set-ups scare the hell out of me lol. There's something about passing fuel through a hot turbo that doesnt seem quite right!
NEW danST WEBSITE NOW LIVE! Bike carbs, throttle bodies and more......
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ianjenn
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| posted on 14/12/10 at 09:37 PM |
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more interesting reading
pressurise carb for turbo
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Craigorypeck
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| posted on 14/12/10 at 10:04 PM |
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Dan, I'm with you as regards to avoiding fuel injection and suck through chargers !
I have both a set of ZX9R's and a set of DHLA40F, the dellortos can be converted to run blow through with these-
http://www.dellorto.co.uk/Merchandise/products_details.asp?PartNo=DHLAturbokit&CategoryID=1&PartsectionID=1
My only concern is my dells are emission spec and cant find much info on using them to blow through but I'm at least familiar with setting them
up.
Bike carbs are pretty new to me so I'll set them up to run NA and see how they run, do more research on charging them and take it from
there..
Thanks for the links too!!! Good bedtime reading...
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FASTdan
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| posted on 15/12/10 at 07:48 AM |
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quote:
Originally posted by ianjenn
more interesting reading
pressurise carb for turbo
Thats an excellent link thanks 
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http://www.danstengineering.co.uk/
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MikeRJ
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| posted on 16/12/10 at 12:28 PM |
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quote:
Originally posted by FASTdan
My experience of bike carbs on NA has been that they are dead simple to set up?
They are fairly simple to get the engine running at on "ok" level, to set them up properly is a much more complex affair. I suspect the
majority of bike carb installations are somewhat less than optimal. Then again that applies to the majority of DCOE installations as well.
quote:
Originally posted by FASTdan
How complex it becomes with boost pressure I am not sure, but given that you can provide a boost reference to the relevant parts of the carb (floats
etc) I thought it would be a decent upgrade over what I have - which itself is a NA carb boosted. Reckon it'd cost me £100 or so to convert
(lots of my time of course), compared to big bucks to go EFI or the like.
The problem is that a carburettor is an inherently velocity sensitive device, for blow through forced induction applications you have to make them
pressure sensitive as well. Simply applying boost pressure to the float chamber etc gets you back to the same state that you were with a normally
aspirated set up, which isn't what you want. The mixture needs to be richened as boost pressure increases if you want you engine to last more
than 5 minutes. Have a look at how the SU was modified on the Metro and Montego Turbo to cope with this.
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Craigorypeck
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| posted on 19/12/10 at 12:04 AM |
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The problem is that a carburettor is an inherently velocity sensitive device, for blow through forced induction applications you have to make them
pressure sensitive as well. Simply applying boost pressure to the float chamber etc gets you back to the same state that you were with a normally
aspirated set up, which isn't what you want. The mixture needs to be richened as boost pressure increases if you want you engine to last more
than 5 minutes.
Can you enlighten me a bit further?? I thought that getting the carb to work as if it was running NA but under pressure was the ideal situation, By
simply applying boost level from the air box to float bowl?
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FASTdan
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| posted on 20/12/10 at 07:54 AM |
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I just plan on the usual rising rate regulator. I might push the boat out and get one with an adjuster screw on the top lol.
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NS Dev
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| posted on 20/12/10 at 03:07 PM |
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quote:
Originally posted by FASTdan
I just plan on the usual rising rate regulator. I might push the boat out and get one with an adjuster screw on the top lol.
On a carb that will unfortunately do bugger all.
In terms of fuel pressure on a carb you can only have enough fuel or not enough, you can't "richen the mixture" via fuel pressure.
All the fuel pressure does is open the float needle! pressurising the carb just makes the float needle work as if it didn't have force fed air
on one side of it by applying it to both sides.
Its not what you'll wish to hear but injecting a turbo installation is by FAR the easiest solution. (and even then, at high boost it gets very
tricky in terms of mixture distribution , charge robbing between cylinders etc etc, on the 500hp XE in our opel kadett we've hit all this! )
cheers
Nat
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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FASTdan
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| posted on 20/12/10 at 04:20 PM |
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It won't do Bugger all at all. Without it there won't be any fuel on boost.
The system works.......it might be crude but I did 30k on that blown, shonky weber with fueling permanently monitored on a wideband (11.5-12.6afr thru
revs).98mph terminals at York so its no slouch.
I just figured bike carbs would be a nice cheap upgrade, probably never happen tho as I'm struggling to even finish the resto.
NEW danST WEBSITE NOW LIVE! Bike carbs, throttle bodies and more......
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MikeRJ
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| posted on 21/12/10 at 09:25 AM |
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quote:
Originally posted by Craigorypeck
Can you enlighten me a bit further?? I thought that getting the carb to work as if it was running NA but under pressure was the ideal situation, By
simply applying boost level from the air box to float bowl?
No, because you don't get the enrichment required as the boost increases. The SU carb used on the Metro/Montego used a second venturi at the
mouth of the carb to create a pressure drop, meaning more pressure at the float chamber vent than at the jet.
You also need to consider things like whether the floats are capable of taking the pressure without collapsing, whether the throttle spindles are
adequately sealed, whether the design is capable of flowing enough fuel etc. You don't want a rising rate regulator either, you simply need a
standard regulator referenced to boost pressure in order to keep the fuel feed a few PSI above boost.
Carbs have always been a big compromise, and never more so than in a turbo/supercharged application. Fuel injection is the only sensible route these
days IMO.
[Edited on 21/12/10 by MikeRJ]
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NS Dev
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| posted on 21/12/10 at 09:47 AM |
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quote:
Originally posted by FASTdan
It won't do Bugger all at all. Without it there won't be any fuel on boost.
The system works.......it might be crude but I did 30k on that blown, shonky weber with fueling permanently monitored on a wideband (11.5-12.6afr thru
revs).98mph terminals at York so its no slouch.
I just figured bike carbs would be a nice cheap upgrade, probably never happen tho as I'm struggling to even finish the resto.
As long as you feed the boost pressure to the reference port on a regulator then the fuel pressure will stay at whatever you set PLUS the boost
pressure, i.e. it will compensate for the boost.
What is WON'T do will be to compensate as the boost rises and allow a fuel slope to be set to richen up the mixture as charge temps rise, (read
Mike's bit above)
This might be no problem if your existing carb setup is running too rich anyway, then you'll be fine.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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FASTdan
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| posted on 21/12/10 at 09:57 PM |
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I'm getting mixed up there with terminology by the sounds if it, I always understood a fpr with boost reference was a 'rising rate'.
I currently run one from a metro turbo - with boost ref.
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