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I'm currently running an eaton charger with a suck through 45 webber, I'm intrested in converting to a blow through system, could I get some advise on what carb, intercooler and hoses to use and where to purchase them?

Carb wise you will need a sealed unit and there are only two real options (although there may be others):

SU HIF 44 off the Metty Turbo which 99% of the people on this board use.

Delorto Turbo Carb of the Lotus Turbo (and presumably others) as was fitted to the JanSpeed Turbo kit in the yellow book. Very few people use these as the HIF seems good enough (although Vizard has some interesting comments) and they're relatively cheap & plentiful.

Intercooler, most people use whatever fits, Costworth IC & RST IC are the most popular two but there are many others. A while back Robert posted some interesting info on the flow rates of different ICs.

Also you will need a big arse (technical term) bypass valve as positive displacement superchargers still produce boost off throttle (assuming the throttle is after the supercharger)

If you have a look at this link there is quite a bit of back ground info, which might be of some help to you.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=128332

IC and hosing is a suck it and see matter, whatever fits is the answer there!!

The Dellorto 40 carbs that Lotus (and Lancia/Fiat I believe) used is a good bet as they are designed to seal against boost. The seals on NA carbs are designed to prevent air being drawn in not blown out......

I would not use a 45, will be a pain to jet properly for light load work so will drive like a pile of poo at low revs.

To be honest I probably wouldn't bother with a Webber, an SU will make a much more drivable engine and I am sure that the Eaton (assuming that it's a 45) will run out of puff before you max out the carbs capability.

Make sure your plenum features the same restrictions and drillings as the Metro one or else you'll have all sorts of running problems.

Finally make sure you have a proper supercharger spec BOV as havin the butterfly after the compressor will mean huge potential pressures in the plenum as the throttle is snapped shut and BOVs for turbos just can't shift that much air and may even try and reclose too early as throttle opens.

With a carb I'd always go for a suck through myself.

Every day is a school day ...........

How fast and how expensive ...... the same question...

You type faster than me Rob

Every day is a school day ...........

How fast and how expensive ...... the same question...

Thanks for the advise, i've been reading through the links you've posted and it does say that on a twin screw charger (eaton m42) the throttle body must be placed before the charger. I understand that a 'big arse' bypass valve may also work, i'll have another search through those sites to see if theres a company selling parts (throttle body and carb).

The configuration i'm running at the moment has probably reached the limit of power that can be produced with a suck through eaton charger.

I already have 2 chargers and plan to purchase another 1 or 2 while they are in plentiful supply.

So part of my thinking was to try to run a pair of chargers that will run in series. By doing this the system would almost certainly need to be converted to a blow through and also run an intercooler

I personally think you'd be better off with a turbo as the set up you describe would probably be quite inefficient.

Every day is a school day ...........

How fast and how expensive ...... the same question...

I've been researching this a bit more since the other post.

Blow thru is better because the blower needs mass air flow rather than volumetric air flow to keep it cool at low load. This is why the OEMs use blow through.

However, you must have a way of allowing the blower to pass air without pressurising the inlet when the throttle is shut or slightly open.

Some of the OEMs use an electric clutch on the blower drive, whereas some use a big bypass valve that returns the flow to the inlet of the blower, therbey reducing the blower load and keeping it cool. The bypass valve could be controlled by manifold vacuum.

I think it is doubtful if a big BOV would work for a road application.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Do you think there is any potential in using twin throttle cables, one connected to the carb and the other connected to a throttle body mounted on the inlet of the charger

Edited by Paul S on 14th Jan, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On a suck through system dose'nt the throttle closing reduce the flow of air into the charger

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Its not really a cruiser and with twin chargers would be even less so.
So if the answer is yes that the throttle reduces airflow, then is there a posibility of my proposed throttle body on the inlet working

How about fitting an intercooler to your suck through setup?

You could gain up to 20-30% more power.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

To keep the charger(s) cooler I was considering fitting water injection at the inlet.