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Supercharger

 
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KN
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Joined: 21 Jan 2006
Posts: 62
Location: Sydney Australia

PostPosted: Sun May 14, 2006 2:53 am    Post subject: Supercharger Reply with quote

I have recently acquired a roots type cabin supercharger Godfrey model 22 complete with a manifold specially cast to suit a Cortina 1500 engine, which I have for my Olympic phase2 ESU816.
It does fit as I have mounted it temporarly onto the engine, occupying the space where the generator lives. This means relocating the generater lower than its present position by making a set of brackets etc to suit.
At present the compression ratio is around 9.75:1 so I will need to drop this to something to suit 98/100 octane fuel 7lb pressure at around 5500 ->6000 rpm. I need to know how to work out what thickness head gasket or de-compression plate I need to acheive the lower ratio I need and what ratio that should be, approx 8:1?, Size of crank pully I need, the supercharger runs a dual belt 2 inch one, to acheive the required pressure at these revs. I have a manifold pressure guage ex Mk1 Spitfire. and a S.U HIF44 carb to suit. I need to make up a manifold to mount this to the S/charger and the brackets for the supercharger to the engine.
I also need a crankshaft pully & a blowoff/releif vavle to suit.
The engine has a worked head with larger valves & runs a Cosworth A3 grind cam which I am assured by the camshaft supplier, will handle these pressures. I can alter the cam timing as the timing gear is a dual row adjustable type.
Any advice will be gratefully received.
Regards Keith Nicholson.
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pfgascoigne
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Joined: 12 Mar 2006
Posts: 3

PostPosted: Fri Jun 15, 2007 8:51 pm    Post subject: Reply with quote

I would have thought 7:1 Cr would be nearer the mark. I can't see you getting down to that using a spacer plate. Spacer plate means two head gaskets instead of one, and I know from experience, thats not a good thing! I personally, would not fancy standard cast pistons with a supercharger, and as you will probably have to buy pistons, forged are probably the best bet. The States are the cheapest and best, Ross's Racing Pistons or Venolia have lots of experience with supercharging, are helpfull and very reasonable.
Compression Ratio=(Swept Volume+Combustion Chamber Volume) divided by Combustion Chamber Volume.
I think (its been a long time!) I don't know how superchargers are rated. There must be a manufactuers plate on it some where, if its X psi at Y revs then life is relatively simple, but if its X cubic feet @ Y revs.....
The fact that it has cast manifold suggests that its not the only one in the world. Classic Ford tuners must know about it, Burtons have been around long enough to know, or could tell you who would.
You are sure to need bespoke pulleys to get the right speed. Your local friendly one man band machine shop should help you here, if you wave cash. They will be need to be made out of an ally billet, so won't be cheap. And if you do get it all set up, please don't think about driving it untill you get it rolling-roaded by a man who knows about SU carbs and old fashioned distributor advance curves. Both the carb and the dizzy are likely to be so far out, that if you are at all enthusiastic with the throttle, your new forged pistons will be history.
Eureka! Put "Godfrey superchargers" into Google and go to "Old Classics"
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KN
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Joined: 21 Jan 2006
Posts: 62
Location: Sydney Australia

PostPosted: Sat Jun 16, 2007 7:47 am    Post subject: Supercharger Reply with quote

Thanks Pfgascoigne for your input. The engine has already been built fortunalty with all the good internal bits

Co-incidendally I managed to contact the man who made the manifold & the intake manifold. He has long since retired from playing with superchargers but was very helpful with his advice and backs up much of what you say re: CR 7:1 and carburation etc. He was very useful in giving me leads on who can make me a crank pully to suit & suggest an overdrive of twice crankshaft speed to supercharger speed max as a starting point as the Godfrey MK22 is approximatly equivilent to a Nordec Marshall 75.
As for the distributor that has been rebuilt & regraphed to suit its current configuration so I will need to take it back to the engineer who did it originally. He also has a dyno and is a past master on Su Carbs.
As for the website reference old classics thanks again. It has not come up before last year when I Googled Godfrey cabin blowers.
Need now to fabricate carb inlet side. A modified Ford Falcon efi inlet runner could solve the problem. Also still need a blow off valve, an air compressor relief valve I have looks promising, and other bracketry.
Regards Keith. Ph2 ESU816
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Dave-M
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Joined: 20 Jan 2006
Posts: 295
Location: Yorkshire, England

PostPosted: Thu Oct 18, 2007 7:17 pm    Post subject: supercharger Reply with quote

Keith, Are you still in the engineering stage with fitting your blower? If you are let me know as I may have some useful information for you.
If you have it completed as I suspect you have, let us know how it's going.
Regards
Dave
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Ph.2 Ford 1500 GT
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KN
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Joined: 21 Jan 2006
Posts: 62
Location: Sydney Australia

PostPosted: Fri Oct 19, 2007 12:33 pm    Post subject: Reply with quote

Hi Dave,
Still engineering the project. Am making up a crankcase pully at present. Also designing an intake manifold for the carburettor side. Space is limited so taking trial & error approach mocking up various configurations.
Still after a blow -off valve,though one from an old compressor looks promising, it is adjustable and with a weaker spring should work. I don't need 120lb/sq inch it is now set to.
Any info will be gratefully received.
Regards Keith
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Dave-M
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Joined: 20 Jan 2006
Posts: 295
Location: Yorkshire, England

PostPosted: Thu Nov 01, 2007 12:35 pm    Post subject: blower Reply with quote

Keith, over the next few days I will take some picture of my pre crossflow/ shorrock set up.
I will include as much tech info as i can including how to modify the ditributor.
Regards
Dave
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Ph.2 Ford 1500 GT
GT with Rochdale Chassis
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KN
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Joined: 21 Jan 2006
Posts: 62
Location: Sydney Australia

PostPosted: Fri Nov 02, 2007 9:44 am    Post subject: Reply with quote

Thankyou Dave
Look forward to your details,
Regards Keith
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zefarelly
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Joined: 26 Nov 2007
Posts: 91

PostPosted: Thu May 15, 2008 9:48 am    Post subject: Reply with quote

I'd be interested to see/know how this all goes, I'm building a 1300 precrossflow soon with a blower, when I can find a suitable one to use.

we're planning forged pistons, steel rods, big end caps, rephased cam ( wider lobe angles to reduce overlap, 9:1 static CR, easiest was to lower a std 1500 is to open up the chambers, you can deshroud a big valve head and get 45cc quite easily
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KN
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Joined: 21 Jan 2006
Posts: 62
Location: Sydney Australia

PostPosted: Thu May 15, 2008 10:48 am    Post subject: Reply with quote

Hi
9:1 C/ratio static plus depending on how much boost you're planning, leads me to ask, are you going to run Methanol?
Effective ratio will be somewhere around 12:1 plus depending on the parameters you have set.
Regards Keith Nicholson Ph2 Olympic ESU816
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zefarelly
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Joined: 26 Nov 2007
Posts: 91

PostPosted: Thu May 15, 2008 11:30 am    Post subject: Reply with quote

12:1 is where my NA race engine runs, proper petrol, either leaded 4 star or 99 and CVL, thats nearly 140 bhp in FiA trim

I think with decent petrol and sensible boost we're aiming for 160-170 bhp from 1300, I've already got close to 120 from a pretty std 1300 precrossflow and a lovely flat torque curve
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