998 Supercharger
Turbo Mini Forums

As my Midget is finish and the 1293 T2 engine for the British Open is coming together quite nicely, I've decided it's time to look for a new project.

So I'm thinking about building a "budget" track car and going down the 998 route so that I can potentially try a bit of Hill Climbing & Sprinting, but instead of going for a turbo I'm thinking about going for a supercharger purely to be different.

Rather than doing for the traditional rear mounted suck through set up, that all the companies are selling (that would be too easy and would eliminate the design work which is my favourite part of the project) I'm thinking about a front mounted supercharger with intercooler & a blow through carb. Hopefully this should allow me to run more boost and thus make more bananas. Obviously I will require a clubby shell so that I can fit all the boost making paraphernalia in the engine bay and still close the bonnet.

As for choice of blower I'm thinking about an Easton M45 to start with purely because they are cheap, however I've not heard of one being used on a 998 before so there are a few unknowns. As I see it a positive displacement supercharger displaces X amount of air per rotation therefore if you decrease the size of the engine which the blower is feeding, then boost must increase, but I'm only an quasi electronics engineer so I've probably got that totally wrong. Also I should be able to wind up the boost a bit more by using a smaller pulley if needed.

I am however having a bit of trouble working out where to get a crank pulley from, although there are now several companies who sell supercharger conversions, I've yet to find one that will sell the pulley on it's own.

As for the engine it's self I was initially going to use any old 998 to start with and see how long it lasts, whilst building a decent bottom end in slower time. However I'm thinking of fitting a 12G295 head with enlarged chambers to reduce the static CR to a sensible level.

Does it sound a good idea or a total no go, or somewhere in between?

i havent a clue about superchargers, but a close friend is currently using a M42 (no idea why) to supercharge his R1 engined kitcar.

maybe its a better choice (or maybe its all gippo could get his hands on..?)

doubt you will need to enlarge the chambers much on a 295, unless it has already been skimmed, as std they have 28.3cc chambers :)

as for pulleys, if it were me id work out the ratio i needed then scavenge the scrappies for loads of different muilt v pulleys, see if i could get a close match?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

sounds like an ace project, this is my supercharger calculator -

http://uk.briefcase.yahoo.com/twin_charged

In the turbo stuff folder there is an excel file, this will calculate everything you need to know including temperature rise boost etc. All of the blue boxes can be changed to suit your engine, ths current numbers are for my 930 imp engine and an eaton M45 blower.

Pulley set up can be got from here -

http://fp.transdev.plus.com/index.htm

I used one of these belts -

http://fp.transdev.plus.com/pages/belts/sy...ex/t10_main.htm

Check out my supercharged imp here -

http://turbominis.co.uk/forums/index.php?p=vt&tid=121495

J

try this for the supercharger calculator -

http://us.f13.yahoofs.com/bc/449efa40_15cb...fVkKhFBK_4CHSxr

J

im in the middle of building a friend a supercharged 998, front mounted m45 with an intercooler and a blow through carb. Another chap on here has done the same thing with a 1380. Definatly the way to go IMO.

regarding the head, im going to use a mayfair/non mg metro 1275 head with 35/29 valves.

I've seen the future and tbh its Pie

J, Your excell file still wont download.

I've seen the future and tbh its Pie

I dont think you can do a blow-through setup with a positive displacement supercharger. It will all go bang.

You need to suck-through or use EFI with a throttle body upstream of the blower.

Problem with the M45, is that is is not very efficient above a 1.5 pressure ratio which works out at about 8psi boost.

As you have probably guessed, I'm researching the same idea.

For my next project, I'm planning on using a M45 with a GT17 or GT20 and twin intercoolers to give 30psi boost efficiently. A 1.4 pressure ratio on the blower and 2.3 on the turbo, both operating at their most efficient.

Needs a secret cam of course

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."

The efficicency of the M45 isnt too bad, They can be ported and the noise reduction ports sealed to increase the efficiency.

What makes you think it will all go bang axel?

A blow through set up will be fine as its no different to using a turbocherger setup, the only difference being the need of a decent bypass valve to prevent sticking throttles and boost spikes on overrun.

Here are the maps for a fifth generation eaton M45 (not many people know you can get thses!) -







Cheers

J

p.s. I paln on twincharging my imp once the blower setup is complete, mine will be sequential though.

There are obviously many maps!

Attachments:

27.53kb

Edited by Paul S on 17th Dec, 2006.

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."

This is a good site for supercharger stuff.

http://www.superchargersonline.com/content.asp?ID=76

"Like the roots, the throttle body must be placed before the compressor because it is a fixed displacement supercharger."

From a scientific perspective, if you throttle the inlet to a positive displacement compressor, it will still compress, but you will still have a vacuum on the other side.

If you just let air in it will compress it and it needs to go somewhere, else it will just keep increasing the pressure until something breaks.

You can bypass the blower, or just dump the air. Its the same reason we use dump valves on turbos, but with a supercharger, the compression does not drop off at light loads.

If you have designed for, say 15psi boost, then the blower is chuffing the equivalent of 2 litres of air (998 ) every 2 revs. That is hell of a lot to bypass.

Edited by Paul S on 17th Dec, 2006.

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."

Exactly, you need a specific supercharger bypass, which is very different to a turbo dump valve -



Throttling the inlet of a supercharger drastically reduces its efficiency, overheating any air that gets through and heat soaking your intercooler. Putting the throttle after the blower means its always working at it best, reducing inlet temperatures.

Did you check out my calculator? Its very informative about inlet temperatures regarding efficiency and engine volume.

Cheers

J

It would appear that the calculator isnt availble to download if im not logged in. Can it be saved on this site? Its ony about 20kb in an excel file.

J

Glad to see you have it covered with that wastegate.

I think you can "attach" .xls files

Edited by Paul S on 17th Dec, 2006.

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."

Blown_imp ... if not I'll host it .. loads of space and nothign to fill it ... LOL

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

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

Lets try this -

Edit - .xls files wornt attach, looks like i need a host!!

Edited by blown_imp on 17th Dec, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

On 17th of Dec, 2006 at 10:15am Axel said:
Needs a secret cam of course

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

whoops , iv just realizeed , the bini cooper s has the throttle after the blower , so does my sisters db7 ,doh , so sound like im talking drivel , !!!!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

There shouldent be too much of a problem with distortion as the volume of the inlet system after the throttles is far smaller than the volume prior. When the throttles close the area after is evacuated very quickly pulling the valve open, the area prior wont have much time to 'pump up' in consideration of the time and volume of air being moved.

I thought about the inlet charge cooling through vacuum, but the part affected is only prior to the throttle. When it is shut the air before the supercharger will indeed be under a vacuum and cool down, but post supercharger the air will still be moving and under the influence of the supercharger.

What has to be remembered here is that the roots type supercharger does not 'pull' air in, it relies on the atmospheric pressure to fill the gaps produced between the rising lobes. If this available pressure is dropped then the supercharger efficiency drops and equal amount. So any air moving through the supercharger under these conditions will be affected by the decreased efficiency, the energy imparted by the lobes will be in the form of heat rather than pressure.

This is in my brain anyways, its pretty messy in there too!!

Cheers

J

p.s. im going by the stuff that was used in the group B era, and personal knowledge.

Edited by blown_imp on 17th Dec, 2006.

Attachments:

59.69kb

Edited by Paul S on 17th Dec, 2006.

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 17th of Dec, 2006 at 04:17pm robert said:

On 17th of Dec, 2006 at 10:15am Axel said:
Needs a secret cam of course

blooody funny axel you do make me laugh .thanks .

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."

Thanks for all the input so far, its definitely me a fair bit to think about, and those maps make by little brain hurt.

Right here is my supercharger calculator, really really!

http://www.turbominis.co.uk/up/calculator_...ercharger-1.xls

Thanks to AlexB for hosting it on the best website/forum on the net

This is what can be done with the supercharger, bit OT but it shows that the eaton is capable of high PSI unintercooled -

487 hp @ 7,300 rpm
11.2:1 static compression

Endyn takes an Eaton M-62 supercharger, rips out the guts and replaces and reworks everything with an eye to increasing flow and reducing the temperature of the intake charge. Carbon fiber rotors (80 percent lighter than the stock pieces) are installed with zero clearance between the rotor and case. The exit side is smoothed and aluminum half-rounds are welded in place to increase the flow. The mods result in an increase from the stock 12 psi to an incredible 27 psi!



Full article here -

http://www.hotrod.com/featuredvehicles/228...honda_civic_si/

Endyn blower stuff here -

http://www.Theoldone.com/

Supercharger porting info -

http://www.theoldone.com/articles/blowers-and-howto.html

Good info on the effects of turning up the psi on a stock blower, shows all the porting and bits -

http://www.theoldone.com/articles/damaged%2Dblower/

Cheers

J

Rob,

Did you ever sort out the crank pulley?

Minispares do a Poly V conversion kit which includes the crank, water pump and alternator pulleys, but I'm not sure if the belt will be wide enough to handle the power taken by the blower.

I've bought a blower now, so I'm doing the design/planning on this whilst I wait for the bits to finish the 998 Turbo.

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."

I've given this a fair bit of though and I'm probably going to go down the 998 turbo route instead, that way I can have two half build Turbo Minis instead of one!