Supercharging theory and practice

Hi guys, used to post here frequently (think i made Dork status) but lost interest after a software change a couple years ago that caused it to take a couple MINUTES to load a thread.

Anyway, you all are a friendly bunch, and i think I need to do some reading..

First, don't send me packing to the CMS board. not sure they'll have information I want. You guys have never been shy about sharing what's in your head, so I'll give a little background. MG made a variant of thre MGB called, oddly enough, an MGC (yeah i know it's more than a variant). Panned by the press, the cars were actually mch better then they were protrayed. They had a 3l inline 6, which weighed a ton, but the actual front/rear balance wasn't bad. The only made a combined total of 8998 cars, so the market for performance parts is a litlle soft. While the B's tend to be a little frantic, the C is a more relaxed car at speed.

And I have one. The latest issue of 'Now C Here', the organ of the North American MGC Registry, had a 2 page article on a guy in Oz who added what looks like an Eation supercharger to an MGC engine. I read the deal, and, as you might expect, not much tech except chassis dyno output and a drag strip run, picture of bracket build on a stand and one installed in the car. So i'm thinkin.... That ain't too tough. i could probably put something together with my stone axe and club toolset.

I need to read up on Eatons or other positive displacement superchargers, sizing, fueling, installation, manifold fabrication, other requirements. Anyboy have a book or two they'd reccomend?

I know that in the Mustang world, the stock Eatons are usually replaced by either Kenne Bells or Whipples.

Welcome back Greg, are you still in Clarkston?

You still have the Toyota? El CaMEANo? (Don't make me go through the entire pole barn inventory ;) )

Still in Clarkston. Toyota was cut up last May and is now part of a Chinese Buick. The drivers door wouldn't latch, and the cost to repair exceeded the value. Fenders wre starting to fall off. Fun while it lasted. Engine and tranny are sitting in the barn- my brother has a R43 Celica in Portland

Current fleet includes 1994 Bronco, 1995 Explorer, 1970 Camaro, 1984 elCamino, 1973 MGB Vintage race car, 1968 MGC, 1976 Capri MkII, 1980 MGB. Guess which three run ;)

Laid off at Valeo in January, supposed to start @ new job on Tuesday. Been a long cold summer

Hey Rev Dex- do you know the reason Ford are using whipple or KB?

They're both twin-screw compressors. More efficient at high boost than an Eaton/Roots, but not as efficient at lower boost levels.

Looking for books? CarTech has a new one called "street supercharging" or something like that. I've been over the equivalent turbo one and it's a good piece of work. Hopefully the supercharger version is as good.

Personally I would also check some MG forums. I'm sure there were others that did something similiar with an MGC. I know there are lots of super/turbo charged B's out there, Moss even has a kit for it. I know different engine but if it can be done I'm sure more than one has done it and willing to share info.
Brit Car forum
MG Enthusiast
MG Experience

Ask on one of these. Believe it or not, lots of MG owners are into modding/upgrading their cars and aren't really keep it original snobs as long as the car is being used and not sitting rusting away.

One basic thing to know is that until very recently Eaton sized its blowers in cubic inches, not CC. Thus they have the M62, M90, M112, etc. The new TVS 1900 may be the first Eaton to change that. I believe the M62 comes on the Cobalt/Cavalier, the M90 was factory on the T-Bird SC and Pontiac GTP and the 112 was standard on the Mustang Cobra/Lightning. They all generate a lot of heat as boost levels increase, so without a bigger intercooler a pulley swap can actually reduce power.

Thanks for the information, Keith. Not sure I'm looking for a book (but I will get them if recommended). What I'm really looking for is information. No one is going to build new stuff for the C, there's just no market, so if i can believe the writup in the C rag, it may be an interesting combination with parts I already have, and others i would want to use. The engine compartment of the C is wider than a B, but it's still crowded.

wlkelly3, i'm invested in MG Enthusiast, MGExperience, and the British V8 forum. While I'm aware of Downton tripple SU conversions, triple 45DCOE stuff, there's not much information on supercharging C's

Greg,

If you really want to supercharge one I would:

• Build a bonnet to pressurize all the carbs at once.

• If using an OE Eaton, remember they are designed to be mounted in a specific plane for oiling. So if you have a TB SC compressor it will have the inlet on the back and the charge tube coming out the top, others may have the inlet in the top and the charge out the bottom. There is a FRPP Explorer M62 that mounted the compressor 90* off plane.

• Eatons like fresh oil often.

• Water injection before the compressor makes a huge difference

Will wrote: One basic thing to know is that until very recently Eaton sized its blowers in cubic inches, not CC. Thus they have the M62, M90, M112, etc. The new TVS 1900 may be the first Eaton to change that. I believe the M62 comes on the Cobalt/Cavalier, the M90 was factory on the T-Bird SC and Pontiac GTP and the 112 was standard on the Mustang Cobra/Lightning. They all generate a lot of heat as boost levels increase, so without a bigger intercooler a pulley swap can actually reduce power.

Technically, there's also an M45... But for this application, it's too small.

I wish I could share my SC sizing presentation with you, but it's proprietary. But for the above blowers, Eaton does have some good information on line- efficency and power curves to pump air at a pressure.

IMHO, a quick and dirty start would be the M62. It will be cheaper than an M90 with all of the GM applications. Not super high boost, but good for an older designed 6 cyl. Once you figure our all of the basics, then you can play with pully sizes and even step up to an M90.

Eric

twentyover wrote: Hey Rev Dex- do you know the reason Ford are using whipple or KB?

Oh, it's not Ford, it's all the guys who buy '03/04 Cobras. They do it because all else being equal, they make more power with the other PD blowers.

Ford's still using Eatons near as I know.

Remember that theory and practice can be quite different. In theory I'm a millionaire...

twentyover wrote: I need to read up on Eatons or other positive displacement superchargers, sizing, fueling, installation, manifold fabrication, other requirements. Anyboy have a book or two they'd reccomend?

twentyover wrote: Thanks for the information, Keith. Not sure I'm looking for a book (but I will get them if recommended). What I'm really looking for is information.

Sorry, I need to work on my reading comprehension

If you're looking for a cookbook on how to add an Eaton SC to an MGC, the only person who can help is probably some guy in Oz. I'd devote a bit of time to tracking him down and seeing if he had any pictures he'd be willing to share. If you have a shot of the engine bay, we can probably figure out what size blower was on there - but with a 3.0 l six making around 200-250 hp, I'm going to say MP62. Taking a look at the Moss Motors MGB supercharger setup will provide some clues on how to deal with manifold design and general concept.

Go to the source .... http://www.eaton.com/EatonCom/ProductsServices/PerformanceProducts/Products/Superchargers/index.htm They show a 'Supercharger Performance Calculator' modeling app that you can download to estimate results with various setups, I have not tried it yet. As a rule of thumb, for a 3.0 L, the M62 should do. Figure the SC RPM as 2x crank RPM. Keep in mind that, unlike a turbo, where the drive energy is vistually free, a SC takes power directly off the crank. So you may run 7 lbs and figure the power goes up ~50%, but you have to subtract the HP to run the SC (plus derate HP due to air charge heating). There are factory maps that will tell you how much HP it takes to create a given amount of boost at a given SC RPM, and the temp rise.

Have fun

Sorry, double post

Thanks everyone for the input. My thinking is that if i supercharge, i should probably go to FI at the same time. i have an old megasquirt in the basement, it was supposed to go on the Toyota.

http://www.californiaclassix.com/images3/c512-engine-remote.jpg shows what the engine compartment looks like

Kieth- i need to work on my writing comprehension. Didn't want to limit it to a book, should have asked for resources, not book. Mind was thinking that, fingers were typing book. Weird synaptic disconnect. my bad.

Not looking for Pederson's kit (rumored but no one has seen it). Figure i could put something together that works for me for les than the $A7000 he wants. He uses his autorotor and lysholm superchargers. No pics on his site. The guy in Oz that wrote the two page ditty used an M90. Don't have scanning capacity to sent the pics he published.

Something else to look at would be V-performance in NY. His main focus is old Volvo's but he's been branching out into LBC's. The s/c kit he sells for Volvo B20's uses a water cooled intercooler in between the s/c and the adapter manifold.

For some reason, I'd wonder of a centrifugal s/c wouldn't work better than a screw type. Put it on the opposite side of the intake; build a custom F.I. intake manifold a la FIS6 (google it...), then run the output of the S/C through an intercooler and into the manifold.

A positive displacement SC yields nearly linear boost vs RPM, centrifugal does not. For a street car, I'd prefer a nice fat torque curve with low end grunt rather than max HP at screaming RPM anyway. You can pick up Eaton's on eBay pretty cheap. What carbs and manifold are used on the MGC? Sidedraft SU or Zenith/Stromberg? You can make a pretty decent custom pressurized carb enclosure out of a cheap pressure cooker from WalMart. If that works, then you can look at getting fancy with MS.

Carter

How do you mount a blower on this car- fab up an intake manifold or what? Do you go with a blow-thru carb?

I generally vote a for a properly designed turbo when it comes to home brewed forced induction, but if you can build an intake manifold, you probably can figure out where to put fuel injector bosses. I think engine management is the deciding factor, as far as boost/ no boost when it comes to projects like this.

Wally wrote: Remember that theory and practice can be quite different. In theory I'm a millionaire...

Yes but in reality we live with a bunch of whores...

later, matt

Here is a supercharger calc sheet that I Came up with. You will have to be running MS active web components for ti work work on your computer. If it does not work follow the link and it sais "web page not found". Then go back a page and the bar on the top will ask to run the active x components. Allow it and you can see the page (it is a spreadsheet)

http://www.ehadesign.com/~dsmith/ENGINE_AIRFLOW.htm

Items in red are variables that you can change.

I believe like most vintage Brit designs, the MGC motor has intake & exhaust on same side. Here's a link to a thread for an Eaton SC on a GT6, a similar configuration

http://www.totallytriumph.net/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=46&forum=DCForumID27&viewmode=threaded

Recall that the Eaton SC has the intake at the rear of the blower body, and discharge on the top/bottom, which can often make the packaging simpler.

The blower sits on the side of the motor without plumbing, feeds into one side of a FMIC, which exits on the plumbing side to feed the intake.

I've seen HIF44 conversions for the MGC motor, recall that the MG Metro Turbo used a blowthru HIF44 from the factory.

A custom manifold could have the SC sitting on it's side, feeding directly into the center of a large log style plenum that runs nearly the length of the block, which would have short individual runners to the head.

Even without MS, I'd still probably go with Megajolt Lite Jr to control the sparks though.

Carter

You don't need FI to run a supercharger - stop by your local drag strip on a Sunday (SUNDAY! SUNDAY!) for proof. I prefer if myself, but it all depends on just how complex you want the final result to be.

If FI is part of the plan, consider installing it first without the supercharger. Figure out the kinks in the system (I doubt there are a lot of Megasquirted MGCs in the world, so you'll be breaking some new ground!) without the distraction of pressurized air.

I'd still start off by examining pics of whatever supercharger systems have been applied to the same or similar engines, that'll give some good ideas or counterexamples for manifold and mounting design. Airflow is easy, but mounting the supercharger and the belt drive capable of transferring 30 or so HP is where things get tricky. I'd strongly recommend using an adjustable tensioner, they make life so much easier.

MGC have both intake and exhaust on the LH side. example laso had the pump mounted on the left, but it was an Ozzie car so no steering shaft. Production cars use 2 HS6 SU's. Moss B kit uses a suck through SU. Thinl pressure bonnets are out, the top of the carb vacuum chanber is perilously lose to the hood.

HIF 44 is the integral float version of the H series carbs. Not familiar w/ the turbo metro, but it was probably a single carb application, probably didn't have hood proximirty issues.

Good thoughts, Kieth, which means I'll probably ignore them :)

twentyover wrote: Still in Clarkston. Toyota was cut up last May and is now part of a Chinese Buick. The drivers door wouldn't latch, and the cost to repair exceeded the value. Fenders wre starting to fall off. Fun while it lasted. Engine and tranny are sitting in the barn- my brother has a R43 Celica in Portland Current fleet includes 1994 Bronco, 1995 Explorer, 1970 Camaro, 1984 elCamino, 1973 MGB Vintage race car, 1968 MGC, 1976 Capri MkII, 1980 MGB. Guess which three run ;) Laid off at Valeo in January, supposed to start @ new job on Tuesday. Been a long cold summer

Wait, which Clarkston? I live in Clarkston, GA. Don't tell me there is an MG hoard within staggering distance of my house?

Sorry, Michign, 15 miles NW of Pontiac

But there is quite a hoard in SC