Tell me about the Eaton M112 Supercharger and using on carbs

[alex]

Hello,

The long term plan is to supercharge my Rover P6 4.6 V8. I am a looooong way off as the engine is in bits again after a head gasket failure, but I like to ponder things

Many newbie questions to follow please excuse my ignorance.

Now, I have an Eaton M112 charger. The plan was to pull through the carb(s) (currently have 2X 2" SUs). So the charger sits in on adaptor plate onto the inlet manifold and then the carbs have another manifold on the charger. This is the first part of conflict - I was up for a considerable amount of time last night trawling the forums and some say that there is absolutely no way the M112 can be used as a draw through due to the seals. Yet on the other hand other sources say no worries, but it does depend on which version of the charger you have - some say the earlier ones are fine. And there are lots of videos about showing the M112 in a draw through setup...so it must be do-able (unless they are all anticipating the seals failing and have accepted that). Can anyone say anything conclusive on this on what versions of the charger will be OK, and how to tell the different versions? Up until now I didn't know there were several types.

The other thing that crops up says that the coating on the rotors needs to be stripped off before it can be used to draw though. Is this really the case? Is the coating not either durable enough to withstand that...or is it that harsh that if it does start to wear off, it will do damage to the charger? If I was to take the coating off unless it is very thin, would that not make the supercharger less efficient as as the rotors would be slightly smaller, and then the gaps bigger? Or am I over thinking that?

This is a mockuop with zip ties etc - the carbs are not mounted to anything! Plus I don't think it would work like this... reckon the carbs would foul the bulk head even without the extra length of the manifold (or whatever term you'd like to sue for it. Perhaps a manifold with an elbows going out to each side...not sure. Perhaps I am over complicating it having two carbs...perhaps I should scrap the idea of a back-fed charger and have one where you can mount the carb on the top (in which case, I'll sell this charger).

[sowen]

Not really answering your questions, but a bit of out-of-the-box thinking for you....

How about running the twin SU's blow-thru? It's a well known and proven MG/Austin/Rover SU carb setup, and the standard HIF44's can be rebuilt with turbo spec parts.

What I'm thinking is that you're planning on fitting the Eaton in the middle on top (so any excuse to justify cutting a hole in the bonnet ), why not use a standard twin SU manifold, space the carbs outwards enough to mount the supercharger between them with the outlet pointing down and the nose/pulley lined up to run off a belt on the front of the crank pulley. From the outlet the air-charge can be ducted either side then directed into both of the carb intakes/plenums. The intake to the charger out the back can be a simple 180 degree elbow to point forwards from above, giving you the classic supercharger scoop, completely functional and bolt on

[alex]

That's a damn bloody good idea Simon and much more practical! It means that I don't have to worry about getting a different (longer) cone so it will be further forward to line up with the pulley - I can pretty much put it where I want (also means handy in the engine bay, plenty of space for the rear of the charger . Means it will actually fit in the bay (well, other than lobbing the top off the bonnet, no problem with that) Also means I can use the standard inlet manifold (or whatever I use in the future). And means I don't have to worry about the coating on the supercharger rotors and not worrying if it's a problem or not to use them as a drag through because it will be a push setup. The charger would have to sit quite high to get some sort of manifold at the bottom of the charger and no idea how I would make that. But it certainly simplifies things considerably.

What I was thinking with push, because I was thinking in my own limited box, is the supercharger off the side of the engine setup, which I did not want in the slightest. Your way is much, much better.

[sowen]

The plenum/manifold on the outlet of the charger would probably only need to be 1.5"-2" deep, as long as it allows the air to flow freely out to each carb the shape shouldn't matter too much. A bypass valve on each side of some description would probably be the biggest challenge. I plan on using a simple mechanically controlled bypass system on my supercharger build, basically another small throttle plate that is open at idle and shut at what.

I really think you should reconsider the HIF44, the parts are available to rebuild them to near turbo spec, main difference is that you won't have the o-ringed dash top (mine started leaking close to 10psi). It could work with the 2" SU's, I've not seen it done but doesn't mean they wouldn't work under pressure?

There you go, no excuses to start bolting the supercharger on

[alex]

No excuse? Hehe yeah other than making a pair of manifolds and figuring everything else out hehe - I am not as skilled as you! However, On searching about, surely there must be an application somewhere where there is an upswept rear port inlet (quite a few of them are top inlets). I was ignoring the bypass valve at the moment as it's.

For the outlet of the charger again here might be something about that can be adapted...but they all seem to be for a single outlet rather than a dual outlet - I need one each side, really. I might experiment making things out of plywood or something.

[alex]

Haaaaaang on a minute. On my old setup (crudely sat on the engine in the pic above) - isn't the charger basically upside down?

If that's the case, why can I not simply use the Jag XKR V8 elbow like this one. In fact, either way round it's supposed to be, can I not use an "off the shelf" part?

[sowen]

If it was me I'd make it all out of something like 2mm steel apart from the flanges which you'd get away with 4-6mm steel and a rubber gasket to take up any warpage, all easily do-able with a basic mig welder setup and hand tools. It would be really trick to get a pair of those alloy outlets and have siamesed outlets, but then again it would be underneath and out of view. I reckon you could knock up a really cool looking air intake similar to that of the original Mad Max Interceptor, simple boxy scoop, filter hidden inside somehow and an elbow at the back to the supercharger. It could be quite a shallow setup, yet still sit nicely proud of the bonnet and not obstruct forward visibility

Or whack a big single turbo on feeding the standard twin SU manifold

[alex]

What is stopping me using the jag outlet as above? If the outlet was underneath, would the charger not be upside down and spinning the wrong way? Wouldn't it make more sense for the outlet to be on-top?

As for spacing the carbs it makes me wonder how much I can space them before it starts to have a detrimental effect.

[alex]

Can anyone identify what generation charger this is?



It has the protruding bearing pins which makes the rear inlet a bit more difficult:

[sowen]

Do you have the Jaguar outlet then? If you have, bolt it on and lay the blower over the engine to see how it could fit

I reckon you could space the carbs a few inches and not notice any difference, bonnet clearance could be an issue, function over form and all that! Make the throttle and choke linkages and fuel lines longer, new throttle control to replace the P6 rod arrangement, I don't see it needing any specialist or highly skilled know-how or tools doing it the way I've described. A pair of Metro turbo plenums or fabricate your own carb plenums (don't bother with any 'restrictor plates', they're a bodge and not how the factory setup runs).

[alex]

Bonnet clearance will be an issue - simple fact it will not clear - the top of the carbs already rub he top of the bonnet very slightly. Angle grinder time! It might be a bit weird looking!

I don't have a choke yet (I hold it open manually for a while at the moment - but I'll address that in the final fitment) and the throttle linkage would simply be extended as I already have it working - it's not standard anyway. No doubt there is enough slack in the fuel lines.

I don't have a Jaguar outlet which is a shame - they are £35 on ebay and it's not the sort of vehicle that appears in the local scrappy. More concerning is which way up the supercharger should go, ideally if it could go the "right" way round - i.e. the outlet to the carbs on the top - that would be ideal. Not sure if the standard setup on the jag reverses the direction from the engine pulley, if you know what I mean.

I read up on things people saying even half an inch on the carb spacer can sacrifice low and mid end performance considerably. There are all sorts of fancy spacers - I am sure if you were trying to squeeze out every horsepower there would be a good reason to figure out what's best, but they come across as gimmickry. I was simply concerned that I could lose a lot of power if I space it too much. I could buy a bunch of H6 spacers (can't find bigger than 1/2"), bore them out by a 1/4" but that's a bit messy I suppose. I can't find off-the-shelf spacers for the H8 so they'd have to be fabricated otherwise.

[alex]

Tell a lie - there is a 1/2" 2" SU Spacer available - part #c33059

www.bighealey.co.uk/austin-healey-parts/fuel-3/under-the-bonnet-1004-large/spacer-carb-to-heatshield-hd8-c33059 although they list it as 1/2" where everyone else lists that part as 1/4".

[sowen]

If you're bolting a supercharger on tuned intake lengths kinda become a secondary concern! The supercharger should sit in any orientation, depends on how it fits each way whether you have the outlet on the top of bottom?

Weird looking? Just watch Mad Max Fury Road then get working on the car!

Best thing to do is grab the blower, lay it in the engine bay and figure out how best it could fit, then start making brackets and plumb it in and test drive it

[alex]

I was thinking if I turn it upside down then it's rotating the wrong way but of course it does't so that's a pretty stupid thing to say! Yep you are right - I'll get the car back together first (head gasket failure) and then start working it out. The pulley is the next thing - I think I have something kicking around that was modified, I'll have to dig it if I can find it - and that will decide where the charger sits, really. Unless someone makes a pulley for the Rover V8. My charger seems to have lost it's pulley looking at the pics, too!

I think outlet on the bottom makes makes it get in the way of other things and was also thinking it would be better a bit further away from the heat of the engine?

You don't have any 2" carb spacers kicking around in your vast array of bits do you?

[sowen]

If I still had a spare carb manifold I could mock something up in the garage if I cleared a bit of space, sold the last of my carb spares a few months back, only got efi kit now. Outlet at the bottom would push the charger up and clear the dizzy (I think you're still living in the stone age running a dizzy?), outlet at the top could work well, then depends which side that big triangular lump sits and how it clears everything?

[alex]

Yep, still in the stone age with a dizzy The carb tower is about the height of the distributor anyway, and would have to clear that, so it'll sit quite high regardless. Triangular lump will probably get in the way of something but will only know when I start mocking it up. *if* I can buy an elbow off-the-shelf no doubt it will point upwards for the standard orientation - that might decide where it goes as it beats trying to make an elbow.

[alex]

If the standard elbow would fit in the bay that would be the easiest thing! Blank off the small hole at the top which I assume is for an EGR. Being designed for the charger so I don't have to stress about getting the design correct. Seems sensible to me.

[Dave Dorson]

My experience of blow vs draw through is limited to air cooled VW's and stuff I've mucked about with for friends, however it translates to the Rover anyway, as it's a 4 stroke engine... usually that draw is fine, if you don't mind driving flat out all the time. you do get flat spots, even with an SU, which is a lovely progressive natured carb, blow through is far nicer, it just feels like you're driving a bigger engine, and it's the reason it gets used for production vehicles everywhere . You want a nice linear power progression, that's why you've gone super over turbo.

I remember having this discussion with Pete when the two of you first made a start on this project.

If you're serious about boosting it, save yourself a whole load of pain and just get the front wheel cut for 36-1, get a megasquirt and figure out a way to go EFi on it, simplify it with a single TB (72mm will flow enough) and have the manifold drilled and tapped for injector placement. I know you wanted to keep it low tech, but you'll only end up disapointed with the results.


Boosting it runs into a whole heap of issues, draw through on that charger isn't ideal anyway, the teflon coated ones you really don't want to go that way with either because you'll end up breaking apart of the coating and it's really nasty stuff to have going through the head and into the bore, basically it'll damage the engine.

If you go down the blow through route, you can just run boost from the charger outlet to the carbs, but you'll need to mount the charger somewhere other than in the valley and run pipework from that, as your carbs will have to sit in the valley on the heads. You can convert SU's to run boost, they used to do it for the metro ones, it's relatively simple.

The second issue you're going to have is retarding your timing for boost.

How does the dizzy advance on the P6?, if it's vacumm you're going to want to change that to a centrafugal advance or find a way to modify the can so it doesn't do funny things when it gets a positive rather than negative signal.

If you insist on keeping it carb, then at least find a way to lock the distributor when it advances, otherwise you're going to melt pistons, if it's centrafugal, you can usually drill and tap the body to add an advance lock which will prevent that.

Don't be tempted to knock the timing back static, because by doing that, you'll have an engine that performs badly off boost, floods with fuel as it's not buring the mixture and you'll see some nasty burps. It'll also be very hard to start.

With regards to fuel supply, if you do boost it and go blow through, depending on your fuel pump, you'll need something to regulate fuel pressure, otherwise the boost will stop the carb from filling with fuel as the floats get pressurised.

You'll want a variable rate FPR that's boost sensitive, the R5 Turbo's used to run carb and blow through and used a malpassi (sp) unit for this that took a reference feed from the inlet manifold.

The the car still running bosh in line pumps with a holley feeding it? , they should be up to the task, but install a swirl pot as well if you haven't already. Last thing you want is to loose fuel mid boost.

[Dave Dorson]

are you sure that outlet on the charger was for an EGR?

I'm pretty sure that because they ran blow through, to stop pressure when the throttle was partially closed, they ran a bypass valve on them similar to the mini with the M45's

If that's the case, you really want something like that installing too, that will prevent you backing air up when the throttles are closed.

I drove an E36 BMW with an M42 that was supercharged, and it drove like the NA car until you booted it, and didn't generate a load of heat, because of that little valve. It's like a secondary TB that bleeds off air when the throttle isn't open.

[mk2cossie]

Jan 18, 2016 11:56:00 GMT Dave Dorson said:

are you sure that outlet on the charger was for an EGR?

I'm pretty sure that because they ran blow through, to stop pressure when the throttle was partially closed, they ran a bypass valve on them similar to the mini with the M45's

If that's the case, you really want something like that installing too, that will prevent you backing air up when the throttles are closed.

I drove an E36 BMW with an M42 that was supercharged, and it drove like the NA car until you booted it, and didn't generate a load of heat, because of that little valve. It's like a secondary TB that bleeds off air when the throttle isn't open.

Yup, that second hole by the throttle plate is the air bypass valve take off.
As above, when on partial throttle or cruising essentially the supercharger isn't as parasitic and improves economy

Also, as the OP has a 4.6 v8 surely he has all the associated efi bits from that engine?