Good reading guys.

I'll throw my hat into the ring.

I have been playing on and off with the Chrysler 2.2 based turbo cars since `89. I have LOTS of turbo experience, but I have never had a blower car.

Turbos are fun and make really cool noises. Blowers also make their own noises and I'm sure are just as fun.

A long time ago I did a lot of reading about boosted engines vs. naturally aspirated engines. You can theoritically get the same horsepower output from each. But the difference is what is called the area under the curve. Boosted engines start producing more horsepower sooner and keep it going longer in the rev range than a naturally aspirated engine can. And usually to get a naturally aspirated engine to match to exceed the peak horsepower of a boosted engine, you end up with a poorly streetable and very peaky engine.

Also, to give a little light on the technical supercharger terms...

A mechanical supercharger is driven via a mechanical means from the engine and is typically just referred to as a supercharger or blower. Although, technically a blower, like on the Detroit Diesels, really isn't there to pressurize the intake system, it's just to 'blow' freash air into the intake ports since there wasn't enough natural vacuum.

A turbosupercharger is indirectly driven using exhaust gases from the engine and is usually just shortened to turbocharger or turbo.

As for those concerned about lag from turbos, Carroll Shebly said "if you have lag, you're not driving it right!"

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Thomas Mann
Jacksonville, FL

Hi,

The Shorrocks are valued as they were homologated for FIA competition, see FIA Recognition #87. I've been chasing one for years, so if someone is interested in letting one go..............

KG

Carroll Shelby must have never driven a Toyota Supra with a 90mm turbo. They make peak boost at no less than 5500 rpm, but when they do it's sideways.

Carol shelby never encountered the tired mercedes 300D I test drove a few years back for a friend interested in buying it. You had to stand on the throttle and brake for a good 30 seconds just to get enough power to pull away from a stoplight as fast as naturaly aspirated newer and smaller cars with half this merc's engines displacement.

The current Mini Coopers provide a good comparison of blown versus turbo'd. The S versions were supercharged for a couple of years and then were reconfigured for turbochargers. The turbo engines are more efficient (better gas mileage) with roughly the same performance. Some folks like the sound of the earlier, blown cars.

My 2008 Clubman S (turbo) has no throttle lag that I can detect. With a 6-speed automatic in sport mode, it pulls like the dickens from a standstill.

The old school superchargers are like hairdriers compared to the modern stuff that is more akin to a leaf blower. I suspect lifespan of the device is going to be much better also due to materials and machining technology.

Fuel injection would be great for these cars however, a proper kit would be as expensive and the supercharger, and not everyone can build/tune their own design to work up to potential.

A WEBER DCOE does not add any power to an engine. No carburator does. All any carb can do is mix air and fuel according to the vacuum signall from the engine and the program entered by the person who tuned it.

Maybe not, but twin DOCE carbs on a 7 port head sure do look purdy.

Your carb should be matched to the air flow of the engine. The stock carbs should do fine for most people as the factory usually does a pretty good job matching parts. When you modify the engine adding compression or improving flow through the system you may benefit from a larger CFM carburetor. The muscle car guys have a tendency to over-carb their engines leading to low velocity through the venturi and poor fuel atomization. Carbs are a PITA to set up for forced induction. Most engines with boost like a dynamic fuel curve to prevent heat and detonation. Carbs are less than dynamic under pressure. They tend to run one curve and jump all over the place with heat changes. Ultimately fuel injection with an adjustable ECU and electronic ignition are best with boost and prolong engine life significantly. IMHO superchargers are easier to install depending on application and design. They provide good power and are easy to maintain. They do create a parasitic power loss due to the drive belt, and are power limited by the pulley and internal gear ratios. Turbochargers are generally more difficult to install as they need piping for the intake and charge air as well as exhaust inlet and outlet. Not to mention the oil and water cooling hoses. They also require a wastegate valve and bypass valve. Turbochargers also generally expose the engine bay to increased heat due to the exhaust routing and the turbine housing locations. Turbochargers however are "free" power and require no mechanical drive. They are also adjustable for "on the fly" boost changes. When I do the ECU's on the TT Vipers I do a map that is temperature and pressure corrected as well as o2 feedback. I can set up a variable boost control setup that does boost by gear or speed. Traction control, launch control (anti-lag), and knock control that pulls timing adds fuel and can reduce boost if the engine begins to ping. With all the controls in place they achieve over 1100 hp and drive like stock with cruise mpg's up generally 10% over the OEM setup.

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My fuel injected MG Midget Project
Sorry folks, I do not battle the keyboard warriors, or feed the trolls!

I'm not sure how you can compare a DCOE to an SU, or worse? The power range of a DCOE is roughly 2500-7000 if properly sized and set up. An SU craps out at 6000. The big difference is low rpm velocity - the DCOE is designed to have correct velocity at race speeds - 3-8K At low speeds, velocity is too low to accurately meter fuel, especially considering its using 3 separate circuits at low speed which makes tuning them very confusing for most people. SUs generally perform better on street cars because anyone can tune them, and the variable venturi design makes them virtually "one-size-fits-all." Overall the DCOE will make the most power, second only to a properly tuned EFI system.

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jeff@advanceddistributors.com

Jeff
Not really meaning to take issue with you but that is a little contrary to my understanding. That being, an SU would "crap" out at its wide open venturi. The size and number of SU would in my estimation, allow one to peak at 7500 or 8K if that was feasible. My further understanding is the preference for Weber in the EU and for UK works engines was for chasing roads up and down the Alps where tremendous atmospheric pressure differentials would give Weber a slight advantage over a sliding venturi carb such as SU. On the other hand, and my point of inquiry, I know of few LBC better, winning, race engine that opt to SU over Weber

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Regards,
Robert Kirk
kirkbrit@yahoo.com
563 323 1017
Moss distributor UK importer
Beat or match any retail/delivered quote



Edited 1 time(s). Last edit at 02/25/2012 12:04PM by kirks-auto.

Hmmmm.

What about all those BMC works cars that WON countless international events using those pesky SU's.
Must have missed something Homologation rules aside, they clearly did the job well.

Not a fan of Weber's, that is well known, at least for road use. Racing, different story...........perhaps.

But, since this is a "supercharger" thread, the point is perhaps "moot".

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Andy

The Shorrock supercharger is very inefficient compared to modern superchargers, but work reasonably well for a mild power boost on smaller displacement engines. The Shorrock setup for spridget is really too small to be very effective on a 1275. It will heat the intake air more and require more power to drive it than a modern supercharger (such as the moss kit). The moss kit uses an Eaton blower, fundamentally the same as fitted to new Minis and several other cars (but with a different casing), and a homemade set of manifolds can be built to accomodate these superchargers (very common on classic minis in the UK). The moss kits are very effective, and I have seen a few engines (heavily built specifically for the supercharger and using higher boost pulleys, but street engines) using the moss setup make around the 140-150bhp mark.

There are lots of other superchargers that can be made to fit if you fabricate the mounts and manifolds, I personally am using a Toyota SC14 supercharger, but this is a bit large (I need to have some different pulleys made up to reduce supercharger speed, as when I first installed it it produced 25psi of boost at 2000rpm). I am shooting for fairly high power though, so wanted the capacity, and therefore potential, of the larger blower. There is a smaller Toyota supercharger, the SC12, that has been used with great success on a lot of 1275 minis here in Australia. You can also buy a kit from Hi Flow (http://www.hi-flow.com/) which uses a twin screw supercharger, which is more efficient again than the roots Eaton blowers. However, in the Hi Flow kit that I have seen, the supercharger was a bit undersized for big power (it is after all designed for a standard engine), and topped out at about 130bhp on my engine builders engine dyno. I should note that I was told when I enquired some time back that they were developing a kit with a larger supercharger for high power applications.

Virtually all these setups use a suck through HIF44 or similar - an 1 3/4" SU - that I think is ultimately the cap for power from these setups. I have constructed my setup to use a HIF44 also, but if (as I expect) it proves to be a restriction I will remake the manifold to take my 45DCOE (currently fitted to the car minus supercharger, due to the issue with excessive boost).

On another note, I have to say I disagree with some of what Robert Kirk has written regarding fuel injection. Fuel injection in and of itself does not necessarily result in more power, and is difficult to get accurate fueling from on our siamese port heads (though it can be done). Fuel injection is used in modern cars mostly for 2 reasons - economy, and emissions. You can get more accurate fueling under a wide range of driving conditions from efi, but a properly setup carby system will produce just as much power at wide open throttle, in fact there have been a couple of studies showing carbs (highly optimised setups of course) producing slightly better power at WOT than equivalent fuel injection setups due to better fuel atomisation. Fuel injection may give a more driveable (though a lot of that is in the electronic mapping of spark, rather than fuel) and economical car, but it won't necessarily make any more power, whereas that is the entire point of a supercharger. Weber DCOEs and IDAs have long been a premium performance carburettor, and they work extremely well when properly setup (but finding the right person to do that can admittedly be difficult). I do agree with Robert though that other, cheaper Weber carbs are just that - cheap carbs, designed to replace standard setups, not designed for performance. I also agree that fuel injection is better than a restrictive carb setup (which many standard setups are, twin SUs are pretty good though).

Oops, posted the above before reading page 2 and 3! Oh well, still mostly relevant.

It would be of interest to see some of the handmade manifolds designed for Eaton and other modern superchargers. Is there any chance that somewhere in the UK such manifold are fabricated and a few copies sold by a an individual?
Does the company you mention sell manifolds separately? I could not find that on their website but itcwas good to see some application to MGA, MGB. Migits , and minis all on one dite.

My point about EFI vs 1970 natural aspiration is more to do with the management system than the specific method of atomization. With a computer monitoring the system by default, there is better overall management and thus more power. Modern vehicles have completely done away with a distributor for instance...crank sensor now used in many instances. That is just one of the benefits.

What some seem to miss is the other technical developments that have come down the pike since Shorrock, Paxton, Prewar MG, Bentley etc. In their day they were state of the art or near so. This thread seems to question the value of modern tech vs two score year old tech. The extra value is the gain in the R&D which has elevated the tech. That is not to say old tech is bad or poor tech, it is just old, dated and less than what is currently available.

I've got no dog in the fight whatsoever, but the level of "refurbishing" a dated SC certainly is key to another point of value. Metal fatigues. RPMs the like of superchargers would certainly bring into question the viability of a used unit. FWIW and IMHO.

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Regards,
Robert Kirk
kirkbrit@yahoo.com
563 323 1017
Moss distributor UK importer
Beat or match any retail/delivered quote

Fair enough Robert, there is certainly a lot of value in electronically controlled ignition, and some gain to be made from fuel injection (with the right setup). It may add a lot of part throttle driveability, improved economy, and maybe a little power in certain areas. My point though was that whereas a supercharger is a power adding modification, fuel injection will not add much power, and may even reduce power if it's a poor configuration or if not set up correctly (just as with a carb setup).

I'm certainly not suggesting that carburettors are better than fuel injection, a well thought out and properly mapped fuel injection setup will be better - particularly for fuel economy, and to a lesser extent part throttle driveability. But if it makes a big outright power difference, then the carb was wrong for the task or not properly setup. I am not adverse to modern tech at all, my other toy is a 70s Mazda fitted with a rotary engine, turbo, and aftermarket fuel injection. But on the other hand, carbs are still capable of a lot, particularly if power is the main objective and fuel economy is less important. They are generally much cheaper also. I guess I feel that for someone asking about supercharging for more power, fuel injection is not a relevant alternative (unless combined with a heavily built, preferably cross flow, engine). It is certainly worth considering in combination with the supercharger though, if the owner is interested in going in that direction.

Gerry - No, I don't believe Hi Flow sell the manifolds seperately. The price of the kit when I enquired was eye watering too... You can find a fair number of home fabricated manifolds if you do some google searching or look on UK or AUS classic mini forums.

Attached are some pictures of my manifolds using the Toyota SC14 supercharger (which is a fair bit larger) when I was doing the final mockup before rebuilding the car. They are made from steel, ceramic coated. You can see a pressure relief valve (to avoid a backfire damaging the blower) and a takeoff for boost reference on the plenum between the supercharger and head. The threaded hole on the intake side of the supercharger is for a water injector, which will inject water/meth under boost to control intake temps and pinging (I am intending to run ~15-16psi of boost). The important thing with making the manifolds is to avoid making the air/fuel mixture travel uphill, or through many tight turns, as these things will result in fuel pooling in the inlet, causing rough running and making it hard to tune. Some aftermarket setups I have seen sold for various cars haven't been very good at these basics... You can see there is a tensioner pulley for the belt mounted to the front of the plenum. Unlike the Moss setup, my setup uses the standard belt to run the alternator and water pump, and a seperate belt to turn the blower. Any other questions feel free to ask! The setup clears the bonnet, guard, and inner guard without modification. It would have been a much easier (less tight) fit if I hadn't wanted to use a set of race extractors (designed for use with a Weber manifold, don't fit with SUs) that have a much longer straight shot out of the head before curving downwards.

Cheers,

Andrew.

The superchargers must need support in addition to the intake manifold bolts! Andrew, have you fabricated a bracket or brace under the SC attached to the block?

I like the idea of separate belts rather than a serpantine belt, also the backfire relief valve is brilliant.

Yes, you're right, there is an additional brace from the bottom of the supercharger to the back of the front plate of the engine, I'm pretty sure it's not fitted in the photos, but you'd struggle to see it anyway. As you can see it was just a mockup fitting, a number of bolts aren't fitted also. The supercharger has similar lugs on the bottom to those you see on the top, and uses a long bolt through a tube between them with a flat piece of plate going downwards that pics up 2 of the bolts on the front engine plate. Having said that, I have seen a number of home made setups with no additional bracing, where the supercharger and carb mounted closer to the head which results in less problems with the weight as it is not cantilevered so far off the head. I still think it advisable to have an additional brace though. Mine is further from the head for 2 reasons - to clear the race extractors, while still being low enough to clear the bonnet. I did not want to have a bonnet bulge. Classic minis have enough bonnet clearance to allow the plenum and supercharger to be mounted above the exhaust, but such a setup would most likely have required a bonnet bulge on my Midget to clear it.

The tensioner pulley by the way is adjusted from a bolt underneath the manifold, it travels up and down in the rectangular piece you see behind it welded to the front of the plenum.

Do you still have the M45? I am aware that these exist in many configurations, most commonly it seeks for the Mini. If you still have the item, I'm interested, would have have a photo of your unit?

sorry, sold long ago. Look on ebay -