Using a Cooper S supercharger on something else...
Discussion
I woke up this morning with nothing better to do than go on the net and noticed that there are a fair few standard Eaton chargers for sale (off the Cooper S).
It got me thinking (and before I say any more, I should explain that I am not an engineer by any stretch of the imagination). How easy (or hard) would it be to fit one to a normally aspirated car?
Now the reason I ask is that my wife has got a little Toyota Starlet SR (1300) and absolutely loves the thing. It's in great condition, low miles, never cuased us any issues etc, but she's always whinging that it doesn't have enough power.
So come on. Anyone know whether it would work and what sort of costs are involved (in addition to the charger itself)?
Look forward to hearing back from you.
Rob
It got me thinking (and before I say any more, I should explain that I am not an engineer by any stretch of the imagination). How easy (or hard) would it be to fit one to a normally aspirated car?
Now the reason I ask is that my wife has got a little Toyota Starlet SR (1300) and absolutely loves the thing. It's in great condition, low miles, never cuased us any issues etc, but she's always whinging that it doesn't have enough power.
So come on. Anyone know whether it would work and what sort of costs are involved (in addition to the charger itself)?
Look forward to hearing back from you.
Rob
Well, go for it then - if you can fit it in. The A-series will handle a few psi of boost perfectly well without internal modification. At one point Shorrock superchargers were a straightforward bolt-on tuning mod for the A-series. The Eaton is an example of the less efficient Rootes type, so an intercooler would probably be a good idea.
Shorrocks are both rare and expensive these days because the company ceased to exist in the 70s, which is a shame. They are vane-type superchargers, like the vacuum pumps used to operate the brake servo on diesel cars only the other way round. Since they have internal compression they are more efficient than Rootes-type blowers like the M45; they sap less power from the crank and heat the charge less.
The classic arrangement was simply to bolt a Shorrock C75 onto an A-series, geared to give 5-7psi boost, sucking through the original carb or maybe an HS4, tweak the ignition timing, and go drive it. The charge cooling obtained from the suck-through arrangement plus the efficiency of the Shorrock design and the low level of boost meant there was no need for an intercooler, and the compression ratio was low enough as standard that there was no need to do things to lower the compression ratio that were either unreliable (two head gaskets) or expensive (decompression plate, head machining). If you were doing it to a high-compression A-series you just put the low-compression pistons in.
As well as charge cooling, the suck-through arrangement has the advantage that you don't need to arse around getting the carb to work at pressures above atmospheric, nor do you need a high-pressure fuel pump. You also don't have the problems associated with throttling the output of a positive-displacement blower.
Since the M45 is designed to work with injected engines you'll probably have to change the seals to run suck-through. You'd also want to gear it for a bit less boost to begin with, say 3-4psi, until you've got a handle on the charge temperatures, since it is less efficient than a Shorrock, and work up in stages. If the charge temperatures are too high and you can't avoid detonation you probably do have to bite the bullet and do it the complicated way with blow-through and an intercooler (which will use all the same parts, just other parts as well, so you haven't lost anything).
The other thing is that the exhaust is usually crap on an A-series and it will be helpful to do something about that, especially with the increased flow from a blown engine. The system is too restrictive and the front box is in exactly the wrong place for good midrange torque. On my Morris Minor (which was not supercharged) I had a tubular manifold off a Midget, cut and welded to fit, then a straight tube of the same diameter all the way to the back of the car, where it joined the over-axle and rear box section off a Marina exhaust. This made a very noticeable difference
and it also got rid of that horrible pipe-to-manifold joint that always leaks
The classic arrangement was simply to bolt a Shorrock C75 onto an A-series, geared to give 5-7psi boost, sucking through the original carb or maybe an HS4, tweak the ignition timing, and go drive it. The charge cooling obtained from the suck-through arrangement plus the efficiency of the Shorrock design and the low level of boost meant there was no need for an intercooler, and the compression ratio was low enough as standard that there was no need to do things to lower the compression ratio that were either unreliable (two head gaskets) or expensive (decompression plate, head machining). If you were doing it to a high-compression A-series you just put the low-compression pistons in.
As well as charge cooling, the suck-through arrangement has the advantage that you don't need to arse around getting the carb to work at pressures above atmospheric, nor do you need a high-pressure fuel pump. You also don't have the problems associated with throttling the output of a positive-displacement blower.
Since the M45 is designed to work with injected engines you'll probably have to change the seals to run suck-through. You'd also want to gear it for a bit less boost to begin with, say 3-4psi, until you've got a handle on the charge temperatures, since it is less efficient than a Shorrock, and work up in stages. If the charge temperatures are too high and you can't avoid detonation you probably do have to bite the bullet and do it the complicated way with blow-through and an intercooler (which will use all the same parts, just other parts as well, so you haven't lost anything).
The other thing is that the exhaust is usually crap on an A-series and it will be helpful to do something about that, especially with the increased flow from a blown engine. The system is too restrictive and the front box is in exactly the wrong place for good midrange torque. On my Morris Minor (which was not supercharged) I had a tubular manifold off a Midget, cut and welded to fit, then a straight tube of the same diameter all the way to the back of the car, where it joined the over-axle and rear box section off a Marina exhaust. This made a very noticeable difference
and it also got rid of that horrible pipe-to-manifold joint that always leaks I thought that the inlet cooling on a suck through (condensation sometimes appears on any pipework between blower and carb) was in fact adding thermal energy to the charge! if it's cool, you can guess why it's cool and which direction the heat flow will be in.
For the record, the M45 has 64% adiabatic efficiency at 0.5 Bar. A screw blower or turbo is in the 80% region, although a Shorrock is a true compressor, I doubt it is in the same ballpark efficiency wise as the latter, I would hazard a guess around the 72% mark.
Problem is in order to give a decent boost to a 1275 engine, you have to spin the tits off it, the vanes shit themselves and get sucked into the engine, not good! I can't remember the rev limit of a shorrock but I think it is in the order of 8000rpm. Sure you can get modern tips but it's still a shorrock blower. I'd strap one to a 998cc myself. The M45 will hack 16000rpm which is good for a lot of boost.
There are blower kits for A Series engines and I think out of a 1330 (1275 +60) you are looking in the region of 125hp and 140lb/ft with no intercooler running 98 octane. That's at about 12PSI. I suppose it all depends where on the efficiency curve the blower is operating. I'm using an intercooler as my blower is in a position to use one anyway, a bit less temperature equals a bit more advance/power.
Sorry for the hijack.
For the record, the M45 has 64% adiabatic efficiency at 0.5 Bar. A screw blower or turbo is in the 80% region, although a Shorrock is a true compressor, I doubt it is in the same ballpark efficiency wise as the latter, I would hazard a guess around the 72% mark.
Problem is in order to give a decent boost to a 1275 engine, you have to spin the tits off it, the vanes shit themselves and get sucked into the engine, not good! I can't remember the rev limit of a shorrock but I think it is in the order of 8000rpm. Sure you can get modern tips but it's still a shorrock blower. I'd strap one to a 998cc myself. The M45 will hack 16000rpm which is good for a lot of boost.
There are blower kits for A Series engines and I think out of a 1330 (1275 +60) you are looking in the region of 125hp and 140lb/ft with no intercooler running 98 octane. That's at about 12PSI. I suppose it all depends where on the efficiency curve the blower is operating. I'm using an intercooler as my blower is in a position to use one anyway, a bit less temperature equals a bit more advance/power.
Sorry for the hijack.
love machine said:
I thought that the inlet cooling on a suck through ... was in fact adding thermal energy to the charge! if it's cool, you can guess why it's cool and which direction the heat flow will be in.
That's true, it will mean that heat conducts in through the metalwork. t may still mean it runs cooler overall though, because by dropping the pressure downstream of the blower it reduces the heat that the blower puts into the charge.
There's a vicous spiral where more back pressure makes the blower work harder, which heats the charge, which increases the back pressure, which puts the blower into a less efficient operating area, which heats the charge even more etc. My theory is this is why supercharged installations had such a reputation for blowing engines up - as soon as you start running into the breathing limitations of the base engine, the heat and back pressure climb catastrophically.
jimmyfish said:
Why not get a starlet turbo
We did talk to Fensport at one point about that, but I'm a glutten for punishment, and love a challenge.
I have a contact who creates bespoke mounts, tubing etc so the actual fitting I don't suppose would be a massive issue. There's tons of room left over in the engine bay as standard.
The thing that concerned me was my simplistic (and often stupid) view on engineering. I just saw a supercharger for £50 (or so) and like a kid in a toy factory, got all excited.
I didn't even consider the engine compression for instance, hence why I suppose there are so many of these chargers around, and not many people who have succesfully done home grown conversions on their "normal" cars.
Anyway, from what I can tell, to do the conversion properly is going to take a fair bit more than the wife would entertain. I was just hoping it would be a bolt on conversion (with a piggy back ECU).
In this case, it appears that an engine conversion would probably be the best bet for more (reliable) power. Or just a new car...
Doesn't stop me contemplating mad ideas though...
Thanks for the input!!
Rob
The whole thermal runaway thing intrigues me. As the thing is in bits at the moment, I have no way of testing how the behaviour would work at higher boosts. My approach is having a long enough cam for the job, both exhaust and inlet. A 264/278 with super monster exhaust lift. The idea being to maximise flow whilst keeping the overlap down.
Just off to read about thermal runaway.....
Just off to read about thermal runaway.....
love machine said:
Just off to read about thermal runaway.....
I haven't done it yet, but I'm wondering about fitting a blow-off valve just to act as a 'safety valve' to stop the back pressure and temperature going through the roof if thermal runaway does occur. In theory, that should be able to stop thermal runaway in its tracks. I've got the recirc valve and I guess I could just add a second actuator, but a separate BoV might be easier to sort.
>> Edited by GreenV8S on Sunday 7th August 14:07
I've got a funny feeling that on the overrun, there is a massive pressure difference across the butterfly and the boost can climb considerably that way. I'm not sure about that, turbo cars use dump valves. It would be interesting to see what happened pressure wise on the overrun. I imagine my new boost guage will go off the scale!
That is not something I would be happy to allow to happen... I'd be worried about things like damaged blowers, exploding intercoolers... perhaps bent throttle butterflies so you suddenly take off, depending on what gives first...
As you say, turbos control this with dump valves... but there is also the point that under steady-speed cruising conditions at speeds that would have been comfortably achieved by the unmodified car, ie. any speed you wouldn't mind meeting the police at, the intake will be significantly throttled and have a pressure below atmospheric; boost is not required. With a turbo you can reduce the boost by reducing the power input to the compressor with a wastegate - the dump valve is only required under transient conditions due to the rotational energy of the turbo. With a supercharger you can't do this unless you have some sort of CVT drive to the supercharger, and controlling excess boost with a dump valve would result in large amounts of power being wasted.
However, since we are talking about a blower without internal compression, its power consumption can be minimised by unloading it - a large diameter bypass around the blower with a butterfly valve in it to close it off when boost is required. It might be a bit tricky to devise a control law for this valve that would give a smooth transition from off- to on-boost without surges or flat spots, or oscillations if you're trying to cruise in the transition region Another option would be to throttle the input of the blower - either so as to keep the pressure after the blower equal to atmospheric when boost is not required, which wastes power and brings in the same control difficulties, or in accordance with the airflow requirements of the engine and the power demand, which would subject the carb to negative static pressures so you'd have to go to injection.
A blow-off valve is still a worthwhile addition, both to guard against thermal runaway and to guard against damage to the blower in the event of a backfire - for a suck-through system, change "worthwhile" to "essential"
(Shorrocks and the A-series... yes, a C75 is a bit small for a 1275, but a C142 is OK... just even rarer and more expensive )
As you say, turbos control this with dump valves... but there is also the point that under steady-speed cruising conditions at speeds that would have been comfortably achieved by the unmodified car, ie. any speed you wouldn't mind meeting the police at
, the intake will be significantly throttled and have a pressure below atmospheric; boost is not required. With a turbo you can reduce the boost by reducing the power input to the compressor with a wastegate - the dump valve is only required under transient conditions due to the rotational energy of the turbo. With a supercharger you can't do this unless you have some sort of CVT drive to the supercharger, and controlling excess boost with a dump valve would result in large amounts of power being wasted. However, since we are talking about a blower without internal compression, its power consumption can be minimised by unloading it - a large diameter bypass around the blower with a butterfly valve in it to close it off when boost is required. It might be a bit tricky to devise a control law for this valve that would give a smooth transition from off- to on-boost without surges or flat spots, or oscillations if you're trying to cruise in the transition region
Another option would be to throttle the input of the blower - either so as to keep the pressure after the blower equal to atmospheric when boost is not required, which wastes power and brings in the same control difficulties, or in accordance with the airflow requirements of the engine and the power demand, which would subject the carb to negative static pressures so you'd have to go to injection. A blow-off valve is still a worthwhile addition, both to guard against thermal runaway and to guard against damage to the blower in the event of a backfire - for a suck-through system, change "worthwhile" to "essential"
(Shorrocks and the A-series... yes, a C75 is a bit small for a 1275, but a C142 is OK... just even rarer and more expensive
) I wanted to fir a supercharger to a VVC.
The main problem was the cost of making a new inlet manifold.
Turbo Technic is charging nearly £10k for a fitted supercharger kit on a vvc
I'll be probably going the direct to head throttle body routes with a new MEM (emerald.
Unless someone as some more info about supercharging VVC.
Jack
The main problem was the cost of making a new inlet manifold.
Turbo Technic is charging nearly £10k for a fitted supercharger kit on a vvc
I'll be probably going the direct to head throttle body routes with a new MEM (emerald.
Unless someone as some more info about supercharging VVC.
Jack
Pigeon said:
A blow-off valve is still a worthwhile addition, both to guard against thermal runaway and to guard against damage to the blower in the event of a backfire
I don't have a BoV (yet), and even with port injection there have been several occasions where it has backfired sufficiently to stall the blower (you can hear it stop and then spin up again, no the poly-V doesn't much like it when this happens!).
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