BMW MINI supercharger on a real mini DIY
Discussion
As I am one of the earliest exponents of a BMW mini supercharger in a blow through configuration, I thought I would post my thoughts here for you lot to peruse. Bearing in mind these blowers are cheap at the moment.
Bini Supercharger Conversion.
Blower.
The blower as fitted to the Bini is an Eaton/Magnuson 4th generation blower. These guys are at the forefront of rootes blower technology and their series 4 is about as good as Rootes blowers get. Sadly that is about 60%(max) Adiabatic Efficiency (Eaton). Comparing poorly to a Screw Blower or Turbo at about 80% (Haynes). Which means when you load it excessively, the unit re-circulates excess air and heats the charge excessively. So, for 12 PSI, the temperature rise is 80 deg C (over ambient). This tails off exponentially and is about 60 at 10, etc, etc. So, the only thing that Bini blowers have got going for them is that they are very cheap. The intake housing is a bad shape and inconveniently large, the unit is gigantic, when placed next to the A Series, it is pretty mind boggling. But for a low boost unit to just augment an engine with already good characteristics, it does it a treat. Which is why the unit figures in low boost applications. It may be practical to use an intercooler to cool the charge slightly, but a boost increase will be non-linear and so the returns don’t justify the means. However, it will allow a higher compression ratio to be used, which will reveal as much power as possible. This looks like being achieved in the biggest possible capacity running as little residual boost as possible, but getting the most air through the intake and out of the car exhaust. This has to be done with particular attention to gas flow, as much as any high performance engine although the characteristics are peculiar to a supercharged engine.
Configurations.
There are only 2 serious options available to the supercharger conversion chap. The Shorrock style “Above the inlet manifold” is the best idea. The easiest to belt up, is probably the best space for it but there is no way in God’s earth (I can see) it would be possible to pipe up for a intercooler (Without a big bonnet bulge). As the engine is a small capacity job (for the blower) and I am trying to get as much out of it as possible, I will consider the alternative. Having it sited at the front, where the alternator would go, but a bit higher up. Before you think otherwise, there is insufficient space (with the pipe work/mounts/oil filter, to mount it with the rotors stacked (ie:- Vertical) so the unit must be mounted “sunny side up” blowing downwards into a fabricated collector. You know if you have it the right place as the unit will foul the slam panel near the bonnet catch, it will be necessary to tip the engine back a tad on special mounts. Once this is achieved, it must be belted up and mounted (which is a lot more tricky than it looks) then it can be piped into a suitable intercooler (Rover TD looks like my favourite choice, although the “Bar and Pipe” design is not the most efficient) then blown through a conventional metro turbo set up. The difference is that a conventional exhaust manifold will be required.
Cam/Head/breathing stuff.
This is where I talk bollocks but it makes sense to me. What is the go for N/A engines, isn’t the same for Turbo engines and again different to supercharged engines.
As the Vizard book says (I had to quote that), increasing the cam duration allows the engine to behave in a form relative to it’s N/A cousins. Whilst this is true and I hear a 276 is great and ultimately a 286 is expected to give great results, I think this is largely bollocks. Whilst it might work the inherent differences must mean that the cam for a N/A engine has insufficient exhaust duration. So, this chokes it up a bit and might sod up the low RPM running. Besides, I’m not investing in a steel bottom end, so I am not going to rev its nuts off anyway. So, the point is at low RPM, the overlap will allow blow by and kill potential power, just as the converse will choke the cam off with not a bit of overlap. Bypassing a load of complicated maths bollocks, about an extra 15deg on the exhaust is a good idea, going to 20 with more wild cams. So, not wanting to go for a special grind, I looked at the Avonbar Ph2 cam, which has the added exhaust duration and lift. (Off the top of my head, it is pretty much a 266 with added exhaust duration of about 15deg).
So, having a look further at the figures for the cam, I see that the exhaust has really high lift, which is a good thing as well. I am now going to go on about the bit of valve choice. Since dP between the inlet and chamber is going to be a lot more than N/A, it follows that the inlet can flow less, as it doesn’t need to, hence less lift, less important inlet valve sizes but the contrary for the exhaust. It will be producing loads of exhaust gas (Try a 2.0 N/A Engine) and so needs big flow. It doesn’t need any more overlap to start interfering with the bottom end, so a bigger valve is more important than a greater rocker ratio.
Roughly, 1.3->1.5 rockers ups area for flow by about 15% more.
Going from a 29mm->32mm exhaust valve adds about 10% more area for flow and acts 10% quicker whilst leaving the overlap untouched. 1.5 rockers increase the significance of the present overlap. Maybe a good idea, but I think not. Obviously, the exhaust system will have to flow for the bigger capacity and I personally would choose a big bore LCB as well as a 2” system.
So, looking at the head. From a load of bollocks and personal hunching, I have decided that 12PSI intercooled, with a 8:1 CR should allow me a sensible margin with 98 RON fuel. That is with a 1380, offset bored, as the extra capacity should release much more useful “work” than an overblown 1293. This appears to be a good move from what I have read elsewhere. Regarding the rev limit of about 6500, it may be possible to gain more power by stroking to 84mm (1430cc) as the lever action should free up a significant amount of torque.
The problem is, how to get the chamber out to the right size. Looking at my casting, and a few others I have, I think that squish matching a head to a piston, with a circular chamber milled out to about 28-30cc, radius being the most important thing. The required gap would then be filled with a matched “Decompression Spacer” gasket, of the required thickness to drop the compression ratio. To 8:1 (I think the area required is about 15cc after 4cc taken off for 2 gaskets). The exhaust ports would be enlarged and the bosses cut back “enough” and the exhaust ports controlled vortex bollocks eliminated and the thing totally matched.
There is very little to read about supercharging an A Series, cam choice, etc. The stuff above is entirely fabricated by me, outlines what I believe to be the right way of getting the most out of the set up. It might make a useful read for someone planning to do a conversion by themselves. However, it is a lot more difficult than it looks. Much more and a kit would be pretty much a good idea.
But, that would be too easy.
Stu
Bini Supercharger Conversion.
Blower.
The blower as fitted to the Bini is an Eaton/Magnuson 4th generation blower. These guys are at the forefront of rootes blower technology and their series 4 is about as good as Rootes blowers get. Sadly that is about 60%(max) Adiabatic Efficiency (Eaton). Comparing poorly to a Screw Blower or Turbo at about 80% (Haynes). Which means when you load it excessively, the unit re-circulates excess air and heats the charge excessively. So, for 12 PSI, the temperature rise is 80 deg C (over ambient). This tails off exponentially and is about 60 at 10, etc, etc. So, the only thing that Bini blowers have got going for them is that they are very cheap. The intake housing is a bad shape and inconveniently large, the unit is gigantic, when placed next to the A Series, it is pretty mind boggling. But for a low boost unit to just augment an engine with already good characteristics, it does it a treat. Which is why the unit figures in low boost applications. It may be practical to use an intercooler to cool the charge slightly, but a boost increase will be non-linear and so the returns don’t justify the means. However, it will allow a higher compression ratio to be used, which will reveal as much power as possible. This looks like being achieved in the biggest possible capacity running as little residual boost as possible, but getting the most air through the intake and out of the car exhaust. This has to be done with particular attention to gas flow, as much as any high performance engine although the characteristics are peculiar to a supercharged engine.
Configurations.
There are only 2 serious options available to the supercharger conversion chap. The Shorrock style “Above the inlet manifold” is the best idea. The easiest to belt up, is probably the best space for it but there is no way in God’s earth (I can see) it would be possible to pipe up for a intercooler (Without a big bonnet bulge). As the engine is a small capacity job (for the blower) and I am trying to get as much out of it as possible, I will consider the alternative. Having it sited at the front, where the alternator would go, but a bit higher up. Before you think otherwise, there is insufficient space (with the pipe work/mounts/oil filter, to mount it with the rotors stacked (ie:- Vertical) so the unit must be mounted “sunny side up” blowing downwards into a fabricated collector. You know if you have it the right place as the unit will foul the slam panel near the bonnet catch, it will be necessary to tip the engine back a tad on special mounts. Once this is achieved, it must be belted up and mounted (which is a lot more tricky than it looks) then it can be piped into a suitable intercooler (Rover TD looks like my favourite choice, although the “Bar and Pipe” design is not the most efficient) then blown through a conventional metro turbo set up. The difference is that a conventional exhaust manifold will be required.
Cam/Head/breathing stuff.
This is where I talk bollocks but it makes sense to me. What is the go for N/A engines, isn’t the same for Turbo engines and again different to supercharged engines.
As the Vizard book says (I had to quote that), increasing the cam duration allows the engine to behave in a form relative to it’s N/A cousins. Whilst this is true and I hear a 276 is great and ultimately a 286 is expected to give great results, I think this is largely bollocks. Whilst it might work the inherent differences must mean that the cam for a N/A engine has insufficient exhaust duration. So, this chokes it up a bit and might sod up the low RPM running. Besides, I’m not investing in a steel bottom end, so I am not going to rev its nuts off anyway. So, the point is at low RPM, the overlap will allow blow by and kill potential power, just as the converse will choke the cam off with not a bit of overlap. Bypassing a load of complicated maths bollocks, about an extra 15deg on the exhaust is a good idea, going to 20 with more wild cams. So, not wanting to go for a special grind, I looked at the Avonbar Ph2 cam, which has the added exhaust duration and lift. (Off the top of my head, it is pretty much a 266 with added exhaust duration of about 15deg).
So, having a look further at the figures for the cam, I see that the exhaust has really high lift, which is a good thing as well. I am now going to go on about the bit of valve choice. Since dP between the inlet and chamber is going to be a lot more than N/A, it follows that the inlet can flow less, as it doesn’t need to, hence less lift, less important inlet valve sizes but the contrary for the exhaust. It will be producing loads of exhaust gas (Try a 2.0 N/A Engine) and so needs big flow. It doesn’t need any more overlap to start interfering with the bottom end, so a bigger valve is more important than a greater rocker ratio.
Roughly, 1.3->1.5 rockers ups area for flow by about 15% more.
Going from a 29mm->32mm exhaust valve adds about 10% more area for flow and acts 10% quicker whilst leaving the overlap untouched. 1.5 rockers increase the significance of the present overlap. Maybe a good idea, but I think not. Obviously, the exhaust system will have to flow for the bigger capacity and I personally would choose a big bore LCB as well as a 2” system.
So, looking at the head. From a load of bollocks and personal hunching, I have decided that 12PSI intercooled, with a 8:1 CR should allow me a sensible margin with 98 RON fuel. That is with a 1380, offset bored, as the extra capacity should release much more useful “work” than an overblown 1293. This appears to be a good move from what I have read elsewhere. Regarding the rev limit of about 6500, it may be possible to gain more power by stroking to 84mm (1430cc) as the lever action should free up a significant amount of torque.
The problem is, how to get the chamber out to the right size. Looking at my casting, and a few others I have, I think that squish matching a head to a piston, with a circular chamber milled out to about 28-30cc, radius being the most important thing. The required gap would then be filled with a matched “Decompression Spacer” gasket, of the required thickness to drop the compression ratio. To 8:1 (I think the area required is about 15cc after 4cc taken off for 2 gaskets). The exhaust ports would be enlarged and the bosses cut back “enough” and the exhaust ports controlled vortex bollocks eliminated and the thing totally matched.
There is very little to read about supercharging an A Series, cam choice, etc. The stuff above is entirely fabricated by me, outlines what I believe to be the right way of getting the most out of the set up. It might make a useful read for someone planning to do a conversion by themselves. However, it is a lot more difficult than it looks. Much more and a kit would be pretty much a good idea.
But, that would be too easy.
Stu
haven't read your post yet - will do later!
this is something I've been wanting to try as I have most of the bits already!
OK, have done a 30 sec read now - couple of comments...
the Works version of the blower is more efficient.
Don't know the exact efficiency of the standard blower, but curves will be available (see Eaton website)
Turbo cam may well not be the correct way to go - you don't need the exhaust pulsation effect that you do to maximise turbo speed.
Vizard's A-series book had acouple of bits about supercharging I thought?
>> Edited by NDT on Friday 7th January 14:31
this is something I've been wanting to try as I have most of the bits already!
OK, have done a 30 sec read now - couple of comments...
the Works version of the blower is more efficient.
Don't know the exact efficiency of the standard blower, but curves will be available (see Eaton website)
Turbo cam may well not be the correct way to go - you don't need the exhaust pulsation effect that you do to maximise turbo speed.
Vizard's A-series book had acouple of bits about supercharging I thought?
>> Edited by NDT on Friday 7th January 14:31
NDT said:
haven't read your post yet - will do later!
this is something I've been wanting to try as I have most of the bits already!
OK, have done a 30 sec read now - couple of comments...
the Works version of the blower is more efficient.
Don't know the exact efficiency of the standard blower, but curves will be available (see Eaton website)
Turbo cam may well not be the correct way to go - you don't need the exhaust pulsation effect that you do to maximise turbo speed.
Vizard's A-series book had acouple of bits about supercharging I thought?
>> Edited by NDT on Friday 7th January 14:31
The deal with the turbo cam is that they open the exhaust valve earlier to get the pulsing. In theory, you could get away with this, I suppose it might enhance your exhaust note a bit. For what it's worth, I think the works blowers cost a bit more than £100 or so.
For the cam, you have to have the exhaust lift and duration as the valves/ports are small even if you do open them out.
Vizards book (and I am very pro-Vizard indeed) goes on and on about using the N/A series of cams which will work a treat, but not as well as ones with a relatively shorter inlet duration. Vizards book has a lot of information about turbos, but comparitively, they are different animals.
Stu
Sounds as if you have had a real challenge on your hands squeezing that lot into a very cramped engine bay. At least I had the luxury of oodles of space, and I needed it all! Distribution seems to be the major issue with blower installations, and assuming you have managed to keep a standard-ish inlet and exhaust geometry I assume this won't cause you too much trouble. Mine is dramatically different to the standard layout and I'm having all sorts of problems as a result. Still, hopefully nothing that can't be sorted out with large amounts of time and money. 
Any chance of some pictures of your installation?
Any chance of some pictures of your installation?
I think getting in to supercharged A-series' is a refreshing idea in the world of ever increasing Honda power (and others).
Things I'm interested in (with very little knowledge of super/turbocharging), about the original post: Firstly how do you arrive at the CR of 8:1 and secondly how do you cope with ignition timing? Or can a standard curve be used?
Personally I'm very tempted to go to VmaxScart with 1600 quid and just buy all the bits. I think they even offer fitting and basic setup for an extra £250. The only problem here is, I'll still never really get my head round how the conversion hangs together, so when it goes wrong I wont know what I can use to fix it! Or how to improve on the setup when funds allow!
Things I'm interested in (with very little knowledge of super/turbocharging), about the original post: Firstly how do you arrive at the CR of 8:1 and secondly how do you cope with ignition timing? Or can a standard curve be used?
Personally I'm very tempted to go to VmaxScart with 1600 quid and just buy all the bits. I think they even offer fitting and basic setup for an extra £250. The only problem here is, I'll still never really get my head round how the conversion hangs together, so when it goes wrong I wont know what I can use to fix it! Or how to improve on the setup when funds allow!
The sprint project has stopped as the blue one (66) blew up on me. I have got to a pretty messy and unimpressive stage with it. This project has completely ground to a halt.
The ignition timing, as the intercooler goes where the dizzy used to be is going to be done via MEGAJOLT cheapo DIY programmable ignition using the gear off a Ford Sierra (Edis). I will set up as a standard Mk1 curve and then RR it and advance it until it pinks.
I have taken it all to bits again without taking any photos. Did a trial fit and now the engine has come out for a rebuild.
I have arrived at the figure of 8:1 CR by reading a massive amount of graphs, looking at what other people have done and having a semi-educated hunch. I will try and top out at about 12 Psi. With the intercooler, that should be totally safe with 8:1 and yield pretty much the best output. Given a bit of time, I could (but probably wont) try different thickness decompression plates.
I suppose that Vmax is on the right boat as the fuel evaporating will slightly cool the charge and cause the rotors to run slightly more sealed, hence a weeny bit more efficient. However, I'm not sure what happens if it backfires. Also, I have heard that someone using a draw through system has experienced condensation being formed on the inlet pipe. This obviously means it is also absorbing more heat.
I will post some photos as and when, allthough the system is infinately more busy than Vmax's effort. But then again, mine will eat his for breakfast
I like the look of Vmax's set up, and from what I have experienced with trying to do it myself, is that his kit is bloody cheap and value for money. I don't agree with his cam choices though.
The 8 port head is on the backburner as well.
Plan is to get the SC 66 on the road for Le Mans, totally finished. Got to mess about with the wiring seriously. My problem is too many things on the go atb once.
The ignition timing, as the intercooler goes where the dizzy used to be is going to be done via MEGAJOLT cheapo DIY programmable ignition using the gear off a Ford Sierra (Edis). I will set up as a standard Mk1 curve and then RR it and advance it until it pinks.
I have taken it all to bits again without taking any photos. Did a trial fit and now the engine has come out for a rebuild.
I have arrived at the figure of 8:1 CR by reading a massive amount of graphs, looking at what other people have done and having a semi-educated hunch. I will try and top out at about 12 Psi. With the intercooler, that should be totally safe with 8:1 and yield pretty much the best output. Given a bit of time, I could (but probably wont) try different thickness decompression plates.
I suppose that Vmax is on the right boat as the fuel evaporating will slightly cool the charge and cause the rotors to run slightly more sealed, hence a weeny bit more efficient. However, I'm not sure what happens if it backfires. Also, I have heard that someone using a draw through system has experienced condensation being formed on the inlet pipe. This obviously means it is also absorbing more heat.
I will post some photos as and when, allthough the system is infinately more busy than Vmax's effort. But then again, mine will eat his for breakfast
I like the look of Vmax's set up, and from what I have experienced with trying to do it myself, is that his kit is bloody cheap and value for money. I don't agree with his cam choices though.
The 8 port head is on the backburner as well.
Plan is to get the SC 66 on the road for Le Mans, totally finished. Got to mess about with the wiring seriously. My problem is too many things on the go atb once.
I think K plate cars just have the same emissions regs as older cars. ie, HC 1200 ppm and CO 3.5%
From memory, that seems to be the limits set on the MOT tests I've had done on cars of that age.
So if you have a working cat it should be WAY under that. If you don't, it's just the same as any old car. (Excluding the reallly old ones which just have to have a visual smoke check and so on!
Oh, and also I think it's the age of the engine which dictates the regulations you have to meet - no idea how you prove the engine age though??
>> Edited by British_Mini on Tuesday 11th January 00:30
From memory, that seems to be the limits set on the MOT tests I've had done on cars of that age.
So if you have a working cat it should be WAY under that. If you don't, it's just the same as any old car. (Excluding the reallly old ones which just have to have a visual smoke check and so on!
Oh, and also I think it's the age of the engine which dictates the regulations you have to meet - no idea how you prove the engine age though??
>> Edited by British_Mini on Tuesday 11th January 00:30
people with MINI supercharged mini's im thinking of building a 998 using the BINI blower what are you views on using a 998 engine and also what are you using for an inlet manifold, love machine?
and i do understand that i could probably just drop in a 1275 and have the same power but its just not the same. what sounds more interesting a 1275 with a stage 1 kit or a supercharged 998!
and i do understand that i could probably just drop in a 1275 and have the same power but its just not the same. what sounds more interesting a 1275 with a stage 1 kit or a supercharged 998!
ccharie
why not knowing much about the mechanics of the late mini supercharger i will stick my opinion in!!!
i think you will need to find a low compression 1000 cc piston that will be able to take the extra stress of what you are trying to do. the good news is that it will be possible - there is a guy called will hamer who hillclimbs a mini 1000 with a metro turbo strapped onto it. i imagine that will h will be running a fairly low compression ratio. he posts a lot on the minifinty site so i guess you will be able to contact him to find out what he has done internally to his motor.
ive driven a 850 supercharge mini (with a old shorrocks huffer fitted) it went really well, about the same as a std 1275. the only downside was the huge cloud of oil smoke that it spewed out on startup if it had been thrashed!! it would easily block all six lanes of a motorway for a mile or so!! very embarrasing!!!
good luck with your project! its nice to see someone doing something differant, not just going down the boring 1380 route!!!
why not knowing much about the mechanics of the late mini supercharger i will stick my opinion in!!!
i think you will need to find a low compression 1000 cc piston that will be able to take the extra stress of what you are trying to do. the good news is that it will be possible - there is a guy called will hamer who hillclimbs a mini 1000 with a metro turbo strapped onto it. i imagine that will h will be running a fairly low compression ratio. he posts a lot on the minifinty site so i guess you will be able to contact him to find out what he has done internally to his motor.
ive driven a 850 supercharge mini (with a old shorrocks huffer fitted) it went really well, about the same as a std 1275. the only downside was the huge cloud of oil smoke that it spewed out on startup if it had been thrashed!! it would easily block all six lanes of a motorway for a mile or so!! very embarrasing!!!
good luck with your project! its nice to see someone doing something differant, not just going down the boring 1380 route!!!
Charlie. It's a difficult one.
If you build it, you will be able to use it on a 1275 as you see fit.
If I was you, (Before I bought the Bini blower) I would see if I could get a Toyota MR2 SC 12 blower (the SC14 is bigger) once again it is a Rootes, they come up on ebay.com from time to time, they are pretty cheap and a lot easier to pipe up. The Bini blower is
enormous and is a tight squeeze. I'm not sure what Vmax use as an inlet manifold but I expect it is highly modified from normal. I am blow through and my blower is where the alternator is, blowing through a metro turbo gubbins.
Piston trouble starts where you make the piston accellerate the most, ie:- High revs. So with a blower engine, you shouldn't be revving it too much. With a head, I think the 12G202 (?) (997 cooper head) had big chambers. I think metro "e"s had low compression pistons as well. With the Bini blower, you are looking at about 12PSI backpressure to start heating things up. That is geared for 12PSI at the rev limit and so will be less up through the range. I wonder if a MG Metro cam would be a good idea, it has the extra exhaust duration which is nice. Stick to 1.3 rockers.
Final drive is worth a look as well. A 3.2 might be a good idea. Forget horsepower, you will be developing a lot of torque. I think a Mk1 dizzy curve is what you are after as well (So, I've heard). Have yet to get mine flashed up. (Run out of bucks).
Any questions, give me a shout.
If you build it, you will be able to use it on a 1275 as you see fit.
If I was you, (Before I bought the Bini blower) I would see if I could get a Toyota MR2 SC 12 blower (the SC14 is bigger) once again it is a Rootes, they come up on ebay.com from time to time, they are pretty cheap and a lot easier to pipe up. The Bini blower is
enormous and is a tight squeeze. I'm not sure what Vmax use as an inlet manifold but I expect it is highly modified from normal. I am blow through and my blower is where the alternator is, blowing through a metro turbo gubbins. Piston trouble starts where you make the piston accellerate the most, ie:- High revs. So with a blower engine, you shouldn't be revving it too much. With a head, I think the 12G202 (?) (997 cooper head) had big chambers. I think metro "e"s had low compression pistons as well. With the Bini blower, you are looking at about 12PSI backpressure to start heating things up. That is geared for 12PSI at the rev limit and so will be less up through the range. I wonder if a MG Metro cam would be a good idea, it has the extra exhaust duration which is nice. Stick to 1.3 rockers.
Final drive is worth a look as well. A 3.2 might be a good idea. Forget horsepower, you will be developing a lot of torque. I think a Mk1 dizzy curve is what you are after as well (So, I've heard). Have yet to get mine flashed up. (Run out of bucks).
Any questions, give me a shout.
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