Metro Turbo Engines
Discussion
Hello guys, I'm looking at using one of these engines for an engine swap for my 1500 midget, so I thought this might be a good place to ask for info on the engine.....
As I understand it they run 93bhp as standard, how tunable are they though? I'm looking for around 110 - 120ish bhp to start with. Due to the lack of space to put an intercooler in the midgets engine bay I was considering water injection having played about with it on Turbo MR2's with reasonable success. Any info about these engines would be appreciated.
Am I right in saying its an A+ with a T3 'bolted on'? Are the internals standard etc? Also, does anyone know what torque they produce?
As I understand it they run 93bhp as standard, how tunable are they though? I'm looking for around 110 - 120ish bhp to start with. Due to the lack of space to put an intercooler in the midgets engine bay I was considering water injection having played about with it on Turbo MR2's with reasonable success. Any info about these engines would be appreciated.
Am I right in saying its an A+ with a T3 'bolted on'? Are the internals standard etc? Also, does anyone know what torque they produce?
93bhp is correct for the standard engine. They are fairly tuneable, but raising the boost on a stock engine isn't really feasable as the very high CR (9.3:1) will cause detonation very quickly. In fact the standard engine uses boost control to limit boost to just 4PSI until around 4500 rpm where you get the full 7PSI. This was allegedly to prevent blowing up gearboxes with the huge amount of torque (for an A-series
). However, IME you will get detonation on a stock engine by defeating the boost control and running just 7PSI all the time.
A popular mod is a set of metro van pistons which give aproximately 8.8:1 CR and a bit of grinding on the chambers to de-shroud the valves etc. will lower this further. The cranks were supposed to be nitrided, but it seems like plenty of them aren't. The bottom end is reasonably strong, but a set of uprated big end bolts and strapping the center main bearing would be advisable.
The cam is very mild, the same grind used on a stock 1275 I think, and the engine will respond to a slightly hotter cam such as the MG Metro unit, or there are some specialist cams around designed for the turbo.
In stock form the engine delivered around 85ftlbs (at 4000RPM), but upping the boost (with the other mods) will significantly increase this. If you are thinking of using the stock gearbox then you are probably going to get plenty of practice changing/rebuilding it.
Paul Whiffin had a monster turbo'd A series producing 175bhp/200ftlb in a mini. Have a look at www.whifbitz.co.uk/feature.htm
How to turbocharge your Midget www.turbomidget.connectfree.co.uk/turbo.htm
). However, IME you will get detonation on a stock engine by defeating the boost control and running just 7PSI all the time. A popular mod is a set of metro van pistons which give aproximately 8.8:1 CR and a bit of grinding on the chambers to de-shroud the valves etc. will lower this further. The cranks were supposed to be nitrided, but it seems like plenty of them aren't. The bottom end is reasonably strong, but a set of uprated big end bolts and strapping the center main bearing would be advisable.
The cam is very mild, the same grind used on a stock 1275 I think, and the engine will respond to a slightly hotter cam such as the MG Metro unit, or there are some specialist cams around designed for the turbo.
In stock form the engine delivered around 85ftlbs (at 4000RPM), but upping the boost (with the other mods) will significantly increase this. If you are thinking of using the stock gearbox then you are probably going to get plenty of practice changing/rebuilding it.
Paul Whiffin had a monster turbo'd A series producing 175bhp/200ftlb in a mini. Have a look at www.whifbitz.co.uk/feature.htm
How to turbocharge your Midget www.turbomidget.connectfree.co.uk/turbo.htm
Thanks Mike, Some usefull information there, I wasn't aware it limited boost to 4psi until 4.5K. However, it looks like it doesn't use an intercooler as standard so that might well account, at least in part, for the detonation problems. In intercooler + water injection would most likely cure that one. (hopefully)
BTW, just seen your car in your profile, v. nice, just like my old GTS. Great cars.
BTW, just seen your car in your profile, v. nice, just like my old GTS. Great cars.
neilr said:
Thanks Mike, Some usefull information there, I wasn't aware it limited boost to 4psi until 4.5K. However, it looks like it doesn't use an intercooler as standard so that might well account, at least in part, for the detonation problems. In intercooler + water injection would most likely cure that one. (hopefully)
Correct, no intercooler. I suspect an intercooler + water injection would certainly help a great deal.
said:
BTW, just seen your car in your profile, v. nice, just like my old GTS. Great cars.
Much fun when it's running! Blew a head gasket a couple of weeks ago and I've been slowly rebuilding it, mainly waiting for parts from Toyota or recovering from shock at the prices: How about £45 for one exhaust valve? Must get another mini after I have finished building the Locost
>> Edited by Mr2Mike on Tuesday 15th July 22:47
The 'boost control', is actually not below the 4.5krpm it's above, the actuator on the turbo is 4-5psi, the ecu, uses a bleed valve to 'confuse' the actuator into thinking the boost is lower and so allowing more boost upto the 7 psi.
van pistons are a good cheap mod, but forged ones are much better.
You'll also need to change the dump valve spring in the plenum, or fit an adjustable one (but a modified plenum is required, not cheap!).
get the block chemically cleaned, there are oil sprays under the pistons which squirt oil onto them to aid cooling, these can become blocked and cause pinking.
my 2peneth
van pistons are a good cheap mod, but forged ones are much better.
You'll also need to change the dump valve spring in the plenum, or fit an adjustable one (but a modified plenum is required, not cheap!).
get the block chemically cleaned, there are oil sprays under the pistons which squirt oil onto them to aid cooling, these can become blocked and cause pinking.
my 2peneth
Water injection has always interested me. Does anyone know of a kit you can buy. We used to use water injection on jet engines for military applications to get max boost for take-off. It's a long time ago, but IIRC the idea was to inject a fine spray of water into the air intakes just before the first compressor stage, thus giving the effect of increasing the density of the air.
I sort-of looked at designing a system a few years ago, but the problem seemed to be to link the volume of water delivered to the throttle setting and engine load. I suppose you need to link it to the vacuum setting and revs. i.e. the lower the vacuum in the manifold and the higher the revs the more water should be delivered into the manifold as a fine spray.
If anyone can provide more information on this I should be very grateful.
I sort-of looked at designing a system a few years ago, but the problem seemed to be to link the volume of water delivered to the throttle setting and engine load. I suppose you need to link it to the vacuum setting and revs. i.e. the lower the vacuum in the manifold and the higher the revs the more water should be delivered into the manifold as a fine spray.
If anyone can provide more information on this I should be very grateful.
What you say is basically right, a fine mist is injected into the intake but after the Intercooler (if there is one) and usually before the actual manifold.
Basically works (usually)on a pressure sensor that triggers the spray above a certain psi/bar and away you go (although I'm pretty sure that if the engine uses a MAP sensor rather than an AFM then you can use the pressure inputs from the ECU to activate it).
I think some Imprezas had WI sprays that were attached directly to the intake manifold, (presumably for maximum affect) but i ca't be certain. If your running high (read above OEM) boost then it's highly affective, especially at stopping detonation. Methanol (i think) is sometimes added to prevent the water freezing in winter and has the added benefit of a psuedo octane increase. Aquamist (among others) make various kits to suit various wallets....
Basically works (usually)on a pressure sensor that triggers the spray above a certain psi/bar and away you go (although I'm pretty sure that if the engine uses a MAP sensor rather than an AFM then you can use the pressure inputs from the ECU to activate it).
I think some Imprezas had WI sprays that were attached directly to the intake manifold, (presumably for maximum affect) but i ca't be certain. If your running high (read above OEM) boost then it's highly affective, especially at stopping detonation. Methanol (i think) is sometimes added to prevent the water freezing in winter and has the added benefit of a psuedo octane increase. Aquamist (among others) make various kits to suit various wallets....
you'll need a boost pressure and air temperature sensor, also feeding the coolant temperature signal into a controller will be uselful. (it is possible to do with analogue electronics).
It's possible to use a fuel injector, same thing works for nitrous! or methanol as was mentioned
you just alter the pulse duration based upon those three variables, relatively simple.
It's possible to use a fuel injector, same thing works for nitrous! or methanol as was mentioned
you just alter the pulse duration based upon those three variables, relatively simple.
I was thinking of an applicaton with a twin-carb Cooper 'S' without the requisite black-box, turbo controller or intercooler. If I was allowed to run on events with an intercooled Turbo I don't think I'd need water injecton as I could easily break the transmission without! Thinking about it, I break it anyway without either.
Seriously, I think the problem with the very high torques you could obtain with a turbo-intercooled water-injected unit might be more than the standard drive shafts could take. There are some very expensive shafts (i.e. about £65 each) made from EN24B which delete the weak point. The weak point is the circlip groove where the shaft enters the splined bore of the CV joint. In engineering terms it's 'a rapid change of cross sectional area at a point of high stress loading'. In normal terms, it bloody well snaps off at this end! Since I paid my money I have had no further failures, touchwood.
Seriously, I think the problem with the very high torques you could obtain with a turbo-intercooled water-injected unit might be more than the standard drive shafts could take. There are some very expensive shafts (i.e. about £65 each) made from EN24B which delete the weak point. The weak point is the circlip groove where the shaft enters the splined bore of the CV joint. In engineering terms it's 'a rapid change of cross sectional area at a point of high stress loading'. In normal terms, it bloody well snaps off at this end! Since I paid my money I have had no further failures, touchwood.
David Vizzard explains a "home made" water injection system in the turbo section of 'Tuning BL's A-series', or 'the big yellow book' if you prefer. About the only "hi-tech" piece were the jets, which if memory serves was a piece of brass drilled out to 40 thou, threaded and installed into the inlet manifold. He suggested using an oil pressure switch tapped into the inlet as the control. The oil pressure switch is about 5psi, so when the turbo builds up to it's massive 7psi the switch activates a pump and off you go.
We have water injected our industrial gas turbines in the past for increased power. It works well, but you do need an awful lot of water......
>> Edited by phil hill on Thursday 17th July 13:44
We have water injected our industrial gas turbines in the past for increased power. It works well, but you do need an awful lot of water......
>> Edited by phil hill on Thursday 17th July 13:44
You might want to look here if you are planning on a DIY WI system: www.dawesdevices.com/howto.html
Seem to remember a friend used water inj on a Honda CRX along with a Supercharger to great advantage but if your in competition, check the Blue Book, have a bit of a feeling that it might not be legal for certain events. Not sure why etc. May be just Hillclimbs or something. (Too early/memory fading fast)
I have just been offered a Metro Turbo engine & box without a turbo, apparently it was a good motor while in use. Not sure if anything's been done to it as yet, bit would a non turboed turbo engine be any use or do I have to start skimming heads, changing cams etc
Good to see a few nice Minis out on the Berwick Classic over the weekend. Anyone here??
Cheers
Good to see a few nice Minis out on the Berwick Classic over the weekend. Anyone here??
Cheers
annodomini2 said:
The main weak point in the transmission on a metro turbo is the drop gears, apprently changing them for some straight cuts is better.
The double ball race on the end of the first motion shaft is the most common failure IME (although I have heard of drop gear failures). All the newer bearings use a plastic cage which breaks up and the balls eventualy fall out. You can test for this fairly easily, jack one wheel up and with the box in neutral slowly turn the wheel. If you hear a little clinking noise every so often, that'll be the balls falling down from the top of the race to the bottom.
The Turbo box was beefed up somewhat over the standard A+ box, with a stronger casting and larger spigot bearing on the FMS. An unused hole in the web near the aformentioned double row bearing was also removed as it caused cracking.
The problem is simply helical gears+lots of torque = large side thrust on bearing.
Sagalout, the standard turbo lump would be a good basis for a tuned N/A, but in stadard form will be no more powerfull than a standard A+ (62bhp ish). The valve sizes are standard A+, although the exhaust valves are (allegedly) sodium cooled.
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