Short stroke details
Turbo Mini Forums

i have used the search but not really found what im after, i have been thinking about diffrent styles of engine builds recently with the chinanigans with the 1460 turbo ect. what would be needed for a 1275 short stroke turbo? its abit diffrent and its interesting me quite abit. what displacment would a +20 over bore on a 1275 block short stroke CC be? what are the pro's and cons of short stoke engines.
if i knew how to work out the displacement i would do it my self but i dont lol :)
all comments and information welcome

paul

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

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Well, the advantage of shorter stroke is to reduce piston, rod etc speed at a given RPM. This enables you to increase RPM without increasing the speed of the engine internals. It also allows the engine to rev up quicker because of this.

The 1071 and 970 Cooper S engines are the same as the 1275 Cooper S engines except the block is machined down the allow the pistons to reach deck height (or thereabouts). There are several shorter than standard stroke aftermarket cranks so until you choose a crank I can't say what the capacity would be.

I don't know if I would go short stroke turbo for a road car. You have to rev short stroke motors alot more to get them moving because they are higher revving by nature. I was initally going 998 with my build but decided to change crank and pistons to the 1098 variety. I done this to improve torque and make a lazier lump that would pull from lower down.

Well thats my understanding of bore/stroke relationship. I'm sure someone else will be along with a more factual response.

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

i was comtemplating building a short stroke 998cc turbo out of a 73.5mm big bore block to fit into the 1.4 hillclimbing class

id need a crank (billet) with a stroke of 58/59mm, which would mean machining 20mm odd off the block (possible?), or longer rods, or a bit of both?

either way v. expensive so im just following wil & ben_h's route

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

20 mm of the block isnt possible. IIRC its about 15-16 mm thick.

I have a couple of Sth African short stroke cranks here, They`re the same-ish stroke as the early 1071 S donks, but with large journal (2inch mains &1&3/4 big ends) Toughest ever factory crank in my books,,, so i`m building 1170-ish engines with 16v Bimmer twinky Turbo injected, hope to have it spin to 10,000rpms with 25lbs boost

I have short lightweight strong as an ox suzuki forged motorbike pistons, & am now just looking for some very long lightweight strong rods to suit , just so i can keep the std block deck height & as soon as i can afford the rods i`ll stick them both together

Absolutely mind blowing screaming slot car type donk

& not many people seem to know that these Sth African cranks exist oh,,, did i just let the cat out of the bag?

Edited by MadMatt on 15th Oct, 2008.

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

I have one of those aswell, thought about making a 1191 K headed engine (73.5mm bore and 70.2mm stroke), but the need for longer rods made it "difficult"

why dont you buy Neil a few pints and let him explain it all in person, he built one from scratch last year :)

i thought his was a long stoke :) 1355cc

Edited by Paul R on 15th Oct, 2008.

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

yes, S blocks can, but thats only approx 7 mm (for both 1071 and 970, as 970 have different rods). All pre A+ blocks can be skimmed like this. There is a difference between 7 and 20 mm you know

its not got every possible displacement on it but this is usefull, probably got it from some where on tm lol

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Hi guys those South African cranks are quite special. We use them with normal 1275 pistons , deck the block about 6-7 mm and use 998 push rods. Racing engines of this style rev to 9-10 grand easily. But as the other guys have said short strokes are not very torqey so not great road engines but fantastic on the track.

Im planning to use one of these cranks in conjunction with some S rods for my k1100 build. Should be interesting.

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