Cylinder liners in Turbo blocks??
Turbo Mini Forums

I'm thinking of building a large bore, short stroke turbo engine.

Spec :
A+ block with steel main caps and 4 bolt centre strap
Forged 76mm stroke crank
Forged 6"center con rods
+0.060" or 73.5mm pistons with 14./18.cc dish
28cc head with 35/30mm valves.
will run 7-10 psi of variable boost.

Given the cost of all of the above is there any value in having the block linered with the new ductile iron liners that are now available, to strenghten the bores?

What do those in the know think, do liners work with turbo'd engines or do they creat other problems

Seems an awful lot of work and expense in block etc prep, to then only run 7-10psi boost pressure. Are there any specific reasons why you want to do all that work e.g. short stroke crank etc?

I want to build an out and out high rev turbo engine.
The boost is worked out at 6.9-1 static C/R to give 10.5-1 running. To start with anyway.

From my Initial research a square bore to stroke profile is common in the modern turbo engines and also provides easy low compression.

Also the short stroke will allow for higher revs (upto 8000 rpm)
without crank & rod flex issues.
The steel bottom end will hold everything together.

Yes Its a bit of a wish list spec but its meant as a track engine so will get thrashed.

Hence the strength of the bores is about the only weal link left on the short engine.

Edited by cooper-202s on 11th Oct, 2009.

Is there enough metal in the block to get it bored enough to put liners in to bring it back down to 73.5mm???

6.9:1 CR That would be an absolute pig and probably wouldn't even start. Turbos produce power due to the dynamic CR. 10.5 could easily be achieved NA and would basically be the same engine with better manners.

On 12th Nov, 2009 Paul S said:

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

6.9:1 CR

With what cam?

Why short stroke to achive 8000rpm? when I run my engine to 8000rpm and the DON goes beyond 9000rpm on a standard stroke

Edited by Sprocket on 11th Oct, 2009.

This whole thought about the liners came about after being presented with a very knackered engine out of a JCW MPI mini to rebuild last tuesday.
The owner (friend of a friend)is insisting on re-using the origional block as the car has some history Conversion no M002, but it has split a little end of a rod allowing the gudgion pin to completley ruin a bore.
Miraculously the piston and the rod stayed together so the block isnt holed.

The block is already +0.020" and to clear the damage will take a 73mm bore, so I either get it bored 1380 or liner it back to a std oversize which he would prefer.

The engine spec stated is an idea for something that will rev mentaly fast for track use with some wild amounts of boost but I take the point about it not starting. Its something I havent researched properly yet as I want to build the small bore 1100 first.
Either way its going to push all the mechanicals to the very limit which is why I wondered about linering it.

As Sprocket mentions, the DON has revved to 9500rpm on a worked lightened standard crank, worked lightened standard rods, and minispares mega pistons. It has the lightest flywheel I know of and will rev up almost like a motorbike.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

You dont want to break 14.5 on the dynamic compresion when at max boost work back from there and you should find your CR around the 8.8 region (not checked this just thinking on the fly from thr figures I have thrown about)

Own the day

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I dont doubt there are std stroke engines running 8000 rpm regularly, I've only had an engine at that speed once, Briefly before it expired Spectacularly!
"the Don" with which I'm not familiar, is this a drag strip spec or has it been built for endurance.

What I am looking to build is something that will spin up quickly but spend 4 hours going round the track without breaking, boiling or self destructing and not need a rebuild evey time I run it.
I set the upper limit at 8000rpm because that is the running limit of the 1st motion bearing at the end of the gearbox, the bottom end is realy built for 10k.
But is that sustainable for any lenght of time elsewhere in the drive train.

The engine spec was not meant as the basis of the thread as it was somewhat speculative after seeing the crank in question on Friday,
the cylinder liners were.

So the question remains, does anyone know of any inherent problems of fitting liners into the A/A+ block when your going to build a performance engine I.E. Either FI or High compression ratio.

If someone knows I would appreciate the chance to discuss what they have learned.

My thoughts are that it is more in the hands and skill of the machinist as to whether you have liner problems.
If the liner is fitted to a stepped bore and therefore trapped in position by the head all that remains is a good fit in the bore to maintain rigidity and thermal conductivity.