Help with engine spec
Turbo Mini Forums

Right this is the first turbo engine ive gone to spec up. Its not in full detail as its not mine so i dont know how much he is willing to spend on the engine.

1380 a+ block
Omega pistons, 11cc dish
25cc fast road head Exhaust. 29.4mm Inlet. 35.6mm
Mspd ph 2 cam
Metro T3
Standard crank and rods
Lightened fly and backplate
Grey pressure plate
Minispares x-pin diff
SC drops
Standard gears
BK450 Gasket
Standard rockers
Megajolt setup
Intercooler

I know there is a turbo oil pump and other things like that required.

With this spec i get a estimate of 8.5cr, i know he wants to run between 15 and 18psi with the possibility of more in the future.

Any suggestions or recomendations on this?

Thanks

Jackman

Edited by Jackman on 20th Nov, 2008.

Manchester Minis

That collection of parts seems reasonable.

One thing that sprang to mind is the porting on the head, how big were the ports made?

I would get the crank tuftrided and balanced and get the rods polished to remove any possible fracture points.

I’m concerned by the lack of auxiliaries mentioned.

My main points of concern within that are:

Turbo I would put a 360 degree thrust bearing in for more support and maybe change

What about cooling?

Intercooler has been mentioned, what intercooler has your friend decided on?

Isn't the Mspd Ph2 camshaft a fast road one? This is not the same as the Avonbar ph2.

I recon the Kent 274SP for that engine

the CR IS WAY TO HIGH 9.25:1
you wont get past 11 psi of boost there without detonation on nearly

18cc accralites ar NLA Unless you commission a set of 5 and a 9 week lead time

i would opt for a 1293 engine and 10 cc omegas cast at £270 but.... forged if you budget will allow and 28 cc in the head, this would give you a CR of 8.38:1 more like it

its simpley piston avalability with the right cc in the crown.

i managed last week to get some accralites last of stock +40s 14 cc dish forged.

but there are many permutatios in pistons its if you want to machine them out etc..........

cam chioce in my book phase 2, kent 266 or mg cam the chioce is yours

Edited by BENROSS on 20th Nov, 2008.

I got 8.6 steve, ill get back to you about that gearbox in the new year.

Sam - ill most prob get him to get a benross head so will be those port sizes. As for auxiliaries ill have a more in depth spec when i get to talk to him fully and find out how much he will spend on it.

Cooling, most prob a 2 core rad, intercooler i cant say at the moment as i havent spoke to him about that either.

V - Is the avonbar the better option on the cam?

Sprox - Its not my engine but ill let that cam choice be known too.

Benross - i get 8.5/8.6 on that spec, have i done somthing wrong caluclating it?

Thanks everyone.

Manchester Minis

With 11 cc pistons and 25cc chambers with a 1380 I get more like 9.9:1!! How have you calculated it?

You need another 7 cc from somewhere to get 8.5:1.

the Avonbar PH2 cam would be my choice for this engine too.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Similar spec to the engine I'm currently building.

On 20th Nov, 2008 Sprocket said:
I recon the Kent 274SP for that engine

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."

wil-h
sweptt 345cc

unswept
head volume 25 cc
piston dish 11cc
head gasket bk450 3.8cc
ring lands 2cc

total 41.8cc

calcs to 9.25:1

Thats assuming the piston crown is dead level with the deck face though isn't it?

There are a lot of assumptions here.

I use slightly different figures to steve (gasket 2.5cc and I ignore ring land). Hence why my figure looks higher.

This of course means that in reality my CR is lower than calculated. But this ia a safety margine I can cope with. also as I only ever build 998s the ring land volume really is bugger all.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Manchester Minis

swept of 344
unswept of 45

so unswept+swept=390

390/45= 8.6.

Agree, 8.58 from those figures.....

Is your deck volume actually going to be 5.25cc though ???

Mine was 1.8cc when I actually measured it (depth micrometer to top edge of piston with DTI to ensure true TDC, then maths; pi * (d^2)/4 * depth )

Schrödinger's cat - so which one am I ???

Of the aftermarket pistons I have fitted, they have all been about 40 thou down the bore, that includes Megas and Omegas

40 thou=a fookin mile.

yes it is, but it at least alows you to decide how to engineer your compression ratio, which I think is the main reason for it.

I had to take 20thou of the top of jackmans block to keep the compression ratio the same as standard.

40thou is around 5cc

Edited by Sprocket on 22nd Nov, 2008.

Yep, mine were 14thou down for 1.8cc so the maths is about right...

Schrödinger's cat - so which one am I ???