Con rods for beyond 140bhp?
Turbo Mini Forums

i honestly think that 160 is achievable at the fly

want to pick your brains, i want to build a small bore turbo engine, below i have outlines the engine spec the questions i have are

What work will i need to have carried out on the rods to handle this power level?

what bearings should i use, cam included?
will a grey clutch handle the amount of torque?

Head:
Head not quite sure of yet
11 studs holding the thing down and arp bolts.

Block and engine internals.
120 thou overbore
center main strap
Mini7 spec crank shaft
double row vernier adjustable crank to cam timing set
rods (?)
ARP rod bolt set.
Bearings (?)
cam shaft, I'm undecided yet but something with around 270 degree inlet duration and 300 degree exhaust rotation (Any ideas?)
tapped oil gallery plugs
De restrict water pump hole

Gearbox:
Four pin diff
Stright cut gears
stright cut drops
central oil pickup pipe
Ap Grey clutch (will it hold up?)
billet fly wheel

cheers

Sam

Looks good, I have a few comments:

The cam is to long a duration unless you intend really revving the knackers off you engine 8k+.

The clutch will be close to it's limits.

What turbo you plan on using is missing.

The rods will be more than upto the job

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

www.twin-turbo.co.uk

thinking t2/2.5
dident think of that lol what about 260/260?
standard rods at 160bhp?! surely not

Id say they would be fine with some decent bolts. Depends on where your redline is going to be i guess, and what you intend using the car for.

i dont think its the components durability you should be worrying about, its the cam/head/cr/turbo choice that will be the key factors to big power

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

"did you know you can toast potato waffles?"

It's revs that kill rods not power or torque.

I have used totally standard rods (and I mean totally, not balanced, lightened nothing) and I have 155 bhp, so not too far off. My max. rpm is 7k.

I added ARP bolts last year, but only because I wanted new bolts and it seemend silly to buy standard ones.

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

www.twin-turbo.co.uk

weekend monster really, and the occasional use in the evenings, mebbe some track days and some hill climbs but not very much mileage.

Ive seen a few power graphs of the turbos on minis, it seems that on a 998 the main bulk of power is between 4000 revs and 5700ish.

so ill limit it at 7000 like you will.

because i might be in that area of revs every so often

and could i be cheeky and nab your mj map?

Feel free to use the map, but be careful it will only be a starting point.

Have you had a look at the spec of our 155banana engine?

http://www.twin-turbo.co.uk/The%20Spec.html

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Christ you two are brave!

i think i might have them stress relived and balanced.

even if its not needed, kinda piece of mind thing!

Now bearings. i was thinking vandervell, however currently ive heard the name ACL Duraglide flicked about?

any advice on to whats better?

as stated it really is the rpm that kills rods, or more likly rod bolts.

cylinder psi is in the order of some hundreds of psi which IIRC equates to a couple of tons of pressure on the rod, but at 7-8000 rpm the piston is pulling a couple thousand G

If i've guesstimated right its a couple of tons rod load for piston pressure and a couple of hundred for rpm.

well, peace of mind really, and i was quite alarmed by vegards findings the other day.

Well, that was only the weights. Be sure to have them balances as the guys at the factory must have been both blind, dumb and drunk.

and advice on bearings though vegard, you seem to "the one in the know" at the moment.

use ARP rod bolts

the main bearing bolts are up to the job

I've used A+ rod bolts from Minispares. They really look nice, and would be excellent in a turbo application. Bearings.. On small bore engines it seems as one have to use what's available. I don't really think bearings are much of a big deal to be honest. As long as you've got good oil pressure, what does the bearing do? Nuthin'

this is very true, but i guess its all about the material they are made out of, less friction, oil can only do so much.

im thinking also about the harmonics of the engine, eg frequency's obviously this would kinda depend on the revs of the engine. but could bad bearings design/material make the rod caps and big ends kind of oval by almost a hammering process?

The crank doesnt run on the bearings, it runs on an oil film so as V says, they dont really matter so long as they stay where they should etc.
Its the cold starts that wear the bearings, if you had an electric pump that started before the engine then you could virtually emlinate the wear.

vegard and ian are totaly correct sam

good oil noting less than a 15 /40 grade
changed very frequent

you may push the boundries of 155bhp of wills motor .... but.... it will take some doing ........we are all here to help and thats what turbo minis is about

i wouldn't like to use an electrical oil pump for the overall running in case the fuse went pop

however what about running it from the oil galleries on front (cylinder 1) to the back cylinder 4 on both ends.

if im right in thinking that the oil supply for the main bearings comes from the front gallery? you could tap right into that gallery in the middle, meaning you would have pressure from 3 places before you start up, both ends and the middle, eg the three mains.

Oil pressure is not a problem on the engine Sam, ians statement goes for all cars ... i think ……………?

ian was quoting for start ups from cold that… split second
Anyway when the engine bearings are worn out the motors done many hard miles and will require a freshen up all over

I have spotted the cam idea you have 270 inlet duration is ok the 300 deg exhaust is too radical especially in a small bore motor

Have a look at some cams the guys are using in my book maybe a Kent 266 ?
The right cam choice will make a winning engine.. Make or break!
How the car performs

Edited by BENROSS on 18th Feb, 2008.

Good quality bearings not alot of cash anyway. Regular servicing as the lads said above.

Edited by Jason G on 18th Feb, 2008.

all the advice ive had so far has been great, even if my ideas are Abit wacky.

if i do manage to break 160bhp with a small bore 5 port firstly ill be dead cuffed and more then happy to tell people details about it ect. i understand why people with the 200+ bhp a-series minis are abit hesitant to give out details as theyve done lots of development work.

all ill really be doing is furthering my knowledge and basically bolting all the clever work that has been done together.

yeah its not the running pressure thats the problem, its the lack of pressure on startup etc that means there is no proper oil film.

just keep on top of it with servicing and will be fine with whatever bearings.

vandervell it is then, need to inspect my crank to see what i need yet.

Edited by Sam on 18th Feb, 2008.