9 replies to this topic

[Cooper-202S]

Does anyone know why despite being a long stroke engine why the 1098's have one of the lowest compression ratios of all the a-series engines?

[liirge]

less stress on the crank??
also werent they built to be economical, hence put in vans and mokes in australia

[Ethel]

It is actually slightly higher than 998 & 850's of a similar age.

Back in the day we had 2 star and 4 star leaded petrol, performance cars with higher compression needed 4 star. "Economy" vehicles had a lower compression ratio to burn the cheap stuff, and also run on the lower grade fuel that was all you could get in many countries. MG1100 engines have higher compression.

[Cooper-202S]

Ethel "Back in the day we had 2 star and 4 star leaded petrol"

God you just made me feel old, I'd forgoton 2 Star petrol.

I had thought it was to do with low octane fuel but couldnt remeber that.

Thanks for the response.

[minidaves]

yes and remember 1098s are made of cheese and designed for torque not revs and they do that very well, rev them and they go pop

dave

[benb12]

They're not that bad, underrated I think...

[roofless]

best engine I had was a 1098 - brilliant and fun.

[Cooper-202S]

yes and remember 1098s are made of cheese and designed for torque not revs and they do that very well, rev them and they go pop

dave

I'm working on the basis that steel caps and a 4 bolt center are a must as well as wedging and balancing the crank, a good damper wont hurt other than in the wallet. (Just why are they so expensive?)

Has anyone run one of these on twin carbs, what were results?

I think there is a realy drivable engine hiding in there somewhere>

[benb12]

I recommend you read this, it's very informative for tuning 1098 engines.

http://www.minimania...28/ArticleV.cfm

And a conclusion from Calver himself, for those non-believers:

Far from being the 'non-revving, boring, slug motor' the 1100 has been drubbed with, it's a very capable engine that gives exceptional results for little cash input. It would quite easily pull a 3.1FD without loosing the performance results here. In fact it would probably enhance it, allowing further distances to be covered in all gears with a more relaxed cruising speed.

Further - what I think it REALLY needs is a Mini Spares Centre 'Clubman' close-ratio straight-cut gear kit and 3.1FD to see what it can do!

During the rolling-road session, the needle choice proved to be very close, although a little on the rich side - particularly on full load. After some discussion with Andrew on this, we decided to leave the needle as was (AAA) and adjust the idle mixture up a little to drop the CO at idle from the 5.4% it was reading to 3.5%; thus raising the jet and theoretically leaning the mixture out across the whole range. The merest hint of adjustment brought about a massive change in CO reading! Removing the dashpot, Andrew revealed the jet was all but flush with the bridge. This affects the way the carb performs quite drastically - generally caused by a worn jet. This would also go some way to explaining the slight over-richness everywhere. A new jet would possibly get things into a better position and improve the fuelling.

Despite all this, the mpg is pretty good. Thrashing the thing mercilessly back from GRV, it returned 35.2mpg. More sedate urban driving and general duty use has raised this to a very respectable 43.6mpg! The 'motorway' run result is very similar to that gleaned from the 998, the urban use is far better. Further testament perhaps to the slightly less 'busy' nature of the 1100. And this would improve again with a fresh jet.

The SW5 cam is a blinder. Buy it and use it in anything road going - you won't be disappointed. It gives - without doubt - the best performance increase throughout the usable rpm range without causing emissions problems. In fact it gives better emissions than most standard, un-tuned, carbed engines I've come across! It has become my first choice road-cam over the 997 Cooper one I've used for so long.

This all goes to prove what I've been banging on about for years - the A-Series is not an rpm monster, so should be tuned accordingly. And an engine built to give best power at 6,500-7,000rpm on the road is a waste and unnecessary. Good torque over a wide rpm band means big fun on the road. You really ought to drive this motor! And a final word from Andrew - 'Blimey! Fit, isn't it?'

Am I sad for spending christmas day wrapping bold tags around sentences? Probably, but I'm waiting for everyone to get up!

Merry Christmas!

[Rosslin Racing]

I have had good resaults with the 1100 engine, put the 1275 head on it, balance the flywheel crank rods and pistons, steel main cap and she will see off most small bore stage ones easy! up hill it just pulls all day and thats with a standard cam carb and Exhaust.

Edited by Rosslin Racing, 25 December 2008 - 06:15 PM.