CompressionRate from 9.25 to 10.5
- Thread starter Jorgenson
- Start date
1396midget
Well-Known Member
A skim off the heads would up the compression, but would also require a calculation. My advice (which can be ignored if you like 
) would be to avoid going too high, I'm tempted to try and reduce mine a bit so it can run on normal petrol and not be quite so sensitive to timing and mixture
) would be to avoid going too high, I'm tempted to try and reduce mine a bit so it can run on normal petrol and not be quite so sensitive to timing and mixture
Graeme is right on the money. Having owned and driven a Rover with a 10.5 : 1 engine from 1985 till 2007, and having driven a Rover with a 9.25 : 1 engine on a number of occasions, the latter is definitely the way to go. You can run more initial ignition timing so you'll achieve better engine performance and better fuel economy.
Ron.
Ron.
redrover
Well-Known Member
The best thing I've done to my 2000TC is lower the CR from 10:1 to 9:1 (export TC spec). Before, there were flat-spots through the range and pinking under hard acceleration that was very difficult (and compromising) to dial out. Performance and rev behaviour is now much more like an injected setup - any revs, any gear, any gradient and it pulls smoothly and progressively up the range. Obviously, the revised carbs, induction and remapped distributor is the real cause of that, but the engine itself is now receptive to what those ancillary components feed it.
If this were Top Gear, I'd be labelled a fool. As we all know, according to the ancient automotive philosopher Clarksonius, the brake horse power figure is the most important number....in the world! But, as Graeme says, there are many more things you can do to extract a more meaningful and useful torque curve out of your engine, especially if you intent to use modern fuel in modern traffic conditions. 155bhp@5500rpm is all fair and well on the autobahn, but if you can't get out of the way of the turbo-diesel Fiesta at 20 mph, there isn't a lot of point in extracting it!
Michael
If this were Top Gear, I'd be labelled a fool. As we all know, according to the ancient automotive philosopher Clarksonius, the brake horse power figure is the most important number....in the world! But, as Graeme says, there are many more things you can do to extract a more meaningful and useful torque curve out of your engine, especially if you intent to use modern fuel in modern traffic conditions. 155bhp@5500rpm is all fair and well on the autobahn, but if you can't get out of the way of the turbo-diesel Fiesta at 20 mph, there isn't a lot of point in extracting it!
Michael
WarrenL
Active Member
I run a 10.5:1 engine and, knowing the lower compression engine well, I'd prefer the latter. The 10.5 is a pest. It only likes the very high octane fuel (98 here in NZ) and grumbles if it is even slightly out of tune. If more power is your aim, there are other ways to achieve it, as more knowledgeable gentlemen on this forum will soon tell you.
The day my engine shows signs of tiredness I will be planning a lower compression rebuild. Going the other way is unthinkable to me.
The day my engine shows signs of tiredness I will be planning a lower compression rebuild. Going the other way is unthinkable to me.