Thread: Torque curve ?

Originally Posted by scrambler

It might have the "torque curve" lower, but that's due to less torque higher, rather than more torque lower. The Subaru STi puts out 392 Nm of torque to 4000rpm. The 2.25 LR motor puts out 166 Nm at 2500rpm and 134 Nm at 4000. What's the bet that the STi puts out more than 166 Nm at 2500 rpm? It's just got MORE higher up. The displacement is pretty close. Don't have time to find whether the STi is over- or under-square, but the 2.25 is marginally oversquare ("short-stroke") at 90mm bore and 88mm stroke. http://www.csse.monash.edu.au/~lloyd...Rover/Engines/

urmmm thatd make it undersquare..... (but then the stupid american under and over square stuff always threw me.


why is it i remeber it as being an 89mm bore on a 93mm stroke.... making it a long stroke.

Im going to go dig out the old rebuilders manual when I tidy the shed this weekend....

Originally Posted by mcrover

Do the same with a 2.25 in a SIIa.

My old boat my Triton couldnt pull it out of the water in High range but the old 2a did it easy.

My IIa would be lucky to pull itself up a boat ramp. Hmmm, actually I'd better get back to fixing it.

Originally Posted by Blknight.aus

urmmm thatd make it undersquare..... (but then the stupid american under and over square stuff always threw me.


why is it i remeber it as being an 89mm bore on a 93mm stroke.... making it a long stroke.

Im going to go dig out the old rebuilders manual when I tidy the shed this weekend....

Looking at the manual I think its 90.47 bore and 88.9 stroke for both diesel and petrol 2.25

Originally Posted by Blknight.aus

the wrx motor is a short or square stroke motor ( I cant remember which) and develops peak torque at 4500rpm. (as an example)

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Don't forget that a WRX engine, whether long stroke or short stroke has a turbo charger hanging off it. I think that would influence power and torque delivery a lot more than the bore / stroke relationship!

Torque (rotating force) - In layman terms it is the leverage of the connecting rods over the crank pushed by the big bang that happens upstairs above the piston crown. The better the leverage and the bigger the bang the more push around of the fly wheel or Torque converter turning whatever is behind it.

Max power is produced at an optional point in the rev range where the inlet gas speed is at such at point where it is mixing the fuel into the air really, really well and you get a optional burn of the mixture and everything else is working together pumping the air in and gas out super efficiently as per the engines design.

When I hotted up my 1991 HD evo motor and dyno'd it. Max torque was there straight off idle and stayed flat accross the rev range. Max power achieved at 4,500 rpm even though it was capable of revving to 7000rpm as it had a screaming eagle computer under the seat. 1,340 cc of pure hang on and be terrified if needed to.

Inlet AIR speed, compression, excellent combustion, cubic inches (BIG CC'S for you youngsters) and good extraction of the exhaust gases along with getting the spec right so it all works together usually does the job. (except when I melted the heads to the block of my first 350 chev - slight mishap with the nitros)

Regards,
BradM

Originally Posted by Slunnie

My IIa would be lucky to pull itself up a boat ramp. Hmmm, actually I'd better get back to fixing it.

Well it did when it was running, actually my 2a had a 186 but we dragged the boat with a mates 2a shorty most of the time and the couple of times we didnt and used the triton we found the triton had to work a lot harder to pull it out with water in the bilge where the landy just putted out in high the triton needed low and a gut full of right foot.

It wasnt a big boat, 14' but built of steel sheet with steel boyancy tanks either side and running a 289 winsor and a for/rev gearbox and soft clutch made for a heavy little boat but it used to pull my huge skeleton out of the drink on skis and drag the doughnut around great and Ive been told by the bloke that bought it off me that it is great in the bay, it sits flat and doesnt rock around like the other boats the same size.

THe previous owner to me also had a landy S2 with a 202 and trimatic that he dragged it around with and told me that Id be lucky to pull it out with the triton.

Originally Posted by Slunnie

Looking at the manual I think its 90.47 bore and 88.9 stroke for both diesel and petrol 2.25

Spot on. 2.25 landie engines and Subie WRX engines are BOTH Oversquare (stroke shorter than bore). A Subaru WRX is 89 and 75 mm. So only 17% difference in bore-stroke ratio between the two.

A 4BD1 engine is 104mm bore and 118mm stroke, so Undersquare (long stroke).

Originally Posted by BigJon

Don't forget that a WRX engine, whether long stroke or short stroke has a turbo charger hanging off it. I think that would influence power and torque delivery a lot more than the bore / stroke relationship!

Very true. NA Subie engines are generally quite torquey (low down).

Torque depends on LOTS of different things, not just bore/stroke ratios.

Originally Posted by BradM

Torque (rotating force) - In layman terms it is the leverage of the connecting rods over the crank pushed by the big bang that happens upstairs above the piston crown. The better the leverage and the bigger the bang the more push around of the fly wheel or Torque converter turning whatever is behind it.

Max power is produced at an optional point in the rev range where the inlet gas speed is at such at point where it is mixing the fuel into the air really, really well and you get a optional burn of the mixture and everything else is working together pumping the air in and gas out super efficiently as per the engines design.

When I hotted up my 1991 HD evo motor and dyno'd it. Max torque was there straight off idle and stayed flat accross the rev range. Max power achieved at 4,500 rpm even though it was capable of revving to 7000rpm as it had a screaming eagle computer under the seat. 1,340 cc of pure hang on and be terrified if needed to.

Inlet AIR speed, compression, excellent combustion, cubic inches (BIG CC'S for you youngsters) and good extraction of the exhaust gases along with getting the spec right so it all works together usually does the job. (except when I melted the heads to the block of my first 350 chev - slight mishap with the nitros)

Regards,
BradM

Love the work! - don't agree with the second paragraph. Power = torque x revs. It's that simple. The torque peak is the only true "peak" in the engine design - THAT is the optimum combustion point. Peak power comes higher only because there is the multiplier effect of RPM, and if the torque peak remained flat forever then the power would go on rising. After a certain rpm, depending on a multitude of design features as you say, efficiency drops, torque drops and eventually power drops.