Katana

I'll do it when I get back mate. Just woke up myself thanks to this cold.

edit: can you post the conversion for Bhp in SI units plz. I've been known to make stupid mistakes over the conversions.

[Edited by Katana - 12/11/2002 11:26:30 AM]

Andy.F

On the topic of engine torque potentially causing con rod failures (Studying engineering at Uni and being a scoob owner you'll be keen to know this)
See if you can calculate the respective conrod tensile and compressive loads on -

Engine A > 280 bhp revving to 8250rpm
(std, very safe factory spec Sti)

Engine B > 350lb-ft torque at 5000 rpm
(recklessly modded car allegedly about to bend its con rods)

Assume a piston&pin mass of 0.5kg and 50% of conrod weighing 0.28kg
Stroke = 75mm Bore = 92mm. (Disregard the effect of conrod length on piston acceleration for this excercise)

Interested to see if you get the same answer as I did

Andy.

EvilBevel

Can we place bets on the outcome ?

Pretty much over my head, but I would expect the biggest stress on the 8250 RPM engine, going by what I read/remember from Maximum Boost.

Katana

Back now, give me about 10-15 minutes to eat my dinner and finish this thing up. I'll make loads of assumptions to make the calculations easier as we only want a comparison it instead of a fixed figure.

edit: without any load applied and lots of assumptions, the tensile force is almost 3 times more for A than B. Now to figure out how to correlate torque and power (2 different things as 1 is distance*force and the other is distance*force/time I think). Long day today.

edit2: Assuming I did not get anything wrong with the conversion and everything, A is bigger than B.

[Edited by Katana - 12/11/2002 8:10:55 PM]

Katana

AndyF, YHM and don't laugh, standard of education has gone down since your time.

Andy.F

Yep, agree with that M8

The standard Sti is putting 2.7x tensile load on its rods.

The combustion forces are double on the high torque motor but when added to the inertia loads on the downstroke, the std STI still has 14% more 'buckling' compressive forces acting on the rod than a 350lb-ft engine.

When you compare the sum change in forces (cyclic) between tensile and compressive, the Sti is subjecting the rods to an extra 50% stress.

Andy

Katana

Yay! So there is still chance of me graduating after all.

When and where did you get your engineering degree? Was it in Strathclyde (best engineering uni in Scotland)?

Andy.F

I done mine at home (OU) I couldn't afford to be a student, had to get a real job too many mouths to feed
I did do my HNC in Glasgow though

How can you be a student and run a scoob anyway you got a rich girlfriend

Katana

I'm a 25 year old student. Dropped out of Starthclyde doing Civil Engineering years ago because I ran out of dough. Now that I've saved up some money and have a better income source I'm studying again in Reading, this time as a mechanical engineer.

OU? I plan to do an electronics degree with them after I finish this course. I know of a few people doing other courses with them.