100bhp per litre
Discussion
Surley the BMEP is a much better way of messuaring engine effieceny. Anybody worked out the engines mentioned above (I'm far too lazy and tired right now!)
Using this formula I googled for: BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci)
Mine worked out at 200psi (107 BHP / L)
Using this formula I googled for: BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci)
Mine worked out at 200psi (107 BHP / L)
Edited by TB Rich on Saturday 16th December 21:48
Dont mention the Rover K series and reliability in the same sentence please,as for bike engines have no torque Yamaha fzr1000/thunderace unit have good tractability low down,works well in a Bedford Rascal i once drove with the EXUP valve all working as it should & proper geared rear axle.....COMPLETELY BONKERS....but drove like a pussycat,Oh and bullet proof japanese quality(bar the cluth but that was also problem on the T/ace billet basket neccesary)possibly not a good comparison due to low weight.Please dont dismiss bike engines, i beleive high output/performance should not mean engine failure every 5 minutes,something that can be tough compromise with car engines sometimes.
stevesingo said:
A good production engine should have at least 100BHP/Lt and at least 80Lb/ft per lit produced below 6000rpm.
Steve
Bloody hell!, you mean a very good high performance engine, as busa rush has said, why would you need such high specific outputs.
The example you used of cars are all absolute top notch engines that are generally acknowledged of some of the finest engines today.
I think what you are forgetting about is cost, you say that it probably doesn't cost anymore to develop - course it does. The defining factor is that all these high specific outputs have some degree of variable valve timing or variable induction length system. This is the reason that the engines produce such good torque characteristics. You can make any engine within reason provide a huge specific output aslong as the head can physically flow the air and it can take the revs. Hence why race engines have always been able to provide post 100bhp/litre figures for ages and ages.
But they can't provide the torque low dow which is what production engines need to be able to do. I would say that these systems provide the extra cost and complication with the engines which generally isn't needed in everyday cars.
Now if we are talking about high outputs on small engines using direct injection and sequential turbo charging or twincharging thats a different matter!
Edited to add: oops just read your post and you do say they cost more to develop etc... ignore that bit of my post
Edited by bales on Wednesday 20th December 13:24
bales said:
Bloody hell!, you mean a very good high performance engine, as busa rush has said, why would you need such high specific outputs.
Of course they are very high performance engines, that is what us Pistonheaders are all about aren't we
Why? If you rely on capacity to generate your power inefficiently then you are adding unnecessary weight and therefor needing more power to overcome the weight, it goes on. Compare a Civic Type R to a Golf R32, similar outright performance, 300Kg difference in weight and that 300kg mostly is over the front of the vehicle.
As for cost, they do cost more to develop but if more are made then they get cheaper. With even the most basic cars having variable cam phasing these days and direct petrol injection becoming more popular, higher outputs are going to be more achievable. As long as the emission police don't interfere too much.
Steve
Just to resurrect this thread as I missed it before Xmas...
I can't think of ANY car engine that achieves that. All of the >100bhp/litre n/a car engines produce peak power at OVER 7,000rpm, and there are hardly of those any that produce over 80lb/ft per litre (hell, how many n/a engines ANYWHERE produce over 80lb/ft per litre?!?*).
Such an engine would probably cost £15k or more to build, and as a result the car would sell in miniscule numbers or at a substantial loss.
Anyway, I agree with the general principle that it's the area under the curve that is important for general driving...although the VTEC engines are VERY good at punching above their weight on-track and on-a-blat. But I'd like a thicker mid-range (to match my thick mid-rift!)...
* I thought THIS website: http://autoroadtests.com/specificoutp
...was a useful site, but reading it I've noticed some cars have the torque figures mis-posted as the Nm figures, not the lb-ft figures, which messes things up a bit...but it does show that even the M3CSL engine only manages c.80lb/ft per litre. Still an interesting site...
stevesingo said:
A good production engine should have at least 100BHP/Lt and at least 80Lb/ft per lit produced below 6000rpm.
Steve
Steve
I can't think of ANY car engine that achieves that. All of the >100bhp/litre n/a car engines produce peak power at OVER 7,000rpm, and there are hardly of those any that produce over 80lb/ft per litre (hell, how many n/a engines ANYWHERE produce over 80lb/ft per litre?!?*).
Such an engine would probably cost £15k or more to build, and as a result the car would sell in miniscule numbers or at a substantial loss.
Anyway, I agree with the general principle that it's the area under the curve that is important for general driving...although the VTEC engines are VERY good at punching above their weight on-track and on-a-blat. But I'd like a thicker mid-range (to match my thick mid-rift!)...
* I thought THIS website: http://autoroadtests.com/specificoutp
...was a useful site, but reading it I've noticed some cars have the torque figures mis-posted as the Nm figures, not the lb-ft figures, which messes things up a bit...but it does show that even the M3CSL engine only manages c.80lb/ft per litre. Still an interesting site...
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