SR3 HP at the real wheels?
Discussion
I've got one that shows very very fractionally south of 200 RWHP for the K8 1475.
Of course what mustn't be forgotten about is the near turbocharged levels of increased gee-gees created by the 'can't be replicated on the dyno' ram air effect.
In the apparent absence of a smilie for someone mooning ........
Of course what mustn't be forgotten about is the near turbocharged levels of increased gee-gees created by the 'can't be replicated on the dyno' ram air effect.
In the apparent absence of a smilie for someone mooning ........
I feel that it is the torque figures that are more unrealistic than the BHP numbers (BHP is only a function of torque and revs after all).
The efficiency of engines is normally compared with BMEP (Brake Mean Effective Pressure expressed in psi) with the maximum BMEP at maximum torque, the rpm where the cylinders are filling the most completely.
For example an engine of around 1585cc (96.7 CI) which may produce around 173ft/lbs
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) therefore:
BMEP = (150.8 x 173) 96.7 = 269.8 psi.
F1 engines struggle to get anywhere near 220 - 230 psi.
A torque figure approaching 100 ft/lbs per litre is extremely (unbelievably) good with anything over this simply fantasy. The high BHP figures could be achieved if the engine holds the torque higher up the rev range.
Have a google for BMEP and see what comes up!
The efficiency of engines is normally compared with BMEP (Brake Mean Effective Pressure expressed in psi) with the maximum BMEP at maximum torque, the rpm where the cylinders are filling the most completely.
For example an engine of around 1585cc (96.7 CI) which may produce around 173ft/lbs
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) therefore:
BMEP = (150.8 x 173) 96.7 = 269.8 psi.
F1 engines struggle to get anywhere near 220 - 230 psi.
A torque figure approaching 100 ft/lbs per litre is extremely (unbelievably) good with anything over this simply fantasy. The high BHP figures could be achieved if the engine holds the torque higher up the rev range.
Have a google for BMEP and see what comes up!
Martin B said:
I feel that it is the torque figures that are more unrealistic than the BHP numbers (BHP is only a function of torque and revs after all).
The efficiency of engines is normally compared with BMEP (Brake Mean Effective Pressure expressed in psi) with the maximum BMEP at maximum torque, the rpm where the cylinders are filling the most completely.
For example an engine of around 1585cc (96.7 CI) which may produce around 173ft/lbs
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) therefore:
BMEP = (150.8 x 173) 96.7 = 269.8 psi.
F1 engines struggle to get anywhere near 220 - 230 psi.
A torque figure approaching 100 ft/lbs per litre is extremely (unbelievably) good with anything over this simply fantasy. The high BHP figures could be achieved if the engine holds the torque higher up the rev range.
Have a google for BMEP and see what comes up!
Even for N/A cars, some of the newer production cars are approaching this figure. E.g. 458 Italia = 4.5 litres & 398 lbs ft @ 6k rpm. BMEP is also a function of the type of engine design (number of valves, head design, plug positioning, etc)The efficiency of engines is normally compared with BMEP (Brake Mean Effective Pressure expressed in psi) with the maximum BMEP at maximum torque, the rpm where the cylinders are filling the most completely.
For example an engine of around 1585cc (96.7 CI) which may produce around 173ft/lbs
BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) therefore:
BMEP = (150.8 x 173) 96.7 = 269.8 psi.
F1 engines struggle to get anywhere near 220 - 230 psi.
A torque figure approaching 100 ft/lbs per litre is extremely (unbelievably) good with anything over this simply fantasy. The high BHP figures could be achieved if the engine holds the torque higher up the rev range.
Have a google for BMEP and see what comes up!
Also you can compare BMEP at specific revs to get a picture of how tractable an engine is, with effectively a plot of it's cylinder filling efficiency (port design (inlet& exhaust) + the scavenge capability of the exhaust system.
Martin B said:
The 458 Italia is hardly a normal production car though is it??
It is probably nearer a race engine than most production road car engines. The torque figure is very believable though as it is still some way off 100 ft/lbs per litre, if exceptionally good though.
Some of the tuned 2/2.2/2.3 litre duratecs are also approaching 100 lbs ft/litre.It is probably nearer a race engine than most production road car engines. The torque figure is very believable though as it is still some way off 100 ft/lbs per litre, if exceptionally good though.
The bike engines (e.g. K7/K8) are also in a state of tune (even in stock form) over and above most car engines (Honda's VTEC units aside).
With the latest engines, there's no need to go looking at highly tuned and perhaps delicate exotica to see outputs in and around 100bhp and 100ftlbs per litre.
For example, the engine in the latest (albeit confusingly numbered) BMW 550 > 4.4 litres, 407bhp (at 5.5 > 6.4K) (probably PS) and 600Nm (442ftlbs)(at 1.75 > 4.5K
). And I dare say that will be capable of going to the moon and back (whereas the Ferrari?).
Since edited to show what at what rpm.
For example, the engine in the latest (albeit confusingly numbered) BMW 550 > 4.4 litres, 407bhp (at 5.5 > 6.4K) (probably PS) and 600Nm (442ftlbs)(at 1.75 > 4.5K
). And I dare say that will be capable of going to the moon and back (whereas the Ferrari?).Since edited to show what at what rpm.
Edited by splitpin on Friday 3rd September 13:17
[quote=fergus
Some of the tuned 2/2.2/2.3 litre duratecs are also approaching 100 lbs ft/litre.
The bike engines (e.g. K7/K8) are also in a state of tune (even in stock form) over and above most car engines (Honda's VTEC units aside).
[/quote]
Approaching 100 ft/lbs per litre is fine, claiming substantially over it is not. I would still be surprised for any of the stock bikes to be anywhere near 100 ft/lbs per litre. I know the ZZR1100 is old hat but that only had 81 ft/lbs of torque, I think the stock Busa is under 114 ft/lbs.
Also 100 BHP per litre is easy with a 4 valve head provided the rpm is high enough to allow for the drop off in torque.
Some of the tuned 2/2.2/2.3 litre duratecs are also approaching 100 lbs ft/litre.
The bike engines (e.g. K7/K8) are also in a state of tune (even in stock form) over and above most car engines (Honda's VTEC units aside).
[/quote]
Approaching 100 ft/lbs per litre is fine, claiming substantially over it is not. I would still be surprised for any of the stock bikes to be anywhere near 100 ft/lbs per litre. I know the ZZR1100 is old hat but that only had 81 ft/lbs of torque, I think the stock Busa is under 114 ft/lbs.
Also 100 BHP per litre is easy with a 4 valve head provided the rpm is high enough to allow for the drop off in torque.
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