Discussion
Just had my Cerb dyno'd today and it made 305 bhp @ wheels, 296 ft torque,( Engine speed )on one graph and the other graph it shows 312bhp ( mph speed) dont know the difference between the 2??? has anyone got any ideas as to how to calculate the figure for power at flywheel. I would post the graphs but have no idea how to do it.
Just looking at a cerbera graph i've had done today .. 305 at teh wheels .. that's a great figure .. I have a graph here that's 280 ish at the wheels / 350 at the flywheel .. so 305 at the wheels is 370/375 at the flywheel, obviously depending on the rollers used etc etc but the wheels figures are usually pretty accurate as long as the rollers are calibrated regularly and properly.
you have a powerful car there .. no excuses on track now though paul
you have a powerful car there .. no excuses on track now though paul
I dont get this, 305 at the wheels leading to 370 at the flywheel...
thats just not right, this aint an auto transmission...
Take for instance - the VERY efficient Borg T5, and then the overpowered baby BTR differential with bogus hydratrak, then take the miniscule tiny driveshafts and baby CV joints... and what about the joke of a lightweight propshaft that connects the front to the rear... then you've got an extremely well setup twin disc clutch in there - thats one 'lightweight' setup! that has a very low frictional loss....
I've spoken to a dozen performance guys, even an F1 engine building firm, not to mention the man himself Al Mellings, the guy who designed the damn thing (well my guys spoke to him and his team)... the drivetrain losses on a 4.5 are between 29-35 tops! and on average 29-30ish... thats with 255/40/17's with standard alloys taken into the equation for *marginal* tyre loss...
The way I see it, MCD (Al Mellings engineering company) have had this engine on an engine dyno, and they know its true output at the flywheel (not a hypothetical calculation based on RWHP and a number of estimated figures but an actual torque sensor system).... and if they have confirmed that the max they ever got out of a 4.5 for the roads was 362bhp, and then once the alternator/ac production level cam gear (cheap heavy stuff), lower cr, you're talking roughly in the equation of 340-355bhp at the flywheel... thats of course on an MCD 'well tuned' engine...
the red roses with their 'performance' touches will push more obviously... but the drivetrain losses will not suddenly drop or increase....
MCD confirmed that the highest figure for a production level V8 AJP 4.5 produced in engineering on an engine dyno.
But they do say, there were some very exotic versions of the AJP they did build, for just 'testing' sake (which did not make it to production due to a number of reasons)... and I'm willing to put down money to say one of those 'well sorted' engines was used in the factories early day press tests etc...
The drivetrain loss of a cerbera, based on the words from the engine designers/builders... is roughly along 29-35. If you want to dial in 50+hp, then someone is going to be very happy, but, it doesnt go hand in hand with the guys who have tested numerous AJP's on a computerised engine dyno.
anyway, my rant over...
thats just not right, this aint an auto transmission...
Take for instance - the VERY efficient Borg T5, and then the overpowered baby BTR differential with bogus hydratrak, then take the miniscule tiny driveshafts and baby CV joints... and what about the joke of a lightweight propshaft that connects the front to the rear... then you've got an extremely well setup twin disc clutch in there - thats one 'lightweight' setup! that has a very low frictional loss....
I've spoken to a dozen performance guys, even an F1 engine building firm, not to mention the man himself Al Mellings, the guy who designed the damn thing (well my guys spoke to him and his team)... the drivetrain losses on a 4.5 are between 29-35 tops! and on average 29-30ish... thats with 255/40/17's with standard alloys taken into the equation for *marginal* tyre loss...
The way I see it, MCD (Al Mellings engineering company) have had this engine on an engine dyno, and they know its true output at the flywheel (not a hypothetical calculation based on RWHP and a number of estimated figures but an actual torque sensor system).... and if they have confirmed that the max they ever got out of a 4.5 for the roads was 362bhp, and then once the alternator/ac production level cam gear (cheap heavy stuff), lower cr, you're talking roughly in the equation of 340-355bhp at the flywheel... thats of course on an MCD 'well tuned' engine...
the red roses with their 'performance' touches will push more obviously... but the drivetrain losses will not suddenly drop or increase....
MCD confirmed that the highest figure for a production level V8 AJP 4.5 produced in engineering on an engine dyno.
But they do say, there were some very exotic versions of the AJP they did build, for just 'testing' sake (which did not make it to production due to a number of reasons)... and I'm willing to put down money to say one of those 'well sorted' engines was used in the factories early day press tests etc...
The drivetrain loss of a cerbera, based on the words from the engine designers/builders... is roughly along 29-35. If you want to dial in 50+hp, then someone is going to be very happy, but, it doesnt go hand in hand with the guys who have tested numerous AJP's on a computerised engine dyno.
anyway, my rant over...
interesting.
as tim act said, you see 50 bhp on relaitvely laigthweight griffs .. you'll get 30bhp losses on locaterfield type cars at high aquivalent road speeds on the rollers..
the figure I'm saying here is taken off the graph i have infront of me, that's all the info i have. it's not a constant figure of course, it increases with roller speed .. at low speed it's only 10bhp or so, at 150mph eqivalent roller speed it's 70... on this graph.
i think these figures are fairly typical.
this is going to open a whole debate up again, because properly calibrated roller dynos can be surprisingly accurate when you put known good cars on them eg bmw / porsche etc. they'll give you figures that are within single figure differences of the published figures from those manufacturers. Not every dyno can be wrong, and by exactly the same ammount.
It also goes against my belief that the airflow potential of the std 4.5 cerbera ajp8 is 380-390bhp and 355-370 lbs torque in road trim, installed in the car .. cos that's what we see on different and well respected dynos ..
I've also just bought an in-car accelerometer which will give an *indication* (ie not accurate, but close enough to show massive errors) of the power at the wheels, which let's face it is what properls the blinking thing forwards .. it's what's left actually as the tractive force .. any other hp figure is largely irrelevant.
as tim act said, you see 50 bhp on relaitvely laigthweight griffs .. you'll get 30bhp losses on locaterfield type cars at high aquivalent road speeds on the rollers..
the figure I'm saying here is taken off the graph i have infront of me, that's all the info i have. it's not a constant figure of course, it increases with roller speed .. at low speed it's only 10bhp or so, at 150mph eqivalent roller speed it's 70... on this graph.
i think these figures are fairly typical.
this is going to open a whole debate up again, because properly calibrated roller dynos can be surprisingly accurate when you put known good cars on them eg bmw / porsche etc. they'll give you figures that are within single figure differences of the published figures from those manufacturers. Not every dyno can be wrong, and by exactly the same ammount.
It also goes against my belief that the airflow potential of the std 4.5 cerbera ajp8 is 380-390bhp and 355-370 lbs torque in road trim, installed in the car .. cos that's what we see on different and well respected dynos ..
I've also just bought an in-car accelerometer which will give an *indication* (ie not accurate, but close enough to show massive errors) of the power at the wheels, which let's face it is what properls the blinking thing forwards .. it's what's left actually as the tractive force .. any other hp figure is largely irrelevant.
joolz, I hear what you're saying... at the end of the day (a cliche or what), I think the RWHP says it all, its what you put down on the road that counts.... in my way of thinking (which is arcane, I know), I want the power at the wheels, not at the flywheel, its the delivery that I'm interested in... and if anyone out there is pushing 350-400bhp+ at the wheels with an NA engine, then thats heaven... 
SXS said:
joolz, I hear what you're saying... at the end of the day (a cliche or what), I think the RWHP says it all, its what you put down on the road that counts.... in my way of thinking (which is arcane, I know), I want the power at the wheels, not at the flywheel, its the delivery that I'm interested in... and if anyone out there is pushing 350-400bhp+ at the wheels with an NA engine, then thats heaven...
400 at the wheels would be very nice indeedy
TooTall Paul said:
Julian thanks for sorting my car this weekend, you'll be glad to know its running spot on now fuel consumption is far better now and theres no smell of petrol now
Thanks again
Paul
thankx for the update Paul .. good to see you and the car once again
we need to get you onto the next phase now .. more power
joospeed said:
yeah Tim it's somewhere up there, it's a lot more than griffs and chims, heavier car with wider tyres and those factors over two roller contact patches per tyre really add up.
JOOLS, having my 1998 4.2 put on a dyno next
week. what sort of power should i expect to
see at the wheels?
verminator said:
JOOLS, having my 1998 4.2 put on a dyno next
week. what sort of power should i expect to
see at the wheels?
We had one with a sports exhaust and cats in, which on Saturday put out 350Bhp at the fly.
Can't remeber what the wheels fig was. But the fly fig was certainly higher than some 4.5's
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