Rolling road 3.0Si Coupe Vs Roadster
- Thread starter Joycey
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Twin Turbo
Active member
Interesting that only 2% difference, has Lee got any engine mods yet?
When was the last time you both did a oil & filter change?
If you doing an Z rolling road - I might bring my little 2ltr to the party
When was the last time you both did a oil & filter change?
If you doing an Z rolling road - I might bring my little 2ltr to the party
Twin Turbo said:
As far as I'm aware the engine is standard, I have serviced the car 2 times since Feb because I drive her hard. I did have the engine carbon cleaned in the summer but not convinced it did much. I'm slightly sceptical that the engine is stock because there is 20lb,ft more torque over BMW standard figures, Or it's just a really good one from the factory. 8)
Always thought that bhp figures given by manufacturers were taken from the crank? I expected there to be a significant drop at the wheel (or does the rolling road read out allow for this?). If these figures are at the wheel then that's really impressive 
Twin Turbo
Active member
Joycey said:
Oil changes can make a big difference, as I change my oil every 8K
I call shenanigans, and temporarily revoke your bragging rights pending a stewards inquiry!Joycey said:
Seriously though, it's nice to see that BMW weren't ridiculously over boasting the figures in the brochures. Next up for me will be some mild tweaks (induction, exhaust & remap).
Will be looking for a remapping specialist, rather than ones that slaps on a generic download and can't prove what it does. I'll be back with another dyno for evidence of any improvement.
Gazhyde said:
is the graph from dyno reading WHP or BHP?
paulgs1000 said:Always thought that bhp figures given by manufacturers were taken from the crank? I expected there to be a significant drop at the wheel (or does the rolling road read out allow for this?). If these figures are at the wheel then that's really impressive
im sure its already converted to bhp on the dyno chart as if it was WHP then the BHP would be around 290+ which isnt correct. When ive had dynos it normally says WHP. Test car in 4th gear usually best 1:1 ratio then dip clutch to measure drag then calculate.
goldbcfc said:Gazhyde said:
is the graph from dyno reading WHP or BHP?
paulgs1000 said:Always thought that bhp figures given by manufacturers were taken from the crank? I expected there to be a significant drop at the wheel (or does the rolling road read out allow for this?). If these figures are at the wheel then that's really impressive
im sure its already converted to bhp on the dyno chart as if it was WHP then the BHP would be around 290+ which isnt correct. When ive had dynos it normally says WHP. Test car in 4th gear usually best 1:1 ratio then dip clutch to measure drag then calculate.
Yes, they all do that.
Flywheel horsepower is a silly measure of power as what actually matters is how much reaches the wheels. I wish all manufacturers would quote WHP but then it'd expose how silly an idea it is to buy a 320d as an xdrive over 2WD. If they did you'd get a much better expectation of how cars compare with each other.
Flywheel horsepower is a silly measure of power as what actually matters is how much reaches the wheels. I wish all manufacturers would quote WHP but then it'd expose how silly an idea it is to buy a 320d as an xdrive over 2WD. If they did you'd get a much better expectation of how cars compare with each other.
Marlon said:So now I'm confused
What is the dyno run testing exactly? BHP at the wheel and then recalculating to give a crank shaft bhp?
A dyno measures torque, hp is calculated:
HP = Torque X RPM / 5252
That's why the torque and hp lines always cross at 5252 rpm on the graph.
Rolling roads can only estimate flywheel horsepower, they can't actually measure it. Depending on the RR make/type, the estimates are made using a blend of known inertia (roller(s)), torque moment at the retarded, speed and "coast down loss". The dyno dynamics machine shown doesn't use coast down.
Wheel power isn't a certainty either, it's easily affected by numerous factors that can't be reliably quantified, you're right to call up tyres and gearing is a major curve ball with this type of rollers, but you'd expect that to be equal in this case. Wheel power is measured differently on different machines and you'd see much lower wheels figures on a MaHa LPS compared to this for example, with similar flywheel figures.
I regularly use engines dynos and various rolling roads and have never seen a reliable correlation from engine dyno to any rolling road. If you see a result you think is right, you smile, if you don't, you frown. A stopped clock is right twice a day!
Treat it as bit of fun and try not to obsess about the precision or provenance of results.
Wheel power isn't a certainty either, it's easily affected by numerous factors that can't be reliably quantified, you're right to call up tyres and gearing is a major curve ball with this type of rollers, but you'd expect that to be equal in this case. Wheel power is measured differently on different machines and you'd see much lower wheels figures on a MaHa LPS compared to this for example, with similar flywheel figures.
I regularly use engines dynos and various rolling roads and have never seen a reliable correlation from engine dyno to any rolling road. If you see a result you think is right, you smile, if you don't, you frown. A stopped clock is right twice a day!
Treat it as bit of fun and try not to obsess about the precision or provenance of results.
Joycey said:Disca said:At least I now know your Z4F alias Lee
Gimme a shout next time you head down and I'll bring the Z3 along!
Rumbled, We're going to organise a BMW Z day early spring. Keep an eye out :driving:
This was mine years ago at SRR, would be good to have another go next year