r5 bhp fly wheele to road diferance

smithyr5

Wrench Pro
Points
26
From
warminster
Car
renault 5 gt turbo
hi there people.
can anyone tell me why the r5 looses so much power in transmition.
i have a rolling road print out that basicly says i have lost 50 bhp between the fly wheel and the tyre.

why?????
 

Loz

Torque King
Points
252
From
Wolverhampton, U.K.
Car
MX-5
Tyre pressure will have a large effect on readings, what pressures are you running? If their quite low then that might go some of the way to explaining the loss.
 

smithyr5

Wrench Pro
Points
26
From
warminster
Car
renault 5 gt turbo
no its gota be more than that. i have tw0 rolling road print outs now from two differant places. jan speed being one of them and they both say a loss of around 40/50bhp from fly wheel to the road.
first test said 167bhp at the fly and 126 at the wheel.
second (janspeed) says 189bhp at the 130 at the wheel.

dont get me wrong the car is sweet as and has a new upraited clutch.
tyres are solid. not sure of the psi.
speeking to the tester at janspeed. who has an r5. he said he has hurd of this and dosnt know the answer why.
 

MasterAuron

Very Senior Member
Points
242
From
379bhp 359lbft
Car
Mk1 Focus RS
Something isn't right. Both rolling roads probably.

189bhp will be about 150-160whp for a FWD car. RR's are a bit of a dark art, a large number of factors affect the results; correction factors, tyre pressures, how accurate the dyno is in the first place etc etc etc etc.
 

SLEEPER

Pro Tuner
Points
552
Power figures are just that . If you cars goes well dont worry.

The drop between ATF and ATW is because the power made at the flywheel has to go thoough the clutch - gearbox - transmission and wheels to the ground,
None of the above can be 100% efficient so there will be a loss. This loss is calculated by the machine so if the engine is in the car and being measured by rollers all flywheel figures are by calculation only . People use them because they are higher. To me thats daft .
This "drop" varies dramatically between FWD RWD and AWD and the power level makes a difference as well.
Plus all dynos give diferent readings even the weather affects the result ( especially on turbo cars) and the calculations vary from one tuner to another.
 

SLEEPER

Pro Tuner
Points
552
The power you actually have is fixed The power the dyno says you have isnt because rolling roads differ a lot .

Lower tyre pressures reduce wheelspin (thats why drag cars run low pressures - its harder to spin the wheels.)

Any lack of grip on a dyno and the power reading will be less as its measuring the turning forces .So you will change the dyno figure but unfortunately your car wont be quicker when it comes off the dyno.
 

smithyr5

Wrench Pro
Points
26
From
warminster
Car
renault 5 gt turbo
yeah i understand. its fine as i am happy with the power of the car anyway. she gose like a rocket. lol
i will do a strip run this summer and see what she can do that way. lol
 
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