Rolling road result

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smcnairn

Guest
Had my ar at Star performance on friday for a power run. After not being happy with the Profec b settings decided to disconnect it and use a forge manual type of boost controller set at 1bar. On the graph below u will see the results of 220.5bhp at the wheels.:-D The Engine output reading is way out because of something to do with the drag or transmission reading being out. what is the usual loss of power through the transmission with the Gtir??. Done a search and found 28% is this right? Also can someone explain the drag curve? what is it showing and why could my flywheel reading be so far out??



 
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AJ4

Guest
the transmission loss is a fixed value not a percentage ( increases slightly with power level because of the extra momentum though ). If it was fixed at 30%, then a 1000 bhp car would use 300 bhp just to turn the gearbox ;) :D I think its around 40 - 60 bhp from what I can gather on a Pulsar ?
 
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smcnairn

Guest
Fire & skill said:
thats a nice power delivery :)

are you running an uprated turbo? its saying 374
Click to expand...
No its still standard turbo, if u look at the difference between the engine output 374bhp and the wheel power 220bhp. The engine power is way out for some reason? i was expecting 260-280bhp engine power. Dont know whats up with that reading I would of thought the drag should be smooth curve on the graph?
 
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smcnairn

Guest
gtir bean said:
i got 200 at the wheels and 302 at the fly if that helps.
Click to expand...

Cheers for that gives me a better idea of what mine is. Im well impressed with the result if thats the case:D
 
PaulB

PaulB

Member
Glad to see your rolling road session went well. Im booked in their at the end of the month. Ive got new plugs and leads to fit, aswell as a filter and exhaust. Hes gonna set my car up to run 1BAR boost with a Forge manual boost controller.
Im well lookin forward to the trip now.
 
Fire & skill

Fire & skill

Vintage member
are you sure its std tubby?

my old R: RR at star performance


336bhp
292lb ft torque.

using RB box (dakar)

mods: hks evc3 (set to 1.2 bar for run)
k&n ind kit
standard t28 turbo
standard injectors
standard internals
remap by buddyclub Japan
helix clutch
 
Last edited:
Rishi

Rishi

Still waiting on some shims!
AJ4 said:
the transmission loss is a fixed value not a percentage ( increases slightly with power level because of the extra momentum though ). If it was fixed at 30%, then a 1000 bhp car would use 300 bhp just to turn the gearbox ;) :D I think its around 40 - 60 bhp from what I can gather on a Pulsar ?
Click to expand...

Its roughly 24% loss through the 4x4 system...


Rishi
 
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AJ4

Guest
RishiGTiR said:
Its roughly 24% loss through the 4x4 system...
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How can it be a percentage ?

I've got 300 bhp and I'm cruising at 70 mph on the motorway with 24% trans loss so I lose 72 bhp through the transmission.

Then I turn the boost up so my car is now capable of 1000 bhp :D Even though I'm travelling at the same speed, and the same rpm, my transmission loss suddenly shoots up to 240 bhp ?

Tranmission loss is completely independant of engine power, thats why it can't be a percentage of engine power. If it was you could turn the transmission loss up and down with the boost controller ;)

I think we got wires crossed here Rishi as you should know better ! ;) You meant 24% for a standard car at 220 = 53 bhp, not 24% all the time ?
 
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Odin

Guest
Yes I've always wondered how you can lose more power through the transmission as you BHP goes up, Surely its a fixed thing not something that changes with power out put lol.


Rob
 
Rishi

Rishi

Still waiting on some shims!
AJ4 said:
How can it be a percentage ?

I've got 300 bhp and I'm cruising at 70 mph on the motorway with 24% trans loss so I lose 72 bhp through the transmission.

Then I turn the boost up so my car is now capable of 1000 bhp :D Even though I'm travelling at the same speed, and the same rpm, my transmission loss suddenly shoots up to 240 bhp ?

Tranmission loss is completely independant of engine power, thats why it can't be a percentage of engine power. If it was you could turn the transmission loss up and down with the boost controller ;)

I think we got wires crossed here Rishi as you should know better ! ;) You meant 24% for a standard car at 220 = 53 bhp, not 24% all the time ?
Click to expand...


Not 24% all the time.... But still 24% loss while accelerating at full throttle even at higher power levels...

220bhp car will lose about 50bhp through turning the drivetrain which accelerates the car at a certain rate...

Now a 1000bhp car will lose more power as it is having to turn the same weight of drivetrain at a greater rate...

The energy needed to rotate/accelerate a drive train increases with the rate of acceleration...

This is proven on engine and then on rolling road dynos...

If I'm wrong then there are a lot of tuner claims that need to be changed... eg RC who managed 700bhp @ Wheels and from that claim 930bhp @ Fly...



Rishi
 
Fast Guy

Fast Guy

Moderators
Staff member
Don't transmission heat up when more power is put through them? Hence sometimes a transmission cooler is fitted?
So I take it this increase in heat is due to increase transmission losses or something like that:?
 
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AJ4

Guest
hmmmmmm, should I believe a tuners power claim..? :D:D:D

I agree that the apparent 'loss' goes up with acceleration, but not power. Nothing in the drivetrain is changing, its the same weight and same rotational mass, therefore it shouldn't matter what power the engine is, the load ( and therefore the drag ) is still the same.

I'll give you that it increases with 'rate of change' or acceleration , because of the extra shearing forces on the oil / mating surfaces etc, but I'm sure its not a fixed percentage of engine power.
 
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geoff pine

Well-Known Member
GTIR BEAN think you have read the chart wrong bhp is more like 242 if not then thats a 50% increase at the fly wheel . mine made 209bhp at the wheels thats about 259 bhp using the 24% method your at the wheel figure is to low.;)
 
gtir bean

gtir bean

New Member
hmm,thats what it says anyway.it should be more than 250 at 1 bar anyway.it made 289 on different rollers.arent standard r's meant to be about 150 at the wheels?
 
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geoff pine

Well-Known Member
No your at the fly wheel figure is 302 most people qoute at the fly wheel figures .my own figure is 259 bhp more like .8/9 bar your looks good.
 
gtir bean

gtir bean

New Member
;-) i see.i was going to have a look at the print out but i dont know where i put it now.im sure it will be on the rollers again soon.:p
 
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