Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
Hope I don't start any arguments but I'm looking for a general viewpoint and experience of the different people who use rolling roads or know science.
The 2.1 made 206bhp at the wheels...and Saxon said thus 218bhp at the flywheel.
Thats a 6% transmission loss. Is that even possible to have that low of a loss?? I hear a lot about anything up to a 15% loss?
Input/discuss!
Posts: 4,604
Threads: 90
Joined: Dec 2011
Reputation:
54
Location: Cornwall
Car Model/Spec: 1996 306 DT M-TDI/16
Thanks: 0
Given 20 thank(s) in 18 post(s)
Won't be 6% , just re do the flywheel power based on 10-15% losses and will be more accurate... Would be interesting to take it to another dyno and compare also as they tend to vary akot !
| Dyno Power Runs & Steady State Facilities Available, Just Ask Anytime |
| #DervMafia |
![[Image: sigi-2.png]](http://i281.photobucket.com/albums/kk226/darrenjlobb/sigi-2.png)
Posts: 5,203
Threads: 110
Joined: Jan 2012
Reputation:
20
Location: Devon
Car Model/Spec: Estate, DT, GTI6 and 205
Thanks: 1
Given 30 thank(s) in 30 post(s)
Just looked at my dyno sheet, my car was 150 at the fly and 120 at the wheels so that's about 20% lose
Posts: 3,419
Threads: 120
Joined: Jan 2014
Reputation:
35
Location: Powys / Herefordshire
Car Model/Spec: Rallye/S16 & 175 megane
Thanks: 147
Given 40 thank(s) in 40 post(s)
Mine pulled 182.1ATF and 165ATW unsure what percentage loss that is?
![[Image: 17b33c2a-8471-4313-992e-0a4b324cf926_zps2e63812a.jpg]](http://i143.photobucket.com/albums/r143/matt-taylor/17b33c2a-8471-4313-992e-0a4b324cf926_zps2e63812a.jpg)
Team Cyril
Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
(25-10-2014, 07:13 AM)Matt-Rallye Wrote: Mine pulled 182.1ATF and 165ATW unsure what percentage loss that is?
About 12%...
Which is what I would expect tbh
Posts: 902
Threads: 31
Joined: Oct 2012
Reputation:
4
Location: directly above the center of the earth
Car Model/Spec: tu5 bitza/cherry dt
Thanks: 2
Given 5 thank(s) in 5 post(s)
9% transmission loss on yours matt
Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
25-10-2014, 07:33 AM
(This post was last modified: 25-10-2014, 07:35 AM by Piggy.)
(25-10-2014, 07:19 AM)306Dan Wrote: 9% transmission loss on yours matt
I calculated it from both figures and got about 12%?!
How did i do that...
Ive just done a different calculation and 165 at the wheels is 90.6% of the ATF figure...random...so yeah, about 9%!?
Posts: 3,419
Threads: 120
Joined: Jan 2014
Reputation:
35
Location: Powys / Herefordshire
Car Model/Spec: Rallye/S16 & 175 megane
Thanks: 147
Given 40 thank(s) in 40 post(s)
The way i look at it, no dyno is accurate. but it gives an even spread between the cars there on the day so whatever mine is piggy yours is at least 40bhp more 
Team Cyril
Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
Hmmm.
I like to look at the torque more anyway to be honest 
Posts: 5,205
Threads: 91
Joined: Dec 2011
Reputation:
83
Location: Oxfordshire/Cornwall
Car Model/Spec: Moonstone DT/Volvo V50
Thanks: 2
Given 41 thank(s) in 41 post(s)
Ugh people seem to get confused with accurate vs correct...
The dyno is highly accurate... The problem lies with the correction of HP atf and atw... If our stupid country wasn't obsessed with flywheel figures, we would be fine!!!
The figure at the wheels is pretty much comparable with every other dyno, end of the day it's measuring torque which is simply the force applied at a foot away... Hardly a complicated calculation... Why don't we all just compare our at the wheels figures... That we we'd actually know what sort of power each persons car is making...
(16-05-2016, 10:45 AM)Toms306 Wrote: Oh I don't care about the stripped threads lol, that's easily solved by hammering the bolt in.  Nanstone GTD5 GT17S - XUD9TE
Volvo V50 D5 R-Design SE Sport - Daily cruise wagon.
Posts: 1,950
Threads: 55
Joined: Dec 2011
Reputation:
17
Location: Rotherham
Car Model/Spec: 406 V6
Thanks: 3
Given 10 thank(s) in 10 post(s)
Depends how they've done the coastdown losses tbh, they can be buggered up fairly easy if the ramp down is much faster (i.e, they don't let it slow the same amount of time for lower revving cars as the high ones, etc)
Custom roll cages/shiny suspension bits/general fabrication work undertaken, PM me.
Top engine mount repair/reinforcement/chocking for cracked chassis and high powered cars, drive in, drive out, 2 hour turnaround.
Posts: 19,854
Threads: 581
Joined: Dec 2011
Reputation:
195
Location: Bournemouth
Car Model/Spec: Supercharged 306 GTi6
Thanks: 36
Given 82 thank(s) in 78 post(s)
(25-10-2014, 08:18 AM)Ruan Wrote: Why don't we all just compare our at the wheels figures... That we we'd actually know what sort of power each persons car is making...
Because most people see a higher figure and think oh that sounds better and because of that, everyone follows.
End of the day, it just doesn't matter. Its all well and good having shit loads of power but if the delivery of that power is awful, chances are your not going to be as quick as you hope!
Team Eaton
1999 China Blue 306 GTi6 - Eaton Supercharged - 214.5bhp 181lbft
Posts: 5,205
Threads: 91
Joined: Dec 2011
Reputation:
83
Location: Oxfordshire/Cornwall
Car Model/Spec: Moonstone DT/Volvo V50
Thanks: 2
Given 41 thank(s) in 41 post(s)
Trying to calculate coastdown losses is like trying to calculate power by licking your finger and putting it in the fuel tank...
You're measuring the static losses, not dynamic losses... Surely the power lost when coasting down isn't the power lost when stuffing 320lb.ft through it.
(16-05-2016, 10:45 AM)Toms306 Wrote: Oh I don't care about the stripped threads lol, that's easily solved by hammering the bolt in. Nanstone GTD5 GT17S - XUD9TE
Volvo V50 D5 R-Design SE Sport - Daily cruise wagon.
Posts: 4,604
Threads: 90
Joined: Dec 2011
Reputation:
54
Location: Cornwall
Car Model/Spec: 1996 306 DT M-TDI/16
Thanks: 0
Given 20 thank(s) in 18 post(s)
What Ruan said ^^
No transmission creates the same "losses" while coasting down on a rolling road, than when its under full load..
ATW is a far more useful number anyway, given this is the number your acaully putting down on the tarmac, why do you think all Americans use this figure, the UK is just obsessed with ATF figures because there always higher, and depedant on what tranny losses are inputted / generated (99% of dynos dont generate it, they just use an average for the car) its so easy to make the ATF figures wildy higher / lower than they really are...
| Dyno Power Runs & Steady State Facilities Available, Just Ask Anytime |
| #DervMafia |
Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
25-10-2014, 08:56 AM
(This post was last modified: 25-10-2014, 08:56 AM by Piggy.)
Posts: 3,419
Threads: 120
Joined: Jan 2014
Reputation:
35
Location: Powys / Herefordshire
Car Model/Spec: Rallye/S16 & 175 megane
Thanks: 147
Given 40 thank(s) in 40 post(s)
So my rallye came with 167ATF and now makes that at the wheels with no power mods...
yay 
Team Cyril
Posts: 1,748
Threads: 41
Joined: Dec 2011
Reputation:
12
Location: Midlands
Car Model/Spec: Dtractor
Thanks: 0
Given 6 thank(s) in 6 post(s)
If your wheels were full of cement your transmission losses would be less
Posts: 18,242
Threads: 386
Joined: Dec 2011
Reputation:
87
Location: Suffolk
Car Model/Spec: Focus Titanium
Thanks: 1
Given 118 thank(s) in 117 post(s)
When we did the RR at college the losses were roughly 15-20bhp (not sure what percentage that is though, cars were saxo's/106s/Clios and my standard Golf so nothing high powered).
Funniest thing was my mates original Mini though...made 40bhp ATF, lost 20bhp through the tranny! 
Posts: 1,950
Threads: 55
Joined: Dec 2011
Reputation:
17
Location: Rotherham
Car Model/Spec: 406 V6
Thanks: 3
Given 10 thank(s) in 10 post(s)
25-10-2014, 06:03 PM
(This post was last modified: 25-10-2014, 06:06 PM by Rippthrough.)
(25-10-2014, 08:31 AM)Ruan Wrote: Trying to calculate coastdown losses is like trying to calculate power by licking your finger and putting it in the fuel tank....
That works! If it comes out tasting like petrol, that's +50bhp right there!
If it comes out tasting like chips, that's -50.
The problem with ATW figures is they're not actually correct as soon as you put the car on the road, a roller causes far more tyre distortion and heat build up than normal road use. Hub figures/dynos tend to be a lot more consistant there, as it takes that out of the loop, but obviously still don't actually give you a power output that's accurate in the real world.
Custom roll cages/shiny suspension bits/general fabrication work undertaken, PM me.
Top engine mount repair/reinforcement/chocking for cracked chassis and high powered cars, drive in, drive out, 2 hour turnaround.
Posts: 15,646
Threads: 541
Joined: Dec 2011
Reputation:
124
Location: Aylesbury
Car Model/Spec: 320bhp Impreza WRX
Thanks: 7
Given 59 thank(s) in 58 post(s)
From what I've seen it tends to be 15-20% on a BE3 box on a dyno dynamics rr
Posts: 3,539
Threads: 42
Joined: Mar 2012
Reputation:
28
Thanks: 3
Given 89 thank(s) in 88 post(s)
only one thing for it
RAAAACCCCCEE!!!!!
Posts: 3,419
Threads: 120
Joined: Jan 2014
Reputation:
35
Location: Powys / Herefordshire
Car Model/Spec: Rallye/S16 & 175 megane
Thanks: 147
Given 40 thank(s) in 40 post(s)
(25-10-2014, 09:36 PM)welshpug Wrote: only one thing for it
RAAAACCCCCEE!!!!!
This!
Team Cyril
Posts: 20,092
Threads: 591
Joined: Nov 2012
Reputation:
54
Location: Cotswolds
Car Model/Spec: Stage 13 16v HDi
Thanks: 22
Given 68 thank(s) in 68 post(s)
See you on the track next year matt...in my rear view mirror
Posts: 3,419
Threads: 120
Joined: Jan 2014
Reputation:
35
Location: Powys / Herefordshire
Car Model/Spec: Rallye/S16 & 175 megane
Thanks: 147
Given 40 thank(s) in 40 post(s)
(27-10-2014, 08:03 AM)Piggy Wrote: See you on the track next year matt...in my rear view mirror
When your spinning backwards on the grass and im speeding away maybe bacon boy
Team Cyril
Posts: 5,205
Threads: 91
Joined: Dec 2011
Reputation:
83
Location: Oxfordshire/Cornwall
Car Model/Spec: Moonstone DT/Volvo V50
Thanks: 2
Given 41 thank(s) in 41 post(s)
(25-10-2014, 09:15 PM)Dum-Dum Wrote: From what I've seen it tends to be 15-20% on a BE3 box on a dyno dynamics rr
Lol! Dyno Dynamics Shootout mode simply applies 15% transmission losses on FWD cars because they're aware of how bloody inaccurate it is!
(16-05-2016, 10:45 AM)Toms306 Wrote: Oh I don't care about the stripped threads lol, that's easily solved by hammering the bolt in. Nanstone GTD5 GT17S - XUD9TE
Volvo V50 D5 R-Design SE Sport - Daily cruise wagon.
Posts: 229
Threads: 11
Joined: May 2013
Reputation:
0
Location: Stockholm, Sweden
Car Model/Spec: 306 GTI-6 trackday toy
Thanks: 0
Given 2 thank(s) in 2 post(s)
Can't we just agree to only use chassis dynamometers? The fact that you can adjust your hp by pumping your tires harder just makes for inaccurate figures..
Tinkerer of 306gti6 trackday racer, less stuff, more hard, more umpf, more stop.
Posts: 4,604
Threads: 90
Joined: Dec 2011
Reputation:
54
Location: Cornwall
Car Model/Spec: 1996 306 DT M-TDI/16
Thanks: 0
Given 20 thank(s) in 18 post(s)
Just compare whp figures, its the most accurate thing to compare to. And yes it although it may not be "real hp" to the wheels due to tyre resistance and other things, its still the most comparable thing dyno to dyno. flywheel HP depends on so many factors / is so easy to screw.
| Dyno Power Runs & Steady State Facilities Available, Just Ask Anytime |
| #DervMafia |
Posts: 18,242
Threads: 386
Joined: Dec 2011
Reputation:
87
Location: Suffolk
Car Model/Spec: Focus Titanium
Thanks: 1
Given 118 thank(s) in 117 post(s)
How do manufacturers accurately test new cars power? As they all give fly figures obviously. Or do they just estimate with some maths/magic somehow?
Posts: 5,205
Threads: 91
Joined: Dec 2011
Reputation:
83
Location: Oxfordshire/Cornwall
Car Model/Spec: Moonstone DT/Volvo V50
Thanks: 2
Given 41 thank(s) in 41 post(s)
Engine dyno!
Stick the engine straight on the power absorbing mechanism... No losses!
(16-05-2016, 10:45 AM)Toms306 Wrote: Oh I don't care about the stripped threads lol, that's easily solved by hammering the bolt in. Nanstone GTD5 GT17S - XUD9TE
Volvo V50 D5 R-Design SE Sport - Daily cruise wagon.
Posts: 18,242
Threads: 386
Joined: Dec 2011
Reputation:
87
Location: Suffolk
Car Model/Spec: Focus Titanium
Thanks: 1
Given 118 thank(s) in 117 post(s)
Ah, that's a lot more simple than I was assuming!
|
![[Image: 17b33c2a-8471-4313-992e-0a4b324cf926_zps2e63812a.jpg]](http://s143.photobucket.com/user/matt-taylor/media/17b33c2a-8471-4313-992e-0a4b324cf926_zps2e63812a.jpg.html)
![[Image: 22f2b6b2-758b-4c1c-96fb-6fa9c6059b13_zpsf306b56b.jpg]](http://i585.photobucket.com/albums/ss299/Ha11elujaz0rs/22f2b6b2-758b-4c1c-96fb-6fa9c6059b13_zpsf306b56b.jpg)
