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Gtir Motorsport club » Tech room » Help and Advice » Driveline loss

Driveline loss

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1 Driveline loss on Thu Jun 04, 2015 5:53 am

gtir_woody

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Does anyone know what % of power is generally lost through our driveline?

2 Re: Driveline loss on Thu Jun 04, 2015 6:52 am

PartyPete

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the one star club
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I saw something on face book about this a few weeks ago and caused a huge argument between people on there Razz

3 Re: Driveline loss on Thu Jun 04, 2015 7:13 am

gtir_woody

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People on this forum are a lot more sensible though Laughing

4 Re: Driveline loss on Thu Jun 04, 2015 7:44 am

ROB_IOW

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Can vary allot .  
If you have sticky  brakes , low tyre  pressure , worn gearbox , old oil's  ..  can be anywhere from 15%  to 30% I believe..  but I could be wrong.  
Mine made 276 atw 330 atfw

5 Re: Driveline loss on Thu Jun 04, 2015 8:07 am

nomad

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I thought it was 30%


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6 Re: Driveline loss on Thu Jun 04, 2015 8:18 am

gtir_woody

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I was talking to a guy today about something completely unrelated and it came up. Got me thinking, I've got no idea how much the driveline actually chews up Laughing

7 Re: Driveline loss on Thu Jun 04, 2015 10:53 am

GTI-R US

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@ROB_IOW wrote:Can vary allot .  
If you have sticky  brakes , low tyre  pressure , worn gearbox , old oil's  ..  can be anywhere from 15%  to 30% I believe..  but I could be wrong.  
Mine made 276 atw 330 atfw    


^^^
pretty much spot on


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8 Re: Driveline loss on Thu Jun 04, 2015 11:38 am

gtir_woody

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That's interesting, I probably wouldn't have thought it was as high as 30%, good to know.

9 Re: Driveline loss on Thu Jun 04, 2015 1:23 pm

Mr B

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gtir technician
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I would say 23% would be good figure to average on if all running gear & brakes in tidy order.
Can't really take rolling road result like rob suggested as that itself is a guess as it measures wheel horse power & then uses run down roller drag data to guesstimate flywheel power & is not always overly accurate & has operator settings that can vary it quite a bit too.
Interesting see what Bobs RR figures calculate it at on a variety of R's & what DD rate fhp accuracy at.
As it a decent new RR & does a lot of R's it could collect some interesting data, would like see figures compared on straightcut par & quaife too.

10 Re: Driveline loss on Thu Jun 04, 2015 2:54 pm

Indy


Now correct me if I'm wrong some years ago I was talking to an engeenering guy who said generally through 4 wheel drive you can lose as much as 75-150hp now I don't know how true this is but again as mentiond in the earlier post would depend in how bad the gears are wore tyres ect hope this helps I don't know how true this is but put it out there for comments:)

11 Re: Driveline loss on Thu Jun 04, 2015 9:45 pm

Mr B

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^ Driveline loss gets well over estimated at times,as an example a n13 nissan sunny 1.6 4x4 was under 90hp output & was still quite nippy despite the loss of a 4wd system with similar design/principle & weight of the R.
Another concern is on power output, more power means more load/thrust in transmission thus more friction meaning more loss but this is not linear so the rule of percentages don't work.
RR using run down test is only measure drag under coasting which totally different to under acceleration so makes the whp calculations conjecture really.
Different transmissions & drivetrains vary so much in terms of bearing friction, windage, driveshaft lengths/mass etc that no average figures or percentages can be that accurately used to cover them.

12 Re: Driveline loss on Fri Jun 05, 2015 10:36 am

FPSChris

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So if you were to make the pulsar fwd you'd have more whp if you could get grip?
Is there anyway to reduce the loss?

I'm not going to, just interesting to know these things!

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13 Re: Driveline loss on Fri Jun 05, 2015 11:10 am

gtir_woody

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I reckon it's an interesting topic, sounds like the best way is to keep your driveline well maintained, I wonder how much impact straight cut gears have as well.

14 Re: Driveline loss on Fri Jun 05, 2015 1:10 pm

Indy


4x4 is more restrictive than fwd cars as the power needs to be transferred through more components ie the drive train.
A good example of this would be in audio they always suggest to use minimum joints in cables as the more joins you have the more the resistance you will have now apply that logic to the 4x4 system and you can take a guess from there.

Although the 'power to the ground' concept is true on launching once you reach a speed where the wheels can Handel the power without wheel spinning you are effectively placing less power to get the car faster

Sorry for the gibberish lol

15 Re: Driveline loss on Fri Jun 05, 2015 1:21 pm

shroom

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Try having 300 BHP in a front wheel drive car though it might not be all its cracked up to be as unless its perfect conditions they can be crap. My cousin had a Turbo civic and it was a right handfull. Not saying some factory front wheel cars are no good its just horses for courses on paper it may seem better but I sure prefer the all wheel drive

16 Re: Driveline loss on Sat Jun 06, 2015 3:57 am

GTI-R US

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@FPSChris wrote:So if you were to make the pulsar fwd you'd have more whp if you could get grip?
Is there anyway to reduce the loss?

I'm not going to, just interesting to know these things!

In a nutshell the answer is yes!

2 cars at same fly Bhp one being 4wd and other 2wd either front or rear wheel drive (rear being better of the two) will be quicker over ground than its 4wd counterpart especially if it has lsd fitted. Once the cars are off the mark the 2wd will pull clean ahead as power to the wheels is superior and also carrying less weight due to having no bulky transfer boxes subframe etc, but it may well struggle in the wet which is where 4wd comes into its own and will be quicker in any slippery conditions such as rallying and so forth.

I will be building a fwd sunny GTI up soon (well within next year after Rasheen is done) it will have all the correct lsd's fitted and be 600+Bhp Bhp @ the wheels so should run possibly low 9s or even late 8sec quarters with good traction off the line as I've an idea how to get the grip down even better than with just using lsd's  so watch this space in around a years time.

As Mr b said I'm going over the top really when I said anything between 15-30% loss as don't think I've seen any 30% losses on Dyno upto yet certainly but had a couple at around 25% which is excessive but mainly due to stuff like binding brakes and poor maintenance of car.

If I get time in next week or so (unlikely as very busy but will try my best) il load some recent Dyno print outs from pulsars and other cars we've ran and then you can work out the average losses on a pulsar.

Straight cut dog gearset will have less transmission losses over a helical or even semi helical cut gearset so lots of things can increase losses.

Just for the record too, some people falsely believe that hub dyno's are more accurate than a rolling road such as we have.
That is 100% not the case and when we were looking to purchase one is the reason we went for a proper rolling road over hub type Dyno. Reason being is the hub Dyno does not give either a semi accurate calculation at fly nor at the wheels as there are none fitted lol.
It's just good for extremely high powered cars such as top fuel dragsters or 1500bhp GTR's that can not get grip on a conventional rolling road so they have no alternative other than to use a hub Dyno. However our Dyno has outstanding grip levels due to cut of the rollers themselves and the brace bars that will pull down car even further if loss of grip is occurring.
There has been (not on mine as of yet) but a 1600bhp Toyota supra ran on the Dyno developments Dyno with no slippage as it's impossible for slippage to take place, most we've ran up till yet is just shy of 900bhp with 1000lbft torque and was a pussycat certainly would not bother me running a 2000bhp drag car on there but would need to make sure it was strapped down very well or......"........... :chop Laughing

That's the reason we went for DD over any other make, not the cheapest by far but certainly the best and most accurate figures I've ever seen on any rolling road and that's what customers want even if it means them going home disappointed as they thought their car was making more, m3 and Audi owners are the worst for this as some leave with their tails between their legs Laughing makes me happy to see their faces as you know my loathing for what seems to be a majority of people who drive those particular 2 types of car so moonie yoursofunny


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Full Race setup's, Servicing, Mot's, Restorations, conversions, fabrication, Worlds largest stockist of quality used parts for Gtir
http://www.gti-r-us.co.uk www.force500.com

17 Re: Driveline loss on Sat Jun 06, 2015 8:09 am

johnny gtir

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Bmw wankers 
Audi is ok or it will be when I get my big power rs6 estate and power past a few R35's

18 Re: Driveline loss on Sat Jun 06, 2015 12:27 pm

shroom

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RS6 estate that's awesome, got to love the V8 such an awesome sound.

19 Re: Driveline loss on Sat Jun 06, 2015 12:49 pm

gtir_woody

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This fwd sunny sounds like it will be nuts bob, looking forward to hear about it in the future then.

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