How much bhp is lost through gtir 4wd

[gtiroz]

"the truth is out there"

a nice simple explanation:
http://www.car-videos.com/articles/horsepower_torque.asp

the no-crap approach:
http://www.sdsefi.com/techdyno.htm

some good descriptions from actual operators:
http://www.g-force-motorsport.co.uk/dyno/rolling road detail 2.htm
http://www.ktrperformance.com/services/dyno_faq.htm
http://www.ultimategarage.com/dynapack.html

and if you wanna get technical:
http://www.fordcaprilaser.co.uk/rolling_road_article.htm
http://www.revsearch.com/dynamometer/torque_vs_horsepower.html
http://wahiduddin.net/race/dynotest.htm

that last one contains the only actual printed calculation i have ever come across!
Drivetrain loss, hp = 4.874 *10(power of)-2 * MPH + 3.517 *10(to the power of)-4 *MPH(to the power of)2
(can someone who knows maths give that a go please

and just ftr:
downunder we have always quoted at-the-wheels 8)

 

[Rishi]

I see wot your saying, but why duz it hav to be a percentage as opposed to a fixed figure. The drivetrain can`t be adjusted so therefore cant take any more power from a more powerful engine. which using a percentage indicates it duz!!!

wish i had the answers for you but i don`t
perhaps we could interrogate the r/r guys on the 25th,you could even threaten to fry them if they don`t give up the info :twisted:

We're going to have a wide variation in bhp figures on the RR day on the 25th so I'll post them up and you'll be able to work out if it is a set percentage loss or simply a set bhp loss...


Rishi

 

[Fast Guy]

"the truth is out there"


that last one contains the only actual printed calculation i have ever come across!
Drivetrain loss, hp = 4.874 *10(power of)-2 * MPH + 3.517 *10(to the power of)-4 *MPH(to the power of)2
(can someone who knows maths give that a go please

That formula must be specific to the car in that article. For example, that formula says you're losing 8.391hp at 100mph, the other problem is that the formula is implying drivetrain losses are fixed at any speed and have nothing to do with 2wd/4wd the gear you're in or anything, because if you applied it to a Skyline or a Skoda the only variable is mph.

 

[Spikey]

Let's stir this up again

 

[red reading]

18 - 25 % is the variation for 4wd between differant dynos, the true variation will differ due to each gearbox/transferbox/rear diff's condition.

 

[PobodY]

...including what oil is in them etc?
Does a helical gearset lose more than a straight-cut?

 

[Mad]

Let's stir this up again

:lol:

I think most dyno's allow 23 - 24%.

 

[red reading]

...including what oil is in them etc?
Does a helical gearset lose more than a straight-cut?

Yes oil thickness will have an effect and helical gears have side thrust loadings by design and wider teeth for the gears width than straight cut so by that you have created more transmission losses thru friction than straight cut

 

[PobodY]

:doh: I've seen your other post on this subject now, so would have known that if I'd read it first.

I guess you need to look at every bearing and friction surface; lubricate/harden/polish them to give you the least resistance if you really want to reduce the losses. - Do the losses change slightly with gearing; for example does 4th gear introduce less resistance than 1st?

 

[mikeyp]

yes, simply because the ratio is different and the actual gear cog is a different size so the amount of friction is different inside the box.

 

[red reading]

:doh: I've seen your other post on this subject now, so would have known that if I'd read it first.

I guess you need to look at every bearing and friction surface; lubricate/harden/polish them to give you the least resistance if you really want to reduce the losses. - Do the losses change slightly with gearing; for example does 4th gear introduce less resistance than 1st?

yes, but the next thing you have with differant gears is the fact thay are torque multiplyers or reducers depending on ratio