DASHOCKER

iTrader: (2)

here is the basic math. 300 horse at the crank and 245 on average at the wheels. Where is the other 55 horses?? Synthetics do lessen the parasitic losses. You are correct about the diff, and I don't believe that by changing that alone, you will get 9 horses. Changing out all the fluids that are a part of the drivetrain to synthetic will make it run cooler and smoother. The molecular structure of sythetic oil is quite different than dino oil. It has more lubricity which equals less friction, it also runs cooler which means lower operating temperatures. Less friction and heat equals more power. Other guys can chime.. MIT has done well for you Vetteboy. I like ya

Vette Boy

Thanks for the kind words, Dashocker. BTW, I went to Iowa (BSEE), not exactly MIT, but hey, this isn't rocket science

BTW, I do use synth for everything I can. I agree it's better. IMHO, the better is mainly related to high temp and longevity and there is some friction advantage esp after the dyno oil is beaten on for a time. And I don't think RP is bad, just expensive and not as tested/charactorised as Mobil1. So I go with Mobil1 (also 'cause I'm lazy and can buy it at Autozone).

dsouth

iTrader: (4)

Don't know about 9 horses but I'm running that in my Diff.

ChronoJ1

iTrader: (2)

Me too.
It's smooth, but I don't notice that much of difference from other brands.

BA_GS400

iTrader: (1)

Have you ever felt hot gear oil? Put your hand on a hot differential? I know I have. I can assure you it's more than 1500W. And yes, 746W = 1hp.

I've got all the knowledge I need to believe that it's more than 2hp. Even without numbers, I'm saying that the empirical data cannot be denied, thus it must be more than 2hp.

Luckily, DaShocker put it into other words for us. We lose 55hp (roughly) through "drivetrain losses".

Judging the technical nature of your posts, I simply wanted to hear more about your data.
"where did you get the 2hp number from?".
It just sounded speculative by assuming that a rear-end can't generate more heat than a ceramic heater.

I was just hoping to get your opinion on where these 55 hp are being lost at if the rearend is ONLY responsible for 2hp loss. (which I do disagree with)
I'm sure you'll agree that it's worldly accepted that drivetrain loss is between 12% - 20% for a majority of vehicles. Working from that, it's hard to believe that the rear-end causes only 4%.

http://www.google.com/url?sa=U&start...yno.htm&e=9797
http://www.team3s.com/~matthews/dyno.html
http://www.eng-tips.com/viewthread.cfm?qid=74391&page=1
These people like testing and have tested both trannys and rear-ends:
http://www.swri.org/
http://www.swri.edu/4org/d03/vehsys/...%20Testing.pdf

Elsewhere: (and across the country on Dynojets everywhere)
"The following polynomial approximates the drivetrain loss as a function of speed in MPH, which was measured as negative horsepower on the DynoJet chassis dyno. This expression is valid from 0 to 130 mph:
Drivetrain loss, hp = 4.874 *10-2 * MPH + 3.517 *10-4 *MPH2

Dyno spindown test...
"On the DynoJet, you measure the drivetrain losses by running the car up to a ceertain speed and then simply pressing in the clutch to disconnect the drivetrain from the engine. As the speed slowly decreases, the dyno measures the total drivetrain losses due to the transmission, differential, CV joints, bearings and tires."

"Differential losses in the commonly used Hypoid type gearset is in the order of 6 to 10%."

http://www.sdsefi.com/techdyno.htm

DaveGS4

iTrader: (2)

BA,

I've read all the links you posted and I can't find anything at all that disputes what was quoted by vette boy.... it's all very generic stuff about drivetrain loss and I didn't read anyone arguing about that being a factor. I've heard more than one Lexus tuning expert quote the 2GS auto (for example) at 20 - 21% and that is what I use as my general assumption.

Maybe I missed it, but what I didn't see is:

1) breakdown of drivetrain loss components that attribute different percentages to the different components... transmission, rear end, tires, wheels etc. what specifically is attributed to the rear diff.

2) actual temp of a hot rear diff with dino oil compared to one filled with a synthetic (not based on a burned hand )

3) and best proof ever would be the same exact test run with a little more scientific conditions. I watch Horsepower TV all the time and while I like the show, they are totally OWNED by the sponsor to sell the product. It's a giant infomercial.

Do a dyno run with fresh dino differential oil for a baseline. Do another with a fresh quality synthetic (Mobil or Redline). Do a final one with Royal Purple.

If you find an independent dyno shop and either do the differential oil changes yourself (or pay for them + product) in between (similar conditioned) dyno runs and it shows even a 5hp difference I'll pay for the dyno runs up to $80

BA_GS400

iTrader: (1)

yeah, I know that none of them were quite as explicit as he would like or as I would have hoped, that's why I said that the "empirical" evidence is already there. (15% loss for entire drivetrain)
However! There were some very very good anecdotal evidence though: The spin-down dyno test. That's math right there. I don't know the size of the drum, or it's weight, or it's speed, but those ARE known numbers. Without a doubt, that is a method right there and they are saying 6% - 10%.

There is also some breakdown of data at the SWRI.org. I spent hours reading there.
They showed auto vs manual trannys and steady state vs under load and also 1st gear vs 4th gear. I saw nothing for the torque convertor specifically. They also had bearings and u-joints as well. Most of that only added up to about 6% or so, leaving a lot left over between the TC and entire rear axle assembly. I think I recall a 1.5% - 2.5% loss for a manual tranny, in 4th gear, under cruise conditions.

It's a bit surprising that you mentioned "I can't find anything at all that disputes what was quoted by vette boy". I mean, that IS my point. He did not give enough data to factually state that there is less than a 2hp loss!! I really really want to see hard data on that because the empirical data is very much in disagreement!

I'm not really debating the 9hp gain of Royal Purple or any other oil, dino or synth. That's possibly in the realm of possibility whereas the 2hp speculation doesn't seem to be.

BA_GS400

iTrader: (1)

This is interesting info from a friends of mine..

"It really all depends on what type of differentail you are considering, but the bevel type(non-spiral) non-locking differential is the basic one. This is also the best case scenario, because it happens to be the most effieient.

In any gear train, you multiply the effieiencies between each gear set to find the final efficiency.

Since you measure HP based on the total power output from both wheels, then at the least you have 2 gear sets. (I am assuming you know how a basic differential works)

The book says bevel gear with no spirial can obtain, with good lubrication(I assume they used graphite for the test) and no oil friction a power efficiency of .99 This is under low stresses. If the stresses increase, you lose more power to the deformation of the gears and axels.

So .99*.99 = .98

SO its 98% efficient or has a 2% loss either way you want to look at it.

.98 * 50HP = 49HP

So even in the absolutly best case scenario, low stresses, no losses due to friction in the oil, and a straight bevel gearset you still lose 1 HP out of 50.

In a more real world scenario, spirial bevel gears are used since they dont "whine" at high speeds, (this is what is in most cars) are stronger and thus more resistant to fatigue failure. In an oil bath, the spirial bevel gears are about .96 efficient.

.96*.96 = .922 7.8% Loss

.922 * 50HP = 46.1HP Loss of 3.9HP

So this is still without friction on the bearings, other rear-end rotating mass, or high stresses on the gears. "

.

DaveGS4

iTrader: (2)

Gotcha..

My point is that none of that info (including the new stuff) addresses why there would be any significant (which is what I asume the quoted 2hp is) difference between quality, fresh dino diff oil or even a better comparison another synthetic diff oil and fresh royal purple on a dyno test.

Its interesting stuff but it just doesn't prop up what I think was an innacurate 9hp non-scientific (best) or (at worst) biased test on the TV show.

BA_GS400

iTrader: (1)

I hear from a good source, (ie. Dave Meyer, Rob Muzzy's right hand man. You know, World Superbike, Bonneville record holder, right hand man, Kawasaki racing....), that the Bosch Automotive Handbook should have the answer we seek.

He wasn't positive, but, he was pretty certain that it's in there. I'll see if there is one at the local library or bookstore or something.......

We trust Bosch, right?


A.

DASHOCKER

iTrader: (2)

The facts will open all of our eyes, and put an end to the skepticism. Good work BA

DaveGS4

iTrader: (2)

Yes, but I'm pretty certain he wouldn't have done a test like I'm talking about and documented it a Bosch handbook. Maybe it will give a general answer to the typical percentages of drivetrain loss for each component of the drivetrain though which would be good to know.

BA_GS400

iTrader: (1)

Hey Dave, you and I are reading different things from VetteBoy's posts.

I read his post to say that the entire differential as a whole, no matter what oil, will not lose more than 2hp due to frictional and rotational loss. That was his basis for saying the 9hp was a bogus number. ie. how can you gain 9hp when the rearend as a whole doesn't even account for more than 2hp loss!
So, my disagreement with that is that I'm sure a rear-end loses more than 2hp due to fricitonal and rotational losses.

Sounds like you were reading VetteBoys's posts to say that there would not be a 2hp difference between any oils. Perhaps VB should clarify for the both of us.

Meanwhile, I'm off to the store to look for that book.

PS. your last sentence is correct. Dave Meyer himself did not input to the Bosch Automotive Handbook of course, and I DO NOT expect to see comparisons in the Handbook, but I do expect to see basic range of HP loss in a standard rear-end.

Where's VB?

BA_GS400

iTrader: (1)

well damn, I went to 3 bookstores and none carry the Bosch Automotive Handbook, but all would order it for me.

Mr. Meyer is out of touch for 2 weeks, but said he could look in his copy when he returned.

Vette Boy

I can't find my copy, it's buried somewhere. Let's use your numbers for efficency and see where they take us.

PD = Power dissipated by diff
PIN= power into rear diff (Flywheel HP minus the transmission loss)
POUT = power out of rear diff (very close to RWHP)
n = effiency of gearset (between 96% and 98%)

PD = PIN - POUT
PIN * n = POUT

PD = PIN - PIN * n

PD = PIN (1-n)

Using 97% and 250HP, then PD equals:

PD = 250(1-0.97) = 7.5HP

Using 97% and assuming an input power of 250HP, then PD = 7.5HP or ~5kW (1HP = ~750W). Subtract 7.5HP from 250HP, it's close to stock RWHP (Pout of diff). I could see 5kW being dissipated by the rear diff's case without getting too hot.

Use 7.5HP for the power dissipated in the diff, how many HP is RP going to save over good dyno oil? How about Mobile1? If RP is even 10% better (highly unlikely), then it saves only 0.75HP.