My APR Supercharger has arrived!

4.2 V8 32v Naturally Aspirated - 414 bhp
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Stoffle32
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Re: My APR Supercharger has arrived!

Post by Stoffle32 » Mon Oct 24, 2011 10:14 am

i dont think he meant by what you saying either, what he was saying that its a bigger loss in terms of power in otherwords lets say you dyno and you get 400hp, and the fly but you know the loss to be 25% you get 300hp thats 100hp loss. Now you tune the car and you get 500hp thats now 375hp at the wheels you now have lost 125hp....
So yes you now have lost 25hp more than earlier... Im pretty sure thats what he meant, as you gain more power you loose more power...
This is how I see it on how he meant it

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JackS4
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Re: My APR Supercharger has arrived!

Post by JackS4 » Mon Oct 24, 2011 2:39 pm

This has always confused me somewhat - how can you gain more power and lose more power ? If between the crank and the wheels the car loses say 100bhp as this is how much is taken up with transmission, 4wd etc etc how can it then lose more bhp if the over all power increases ? If there is say a 50bhp increase in the engine power how can some of this gain be lost as transmission, 4wd etc as it still takes the same effort as before (ie 100bhp).

I know that superchargers consume some of the power they generate as they are driven off the engine so in my example assume its not a FI gain.

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Re: My APR Supercharger has arrived!

Post by Keith@APR » Mon Oct 24, 2011 3:12 pm

This is a good read about dyno testing from Dinan that answers a lot of questions asked in this thread.

Follow this link: http://www.dinancars.com/university/

Click on Dyno Testing and the Modern BMW Engine

You can pretty much take BMW out as this applies to almost all modern engines.

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Re: My APR Supercharger has arrived!

Post by JCviggen » Mon Oct 24, 2011 5:20 pm

Stoffle32 wrote:i dont think he meant by what you saying either, what he was saying that its a bigger loss in terms of power in otherwords lets say you dyno and you get 400hp, and the fly but you know the loss to be 25% you get 300hp thats 100hp loss. Now you tune the car and you get 500hp thats now 375hp at the wheels you now have lost 125hp....
So yes you now have lost 25hp more than earlier... Im pretty sure thats what he meant, as you gain more power you loose more power...
This is how I see it on how he meant it
I think that is indeed how he meant it, but it was wrong. The losses stay about equal if all other parameters outside of power and torque are the same (wheel weight, tire pressure and temperature, gearbox and diff temps,...)
The 100hp loss at 400 would still be 100hp loss at 500.
That's not to judge the accuracy of the dyno reading or anything, it could be miles off for all we know, but the absolute loss does not increase when you add power.
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Re: My APR Supercharger has arrived!

Post by Keith@APR » Fri Oct 28, 2011 1:00 pm

I would have to disagree that the losses stay the same as the power increases.

Out of laziness and not wishing to retype a diatribe on the subject, here's a link that explains my position:

http://www.eng-tips.com/viewthread.cfm?qid=74391

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Re: My APR Supercharger has arrived!

Post by JCviggen » Fri Oct 28, 2011 1:49 pm

They do not stay exactly the same, but the differences can be ignored for the sake of argument because there are much more significant factors at play during dyno runs. I don't think 1 horsepower matters when the tires can easily cause 10hp horsepower of extra drag at 120-130mph tire speed by getting a little warmer (which they do after a few runs on a double roller dyno)

Dyno a car 5 times in a row and watch drag increase significantly. The gearbox and diffs are a small part of total losses. You can't dump 50hp worth of friction (kinetic E into heat) into a gearbox or it would melt. We're talking low single digits loss % for a manual gearbox, and then a few percent increase on that when you increase power (most gears get more efficient at higher loads if the oil film is not compromised) So you'll never notice. But to be entirely accurate I could say "power losses on a dyno stay almost the same when you add power"

It's easy enough to see if you have before and after dyno plots with the drag curve on it.
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Re: My APR Supercharger has arrived!

Post by adsgreen » Fri Oct 28, 2011 3:30 pm

Interesting thread - good point that you can measure any drivetrain loss by looking at the transmission oil temperature change.

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Re: My APR Supercharger has arrived!

Post by P_G » Fri Oct 28, 2011 3:58 pm

JCviggen wrote:They do not stay exactly the same, but the differences can be ignored for the sake of argument because there are much more significant factors at play during dyno runs. I don't think 1 horsepower matters when the tires can easily cause 10hp horsepower of extra drag at 120-130mph tire speed by getting a little warmer (which they do after a few runs on a double roller dyno)

Dyno a car 5 times in a row and watch drag increase significantly. The gearbox and diffs are a small part of total losses. You can't dump 50hp worth of friction (kinetic E into heat) into a gearbox or it would melt. We're talking low single digits loss % for a manual gearbox, and then a few percent increase on that when you increase power (most gears get more efficient at higher loads if the oil film is not compromised) So you'll never notice. But to be entirely accurate I could say "power losses on a dyno stay almost the same when you add power"

It's easy enough to see if you have before and after dyno plots with the drag curve on it.
But it also takes on average 3-4 runs for peak power to be measured on a dyno as the ECU's adapt to the r/r environment and traction available.

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Re: My APR Supercharger has arrived!

Post by JCviggen » Fri Oct 28, 2011 4:38 pm

That's very possible, fortunately not an issue for dyno's like the kind MRC uses. The BHP engine value will remain accurate although wheel numbers will change. I imagine after a few pulls you could have a few horsepower being gained from the transmission oils quickly getting thinner by heating up. All very interesting stuff. Even with the most advanced chassis dynos there is still a degree of guesstimation going on with drivetrain losses but the calculation is consistent and realistic.

I'm still interested what the engine oil temps are like when you track a SC'd RS4, anyone?
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Re: My APR Supercharger has arrived!

Post by S4Player » Fri Oct 28, 2011 4:58 pm

Thats true regarding transmission oils etc my car gained around 15ps once it was iirc. Dougs your best bet on oil temps on an sc rs4 I only ever dragged mine after 6 consective runs i think i seen 115-120 oil temps
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Stoffle32
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Re: My APR Supercharger has arrived!

Post by Stoffle32 » Mon Oct 31, 2011 11:55 am

I tracked my Rs4 yesterday (stock) and oil temp reached 138 degrees Celsius....
In SA though temps are much higher, was around 27 degrees... on a normal day normal running car is around 110 degrees

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Re: My APR Supercharger has arrived!

Post by adsgreen » Mon Oct 31, 2011 1:57 pm

138 is nearing what I'd go for as a safe level - 140 constant or 150 peak then id be pulling back into the pits.
Ideally I look to keep 130c

Wonder if possible to add additional oil cooler? Maybe replace one aux rad with another oil/air cooler. I know their is one oil cooler rad with the main rad and according to the study guide there's a water/oil cooler on the main coolant circuit but I've always found air/air coolers better on track. Would be relatively easy to plump in online with the main cooler with a bypass thermostat using similar principles as the cold air feed.

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Stoffle32
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Re: My APR Supercharger has arrived!

Post by Stoffle32 » Mon Oct 31, 2011 2:08 pm

I think the Oil light comes on at 140 degrees anyways... I wouldnt go higher than 140 degrees myself either...
But I think if you also using a good quality oil made for higher temps I think you should be safe..

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Re: My APR Supercharger has arrived!

Post by PetrolDave » Mon Oct 31, 2011 7:39 pm

Stoffle32 wrote:I think the Oil light comes on at 140 degrees anyways...
I didn't know there was an oil over temperature light?
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Re: My APR Supercharger has arrived!

Post by S4Player » Mon Oct 31, 2011 9:30 pm

I'm sure doug was having a race spec cooler made for the other side just incase but I'm sure when he tracked all was good
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