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Discussion Starter · #1 ·
Had a great day today. Was actually a bit long, as the Dyno team were having problems with their software. However, the Dyno is SPOT ON with the results on all the cars. So here's how my A5 3.0TDI Quattro got on.

Not exacly chuffed with the Power Figure, but the car is no where near run in yet. results as follows @ 5k Miles:

Power Wheels: 181.3BHP @ 2699 RPM (Book says 240! )
Power Engine: 199.1BHP @ 2719 RPM
Max Torque: 399.7 lbft (543.11NM!!!) @ 2440 RPM - Well Chuffed with that. Book says 500Nm! Remap should take the Torque up to 613.11Nm.

Obviously, 5K is nowhere near enough for the car to have been fully run in. At the moment, i'm 59BHP short than what the book quotes, which is interesting.

The increased Torque, now who would like to explain that? Maybe the V-Power Diesel fuel I'm using?

If any other owners are planning on Dyno'ing their 3.0TDI, the gear mine was Dyno'd in was 3rd Gear.

I'll try and get the dyno report scanned in at somepoint when I have time.

Also keep a look out for the A5's Dyno video being uploaded in the Video Section shortly ;)

Rab.
 

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The power is definitely surprising, but so is the torque... I guess it evens out :p

edit: and thanks for the report. Looking forward to more dynos in the future
 

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Possible answer on Torque figures

Won't the Torque from the engine be different to that at the wheels due to the gear ratio of the gearbox?

If you find out the effective gear ratio (may be close to 1:1 in top gear) and then multiply the wheel value by the square of the gear ratio, I think you should get the Engine torque, minus a bit from drag in the gearbox/final drive

My mech Eng theory is a bit rusty but I think this is probably the explanation.

Other minor point is that the DYNO must be using a certain diameter for the wheels, so that might be off a bit aswell.

Did the DYNO read the 40/60 torque split between front and rear axles correctly?
 

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Discussion Starter · #4 ·
Won't the Torque from the engine be different to that at the wheels due to the gear ratio of the gearbox?

If you find out the effective gear ratio (may be close to 1:1 in top gear) and then multiply the wheel value by the square of the gear ratio, I think you should get the Engine torque, minus a bit from drag in the gearbox/final drive

My mech Eng theory is a bit rusty but I think this is probably the explanation.

Other minor point is that the DYNO must be using a certain diameter for the wheels, so that might be off a bit aswell.

Did the DYNO read the 40/60 torque split between front and rear axles correctly?
Im sure its a cumulative measurement, rather than axle specific.

Assuming audi's own measurements are at the wheel, then I'm still over reading on the both at the wheel and fly.

Ive been told that the increase in torque, and the bhp deficit will be evening the values, i.e, the increase in torque is cancelling out the bhp deficit... True?
 

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Dyno Values

I was thinking more about the values reported from the dyno....

to get that much higher torque and almost 25% lower in power just seems unlikely to me. I can't imagine any amount of "bedding the Engine in" would give you 20%+ more power, nor any special fuel would give you such a large % increase in torque. Even if the turbos were giving more boost than advertised, its unlikely that this would show up just in torque and not the power output.

I wonder if there is a simple explanation.... is it possible that the Dyno operator put in the wrong conversion values for the wrong A5 model? maybe they used gear ratio's and other parameters for the A5 V6 3.2 vs. the A5 3.0TDI? or possibly the V8 S5?

Another explanation could be that they are using 50/50 F/R axle torque split which is common to almost all Audi except for the latest B8 platform.

Might be worth a call to the Dyno operator to check?

Well, hope this helps - either way I am sure there is nothing wrong with your Engine.

BTW I think the Torque from the turbo diesels is great and results in overall better acceleration in practical situations. We can't use them here in SO Cal because we don't have the ultra low Sulphur fuels, using the diesel fuel here would damage the particulate filters (costly). Shell are just thinking about intoducing the new fuels, but its not going to happen in a hurry. Shame... the penny hasnt dropped on Economy + performance with this Engine technology here yet....
 

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This is really interesting. I have no engineering background to lean on but I have to say Rab that you're being remarkably sanguine about a 'missing' ~60BHP! As SDS5 suggests, in these days of finer production tolerances, the 'running-in' period is more about a bit of mechanical sympathy for an untried powertrain than getting the components to begin doing their proper job over time. I can't see that 240 figure miraculously appearing over the new few thousand miles.

As I say, I'm mechanically challenged but I'd be straight back to Audi with the report and demanding an explanation. But first, I'd absolutely verify the dyno test parameters again - I had my Alfa dyno'd on two different systems within the space of 4 months and they produced dramatically different results at the wheels (232 and 265) which had to be due to set-up. Since then, I've regarded dynoing as a bit of an inexact science!
 

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Discussion Starter · #7 ·
Hmm, thanx for the info guys. I'll give the operator a call on monday.

The only problem I have with reporting this to Audi is that the car is leased, and probably shouldn't be put on a dyno :p (at least, not without Audi Finance's approval I would imagine)

I'll maybe book it in for another test on the same dyno, to make sure they devote time to it being set up properly and have the correct values entered.

Regarding conversion values, I have no idea what they have used. They havn't done an A5 or an S5 before (and as far as we know on this forum, neither has anyone else?) However, their correction factor which they used on run 2 was 100.5%.

The problem I have with getting it onto another dyno is that there are no trustworthy Dyno operators around here. The nearest one, AVA, have a TERRIBLE cooling system... they've got a history of cars coming out of there with blown engines.

EDIT: Just noticed the A5's Power book value: [email protected] ... Higher RPM than mine was at. Wrong gear used???

Anyway, i'll try and find out some more info and report back
 

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HP at the Crank and HP at the Wheels are two different things. A dyno of power at the wheels should always be less than what is quoted in the Car specs because Audi measures bhp at the crank before any of the drivetrain components start sucking up some of the juice. A 25% loss is not uncommon. It is closer to 30% on most cars.
 

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these figures don't make any sense to me. The 240 (PS) is the crank power; there is a lot of loss before it is measured at the wheels- more for 4wd than 2wd- i would guess up to 25% loss. If the engine power is 240 PS (metric bhp) then this car is showing a loss of 22% due to the transmission/ loss between tyre and the rollers, which is not too bad, especially as max power should be at about 4,000 rpm

the figure can be affected by the amount of cooling that can be supplied to the engine, and for example if the rollers have twin contacts with each wheel this increases the friction loss.

What is clearly wrong is that the "engine power" calculation is far too close to the "at wheels" output, and oddly at a different rpm :confused: Also there is a direct relationship between torque and horsepower: Horsepower = Torque x rpm / 5252 which suggests that the bph is 185, which results in an at flywheel (engine) power of 231.6, which converted to the metric PS is 236, close to the factory expected output, although the rpm figures still don't make sense.
 

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Guys... refer to my posts in the 'petrol vs Diesel' thread and the 'what does bhp mean?' threads... I just got back from the pub, so too pissed ('drunk' for you US guys!) to search and paste the links here...

...However Fraser makes some good points and his calcs are correct... let's remember that Torque will be affected by frictional losses and BHP (power) will be affected by this and by inertia in the transmission... The relationship between BHP and torque involves RPM, so peak HP will not necessarily occur at peak torque rpm.

finally, BHP at the flywheel is an impirical and 'indirect' measurement on a dyno that involves running the engine under load and then under no load to derive the mass and losses in the transmission and approximate flywheel torque.

:)
 

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not sure what this all means but im intriged.... mine isnt leased for audi so where and how much is it to stick it on the dymo???
 

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shouldnt be expensive to stick it on rollers-just need to find somewhere that is respected and trusted for decent runs.
 

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...Agree with Kenny.

Go with a referral if you can and when you get there, ensure they have suitable 'forced cooling' in other words bloody-great fans in front of the car, because the engine is designed to be working this hard whilst moving... without significant forced cooling the engine will overheat and be permanently damaged.
 

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Discussion Starter · #16 ·
not sure what this all means but im intriged.... mine isnt leased for audi so where and how much is it to stick it on the dymo???
I got mine done at Dastek in Dunfermline. Their cooling is top notch, easilly the best in the country.

Whatever you do, DO NOT go near AVA at Glasgow Airport. Your engine WILL overheat!!!
 

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star performance are in kircaldy-a wee trip from aberdeen mind you but have a good rep
 

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does anyone know how much it would be and do you have to book in advance??
 

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hi jim,

i was going to pop by and see you shortly, not sure if you remember me but im the one with the red A4 quattro, had manifold etc done at star. im over in briskoda a bit.

looking forward to seeing your results :)
 
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