Dyno Bullshit!!

[W8PMC]

I've had this debate until i'm blue in the face & yet it always comes full circle.

I do appreciate that some see the Dyno as god like, however being somewhat an expert in things IT, let's say that it's very easy for the Computer to say NO or YES!!.

If your car feels slow, or that it's started slowing down over time, fair enough you may have a problem that needs resolution, but all you need to ask is how does it perform in the real world, that being out on the road.

Prior to my RS4, i owned a DMS E60 M5, pushing out around 540BHP & prior to that a C5 RS6 with 560BHP & 565lbsft, however my RS4 with just a DMS map & Milltek car-back feels as fast as both those cars & is defo quicker point to point in virtually any conditions.

Now, i've never had my car on a dyno & perhaps i should out of curiosity to see if it's at 350/400 or 450BHP, however as the cars owner & driver, i know that it performs as well if not better than far more powerful machines & have no doubt it's achieving it's claimed outputs give or take.

So, is the dyno king or is it like any computer & producing either what the operator wants it to say or even what the cars owner would like to see.

Let's not kid ourselves that many many factors make a dyno plot, least of all some blokes calcualtion of the transmission losses & how to manipulate what the dyno actually says, into figures the pissing contestants want to see.

I realise this post will no doubt get flamed, but why base your opinions on a damned computer print out?? Does your car really feel really slow? as i know mine still feels like it's hitting warp speeds.

[rs4v8]

I realise this post will no doubt get flamed, but why base your opinions on a damned computer print out?? Does your car really feel really slow? as i know mine still feels like it's hitting warp speeds.

Have to agree. Find it all more than a wee bit yawnworthy. I'd rather be out driving mine than stuck in an industrial unit glued to a PC screen fretting over the numbers.

All to their own though, some folks may be into that kinda thing!!

[sonny]

I agree, how ever Iv booked my car back into SRR to a re-run (2 runs in 3 months) so at the mo I think I'm looking at the dyno as King, placebo any one lol

[W8PMC]

Wrote that whole O/P with a large quantity of Carling inside me & i can only spot one spelling mistake

To expand, i'm not criticising anyone who wants to or runs their car on a dyno, as it's i guess OK for some benchmarking & defo a fair idea if ur having tuning work done, i was just making the point that their accuracy levels are shocking, so therefore the same applies to the figures generated.

I've heard many times of 50+BHP differences between different rolling roads, big differences at different times of the day, that extra 1 degree in ambient temp could = 15BHP etc. etc.

Being what i would consider an experienced driver on road & track & having driven or owned a fair variety of powerful road cars, i see no better indicator to the cars performance than my own driving experiences.

A caveat however, i have no doubt that a very small selection of B7 RS4's as well as other marques are way down on power & would naturally warrant investigation, however i'd not be calling my lawyer due to one poor dyno plot & likewise Audi would not be waking their lawyer up.

[Andyuk911]

I liked your post .... I noted that the Dyno Dynamics's guy real job is an IT consultant...


The Dyno day was good as it provided a base line .... some cars were way down and had problems which are now being fixed by dealers(fingers crossed).

You must have missed my post asking about VMAX ... I am sure Craig would host a RS Vmax event .... ball park number on cost ?


However my ride in this car had my Dyno cheek twitching ...

[W8PMC]

Andy, the day itself looked fun & nice to see so many B7's, however as expected it raised far more questions that it did provide answers.

All but the most extreme cases would see dealers or Audi giving a toss. VARSITY was one (after a lenghty legal battle) & so far to my knowledge his was the only case.

Anyone that sees a RR day as anything other than fun/pissing contest (on that day) is not understanding the whole concept of RR's & technology, so i'd hate to see everyone under 414BHP wander into their dealer with a plot & get laughed out (which they will).

That said, a RR can show up other faults, say for instance bad timing, over fuelling, loose pipes etc. however surely in day to day driving, a driver should spot if their car has suddenly lost say 50+BHP, i know i would & i'd then be into the dealer saying my car is losing power.

If one car is hugely down on power then perhaps with ALOT of further proof someone may have a case.

I have run my B7 at VMAX many times, as i did my M5 & RS6. My trap speed in the M5 & RS6 were both higher by about 10MPH than my best in the RS4, however i've drag raced a couple of B7's & was head to head with another DMS car up to warp speed & identical trap speeds all day & quicker than 2 stock cars both off the line, drag & through the trap.

Could even up to 100MPH hold onto stock 996 Turbos.

May now plonk mine on a RR just out of curiosity, but if it said 350BHP i'd know that was bollox, as i would if it said 450BHP.

If Audi really did produce thousands of B7 RS4's & all of these were averaging 35BHP down on quoted output, i feel a class action would be top of customers lists, but i truly believe if every engine went back to the factory & was bench tested in identical conditions, the outputs would be near as damn it the same & any that were wildy adrift could no doubt be seen as faulty.

Craig would not get enough attendees to an RS specific event, as it's sometimes a struggle with the widest reach. Cost with expected RS numbers would be around £400 i'd expect, as it's getting close to £200 with a full regular. That said, it would be by far the best measure head to head & as above i've had such runs.

Nice GTR Andy, a purchase or loaner? What are they really like on the road?

[duud40]

Don`t over-estimate it man, it`s just a tool that measures power to the wheels then a human (ie source of error) can input a drive train loss coeficient and say you have xxx hp to the cranck by guestimating. In it`s right the dyno is a very accurate tool that measures horsepower to the wheels (chassis dyno, engine dynos obviously measure power at the crank). Dyno`s aren`t tools that say your car is fast or slow, it`s people that play that part. When did you ever go to a dyno and get a sheet saying : YOUR CAR IS REALLY REALLY FAST! , I guess you never did eh? As long as you keep it simple and don`t make assumptions about a car being fast or slow only by dyno figures you`re in the clear . Just go out and enjoy your beautifully balanced,quattro driven,4.2 fsi jewel .

[klauster]

completely agree, my car was at the bottom end of RR BHP list, my car goes into Audi next week as the power curve just didnt look the same as other peoples, which says to me it cant be quite right. A full service and some Audi diagnostics should show up something, which Audi have agreed to look at. If nothing is found then I'm still happy with my car.

The only thing I took from the day was that the curves on my plot, particularly at the top end of the revs was very different to other people, so maybe something isnt right...

[no_RS]

There are far too many variables in the in the dyno measurement and vehicle performance to take the numbers as absolutes and should be considered as diagnostic/development tool and to support pissing contests.

I believe the ECU's fitted to the S/RS models have an adaptive feature that optimises performance (reduces engine power) depending on previous driving style so you would need to reset this to get a true picture of engine performance.

[ghoonk]

Does it matter if an RS4 with 350 bhp still spanks a car that has more power? At the end of the day, what really matters?

[r4fdud]

the driver!

[ArthurPE]

if my dog was as ugly as the GT-R I'd shave it's arse and parade it around backwards

it's fast...but you can't outrun ugly lol

[SR71]

Prior to my RS4, i owned a DMS E60 M5, pushing out around 540BHP & prior to that a C5 RS6 with 560BHP & 565lbsft, however my RS4 with just a DMS map & Milltek car-back feels as fast as both those cars & is defo quicker point to point in virtually any conditions.

The obvious flaw in the argument is, how d'ya know what the M5/RS6 were producing?

Were they engine dynoed?

If they were only as fast as your B7 maybe they were 100hp down on your quoted figures, whereas your particular B7 was producing more than the quoted figures?

You either have faith in the dyno or you don't?! It can't apply in just some cases and not others!

I've dynoed all my previous cars (including Audi's) and they've all delivered what the manufacturer said on the tin...certainly within 5%. That might just be a statistical anomaly I agree...

But all we want to know is why the B7 typically doesn't.

Now if Audi came out and admitted that the ESP/EDL/ABS (call it what you want) is responsible for the discrepancy, fair enough.

That may also explain the variance.

One of the reasons the results are so inaccurate is that the dependent variables aren't controlled in any significant manner for the purposes of "Rolling Road" days as we enthusiasts know them.

But I'd imagine the Dyno Dynamics engineers would be pretty adamant that under properly controlled conditions, having tested a number of cars, they'd be able to deliver the algorithm that backed-up the OEM claims.

In the meantime I am quite happy with my car and its performance, but the quest for further knowledge continues.

Nobody likes being hoodwinked, and we know that Audi have hoodwinked us with the performance of their cyclonic seperator on the B7...it might as well not be there!

[ArthurPE]

dynos are limited in utility...they are good for tuning, not comparison...and definitely useless for 'crank' HP...
and Dyno Dynamics THEIRSELVES said on their website that if someone is telling you crank HP, they are full of it...
it CAN'T be determined accurately from wheel HP without having dyno'ed an engine alone and then the car, then deriving the cf from the difference...for many runs...

losses vary with rpm...period...the cf at 4000 is 1/2 of that at 8000...basically linear with rpm

the ONLY way to know crank HP is to remove the engine and dyno it...

the documented speed/times of a 4000 lb car are the best 'proof' that the RS4 makes >400 HP...
speed and time measurments are dead accurate...and the physics behind the calculations are well known, transparent and not subject to debate...

I contend the recent numbers are skewed downwards becuause the 'TN' factor is off by at least 10-12%, maybe more...
but it's a moot point...

why can't we see the raw wheel torque and the cf's used to get back to crank HP...

who tuned the top 2 HP modified cars?
would there be any reason to make sure they were the top 2?

I'd like to see the cf's for all cars...the others averaged 355 or so, the tuned cars 415...there is NO way those minor mods can give 17% more HP

Torque = V x P/4Pi
V = displacement
P = mean effective cylinder pressure ~ Cr and/or boost, na in this case
Pi = 3.14159....

HP = T x w
w = rotational speed or rpm...

so the ONLY ways to substantial (>5%) increase T is a bigger engine or more P, higher Cr or boost
if T is constant the ONLY way to increase HP is to raise the rpm's

these are irrefutable facts of engineering, not hypotheses...

[sonny]

BTW that Skyline is nice, I have changed my mind about that car lots, so come on Andy, did you "razz" it around your local vilage?