997.1 C2S Dyno'd - Impressed with results!

[Gibbo205]

Hi there


Well as some of you will know I've got the X51 manifolds and radiators on my car which caused a few warranty questions to be raised but in the end Porsche agreed they are not a problem and still gave me a warranty.

As such here are the results:-




My car should be 350BHP and 290Lb/Ft stock I believe?

So 366BHP and 306Lb/Ft is a good result!


On the road the car is certainly quicker, so quick there is nothing between it and a MK2 996 GT3 upto silly speeds, I've also got some VBOX times as well:-

30-70mph - 3.4s
60-100mph - 5.4s

To compare my M3 CSL was:-
30-70mph - 3.8s
60-100mph - 5.9s

My EVO X with 410BHP / 380Lb/Ft:-
30-70mph - 3.6s
60-100mph - 5.6s


Needless to say very impressed with the performance from the car and the X51 parts very worthwhile, the tech guys at Porsche Edinburough are very helpful and may also be able to give discount as well.

In short I added:-
X51 Manifolds - £650ish
X51 Radiator Kit - £90ish
X51 Undertray - £45ish
+ Fitting!

Very happy, car runs far cooler, sounds better and the butt dyno can feel this as can the real dyno plus the VBOX too.

Edited by Gibbo205 on Wednesday 27th July 21:23

[Gibbo205]

For those who are interested the Mustang was:-

30-70mph - 2.75s
60-100mph - 4.2s

Though it was 577BHP.

[Magic919]

Bit meaningless without a before run on that dyno.

[Gibbo205]

Magic919 said:

Bit meaningless without a before run on that dyno.

True but 25 cars ran that day and results seemed quite consistent and accurate.

[gt3nor]

29% drivetrain loss? Really?
Where does this number come from?

I can easily belive the 257rwhp, but would like to know where the conversion factor giving 362hp on the engine is coming from.

[Gibbo205]

gt3nor said:

29% drivetrain loss? Really?
Where does this number come from?

I can easily belive the 257rwhp, but would like to know where the conversion factor giving 362hp on the engine is coming from.

Its a Maha dyno which uses two contact patches, which results in very low wheel power figures, supposedly this configuration of dyno gives more accurate flywheel figures.

A full explanation is available here:-
http://forums.vwvortex.com/showthread.php?3965266-...

In short:-
[i]First thing we learned about using the MaHa lps 3000
Is… forgetting everything you learned about all other wheel power calculating dynos. This is what we had to do, Joe and I have been using other dynos for years to tune and test cars and we put up some resistance at first until we unlearned what we had gotten so used to.

Other dynos can only give you wheel power #s. and this is ok if all your going to do Is look for the gain from a modification compared to stock, and you don’t need or care to know what the real power is. The wheel numbers are completely arbitrary.

One of the most common miscalculations in determining horse power was guessing the drive train loss.
Most people think that there car has a certain percentage of drive train loss, in fact drive train loss is not one set percentage its multiplication, the most common example is a person that has had there car dynoed at a shop with a DynoDynamics or a Dynojet or other simalar, will say something like… my car dynoed at 280 whp and the dyno operator told me my car is approximately 25% drive train loss, so my car must have 350hp at the crank.
First question we usually ask is At what RPM. if your peak HP is at 5000 RPM then you drive train loss is much less than it is at 7000RPM so for example lets say your drive train loss is 65 hp at 5000 rpm and it is 80 at 7000RPM then you have to know what the loss is at the exact RPM that you are making your max HP, or your #s are again completely arbitrary. And with all the different wheels brakes, light weight drive lines, even tires,,.. with out the ability to dyno you driveling you have no way of knowing what your real Hp # is.
This is why we have no question about high or low reading dyno we can always throw a stock car on and compare it to the factory SAE #s
A stock e46 M3 will put between 332 and 334 crank horse power on the MaHa dyno all day, factory #s 333.0 Hp, YES its that accurate.[/i]


Like I say on the day there were stock cars making bang on their figures. This is not a wheel power dyno, its a maha dyno designed for calculating real power and not just plucking a number/percentage out of the air for transmission loss.

[drmark]

But, surely it can only measure power at the wheels, like all dynos, and guesstimate the rest no matter how clever it is - and your wheel bhp looks low to me. Me no understand.....what am I missing?

[Gibbo205]

drmark said:

But, surely it can only measure power at the wheels, like all dynos, and guesstimate the rest no matter how clever it is - and your wheel bhp looks low to me. Me no understand.....what am I missing?

Do some reading up on Maha dyno's and hopefully you will understand better, I am not a dyno expert but there are different types of dyno's and they will all give different results.

Most dyno's give you a wheel figure, but can't give you a flywheel figure, the operator just takes a good guess at what transmission losses might be.

The Maha dyno does not take any guesses it uses coastdown to calculate the flywheel BHP accurately.

For example I ran my Mustang on this very same dyno, it made 577BHP flywheel BHP and its wheel figure was some very low in the region of 350BHP, yet other dyno's had shown the true wheel power to be 460-480BHP which was about right as no car has 50% transmission losses.

Put it this way Porsche, Audi and several other manufacturers use Maha dyno's because of how precise they are, or so the internet says.

Edited by Gibbo205 on Wednesday 27th July 23:01

Edited by Gibbo205 on Wednesday 27th July 23:02

[Gibbo205]

More info found on Maha dyno:-

Transmission losses are a factor that will increase with power increase. The more power you have, the more you will loose, it is not a fixed figure. if you have 100 WHP and are loosing 20 through the transmission, then if you tune the engine, the losses will increase with the additional power, as it is a percentage of the power that you loose. Some 4WD systems, such as quatro, will loose more power, the faster you go, to the point that the car is loosing half of its power through losses.

The MAHA will measure losses when you dip the clutch (accurately), and will continue to extrapolate as the vehicle slows down, even if Neutral is selected after the measurement has started, in order that you don't burn out the clutch release bearing!, It is important that the measurement is taken while the vehicle is "in-gear", otherwise you inly measure to the gearbox, not to the flywheel!

As an experiment, test ine vehicle with two or three sets of Roadwheels (fefferent rolling Diameters), on a MAHA, you will get differing wheel figures, but always the same flywheel! Try it on a DD, and you can increase the flywheel figure by fitting smaller wheels! This is because DD measure a wheel figure, add a set percentage to Guess the flywheel!

TRY IT :-)

(DD = DynoDynamics Dyno)

[OdramaSwimLaden]

OT; It makes the Lotus Carton's 30-70mph time look all the more impressive - 3.7 seconds. Not bad for a 4 door back in 1992!!

[Slippydiff]

This is what's required to measure Hp and torque accurately








No transmission losses, no BS, and the ability to put an engine under load for as long as you like to map it correctly.

Regrettably there's a downside, that being it means removing your engine and hooking it up to Schencks finest. This is Rufs BTW. (MAHA do them as well)

[HarryW]

OdramaSwimLaden said:

OT; It makes the Lotus Carton's 30-70mph time look all the more impressive - 3.7 seconds. Not bad for a 4 door back in 1992!!

or 3.1s for a 1996 4.2 cerbera, v impressive at the time and still impressive today........

RE Maha and DD so long as you understand the differences it really doesn't matter.

[thegoose]

Gibbo205 said:

Most dyno's give you a wheel figure, but can't give you a flywheel figure, the operator just takes a good guess at what transmission losses might be.

The Maha dyno does not take any guesses it uses coastdown to calculate the flywheel BHP accurately.

I'm no expert on dynos but every one I've been on (6 in total I think) used coastdown to calculate transmission loss accurately.

Any additional drag on coastdown means a bigger measured loss, which when added to the measured wheel hp gives a much higher calculated flywheel hp. So anything dragging on the rollers under deceleration that didn't drag under acceleration will do that (I've had to have anti-roll bars removed for dyno testing so they didn't drag), so a high figure can easily be falsified (for example by lightly pressing the brake pedal on coastdown).

I was also rather surprised to see such a high measured loss from your car. I know it's somewhat different but the measured figure from my 964 was 22kW.

To digress slightly.....Sadly from 2008/9 reg's were changed (as a result of power testing irregularities in 2008) to specify a loss figure for each model to be added to the wheel hp measured on the championship's nominated dyno and for my car it was 30kW...so we had to de-tune the car so that when 30kW was added to the wheel figure the total would be within what was allowed.


Anyway, back on track - 78.4 kW loss for your car seems like an awful lot.

[BertBert]

looks pretty close to 25% all the way till it runs out of puff to me!

It's well known that using a RR with coastdown (like Marcus, never used one that doesn't do this) to measure a car against published figures is complete pie in the sky. You certainly can't conclude anything about the effects of you mods I'm afraid.

Did they really do a run with oil temp at 24 degrees? I presume not.

Bert

[Gibbo205]

BertBert said:

looks pretty close to 25% all the way till it runs out of puff to me!

It's well known that using a RR with coastdown (like Marcus, never used one that doesn't do this) to measure a car against published figures is complete pie in the sky. You certainly can't conclude anything about the effects of you mods I'm afraid.

Did they really do a run with oil temp at 24 degrees? I presume not.

Bert

As mentioned you ignore wheel figures that a Maha dyno gives, as that figure is completely not accurate.

Like I said that same dyno said my Mustang only had 350 at the wheels wheras a DD showed my car to have 460+ at the wheels.

No the oil temp was not 24 degrees, car was upto temperature, for power runs they don't connect everything up, suspect they would if tuning though.

I suspect if I plonked the car on a DD the wheel figure would be 320ish as thats a dyno designed to give wheel power, wheras a Maha is not and as such the wheel power figure from a Maha dyno should be ignored.

[Gibbo205]

Here is an E39 M5 which ran:-




Again such a car has a lot more wheel power, the Maha dyno wheel figures are miles out and should be ignored as the dyno is designed to give accurate flywheel figures.

If you want wheel figures you use a DD or Mustang dyno.

Its not hard to realise the Maha's wheels figures are pointless because if that was the true wheel power then every car was running massively under stock power, which is simply not the case.

[pete]

I concur - abnormally high transmission losses. I had both of my old TVRs on various dynos and they all used coast down to measure transmission losses. Both Griff and Tuscan were between 15-20%, varying slightly by dyno, and that's for a conventional manual, RWD, LSD drivetrain. Can't see why the Porsche rear engine layout would dramatically change that; if anything I'd expect lower losses without a long prop shaft and the joints it entails.

Anyway, it just shows you can't compare against different dynos, and certainly not against stock engine dyno figures. Way too many variables!

Pete

Edited by pete on Thursday 28th July 08:32

[Magic919]

Gibbo205 said:

... the Maha dyno wheel figures are miles out and should be ignored as the dyno is designed to give accurate flywheel figures.

So the Maha measures power at the wheels, but produces highly inaccurate wheel figures. It then uses these same inaccurate figures, plus coastdown measurements, to produce highly accurate flywheel guesses. Wow, I guess it's not a science these days.

[BertBert]

Gibbo205 said:

Its not hard to realise the Maha's wheels figures are pointless because if that was the true wheel power then every car was running massively under stock power, which is simply not the case.

I'm sorry, but you really don't understand the world of rolling roads. The type of dyno that a maha is measures power at the wheels on the way up and measures losses on the way down. Then adds the one to the other to give its bhp. As the previous poster said, they really both need to be accurate to get an accurate answer. And to the extent that rolling roads are accurate (cue big debate), they both are.

However, they are not accurate enough to do a run, compare with manufacturer figures and get depressed or elated.

Been there, made the same mistake, moved on
Bert

[EvoSlayer]

Gibbo205 said:

I've also got some VBOX times as well:-

30-70mph - 3.4s
60-100mph - 5.4s

Imo the timed runs are the best measure of any performance gains, dyno results will always be a topic of massive debate and largely ridiculed. How do these times compare to those published for the standard car, or better still did you get any timed runs in prior to your mods?