surquhar

Yes you are right.

randr

As I said previously, its about understanding the starting point.

(1) If you don't dyno the car before modifications on the same dyno you have no idea if the number after modification is real or meaningful.

Its that simple. . There is no mystery. Or you can use something like a MAHA dyno which can produce precise and accurate results. Tuners don't like them because they are very expensive.

also and as I said previously

(2) If you get a replacement crate engine for a GT3 - that engine will have a result from Porsche with the paperwork

(3) Porsche release engines within a narrow tolerance band

(4) Sport Auto (a very highly respected magazine) reports MAHA dyno results for a wide range of Porsche sports cars and others.

(5) Moreover, they bothered to look into the detail and found that a "happy" result for a TTS was way off beam. They went and did three cross checks on three other MAHA dynos and found the initial error was due to the use of inappropriate corrections for these cars.

(6) If you want a reasonable discussion about modifications, what works and what doesn't work. You need accurate and precise information or at worst inaccurate but reproducable information from the same dyno. Without this its all smoke and mirrors.

(7) I wasn't "calling anyone out" - I was pointing out what the real starting point for this series is.

(8) Why would I want to or need to dyno my X51, there is no point - its a manufacturer modification - a turbo swap and whole system remap - it does what it says on the box.

P-car fan

That's a huge improvement over stock if your baseline would have been similar to the Cobb dyno runs!

Are the O2 spacers continuing to eliminate any CEL's? How's the exhaust smell without the cats?

erko1905

This is kinda surprising; I always thought you had to pair a hardware change like this with an appropriate tune - your results imply that your stock ECU adapted to not having the cats and car is putting down more power accordingly, making use of your new hardware, so the ECU self-tuned in a way? Pretty impressive if so

sticky

Randr, this is the second time now you are claiming someone else's dyno runs to be inaccurate. You are spreading misinformation.

The dyno run in the OP is accurate you simply do not understand that it is a Dynojet he is using. We already went over this and I attempted to explain it you in very basic terms.

I sent you an article that explains exactly why dyno's differ and how a Dynojet in particular operates compared to other dynos: http://www.****************/content.p...an-vary-wildly

I see you did not read it. It is very insulting for you to claim ///m3thod's run is inaccurate as well as runs by others.

The MAHA is simply reading conservatively. The 991.2 does not have 19% drivetrain losses which is what 362 whp compared to a 450 hp crank rating would tell you.

Additionally, Porsche does in fact underrate certain engines. How do you explain the 991.2 Carrera trapping 7 miles per hour higher despite 'only' an increase of 20 horsepower on paper? Are Porsche horses taking steroids?

991.1 Carrera

DISPLACEMENT: 210 cu in, 3436 cc
POWER: 350 hp @ 7400 rpm
TORQUE: 287 lb-ft @ 5600 rpm
Standing ¼-mile: 12.9 sec @ 111 mph

991.2 Carrera

DISPLACEMENT: 182 cu in, 2981 cc
POWER: 370 hp @ 6500 rpm
TORQUE: 331 lb-ft @ 1700 rpm
Standing ¼-mile: 11.9 sec @ 118 mph

Your argument is Porsche does not underrate the motors and that all dyno's othe than the MAHA are wrong. Well then, why do my own dyno tests support the real world performance difference? How do you explain the dyno results lining up exactly with what you see?

A Dynojet is an inertia based dyno (you would know this if you read the article I linked you to) which means it measures how quickly a drum of a set weight is spun. Compared to load bearing dynos (like a MAHA) it reads higher. That does not mean it is inaccurate. It means it is different.

Please read about different dynos and do not discount the testing others do especially when you have done none of your own and do not understand how different machines operate.

sticky

He seems to think that because a MAHA says 362 whp that means all dynos should show 362 whp. It's a basic fallacy.

If your Carrera reads 355 on a Dynojet and 340 on a Mustang the horsepower of the car didn't change it is simply the reading of the dyno that did because it's a different machine.

Where is the OP supposed to go find a MAHA? He's not in Europe. I'm not in Europe. You're not in Europe. We do not need a MAHA anyway. I wouldn't want to use one due to how few runs there are to compare to Dynojet and Mustang graphs.

It is wrong for him to call the testing of others inaccurate though. He should appreciate the data and read about the subject so he can better understand it rather than dismiss everyone else outright.

sticky

Exactly this.

I'm ordering a set of cat bypass pipes myself to test as I have a baseline and I will show the overlay as soon as Soul gets back to me.

randr

No sticky - I'm not posting false information. I'm pointing out what each of this series puts down in stock form, both at the wheel and at the crank.

The Sport Auto articles are factual and the data is reproducible.

I am fully aware there is some variance from the factory however this is very tightly controlled by Porsche.

You need to understand the distinction between accuracy and precision and also understand the actual difference in performance between the .1 base and .2 base as power calculated under the curve. Which is significant.

This is why the performance of the .2s is so far ahead of the .1s - because of the large difference in total power under the curve created by the presence of low end and mid range torque.

I wont even bother to address this particular comment - However, I did find it very amusing.

sticky

You're hung up on Sport Auto for some reason as if they are the only people who can dyno a car on the planet. I don't know why you can't process there are different dyno machines.

I have personally utilized three different dynamometers with the same car. Each showed different peak horsepower yet the curve shape was similar. Why? Did my hp change on each machine or how it was read?

I'm not talking about factory variance but Porsche underrating 991.2 output. Would you kindly explain how the '370' hp 991.2 base is beating the 991.1 GTS in a drag race? Have you read this which explains it? http://www.****************/content.p...orsche-history

You say it is area under the curve. True. But horsepower is torque X rpm / 5252. The 991.2 has more torque AND more power.

Need evidence? Here:

Stock 991.1 Carrera:



Stock 991.2 Carrera:



Not 20 hp. 75+ hp and more area under the curve. Works out exactly to a 7 mph increase in trap speed. Why is the dyno 100% accurate here?

I find it amusing you still didn't read the dyno article I linked you to. I can lead you to water but I can't make you drink it. You would do yourself and the forum a huge service if you educated yourself on the topic.

Ed911.2

Fascinating discussion. Could do without the ad hominem, though.

As a relative novice in this department, I would have thought the power curve as delivered to the wheels was the most important thing; after all, that’s what makes the car move? Who cares what’s going on at the end of the crank or in the middle of the gearbox?

There are many ways to measure power/torque with high accuracy. If tested under the same conditions, there is only one correct set of data and I’d have thought the dyno which gets closest to these numbers would be the best?

randr

Sticky, from 4000rpm to redline the 991.1 GTS makes 340HP under the curve. The 991.2 base makes 330HP under the curve - so any drag race should be very close. Note the GTS will likely have slightly higher losses.

Car and Driver 991.1 GTS 11.9 @ 118 (https://www.caranddriver.com/reviews...ra-test-review)
Car and Driver 991.2 Base 11.9 @ 118 . (https://www.caranddriver.com/compari...e-specs-page-5)

If you look at - to speed or in gear acceleration the base 991.2 is every bit the equal of the outgoing GTS

0-60mph, 3.4s base/ 0-60, 3.6s 991.1GTS
to 100mph, 8.5s/ 8.5s
to 130mph, 14.8s/ 14.6s
5-60mph, 4.3s/ 4.2s
30-50mph, 2.6s/ 2.7s
50-70mph, 2.8s/ 2.8s

I really don't think its a mystery but I do think its fantastic Porsche produced such a good engine with so much head room.

In some respects its easy to see why the 991.1 guys get so riled. The usual Porsche scenario is the .1GTS is ~ .2S and the .1S is ~ .2 base. What happened here, in terms of performance, is the .1 GTS ~ .2 base.

sticky

So you're going by the graphs I posted?

Exactly my point. The 991.2 base at 370 matches the 991.1 GTS at 430? Someone is lying. By the way, torque isn't what you want for trap speed. If it was diesels would rule the performance landscape.

I haven't seen any MAHA graphs to back up your claims showing a 350 whp 991.2 S or 300 whp 991.2 base.

Regardless, you still don't understand how dynos differ...

randr

No, I'm calculating everything from the published engine curves then integrating the areas under the curves to give a HP value "under the curve" from 4000rpm to redline (or basically calculating how much engine HP is realistically on tap as you punch through the gears).

sticky

So you're a dyno?

randr

You can do the same calculations for any data. It will only have meaning if the data is accurate.

Thats why I use the engine curves published by Porsche as the starting point.