RE: 500hp Cayman GT4!

Author
Discussion

anonymous-user

53 months

Wednesday 2nd January 2019
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anonymous said:
[redacted]
(my bold)

No it doesn't. It's an N/A engine, it makes, what it makes, end of. Sure, on turbo engines, you can see more than the homologated power transiently, if boundary conditions differ (ie colder air, 1st run of the day with a cold engine etc etc) but N/A engines make what they make. The ONLY reason you hear people say "car x, y or z must make more that they claim" is usually because that car has just beaten their "1 million" PHP (Pub HorsePower) tuner car, and if their car makes a million horses, then to beat it, the OE car must make 1million and ten eh...........

BrassMan

1,482 posts

188 months

Wednesday 2nd January 2019
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IanJ9375 said:
J4CKO said:
Arent the LS conversions no heavier than the normal flat 6 engine ?

there is an impression that American V8 engines are heavy old boat anchors, they may have been in the past but nowadays they are fairly light for the power they offer.
The last conversion I read the LS V8 was lighter than the pork that came out, so yes you're right
AIUI, flat engines are good for getting the weight down low, although they get in the way of underfloor aerodynamics. Putting in a taller engine just ahead of the rear axle may (or may not) nerf the balance?

anonymous-user

53 months

Wednesday 2nd January 2019
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anonymous said:
[redacted]
You can't because it isn't!

Porsche did not spend millions designing and developing every single last watt out of that engine (and i personally know quite a few of the development team who worked on it) for them to just then go "ahh F**K it, lets just claim it makes 25bhp less than it does"

The reason you can't "prove" anything is because the proof already exists, ie the engine is certified to UNECE R85, and the power it makes, is the power claimed, and PROVEN by that certification.

If you have an EU type approved engine dyno, then please feel free to re run that engine to satisfy yourself!



samoht

5,633 posts

145 months

Wednesday 2nd January 2019
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Max_Torque said:
Lol, gotta love those Americans for making up power numbers!


488 bhp from 4.25 litres at 8k rpm (114 bhp/litre) is 435Nm (102Nm/litre) which is 12.9 Bar BMEP.

This is juuust about achievable and is broadly in line with what Porsche themselves make on their GT-3 engine (GT3 4.0 is 493 bhp at 8250 rpm, with the extra 250 rpm giving them a small edge in terms of specific output)


But the absolutely ridiculous 561 bhp figure (132bhp/litre & 118 Nm/litre - 14.8 bar), er nope, not a chance (unless they've got a turbo or two hidden away somewhere..........)
Good point, the figure of 561hp appears to be noticeably beyond the state of the art. It also seems to be a journalist extrapolation, not a claim made by DeMan themselves. The below shows the car on a hub dyno, so perhaps a ~9% drivetrain loss might be more applicable than the 15% R&T supposed?
https://youtu.be/kcR3Mq7utbE

bigmowley

1,875 posts

175 months

Wednesday 2nd January 2019
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Not sure about the "awesome track weapon" bit. The extra grunt will take a lot of extra cooling both engine and gearbox, i.e. More weight and complexity. Brakes might be just about man enough for the job, the standard car is fabulous in the brakes department, but the chassis balance and electronics will need a bit of fine tuning as well. Not sure what the gearbox and clutch will be like with that extra torque as well. Probably add another £10K to the bill to bring it all up to a reliable track spec. Might well be a case of more is less given how beautifully balanced and nuanced a standard car is on track.

sideways sid

1,371 posts

214 months

Wednesday 2nd January 2019
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bigmowley said:
Not sure about the "awesome track weapon" bit. The extra grunt will take a lot of extra cooling both engine and gearbox, i.e. More weight and complexity. Brakes might be just about man enough for the job, the standard car is fabulous in the brakes department, but the chassis balance and electronics will need a bit of fine tuning as well. Not sure what the gearbox and clutch will be like with that extra torque as well. Probably add another £10K to the bill to bring it all up to a reliable track spec. Might well be a case of more is less given how beautifully balanced and nuanced a standard car is on track.
Just out of curiousity, one wonders what these guys could do with a standard 6-cylinder Cayman engine, in terms of making it slightly more powerful and higher-revving.

Obviously not the power in their 4.25 litre GT4, but potentially the perfect Cayman without overloading drivetrain, brakes, cooling systems etc?

MDMA .

8,849 posts

100 months

Wednesday 2nd January 2019
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Max_Torque said:
Lol, gotta love those Americans for making up power numbers!


488 bhp from 4.25 litres at 8k rpm (114 bhp/litre) is 435Nm (102Nm/litre) which is 12.9 Bar BMEP.

This is juuust about achievable and is broadly in line with what Porsche themselves make on their GT-3 engine (GT3 4.0 is 493 bhp at 8250 rpm, with the extra 250 rpm giving them a small edge in terms of specific output)


But the absolutely ridiculous 561 bhp figure (132bhp/litre & 118 Nm/litre - 14.8 bar), er nope, not a chance (unless they've got a turbo or two hidden away somewhere..........)
Doesn't a 458 Speciale make 597bhp from a 4.5L NA V8 which is the same 132bhp/litre ?


Edited by MDMA . on Wednesday 2nd January 18:59

Twincharged

1,851 posts

204 months

Wednesday 2nd January 2019
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Max_Torque said:
You can't because it isn't!

Porsche did not spend millions designing and developing every single last watt out of that engine (and i personally know quite a few of the development team who worked on it) for them to just then go "ahh F**K it, lets just claim it makes 25bhp less than it does"

The reason you can't "prove" anything is because the proof already exists, ie the engine is certified to UNECE R85, and the power it makes, is the power claimed, and PROVEN by that certification.

If you have an EU type approved engine dyno, then please feel free to re run that engine to satisfy yourself!
Do you suppose that Porsche may, like every manufacturer of anything on earth, have a tolerance within which engine components (and therefore complete engines) are produced? And that this might therefore mean that there is a tolerance band for the power output of the engines too?

Considering that tolerance band, do you think Porsche might decide to quote the lower end of it, to avoid any customer who dyno's their engine from being disappointed?

kambites

67,460 posts

220 months

Wednesday 2nd January 2019
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MDMA . said:
Doesn't a 458 Speciale make 597bhp from a 4.5L NA V8 which is the same 132bhp/litre ?
Yes but it revs to 9000rpm. 130bhp/litre at 9000rpm is hardly easy to achieve but it's within the bounds of what's realisticaly possible from a naturally aspirated four-stroke pretrol engine. 130bhp/litre at 8000rpm is a very different matter.

I suppose strictly speaking the article doens't say anything about it running on petrol.

Edited by kambites on Wednesday 2nd January 19:30

anonymous-user

53 months

Wednesday 2nd January 2019
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MDMA . said:
Doesn't a 458 Speciale make 597bhp from a 4.5L NA V8 which is the same 132bhp/litre ?
Of course. And 132bhp/litre is no where near the N/A limits. For example a 3.0 Formula 1 V10 engine makes over 900 bhp (300 bhp/litre). And how do they do that you ask, and the answer is REVS, and lots of them. The 458 makes peak power at 9000 rpm, vs the claimed power of this GT4 at 'just' 8000 rpm.

And guess what, 132 x (9000/8000) is 117.......


That's the thing about N/A engines, they are actually very predictable, because you only have atmospheric pressure to push air into the engine, and you only have atmospheric air density to supply the oxygen. All N/A engine scale pretty much with capacity and revs, which is why i know this GT4 engine DOES NOT make over 500bhp.....


(it's also worth noting, to the people saying the manufacturers are sandbagging on their power cert tests, how are they doing this then? The test must be done with the production engine calibration, and checks are made for wideopen throttle, and the fuel used is specifically tested and rated, and the eventual power output is normalised to a standard day to allow comparison across engine types (and there are limits for humidity, temperature and pressure, which must be met or the test is void). On top of all that, once you have done your power cert, you have to then pass conformity of production tests. Sure, these have a slightly higher acceptance window (typically 5% max) but no one is going to use that window to up or down rate their power cert, because you need to be in the middle of that window precisely to allow for small production variations. Of course, the manufacturer could cheat, but ime, whilst a few small tweeks that fall into grey areas might be used, that might make a bhp here or there difference, no one is blatantly up or down rating their N/A engine to the tune of 10's, 20's or even 50's of bhp.)



stevesingo

4,848 posts

221 months

Wednesday 2nd January 2019
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It is and interesting read: http://www.unece.org/fileadmin/DAM/trans/main/wp29...

I'm with Max_Torque on this one. The above document is excruciatingly prescriptive in how the test is conducted. If a manufacturer could make more power in the test, they would and they would market that number.

What is possible closer to the truth is some manufacturers may "select" engines with favourable tolerances for submission to the teat. The bulk of that manufacturer's engine may well seem to under perform.

Dynapac dyno's are not in any way comparable to what manufacturers use. They measure water pressure generated by a pump on the hub and extrapolate the torque data from there. What could possibly go wrong with such a system?


BubblesNW

1,710 posts

182 months

Wednesday 2nd January 2019
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sideways sid said:
Just out of curiousity, one wonders what these guys could do with a standard 6-cylinder Cayman engine, in terms of making it slightly more powerful and higher-revving.

Obviously not the power in their 4.25 litre GT4, but potentially the perfect Cayman without overloading drivetrain, brakes, cooling systems etc?
Not the same people but the best Europe has to offer, 440bhp and 470Nmat the wheels using the standard 3.8 litre block and a few choice mods to the exhaust, headers and tuning

https://youtu.be/94P6COIXTHM

Not sure if anyone has gone the whole hog in the U.K. but there are a few cars here that Jens has worked on.

Deep

2,061 posts

242 months

Wednesday 2nd January 2019
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anonymous said:
[redacted]
With respect, you are conflating mileage with major modifications. I use mine (not a GT car) everyday and don't give a damn what the mileage does to the value. I bought it to drive and enjoy and I intend to do so.

However would I modify it so that the value falls through the floor and I lose my warranty? No way.
In addition I don't have the time nor inclination chasing a 'small' aftermarket tuner for a warranty claim. If the engine, gearbox etc let go I need to know I can just hand the keys over to an OPC and wait for the call to tell me it is fixed.


ChrisW.

6,209 posts

254 months

Wednesday 2nd January 2019
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BubblesNW said:
Not the same people but the best Europe has to offer, 440bhp and 470Nmat the wheels using the standard 3.8 litre block and a few choice mods to the exhaust, headers and tuning

https://youtu.be/94P6COIXTHM

Not sure if anyone has gone the whole hog in the U.K. but there are a few cars here that Jens has worked on.
Although noise is also becoming a very serious consideration ...

I could be very interested in tuning mine to X51 spec but I would basking for less noise ... rather than more ... is this possible ?

stevesingo

4,848 posts

221 months

Thursday 3rd January 2019
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BubblesNW said:
Not the same people but the best Europe has to offer, 440bhp and 470Nmat the wheels using the standard 3.8 litre block and a few choice mods to the exhaust, headers and tuning

https://youtu.be/94P6COIXTHM

Not sure if anyone has gone the whole hog in the U.K. but there are a few cars here that Jens has worked on.
Not sure that is reality either. 470Nm is 338lbft. 338/3.8 is 89lbft/lt (BMEP of 15+) measured at the wheels. The last of the NA F1 engines made about 93-94lbft/lt at the flywheel.

Burwood

Original Poster:

18,709 posts

245 months

Thursday 3rd January 2019
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anonymous said:
[redacted]
Isn’t there also the psychology that it’s near as perfect from the factory. Modifying it is a bit Frankenstein.