[ZuffenHouseRules]

I share this only from a perspective of engineering interest -- not saying it matters a whole lot one way or the other to our driving experience/enjoyment as 718 owners.

Quoting one of two independent tuner sites sharing baseline dyno results on stock 718 S:
"The main focus here is that the Boxster S and Cayman S are really over 400 horsepower from the factory."

My online search indicates a conservative (minimum) figure for Porsche drivetrain loss for manual/PDK dual-clutch is 15% -- that is, hp at rear wheels about 85% of engine (crank) hp at the flywheel. So both dyno tests support true horsepower around 400....

Just as an aside, substituting 400hp for the Cayman S in this comparison with current/recent Carreras of 370-409hp makes the results appear a lot more reasonable for acceleration relative to power/weight ratio (I'm pretty sure all are PDK with possible exception of the 997: fastestlaps.com doesn't provide detail on the transmission used for individual test results so some inference is required).

Some of you may recall I was intrigued by the question Thomas at Everyday Driver European posed in his video review: "how is this even possible?" (718 S Norschliefe result seeming anomaly for a 350hp/3100 lb. car). Maybe now the question is: 'would Porsche -- known for very conservative power ratings -- actually understate the 718 by as much as 12%?" And why...

But most interesting to me is simply the engineering aspect of a turbo engine with (ostensibly) 160 hp/litre specific power. Is that the result of adding a larger VTG turbo to the 150 hp/litre of the 2.0 (and Carrera GTS 3.0 TT)?

I'm interested in hearing your thoughts on this, and also some seat-of-the-pants impressions from 718 S drivers (esp. w/ track experience) -- does it feel like 400hp to you?

 

[dpcompt]

718S horsepower?

In a road test of the 718S, Automobile Magazine reached an indicated speed of 186mph and the car was still accelerating. That would suggest that the quoted HP numbers by Porsche are probably conservative.

 

[Black718]

Cobb got 340hp during their baseline dyno test before any modifications: https://www.cobbtuning.com/baseline-dyno-pulls-2017-porsche-718-boxster/

Using your 15% drivetrain loss number, that would mean crank horsepower would be exactly 400hp.

Drag strip time-to-horsepower estimators are notoriously inaccurate, but just for fun: Wallace Racing HP Calculator For 1/4 Mile

If I plug in the times from my last trip to the drag strip of 11.722 @ 117.12mpg (and assume 3300lbs for weight of car/driver/fuel) I get:
Your HP computed from your vehicle ET is 364.45 rear wheel HP and 404.95 flywheel HP.
Your HP computed from your vehicle MPH is 382.11 rear wheel HP and 424.56 flywheel HP.

So yes, I think the car has 400hp at the crank from the factory.

 

[ZuffenHouseRules]

Automobile Magazine reached an indicated speed of 186mph and the car was still accelerating

Right, I saw that, and I know top speed can be a good indicator of relative power between cars of similar Coefficient of drag (Cd), but I didn't want to introduce possible speedometer error as a variable.

Still, 186 would slot in right where you'd expect a 400hp Cayman S to fit versus the group of Carreras in the comparison. Or in this even better head-to-head -- with more data points -- versus a 991 Carrera S of same weight, same Cd, same transmission, and very close power* resulting in very close acceleration times across the spectrum.

*allowing that conservative factory power numbers apply to the 911 as well, it should be slightly higher than the 400hp 718

eta: I don't know if it shows up clearly, my reference links are embedded in the text in blue.

 

[Porsche2018]

So yes, I think the car has 400hp at the crank from the factory.

If the S is at ~400hp that would seem odd that Porsche wouldn't want to use that as a selling point. There aren't many people that would view the extra 50 hp as a negative. Even if we concede that Porsche is conservative with their numbers in general this would be an extremely conservative performance estimate.

 

[Black718]

There is an established pecking order at Porsche. The 718 isn't allowed to have more horsepower than the 911. It's all marketing.

Take a look at the quoted 0-60mph. Porsche quotes 4.0 with PDK and Sport Chrono, but the car will actually do it in 3.5 seconds.

 

[Porsche2018]

There is an established pecking order at Porsche. The 718 isn't allowed to have more horsepower than the 911. It's all marketing.

I didn't put that in the comment but that is exactly what I told my friend yesterday......that is truly my suspicion. I was trying to find the best Porsche for my taste and test drove specked out 2017 base 911 and a 2017 C2S and they didn't even come close to the power of the 2017 CS. My first inclination was if the 2017 C & CS was fast then the 911 Carrera and the C2S would be a rocket. Just the opposite after driving the 911's they felt like, well, family sports cars....no real thrill. The rockets were both the Cayman and Cayman S......that also applies I am sure to the Boxsters too...........

 

[dpcompt]

718S horsepower?

Bottom line: If you thought your 718S was very fast, you were right!

 

[photonscience]

Cobb got 340hp during their baseline dyno test before any modifications: https://www.cobbtuning.com/baseline-dyno-pulls-2017-porsche-718-boxster/

Using your 15% drivetrain loss number, that would mean crank horsepower would be exactly 400hp.

Drag strip time-to-horsepower estimators are notoriously inaccurate, but just for fun: Wallace Racing HP Calculator For 1/4 Mile

If I plug in the times from my last trip to the drag strip of 11.722 @ 117.12mpg (and assume 3300lbs for weight of car/driver/fuel) I get:
Your HP computed from your vehicle ET is 364.45 rear wheel HP and 404.95 flywheel HP.
Your HP computed from your vehicle MPH is 382.11 rear wheel HP and 424.56 flywheel HP.

So yes, I think the car has 400hp at the crank from the factory.

I'd love to see you post this on the P9 and rennlist boards and watch the heads explode >

 

[Viffermike]

I'd love to see you post this on the P9 and rennlist boards and watch the heads explode >

I doubt it would do any good. The engine could produce 600hp and be some sort of direct derivative from WEC and the Old Guard would still moan and genuflect about losing two cylinders, then cramp up into a fetal position ...

What I'm interested in is a Cobb (or otherwise) dyno test of the base 2.0. I doubt it's done it because the base motor doesn't have near the tune-ability that the 2.5 does. The 2.0 already spools up, what, 19 psi max?

 

[Black718]

Fabspeed did test the Base 718 when they compared before/after their street sport exhaust. Here is their dyno.

281.26 hp at 6.15K rpm and 269.46 torque at 4.46K rpm

stock according to Porsche is 300 hp and 280 lb-ft

 

[Viffermike]

Fabspeed did test the Base 718 when they compared before/after their street sport exhaust. Here is their dyno.

281.26 hp at 6.15K rpm and 269.46 torque at 4.46K rpm

stock according to Porsche is 300 hp and 280 lb-ft

Nice. Thanks for this. It does appear that Porsche underestimates the 2.0 at the crank, too.

 

[Porsche2018]

I think you guys will appreciate this but I drove the car 200 miles around the Austin area, and when people see and hear me coming they pull to one side.....not quite Autobahn Royalty but maybe, just maybe, Texas Royalty..........This car is a rocket plain and simple..........>. When you hit the gas it slams you back.....now that's my idea of fun! I got the car up to 110mph in no time and prayed the local police were not lurking......big smile.

 

[ZuffenHouseRules]

I've been referencing 718S to 911 Carrera acceleration times because it's more nearly a like-to-like comparison: same PDK and electronic launch control, similar Cd/frontal area, similar weight....and overall just very close members of the same family. I surely didn't mean to diminish the 911 results, hope I didn't give that impresson. To the contrary I'm holding them up as the ultimate standard for power and speed in a Porsche that the lower-cost mid-engine platform could aspire to.

Porsche 911 Carrera GTS vs Porsche 911 Carrera S vs Porsche 911 Carrera vs Porsche 718 Cayman S - FastestLaps.com
Porsche 911 Carrera S vs Porsche 718 Cayman S - FastestLaps.com

Very fast company to run with, irrespective of factory hp rating....

 

[Viffermike]

I think you guys will appreciate this but I drove the car 200 miles around the Austin area, and when people see and hear me coming they pull to one side.....not quite Autobahn Royalty but maybe, just maybe, Texas Royalty..........This car is a rocket plain and simple..........>. When you hit the gas it slams you back.....now that's my idea of fun! I got the car up to 110mph in no time and prayed the local police were not lurking......big smile.

Funny: So far, I've gotten a few looks but not much in the way of out-and-out gawking. (Then again, this is Dallas we're talking about.) We'll see what happens this weekend when I put a couple hundred more miles on Alli.
@Porsche2018 , It's the color. Has to be the color. >

 

[Black718]

does it feel like 400hp to you?

Sorry I can't reply to your private message. I don't have enough posts.

Yes, I was a few tenths faster than the magazines with my quarter mile time. Remember that I was on a prepped drag strip surface 59 feet above sea level (Bradenton Motorsports Park).

The car's time did surprise folks and it's actually a Boxster S, not a Cayman S.

 

[GregW]

I'm wondering about all of this. I am also very happy with the 'seat of the pants' feel and don't really care--but I am curious.

According to Porsche any engine that produces under, or more than a limited amount of hp over the standard is rejected, torn down and inspected to find out what happened.

The net hp ratings are said to be produced according to ece-r85, which states (among many things): No data shall be taken until torque, speed and temperatures have been maintained substantially constant for at least one minute. This is mandated as a full throttle test.

So, questions:
What is Porsche's internal standard? Is it the same as the published figures?
What happens to an engine's production when run at full throttle for more than a minute?
Can an engine produce more hp & torque during a short burst (typical dyno run) than the sustained production tested? (I know that stereo amplifiers sure can.)
If the real figures are substantially above the published ones--Why?

Greg

 

[dpcompt]

718S more powerful than published

I'm wondering about all of this. I am also very happy with the 'seat of the pants' feel and don't really care--but I am curious.

According to Porsche any engine that produces under, or more than a limited amount of hp over the standard is rejected, torn down and inspected to find out what happened.

The net hp ratings are said to be produced according to ece-r85, which states (among many things): No data shall be taken until torque, speed and temperatures have been maintained substantially constant for at least one minute. This is mandated as a full throttle test.

So, questions:
What is Porsche's internal standard? Is it the same as the published figures?
What happens to an engine's production when run at full throttle for more than a minute?
Can an engine produce more hp & torque during a short burst (typical dyno run) than the sustained production tested? (I know that stereo amplifiers sure can.)
If the real figures are substantially above the published ones--Why?

Greg

I can think of two reasons for this:
The old theory that the Cayman should be the sister/child to the venerable 911
And, maybe Porsche fearing backlash from the 6 cylinder aficionados, made the new 4 even faster than was advertised to make test drives a little more rewarding.
I actually like the sound of the new engine. It reminds of V-8's from the past, throaty and torquey.
I don't like slow cars that sound great.

 

[ZuffenHouseRules]

For me this comes down to two equally hard-to-believe alternatives:

1. Porsche is knowingly 'sandbagging' 718 power ratings for their own reasons (which we can only speculate upon).

2. 718 S is a true 350hp car that somehow posts independent acceleration times in line with 400+hp PDK-equipped 911s (incl. a quarter-mile run by one of our own forum members); and makes dyno readings at the rear wheels in line with 400 crank hp calculated (as reported separately by two independent tuners).

??????

 

[GregW]

<snip>I actually like the sound of the new engine. It reminds of V-8's from the past, throaty and torquey.
I don't like slow cars that sound great.

I've said it before, and I'll undoubtedly say it again, but this time I'll just agree with your first point.

I don't mind slow cars that sound great--and they can be cheap to produce, and a great sound is a great sound. What I don't accept is that loud=great.

Greg