Didn't see this posted here, and seems like people would be interested to see these results from BGB. @BGB Motorsports let us know if you have anything else to add to this convo.

What this kind of shows is Porsche gave the 718 GT4 road car 718 Clubsport performance for the road (note 100 cell cats on Clubsport + 98 Octane). Add mods like Cobb OTS tune + free up a little flow, and you're equal.

If the upcharge for the 718 GT4 is GT3RS suspension components (improved rear end stability vs. 981), 4.0L / X-51 level engine power, significant aero improvements, and a warranty to go with it - that all-in-all sounds like pretty good value if you want more GT4 under engine warranty and a more robust base to get 500hp later. Imagine just what will happen when there's another X-51 like upgrade for the 4.0L from our friends at BGB...

Originally Posted by BGB Motorsports View Post
How about a comparison of a 718 GT4 4.0L vs. a 718 GT4 3.8L Clubsport AND a stock 718 GT4 4.0L vs. a stock 981 GT4 3.8L!?!



718 GT4 Clubsport Race Car (98 Octane) vs. 718 GT4 4.0L Street Car (93 Octane)

718 GT4 4.0L Street Car (93 Octane) vs. 981 GT4 3.8L Road Car (93 Octane)

 

That is one of the smoothest power/torque curves I've ever seen. No wonder feedback has been positive regarding its linear power all the way to redline!

 

Good demonstration of how unstressed the 4.0 might be, and how Porsche have used ECU calibration to harness it.

 

Subbed. Lots of potential in this engine. I bet 30-40 ponies (a la GT4 RS) especially if they can bump up the redline to 8500. Motoman stated the crankshaft and pistons are forged. However, Ive also heard from autotop.nl the valvetrain can only go up to 8000 rpm because it injects fuel 3 times per stroke. So they will either need a new valvetrain for the RS or come up with a different software calibration. My hope is its just software so the base gt4 can just be tuned to like 450+ hp. This engine is not even working hard with the current map. Wishful thinking

 

If I'm looking at the plot correctly, I read the the exact opposite.

The first plot shows 718 98 octane club sport gt4 vs. 718 93 octane street gt4 with a similar profile but ~20 hp differential. Not massive difference for the octane differential.

Looking at the second plot, which is the 718 gt4 vs. the 981 gt4, I see some obvious detuning after 6.5k (which clearly makes sense since its the same 911 S engine that produced 400 hp). It would make me assume the 981 GT4 is less stressed than the 718 GT4.

I'm making assumptions obviously, but I'm unclear as to the thought process that would indicate the 718 is unstressed. For me, it basically looks like the 4.0 street car is tuned proportionally lower for the 93 octane drop as compared to the 98 octane club sport. Due to the unnatural 981 GT4 curve, it looks like there's quite a bit more in hand for tuning.

A better indicator would be including a 981 gt4 clubsport in there. But I definitely don't see how the 4.0 looks unstressed. It looks like a normal power band for the respective octanes.

Also keep in mind this is a dynojet comparing a 718 PDK with the 718 Manual. Slightly different gear ratios will affect HP output. Don't what the final gear ratio is for each of these car's tested, but unless they are exactly the same, then it's not quite a fare comparison. If the BGB guys can tell us what gear each one was dyno'd in, we can see the difference in final gear ratio and see if the anticipated results match.

 

So 100 cell cat and higher octane fuel - and all the difference we see is 13hp and 13 torques?
Not too much.
And the RS probably has more aggressive ECU tune.

 

My specific point was 718 CS vs 718 Road car.

The 4.0 gives the plot it does, with no dips or breaks in the delivery.... take into account that these cars with increased cc, have 2 additional filters in the exhaust path and still have very restrictive headers.
Now the X51 3.8 in the CS by definition is doing more with less capacity....and running via less restrictive cats... and is also PDK which may well relatively increase the wheel power and torque.

Specific capacity outputs =
718 Clubsport 425ps/3.8L = 111.8ps per liter (420 mechanical hp/313kW) - 718 CS torque is also nominally up by 5NM to 425NM(313lbft)
718 GT4 420ps/4.0L = 105ps per liter (414 mechanical hp/309kW)
981 GT4 385ps/3.8L = 101.3ps per Litre (380 mechanical hp/283kW)

991.2 GT3 500ps/4.0L = 125ps per liter (493 mechanical hp/368kW)
991.2 GT3 520ps/4.0L = 130ps per liter (513 mechanical hp/383kW)

At a basic level, Quick maths, tells you if they apply the same level of tune/upgrade to the 4.0L as per the X51 3.8 in the 718 CS... it should give even more power.. (obviously assumption, made that they are not prohibited by design by doing the same kind of upgrade).
Looking at the GT3/RS specific capacities... the 718 4.0 does need to go anywhere near those levels and would only need a specific output of 110ps per liter (same difference in specific output as from GT3 to RS) to get to 440ps... that's less than the 718 CS x51 111.8ps per liter.
Same specific output as 718 CS X51 gives pretty much 450ps. All this and that before we even talk about torque....

Clearly the 4.0 is pegged... it is rated at the same torque as the 3.8... 310lbft.. and purely by virtue of the map.
Porsche have chosen exactly where they want to make it available.
Let's also not forget - the same engine goes into the GTS 4.0 with the same torque delivery (310lbft), pegged back by 200rpm vs 718 GT4 and still produces a 394ps... still more on paper than the 981 GT4 with the 3.8.

Really you only have to look as far as people that have done the 4.0 upgrades to know that engine design aside.. increasing capacity should bring a significant jump in performance... everyone that has done it is making much much more than the factory 4.0 414hp/420ps... and more into the 440ps and above..

 

Man those stock 718 power and torque curves look awesome. I can't wait to drive this car.

 

+1

 

As a former 981 GT4 owner, the 718 GT4 dyno plot makes me want my new GT4 sooner! The low end and dips have been improved, and the top end HP climbs all the way to the 8K redline compared to the nose dive of the 981. Nice!

 

That is a great looking power curve!

 

The GT4 is the evolved 9A2 EVO engine vs the GT3 motor which is GT3R and Cup derived. Much different and much different Rev range. The GT4 has the “integrated” dry sump vs GT motor with dry sump and de-foaming unit.

many other differences as well

 

thanks for the analysis! great summary

 

im not sure I draw the the same conclusions based on your analysis, but I can understand your logic. Multiple reasons exist for the variance in specific output of an engine. I still see see no real engineering understanding of why it would be more tunable, just some pretty basic assumptions.

I’m not saying it won’t be more tunable, I was just wondering if I was missing something, but it seems all your assumptions (save the one based on a small rpm differential that’s within the error for a single dyno result) are not based on the dyno plots as you had mentioned before.

Keep in mind CS cars are built to a certain spec for racing homologation for a particular series and are not necessarily a clear indicator of outright max specific output.

 

Correct, as you say those dynos plot cannot tell us what the outright max specific output is...
None of us are part of the power unit design/engineering team at Porsche - so we have no idea of what constraints, boundaries or limitations they are working too, and we don't know the product roadmap.
My commentary is based upon the reasonable assumptions that we all can make based upon what Porsche has done before, and what we have seen done in the aftermarket based upon the hardware platform.... so its not a question of having no real engineering understanding.... lol, the information isn't available to make a defintive assertion.

My original comment.. raises the question of how tuneable the new 4.0 engine might be, with the knowledge that aftermarket 4.0 conversions of the old 3.8 are much more potent, so that give us an indication of what a flat 6 4.0 revving to about 8K will deliver... and that although this is a very nice plot.. if the 4.0 engine is truely naturally more potent, Porsche could easily be applying capping/clipping to achieve a target delivery... in my opinion, thats what it looks like.

Ref, the old 3.8 the max state of tune we have seen from Porsche was from its application in the 991.1 GTS... 430ps/424hp 325lbft/440NM, slightly pipping the 718 CS application.