Markski is a breath of fresh air. He puts everything into its proper perspective, no BS. Couldn't ask for a more helpful and honest guy.

 

Mark is a very good guy to have on the forum. He's helped MANY MANY people on this forum, including myself. He does not try to push anything at you, but he just suggests things from his personal experience with these cars. It's not to often you see that!

 

We have (and held before) some records with a stock block 997TT engine, with all the bells and whistles of course...

 

Unbelievably honest. After much debate, my expectations were high and the kitchen sink he sold me works EXACTLY as he said it would...

 

Thanks, Powell. I almost bought your old set up but WOW your new set up looks wicked!! We need to talk one of these days. Maybe at the next coffe and cars or the Texas Mile....

 

+1. We are over 4000 miles from him in the UK, and his service is second to none. The fact that he was a Privateer first, only goes to help his business now as he has been there, dont it, and got the t' shirt, and tries to pass all this knowledge onto his clients.

In fact, the only reason I have bought bits from other vendors from this site, is that he did not stock them, and on those occasions, he probably would have been able to help me out if I had asked.

Superstar, and in more than one profession

Mr F

 

I thought everyone is a Privateer unless a manufacture is footing your bills?

 

I was taught to use this: HP divided by displacement = X then times X by new displacement. If you use 800hp divided by 3600 you get .223 hp per cc now if you times .223 by 3800 you get 847.4 That is slightly more the 5%. Now the cams, if not set right they can hurt you more the help you if you do not set the lobe separation for a turbo setup. N/A cams are not turbo cams and depending on boost levels used the intake cam takes the back seat and the exhaust cam is king. This is only my experience, others may vary. All test was conducted on a closed course with a professional driver...

 

Got it but the gain would be %5 only?

 

Well... the logic does hold up. (3.8-3.6)/3.6 = ~5.5% gain in displacement. So, all things equal, you should expect around a 5-5.5% gain.

Start changing variables like CR, cam specs, rotating assembly weight, air/fuel, timing, boost, etc... and then, who knows? Maybe a little more, if everything's optimal.

 

Assuming the starting point, the 3.6 was optimally configured, and the ending
point 3.8 is optimally configured and equally stressed (no more), then you'd
get your 5%. Only. Tops. There is no magic. If the 3.6 was not optimized at
the start, and the 3.8 was, or you accept more stress in the 3.8 than the 3.6
was bearing, then maybe you get more. But the more likely scenario is that
the 3.6 is more optimized to begin with, and it has some parts that will not
tolerate more stress or work or flow etc.
This is because the whole 3.6 motor was designed as such. Going to 3.8 is
not just adding the displacement. There are many other factors that may
arise in the intake, combustion, exhaust, and strength areas that were fine
and were all balanced for the 3.6, but which individually may become
bottlenecks to power or reliability when pushed by 3.8 liters of displacement.
For instance, how sure are you that the flame-front propagation in the
cylinder will allow a complete combustion of the charge in the same time as
it did in the 3.6? If not, you may have to alter the timing and not get as much
high RPM power (proportionally). In other words, unless you do as good and
completely integrated (expensive) a job as Porsche, you may either end up
with less than the 5% you can hope for, or you may get your 5% or more,
but only for the few weeks till something expensive breaks.

 

There are a lot of variables in play here as mentioned above but the simple ratio hp vs displacement is not that simple. Assuming you optimize a stroked 3.8l (cams, valves, etc...) you should get much more than 5% increase. The reason being is that in a stroked motor for every rev the pistion will be traveling a greater distance in the same amount of time thus it is traveling faster. This has the net result of significantly increasing VE. So the VE for an optimized 3.6l motor vs an optimized 3.8l motor will be less. This is why a guy like Sonny Leonard's motors have such high VEs. Optimizing a stoked motor is not trivial as already stated.

 

except 3.8 motors are not stroked only over sized pistons

when you pair the 3.8, plus head porting plus cams, and a tune that maximizes all of this you can easily see 150whp but you also gain the ability to run more boost safely so its a whole new ball game

but your looking at almost 20k on top of a regular engine build to do a 3.8 build minimum your looking around 35-50k for this engine rebuild is it worth it to you?

 

I run a 3.6 motor period. The 2mm thinner sleeves, 2mm less gasket area, and greater room for piston to rock are not items I am willing to put to the test. I feel that if it were stroked and much longer rods you would see much better gains.

 

Actually nothing to test anymore. With the race rule changes a couple years ago Porsche started making true 3.8L motors.