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Pretty stoked to see what Chris gets out of his, you guys should get on a track together.
We plan on it for sure next year. Hopefully we’ll learn a lot once Chris’s set up is dialed in with his 6GT3 top end to make my transition to the 7.1Cup top end seamless.
The valve sizes are the same if I’m not mistaken but the 7Cup heads have much bigger ports. The 997 intake manifold has 2 resonance chambers with dual flapper valves vs a single flapper set up on the 996. The 997GT3 variocam also has a greater adjustment range. There will likely be slightly more overall efficiency on the 997 parts but not a game changer. It will be interesting to compare apples to apples as the engines are identical internally with same turbos.
I find this stuff fascinating as all the development for the 997 heads was born, ultimately, from the trials and errors of the 996 cup heads. Very neat evolution.
Thanks guys, yeah I'm excited to see what it makes also. Was chatting with Chris earlier this week about some reasonable limitations and if it lands in the ball park of John's predictions I'll be over the moon. I know the math says it is possible but is just hard for me to wrap my head around it.
It'll be a ton of fun to have both of the cars on the same track at the same time, I'll consider it a win if I can stay within eye sight of John's car! Chassis and aero is so much more developed on his and the time/cash I had set aside for that went into this engine so I've got some catching up to do on that front.
As far as differences, John nailed it, it is mostly in the port size as well as the shape of the port. The valves are the same size but I believe the shape of the 997 port either changed the size or position of the spark plug slightly. The cam adjustability is greater, and I think there is a small difference in cam spec as well. It'll be really interesting seeing the difference in the variocam and the dual resonance plenum.
I think your car will be ready to go right out of the box with what we learned on mine when you do your engine minus the car specific/elevation tuning differences. Getting the cam control/timing was a little time consuming but I could get it done first shot now and have shared everything with Chris through the trial and error. Obviously I'll share where my variocam and plenum settings end up, but I imagine that is going to change for yours.
I find this stuff fascinating as all the development for the 997 heads was born, ultimately, from the trials and errors of the 996 cup heads. Very neat evolution.
One thing I regret not doing that we thought of after the fact is having both of our heads put on the flowbench. McKenzie Cylinder Heads had them both in hand at the same time, but we didn't even think of doing it until my heads were already in Colorado.
I think it got around 4-5 miles per gallon on the old setup, I don't expect it to be any better- but this is track mpg... Maybe I'll put some pump gas in and see what it will do on street mileage one day. I don't think it ever really got better than 20 mpg or so in the last few iterations when I did drive it on the street more, even worse when I ran e85.
As T10 mentioned, the port shape is quite different on the 7 heads, the intake side is much more open. Here is a youtube video I found that talks about the differences between the 6GT3 and the 7Cup heads (at the 0:30 min mark). One other notable difference is that the spark plug used on the 7 head is a slightly smaller diameter presumably done to leave more "meat" between the plug and valves to reduce any chance of cracking. You can see the valve sizes are maxed out in the picture below. I don't believe the head differences will make that much difference between the 6 and 7. I think the larger gains will be as a result of the larger dual resonance manifold used on the 7. Both the 6GT3 and 7Cup heads have valves that have a 23% larger cross section area than that we are currently using on my 996Turbo McKenzie heads. That in and of itself will increase flow through the head by a minimum of 23% which is huge.
I think it got around 4-5 miles per gallon on the old setup, I don't expect it to be any better- but this is track mpg... Maybe I'll put some pump gas in and see what it will do on street mileage one day. I don't think it ever really got better than 20 mpg or so in the last few iterations when I did drive it on the street more, even worse when I ran e85.
Interesting, one would think that E85 has a cleaner, more efficient burn in the combustion chamber than premium fuel.
As T10 mentioned, the port shape is quite different on the 7 heads, the intake side is much more open. Here is a youtube video I found that talks about the differences between the 6GT3 and the 7Cup heads (at the 0:30 min mark). One other notable difference is that the spark plug used on the 7 head is a slightly smaller diameter presumably done to leave more "meat" between the plug and valves to reduce any chance of cracking. You can see the valve sizes are maxed out in the picture below. I don't believe the head differences will make that much difference between the 6 and 7. I think the larger gains will be as a result of the larger dual resonance manifold used on the 7. Both the 6GT3 and 7Cup heads have valves that have a 23% larger cross section area than that we are currently using on my 996Turbo McKenzie heads. That in and of itself will increase flow through the head by a minimum of 23% which is huge.
The flow charts in the video are very interesting - I would have thought the Cup head would have flowed more on the intake side of things, likewise for the exhaust. The silicone molds were a nice 3d representation of the port design, neat way to look at it.
With your heads, are you doing any more porting/flowing, or are they just going to go straight on?
The flow charts in the video are very interesting - I would have thought the Cup head would have flowed more on the intake side of things, likewise for the exhaust. The silicone molds were a nice 3d representation of the port design, neat way to look at it.
With your heads, are you doing any more porting/flowing, or are they just going to go straight on?
There is virtually nothing that could be done to the ports to improve them based on talking with Todd McKenzie. He is the best in the business when it comes to headwork and I trust his judgment. I sent him the heads so he could refresh them and properly shim the valve train for a turbocharged application. I told him it's totally up to him to do his thing on the heads but he chose to leave the ports alone. The ports on the 7Cup heads are significantly larger than his ported heads that I'm currently running and with the 23% larger valves, I see no issues here. The beauty is going to be in having a safe "8500" redline. It annoying to have to call it quits at 7500 even though I think we would be ok to go to 7700 with the current heads. We've run them to 7800 on the dyno but that just doesn't any headroom for any minor overrevs. The Cup heads are good for 9K+ with the lighter lifters.
Replaced my water pump this week. It was dripping a few weeks ago, so I picked up a new one at my local dealer, knowing it would be inevitable.
I started to prep for the job Thursday, jacking it up, removing a few items, cleaning some components and such. Then, before I knew it, I had everything off and the old one out. So on Saturday I took my time and put the new one on, and everything back on by that evening (It's not often I have a few days in a row with no outside activities planned). It was relatively easy compared to some other maintenance items... after you remove the rear bumper, heat shields, muffler assy, engine mounting plate and serpentine belt . Sorry I didn't take any photos to document the operation.
Then the next day, I hurriedly drove to town and entered her in our bi-annual All Porsche Auto Show held by our local PCA chapter. Surprisingly, she took 1st Place in the Contemporary 911 Class!
09-01-2023, 02:45 PM
. Sorry I didn't take any photos to document the operation.
