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The tune runs rich on 93 so heat increased but that's part of the reason we added the third radiator, and Cobb is in the works on Stage 2 once they can address the cooling factor.
You've said this a couple of times now. I figured it was a typo the first time since running rich actually cools an engine. It's running lean that creates more heat. Would it be more accurate to say that the Cobb tune allows you to burn more fuel at the optimum mix to create more power, which in turn generates more engine heat?
That makes sense to us (could be completely off target though, we're definitely not tuners by any stretch of the imagination). The tune uses a richer fuel mixture which picks up power, but with a lack of cooling we're thinking that in this case more power is generating more heat with no where for it to go. With COBB looking to address the cooling for their Stage 2 which creates even more power we think that would be the case here as well. But again, we may be way off here, this is just what we've experience so far.
Originally Posted by sobiloff
You've said this a couple of times now. I figured it was a typo the first time since running rich actually cools an engine. It's running lean that creates more heat. Would it be more accurate to say that the Cobb tune allows you to burn more fuel at the optimum mix to create more power, which in turn generates more engine heat?
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Can you do some timed runs like 0-60, 1/4 mile? Curious to know what it is now doing with the tune. I do like the sound of "same shakes I get while driving a 911 Turbo. It's a frickin monster."
You've said this a couple of times now. I figured it was a typo the first time since running rich actually cools an engine. It's running lean that creates more heat. Would it be more accurate to say that the Cobb tune allows you to burn more fuel at the optimum mix to create more power, which in turn generates more engine heat?
Actually, running rich OR lean can cool an engine. Running closer to stoichiometric heats it. I suspect the tune has reduced the fuel/air mixture to extract more heat (thus pressure) from each stroke. Leaner, but still rich. "Optimum" would be stoichiometric but that would likely be too hot (and likely start knocking).
Some fresh images from 3 days at the track with PCA. The car didn't skip a beat the whole time. We might need to pick up a set of the Rennline grille inserts because we kept puling out pieces of rubber from the center radiator....
We went with the normal PASM lowering springs from H&R, not the adjustable fronts and they have been good to us so far. We had H&R on the last car we ran and never had an issue
Originally Posted by MC129
Curious about the H&R PASM lowering springs you have on this. Thinking about putting a set on my 981 Cayman GTS that I take to the track. Do you have the sport springs or the VTF adjustable ones?
i have a similar project now based on my cayman 718 gts, Manthey racing will take care of it for all tha chassis parts and adjustment
i have a question about the rear wing, what is the top speed you already done with it? I would like to mount one but iam a bit afraid about the resistance in the time due to the very simple screw in system.
my car will be used only on the nurburgring with high speed and downforce all the time...
The highest speed we've seen has been 142mph on the back straight at Sebring before braking for Turn 17. It has a lot of shake to it at that speed so we're exploring a way to reinforce it.
Here's two fresh photos from the Toys for Tots rally we hosted last weekend
Originally Posted by SEB74
That’s a very nice project, congrat for it!
i have a similar project now based on my cayman 718 gts, Manthey racing will take care of it for all tha chassis parts and adjustment
i have a question about the rear wing, what is the top speed you already done with it? I would like to mount one but iam a bit afraid about the resistance in the time due to the very simple screw in system.
my car will be used only on the nurburgring with high speed and downforce all the time...
Maybe you would be better off with the Techart rear wing?
I notice it has an extra duck tail integrated into the design which distributes weight across the rear trunk lid and looks to tie everything in and make it more secure.
Maybe they also matched it better to the Techart front lip.
Maybe you would be better off with the Techart rear wing?
I notice it has an extra duck tail integrated into the design which distributes weight across the rear trunk lid and looks to tie everything in and make it more secure.
Maybe they also matched it better to the Techart front lip.
We did look into that wing and after a few discussions with NR Auto about their GT4 style rear wing we decided to go with that one. They informed us that they have several 981 customers tracking with this wing and had no issues. We might switch to the carbon wing and see how that does. We will be sending videos to NR Auto after our next track weekend in January.
We completed about 10 days on the Bridgestone RE-71R's and we ordered a set of Michelin Cup 2's to give them a shot and compare the differences. Those are being mounted right now.
Could you give any feedback on the two different tires? I'm trying to decide between them for a set of dedicated track tires and wheels. Thanks!
Could you give any feedback on the two different tires? I'm trying to decide between them for a set of dedicated track tires and wheels. Thanks!
We got really comfortable with the RE-71R's while they were on. Great feedback and lasted 4 weekends for us. Once we switched to the Cup 2's we noticed an immediate rise in grip after the got a few heat cycles and they are a lot quieter, which is a good and bad thing. It did take us a few sessions to dial in the pressures and we felt they were the best at 28F/29R HOT which means 20F/21R COLD. We've only done a couple of days on them and we have two four-day events coming up in January at Sebring so we should be set for those. I think for a dedicated track car the Cup 2's are the way to go. If you do Auto-X and occasional track time then the RE-71R's might be a better.
Thank you! Interesting observation on the heat cycles. I was wondering why the Tire Rack offers their heat cycling service for the Cup 2s but not the RE-71Rs--your experience may indicate that the RE-71Rs don't benefit as much from it.
You've said this a couple of times now. I figured it was a typo the first time since running rich actually cools an engine. It's running lean that creates more heat. Would it be more accurate to say that the Cobb tune allows you to burn more fuel at the optimum mix to create more power, which in turn generates more engine heat?
More power = more heat, simple as that. Figure the engine is around 35% brake thermal efficiency. A Prius engine is around 40%. A diesel is around 45%. About 30 years ago, gas engines were only around 20%. Anyway, we will assume 35% for the Cayman S engine as a nice easy number to work with because the engine makes 350hp. So really, the engine is using 1000hp of power, but can only convert 35% of that into actually moving the car, so 350hp. The other 650hp ends up as waste heat. Heat dumped out of the coolant, heat dumped out of the oil, heat dumped out the exhaust. With the Cobb tune making more power from burning more fuel, that also means more heat is being generated that needs to get dumped. So yeah, need bigger radiators.
I saw APR tore apart a Cayman and 3d scanned in the whole engine package. Packaging is very tight.... they will be room for improving the radiators for the air-water IC system, but don't expect a ton of improvement as there's just very little extra space in there. For a dedicated track car, could ditch the A/C system and add an extra water radiator in place of the a/c condensor.
11-15-2018, 10:59 AM
