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AMEN to that brother! We should both send a memo to Porsche to go back to its roots, stop charging for fastest ring times and stop making it a time thing! That's at least a 100K savings big smile right there.
Because CAFE is based on both around town and highway. And they allow for only specific gears tested at specific speeds.
BS. Every other car in the world with a FPC has tight gears at least until a final tall overdrive gear. The GT350 is tight 1-5 for an example. C7Z manual has a tight spread up to 6th and still didn't have a gas guzzler tax. A tall 7th was all it took.
They didn't want to pay Tremec for new gears, plain and simple.
BS. Every other car in the world with a FPC has tight gears at least until a final tall overdrive gear. The GT350 is tight 1-5 for an example. C7Z manual has a tight spread up to 6th and still didn't have a gas guzzler tax. A tall 7th was all it took.
They didn't want to pay Tremec for new gears, plain and simple.
I don't recall any C7 having tight gears.
Z06 MPH @redline by gear vs GT3 (manual) vs GT350
1: 67 vs 52 vs 47
2: 95 vs 81 vs 68
3: 126 vs 113 vs 94.8
4: 152 vs 144 vs 123
5: 186 vs 179 vs 152
6 225 vs 220 vs 242
7 339 vs NA vs NA
Ironically, the Z06 had the best 1st gear for road racing, but then got tall. You want first gear to be super tall (you're basically never using it on a road course), so that it's really more like 2nd gear. Then you have more gears "left over" So you can use 2-3-4-5 instead of 3-4-5 (for example).
Corvettes were always been known having very tall gears. Most tracks you could probably just stay between 3 and 4. A Posche and Mustang will use 2, 3 and 4. Probably use 5th for the Mustang on most bigger tracks). Never tracked a Z06, but my GS only ever used 3 and 4 at the track (different ratios, I know).
I'm not sure why they didn't do different gears. I doubt they are going to charge them much for a different gear ratio if the rest of the trans is the same. Then again, maybe the physical size of the gears was too big or small to get what they wanted without bigger engineering changes. Seems kind of silly to develop this whole crazy 5.5L FPC that revs to almost 9000rpm just to made it to a pushrod transmission.
Z06 MPH @redline by gear vs GT3 (manual) vs GT350 vs C8Z
1: 67 vs 52 vs 47 vs 44
2: 95 vs 81 vs 68 vs 73
3: 126 vs 113 vs 94.8 vs 105
4: 152 vs 144 vs 123 vs 145
5: 186 vs 179 vs 152 vs 197
6 225 vs 220 vs 242 vs 251
7 338 vs 320
8 388
7 339 vs NA vs NA
Ironically, the Z06 had the best 1st gear for road racing, but then got tall. You want first gear to be super tall (you're basically never using it on a road course), so that it's really more like 2nd gear. Then you have more gears "left over" So you can use 2-3-4-5 instead of 3-4-5 (for example).
Corvettes were always been known having very tall gears. Most tracks you could probably just stay between 3 and 4. A Posche and Mustang will use 2, 3 and 4. Probably use 5th for the Mustang on most bigger tracks). Never tracked a Z06, but my GS only ever used 3 and 4 at the track (different ratios, I know).
I'm not sure why they didn't do different gears. I doubt they are going to charge them much for a different gear ratio if the rest of the trans is the same. Then again, maybe the physical size of the gears was too big or small to get what they wanted without bigger engineering changes. Seems kind of silly to develop this whole crazy 5.5L FPC that revs to almost 9000rpm just to made it to a pushrod transmission.
Yep, I don't get why they aren't optimized.
I added the C8Z speeds in each gear to your table above in red.
Delta from 3rd to 4th in the C7Z is 26 mph, in the C8Z it's 40 mph
Delta from 4th to 5th in the C7Z is 34 mph, in the C8Z it's 52 mph
Delta from 5th to 6th in the C7Z is 39 mph, in the C8Z it's 54 mph
At Sebring when I had my C7Z I got to 152 mph on the back straight basically every lap. Video just posted on youTube of a C8Z shows 147 mph each lap. He's also a better driver than me - though that's not saying much.
Yep, I don't get why they aren't optimized.
I added the C8Z speeds in each gear to your table above in red.
Delta from 3rd to 4th in the C7Z is 26 mph, in the C8Z it's 40 mph
Delta from 4th to 5th in the C7Z is 34 mph, in the C8Z it's 52 mph
Delta from 5th to 6th in the C7Z is 39 mph, in the C8Z it's 54 mph
At Sebring when I had my C7Z I got to 152 mph on the back straight basically every lap. Video just posted on youTube of a C8Z shows 147 mph each lap. He's also a better driver than me - though that's not saying much.
Yeah, that really tells the story. At the top of 2nd gear, it's 22mph slower than the C7 and by 5th gear it's 11mph faster! it's wild how big those gaps are, especially with DCT. You don't want to shift too much with a true manual because there's real time lost there with each shift. There are places where I am better off bouncing off the rev limiter for a second or two than shifting. But DCT is so fast, you barely lose any time at all.
Did they really just use Z51 gearing? I mean, wtf. It's 9000 rpm FPC with 170 more horses It's kinda different.
As far as those top speeds, that's really surprising for a number of reasons. 1) It has more power 2) it has more efficient aero 3) it has more gears and 4) the C7Z06 pulls timing like a ****. My buddy and I ran very similar top speeds at COTA, him in a tuned Z06 + CAI and me in a stock GS. Only difference in aero was the stage 3 bridge on his spoiler.
Can't believe GM threw away so much performance to lazy gearing.
I think they chose the gearing in the C8Z06 to be steeper in first to help the 0-60 metric as that’s important to some, then they have to have it make more torque at the rear wheels with gear multiplication to match the C7Z06 acceleration as the LT4 of course had much more torque and could get away with pulling taller trans gears. It had a cruising rpm of 1400 at 70mph in 7th gear with cylinder deactivation which helps, here are the other NA cars rpms at 70mph in their top gear for comparison.
I didn’t think the idea of the mph spread is important between gears as much as the rpm drop, which if you try to keep that consistent then the mph gained in each gear goes up as they get taller for faster speeds. Below I customized 4th, 5th and 6th, 7th is actually OE 8th and if the custom 7th was in between the 6th and 8th it’d be a 600rpm drop at 70mph between 6th/7th and 7th/8th which doesn’t sound like a smooth transition and don’t know any other auto cars out there with that big of a drop in their two final gears. The C6Z06 had that big of a drop, but granted it made more low end torque. It would have accelerated better if it had the C6ZR1 5th and 6th gear ratios, but they didn’t put it in the C6Z06 for CAFE reasons and that was over 15 years ago when emissions were less strict.
Yeah, that really tells the story. At the top of 2nd gear, it's 22mph slower than the C7 and by 5th gear it's 11mph faster! it's wild how big those gaps are, especially with DCT. You don't want to shift too much with a true manual because there's real time lost there with each shift. There are places where I am better off bouncing off the rev limiter for a second or two than shifting. But DCT is so fast, you barely lose any time at all.
Did they really just use Z51 gearing? I mean, wtf. It's 9000 rpm FPC with 170 more horses It's kinda different.
As far as those top speeds, that's really surprising for a number of reasons. 1) It has more power 2) it has more efficient aero 3) it has more gears and 4) the C7Z06 pulls timing like a ****. My buddy and I ran very similar top speeds at COTA, him in a tuned Z06 + CAI and me in a stock GS. Only difference in aero was the stage 3 bridge on his spoiler.
Can't believe GM threw away so much performance to lazy gearing.
The stage 3 bridge was actually great for me. The last thing I needed was going any faster and it definitely provided downforce, no matter how inefficient. It was also a huge help with high speed braking, my car was crazy fast without it.
I’ve switched to a C5Z now. It has the same wide gears as the C7 GS. They’re great like you said, wide powerband and less time wasted shifting.
Originally Posted by PRE-Z06
I think they chose the gearing in the C8Z06 to be steeper in first to help the 0-60 metric as that’s important to some, then they have to have it make more torque at the rear wheels with gear multiplication to match the C7Z06 acceleration as the LT4 of course had much more torque and could get away with pulling taller trans gears. It had a cruising rpm of 1400 at 70mph in 7th gear with cylinder deactivation which helps, here are the other NA cars rpms at 70mph in their top gear for comparison.
I totally get they need a lower RPM for gas mileage as the motor is larger displacement than any of the above. 7th & 8th can do that, looks like they’re optimized for it well.
Only other reason I can think of is they left some room for the ZR1?
SR: optimized for 0-60
Z06: optimized for 0-100 (1st, 2nd 3rd are perfect imo)
ZR1: optimized for 0-150?
This should be an Ask Tadge question although I think he’s quit doing that.
I think they chose the gearing in the C8Z06 to be steeper in first to help the 0-60 metric as that’s important to some, then they have to have it make more torque at the rear wheels with gear multiplication to match the C7Z06 acceleration as the LT4 of course had much more torque and could get away with pulling taller trans gears. It had a cruising rpm of 1400 at 70mph in 7th gear with cylinder deactivation which helps, here are the other NA cars rpms at 70mph in their top gear for comparison.
I didn’t think the idea of the mph spread is important between gears as much as the rpm drop, which if you try to keep that consistent then the mph gained in each gear goes up as they get taller for faster speeds. Below I customized 4th, 5th and 6th, 7th is actually OE 8th and if the custom 7th was in between the 6th and 8th it’d be a 600rpm drop at 70mph between 6th/7th and 7th/8th which doesn’t sound like a smooth transition and don’t know any other auto cars out there with that big of a drop in their two final gears. The C6Z06 had that big of a drop, but granted it made more low end torque. It would have accelerated better if it had the C6ZR1 5th and 6th gear ratios, but they didn’t put it in the C6Z06 for CAFE reasons and that was over 15 years ago when emissions were less strict.
Rpm drop is directly linearly related to mph drop.
You drop 20% in mph, you drop 20% in rpm
Rpm drop is directly linearly related to mph drop.
You drop 20% in mph, you drop 20% in rpm
Right, I was talking about each gear having the same mph gain. Obviously accelerating is quicker at lower speed ls because of less aero drag. How much of a rpm drop in 7th and 8th is acceptable when cruising?
05-05-2023, 06:56 PM
It's kinda different. 
