FenwickHockey65's Great Thread of GM Knowledge

[GretchenGotGrowl]

Remember the target audience...

[Camaro_Corvette]

Target audience is anybody with money.

[GretchenGotGrowl]

Originally Posted by Camaro_Corvette

Target audience is anybody with money.

True.

[PYROLYSIS]

Might as well go for 50.

[DGthe3]

Originally Posted by GretchenGotGrowl

Great minds think alike. LT1 may not make as much power down low, but I think it will be right around the same time.

I think they'll be almost on top of each other. We haven't seen GM's official dynochart for the LF4, but we can speculate based on the LF3. The LF4 makes 14 ft-lbs more at peak torque, while at peak power the difference is about 24 ft-lbs (44 hp). That would indicate (to me) that GM focused mostly on the top end rather than the mid-range or low end. So while there might be some gains down low, I would be surprised if its more than a couple foot-lbs.

I'm basing this off of GM's dyno charts for the LT1 (http://gmpowertrain.com/2014_images/charts_lg/lt1_chart_stingray_v2.jpg) and the LF3 (http://gmpowertrain.com/2014_images/...V6_LF3_CTS.jpg). Its kinda hard to do a direct comparison between the two because of the different scalings that they inexplicably use, but its the fairest comparison that we've got at the moment. The LT1 holds a slight advantage down low, though not much (most of its advantage is in the mid-range & top end, but we're not looking at those for now).

Without mapping it all out, it looks like the LT1 holds a 5 to 10 ft-lb advantage below 2500 rpm. So the LF4 would need to pick up something like 15ft-lbs to have even a small advantage down low. It could happen, not saying it won't ... but in order to have a decent advantage it would need to gain more (vs the LF3) down low than it does in the midrange or up top. That scenario seems unlikely to pan out to me.

But either way, at these speeds we're talking about between 1 and 10 hp on engines making 75 to 200 hp (since hp = [torque x rpm]/5252). No matter what, its not going to be all that significant.

[GretchenGotGrowl]

Originally Posted by DGthe3

I think they'll be almost on top of each other. We haven't seen GM's official dynochart for the LF4, but we can speculate based on the LF3. The LF4 makes 14 ft-lbs more at peak torque, while at peak power the difference is about 24 ft-lbs (44 hp). That would indicate (to me) that GM focused mostly on the top end rather than the mid-range or low end. So while there might be some gains down low, I would be surprised if its more than a couple foot-lbs.

I'm basing this off of GM's dyno charts for the LT1 (http://gmpowertrain.com/2014_images/charts_lg/lt1_chart_stingray_v2.jpg) and the LF3 (http://gmpowertrain.com/2014_images/...V6_LF3_CTS.jpg). Its kinda hard to do a direct comparison between the two because of the different scalings that they inexplicably use, but its the fairest comparison that we've got at the moment. The LT1 holds a slight advantage down low, though not much (most of its advantage is in the mid-range & top end, but we're not looking at those for now).

Without mapping it all out, it looks like the LT1 holds a 5 to 10 ft-lb advantage below 2500 rpm. So the LF4 would need to pick up something like 15ft-lbs to have even a small advantage down low. It could happen, not saying it won't ... but in order to have a decent advantage it would need to gain more (vs the LF3) down low than it does in the midrange or up top. That scenario seems unlikely to pan out to me.

But either way, at these speeds we're talking about between 1 and 10 hp on engines making 75 to 200 hp (since hp = [torque x rpm]/5252). No matter what, its not going to be all that significant.

True, we don't know the numbers for the LF4, yet. However, we know the LF3 makes 90% of peak torque as low as 2500 RPM (it's 3000 RPM for the LT1). The LF4 is running 50% more boost, so unless turbo size is significantly larger than on LF3, that should push the torque curve left (perhaps 90% of peak down to 2200 RPM?). Again, I don't think it will affect acceleration much given similar gearing, but there should be a bit more power down low on the LF4.

Either way, this is very promising for the 6th Gen SS. A 4.0 s or faster 0-60 time would be amazing.

[FenwickHockey65]

[DGthe3]

Originally Posted by GretchenGotGrowl

Either way, this is very promising for the 6th Gen SS. A 4.0 s or faster 0-60 time would be amazing.

Indeed. I keep trying to find a reason to justify why a 6th gen SS might be more like 4.2 or 4.3 seconds (which would still be a decent improvement over the 5th gen) ... and I'm having a hard time doing it. All the reasonable guesses on the specs point to the ATS-V and 6th gen SS being practically identical in acceleration. Likely to be very similar in weight & weight distribution. The power & torque curves of the LT1 & LF4 will be very similar. They'll probably even use the same transmissions. The main differences will be in the fine details, like gearing ratios and choice of tires -but thats not going to hurt 0-60 by a half second. So 4 seconds flat sounds almost conservative ... but I just can't let myself believe that to be true.

[GretchenGotGrowl]

Originally Posted by DGthe3

Indeed. I keep trying to find a reason to justify why a 6th gen SS might be more like 4.2 or 4.3 seconds (which would still be a decent improvement over the 5th gen) ... and I'm having a hard time doing it. All the reasonable guesses on the specs point to the ATS-V and 6th gen SS being practically identical in acceleration. Likely to be very similar in weight & weight distribution. The power & torque curves of the LT1 & LF4 will be very similar. They'll probably even use the same transmissions. The main differences will be in the fine details, like gearing ratios and choice of tires -but thats not going to hurt 0-60 by a half second. So 4 seconds flat sounds almost conservative ... but I just can't let myself believe that to be true.

Yeah, I'm having a hard time with it, too. On one side you would expect a similar time if a LT1 was in the ATS-V, and you would expect the Camaro on the Alpha platform to have similar performance. However, on the other hand the Stingray with the A8 does 0-60 in 3.7 secs. That's a lighter car than the ATS-V (and presumably the 6th Gen Camaro). I guess we just have to wait and see.

[FenwickHockey65]

I'll just leave this here.

[hotlap]

^ oh my!

[KMPrenger]

Wowzers.

[ilirg]

Got my tix to NY show, cant wait to see this new Caddy in person.

[camaro2lt]

I'll be there for press day. Will update with pics