Why didn't Chevy Revise Gear Ratios on 7sp?
07-14-2013, 10:12 AM
#61
If you are a brainwashed sheep, you think the posted speed should define your freedom. If you think like an american, you travel at reasonable speeds to respect the safety of others, and on most interstates, 100 is within this range in a modern car if you're paying attention, on dry roads, with good visibility.
Of course, as a practical matter, like in many other areas of government these days, many local judges will lie and break the law to try to keep your illegally generated fine. And of course, many american jurors are brainwashed sheep.
So, you have to weigh your personal values and desire for free and rational living against your tolerance for harassment by government.
Of course, as a practical matter, like in many other areas of government these days, many local judges will lie and break the law to try to keep your illegally generated fine. And of course, many american jurors are brainwashed sheep.
So, you have to weigh your personal values and desire for free and rational living against your tolerance for harassment by government.
07-14-2013, 11:37 AM
#62
Instructor
That was Harlan's point that the new engine has so much low end the 0.4 can be used at legal highway speeds.
My point is, according to the numbers, there is no point in having a 7th gear as it will never be used at legal speeds on US roads. With the information available today, it appears that it would only be viable as a gas mileage gear at near triple digit speeds. Useful on the autobahn maybe, or if you have a highway where you feel comfortable cruising at extra-legal speeds for extended periods of time.
Or, the intent could be that you turn ~1k rpm on the highway at normal speeds. Maybe the LT1 has that much torque.
Or, the intent could be that you turn ~1k rpm on the highway at normal speeds. Maybe the LT1 has that much torque.
07-15-2013, 10:10 AM
#63
Melting Slicks
I understand it will hit 200 in 5th. What I was asking is if it can sustain that 200 in 6th at a lower RPM possibly getting better fuel economy. This matters in a 24 endurance run because you take less pit stops which nets a higher average.
07-15-2013, 08:06 PM
#64
Melting Slicks
I think the reason GM set up the Z51 gearing lower (higher numerically) is to improve the acceration and track times.
Look at where the Z51 RPM drops down to after the upshift. All near the torque peak. I image the with this gearing, the engine stays in the highest average torque range, which translates to the best acceloration.
I really like the gearing spread on the Z51 because on the upshift, its stays up in the higher RPM range.
How do you think a base trans car will accelorate when you upshift from 5th to 6th?
I don't think GM just threw a dart to come up with these ratios.
Look at where the Z51 RPM drops down to after the upshift. All near the torque peak. I image the with this gearing, the engine stays in the highest average torque range, which translates to the best acceloration.
I really like the gearing spread on the Z51 because on the upshift, its stays up in the higher RPM range.
How do you think a base trans car will accelorate when you upshift from 5th to 6th?
I don't think GM just threw a dart to come up with these ratios.
07-15-2013, 08:40 PM
#65
Drifting
Actually, for the best acceleration, the engine needs to stay in the range with the highest average horsepower, and not torque. To do this, you need many close ratios to keep the engine at, or near, the horsepower peak.
I believe they could have simply given 6th gear the same ratio as 7th gear, kept the highway mileage rating, and then gotten rid of 7th gear. At highway speed limits, the rpm difference is not enough to matter in terms of "feel". One possible reason to use both 6th and 7th would be if you plan to cruise at higher speeds....say, 75-85, then 7th might be a better ratio than 6th. If you're cruising at 55, 6th might be better.
IMO, from an engineering standpoint, this 7-speed is just a not-very-clever stretch of an existing dinosaur of a tranny. From a marketing standpoint, it's pretty smart though....
.
Last edited by RedLS6; 07-15-2013 at 08:56 PM.
07-15-2013, 09:40 PM
#66
Melting Slicks
That is true for gears 1, 2, and 3.
Actually, for the best acceleration, the engine needs to stay in the range with the highest average horsepower, and not torque. To do this, you need many close ratios to keep the engine at, or near, the horsepower peak.
I believe they could have simply given 6th gear the same ratio as 7th gear, kept the highway mileage rating, and then gotten rid of 7th gear. At highway speed limits, the rpm difference is not enough to matter in terms of "feel". One possible reason to use both 6th and 7th would be if you plan to cruise at higher speeds....say, 75-85, then 7th might be a better ratio than 6th. If you're cruising at 55, 6th might be better.
IMO, from an engineering standpoint, this 7-speed is just a not-very-clever stretch of an existing dinosaur of a tranny. From a marketing standpoint, it's pretty smart though....
.
Actually, for the best acceleration, the engine needs to stay in the range with the highest average horsepower, and not torque. To do this, you need many close ratios to keep the engine at, or near, the horsepower peak.
I believe they could have simply given 6th gear the same ratio as 7th gear, kept the highway mileage rating, and then gotten rid of 7th gear. At highway speed limits, the rpm difference is not enough to matter in terms of "feel". One possible reason to use both 6th and 7th would be if you plan to cruise at higher speeds....say, 75-85, then 7th might be a better ratio than 6th. If you're cruising at 55, 6th might be better.
IMO, from an engineering standpoint, this 7-speed is just a not-very-clever stretch of an existing dinosaur of a tranny. From a marketing standpoint, it's pretty smart though....
.
I was thinking the torque curve on the LT1 remains fairly flat from the 4600 peak 6000. Therefore the transmission ratios were designed to keep it between 4600 rpm and ~6400 rpm. Too many times, the gear ratios are not optomized and on upshift, it drops way down where the torque/hp is low.
Last edited by RussM05; 07-15-2013 at 09:46 PM.