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Car Forum / Saturn Cars / October 2005Passing Gear Ques.
New to this group I see we have some highly experienced experts offering advice. I'm looking to purchase a Saturn in the very near future, because of the 35~38mpg rating these cars have established. Over the past 3 weeks or so I have test driven 4 or 5 Saturns ranging in years from 1999 to 2002, all of them SL2's, all automatics w/ overdrive. One thing I found in common with all of the Saturns I've driven is what seems to be a down-shifting flaw. At speeds around 45 or 50 mph, when you step down on the gas (to hit "passing gear"), the transmission doesn't down-shift to the next ratio, say 4th to 3rd, or 3rd to 2nd. It seems to drop aaaaLL the way back to first gear, causing the engine to "rev" to a very uncomfortable 5~6,000 rpm. This can't be good for the engine! My question is,..is this a malfunction? or is this normal operation? Is it a mal-adjusted passing gear linkage?, or a glitch in the computerized shift program? Do all of the Saturns downshift this harshly?..it's odd that all of the one's I've test-driven behaved the same. I would like to add that my wife's car, a 2001 Chevy S10 2.2 litre 4cyl. w/ 4spd overdrive automatic, also downshifts in the same manner, all the way down to 1rst, no matter how lightly you press the accelerator. Is this simply the way GM designed the shift pattern for all its' 4 cyl. automatics?...a design flaw?...or just something out of adjustment? Any input will be greatly appreciated. Hope to hear from you soon. > New to this group I see we have some highly experienced experts offering > advice. I'm looking to purchase a Saturn in the very near future, > because of the 35~38mpg rating these cars have established. > <snip> Hi, David, Can't answer your main question but thought I should let you know that AFAIK you will not get anywhere near 35 + MPG in a 1999 SL automatic. I have a 1999 manual and get a bit over 40 during warm weather and 35 - 38 in cold weather, doing about 2/3 highway and 1/3 "city" driving. Good luck! Nobody out there can share their thoughts on this subject? Surely you're not all driving manual tranny's? >...One >thing I found in common with all of the Saturns I've driven is what [quoted text clipped - 4 lines] >"rev" to a very uncomfortable 5~6,000 rpm. This can't be good for the >engine! I don't think it's actually shifting all the way to 1st gear but is probably is going to 2nd, depending on how hard you've hit the gas. This is a fairly common design feature these days. It's designed to work that way. In the ancient times, cars equipped with large-displacement V-8s could pull away from a standstill in high gear and burn rubber at the traffic light, putting on a great show. For spectacular displays of torque, there's no substitute for cubic inches. But look at how cars are designed today, with the focus on fuel economy: four valves per cylinder to allow it to breathe efficiently at high speed, overhead cams that minimize valve float at high speed, and a tachometer with a redline at 6500 rpm or more. These powertrains are designed to produce their torque at high speed with the help of a trasmission that keeps the revs up. What's the point of those all those extra valves in the cylinder if the engine is going to loaf along at just above idle speed? These engines were built to rev. They'd probably hate being lugged in high gear. I notice that my mother's Northstar Cadillac works this way too, though the Northstar is a lot quieter than my Saturn when it does it. Don't worry about the breaking the engine, the computer will protect it from overreving. RK Henry > On Wed, 19 Oct 2005 09:43:47 -0400, poolboy2000@webtv.net (David) > > > > Don't worry about the breaking the engine, the computer will protect > it from overreving. really ? seriously ? usually things break when they are over-revved. I've always driven to avoid this jump in revs in my saturn Laz >> On Wed, 19 Oct 2005 09:43:47 -0400, poolboy2000@webtv.net (David) >> > > [quoted text clipped - 3 lines] >really ? seriously ? usually things break when they are over-revved. I've >always driven to avoid this jump in revs in my saturn According to what I've read in the service manual, if revs get too high the computer will regulate engine speed by selectively shutting down injectors. RK Henry > >> On Wed, 19 Oct 2005 09:43:47 -0400, poolboy2000@webtv.net (David) > >> > > [quoted text clipped - 9 lines] > > RK Henry This came about around the time of OBD II for a majority of cars so you dont want to paint everything with the same broad brush. While in gear a healthy Twincam wouldnt have a problem running all the way out to 7000rpm. It just tends to create undo wear... > This came about around the time of OBD II for a majority of cars so you > dont want to paint everything with the same broad brush. While in gear a > healthy Twincam wouldnt have a problem running all the way out to > 7000rpm. It just tends to create undo wear... IIRC, there's a fuel cutoff at 7500? 4000ish if not moving. I don't know if 4000 is a good launch RPM or not for Saturns but I wouldn't put it past GM's engineers to have picked that number for that reason... My '93 does this. IIRC, the cutoff isn't an EPA thing but more related to turndown ratios of the injectors and preventing the possibility of going 'oops too lean' at high RPM because the injectors hit 100% duty cycle. |
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