My take is that in any engine, keeping the rev's down will extend it's life. In my daily drivers I shift low, drive responsibly, keep up on maintenance and have had great results. Over 200k with no engine work on several cars at various times.

The Porsche is my fun car and I drive the hell out of it. I usually try to shift in the 5k range and regularly take it up to the redline. While it has been able to handle this my guess is that the engine would last longer if I took it easy on it. That's not why I bought it.

Would you rather buy a used engine from a car that had been babied or driven hard?

Has anyone taken apart a Carrrera tach to see what turns on the CASIS light durring wide open throttle acceleration? Is it strickly RPM? Know what that RPM is?

The only thing I ever did with my CASIS light is disconnect it.

Some one said that when you pull the wire that sends the fuel injector pulses to it it still does the RPM thingy.

Huh? Not sure what you mean. I pulled the wire and my '86 Carrera kept running just fine.

For your 911 Never pay any attention to the CASIS light. It was put there for the US gas guzzler crap.

In my 3.2 the owner's manual says to never shift any lower than ~2600 rpm (actually there is a chart with minimum shift points per gear, I believe the chart says
Minimum Shift points
1st gear 2600
2rd gear 2500
3rd gear 2400
4th gear 2600

My owner's manual also says what Jack Olsen said earlier "Never lug the engine..."

My opinion
During normal driving I say shift anywhere between 3500 and 4500, during spirited driving shift anywhere between 5500 and the rev limiter.

On the freeway I am generally cruising between 3200-3800 (unless I'm going over 80, yes I am often speeding). If the speed drops down to 60 then I drop back to 4th and run the car in the mid 3000's.

For a 3.2 the best shift point for acceleration is approx redline.

For your Jetta, who knows. For acceleration it would depend on peak power and gear ratios, but I can tell you that each car feels different and has a very different torque curve. My '88 loves to hit redline, but my wifes pontiac that has a dohc 4 cyl which shows very similar peak hp and torque (not values, but rpms at which the values occur) really dislikes being revved to redline, it falls on it's face well before redline. It's torque curve seems to be weaker above peak and fatter down low.

It's basic fizziks guys, picking a fixed rev point to upshift for max accleration is bogus if you don't account for gear change variations. Maximum accleration comes when you shift to maintain maximum available thrust at the wheels, peak engine horsepower just boils down to revs*torque.

Plot the rear wheel torque across the revs for each gear, as the torque falls off you want to shift about where the thrust would drop below what the next gear has (or redline!).

On my 88 if you hold the pedal to the floor the CASIS light comes on somewhere in the orange band. A common way to disable the light is to pull the wire from the DME. Looking at the schematic I'm guessing that wire sends the injector pulses to the tach. I recall someone also saying this didn't disable the top end feature.

i don't understand what the point is,
put me in any car, and i'll shift where appropriate
it's not rocket science now is it?!!?

you press the loud pedal, and if you feel it's not accelerating as fast any more , then you shift up

every car is different, and you can feel when to shift
you can discus the ideal upshift on two 89 carrera's, but the truth is what's ideal for A , is not for B

euro gearboxes are a lot more sporty, us gearboxes are lame, maybe not every model , but i can confirm it to be so on a 944S2 with a CASIS light >> lame gearbox

other than the gearbox, every engine will have a different curve some engines wear out faster, others have small upgrades. etc etc...

so realistically ... what's the point discussing it... drive it and listen to your ears and feel it in your lower back...

i never even look at my RPM indicator.... in any car...

Actually I think the US gearboxes were more sporty for the '88 MY. Generally closer gears is sportier, and the difference in gearing in '88 is that the Euro models have a slightly higher 4th and 5th, otherwise they are the same (Euro meaning RoW, but I think Swiss gearboxes were different than both the RoW and US).

Is the Shift indicator in any way controlled by the ECU or strictly RPM based?

Those F1 guys (and most other racecars) must have them for a reason...

The CASIS light is controlled by the ECM, because it takes more into account than just rpm. The rpm that the light comes on changes according to throttle opening which to me says that vacuum or throttle position is also a factor.

ever heard an F1 car?
then imagine sittin in one, with earplugs with a radio ...and a helmet on top ...you can't hear the differences in your engine noise well enough to use it for shifting...

don't compare apples with oranges, it doesn't work

EDIT and any street driver, who needs an RPM indicator for his shifts... is a danger since that means his attention is on his dash, instead of on the road... one fraction of a second lost because your reading your tach , adds up to a lot more reaction time lost to brake for a child crossing the street, or another car crossing or hitting something , or road debris...

Different but not necessarily sportier
http://forums.pelicanparts.com/uploa...1081285765.jpg

OK, looks like the 3.2L cars with the 915 were sportier in the RoW, but I still am pretty sure that the 3.2L G50 cars were more closely geared in the US. Actually, I think that chart is wrong in the middle if my books are right.

this probably won't format well, but I'll see what i can do...

88 G50 US
Gear ratio _Overall___Top Speed in Gear
3.5_______12.06____39.96
2.0588____7.09_____67.93
1.4090____4.85_____99.25
1.125_____3.88_____119.53
0.8889____3.06_____151.28
88 G50 Euro
3.5_______12.06____39.96
2.0588____7.09_____67.93
1.4090____4.85_____99.25
1.0740____3.70_____125.19
0.8611____2.97_____156.16

could be, haven't driven all those, but it is true for the 944 S2
sat in one last weekend, and it had no power in 4th and 5th

and again , the the table just prove the futility of discussing the optimal shift point... to many different gearboxes, to many different engines, to many unknown variables....

gotto feel when to shift, not calculate

Well I'm still claiming that optimal accelleration trough gears will only be achieved by choosing shift points that maximize sum of swept areas under power curve for particular run trough the gears.

Prove me wrong.

Goran, you are, of course, correct. A graph of engine power is needed to get the best shift points for accelleration.

graph and gearing numbers... and some Matlab quality-time.

i'm not going to argue with that, but let's be honest
do you calculate it everytime you get yourself a new car???
do you take it to the dyno everytime you change something on your car, which might affect the power/torque curve???
do you really think it gives you a huge advantave over the regular butt guess shifting folks???

No, but I was a math geek long time ago and I still like elegant predications ;-)

Now bring turbocharger rotational inertia and tyre-slip at launch into equation and it starts to get interesting...

lol :D

but i think you'll agree, that it's mostly a matter of sensing when to shift, and that's the most real advice to give to somebody who's new at shifting and specifically shifting in a sports car...

Well rule of the thumb would be to shift a little bit north of max power point (especially in 930), but there are no thumbs in mathematics... :)

I usually shift at about 7K right when the valves start to float!!


Todd

Aw, let's just shut up and drive....

The real question is does it matter if the transmission is in a Club Sport, a regular 3.2L car or a turbo-look?? And would it make one of those faster on the track!!

;)

Something like this?
http://forums.pelicanparts.com/uploa...1081293516.jpg
:)

That is what I have always heard. My car also seems to run better with a little more spirited driving. When I putt around, it seems to bog down a little or feel like it is loading up. Don't know who to explain it, but a good blast to the red line keeps the revs feeling real snappy and responsive.

On my 964:

In running 0-60s on my G-Tech and after I did my dyno, I found it best to shift at about 6,300 to 6,500 instead of my 7,000 red line. I stay in the torque better, the back tires lets out a scream and and I run just as quick if not quicker at the 6.5k +or- a few.

On both 996s:
I pretty much take it to red line to get best results on G-Tech.

Bill, can you recreate that graph showing rear wheel torque ?

All you need are the torque #s from a dyno, gear ratios(final and individual) and tire heights or revs/mi?


Thats my engine w/ current and proposed tires.

I shocked ! You don't have that data on hand ?

I have all the pertinent information for my car. Why would I need more;)

Charlie, You might be interested in this one I did comparing my C3 w/ stock engine, 915/44, 225/50x16 tires and the same car w/ 3.8RS, 915/67, 275/40x17 tires

http://forums.pelicanparts.com/uploa...1081305282.jpg

I'd like to hear what Walker thinks, I know he has had plenty of engines opened, under every driving condition imaginable.

"ever heard an F1 car?
then imagine sittin in one, with earplugs with a radio ...and a helmet on top ...you can't hear the differences in your engine noise well enough to use it for shifting..."

That's not entirely true. I raced Grand Prix bikes (two strokes) and you can hear the motor and feel it but it revs so fast the needle just swings over to 12K-14K like you are in neutral. The power comes on so fast you have to check the tach so you don't bounce off the rev limiter. It pulls really hard then falls flat, it can catch you off guard on a long straight. The power can be in such a small band (like 10K to 12.5K, and it's geared to stay in that band after every shift) that the tach helps you learn when to shift so you don't trust your ears or seat. Also you look at it if your power falls off so you can tell the mechanic where the hiccup is. Or use it as a reference to note how the engine performs.
All the same reasons to note for a street car, it just happens more slowly.

I took my brother in-law out last weekend and we cruised around for a few minutes in the 5-6K range. Figured I took some miles off the engine but man did it sound wonderful!

How many times have I -over here- heard the remark, "yes, no rust, but watch it, the car was imported from the U.S. and the engine is full of muck cause the engine hasn't seen any speed".

I guess that's just hearsay, of course.

My guess is that, yes of course, "the overlappong torque areas" give you the best speed and, in general, very average shifting ranges will put least stress on the machine. It's just so that, on our dry-sump aircooled flat-6 engines, "average" is not to be exaggerated, meaning ...anything between 3000 and 4000 is pretty cool, not to worry in the least. And I repeat, in 5th gear, 4000 rpm gives my ROW exactly 100 mph, which I have done all day long in the past over an 800 km distance (before I got scared of traffic tickets).

I think it was Nostatic had a point: "stay in 2nd to be able to react quick". Sounds reasonable to me. For reasons personal to my car, my policy is different, I use 2nd to get out of 1st (I NEVER stay in 1st for any length of time, gosh is that ever unpleasant!), use 2nd for as long as I remain accellerating or -for a short period- higher up in the revs (I don't cruise in 2nd), and -generally- cruise in 3rd (or 4th but then I should be out of city streets already...). Wanta know why I avoid staying in 2nd? Because when really "slowpoking" in 2nd, she tends to jump out of that gear, which doesn't happen in 3rd... grin grin...

Somehow, I still think most people in Europe would exhibit a slightly different "driving profile" from the U.S. I think the type of road infrastructure, and the directional shape and physical size of city-streets, suburban-streets etcetera... also play a large role in that. I sure do not wish to "patronize" our U.S. Porsche friends, but my feeling is that the "average" U.S. driver (1) doesn't have a manual box and (2) if he/she does, shifts at far lower revs. If I had a 5.4 liter V-8, I probably would do likewise... (I don't really know this first hand, though).

Belgik, you're probably right in a lot of ways, thank goodness that I'm not the "average" US driver.

How's that bumper sticker go? "Drive it like you stole it"