When to shift?

Randy803 · 12-16-2002, 07:27 AM

Now that I have my new 911 running smoothly I notice most of its power seems to really present itself at about 4000+ RPM. I am not used to running a car up this tight anymore and am wondering if its ok to shift at 5000rpm? I am curious what you long time 911 owners and racers think? I am not worried about the shifting aspect of the high rpms, I am a very smooth shifter I was tought years ago that the 915 gearbox must be treated kindly and shifted smoothly with positive gear lock. I once in the procces of breaking in an engine (in my much younger days) missed a gear in a hot 911 and pop went the tranny! I have learned not to get excited when shifting but to let the gears flow.

Milu · 12-16-2002, 07:38 AM

When your engine is warm don't be afraid to rev to the redline.

pbs911 · pbs911's Garage

Stay below 3000-3500 RPMs until the motor is warmed up. After that run it to the red line, about 6300 rpms. These motors and tranys were designed to run that way. If you only run the motor up to 4000 RPMs you will ruin the motor.

Rot 911 · 12-16-2002, 07:40 AM

The 915 is a tough tranny, but it does require smooth, positive shifting, with a slight wait between gears. Running up to redline in each gear won't hurt a thing and adds to the enjoyment. As you found out you need to shift at the higher rpm's. Shifting at 5k rpm's is just fine.

rs911t · 12-16-2002, 07:43 AM

I don't figure the my car's first owner added 1000 RPM extra without intending to use it. 7000 rpm sounds cool

Rick Lee · Rick Lee's Garage

My new engine has the Raceware rod bolts. I can't wait to give this baby a workout!

weber92037 · weber92037's Garage

I am curious about how it will ruin the motor if run only to 4000 rpm. Could someone please explain. Thanks.

dd74 · 12-16-2002, 10:10 AM

Quote:

Originally posted by weber92037
I am curious about how it will ruin the motor if run only to 4000 rpm. Could someone please explain. Thanks.

I believe not running the motors at higher RPMs can promote carbon deposits within the engine, which isn't good.

jyl · jyl's Garage

The motor is also unhappy if given significant throttle under load under 2,000 rpm (mine is, anyway).

So if one used a self-imposed 4,000 rpm, you'd be living in a tight band from 2,000 to 4,000 rpm, which seems like a pain.

I stay under 3,000 until the oil temp needle clears the solid white zone, then I take it to 6,000 rpm routinely. I try to rev it to redline (>6,000 rpm) several times on each drive.

My theory is (1) revving is fun and that's why I bought the car, and (2) if the thing is going to break, let's break it close to home.

Calspeed · Calspeed's Garage

Hey JYL... Since we both live in the City we gotta get together for coffee and chat Porsches one morning. Maybe get a SF breakfast run or something setup.

Calspeed

jyl · jyl's Garage

Maybe meet up at the first PCA Golden Gate Club auto-cross event of the year? I think it's in March. I'm planning to attend and watch and/or try AX.

Gunter · Gunter's Garage

The first and second gear on these 915's is not s@@t-hot, so, I don't rev. to high from 1st to 2nd, but after that, go higher in the other gears. 5-6000 sounds good.

masraum · 12-16-2002, 01:40 PM

My owners manual has a minimum RPM for shifting. It averages about 2500 rpm (slightly different for each gear) I'm sure that would apply for any year, and would actually be higher for the earlier smaller engined cars.

dickster · 12-16-2002, 01:44 PM

one of the reasons it is good to run to the line is to give the rods a stretch. if you don't you run the risk of a wear ridge forming in the bore and then you're in danger of breaking a piston ring if you take it to the redline stretching the rods beyond the wear ridge.

personally i like the power of bigger motors (3.2 is BIG in the uk) and like short shifting unless i'm gunning it. that means changing at anything over 2.5k. theres no harm in low rpm, just don't overload and bog the engine.