Itinerant Air-Cooled

Oooooh. This thread could get interesting....Makin' popcorn now...

Ok, warmed up the bus, filled the gas tank and drove around today reving up to 6200 rpms in first and second gear 4 times and still no rev limiter other than me chickening out at 6200rpms. It really seemed like that was all she could go to vs the 914 with stiffer springs which will go to 6500 rpm + without too much effort with hp.
Maybe its a 79 ECU thing?

Bleyseng wrote:Ok, warmed up the bus, filled the gas tank and drove around today reving up to 6200 rpms in first and second gear 4 times and still no rev limiter other than me chickening out at 6200rpms. It really seemed like that was all she could go to vs the 914 with stiffer springs which will go to 6500 rpm + without too much effort with hp.
Maybe its a 79 ECU thing?

What indicated speeds were you hitting in those gears?

Dunno as I was watching the tach!

I was just wondering because I've wound mine out pretty high but don't have a tach. I know I can do 65-70 in third before it stops pulling but don't know what rpms I'm pushing. Never felt any kind of limiting.

Haha, I have never gone past 60 in third but this "test" was in first or second. In second gear I was flying on a freeway onramp and had to shift or I would hit the car in front of me as he was a slowpoke merging into traffic...
6200rpms the bus seemed to be either valve floating or just starving for air as it wouldn't rev much beyond without forcing it.(like going downhill)
Now the 914 rev's easily to 6500 but its setup to do that.
I think I am going to get a 5400 rev limiting rotor for the bus as I have some guests coming and they will drive it around town. For the 914 I use the 5800 rotor but I rarely let anyone besides Monique drive as other people can't figure out the weird early Porsche shift pattern.

I remember the rev limiting being a function of the rotor. Replace it with a different rotor, and you lose the protection. Richard Atwell (of ratwell fame) says the rev limiting function of the '79 is in the ECU, while earlier models rely on the rotor.

Ah Ha! that answers the question. I understand that the with the rev limiting rotor fuel is still dumped into the cylinders, making for raw gas being pushed out the exhaust. The ECU function shuts off the injectors, right? Just like on overrun the ECU shuts off the fuel as you decelerate until 1800 rpms. The 79 ECU is a improvement for smog I am sure but at what rpm does it shut off?

Westy78 wrote:I was just wondering because I've wound mine out pretty high but don't have a tach. I know I can do 65-70 in third before it stops pulling but don't know what rpms I'm pushing. Never felt any kind of limiting.

I am wondering too!

As per previous posts on this thread:

As soon as VW was required to equip their engines with catalytic converters (1975 CA), the ignition-based rev limiter was a no-no. Imagine cutting ignition at 5,400 rpm . . . all that fuel slamming into the catalytic converter

The L-Jet ECU allegedly limits revs by soft fuel cut-off at the injectors.
Colin

091 Transaxle Speeds @ 6,000 RPM.
..1.....2.....3......4
25 / 47 / 77 / 109 mph

Jasan, your engine can easily handle factory 5,400 rpm rev limits.
You and I did a pull in 3rd to 65mph, the factory rev limit of 5,400 rpm should be 69 mph in 3rd with an 091 transaxle.
The factory stated in every owner's manual that the bus had rev-limiting protection.
The rev-limiting rotor was used through '74 and maybe on later Federal fuel injection BUT NOT NOT NOT on catalyst-equipped cars, period.
Colin

Bleyseng needs to tell me if he hit 47 mph in 2nd tach be damned. He knows right here that 6,200 rpm would be more than 47 mph, and has already done that.

Amskeptic wrote:

72Hardtop wrote:So what would be the ideal shift points for say... a 2.1L (2056cc) with 002 trans and 185R 14 tires?

You have a guesstimate in Bleyseng's answer . . . but we at Itinerant Air-Cooled endeavor not to guess.

Please provide the following information (if you have to research, research!)

Torque Peak RPM.
Horsepower Peak RPM
Your 002 ring and pinion ratio (the 5 ribs were 002 with a 4.86, we need to know if yours is a 5 rib or a 3 rib with 5.37)
Colin

Well it's a 1972 Westy hardtop (002 trans 3 rib)

72Hardtop wrote:

Amskeptic wrote:

72Hardtop wrote:So what would be the ideal shift points for say... a 2.1L (2056cc) with 002 trans and 185R 14 tires?

You have a guesstimate in Bleyseng's answer . . . but we at Itinerant Air-Cooled endeavor not to guess.

Please provide the following information (if you have to research, research!)

Torque Peak RPM.
Horsepower Peak RPM
Your 002 ring and pinion ratio (the 5 ribs were 002 with a 4.86, we need to know if yours is a 5 rib or a 3 rib with 5.37)
Colin

Well it's a 1972 Westy hardtop (002 trans 3 rib)

Amskeptic wrote: Please provide the following information (if you have to research, research!)

Torque Peak RPM.
Horsepower Peak RPM

If you do not have those numbers, well . . . . stick with the "'72 Bus" diagram.
Colin

Hey Colin...

I noticed on your chart for the 72 shift points it shows 78mph @ 3,900 rpm and to the right for 4th gear it shows 30 - 78mph 1800 - 4700rpm.

Which is it at 78mph for the 72 with the 3-rib? 3,900 or 4,700rpm? I was under the impression it was around 4,200 with the 3rib and 185R14's.

Given I have a 2056cc with a 3rib 002 and running 185R14's how close to the 091 gearing would a set of 195R14's get me?

72Hardtop wrote:Hey Colin...

I noticed on your chart for the 72 shift points it shows 78mph @ 3,900 rpm and to the right for 4th gear it shows 30 - 78mph 1800 - 4700rpm.

Which is it at 78mph for the 72 with the 3-rib? 3,900 or 4,700rpm? I was under the impression it was around 4,200 with the 3rib and 185R14's.

Given I have a 2056cc with a 3rib 002 and running 185R14's how close to the 091 gearing would a set of 195R14's get me?

I fixed that writeographical error. What an involved process that was. When your browser cache/cookies flush, the correction should show up.

195s do not qualify as "freeway flying" over the 185s. Rotations per mile is 2.3 % less with the 195s, and the speedometer reads 1.4 mph lower with the 195s. Your engine would benefit from about 100 fewer rpms per mile.

4,200 rpm with the 002 5.375 rear axle? 70 mph.
Colin
(thanks for pointing that error)

Bleyseng wrote:other people can't figure out the weird early Porsche shift pattern.

Reverse, o'er left and back.
First forward, and a notch o'er right. Second,third,forth, follow the H and again over and up for 5.
Err, ah, what sort of social strata forces itself on you not knowing such basic 901 's social grace?
Eric// ex 74 1.8 phoenix red,ex 73 silver 2.0. missing a mid engine boxer 4 in life..
But back to the thread. Quite some info! !

I was talking about the early 901 pattern.
Reverse is all the way left and forward
1st is all the way left and back to you
going to second let the spring guide you slightly right into second from 1st so you don't nick reverse