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> Optimum rpm range around town and cruising around 70mph?
mlindner
post Jul 21 2022, 08:53 AM
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If any time applying load, I down shift so RPM is always above 3,000/3,500. This is for a 2.2 S six, power band is from 4,000 to 7,000.
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Dr Evil
post Jul 21 2022, 10:08 AM
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QUOTE(VaccaRabite @ Jul 20 2022, 01:47 PM) *

QUOTE(Optimusglen @ Jul 20 2022, 12:38 PM) *

Shoot... I'm pushing 4k in my 6 at 70-75ish (IIRC)

Wonder if I should go bigger tires...


If the gear ratios are the same in a /6 as they are in a /4 - then yes you need taller tires. Your speedo must be way off too. Guessing you are using a 50 series tire?

Zach

Nope. The gearing in a stock /6 is shorter.

4 - A, F, N, V, ZD
6 - A, GA, O, V, ZA

5th is shorter so higher RPM at freeway speeds. 2 and 3 are actually taller, 4th is the same. Changing wheels and tires is not gonna be a good fix as the result may make a weird looking car with a speedo that lies. Easy enough to change the gearing. The 914 really does have the best all around modern gearing for all around use.
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Optimusglen
post Jul 21 2022, 02:00 PM
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QUOTE(VaccaRabite @ Jul 20 2022, 12:47 PM) *

QUOTE(Optimusglen @ Jul 20 2022, 12:38 PM) *

Shoot... I'm pushing 4k in my 6 at 70-75ish (IIRC)

Wonder if I should go bigger tires...


If the gear ratios are the same in a /6 as they are in a /4 - then yes you need taller tires. Your speedo must be way off too. Guessing you are using a 50 series tire?

Zach


I'm running 205/60-15 (627mm diameter)

I've only ever used a GPS speedometer, but I may be misremembering the speed/revs.

trans is a side shift from a 4-cyl, I don't believe it's been opened.
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emerygt350
post Jul 21 2022, 05:18 PM
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You would think so... But it is definitely reading faster on the speedo.
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VaccaRabite
post Jul 22 2022, 10:36 AM
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QUOTE(Optimusglen @ Jul 21 2022, 04:00 PM) *

QUOTE(VaccaRabite @ Jul 20 2022, 12:47 PM) *

QUOTE(Optimusglen @ Jul 20 2022, 12:38 PM) *

Shoot... I'm pushing 4k in my 6 at 70-75ish (IIRC)

Wonder if I should go bigger tires...


If the gear ratios are the same in a /6 as they are in a /4 - then yes you need taller tires. Your speedo must be way off too. Guessing you are using a 50 series tire?

Zach


I'm running 205/60-15 (627mm diameter)

I've only ever used a GPS speedometer, but I may be misremembering the speed/revs.

trans is a side shift from a 4-cyl, I don't believe it's been opened.


QUOTE
Nope. The gearing in a stock /6 is shorter.

4 - A, F, N, V, ZD
6 - A, GA, O, V, ZA

5th is shorter so higher RPM at freeway speeds. 2 and 3 are actually taller, 4th is the same. Changing wheels and tires is not gonna be a good fix as the result may make a weird looking car with a speedo that lies. Easy enough to change the gearing. The 914 really does have the best all around modern gearing for all around use.


You have to have different gearing as Mike noted above (or be mis-remembering your speed vs revs as you said). Your tires are really close to mine (205/55 r15) and I'm right at 3K when doing 70. With a taller tire you should be revving less, not more. Also, is you car flared? 205/55r15 is the largest tire I could get under mine without rubbing. Did you need to roll your fenders or something to get the 205/60 to fit?

Zach
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barefoot
post Jul 25 2022, 08:19 AM
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With my 235-55 ZR17's (27"OD) I'm running 3100 RPM at 70 mph.
Interesting that the speedo reads consistent with my GPS even though these tires are O/S compared to stock OEM . Don't know what's in my tranny however.
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Jamie
post Jul 25 2022, 09:30 AM
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QUOTE(barefoot @ Jul 25 2022, 06:19 AM) *

With my 235-55 ZR17's (27"OD) I'm running 3100 RPM at 70 mph.
Interesting that the speedo reads consistent with my GPS even though these tires are O/S compared to stock OEM . Don't know what's in my tranny however.

I've been running Michelin 205-65-15's on stock steel 5 1/2"rims for several years, and have cross referenced my speedo vs. GPS and have about a 2 MPH variation at 70MPH. I've wondered how accurate the GPS readings are, as my tire diameter is very close to stock tire diameter.
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Optimusglen
post Jul 25 2022, 02:34 PM
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QUOTE(VaccaRabite @ Jul 22 2022, 11:36 AM) *



You have to have different gearing as Mike noted above (or be mis-remembering your speed vs revs as you said). Your tires are really close to mine (205/55 r15) and I'm right at 3K when doing 70. With a taller tire you should be revving less, not more. Also, is you car flared? 205/55r15 is the largest tire I could get under mine without rubbing. Did you need to roll your fenders or something to get the 205/60 to fit?

Zach


Guessing the error is in my memory, I'll check next time I have it at highway speeds.

Not flared, but I did roll the inner lips flat in the rear.

(IMG:http://www.914world.com/bbs2/uploads_offsite/live.staticflickr.com-19709-1658781262.1.jpg)
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