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Comfortable Cruising Speed

johnd

Donation Time
Out of curiosity, what is generally considered to be a "comfortable" cruising speed for O/D and non-O/D Alpines? I'm comfortable at 55-60MPH with the O/D on (3.89 diff) and the tach sitting around 3000 RPM.
 

alpine_64

Donation Time
Out of curiosity, what is generally considered to be a "comfortable" cruising speed for O/D and non-O/D Alpines? I'm comfortable at 55-60MPH with the O/D on (3.89 diff) and the tach sitting around 3000 RPM.

Comfort is a relative term... Before I had my OD setup I used to sit at 3600rpm on freeways... The car was OK with it but it wears the driver out at that constant rpm with the sound.

Also on a constant rum the lower the RPM without making the motor lug the better, less wear on the engine and better mpg. Cruising at a constant rpm anywhere around 3k is good for the car and you :).

YMMV
 

Bill Blue

Platinum Level Sponsor
While our car is comfortable cruising at any legal (or extra legal) speed, we aren't. The car is very happy at 85-90 (the fastest I've ever driven it) above 60-65 we find wind and road noise to be tiring. 55 is great! So there is a trade off. Hammer down the road at 75 and get there quickly but worn out, or piddle along at 60 and get there later, worn out from extra hours behind the wheel.

For long distance comfort, I do not think the gearing of your car is the limiting factor.

Bill
 

RootesRacer

Donation Time
Out of curiosity, what is generally considered to be a "comfortable" cruising speed for O/D and non-O/D Alpines? I'm comfortable at 55-60MPH with the O/D on (3.89 diff) and the tach sitting around 3000 RPM.

Without OD, and also without hugely tall tires, you will not be achieving 60mph at 3000 RPM. By most accounts with stock tires and a 3.89 rear, 60mph occurs at 3800RPM sans OD.

With OD, the RPM runs about 3200RPM at 60.
 
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alpine_64

Donation Time
Running o/d and 3.89 diff with 195/60/14's ... 60mph is around 2700 rpm ( 62mph is legal limit on freeway) so that's a very comfortable cruise in the alpine for engine and driver.

I used to run 3.89 no o/d and had 175/60/14 which gave about 3550 at 60mph .. Much buzzier, but if you put your foot down it accelerated well as it was nearing the torque band .

These days with hardtop on the car is quite a relaxed long distance car
 

SoCal'beaming

Donation Time
I'm not sure .... But my little kitten @ 6 grand sure scare's the 356's on the back roads ..:D... haven't used my od ... we'll see .....

..... David
 

Hodee

Donation Time
My Ser V has a strong motor but don't think I would ever take her to 6000rpm.
On a different note. I have a 3.89 rear and very large 225/16/15 rear tires no od. The perfect offset wheels and no rubbing anywhere on the body/leafs or elsewhere. They are 25 inches in dia. and raise the height a fair bit. BUT, the trade off in attaining highway speeds is worth it. 75mph at 4000 rpm is very doable and in a relatively comfortable "hum" for the motor as long as it is not held there for extended periods of time. Any thoughts on driving 4000 rpm for an hour?
 

Jimjordan2

Donation Time
OK, I just calibrated my tachometer, speedometer is within 1 mph, running 185/70/13 tires. Just converted to OD which is working great. Stock 67 series V with I imagine just the stock 3.89 diff, if that's pretty standard for a non OD car. 65 mph feels real nice at 3800 rpm.
 

alpine_64

Donation Time
OK, I just calibrated my tachometer, speedometer is within 1 mph, running 185/70/13 tires. Just converted to OD which is working great. Stock 67 series V with I imagine just the stock 3.89 diff, if that's pretty standard for a non OD car. 65 mph feels real nice at 3800 rpm.

Apparently most sv alpines on USA had 4.22 without o/d, so it'd quite possible you are running with 4.22. also what is unit did you get there are different % ratios. 3800 rpm in o/d serms high with a 3.89 rear.. should be 2950 ... even with 4.22 it would be 3200
 

George Coleman

Gold Level Sponsor
Stock Alpine V for me with 4.22 rear 1725cc motor 4000rpm (approx.) running 60 MPH. Now Toyota 5 speed. 3.70 rear 70MPH turning 3500 RPM. I find that the 1725 likes it under 4000, just dose not seem to work as hard below this!. :cool:

If you need more info on Toyota boxes here is a good tech. site to help you along i used the T-50 box number 1. picture. http://www.retrotech.co.nz/Tech/Toyota-boxes.php
 
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Jimjordan2

Donation Time
OK, now you're gonna make me find out what I have for a rear-end. LOL Sure seems to be a lot of variances here though. I guess with a 50 year old car, lots of parts have been swapped out. I know I'm using a bunch of them from diff. cars.
 

Tom H

Platinum Level Sponsor
Jim, It's quite easy to measure your axle ratio. Jack up one rear wheel. Put a chalk mark (or just note an observable point)on the drive shaft or pinion flange. Then rotate the wheel exactly 2 full rotations (equivalent to both wheels rolling one full rotation) while observing the drive shaft. The drive shaft will rotate approximately 4 times. Carefully observe if it rotated slightly less (3.89) or slightly more (4.21) than exactly 4 turns. You will clearly see one or the other. Maybe start with the pinion flange exactly horizontal to see this. Or maybe rotate the wheel 4 times for more observable excess (or shortfall) from 8 full rotations of the drive shaft. Be sure to observe the direction of rotation of the shaft as you rotate the wheel.


Tom
 

Jimjordan2

Donation Time
OK, measured it like you said. It's a 4.21 Thanks Tom, always good to know this stuff. Will now have to dig my spare out and check that one.

And Warren, yes, Queens English was pretty awesome, I was just happy to get there and back in one piece. This engine and transmission hadn't really been tested on the freeway very much.
 

hartmandm

Moderator
Diamond Level Sponsor
Any thoughts on 4000 rpm for 30 mins straight?

Search the forum and you'll find that folks have commented about valve seat recession being a problem at 3k rpms and above. Recommendations are to get hardened seats and valves designed for unleaded gas. I have no personal experience with the issue, just passing on what I have read here over the past few years.

Mike
 

Hodee

Donation Time
thanks Mike, I run a fuel mixture of 93 unleaded pump gas and a leaded 110 octane race gas. I try to keep it at a 50/50 ratio but it is always fluctuating as I do not "pre-mix" them beforehand. Just an on the fly collaboration as I see the gauge getting low. The race gas is very expensive but i don't drive many miles a year and it's cheap insurance for valve recession and guaranteed lead content.
 

Hillman

Gold Level Sponsor
My 1725 with OD is happy to cruise at 3800 RPM all day. Don't trust the speedo, but it's likely above Canada's max of 110 KPH.
 

alpine_64

Donation Time
Hodee,

I'm not sure your tach is correct.. or your speedo is out?

You say 65mph = 3800, you have a 4.22 with 185/70/13 tyres.

This would give:
a tyre dia of 23.2"
Circumference of 72.88"
So 20.36 mph per 1000 rpm in o/d top.

So 3800rpm should = 77.36mph.
 
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