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914World.com _ 914World Garage _ Rear axle ratio?

Posted by: bernbomb914 Mar 28 2003, 04:35 PM

It seems like my engine revs a lot at freeway speeds. The oil temp comes up to the danger level if I run at these speeds for any length of time. (3400 rpm at 70 mph) I have a 1.8 with FI and it runs normal to rich? cleaned the oil cooler put in new flaps thermo. what could be causing this problem.

Bernie

Posted by: Brad Roberts Mar 28 2003, 04:57 PM

What size tire Bern ??

3400 is a couple 100 rpm over what I think it should be.

B

Posted by: bernbomb914 Mar 28 2003, 05:11 PM

B.
they are 195x60 15s hp4s

Bernie

Posted by: bernbomb914 Mar 28 2003, 05:16 PM

The problem is I installed the 911 guages so I have oil pressure and temp in the dash pod. so now I know. oil pressure drops to 1 duck when it comes to idle when hot.

Bernie

Posted by: Brad Roberts Mar 28 2003, 05:28 PM

Bernie,

when hot with regular oil the car might have 15lbs of oil pressure at idle. Synthetic could be a tad LOWER. Do you have the flaps under the firewall ??

All the teeth on the fan ??

Timing set correctly ??

B

Posted by: SirAndy Mar 28 2003, 05:29 PM

clutch holding up?

Posted by: Brad Roberts Mar 28 2003, 05:31 PM

Bern,

the other thing I see repeatedly: people replacing the oil cooler seals and pinching them half closed during reassembly.

B

Posted by: bernbomb914 Mar 28 2003, 06:23 PM

B
Timing is correct, have flaps, next change will be syn, clutch is good, haven't had motor out to check lines for crimping. have a 2L core engine that I will rebuild and install when I get rich. is a exterior cooler nessessary?

Bernie

Posted by: Aaron Cox Mar 28 2003, 06:27 PM

I think i get about 3100-3200 rpms maybe a tad lower in 5th gear while going ~about 70mph...w/ 165 r 15 cooper tires.

Posted by: silver six Mar 28 2003, 06:35 PM

Bernie,

I assume you either calibrated your 911 guages to work with your engine's pressure and temp senders or you replaced the senders. If not, you'll get bad readings.

Douglas

Posted by: bernbomb914 Mar 28 2003, 08:11 PM

new senders to match.

Bernie

Posted by: Dave_Darling Mar 28 2003, 11:34 PM

"Druck" is German for "pressure".

1 on the gauge is 1 Bar, or one atmosphere. 1 Bar is about 14.5 PSI. Which is quite enough for your motor at idle--you don't start worrying until you see less than 10 PSI at warm idle.

--DD

Posted by: Racer Chris Mar 29 2003, 05:49 AM

Tire size has no bearing on rpm vs. odometer indicated speed, since both gauges are connected to the engine/gearbox.
There are only two final drive ratios, with the shorter one being about 10% under the stock one. That would put rpm up by more than 300 at 70mph if you had the short R&P installed. That is unlikely in a street car, since the alternate is somewhat rare.
I guess it's possible that one of your gauges is calibrated wrong. Perhaps the zero point of the tach is off. The easiest way to test would be to wire up a different tach.