guys how long would be the safest time to wait until i can take the car for a spin.... like when i first start it in the morning..


is it also safe to rev while at full choke?

thanx heaps guys

 

well, if by rev you mean get on it and drive aggressive i would wait like 20 mins at least. but to just drive you can do instantly. It was 14 degrees the other morning and i was runnig late so i didn't have time to warm it up at all. got it, shut door, seat belt on, started and off i went. Its fine as long as you take it really easy.

 

I agree with 82transam. I don't have any problem with mine too.Taked easy...

 

local motor builder said the most engine wear occurs when the motor is warming up. our motors are made of aluminum, steel, and cast iron. those dissimilar metals warm up and expand at different rates. changing tolerances along the way to warmed up. 'the metals need time to gel' his exact words. you really should wait until the water temp is at 160 degrees before driving it. ALL the local racers i talk to say that. i wait until the water gauge needle is on the lower horizontal line before taking parking brake off. and baby it till at full temp. no more than half throttle.

it's your motor, not mine!

-bp-

 

agreed, but thats an ideal world, if I could let it warm up everyday i sure would, but I barely make it to school on time as it is. but everything drivefast7 says is true. so if you have the time to always warm up then you might as well do it.

 

Gel???? Expand at different rates??? NO! Gel is when a fluid starts to solidify, so that obviously is a very poor word to use. As for the rate of expansion, that rate is temperature dependant, based on the metal's thermal conductivity. Both aluminum and steel conduct heat very well, (aluminum slightly better). But, with both metals recieving the same amount of heat, they will expand at very nearly the same RATES. What you mean to say is that they will expand to different volumes, based on the metals coefficient of thermal expansion. This is an intrinsic property to the metal, and is not time dependant, and thus not a RATE. With the amount of heat flux being roughly equal for both the steel and aluminum layers in the rotary motor, then the rate at which they expand will be roughly equal. The difference is of course the metals final volume.

This is called heat stress, expanding metal due to increasing temperature. In a nuclear power plant, thermal stresses coupled with actual stresses due to pressure are huge concerns, and to mitigate it we power the reactor up and down in stages in order to alleviate the stresses. Except for the cooling down stage for my car when I reach my destination, I power up my car in stages too. I start it and let it warm for about 5-7 minutes with the choke on while I go back inside and brush my teeth and kiss the wife and daughter goodbye, then I drive off down the block easy, never exceeding 1/4 throttle. I gradually progress to increased throttle use as the temperature comes up, and by the time I reach the highway its fully warm, just in time to get on it to merge into the traffic for my 15 mile run out to the plant.

 

Realistically, if you take it easy on the motor and don't rev it fast or over 2.5k, you should not be creating any more wear than if you warm it up stationary. Of course if the temp is any colder than 14F, or in Soviet Canukistan, -10C, let it warm up fully before leaving your parking spot, as the oil needs time to be transformed from jell-o back into liquid. Even 0w30 oil's flow is greatly reduced at extreme cold temperatures.

Matt
1979 SA22C

 

Strider is right. The thermal expansion properties vary between metals. At a given temprature, say 160 degrees, aluminum will expand more or less than a different material. But, it is possible for those two different metals to expand at different rates. Lets say aluminum will expand 1 cubic millimeter when heated to 150 degrees. Lets say steel will not expand 1 cubic mm until it gets to 250 degrees. If that aluminum rotor housing and steel centerplate are heated at the same time by the same heat source, there will be a different rate of expansion. The aluminum will be expanding faster, regardless of which one has the greatest expansion capacity. Feel free to challenge that hypothesis, I'm an aircraft mechanic, not a physics major

 

I stand corrected. I'm thinking of thermal stress, which is different than strain caused by thermal expansion. The thermal stress is roughly the same because both are receiving the same heat and at the same temperature, but the thermal induced strain rate is different.

Forgive me, I'm dog tired and not thinking straight.

 

Uhh...I just let it warm up .

~T.J.

 

thanx guys big help

 

Was that sarcastic? If so, basically, I would say to keep it gentle for a while unitl you at least see the needle move. If you werent being sarcastic, Im glad we could help .

~T.J.

 

NO NO!!

i mean it!

i said BIG BIG HELP GUYS.. really..

thanx heaps!

 

This has been one of those big issues ever since cars are around... Truth is, if you are a normal driver with a normal car (even a Seven) you should just start the car and drive of, but not push the engine. Stationary or idling isn't the perfect way to warm up the engine, as it will mean a less then perfect oiling. Best is to just drive away. I know plenty of people tend to think the other way around, and they simply let the engine run for a few minutes before they drive the car. So I don't want to start a big dicussion here. This is just what I learned, as a mechanic...

 

You can rev it at full choke but i would'nt rev anywhere past 3,000. Light taps on the throttle too; and if you choose to drive shift before 3,000 until it's fully warmed up.

 

agreed, i shift at 3k until its warmed up.

 

same here. as long as you're easy on it until the temp gauge hits normal operating temp.

 

And it reaches operating temperature a *lot* faster under load (gentle driving) than idling.

 

yea, nearly twice as fast with mine.

 

Please explain this? At cold idle the motor in my 74 REPU reads 71psi on the autometer oil pressure gauge. That is the factory maximum pressure for the motor, per my service manual.

Another way I look at warmin up a motor is like this. Who would want to be dragged out of bed and made to jog an 8 minute mile without first taking your shower, streaching, and starting off with a leisurly 12minute mile first? That's what you're doing to the motor when it's not warmed up.

 

hehehe I got dragged out of bed to do 5 mile PT runs quite often in the military - and yup, you wake up a lot faster

 

hahahahahaha