Vifa

Hi there,

I hope you can help settle a discussion I am having with a friend of mine. I was around when he was revving up his car with a cold engine. I told him revving up a cold engine was a terrible thing to do. He said no, nothing seriously would happen.

At least I have always been told revving up a cold engine is a terrible thing to do. But with my lack of knowledge on this subject, I am not sure if anything will happen at all, or .. Well, please settle this. Btw, he is reading this thread too.

Porsche964FP

IMO

If it's a car with engine management the ecu will put the revs automatically to 'warm' the engine. If the car with an ecu doesn't automatically do this I would say the car needs some adjusting.

If however the car doesn't have an ecu then setting a reasonable rev point will 'warm' the engine to a point where one can then ease off the throttle to a steady idle without the engine stalling. This would be true for example for an old beetle. This is why the choke on older cars was invented - to raise the revs until the engine reaches a good operating temperature/ a natural idle.

Golden question - what car was he doing this to?

scped

I am far from an expert, but here are 2 opinions:

1) I have heard NPR's Click and Clack say there is no reason to warm up a car - start it and drive

2) I have heard (sorry - do not recall the source) that it is important to warm up a performance engine - the oil reaches the correct viscosity and the temperature of the metals stabilizes so the (cylinder, valve, ...) tolerances are correct for hard driving.

I am curious what others have to say

ScottR

Once or twice probably won't hurt but it's my understanding that it's not good to do regularly. It can cause premature wear of certain components like pistons and cylinder walls through excessive friction. Things haven't warmed up and the oil has not found it's way around. In the same way we don't jump out of bed and start running around.

And because it's not running at temperature it's also not burning fuel properly, which is why emissions tests are done on a warm engine. Thus you can get a build of gas in the cat (if you've got one on) and exhaust system, which can ignite and cause problems

And finally, every car manual out there will tell you to let the engine warm up before taking it over a certain rev range. Surely they can't all be wrong?!?

EDIT: When you say revving, what was he revving it to?

Vifa

It is a '92 964 Carrera 2.

Well, he was demonstrating the sound. He was of course not redlining it, but he said he reached around 5500 revs during the 10 secs 'demonstration'.

I believe the exact question of our discussion is whether or not any damage could have happened. I say plausible, based on what I have always been told - but I have no knowledge to settle the discussion.

Vifa

That makes sense.


Yes ! I always try to keep the revs under 3500 before the engine is warm when I drive mine.

Vandit

Yea, I'm definitely not letting the revs go past 3k-ish until it reaches decent operating temp (2nd line of the 2 close lines at the bottom of the gauge).

Porsche964FP

WOW.

On a 964 on start up the ECU dictates automatically an ideal rev to bring the engine up to temperature.

It specifically states in the user manual and by many sources on here that the car should not be let to idle ( bad for cams ), that as soon as you start up you drive the car in order to bring things up to working temperatures.

I strongly suggest building temperature up slowly and progressively through different gears over roughly a 30 minute period before reving over 4,000 revs.

In continuation of the aforementioned It's also not advisable to let the car idle in traffic for long periods of time. Bring up the revs slightly or switch it off and wait for traffic to move on.

I'm sure a lot of this is a 'no brainer'.

RW964

IMO this is what I do I start the car and let sit for 30 sec and then drive through the hood in 2nd gear with the windows down just to listen to the pipes and let the neighbors look and say WOW !!!

Porsche964FP

It's also worth turning the ignition, let the fuel pump start and then turn over.

Smokin

Yup... That is pretty much what I do. I have always kept it below 4k until it is right at operating temps.... 30 minutes seems a little long to me... Mine usually gets up there in 5-10 minutes... But to each, his own.

Bearclaw

5500 on a cold, unloaded engine? Really, really dumb.
He hasn't allowed the lubricant to come up to temp, nor the moving parts to heat up and use up some of the tolerances that have to be built in, to allow it to operate correctly.
As folks here have said, the correct way is to start it up, make sure you have good oil pressure for 10-30 sec. (depending on ambient temp) at no more than a fast idle, then move off *moderately*, until the oil has time to sufficiently heat up.
A friend of mine has an M5. The manual states 'keep RPM below 3300 until oil temp. reaches 50*C'. There's a reason for a recommendation like this.

Your friend's engine will a really BIG, impressive sound one of these days - and the, silence.

goofballdeluxe

I believe somewhere in the Porsche owners' manual there is a blurb about not revving the engine to higher RPMs until the engine is at operating temperature. I bet it's there for a reason.

I'm sure if you break this rule every now again, say, to avoid an accident while driving down the street, it woudn't do any harm. But as mentioned above, revving any engine that's cold to 5K-6Krpms or higher on a regular basis is not a good idea.

When you first awake from sleep do you get out of bed and instantly run 5 miles? Same logic applies.

PNine64

I agree. My 30 minute drive to work would have to end with me drifting into the parking lot now that it's "finally" warmed up.

boxsey911

The cynical side of me suspects that the Porsche line in their manuals about driving off straight away (and not leaving the car to idle for a few minutes) is to keep the environment lobby happy and nothing to do with mechanical sympathy.