Racing Engine On Start Up

wells service · #1 (**permalink**) 12-21-2007, 12:23 PM

The instructions in the new car manuals years ago said, Do not start the engine and immediately race it. wait until the oil pressure comes up(10 seconds). now drive easy until the engine is warmed up. Varying engine engine rpm is best for warming up the engine.
Now a days when you start a car/truck the computor (especially tundra) the engine races to 2000 rpm then slows slowly and holds higher rpm for 3 or 4 minutes. Why does the Tundra race so high at start up. At the Sema show in 2002 i found a toyota truck engineer and ask why they put on a 1930's exhaust manifold on the 4.7 engine. He looded embarssed and said that was the only way they could get the cats to flash (heat up and start working) quickly. they also raced the engine to light the cats quickly. they compensated by recommending 0-20 or 5-20 oil instead of 5-30 or 10-30. The thinner oil quickly flows to the bearings, camshafts, & rocker arms and also slightly increases corporate MPG average. now you know the rest of the story.

TundraBay · #2 (**permalink**) 12-21-2007, 12:27 PM

That's very interesting. I wondered why the engine revved so high on start up. I thought it might have something to do with getting temperature up quickly. So that's it, catalytic converters need to be warm to work properly; makes sense. And with Synthetic low-weight oils there's better cold lubrication.

djb383 · #3 (**permalink**) 12-21-2007, 12:43 PM

Our Tundra doesn't rev any more than our other vehicles do when started cold but that old school belt driven radiator fan on the Tundra absolutely roars and is obnoxious. Our other vehicles have electric radiator fans which don't come on when the engine is cold. If the Toyota engineers wanted quick heat, why create a tornado of wind under the hood when the engine is COLD?

override · #4 (**permalink**) 12-21-2007, 01:08 PM

I wondered the same thing as to why they did not put an electric fan... my borther-in-law is a mechanic and explained to me that the power and torque in the V8's is so high now days, that a belt driven clutched fan makes little to no difference in your end power to the wheels...

the belt fan is more reliable to operate all the time then an electric fan that could short out, sensor go, etc and not turn at all... with the size of the motor, it would over heat quickly. The noise is anoying, but in the long run I prefer the belt driven.

If you are super picky on getting every little ouce of power, swap it out... I don't race my truck on the track, so there is no need for an electric fan.

djb383 · #5 (**permalink**) 12-21-2007, 02:17 PM

.............then how come the Chevy/GMC p/u's, Tahoes and Suburbans have gone to electric radiator fans and I think Dodge has also. There are millions of vehicles on the road today with electric radiator fans and reliability is a non-issue.

blackgts2002 · #6 (**permalink**) 12-21-2007, 02:23 PM

Quote:

Originally Posted by djb383

.............then how come the Chevy/GMC p/u's, Tahoes and Suburbans have gone to electric radiator fans and I think Dodge has also. There are millions of vehicles on the road today with electric radiator fans and reliability is a non-issue.

If so reliable, why not buy one?

JBK23 · #7 (**permalink**) 12-21-2007, 02:25 PM

Quote:

Originally Posted by djb383

.............then how come the Chevy/GMC p/u's, Tahoes and Suburbans have gone to electric radiator fans and I think Dodge has also. There are millions of vehicles on the road today with electric radiator fans and reliability is a non-issue.

And that is why they keep breaking down too and why people buy the tundra's stick to the belt the old fashion way is much better.The less money you have to spend on repairs.

djb383 · #8 (**permalink**) 12-21-2007, 02:35 PM

There's a couple of DUH answers.

TundraBay · #9 (**permalink**) 12-21-2007, 02:47 PM

Electric cooling fans came out initially in transverse mounted engines. Any idea why they are now being put on longitudinal mounted engines, where there's a serpentine belt there in the front anyway? Would seem an unnecessary added expense, mechanical and electrical stuff to go wrong. Unless there's some other benefit??

can't stop spinning · #10 (**permalink**) 12-21-2007, 03:23 PM

2000rpm is nothing. Last week when I started my corolla, it went up to 2600rpm... And that was after is dropped 300rpm when I let the clutch out

djb383 · #11 (**permalink**) 12-21-2007, 09:07 PM

Electric fans provide high air flow thru the rad, thus providing better cooling, at slow vehicle speeds or when the vehicle is stopped. At highway speeds a fan shouldn't be needed due to the amount of airflow thru the rad, so the electric fan shuts off. Belt driven fans place a constant load on the engine, slow down engine warm-up, are noisy and give reduced airflow at slow vehicle/engine speeds. Belt driven fan clutches have been known to fail.

I bought the best-bang-for-the-buck p/u available today, the Tundra. With just a few tweeks here and there (electric rad fans, etc.) and your talking about the PERFECT p/u.

Personally, I think all the manufacturers get together behind closed doors and say "here's the vehicle that we all must agree to NOT build"........and that's the perfect vehicle.