[mpesik]

Hello.
I have a question.
What is the pulling tension on a Timing Belt at Idle and at maximum RPM?
This is on a 4 banger.
Approximate is good enough.
Curious.
Thanks.

 

[Vulcan Grey]

why would anyone want to know this, let alone actually know this?

What are you trying to figure out?

 

[mpesik]

why would anyone want to know this, let alone actually know this?

What are you trying to figure out?

Cause I'm Curious.

 

[mpesik]

Does anyone have at least an idea about this?

 

[MidLifeZ]

twelve, yeah, twelve...

 

[Type82]

Timing belt tension cannot be determined by 'pulling' on the belt the way 'V Belts' were checked back in the day.

Your best bet is to have a qualified repair shop replace the belt for you,this is one motor not to be 'guessing' with.

Robert

 

[carbuff]

I think Mike (who looks really young in his new Avatar, SEE, we noticed!) wasn't talking about the static tension spec when the belt is replaced. I think he wanted to know how much pulling force the crankshaft applies to the cams during operation (idle and max revs). Thus, an approximation of needed TB tensile strength?

I've never seen specs for THAT on ANY cars I've worked on, or timing belts I've purchased. So, I'll have to with MidLife's answer. LOL.

 

[MidLifeZ]

the only car I have worked on which did this way, albeit not while engine running, was Z32 300ZX. When changing timing belt you measured the deflection with a ruler to set tension

 

[carbuff]

When changing timing belt you measured the deflection with a ruler to set tension

That is exactly the way the old Lotus/Burroughs or Krikit TB tension gauges worked, before frequency specs became commonplace.

But again, that's static measurement...:shrug:

And the old published Lotus specs don't apply to the new, improved blue Gates Racing timing belts, anyway.

 

[jtrealty]

I do not know that there is such a #. It is a LOT more complicated than that anyway. As the camshaft is rotated it gets harder as you pull against the lobe and open the valve but after the valve is opened the camshaft is now being rotated by the force of the spring trying to close the valve so the timing belt is now "holding back" the camshaft. It is a very dynamic process with all of the valves opening and closing and at high speeds. All kinds of vibrations and harmonics build up. It was determined that just measuring the deflection of the belt was not an accurate enough way to tension them. You also have to consider that once the motor gets hot the belt gets a lot tighter. That is why they went to measuring the frequency of the belt, in effect "tuning" the belt like a string on a piano. It is a much better measurement of the tensile stress on it. It also must be done at a particular position of the motor so the valves are not imposing loads one way or the other on the belt. Too little and the belt could jump a tooth, too much and you damage the bearings and stretch the belt. A LOT of engineering goes into this. You would be best advised to go with the manufacturer's recommendations and leave it at that.

 

[carbuff]

A LOT of engineering goes into this. You would be best advised to go with the manufacturer's recommendations and leave it at that.

Or, just go with my NEW value, which I deem to be "42".

Phrases from The Hitchhiker's Guide to the Galaxy - Wikipedia, the free encyclopedia

"The Answer to the Ultimate Question of Life, the Universe, and Everything (42)"

...a group of hyper-intelligent pan-dimensional beings demand to learn the Answer to the Ultimate Question of Life, The Universe, and Everything from the supercomputer, Deep Thought, specially built for this purpose. It takes Deep Thought 7½ million years to compute and check the answer, which turns out to be 42. Deep Thought points out that the answer seems meaningless because the beings who instructed it never actually knew what the Question was.

 

[esprit888]

the only car I have worked on which did this way, albeit not while engine running, was Z32 300ZX. When changing timing belt you measured the deflection with a ruler to set tension

This is a very common TB method of measuring, the M100 lotus élan/isuzu impulse RS turbo is the same but just like the esprit it's subjective in that you apply x pounds of pressure downwards between the two cams and measure the deflection with a ruler. Well x pounds with a double espresso is not the same as x pounds with a hangover
Colin

 

[Vulcan Grey]

The answer is somewhere between imperceptibly infinite and infinitesimally small, but probably closer to the integral of the ever changing slope of the ratio of the cam profile vs spring constant.

This number is so closely guarded that only a trained professional timing belt enginerd would ever be given the answer after completing a series of differential equations that solve the answer to what is the meaning of life, the universe, and everything. Only then would the answer to "What is the pulling tension on a Timing Belt at Idle and at maximum RPM?" be handed down to the enginerd on a silver platter.

 

[Vulcan Grey]

If you want to check tension or set tension on an Esprit with the round belt tooth (HTD profile) like your 89.

Then this is the method that you should use.

cell phone frequency tensioning for me!


I use the app called "Speedy Spectrum" on my Android phone. Works great for finding the first fundamental frequency of the belt.

https://docs.google.com/open?id=0B2...YjEyLTgyZTAtYmI5NjE4MjgxMmRm&authkey=CO_S1NoE

Engine is cold and at 30deg before top dead center (30 BTDC).

Microphone is placed close to the belt, as close as possible. Reach around the front of the engine and strum the belt in the middle between the intake cam pulley and the oil pump pulley. Strum it like a guitar string, do not let the finger touch the belt after the strum, slip the thumb off quickly with one motion.

This is for cars with the round tooth HTD belts only.

Standard software settings, though make sure to turn on peak hold and enable peak hold overlay. you can zoom in on the screen near 100Hz, but I look at the peak hold number in the upper right of the screen.

30 BTDC

Note CAM dots are slightly mis-aligned and not centered on the axis at 30BTDC

Speedy Spectrum at 103Hz on my HTC EVO 3D Android phone

Thumb technique

 

[OnAir]

^ Excellent post Travis.:up: Is the procedure similar for V8s?

 

[Vulcan Grey]

Yes the V8 procedure is similar, though the spec is slightly different. Definitely check your manual.

 

[mpesik]

I think Mike (who looks really young in his new AvataThat'sr, SEE, we noticed!) wasn't talking about the static tension spec when the belt is replaced. I think he wanted to know how much pulling force the crankshaft applies to the cams during operation (idle and max revs). Thus, an approximation of needed TB tensile strength?

I've never seen specs for THAT on ANY cars I've worked on, or timing belts I've purchased. So, I'll have to with MidLife's answer. LOL.

That's It !:clap:
And I thought it was twelve, all this time!?