Belt Tension, Howto

[foama]

The correct belt tension is determined by its resonant tone.
Just like a guitar string, the tone has a pitch proportional to tension.


Here is a quick and easy way of getting it 100% correct:

Pluck the belt firmly as in the picture below where it runs under the engine mount, just as if it were a guitar string. This produces a tone.

Play the audio file (below) for comparison, and adjust the belt tension until its pitch matches.

You may want to put the sound file on your mobile phone, for playing it when and where you need it.



MP3 audio file: mirage-Belt-tension-plucking-sound.mp3


Happy twanging
Foama







The correct belt for Mirage with A/C has 6 ribs and a length of 1240mm.
Some makers offer a length of 1238mm which fits just as good. Any shorter and it becomes difficult to install.

Part number 6PK1238 or 6PK1240 (non metric: 488K6)

Our cars were made adhering to universal (metric) standards as harmonized by the International Standards Organization (ISO). In the last three remaining non-metric countries, namely Liberia, North Korea, and the USA, the 6PK1240 may be sold as 488K6. See bottom picture, where the belt has both printed on it.


Picture of the OEM belt 6PK1240 (Type 488K6 in some non-metric countries)

[MetroMPG]

Audio file added to your post!

[mitsumi]

hehe thats nice! i can tune a guitar and see if i can tune a belt! lolz

[Fuelblender]

hehe thats nice! i can tune a guitar and see if i can tune a belt! lolz

Can you tune a fish? Haha, I couldn't resist...

[stecoop]

Over the last 45 years, I've done a lot of engine tune-ups; this is the first time I've heard of "tuning the belt". Unfortunately, I'm tone-deaf. Will I need to hire a piano tuner to check my belt tension?

[Eggman]

Will I need to hire a piano tuner to check my belt tension?

Consider using an audio frequency app for your phone.

[foama]

Over the last 45 years, I've done a lot of engine tune-ups; this is the first time I've heard of "tuning the belt". Unfortunately, I'm tone-deaf. Will I need to hire a piano tuner to check my belt tension?

Quote:

You may want to put the sound file on your mobile phone, so it can be played where and when you need it.

For MP3 audio file see first post

Happy twanging

[wellswebdesign]

Thanks, that's a great way to test the tension. Just being curious, and please don't take offense, but was yours measured with an MUT3 beforehand? How do you know the tension on yours is correct?

What's the procedure for adjusting the belt tension? That and your audio file would make an awesome DIY write up.

[foama]

Thanks, that's a great way to test the tension. Just being curious, and please don't take offense, but was yours measured with an MUT3 beforehand? How do you know the tension on yours is correct?

What's the procedure for adjusting the belt tension? That and your audio file would make an awesome DIY write up.

The procedure for adjusting the belt tension is totally self-explanatory. The recorded tone was from my car which has a belt with some 25 000km (15000miles) on it, so I can assume it is correct.

The manual says:

DRIVE BELT TENSION CHECK
CAUTION
* When checking the drive belt tension, make sure that
the engine is cold.
* Check the drive belt tension after turning the crank-
shaft clockwise one turn or more.
* Check the drive belt tension in the following procedure.
NOTE: For the vehicles without A/C, the check procedure is
also same.
Belt tension meter set (MB992080) MB992081 MB992082 AC507219AB
1. Connect special tool microphone assembly (MB992082) to special tool belt tension meter (MB992081) of special tool belt tension meter set (MB992080).

The manual continues to say the tension "when being adjusted" relates to a certain vibration (tone-)frequency when the tension is correct.

Since I have none of the mentioned metering equipment, I simply go by the tone as recorded when the belt was plucked as in the picture. Probably anyone not having ten left thumbs on his hands and not being tone-deaf can get it right first try without hassle.

[91cavgt]

I need to re-adjust the tension on my belt. Here lately it has been squeeling a lot when driving through water and it used to never do that. My Mirage is sitting at 33,000 miles so it is probably due.