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Nervous about my timing belt tension
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Mon Jan 29, 2018 4:14 am    Post subject: Nervous about my timing belt tension Reply with quote

I mean to give the old belt a twist before I took it off to "calibrate my twister" for that 90 degree twist method, but I forgot. So I ordered this Krikit thing from Gates, but it says it's for v-belts. Is this the same thing people are using? Or is there a similar device for toothed belts? If there is, I haven't been able to find it.

If it is the same thing...what tension am I supposed to use? Even Haynes says to use the 90 degree twist method.

Finally...I saw a post a while back about tensioning to pitch when you pluck it like a string. I can get a pretty consistent pitch measurement when I do that, I just don't remember what the correct value is.

For what it's worth, I can just twist the belt 90 degrees...maybe a bit more if I really put some effort into it. I just fear that's too tight for some reason...
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-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1556
Location: MI

PostPosted: Mon Jan 29, 2018 5:58 am    Post subject: Reply with quote

I seem to always put mine on too tight and then back it off a bit after it's running and I can tell..

If it's too tight I will hear it, it'll sound like a toothy wine.. Reinstalling the belt I back it down till I just can't hear it or just barely.. With a brand new belt I'd back it down till I can only just hear it a bit and it'll wear in a little..
But I don't run a belt guard so adjustments are easy..

I can twist the belt too much by hand, probably could even if I maxed out the tensioner..
For a smaller guy I have strong hands from a lot of hand clutch and brake when I was young and ofcourse spinning a lot of wrenches..

I don't know what anyone else has to say about this sound method but I'd be interested to hear about more proper or better ways of doing it myself..

Putting a new cambelt on is one of my next steps, can't seem to find the baggie of my stripped TB parts ATM..
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Mike9311  



Joined: 14 Dec 2004
Posts: 661
Location: Chicago-ish

PostPosted: Wed Jan 31, 2018 1:22 am    Post subject: Re: Nervous about my timing belt tension Reply with quote

bureau13 wrote:
I mean to give the old belt a twist before I took it off to "calibrate my twister" for that 90 degree twist method, but I forgot. So I ordered this Krikit thing from Gates, but it says it's for v-belts. Is this the same thing people are using? Or is there a similar device for toothed belts? If there is, I haven't been able to find it.

If it is the same thing...what tension am I supposed to use? Even Haynes says to use the 90 degree twist method.

Finally...I saw a post a while back about tensioning to pitch when you pluck it like a string. I can get a pretty consistent pitch measurement when I do that, I just don't remember what the correct value is.

For what it's worth, I can just twist the belt 90 degrees...maybe a bit more if I really put some effort into it. I just fear that's too tight for some reason...


...just answering the frequency part...

http://www.924board.org/viewtopic.php?t=42614&postdays=0&postorder=asc&highlight=frequency&start=15

This car is still running just fine with the belt setting described in the above thread

This was done with an iPhone and a guitar tuning app. Just got the phone close and plucked the same section you twist.
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Wed Jan 31, 2018 1:34 am    Post subject: Reply with quote

Perfect! That's the exact thread I remember, for some reason I couldn't find it. Of course, I don't remember what the frequency I measured was, but I can easily go back and check (I took just about everyone's advice and left off the cover)

The other comment in that thread is interesting....everything I've seen about the twist method says 90 degrees...if I'm supposed to twist it to 180, that seems loose. Definitely looser than my belt right now...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Mike9311  



Joined: 14 Dec 2004
Posts: 661
Location: Chicago-ish

PostPosted: Wed Jan 31, 2018 1:42 am    Post subject: Reply with quote

bureau13 wrote:
Perfect! That's the exact thread I remember, for some reason I couldn't find it. Of course, I don't remember what the frequency I measured was, but I can easily go back and check (I took just about everyone's advice and left off the cover)

The other comment in that thread is interesting....everything I've seen about the twist method says 90 degrees...if I'm supposed to twist it to 180, that seems loose. Definitely looser than my belt right now...


Off the top of my head 90 degrees sounds right not 180 but you will know when its too tight since it will hear it as mentioned by FastEddie

Better set too tight, listen and back it off a bit. CHeck the frequency too if you can and go from there
_________________
1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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CÚdric  



Joined: 27 Aug 2004
Posts: 1732
Location: Sweden

PostPosted: Wed Jan 31, 2018 2:25 am    Post subject: Reply with quote

Even if ive done it a couple of times its still hard, twist method sucks hard, it so easy to get it to tight. Frequency is so much better. Set it at 85hz last time with help of a frequency analyzer on the phone. I wish there were a workshop number to work with
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Mike9311  



Joined: 14 Dec 2004
Posts: 661
Location: Chicago-ish

PostPosted: Wed Jan 31, 2018 6:14 am    Post subject: Reply with quote

CÚdric wrote:
Even if ive done it a couple of times its still hard, twist method sucks hard, it so easy to get it to tight. Frequency is so much better. Set it at 85hz last time with help of a frequency analyzer on the phone. I wish there were a workshop number to work with


So we are close...this was mine from the other thread

"New belt (931) with a few hundred miles on it so far... F2 (87Hz) "

We have our running baseline so far 85-87 Hz

As far as a workshop number, we might be able to contact the supplier and I think Conti is one that still makes the belt. They might be able to provide a number? Like I stated before for Ducati's, the suppliers actually published the number.
_________________
1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Thu Feb 01, 2018 8:00 am    Post subject: Reply with quote

FWIW I sent an email to someone at Continental. I'm sure it will go nowhere, but you never know...
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Mon Feb 05, 2018 3:18 am    Post subject: Reply with quote

For what it's worth, my twist method attempt had it set at 124 Hz. I backed it down to about 85 Hz. Honestly, how is this not the best method that everybody uses everywhere?
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Mike9311  



Joined: 14 Dec 2004
Posts: 661
Location: Chicago-ish

PostPosted: Tue Feb 06, 2018 2:09 am    Post subject: Reply with quote

bureau13 wrote:
For what it's worth, my twist method attempt had it set at 124 Hz. I backed it down to about 85 Hz. Honestly, how is this not the best method that everybody uses everywhere?


exactly

The first time I did this was on a Ducati 748 which then saw near 13K on the track no issues.

This method doesn't lie and isn't affected by our own paranoia of wanting to get this right by feel.

Check it again after it runs for a while. It may relax a bit
_________________
1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Thu Feb 08, 2018 12:02 am    Post subject: Reply with quote

Indeed the twist method is not accurate at all.
There is no way to calibrate for any individuals strenght or effort. I must have strong hands as can twist it throuh 180*, although not real easily, while another person may go blue in the face achieving 90*.

That`s probably the reason why porsche came up with their P9201 tool, it is calibrated in a specified unit of measurement and constantly repeatable. Same with the more basic Gates Krikit option. There are a few different models & ranges and are suitable for various size V belts, PK and other series multirib belts. Also works fine for timing belts where a figure is specified. I use the blue one that IIRC has the lowest range, down to 30#.

Many 944 & 928 guys use the Krikit sucessfully. There is no spec of tension or frequency for our 2L engines. IIRC the 944 timing belt spec is 30 or 32 Lbs and apparently also proven compatible on our engines. Recall reading some much earlier threads here or RL maybe 10 years ago, before getting the tool.

Mike9311, I looked into measuring frequency some time ago after that other thread. Don`t have a guitar tuner or iphone so downloaded Spectrum Analyzer Pro and some other useless program on my D630 tuning laptop but could not get any specific peaks at all. Notice you used a similar laptop so would like to know what software you used?

bureau13, As you also have the Krikit tool it would be interesting for someone to record and compare various tension readings with their resonant frequency. Just statically of course, don`t need to start the engine.
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Mike9311  



Joined: 14 Dec 2004
Posts: 661
Location: Chicago-ish

PostPosted: Thu Feb 08, 2018 4:44 am    Post subject: Reply with quote

I was using it to build home speakers at the time.

https://www.trueaudio.com/rta_abt1.htm

It may be cheaper to buy a cheap guitar tuner off ebay

You can always look for speaker testing equipment but its overkill. For example...

https://www.parts-express.com/Search.aspx?keyword=testing&sitesearch=true


I am so glad I found this method back in the day. I even successfully pulled off the "twist method" on a 944S2 a long time ago but I can say I never liked it.

The more of us that try it and provide feedback the better.
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Thu Feb 08, 2018 5:41 am    Post subject: Reply with quote

I will try to do this over the weekend.

RC wrote:
bureau13, As you also have the Krikit tool it would be interesting for someone to record and compare various tension readings with their resonant frequency. Just statically of course, don`t need to start the engine.

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 70
Location: South Florida

PostPosted: Mon Feb 12, 2018 5:25 am    Post subject: Reply with quote

OK, for what it's worth, when I remeasured via the pitch method, I got 93 Hz, and on the Krikit, right at the low edge of the range, which is supposed to be 30 lbs.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Thu Feb 15, 2018 12:40 am    Post subject: Reply with quote

Thanks bureau13 for measuring that.
The lowest graduation on the Krikit is 30#, which is where I set mine at.

Tried Frequency Counter android app briefly but without much sucess at all. Got a wide variety of different readings even on the much tighter 6PK blower & alt/WP belts. Intend playing around more another time with the settings for backgeound noise, time period & whatever and will post if I get some repeatable results.
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Allan @ DTA wrote:
I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards
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