Fiat TC Pulley Relations

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FiatRally
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Fiat TC Pulley Relations

Post by FiatRally » Wed Feb 19, 2014 11:38 am

Good day,

I am busy with finalizing my 1800 TwinCam Fiat engine.

I have changed the pulley on the crank and it is smaller and much lighter than the standard pulley.

I never had the waterpump pulley and do not know the standard size diameter.

The engine is full race spec and makes excellent power from 3500RPM upwards.

What would be the size relationship between the main crank pulley and the waterpump and alternator pulleys please.

I have a Bosch Alternator from a Fiat Uno 1400 that I would like to use.

Kind Regards,

Ernst
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FiatRally
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Re: Fiat TC Pulley Relations

Post by FiatRally » Thu Feb 20, 2014 10:18 am

I got the answers at:

viewtopic.php?f=4&t=1472#p7757

Lets hope the alternator will keep up!!

Thanks Guy!!
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FiatRally
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Re: Fiat TC Pulley Relations

Post by FiatRally » Thu Feb 20, 2014 11:41 am

According to information I could get from an article by Gates, alternators usually run at 3 x engine speed!!

3 x 8 000 RPM = 24 000 RPM

Lets hope the bearings on the Bosch alternator is up for the job.
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Urbancamo
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Re: Fiat TC Pulley Relations

Post by Urbancamo » Thu Feb 20, 2014 3:51 pm

Hi Ernst

Crank pulley to alternator ratio in ordinary engines is typically around 2:1 or bit more. Very commonly alternators will produce their max. output current when the engine is running from 2500-3000 rpms = typical cruising situation.
Typically suggested max revolutions for alternators are 12.000 rpms, with a peak of 15.000 rpms for short periods of time.

It's not the bearings, they will last. But the rotor is going to broke. If you run your alternator at 24000 rpm something is gonna blow up very soon ;)

For an example my friend has a full blown Toyota 4A-GE rally unit. Engine runs up to 9400 rpm (rev limiter) all the time in stages and typical rpms are 7500-8500. Years ago it had stock crank to alternator pulley ratio. Alternators kept dying in under 60 miles, it doesnt like to see near 20.000 revolutions. Now the ratio is highly reduced, it's something like 1,5:1 and now you need 1-2 alternators/season anymore. It's still runs bit too fast.

So my advice if your engine is going to spend it's time way higher than stock unit for long periods of time, alternator speed should be reduced.

T
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FiatRally
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Re: Fiat TC Pulley Relations

Post by FiatRally » Tue Feb 25, 2014 1:52 pm

Thank you very much for the helpful information.

I am now happy to make an alternator pulley and will do the calculations and manufacture.

Belt length will be easy to source.

Kind Regards
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Urbancamo
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Re: Fiat TC Pulley Relations

Post by Urbancamo » Tue Feb 25, 2014 2:22 pm

Nice, keep us updated what pulley ratios you ended up. We like pictures too.

TH
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FiatRally
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Re: Fiat TC Pulley Relations

Post by FiatRally » Mon Jan 19, 2015 5:35 pm

After a lot of thinking and trying to work things out in my uneducated mind I have reasoned the following:

Why change 2 pulleys and make the belt even shorter?

I left the waterpump and alternator pulleys as standard sizes. Then made the crank drive pulley smaller.

Our standard pulley on the crank was 148mm diameter, I have gone down to a 120mm diameter.

I am not looking at revving the motor much harder than 7700rpm. This is an 1800 engine.

The test will have to be in running the engine and seeing the results!
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Will01
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Re: Fiat TC Pulley Relations

Post by Will01 » Mon Jan 19, 2015 9:10 pm

Are you going to be running a synchronous (timing belt type toothed belt)?
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FiatRally
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Re: Fiat TC Pulley Relations

Post by FiatRally » Wed Jan 21, 2015 4:28 pm

No I will still run a "toothed" V-Belt for now.

Finding pulleys for running a wide belt is nearly impossible here in South Africa.

Our money is worth nothing, so buying from overseas is impossible. And getting it made is also to expensive.

Unless someone is prepared to "help" which is also not going to happen.

I just do the best I can with the little knowledge I have.

Regards and thanks for the interest!
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