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Engine related: Octane Measurement

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Old 11-09-2018, 07:24:08 PM
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Elden DuRand Elden DuRand is offline
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Default Re: Unsure where to post this. Engine related.


That's what I'd do. If you build the parts the customer's spec, especially if they are better than the presently available parts, you should be all right.

Some kind of incoming inspection and approval by the customer and sign off on the invoice would be good.

Originally Posted by Tanner Remillard View Post
Sounds like they need to give you blueprints with tolerances and have a quality control inspection on their end that they sign off on, making them liable for anything that wasn't right. That way you're just the guy making the parts from what they told you to do.

Take care - Elden
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Old 11-09-2018, 07:45:34 PM
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Reed Engine Reed Engine is offline
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Default Re: Unsure where to post this. Engine related.

The company that owns the engine now is called Compass.
Wake up and smell the Fool-Aid.
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Old 11-09-2018, 08:07:14 PM
Mikey NY Mikey NY is offline
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Default Re: Unsure where to post this. Engine related.

sounds like cheap Chinese parts supplier . Maybe harbor freight
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Old 11-13-2018, 11:24:49 PM
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Thumbs up Re: Engine related: Octane Measurement

Some cool reference;


Okay, so... there's some basic rules about measurement and instrumentation that many people misunderstand, and since I'm in the metrology industry, I'll share some basics here:

To measure something, one needs not some finite, unobtainable ultimate precision...

You only need a predictable and repeatable method, where controls are known, where variables are incremented, and where ancillary circumstances can be properly compensated for.

The operating principle of this machine is NOT complicated- it's an engine, and it has variable displacement. It doesn't actually measure OCTANE. It measures the PREIGNITION POINT of a fuel/air mixture.

The CONSTANTS... are air and fuel temperature, combustion chamber temperature, ignition timing, and operating speed.

The variables are: Fuel quality, and compression ratio.

The output: Audible engine knock.

How do you make a 'variable compression ratio' on an engine? That's extremely easy- you build an engine that has the HIGHEST compression ratio that you'd expect to need (in this case, John's page says the F1/F2 goes to 18:1 CR... so build it to 20:1 with just enough clearance in the chamber for valves to operate. To go LOWER, have a series of chambers of different sizes, with hand-valves that allow you to increase the amount of volume in the 'squish zone', such that the resulting compression ratio is substantially lower... down to 4:1.

A single-cylinder diesel engine is a shoe-in for this circumstance... just need a cylinder head fitted for spark ignition. Note that the spark plug electrode will be the de-facto 'hottest' place in the chamber- this is where preignition will START.

To test the preignition circumstance, simply start the engine, allow it to warm to it's typical temperature, then increase the CR by closing off the hand-valves of the ancillary chambers 'till you hear preignition. To 'calibrate' your measurements, use a fuel sample that was 'tested' and qualified up against another instrument already. On your engine, note the temperature and compression ratio under which you found preignition to occur.

From that point on, any fuel character that 'matches' will be of the same fuel quality as your test sample.
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