Whistler being used at Atlanta ST?

P

Protech Racing

Well-known member
My engine is old and weak . But the compression measures at 11.6 /1. Before I build the good engine, I would like to match the whistler opinion.
Thanks,MM
 
I'm not understanding your question.
How does the use of a whistler at one event or another affect the compression ratio we build our motors to? CR is a clearly objective value, regardless of the accuracy of the method used to measure it.
 
chois":2v189oic said:
I'm not understanding your question.
How does the use of a whistler at one event or another affect the compression ratio we build our motors to? CR is a clearly objective value, regardless of the accuracy of the method used to measure it.
Click to expand...
I believe his intent is to compare the whistler readings to his known 11.6:1 ratio so that his next engine build will be within any tolerances of the whistler's numbers so he's sure to be legal if checked down the road.
(holy Awful Sentence Structure, Batman! but I don't know how to say it any other way.)
 
Matt93SE":3sck92yj said:
chois":3sck92yj said:
I'm not understanding your question.
How does the use of a whistler at one event or another affect the compression ratio we build our motors to? CR is a clearly objective value, regardless of the accuracy of the method used to measure it.
Click to expand...
I believe his intent is to compare the whistler readings to his known 11.6:1 ratio so that his next engine build will be within any tolerances of the whistler's numbers so he's sure to be legal if checked down the road.
(holy Awful Sentence Structure, Batman! but I don't know how to say it any other way.)
Click to expand...

OK - but since CR is actually determined by physical measurements, and whistler is just an approximation - I still don't get it.
Add to that the fact that most folks report that a whistler tends to read lower than actual CR, and the move is to build the motor to the spec line CR (or below) just like you would any other time.

Maybe there are instances of whistlers reading higher than actual that I've not been hearing...

From the GCR Appendix F:
Compression Ratio – Reciprocating engines: the ratio of the sum of swept plus unswept volumes to the
unswept volume. Rotary engines: the ratio of the largest to the smallest volume of the working chamber.

From the GCR Appendix G:
1. FACTS AND FORMULAS TO BE USED AT ALL SCCA EVENTS
...
Compression ratio = (V1 + V2)/V2
Where V1 is total volume of one cylinder: sum of swept plus unswept volumes.
V2 is enclosed volume existing in a cylinder/cylinder head with the piston at its closest approach to the cylinder head.

2. MEASUREMENT STANDARDS
...
12. Compression ratio is absolute maximum

There is no mention of whistler in the GCR.
Again - if I'm uninformed and the whistler actually has a tendency to read high, I understand building to the whistler to avoid having to tear down. Maybe I'm under informed on this.
 
chois":ukb0htjm said:
Add to that the fact that most folks report that a whistler tends to read lower than actual CR, and the move is to build the motor to the spec line CR (or below) just like you would any other time.
Click to expand...
It's well-known that Whistlers tend to indicate around 1/2 point low. The device was well-used as a check in the past.

I used it extensively in tech during the 2015(?) regional season to test it out and learn it, as I'd heard it was going to be used at the Runoffs. It was voluntary to come see me on it. I discovered that almost all Miatae were showing about 1/2 point low but curiously a couple (just a couple) of higher-end drivers were coming in spot-on; both had the same pro engine builder. I waved it off as the vagaries of the device, knowing that the device would only be used as a pre-test and no car would be tossed based solely on that reading.

But then came "Whistlegate"; do you remember it? I forget what year it was - Daytona 2015? - where all pointy-end Miatae were coming in dead-nuts to the Whistler reading. But then the heads were taken off and it was measured manually they all came in 1/2 point high (there or thereabouts). Wasn't that one of the years when they were all tossed?

So, they were "building to the Whistler".

Now, I'll grant you the details on that whole thing may be wrong; I was not involved in tech at that Runoffs. But I've pretty much put aside any thoughts of using the Whistler as anything more than a macro-test for macro cheating. And if you're within a half point or less of your limit, you may find yourself being subjected to head removal (supps permitting).

I don't recommend building an engine to the Whistler. Been done, sets off big flags, and it got caught.

GA
 
Protech Racing":30al2i6a said:
I got whistled at 9.4 once.
Click to expand...

Which kinda just reinforces my question then. Why do you care if they are using the whistle at RAtl? Are you concerned that your competitors will be running illegal CR?
 
The Whistler was originally designed to check a 350 CID engine. My experience has been that is very accurate at that displacement. My experience on smaller engines is that it will usually read low on smaller displacements. As it has been stated, building to Whistler measurements may bite you.
 
If your motor pops any of the piston above the block deck especially if where the edge of the piston meets the block, the whistler will give you a low reading. I whistled 4 SM motors at the 2022 Runoffs all with professionally built motors and the whistler matched the build sheets.
 
Did a little searching for one of the gory details when using the whistler. With the valve cover on the whistler reads low as compared to same engine being cc'ed. Someone suggested the procedure for whistler use specified to remove the valve cover. The procedure specifies you may remove the valve cover, but does not say you shall remove the valve cover.

Jim, for 2022 tech did you have cover off? I'm betting off.

Chris, https://cdn.connectsites.net/user_files ... 1432153407

Per my reading it seems as tho the whistler is a red flag, if the reading is high, cc the engine.
 
I have determined that you must have the valve cover off where the spark plug opening is recessed. The whistler uses tones and apparently the narrow area on some valve covers altered the reading. Yes, all came to light just before the runoffs and everyone who had been building to the whistler had to change head gaskets.

An engine builder just happened to whistle a Miata engine with the valve cover off and then decided to double check his reading after he had installed the motor. He got about a 1/2 point different reading. So, he pulled the valve cover and the reading went back up. So, he called me and told me what he had found. So, that next weekend at Daytona, I whistled a wide variety of SM cars and sure enough, the reading went up when the valve cover was pulled. There were several engine builders there and after discussing with them, I was confident that the reading were more accurate with the cover removed. The rest is history.

i have also discussed with Katech the lower readings that I have found on motors where the piston is above the block deck. They never really said too much about it but after several years of whistling motors at the runoffs and then actually cc'ing them, I'm confident this causes low readings.

So, NEVER build a motor to the whistler. And rest assured that tech will never use the whistler to determine a motor is not compliant. It is only quick check tool. The real determination is actually measuring everything. In all the years that I have whistled motors, only 4 times have drivers/engine builders decided the whistler was correct and a tear down not needed, 2 at the Runoffs with motors pieced together (one also had over size valves in borrowed head) and not even close on CR and twice at the ARRC where the engine builders admitted they made mistakes.
 
We'll come by for a puff if we dont blow up .
Thanks,MM

Maybe we could back up the puffer with an actual burette and CC the chamber. Thats is a useable value and should be the last measure for compression. Easy peasy.
Jack or tip the car so that the plug is up, Roll the piston up on compression. Drop in some ATF oil measuring the amount, shake it a little . Count. Do some simple math and done.

The method of measuring all of the pieces and adding them up has way too much tolerance stack .
 
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