61 replies to this topic

[Johnny D]

If you read this ^, you never answered.

Nuff of your  for me.  
 

 

J~

[Jim Drago]

My profile title kind of says the same thing as Different Ways to Skin a Cat, Different Strokes for Different Folks. If your engine ever blows a higher ratio than allowed, what's you next move???
On my engine, anything other than head off to measure is a go, no-go gauge. No-go and the head comes off.

if you are whistled, there is a procedure to follow. Print it out.. If not followed and signed by competitor and tech official, you could whistle 11:1 and not be dq'ed, or it would be reversed on appeal.

Assuming the procedure is followed and your compression limit is 9.0:1, they typically will give you 9.1 without writing it up. If it is .2 or more off, you will be found non compliant and an RFA will be written.

If the procedure is followed, and you measure over, save your money and don't bother pulling the car apart, you will measure worse. The whistler is EXTREMELY ACCURATE when used correctly. It is not hard to use correctly either. There is also a little fudge built in specific to the miata and the way the tool is used in impound that favors the competitor by .15 or so. So if you whistle 9.6, you will measure about 9.75:1 . If you know you are "right" pull it apart, but if whistled correctly and your over.. you or your machinist made a mistake

On the whistler.. While you could get a pretty good idea on over bore with it.. You could even try and write an RFA, but it would never stick. You can't use the whistler to measure bore.

As far as making a tool. The "tool" is not bad now. The issue is that that you are using a tool that is made to get a general size on bore and measure down to the last .001.. No other tool will be completely accurate less pulling the head.

I'll make it easier.. Take a $12.00 harbor freight Cen-tech digital caliper. Measure something approximately 3 inches long. See if you get the same measurement to .001 each time? NO WAY! Just imagine then adding in the bore tool and the tolerance for error there. A VERY qualified machinist could do this within .004-5, anyone else would struggle to be accurate within .010

Jim

[Bench Racer]

On the whistler.. While you could get a pretty good idea on over bore with it.. You could even try and write an RFA, but it would never stick. You can't use the whistler to measure bore.

As far as making a tool. The "tool" is not bad now. The issue is that that you are using a tool that is made to get a general size on bore and (not) measure down to the last .001.. No other tool will be completely accurate less pulling the head.

I'll make it easier.. Take a $12.00 harbor freight Cen-tech digital caliper. Measure something approximately 3 inches long. See if you get the same measurement to .001 each time? NO WAY! Just imagine then adding in the bore tool and the tolerance for error there. A VERY qualified machinist could do this within .004-5, anyone else would struggle to be accurate within .010

Jim

I deleated the compression ratio comments. Don't want to talk apples and oranges and call them peaches. Point one underlined above, I agree 100%. Point two underlined above, with the existing tool or the what I'll call an improved tool I would suggest only the uninitiated would believe he/she could measure repeatly to a few thousands. My entire point of yaking about the existing spark plug bore tool is a take off of someone that suggested improvement to the existing spark plug bore tool as in taking out some of the variability. My goal is to fab an improved tool and see what it's accuracy/repeat capabilities are. An upmanship project. Point three underlined above, not that gullible, I'd use my 3 inch micrometer. If en ya got something with a tolerance of .001 ya damn well better use an appropraite measuring tool and a caliper is not that tool.  

[Jim Drago]

Dont shoot the messenger...
I am just telling you the way I have SEEN tech measure the bore. It was NOt with a micrometer, it was with a Cen-tech digital caliper

[Johnny D]

I deleated the compression ratio comments. Don't want to talk apples and oranges and call them peaches. Point one underlined above, I agree 100%. Point two underlined above, with the existing tool or the what I'll call an improved tool I would suggest only the uninitiated would believe he/she could measure repeatly to a few thousands. My entire point of yaking about the existing spark plug bore tool is a take off of someone that suggested improvement to the existing spark plug bore tool as in taking out some of the variability. My goal is to fab an improved tool and see what it's accuracy/repeat capabilities are. An upmanship project. Point three underlined above, not that gullible, I'd use my 3 inch micrometer. If en ya got something with a tolerance of .001 ya damn well better use an appropraite measuring tool and a caliper is not that tool.  

 

Dave is here to save the day. He's got an "upmanship project"

 

May I be the 1st to say "up yours" be the best.

J~

[Mike Collins]

Have you read this??

J~

yes...

[FTodaro]

if you are whistled, there is a procedure to follow. Print it out.. If not followed and signed by competitor and tech official, you could whistle 11:1 and not be dq'ed, or it would be reversed on appeal.

Assuming the procedure is followed and your compression limit is 9.0:1, they typically will give you 9.1 without writing it up. If it is .2 or more off, you will be found non compliant and an RFA will be written.

If the procedure is followed, and you measure over, save your money and don't bother pulling the car apart, you will measure worse. The whistler is EXTREMELY ACCURATE when used correctly. It is not hard to use correctly either. There is also a little fudge built in specific to the miata and the way the tool is used in impound that favors the competitor by .15 or so. So if you whistle 9.6, you will measure about 9.75:1 . If you know you are "right" pull it apart, but if whistled correctly and your over.. you or your machinist made a mistake

On the whistler.. While you could get a pretty good idea on over bore with it.. You could even try and write an RFA, but it would never stick. You can't use the whistler to measure bore.

As far as making a tool. The "tool" is not bad now. The issue is that that you are using a tool that is made to get a general size on bore and measure down to the last .001.. No other tool will be completely accurate less pulling the head.

I'll make it easier.. Take a $12.00 harbor freight Cen-tech digital caliper. Measure something approximately 3 inches long. See if you get the same measurement to .001 each time? NO WAY! Just imagine then adding in the bore tool and the tolerance for error there. A VERY qualified machinist could do this within .004-5, anyone else would struggle to be accurate within .010

Jim

What is the correct procedure. I understand the motor has to be cold.

 

i have never seen this done what does it do, measure the volume of air in the chamber or what??

[Jim Drago]

http://scca.cdn.race...ures Manual.pdf

[Bench Racer]

Dont shoot the messenger...
I am just telling you the way I have SEEN tech measure the bore. It was NOt with a micrometer, it was with a Cen-tech digital caliper

Dude, I was using the 3 inch micrometer to measure your something 3 inches long. Had I known you wanted a bore measured I'd have used a 3 point 4 place bore gauge. Tech you have viewed apparently uses tools to match their capabilities, kind of like the original valve shroud tools.

[Jim Drago]

You ask questions.. I answer.. then you argue? You want me to tell you a different story or what I have actually experienced?

At Runoffs, everything is measured correctly on the bore with "normal" tools.( actually be easy to measure bore with digital calipers accurately with head removed) The two times I have seen the bore checked( non runoffs) personally. It was checked exactly how I described above.. With bore tool through plug, expanded out and measured with a digital caliper.
Your measuring capabilities, the tools you would use etc, while maybe correct, have ZERO relevance to how it is actually being done.
You should see how we measure wing height

[Johnny D]

http://scca.cdn.race...ures Manual.pdf

 

https://www.youtube....h?v=DVoRcPzxp8Q

 

J~

[Bench Racer]

No arguement from me. Other than to say in the real world parts that are manufactured using a specific process are checked using the same process. And that's not to argue, that's fact.

[dstevens]

It's all about context, Dewey.  The context here is hobby racing and as high profile of a club sports car race as a Majors is, it's still hobby racing.  And while the construct may be that every tech is trained to be totally accurate in the inspection process using the best tool for the job, the reality, or shall I say the "fact" is that it's not that way in this case.  It's not just in club sports car racing but karts, local circle track, hobby off road and others.  There just isn't the expertise and equipment many times to facilitate a best of breed solution.  I've got a pretty good set of measuring tools and even with a nice mic unless the operator knows how to use it it's still a crap shoot.  Perhaps you'd agree that the more precise the instrument, the more room for error on the part of the operator.

 

That said, I think that in the case of the Majors it's completely appropriate to implement a best of breed solution. And that would include using a mic and bore gauge specific to the engine.  But that's going to take effort and that effort will likely require funding.  I still get a chuckle from having to pay to be teched in addition to the entry but that's a debate for another time.  I'd do you one further and say that at a Majors an appropriate check would be to remove the head from the get go.  In my racing I can't recall seeing any bore checks with the head attached.

[Jim Drago]

Exactly correct Dstevens! You did a much better job explaining

[Mike Collins]

We don't do a very good job recruiting the right people for the job.  I'm not saying we don't have very good people, we just don't always have the right person with the right set of skills.

 

I would be fairly confident in saying that any time Dan Tiley races and his engine is inspected he knows more about it than the inspector.  

 

I cant even begin to tell you how many times I've had to tell someone using a whistler "they are doing it wrong".....

 

One of our biggest problems is the skill of many of our tech staff does not match the tolerance level we have in the rules....

[Jim Drago]

One of our biggest problems is they skill of many of our tech staff does not match the tolerance level we have in the rules....

Well said, I don't think that is an insult. It is just a fact.

[Jamz14]

I think I'll just pull the head. Easier, and will probably take me less time than verifying operator skill and tool quality.

[Kyle Disque]

For SCCA Tech you get .5+/- off of the smallest measurement UNLESS what is being measures has an ABSOLUTE maximum/minimum....  So being out of round in cylinder bore is .006, you actually could be .011 and still be legal....  Nobody is cheating like that....  No gain...in fact you would have piston slap and poor fitting rings.  If I measured this bore, I would take multiple measurements looking for variance....  I might even measure multiple bores to see if you have a terrible machinist or a really old motor...

 

 

This is yet another case where the "tolerance rule" is not appropriate.

 

It's not meant to provide that much leeway.

 

The spec should be .0060"

 

There are other examples of this.  The GTL splitter is spec'd at 2" - so I can make one that's 2.5"?  This needs to be cleaned up.  I've written in and asked for this to be reviewed, but the GCR authors were not receptive.

 

-Kyle

[Bench Racer]

12. A spoiler may be fitted to the front of the car. It shall not
protrude beyond the overall outline of the car as viewed from
above except as follows:

• GT2: a front splitter may extend up to 3 inches.
• GT3: a front splitter may extend up to 2 inches.
• GTLite: a front splitter may extend up to 2 inches.

Not to argue. My take on this rule is, the spoiler may extend 2 inches beyond the overall outline of the car as viewed from above. May extend up to 2 inches eliminates any other plus dimensional tolerance specification. The spoiler may also be less than 2 inches.

[Mike Collins]

Poorly written rule..it needs the word maximum added to it or it can be interpreted differently...