41 replies to this topic

[Mike Babcock]

Question:

 

Compression ratio limit.  Does this apply to each cylinder, or the complete engine?

[Steve Scheifler]

If you mean do they calculate the average of all four, no, each must be within spec. But if the one they checked was a bit over it might be an interesting angle to try and squirm out of it. 🙂

[Mike Babcock]

Thanks Steve...

 

That's exactly what happened.  1.6 at a regional NASA event was put on the dyno, blew 123hp (117 limit).  Torn down and measured #2, which calculated out to 9.48:1.  That's where the inspection ended with a resultant DQ.

 

I then measured out the other 3 cylinders... here's the whole picture:

#1 - 9.17

#2 - 9.48

#3 - 9.25

#4 - 9.32

 

To be clear, I'm not attempting to overturn the DQ.  That ship has already sailed.  My concern is around the validity of a single cylinder test to determine compliance... especially in the context of a 1.6, which appears not to have as tight of tolerances as the later 1.8's.  According to the SCCA CR calculator, the 1.8 has a +/-1cc swing on the piston dome volume.  I'm seeing a 2.5cc swing on both my 1.6 blocks across the cylinders.  Putting that in perspective, that's roughly the difference between 9.0:1 and 9.5:1.

 

I suppose I could do a thicker HG... but that would come at the expense of the other 3 hamsters.  Doesn't really seem like a fair deal.

 

Is there sufficient data on the 1.6 out there among the engine builders/compliance inspectors that supports or disputes what I'm seeing... or have there just not been enough 1.6 engines torn down of late to make an educated call?

[Caveman-kwebb99]

Wow, Nasa is tearing down motors, you must have made someone very angry!  Also is SM in nasa now a dyno class??? how is 123 a no go?  seems like a very achievable number for a 1.6 to me...

[Mike Babcock]

Well, this was a first for our region.  Our SM class is beginning to grow, so I think there's an increasing interest in keeping everyone honest.  I'm good with that.  What I'm not okay with is a shortcut to the CR calculation process, potentially established during the reign of the NB.

 

Appendix G has the details of the dyno check.  It's just an indicator to justify a tear-down in the absence of an official protest.  But yes, the 117 number is stupidly low.

[Caveman-kwebb99]

Well, this was a first for our region.  Our SM class is beginning to grow, so I think there's an increasing interest in keeping everyone honest.  I'm good with that.  What I'm not okay with is a shortcut to the CR calculation process, potentially established during the reign of the NB.

 

Appendix G has the details of the dyno check.  It's just an indicator to justify a tear-down in the absence of an official protest.  But yes, the 117 number is stupidly low.

 

Seems with that number as the tear down number it would discourage someone with a very good car that is legal to run with that region!  What a pita it would be to prove your legal just cause you have 123hp...  

 

This IMO is where the dyno policy is flawed although it was lucky enough to catch your non compliance which I am also sure is not intentional.

Non compliance is non compliance so no argument there, but man if your gonna tear down cars just because they make good power I think that will limit who wants to race in that region. maybe thats what they are aiming for but would seem to me they would want all the entries they can get.

[Bench Racer]

For NASA, there's a maximum horsepower rule (1.6 = 117hp), bore maximum rule and a maximum overbore rule with added weight. 6hp/117hp = 5% extra power.

 

Were you a random pick for dyno or were you obviously a bit faster to other 1.6 cars? What do your bores measure???

 

If everyone plays by the same NASA rules, the class functions very well. 

[Ron Alan]

I like the use of the dyno as a reference tool...but the max HP numbers NASA lists in their rule set are simply a guideline. Over the HP number allows NASA  to inspect further if they desire...you cannot be DQ'd for it. 

 

From last year to this year the "MAX" dyno numbers changed. The one significant change was in the 1.6 power. The number went from 123hp to 117 hp. I for one brought this up right away because in the years I've been seeing dyno #'s without exception a good motor makes 118-124hp on our local dyno. And this is across all the major motor builders/players in the country. As a NASA official I too want to keep everyone honest but I'm scratching my head at this rule change after 1 year of the "Parity" changes that were allowed in 2017 for the 1.6 car?????

 

Mike, can you share some information?

 

Who took the motor apart(not a name but you or someone else)?

Were you able to watch the process?

What method was used to calculate the compression ratio?(SCCA work sheet?)

If they only did #2 cylinder, did you use the exact same method to calculate? Did you get the same numbers in #2?

Who brought the testing equipment?

Did NASA pay the bill for this time or did you?

 

Was the Dyno after the first race of the weekend or the 2nd? If after the 2nd I assume you received a DQ for that race?

 

Sorry for all the questions but I feel its important that this whole process is transparent and that NASA officials across the country are on the same page! 

[Mike Babcock]

Bores measure out about 3.071, with little more than a couple thousands swing either way.

 

There were 3 people who took the motor apart.  I helped, but it was all supervised by NASA officials.  The worksheet used is based on the SCCA 1.8 spreadsheet, but modified by Dan Tilley to account for the non-dome pistons in the 1.6.  That one doesn't appear to be published, so I can't speak to whether or not it's been fully vetted and approved by either NASA or SCCA.  I was picked because I won.

 

Rich Powers brought the equipment and did all the measurements on #2, and I did the other three.  I was able to validate my measurement technique by re-measuring #2... came up with the same numbers within a couple thousands, so I feel pretty confident with that.  I don't think there's any question as to Rich's integrity and/or know-how related to this stuff.  NASA paid for the dyno, but I'm not aware of any other funds exchanging hands.

 

Dyno was after the Sunday race, and that's the one they issued the DQ for.

 

I certainly don't mind the questions... I'd really like to get this ironed out before the next 1.6 racer gets stuck going through this.  And while the single cylinder test may be fully documented in SCCA, I can't find anything that spells that out in the NASA CC&R's.

[Ron Alan]

Pretty funny a SMAC member doing a NASA compliance check But that's great...as an engineer Rich is Mr numbers so his participation was perfect! And no doubt un-biased!

And you make a good point with regard to a single cylinder...this should be clarified!

 

Also if in fact the measuring method is not posted(as official method)it needs to be!!

[Mike Babcock]

Agreed.

I wonder if it’s possible to buy a non-compliant crate 1.6 from Mazda. Given the variance I was seeing across cylinders, it doesn’t seem all that far fetched.

[Caveman-kwebb99]

I would think if one cylinder is over on CR then you would be found non compliant just as several that had one valve or relief cut on their heads...  Tech should not be teching by intent, they should be teching to the rules!  If the rules need to be changed to admit a higher tollerance then that i something the smac and nasa rule makers need to consider.

 

My only complaint with this process is some arbitrary dyno number being enforced nation wide when dyno results vary greatly from dyno to dyno, as well a number that should be so easily achieved by any high level 1.6!

[Bench Racer]

I do not question info/work by Rich.

 

Did anyone compare all the numbers inserted into the different CR formulas/crevice volume worksheet from one cylinder to the other cylinder? 

 

I understand the CR maximum is 9.40. With a CR difference of .31 between cylinder #1 and #2 it would seem some difference in numbers would be visible. Contact Jason Kohler.

 

#1 - 9.17  <

#2 - 9.48 <
#3 - 9.25
#4 - 9.32

 

Where are all the engine builders?

 

Mr. Brown?

[Ron Alan]

 

 

#1 - 9.17  <

#2 - 9.48 <
#3 - 9.25
#4 - 9.32

 

Where are all the engine builders?

My guess would be VIR!

[Mike Babcock]

The most significant variations were observed in the piston dome volume. I don’t have the numbers with me, but I believe they ranged from 1.4cc to 3.1cc. Piston above deck may also be suspect, but IIRC, that variation didn’t move the CR needle much. Stroke looked pretty close across all four.

These observations look to be consistent on both blocks.

[CarbonRacer]

I went to the SCCA web page to download the Compression Ratio Worksheet and I couldn't find it.

 

I know there was an issue with the Worksheet and it was being verified does anyone have information?

 

Can someone post the most current Worksheet link?

 

 

Thanks

[Bench Racer]

https://www.scca.com...orms-procedures

 

Scroll down left hand side until SM CR Worksheet.

[Bench Racer]

My guess would be VIR!

So sorry, don't they have Wi-Fi at VIR.

[Caveman-kwebb99]

So sorry, don't they have Wi-Fi at VIR.

 

Vir is like going to mid ohio lol

[Bench Racer]

Vir is like going to mid ohio lol

They have fish and no Wi-Fi.