Jump to content

Photo

Compression Ratio - Maximum Allowable

- - - - -

  • Please log in to reply
41 replies to this topic

#21
Caveman-kwebb99

Caveman-kwebb99

    Veteran Member

  • SMembers
  • PipPipPipPipPip
  • 2,971 posts
  • Location:World Wide
  • Region:Great lakes
  • Car Year:2000
  • Car Number:99

They have fish and no Wi-Fi.  :noidea:

 

not sure about the fish they do at least have a real civilized restraunt but the place is in the middle of damn nowhere


K. Webb
Powered by East Street Racing (Best engines in Spec Miata)

Driver coach, Spec Miata Prep shop, Spec Miata Setup

2016 Hard Charger award passing 12 cars runoffs 2016 Mid Ohio

2016 P3 RUNOFFS OVER 40 DIVISION LOL!

2015 First consolation prize Northern Conference Majors Title Pageant
2015 Winner Circus Cat Majors Road America

2015 Winner BlackHawk Majors crash fest

My Signature is still not as long as Danny boy's
 

 

 

Donor - Made PayPal donation Majors Winner - Chatterbox - Blah blah blah... Blah blah blah Instigator - Made a topic or post that inspired other Bona fide - A bonafide Spec Miata driver We have a Winnah! - Won their 1st race... Congratulations! Make it Rain - Made Paypal donation of $100+

#22
Jason J Ball

Jason J Ball

    Member

  • Members
  • PipPipPip
  • 161 posts
  • Location:Clayton, NC
  • Region:NASA-SE
  • Car Year:1990
  • Car Number:15

Why did I just spend $$$ to build a new engine with this unreasonably low HP limit on my car? 117hp isn't enough to win against any version of the 1.8. I should know, I've had 117hp for the last 5 years. How was this number calculated? Did I just waste $1000's of dollars?


Bona fide - A bonafide Spec Miata driver

#23
Caveman-kwebb99

Caveman-kwebb99

    Veteran Member

  • SMembers
  • PipPipPipPipPip
  • 2,971 posts
  • Location:World Wide
  • Region:Great lakes
  • Car Year:2000
  • Car Number:99

Why did I just spend $$$ to build a new engine with this unreasonably low HP limit on my car? 117hp isn't enough to win against any version of the 1.8. I should know, I've had 117hp for the last 5 years. How was this number calculated? Did I just waste $1000's of dollars?

 

 

No waste as long as was built legal!  but now you may have to pull it apart for compliance check ;) since its likely over 117 now. 


K. Webb
Powered by East Street Racing (Best engines in Spec Miata)

Driver coach, Spec Miata Prep shop, Spec Miata Setup

2016 Hard Charger award passing 12 cars runoffs 2016 Mid Ohio

2016 P3 RUNOFFS OVER 40 DIVISION LOL!

2015 First consolation prize Northern Conference Majors Title Pageant
2015 Winner Circus Cat Majors Road America

2015 Winner BlackHawk Majors crash fest

My Signature is still not as long as Danny boy's
 

 

 

Donor - Made PayPal donation Majors Winner - Chatterbox - Blah blah blah... Blah blah blah Instigator - Made a topic or post that inspired other Bona fide - A bonafide Spec Miata driver We have a Winnah! - Won their 1st race... Congratulations! Make it Rain - Made Paypal donation of $100+

#24
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 1,837 posts
  • Location:St. Louis

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.


I’m having trouble believing the the piston (dish in the case of a 1.6) varies by that much. I assume you mean either the combustion chamber in the head or the amount that the pistion extends above the deck. Both are common points of variance. Head castings in particular can have the differences you saw from core shift. You can clean it up a little bit with valve seat height but of course you don’t generally want to sink valves deeper than necessary, especially intakes. Blocks are also an issue due to variances in crank to deck height. The deck can be sloped end-to-end and/or side-to-side. For many years Sunbelt used non-US market pistons with a higher pin height so they could deck the block more and align bore crank journals without running out of piston to head clearance. You can do a little of the same. I’ve even spent hours hand matching rods (some stock, some with the big end resized) & pistons to each cylinder for best match to each hole.

BTW, measuring piston height above the deck can be pretty tricky and can also be subject to deck slope.
Bona fide - A bonafide Spec Miata driver

#25
Tom Hampton

Tom Hampton

    Egregious Member

  • SMembers
  • PipPipPipPipPip
  • 1,840 posts
  • Location:Mckinney, tx
  • Region:South west
  • Car Year:1992
  • Car Number:41

117 for a   1.6L
129 for an NA8
128 for a   '99
 
That's dumber than a box of rocks---dumb-squared.  Who's 1.6L DOESN'T make 117?  So, now we want to tear down EVERY 1.6L that competes in a f*cking regional? because, if you don't even make 117 HP, you will be off the back...even in a regional. 

 

And, NASA Champs?  You wouldn't even be competitive at 123.  So, NASA is planning (based on this published standard) to tear down EVERY, SINGLE 1.6L at COTA this summer

 

What standard are we applying to the dyno test---eg, what probability are we trying to establish as the criteria for a tear-down? 

 

1. Possible?

2. More likely than not?

3. Probable?

4. Highly likely?

5. Not possible legally? 

 

At the 117HP standard, I would guess that we are somewhere less than #1. 

 
If someone asks me to tear down my engine at a g*d D*mn regional they can f*ck off.  I've got better things to do with my time---if I wanted that headache I'd compete in majors.  They won't have to worry about "banning" me, either.  The feeling will be mutual---I won't come back.  Plenty of other options for racing.

Other interesting "rules":
 

11. Additional runs may be performed using NASA compliance parts such as ECUs and AFMs.
12. NASA officials may seal the hood of any vehicle that produces more horsepower than the specifications above.

 

ECUs and AFMs are kind of a matched set along with timing, FPR, AFM flapper door orientation, and AFM tuning.  Seriously, so now they want to randomly swap parts and try and subject me to a tear down as a result of the next pull? That's not how we do dyno testing. 
 
Seal the HOOD?  the rules don't seem to indicate when the Dyno will be employed.  So, say after Q1 on Saturday morning?  I pull 118 on the dyno.  My hood is now sealed FOR THE ENTIRE WEEKEND?  So, I "can't" get into the engine compartment AT ALL---perhaps to check fluids, adjust FPR, replace a master cylinder, pump out fuel? 
 

NASA, its officers, officials, and assignees are not responsible for any mechanical failures or damage otherwise while the dyno runs are performed.

 

So, NASA wants to subject my car to a test, which I don't have control or discretion over.  They want the right to make changes that could affect AFR negatively (too lean), with no indication that the official doing this knows what the hell he/she is doing (eg, an SM engine builder).   And they want to be indemnified against the ultimate HARM caused as a result of a flawed methodology conducted by an individual without the requisite knowledge to do the test safely?  An SM engine costs $6500 from a pro shop. 

 

If you blow my engine because of your stupidity...you bet your ass you better be ready to pony up the cash. 

 

Our ethos is "you break it, you buy it".  If you aren't willing to take the risk, then neither am I. 


  • Jason J Ball likes this

-tch
Build: www.tomhampton.info

video: vimeo.com/tomhampton

Support: X-Factor Racing

 

I didn't lose, I just got outspent!

Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#26
Tom Hampton

Tom Hampton

    Egregious Member

  • SMembers
  • PipPipPipPipPip
  • 1,840 posts
  • Location:Mckinney, tx
  • Region:South west
  • Car Year:1992
  • Car Number:41

The more I think about it....the more I think that I'd be even more suspicious of the cars that DON'T make 117---that's more of an indication that they may have a special dyno-mode, than  118HP is of possible illegal compression ratios. 


-tch
Build: www.tomhampton.info

video: vimeo.com/tomhampton

Support: X-Factor Racing

 

I didn't lose, I just got outspent!

Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#27
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 1,837 posts
  • Location:St. Louis

What Tom said, with additional emphasis on swapping AFMs being the dumbest of dumb ideas. Not on my car they wouldn’t, period.
Bona fide - A bonafide Spec Miata driver

#28
Jason J Ball

Jason J Ball

    Member

  • Members
  • PipPipPip
  • 161 posts
  • Location:Clayton, NC
  • Region:NASA-SE
  • Car Year:1990
  • Car Number:15

No waste as long as was built legal!  but now you may have to pull it apart for compliance check ;) since its likely over 117 now. 

 

It certainly better be more than 117hp!


Bona fide - A bonafide Spec Miata driver

#29
Caveman-kwebb99

Caveman-kwebb99

    Veteran Member

  • SMembers
  • PipPipPipPipPip
  • 2,971 posts
  • Location:World Wide
  • Region:Great lakes
  • Car Year:2000
  • Car Number:99

It certainly better be more than 117hp!

 

But your not allowed to be over in nasa LOLOLOLOL... maybe scca will tollerate cheated up 1.6's over 117! :)


K. Webb
Powered by East Street Racing (Best engines in Spec Miata)

Driver coach, Spec Miata Prep shop, Spec Miata Setup

2016 Hard Charger award passing 12 cars runoffs 2016 Mid Ohio

2016 P3 RUNOFFS OVER 40 DIVISION LOL!

2015 First consolation prize Northern Conference Majors Title Pageant
2015 Winner Circus Cat Majors Road America

2015 Winner BlackHawk Majors crash fest

My Signature is still not as long as Danny boy's
 

 

 

Donor - Made PayPal donation Majors Winner - Chatterbox - Blah blah blah... Blah blah blah Instigator - Made a topic or post that inspired other Bona fide - A bonafide Spec Miata driver We have a Winnah! - Won their 1st race... Congratulations! Make it Rain - Made Paypal donation of $100+

#30
Bench Racer

Bench Racer

    Different strokes for different folks : )

  • Members
  • PipPipPipPipPip
  • 5,042 posts
  • Location:Wauwatosa, WI
  • Region:Milwaukee
  • Car Year:1990
  • Car Number:14

117 for a   1.6L 
129 for an NA8
128 for a   '99

The 1.6 dyno or other support data or lack there of would be very interesting to view. Take a 1.6 and a 99 at those numbers straight off the Dyno with equal setup/drivers, have a race and view  the :blush: faced officials.


Broken record - You are starting to sound like a broken record. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#31
Bench Racer

Bench Racer

    Different strokes for different folks : )

  • Members
  • PipPipPipPipPip
  • 5,042 posts
  • Location:Wauwatosa, WI
  • Region:Milwaukee
  • Car Year:1990
  • Car Number:14

But your not allowed to be over in nasa LOLOLOLOL... maybe scca will tollerate cheated up 1.6's over 117! :)

Mine isn't cheated and it's got 10 hp more with 109 lb. ft. on a DynoPack. Glad it's got SCCA decals.


Broken record - You are starting to sound like a broken record. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#32
Tom Hampton

Tom Hampton

    Egregious Member

  • SMembers
  • PipPipPipPipPip
  • 1,840 posts
  • Location:Mckinney, tx
  • Region:South west
  • Car Year:1992
  • Car Number:41

Mine isn't cheated and it's got 10 hp more with 109 lb. ft. on a DynoPack. Glad it's got SCCA decals.


Yeah, but your's breaths fire.

http://mazdaracers.c...ge-3#entry78114

-tch
Build: www.tomhampton.info

video: vimeo.com/tomhampton

Support: X-Factor Racing

 

I didn't lose, I just got outspent!

Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#33
Mike Babcock

Mike Babcock

    Member

  • Members
  • PipPipPip
  • 30 posts
  • Location:Mesa, AZ
  • Region:AZ
  • Car Year:1990
  • Car Number:166

I’m having trouble believing the the piston (dish in the case of a 1.6) varies by that much. I assume you mean either the combustion chamber in the head or the amount that the pistion extends above the deck. Both are common points of variance. Head castings in particular can have the differences you saw from core shift. You can clean it up a little bit with valve seat height but of course you don’t generally want to sink valves deeper than necessary, especially intakes. Blocks are also an issue due to variances in crank to deck height. The deck can be sloped end-to-end and/or side-to-side. For many years Sunbelt used non-US market pistons with a higher pin height so they could deck the block more and align bore crank journals without running out of piston to head clearance. You can do a little of the same. I’ve even spent hours hand matching rods (some stock, some with the big end resized) & pistons to each cylinder for best match to each hole.

BTW, measuring piston height above the deck can be pretty tricky and can also be subject to deck slope.

 

Nope... piston volume.  Used a burette to measure the volume in cc's.  I too was surprised at the variations there, and would've expected to see much more variance in the combustion chamber (head).  But I never saw more than 0.6cc swing across all four chambers, in either of the two heads I have.



#34
Caveman-kwebb99

Caveman-kwebb99

    Veteran Member

  • SMembers
  • PipPipPipPipPip
  • 2,971 posts
  • Location:World Wide
  • Region:Great lakes
  • Car Year:2000
  • Car Number:99

Mine isn't cheated and it's got 10 hp more with 109 lb. ft. on a DynoPack. Glad it's got SCCA decals.

 

Well that is gonna require a teardown to be proven now if you ever slap those nasa decals on it look out... This whole idea of a dyno number that low causing a tear down is a complete joke imo!  Now maybe it will only be the winners ever sent to the dyno so if thats the case welcome to the nasa super tour! 


K. Webb
Powered by East Street Racing (Best engines in Spec Miata)

Driver coach, Spec Miata Prep shop, Spec Miata Setup

2016 Hard Charger award passing 12 cars runoffs 2016 Mid Ohio

2016 P3 RUNOFFS OVER 40 DIVISION LOL!

2015 First consolation prize Northern Conference Majors Title Pageant
2015 Winner Circus Cat Majors Road America

2015 Winner BlackHawk Majors crash fest

My Signature is still not as long as Danny boy's
 

 

 

Donor - Made PayPal donation Majors Winner - Chatterbox - Blah blah blah... Blah blah blah Instigator - Made a topic or post that inspired other Bona fide - A bonafide Spec Miata driver We have a Winnah! - Won their 1st race... Congratulations! Make it Rain - Made Paypal donation of $100+

#35
Bench Racer

Bench Racer

    Different strokes for different folks : )

  • Members
  • PipPipPipPipPip
  • 5,042 posts
  • Location:Wauwatosa, WI
  • Region:Milwaukee
  • Car Year:1990
  • Car Number:14

Well that is gonna require a teardown to be proven now if you ever slap those nasa decals on it look out... This whole idea of a dyno number that low causing a tear down is a complete joke imo!  Now maybe it will only be the winners ever sent to the dyno so if thats the case welcome to the nasa super tour

Dude, you made my day. :rotfl:


Broken record - You are starting to sound like a broken record. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#36
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 1,837 posts
  • Location:St. Louis

Nope... piston volume. Used a burette to measure the volume in cc's. I too was surprised at the variations there, and would've expected to see much more variance in the combustion chamber (head). But I never saw more than 0.6cc swing across all four chambers, in either of the two heads I have.


OK, but something wrong there. I’d guess you have one or more odball pistons, or you aren’t getting an accurate measurement. I’d put it something over 100:1 against finding that kind of variance in stock pistons of the same part number unless they changed spec along the way. I’m actually thinking more like 1000:1 but might not wager at that level.
Bona fide - A bonafide Spec Miata driver

#37
Mike Babcock

Mike Babcock

    Member

  • Members
  • PipPipPip
  • 30 posts
  • Location:Mesa, AZ
  • Region:AZ
  • Car Year:1990
  • Car Number:166

OK, but something wrong there. I’d guess you have one or more odball pistons, or you aren’t getting an accurate measurement. I’d put it something over 100:1 against finding that kind of variance in stock pistons of the same part number unless they changed spec along the way. I’m actually thinking more like 1000:1 but might not wager at that level.

 

I agree... it's weird.  I'm not having any luck posting an actual photo, but below is a link (maybe it'll actually work) that should take you to a shot of pistons 2 and 3 for the block that's currently in the car.  Note the difference:

 

http://i1243.photobu...zpszc3mhuzi.jpg

 

Piston 4 is the same as 3... but piston 1 is different than either 2 or 3.  I don't have a shot of #1, but there's no "button" in the center, and no STD stamp.  Doesn't appear to have been machined, and all 4 pistons in my spare block look exactly like this.

 

Now... having said all that, the 2.5cc variance I'm seeing is on the spare block.  Only a 2.1 swing on the block with the "variety pak".  Still a bit much, but I would expect the opposite.

 

I don't have any history on the spare motor... that was in the car when I got it.  The "variety pak" motor was rebuilt several years ago... I bought it that way from a fellow racer.  So maybe the builder just pieced it together with whatever was lying around.  



#38
FTodaro

FTodaro

    Veteran Member

  • SMembers
  • PipPipPipPipPip
  • 2,902 posts
  • Location:Columbus Ohio
  • Region:Great Lakes
  • Car Year:2001
  • Car Number:35

The more I think about it....the more I think that I'd be even more suspicious of the cars that DON'T make 117---that's more of an indication that they may have a special dyno-mode, than  118HP is of possible illegal compression ratios. 

What is the NASA limit, VVT?


Frank
TnT Racing
SCCA Ohio Valley Region
Chairman, SCCA Great Lakes Divisional Series Committee.

Make it Rain - Made Paypal donation of $100+ We have a Winnah! - Won their 1st race... Congratulations! Bona fide - A bonafide Spec Miata driver Donor - Made PayPal donation

#39
Tom Hampton

Tom Hampton

    Egregious Member

  • SMembers
  • PipPipPipPipPip
  • 1,840 posts
  • Location:Mckinney, tx
  • Region:South west
  • Car Year:1992
  • Car Number:41

What is the NASA limit, VVT?


Don know why I didnt copy that too. From memory it was 126.

-tch
Build: www.tomhampton.info

video: vimeo.com/tomhampton

Support: X-Factor Racing

 

I didn't lose, I just got outspent!

Beta-Tester - Assisted us with beta testing the website. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#40
Steve Scheifler

Steve Scheifler

    member

  • Members
  • PipPipPipPipPip
  • 1,837 posts
  • Location:St. Louis

I agree... it's weird. I'm not having any luck posting an actual photo, but below is a link (maybe it'll actually work) that should take you to a shot of pistons 2 and 3 for the block that's currently in the car. Note the difference:

http://i1243.photobu...zpszc3mhuzi.jpg

Piston 4 is the same as 3... but piston 1 is different than either 2 or 3. I don't have a shot of #1, but there's no "button" in the center, and no STD stamp. Doesn't appear to have been machined, and all 4 pistons in my spare block look exactly like this.

Now... having said all that, the 2.5cc variance I'm seeing is on the spare block. Only a 2.1 swing on the block with the "variety pak". Still a bit much, but I would expect the opposite.

I don't have any history on the spare motor... that was in the car when I got it. The "variety pak" motor was rebuilt several years ago... I bought it that way from a fellow racer. So maybe the builder just pieced it together with whatever was lying around.


You hava a mishmash of stuff there. The one marked STD probably isn't even a Mazda part. The late “factory” crate engines that came out of Canada were assembled by someone else and used some conspicuously different parts, but I’ve never seen that stamp in an original or crate engine. One possible explanation is that it is common for aftermarket pistons to have a larger dish, or higher pin height, intended to drop compression by .5 or more. The rationale is that old engines being rebuilt often also have the head and/or block decked which raises compression, are otherwise tired and often get fed cheap fuel. Lowering compression a bit reduced the risk of harmful knock. That’s what I suspect you have run into.
Bona fide - A bonafide Spec Miata driver




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users