373 replies to this topic

[James York]

Ken hit on something that I think is really important to consider. The size/weight of the Hoosier really affects the 1.6. Would allowing the 1.6 a lighter wheel(unsprung weight/rotating mass) be of any benefit?

Absolutely it will help some.  How much, no idea.  Probably not enough.

[Johnny D]

I was thinking the same thing last night, lighter wheel, but...

 

Is the larger dia a weight issue or a gearing ratio issue or both.

 

And then does that 4.78 rearend work that was mentioned.

J~

[Sean - MiataCage]

A problem I see here standing on the sideline is the 1.6 Owners are still "brainstorming" theoretical and anecdotal solutions and not getting behind ONE solution.  You guys have to agree with each other before you can expect anyone else to take it seriously?  Do some math, do some testing, but random "ideas" are holding you back from your goal?

 

RX-7 AFMs and new intakes, plus dyno tuning?  Anyone actually tried that?  Fact:  An "untuned" RX-7 AFM flows less than a "tuned" Miata AFM.  I'm serious. 

 

Check with your engine builder on the 9.9 CR - my base of knowledge on this is almost getting tossed from the 2007 NASA Champs because my 9.4 CR 1.6 motor had to have the pistons flycut to keep from hitting the head, and thus they were "shorter" than stock.  That was supposedly because my "crate" head had large-ish combustion chambers.  The head was NOT cut, which was why the CCs were large - we had "peach" heads and we wanted to use them as long as possible, which meant cutting the minimum from them to avoid falling outside FSM spec, versus cutting the blocks, which (I believe?) had no FSM spec.  With two different engine builders, I know we had to pair heads and blocks carefully just to get to 9.4 without flunking the piston specs.  If I'm FOS on this, someone with facts please chime in!  Engine builders, this is your chance to help! 

 

I'm not trying to sound like or be a jerk here ... I'd LOVE to see a 1.6 win a Runoffs again!

There are several things being worked through with comprehensive testing plans that will be tested on both East and West coast cars with involvement from people/companies that can make the necessary changes within SCCA to bring the 1.6L car back to being competitive.  We just can't publicly discuss it all right now, but rest assured things are being looked at and tested. 

 

It's not worth bringing up in public yet as it just gives too many people a reason to try to say why it won't work.    More soon......

[ECOBRAP]

I think a rear end would be a good move. Someone in this thread posted effective torque figures with the 6 speed transmission, can anyone do that with diff ratios instead? That is all math and could be easy data to justify a change. Even if I have to get a custom geared diff for ~$1500, hell of a lot cheaper than upgrading to a 1.8. Also, don't tell me the mazdacomp is an advantage when it has the structural integrity of a toothpick. Any advantage it provides will be equalized with the inevitable supernova explosion and DNF

 

I threw out the idea of lighter wheels earlier in the thread, and of course it will improve acceleration, but I don't think it will be enough to justify the extra $. You could probably get the same effect by dropping 20lbs out of the car in general. Correct me if I'm wrong.

 

I thought new rules were supposed to come out yesterday? I have a lot on the line for next year and need to start making moves. If I can be reassured the 1.6 will get SOME help next year, that's enough for me to keep mine and try it out. A deadline or timeline would be useful!

[Ron Alan]

I think a rear end would be a good move. Someone in this thread posted effective torque figures with the 6 speed transmission, can anyone do that with diff ratios instead? That is all math and could be easy data to justify a change. Even if I have to get a custom geared diff for ~$1500, hell of a lot cheaper than upgrading to a 1.8. Also, don't tell me the mazdacomp is an advantage when it has the structural integrity of a toothpick. Any advantage it provides will be equalized with the inevitable supernova explosion and DNF
 

I mentioned in another thread...but worth repeating. The Mazdacomp/clutch pack is not usually the issue...it is the stock rear end and it's parts that break first. Smooth shifters/down shifters and those who don't spend a lot of time going backwards on or off track have great luck with these LSD's
Not aware of any different ratios for the 1.6 diff. There are several that fit in the 1.8

[James York]

 

I thought new rules were supposed to come out yesterday? I have a lot on the line for next year and need to start making moves. If I can be reassured the 1.6 will get SOME help next year, that's enough for me to keep mine and try it out. A deadline or timeline would be useful!

I believe Jim posted in a thread elsewhere, that the SCCA at this time was only discussing the rules put forth in the preliminary Fastrack.  Meaning just the cylinder head and bushing rule changes.

 

So, for the SCCA, I believe at least to start 2015, rules around car parity are as is in 2014.

[SaulSpeedwell]

SaulSpeedwell, if your pistons were at risk of hitting the head it was because the top of the block was cut too much.

It may be that the pistons were cut shorter (which is in no way legal) because the combustion chambers on the head were too *small* and the compression would have been too high. You would have been better off using a thicker head gasket.

I think that's the point - to GET TO 9.4 CR, the Pistons were hitting. If you skim the head, you run afoul of the FSM head height around 2 or 3 'cuts', and that's at 9.4. Not a problem for Joe Regional, but if you were looking at teardown you had to stay above the head minimum height. It wasn't as much of a problem with 90-93 heads, but crate heads were CC-ing higher so you HAD to deck the block. We had cut the 90-93 heads too many times and so they got passed onto the midpack/Regional 'used parts market'.

I'm going off old somewhat-secondhand info from two engine builders here, but AT THE TIME, we were trying to make the best 'teardown-legal' 1.6s we could!

I know we disagree on the CAI, but it's hard for me to ignore the math and data behind air temperature.

[B(Kuch)Kucera45]

There are several things being worked through with comprehensive testing plans that will be tested on both East and West coast cars with involvement from people/companies that can make the necessary changes within SCCA to bring the 1.6L car back to being competitive.  We just can't publicly discuss it all right now, but rest assured things are being looked at and tested. 
 
It's not worth bringing up in public yet as it just gives too many people a reason to try to say why it won't work.    More soon......

Sean,we know they are working ( testing ) the heads but are you saying that they are testing other things to get better parity ?

[wheel]

The tests are to determine the difference, if any, between a stock head, a plunge cut head and a p.c. head with the 1.5 de-burr.  I expect that other data will also come out of the tests, but that is not the purpose of the tests.  

[Bench Racer]

 

RX-7 AFMs and new intakes, plus dyno tuning?  Anyone actually tried that?  Fact:  An "untuned" RX-7 AFM flows less than a "tuned" Miata AFM.  I'm serious. 

I read what I read and when I read and when there is 1.930 more square inch opening, I'm thinking it's doing something someplace. In this case the guys numbers say the Miata OEM AFM potentially allows 13 CFM less air flow and he says, it's doing more above 6,000 rpm. Untill tested on Dyno, I'll buy in. To bad no improvement below 5,500 rpm.

 

Miata Air Flow Meter Replacement

by Randy Stocker ( solomiata@aol.com )

 

 1) I read that for your 1.8 motor upgrade you modified your 1.6 fuel injection with a larger air flow meter from an '86-88 RX7 because the OEM 1.6 flow meter was too restrictive. I have modified my 1.6 with a muffler and K&N cone air filter. Will the RX7 flow meter help me make more power?

 

If you never turn the motor past 6000 rpm then you'd be wasting your time. The factory flow meter CFM threshold before limiting HP is about 6000 rpm with the 1.6 motor (the stock engine will flow 178 CFM at 7200 rpm while the meter is rated only at 165CFM). If your 1.6 motor is relatively unmodified (maybe a performance muffler and intake plumbing) but you regularly go past 6000 rpm then putting the RX-7 unit in will produce about a 5 HP gain, you'll probably only notice it after 6000 rpm though.

 

 

UPDATE 7/1/98 There has been some confusiuon on what an 86-88 RX7 flowmeter looks like. Seems that many junk yards simply put all the flowmeters in a large box for you to sort through. The RX7 flowmeters external dimentions are the same as the miata except for height. When laying flat with the plastic cover facing up, the length and width are the same. The RX7's internal dimentions are larger. The Miata measures 1 3/4" square, the RX7 meter measures 2" wide by 2.5" tall. Hope this helps.

[Ken SM94]

SaulSpeedwell, that's interesting.  All the crate heads I have dealt with had combustion chambers on the small side. In fact I know of some crate engines that were slightly over 9.4 right out of the box.  Stock engines are typically closer to 9.1-9.2.

 

I and some of my local friends have some good flowing 1.6 heads that couldn't be used after the change in minimum head thickness a few years ago because they are slightly too thin.  Allowing us to cut the head for 9.9:1 would bring these heads back into play. 

[ECOBRAP]

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[SaulSpeedwell]

SaulSpeedwell, that's interesting.  All the crate heads I have dealt with had combustion chambers on the small side. In fact I know of some crate engines that were slightly over 9.4 right out of the box.  Stock engines are typically closer to 9.1-9.2.

 

I and some of my local friends have some good flowing 1.6 heads that couldn't be used after the change in minimum head thickness a few years ago because they are slightly too thin.  Allowing us to cut the head for 9.9:1 would bring these heads back into play. 

 

Entirely possible, I certainly don't have a comprehensive database of heads, I just know what I was doing with two engine builders and about 6 motors to try to make the 1.6 fly and pass teardown.  Although, our "crate" heads were NOT brand new ... they were mid/late 1990s "crates", often used to remedy shortnose crank failures in the 1990s cars.  It seemed like those were always "peach" motors .... versus a true 2002-2007 date-of-manufacture "crate" 1.6, which always seemed to suck, and for good cause according to the engine builders.

 

I'm still stuck on the math of what 0.6 CR gives you, though.  It ain't much.  If you got better than the theoretical max, it seems like something else was actually in play while that head off was off for decking.  Better leakdown, better valvejob, etc.?

[steveracer]

I think the 1.6's need a small, low pressure turbo, only way to effectively raise torque. Add option of late mode suspension.

 

Let the 1.8's run unrestricted, weights adjusted for parity.

 

What's an unrestricted '99 make hp/torque wise?

[Bruce Wilson]

 

I'm still stuck on the math of what 0.6 CR gives you, though.  It ain't much.

I read somewhere on the Internets that a 1 point increase yields a 5% torque gain.  So would 3 more ft-lbs be enough?  I think it might be close.  As many have already said, true parity will never exist in SM.  The real measure can only be done in races, e.g. can a pass can be executed with a good draft, etc.

[Tom Hampton]

That corresponds to the references I found, but they were substantiated with test data in the 1500 rpm range. So, I'm not sure how things might change in the 5000 to 7500 rpm range.

The formula I found said:

Torque_gain = (new_cr / old_cr) ^ 0.4

For the ratios in question that's right at 2.5 percent (or 3 hp). IF the physics holds across the rpm range differences.

[SaulSpeedwell]

Absolutely it will help some.  How much, no idea.  Probably not enough.

 

This can be calculated.  Grab some bored engineer with a 1.6 and make him do the math.  I did the math on the flywheel, and it is, in MY opinion, negligible. There are 4 wheels, but they are spinning 4.3 times slower than the flywheel when you are in 4th gear, so pound for pound it is going to be ... well .... 4.3 times as negligible?  And what's it going to cost?  To be meaningfully lighter, we'd be talking $250+ per wheel?  Times 8 to 16 wheels for most guys?  Is this really what the 1.6 Union wants?      I wouldn't want it, but I also don't and should not have a vote!

[SaulSpeedwell]

I read somewhere on the Internets that a 1 point increase yields a 5% torque gain.  So would 3 more ft-lbs be enough?  I think it might be close.  As many have already said, true parity will never exist in SM.  The real measure can only be done in races, e.g. can a pass can be executed with a good draft, etc.

 

Unfortunately, CR vs. efficiency isn't linear.  See FIgure 24 below.  I've got MIT/Taylor's text in front of me, and I'm getting 1.7% THEORETICAL gain going from 9.4 to 9.9 CR.

 

http://naca.central....-report-205.pdf

 

With every automaker willing to kill their Mom and bolt on turbos and 9-speed transmissions to try to meet the new 54.5 MPG bogey, I can assure you if there was a 5% efficiency gain in CR just laying there for the taking, there would be no 87 octaine.  We'd all be running 93+ and getting 5% better MPG?

 

In contrast, see Fig 3 in the below.  It's a little complicated, but it is a FIAT tech paper that basically shows  that 50 degrees F of intake air temperature is worth ~3.5%.  It also indicates that the SAE dyno correction factor we know/love is a bit harsher than reality, compared to actual vehicle testing.  (I'm a skeptic, though, so I'm assuming FIAT's engines just make crappy numbers on SAE dynos and this whole thing was a trumped up study commissioned by the Pope).

 

http://www.scielo.br.../v25n3/a10v25n3

 

FIAT's bias aside, the point here is that the SAE Correction factor itself is a somewhat valid indicator how much intake air temperature matters.  Plus, "we" already have data showing that the 1.6 is sucking 50+ degrees hotter air than the NBs.  Don't take my word for it,

 

The voting should go like this:

Joe 1.6 Frontrunner (does this guy stiull exist, lol?):  Vote for ITA engine rules, make a custom intake to lower IAT under today's rules

Joe Engine Builder:  Vote to scrap existing heads and make ITA engine rules legal

Joe Cheapskate/Lazyass:  Vote for weight and RP changes, and a cold air intake provision

 

I have no plans whatsoever to profit from any of the above. 

[SaulSpeedwell]

Just for fun:

 

http://www.bgsoflex.com/crchange.html

 

http://www.wallacera...m/hp-cr-chg.php

 

I never understood why "we" went to such lengths to maximize CR, or why the peanut gallery screamed about it so much.  Of all the gains I could have left on the table, I was least worried about what 0.1 CR would do for me ....

[Steve Scheifler]

Not surprisingly, the two arrive and very different answers (% gain). Unfortunately both deal with peak HP only and no sense of whether the % increase should be pretty much consistent across the powerband (assuming the engine is not significantly intake or exhaust limited). Seems likely, and I suspect that my strong sense that compression has more impact on peak torque than peak HP probably stems mostly from street cars that were limited at both ends.