207 replies to this topic

[Danny Steyn]

While I have not dyno'ed many Spec Miatas, I have either for personal cars or cars through my shop dyno tuned larger V6 and V8 cars( both full race and street rod types) and feel that 1% error would be acceptable/expected and the 1 to 2 HP differences between pulls to be "noise". Maybe Drago or Kessler can say that in their experience,if they did see repeatable 1 to 2hp differences that translated into repeatable results on the track that may help others to get their head around this, but at the regional level,would the majority of SM drivers  feel the difference?  I feel, and a few well known race engine builders(albeit circle track)  feel that a chassis dyno just isn't as "scientific" as an engine dyno. There are just too many variables(noise) that can affect repeatability/accuracy to worry about 1 to 2HP. I may be out of line here, but are we maybe getting crazy over numbers that may or may not mean anything?   

 

1-2HP differences can be observed on consecutive pulls with no changes to anything when dynoing a Spec Miata on a chassis dyno. I have hundreds of files over the years and have seen this pretty much every time. Do a run, record the data, do another run, record the data. Do NOT expect identical results, they will typically vary between 1-2HP.

 

I personally doubt that the 1.5mm allowance will provide anything more than 1-2Hp increase if that much. 

 

With regard to the repeatability of Chassis Dyno's they are nowhere near as accurate as Engine Dynos where there is much tighter control on the ambient conditions. However there are very few engine dyno's currently setup for SM. I only know of one. I doubt that the testing will be done on an Engine Dyno, but I have been wrong before.

 

I believe that NASA/SCCA/Mazda is currently more interested in determining what the 1.5mm STR allowance equates to in terms of performance gain.

[38bfast]

If you build to the rules as published you are good to go. When and if the testing data is ever completed the result s will be reviewed and will be considered. No mater the outcome of the testing the heads as specked today will still be legal and competitive. So at this point everyone can stop sitting on their hands and get out racing again with confidance that if they have built to the current rules they are good to go.

[FTodaro]

Ralph has the SMAC been asked for and have they given parity adjustment recommendations, or is the plan to hold the discussion pending testing?

[38bfast]

Yes Frank the SMAC has received letters requesting parity adjustments. We are working through them now and doing some of our own independent testing and research. At best case it would be a few months before it could be implemented if proved to be a worthy adjustment. We would have liked to have this all done sooner but STR gate forced us to table it. Now that the head rules are solid we can move foward again. Because of the late timing we can not make any rule changes we can only use weights and plates as an adjustment for 2015.

[Jamz14]

1-2 hp is a big deal Danny. The top guys have been telling us so. Yes they say it doesn't matter to the middle pack guys because they cant drive well enough to realize the benefit we are told. But aggregate this with the other things the top guys do to ike out 1 or two hp here and there and it adds up to more than 1-2 hp. And aggregating everything is something you tell us is needed to win. So yes maybe this is only worth one to two,,, but thats not the point............just like you have been saying before this issue came up.

One the one hand we hear mind all the details and on the other we are told it is only one or two hp no big deal.

[38bfast]

Just to note, if you would like to have the rules changed for any one year of car, I.e 1.6 cold air intake. Please get your ducks in a row. Get member suport and documentation and testing to support your request. Do not expect the SMAC to do your research and testing for your request. An example would be just don't write a letter saying the 1.6 should get a header and that's it. Name the brand or brands of header and include data from a relibale source validating your request. Then campaign with your fellow competitors to support your request. Again rember that we will not be able to make rule changes till 2016. But now is a great time to get started.

Contrary to popular belief the SMAC does want parity with all years. We belive that you should be able to win with what every flavor you chose to race. No BS.

[Ron Alan]

Thanks Ralph. Here is my recommendation...

1.6...2275
NA 1.8...back to 47mm plate and 2360

 

Edit...

[Danny Steyn]

1-2 hp is a big deal Danny. The top guys have been telling us so. Yes they say it doesn't matter to the middle pack guys because they cant drive well enough to realize the benefit we are told. But aggregate this with the other things the top guys do to ike out 1 or two hp here and there and it adds up to more than 1-2 hp. And aggregating everything is something you tell us is needed to win. So yes maybe this is only worth one to two,,, but thats not the point............just like you have been saying before this issue came up.

One the one hand we hear mind all the details and on the other we are told it is only one or two hp no big deal.

 

Jamz, I think you misunderstand the point of my post. I agree that 1-2HP is a big deal. However it is going to be a really tough time for anyone running a chassis dyno to establish beyond any reasonable doubt that the 1.5Mm STR allowance yields the 1-2HP that we predict, since there is that much variation in sequential pulls on a chassis dyno, even when NOTHING is changed.

 

I believe the approach will be to do a standard plunge cut head, do enough runs to optimize the performance and establish a base line. Then remove the head, do the 1.5mm STR work, reassemble the engine and redyno, optimizing and establishing the new benchmark. 

 

But after you have done all the pulls, do you select that best run for each, or do you average the best 5 or all 10 or all 20 whatever the case may be. No matter what methodology you select, the standard variability in sequential runs IMHO will make it difficult to categorically state the amount of performance enhancement. 

 

Bye the way, IMHO, a 1-2HP change wouldn't have changed the finishing order of any race that I have been in this past year. However 3-5HP , thats an entirely different matter.

[Bench Racer]

Thanks Ralph. Here is my recommendation...

1.6...2285

Ron, no disrespect relative to your comment on making the 1.6 weight 2285 pounds. Where in the rpm range and in what gear/gears will this minus 15 pounds do any good for the 1.6? 15 pounds reduction is less than 1 percent reduction in overall weight.

[Cnj]

1-2 hp is a big deal Danny. The top guys have been telling us so. Yes they say it doesn't matter to the middle pack guys because they cant drive well enough to realize the benefit we are told. But aggregate this with the other things the top guys do to ike out 1 or two hp here and there and it adds up to more than 1-2 hp. And aggregating everything is something you tell us is needed to win. So yes maybe this is only worth one to two,,, but thats not the point............just like you have been saying before this issue came up.
One the one hand we hear mind all the details and on the other we are told it is only one or two hp no big deal.

The "1-2 hp" gain from the 1.5mm de-burr is an assumption that has taken on a life of its own. Danny has - in part - addressed this.
For various technical reasons I would be extremely skeptical that a 1.5mm de-burr (which in the real world will be de-burred 1mm to be legal as almost no one can get exactly to 1.5mm and not risk being thrown out) will get anything near 2hp and not even 1hp. In fact it could result in a loss. Technical reasons include that the de-burr is tiny - and air flow and pressure pulses don't work in intuitive ways (ie. I don't assume that a de-burr in a closed system automatically improves performance). In addition measurements by dyno or air flow testing are sketchy at best at this resolution. With the vagarities of testing methodologies I would be hesitant to attach credence to any numbers that are posted. This is not F1 where Comsol models are being run and perfect CNC heads are assembled for closed loop testing.

On the other hand the legal added camber is a big deal. This could provide 0.2-0.5 second gains per lap for those who were only able to get 2 degrees of camber and can now get over 3 (legally). Watch for the field to further close up.

CNJ

[Cnj]

Ron, no disrespect relative to your comment on making the 1.6 weight 2285 pounds. Where in the rpm range and in what gear/gears will this minus 15 pounds do any good for the 1.6? 15 pounds reduction is less than 1 percent reduction in overall weight.

Bench - what do you suggest?

CNJ

[Bench Racer]

Bench - what do you suggest?

CNJ

I'll start by saying that someone droped the ball when the 99 plus cars were included into the class. Talking engines only, with the different 99 head design/intake manifold/compression ratio (compare to the 1.6 head design/compression ratio), the 99 plus engine makes gobs of torque below 5,500 rpm that the 1.6 did not make at the inclusion date and the 1.6 does not have comaprable torque today. The 1.6 races well above 5,500 rpm and it sucks big time below 5,500 rpm. Have you ever had a 1.6 beat your 99 in a drag race below 5,500 rpm? If other folks agree that the 1.6 torque shortfall below 5,500 rpm is the main issue, it'll take more than one little item to make the 1.6 raceable with the 99 plus below 5,500 rpm. Compression, ECU/piggy back, headers, ambiant air at intake, eliminate the so called heat soak issue which 1.6er Bruce Wilson seems to say has been solved in the northwest. Producing the required torque below 5,500 rpm may be an impossible task with the 1.6 head/intake manifold/compression ratio. Hopefully this coming week I'll view some dyno graphs of a 10:1 1.6 ITA car and of a 10:1 1.6 F production car. 

 

EDIT:

Yes, some of the potential improvement items listed are not legal today. Do we want the 1.6 to be capable of racing the 99 plus below 5,500 rpm?

[Ron Alan]

Bench - what do you suggest?

CNJ

Craig...have you not been paying attention??

 

 

Ron, no disrespect relative to your comment on making the 1.6 weight 2285 pounds. Where in the rpm range and in what gear/gears will this minus 15 pounds do any good for the 1.6? 15 pounds reduction is less than 1 percent reduction in overall weight.

 

Nothing to back up my suggestion. I'm basing it off were the cars were at the last adjustment 3 years ago. Part of the idea then was to get the cars closer in weight for handling and braking. We know the 99 lost HP but it also lost weight(50lbs). The NA1.8 after first racing at 2400 with a 47mm restrictor was dropped to a 45mm and 2365 then ultimately to 2350 3 years ago(still weak power). At the same time the 1.6 was raised from 2275/2285(SCCA/NASA) to 2300. This change then would seem to suggest the 1.6 would be an overdog at the lower weight. Fast forward 3 years...nothing but complaints and fewer top 1.6 cars. The weight should be taken back off to start with IMO.

 

I agree with the torque argument...but one aspect that rarely comes up in your comments David is the 1.6 is better in the last 400rpms(before rev limiter) than the 1.8. And I in my 1.8 NA would give anything to be able to hit 7200 before shifting! So, it is a little game of give and take...and also an acknowledgement that no matter what is done "equal" cars is impossible. 

 

Was looking for something else recently and stumbled across a video i had forgotten about. This is Brian Ghidinelli in his 99(2013)chasing Ken Sutherland(gray 1.6) and Elliot Skeer(yellow 99). Once Ken gets the lead, Elliot and Brian have no problem maintaing the pace in the draft...but neither have the ability to make a pass under power. You can see coming out of 11 with equal speed the 1.6 and 1.8 accelerate together. At red line shift the 1.6 drops to around 5200rpm(pretty equal speed in 2nd/3rd gear)...I see the torque difference kick in in 4th gear. It is much more noticable going uphill! Basically you dont see much of it here.  I would say these are 3 "Top" prepped cars and drivers! Whats interesting to know about this is Brian 1 month earlier pretty much stomped Ken in the dry at Laguna...not even close!

 

[Tom Sager]

Thanks Ralph. Here is my recommendation...

1.6...2285
NA 1.8...back to 47mm plate and 2375

Be careful what you wish for, Ron.  I too have a '95.  I don't think +2mm and adding 25 pounds makes the care any faster around most tracks.  Mine spent quite a bit of 2013 and nearly all of 2014 in the garage.  47mm/2375 means it'll probably stay in the garage for most of 2015 as well.  47mm/2350 and it'll see some daylight.  The parity discussion often times get confined to power.  That would be fine if the cars all had the same chassis but they don't.  The NB chassis has better geometry and the NB cars are slightly better balanced in terms of weight.  Some may prefer how the NA chassis "feels" or find the lighter car more "fun to drive" but the entries and results in our class overall, the big macro data (results and participation) speaks loud and clear for itself.  

 

I have an '00 also which I haven't driven all that much but it is now prepped pretty well. If I find the time I'll post some video from the October Mid-Ohio race.  There were a couple of very good 1.6 cars there with very good drivers who have many more laps there than I do.  Surprisingly after looking at the video, the 100 pound lighter 1.6 cars did not look quicker through the twisty sections of the track.  A '95 at 50 pounds heavier than the 1.6 would not fare as well.  

 

The parity discussion to me has to include both chassis and power differences.  If the NA cars could all bolt in a '99 engine or have their existing engines make the same power as a '99, then the question to be answered would be: How much less do the NA cars have to weigh to have equal handling to the NB cars over the course of a race?  That's a hard question to answer, but's it's one that should be answered as best we can.  

 

If the NA 1.8 cars get a 47mm plate as you suggest Ron, and if the weight is still 2350, most likely I'll go back to Mid-Ohio (and other tracks) for SCCA Major or NASA events in the '00 car.  I still think it's the slightly better car even with that adjustment, but that should get the 1.8 cars very very close to the NB cars.

 

The 1.6 cars short of the torque improvements people are clamoring for could benefit from a slight weight reduction.  

[Ron Alan]

I'm with you Tom...and I fixed my numbers! In my head I was adding 10lbs plus a bigger restrictor...but somehow I had 2365 stuck in my head(overbore weight!). So 2360 is what i should have said...but I'm good with staying at 2350!! 

[ChrisA]

I'll start by saying that someone droped the ball when the 99 plus cars were included into the class. 

 

Perhaps, the class dropped the ball by retaining the 1.6s... 

[Bench Racer]

Nothing to back up my suggestion. I'm basing it off were the cars were at the last adjustment 3 years ago. Part of the idea then was to get the cars closer in weight for handling and braking. We know the 99 lost HP but it also lost weight(50lbs). The NA1.8 after first racing at 2400 with a 47mm restrictor was dropped to a 45mm and 2365 then ultimately to 2350 3 years ago(still weak power). At the same time the 1.6 was raised from 2275/2285(SCCA/NASA) to 2300. This change then would seem to suggest the 1.6 would be an overdog at the lower weight. Fast forward 3 years...nothing but complaints and fewer top 1.6 cars. The weight should be taken back off to start with IMO.

 

I agree with the torque argument...but one aspect that rarely comes up in your comments David is the 1.6 is better in the last 400rpms(before rev limiter) than the 1.8. And I in my 1.8 NA would give anything to be able to hit 7200 before shifting! So, it is a little game of give and take...and also an acknowledgement that no matter what is done "equal" cars is impossible. 

 

Was looking for something else recently and stumbled across a video i had forgotten about. This is Brian Ghidinelli in his 99(2013)chasing Ken Sutherland(gray 1.6) and Elliot Skeer(yellow 99). Once Ken gets the lead, Elliot and Brian have no problem maintaing the pace in the draft...but neither have the ability to make a pass under power. You can see coming out of 11 with equal speed the 1.6 and 1.8 accelerate together. At red line shift the 1.6 drops to around 5200rpm(pretty equal speed in 2nd/3rd gear)...I see the torque difference kick in in 4th gear. It is much more noticable going uphill! Basically you dont see much of it here.  I would say these are 3 "Top" prepped cars and drivers! Whats interesting to know about this is Brian 1 month earlier pretty much stomped Ken in the dry at Laguna...not even close!

 

Your point 1, is there software used to make these 10 and 15 pound weight adjustments? For talking purposes lets say the 1.6 weight was lowered from 2,300 pounds to 2,200 pounds (there are 2,000 pound 1.6's) because of the 1.6 lack of torque below 5,500 rpm, per the pounds/pound foot ratio the 1.6 would be an overdog above 5,500 rpm. Use the weight and restrictor to bring the 99 plus cars to the 1.6 overdog condition. Trust me, the 1,6 at 2,200 pound below 5,500 rpm could still not play heads up with the 99 plus. The 1.6 intake/head/exhaust  design may not be capable of equal torque/rpm below 5,500 rpm.  

 

Your point 2, no question the 1.6 races much better above 5,500 prm and the hp does not tail off quite as quick over the last few hundred rpm. One can look at the pound/horse power ratio to get that picture.

 

Your point 3, I have posted in the past a top preped/driven 1.6 that can hang with the 99 plus above 5,500 rpm, but can not pass them at Road America, 4 mile. I've also seen a 1.6 stay ahead of 99 cars at Blackhawk Farm, 2 mile. Different tracks will always exist. Under 5,500 rpm the torque numbers show that the 1.6 can not play heads up with the 99 plus.............  Some folks including Joey admit the 1.6 gets jerked at slower rpm's.

 

Tom, per my two cents weight comments are included ^.

 

 

Perhaps, the class dropped the ball by retaining the 1.6s... 

 

Perhaps inclusion fits better than exclusion.  

[Steve Scheifler]

Danny, you need a better dyno, or a better dyno operator, or both.

[Ron Alan]

Not debating you David...but since its been said only weight and plate can now be used for adjustments, I say lets start by taking the weight back off the 1.6 it was last given to start! 

 

  

 

Your point 2, no question the 1.6 races much better above 5,500 prm and the hp does not tail off quite as quick over the last few hundred rpm. 

 

In the end...this is the key..."RACE". The cat is out of the bag and all the cars are in...and they all have their +/-'s. They all race better at one track vs another. And the exact same cars race better or worse depending on who is behind the wheel!

 

I understand the peak torque issue...and I would even go as far as saying its the whole curve! But in the end isnt it still acceleration...distance traveled and time? From redline shift point back to redline? Its the entire curve we use to compare...not 300rpms?

 

I guess another way to change the game is to give the 99/01 back weight? 2425? This would help those who finally made weight at 2300 in the 1.6....

 

Again...just suggesting changes that CAN be made at this time!

[Steve Scheifler]

David, you and others seem to leave something out of your calculations/assumptions when changing weights. In terms of simple acceleration, at lower speeds weight is a fairly good proxy for torque because of course torque is about the work required to move mass, but the higher the speed, the less benefit it has due to drag. If 50 lbs off the 1.6 is just enough 5200 in 2nd, it will be less help in 3rd and still less in 4th because the percent of power being used to fight drag increases exponentially. It will mean almost nothing at the end of those long straights in 4th & 5th because by then almost all the power is used to break the wind, so it would not make the 1.6 an overdog in that scenario. Drafting reduces that significantly and brings weight back into the picture a bit, but still less than with lower gears.

But, at the same time you have huge changes in torque at the wheels with every up-shift while weight is constant. It's a complex environment, which is why there are sophisticated simulation programs to calculate the impact of such changes.

So even for simple acceleration you can never really offset a difference in engine torque with weight because the effects of gearing and aerodynamics treat them differently, and the best you can hope for is closer lap times.

It is often said that the 1.6 is competative or even better at the top of 4th gear, and I think it is said that the 99+ has an aero advantage. Is the 1.6 advantage in those cases strictly the higher redline, which forces the others to shift sooner and thereby lower their torque multiplier? Or does the 1.6 seem to have an edge, side-by-side, even before the 1.8 shifts to 5th?