ITA RX7 Tubing size

[Jake]

Just taking a poll. If you read the GCR to the letter of the law, you are allowed to run 1.5x.095 tubing on an ITA RX7, but the RX7 just squeeks by. If it were classed with a weight even 10lbs higher it would require 1.75x.095 or 1.5"x.125 tubing. So if a car like the RX7 were to be classed in ITB at a higher weight it would change the tubing requirement - and the ITAC is hesitant to create this situation.

My question: What size tubing are you running on your RX7? (would it meet the heavier requirement anyway)

Thanks!!

[Marcus Miller]

Originally posted by Jake@Aug 28 2005, 08:15 AM
Just taking a poll. If you read the GCR to the letter of the law, you are allowed to run 1.5x.095 tubing on an ITA RX7, but the RX7 just squeeks by. If it were classed with a weight even 10lbs higher it would require 1.75x.095 or 1.5"x.125 tubing. So if a car like the RX7 were to be classed in ITB at a higher weight it would change the tubing requirement - and the ITAC is hesitant to create this situation.

My question: What size tubing are you running on your RX7? (would it meet the heavier requirement anyway)

Thanks!!

[snapback]59137[/snapback]

My pro7 car is built with 1.5 X.120
My ITA car is being built right now, at 1.5 X .095. Perhaps not the smartest choice, given the situation you outlined above, but I'm building a "to the bleeding edge" car.

Marcus

[lateapex911]

I bet that at least half the ITA/IT7 or otherwise elible RX-7s are built with .095. Mine is...I knew it wasn't an overdog and wanted to keep it as light as possible.

It is a mjor reason the car can not go to ITB as is.

The only option to move the car to ITB would be to slow the car down via HP restrictions.

[Speed Raycer]

Mine is 1.5"x.095 and I've built two other cars that are as well.

[Chris Taylor]

They make exceptions all the time... wasn't the original 1.8 SM way over the limit? Who's to say they can't make an exception on this?

Not having any clue as to how close competitive ITA-RX7's and ITB cars are (since there are none of the above in my division), how far off are the two cars? Would the RX7 really need to be turned into a tank to run in ITB? Why not just remove the carb allowance? Does anybody run anything but the stock carb?

Congratulations! You've just finished a game of 20 questions with Chris Taylor...

[Marcus Miller]

Originally posted by Chris Taylor@Aug 28 2005, 06:57 PM
They make exceptions all the time... wasn't the original 1.8 SM way over the limit? Who's to say they can't make an exception on this?

Not having any clue as to how close competitive ITA-RX7's and ITB cars are (since there are none of the above in my division), how far off are the two cars? Would the RX7 really need to be turned into a tank to run in ITB? Why not just remove the carb allowance? Does anybody run anything but the stock carb?

Congratulations! You've just finished a game of 20 questions with Chris Taylor...

[snapback]59161[/snapback]

There is definitely a precedence for it; SM for sure, and I believe A sedan...
No one I know runs an alternate carb.
ITB is also dead here in Norcal.
Socal has some competitive ITB cars but no ITA 7's, everyone runs Pro7.
Marcus

[lateapex911]

The currently accepted "proper build" HP level is about 130 plus at the wheels, or about 150+ at the flywheel.

RX-7 power is funny...if you talk to Mike Van Steenberg at ISC in FL, he says 115 at the wheels is more realistic, but others (Yaw, Susko) say they see more. The cars in the SE run veeeery strong...suggesting that they must be putting down more than 115.

So, at 133 say, the Rx-7 would need to gain some weight to run in B. Around 100+ lbs.

There is the issue of the change to narrower rims, but that is considered (rightly or wrongly) to be somewhat minimal.

And while actual lap times must be taken with a HUGE grain of salt, looking at some large amounts of significant data suggest that as is, the RX-7 would be a tad strong for ITB. Nobody, even members of the ITAC who own RX-7s want the car to be an overdog.

The cage situation HAS seen exceptions, and DOES have some irregulaties and inconsitancies, however, there is an awareness of that among the rulesmakers, and a desire to clean things up in that regard. So, at this point, exceptions are pretty much a non issue.

The cars only real option in a movement to ITB classing, is a restriction of power. The approximate flywheel number would have to be limited at 140 max, wheel hp to 114 or so, if it were to stay at it's current weight and avoid recaging. It is thought that most ITA cars built with .095 cages would balk at recaging.

Rotaries are tricky to class though, as the torque numbers are dismal. My cars last engine showed about 130hp at a bit over 7K rpm at the wheels and 103 pound feet of tq on a Clayton dyno. (Known to yield strong numbers compared to a Dynojet, for example).

So, a move to ITB would require a properly sized SIR, and a change to 6" wide rims, if it were to stay at it's current weight.

Or maybe a little sugar in the Nissan and Honda tanks in ITA might do the trick there,

[Jake]

Jake,

Could you explain how a Single inlet restrictor is sized to limit hp? Is it trial and error, or is there a science to it?

[Banzai240]

Originally posted by lateapex911@Aug 29 2005, 06:04 AM
The cage situation HAS seen exceptions, and DOES have some irregulaties and inconsitancies, however, there is an awareness of that among the rulesmakers, and a desire to clean things up in that regard. So, at this point, exceptions are pretty much a non issue.

[snapback]59175[/snapback]

Let's not get carried away here... There have NOT been cage exceptions in IT... Additionally, in an environment where liability issues are becoming more and more prevelant... what do you guys think the likelihood would be that one would be approved??? (we've already been told NO WAY...)

SM, American Sedan, etc... they are their own deal that was done at a different time, for different reason, and really doesn't matter in this situation...

OH, and for whoever suggested that the SM 1.8 was "way over"... Even though we've told you before, I'll say it again... IT WAS NOT... The car, as currently classified, fits the process... in fact, I personally think that we overestimated the HP potential, but it's better to be a little on the conservative side...


As for an SIR... The GT rules are experimenting with the use of a Single Inlet Restrictor... A device which looks a lot like a venturi that goes at the beginning of the airstream... You'll see them on certain proptotype cars, Formula 3, etc...

I don't know all the science, but the way it works is that it creates a situation where the restrictor is basically invisible to the system until the airspeed reaches a particular velocity, at which point it will flow NO more air... The air goes terminal and that's it...

According to the GT committee, it IS a science... You decide what you want to limit the HP to, and the formula tells you a size... Pretty slick, really....

[Speed Raycer]

How about not allowing a header on the rotary? We already have rotary specific engine rules, and I'd ASSUME that the use of the stock manifold cuts the power output ability a fair amount. What kind of #'s are the Spec-7 motors putting to the ground???

[Dick Elliott]

Why would you want to change anything, when you have your own RX-7 class (IT7) in the MW region. You should be happy with the present rules. People tryed for a long time to get IT7, so leave it alone, and go racing.

[Chris Taylor]

Originally posted by Banzai240@Aug 29 2005, 01:35 PM
OH, and for whoever suggested that the SM 1.8 was "way over"... Even though we've told you before, I'll say it again... IT WAS NOT...

[snapback]59185[/snapback]

Have you ever read the GCR? At 2400 pounds, unless the driver of the car is a lardass, the 1.8 would require .120 wall. 2400 pound requirement, over 2200 (no driver) has to use .120. At the CURRENT WEIGHT, yes, it fits for most people. At the PREVIOUS, LONG STANDING WEIGHT, no.



Back on topic, I tend to agree more with Dick than with the "move the RX7 to ITB" mentality. For those that haven't tried to get a class going, it's a helluva lot easier than dealing with the CRB. The ruleset doesn't have to be in the GCR if it's a class specifically for ITA-prepped RX7's (with or without a spec tire). If every division has it (and every division should be able to support it) it's a nationally recognized class!

[Andy Bettencourt]

Chris and Darin - you are talking about different things. Chris is talking about the cage exception that the 1.8 Miata got at (then) 2400, now 2350.

Darin is talking about the weight suggested to the CRB for re-classification of the 1.8 in ITA...

AB

[Speed Raycer]

Originally posted by Dick Elliott@Aug 29 2005, 11:53 AM
Why would you want to change anything, when you have your own RX-7 class (IT7) in the MW region. You should be happy with the present rules. People tryed for a long time to get IT7, so leave it alone, and go racing.

[snapback]59200[/snapback]

Easy there Dick. I'm very happy that we can run IT7 here in MiDiv. I was one of those people that "tried for a long time to get IT7". Do you really think I look forward to being in the same class with Chris Albin???? :119:

However, through bad luck and timing, we've had >4 IT7 cars competing regularly this year. Looking down the road, I'd rather have the car classed competitively SOMEWHERE when MiDiv looks at the numbers and says it's not worth the separate class.

If it's going to be reclassed, I'd also rather not have to put another new cage in the car if there were ways to keep it at it's current weight.

[Dick Elliott]

I understand 100%. Looks like a large # of cars in Texas region are going to NASA and pro7. AHRA and IHRA both at one time had more classes than cars. Thats what NASA has done. Spec this and spec that, untill you only run against cars like your own. DICK.

[dyoungre]

Jake,
I used 1.5x0.120 and I totally support what you asked. Anyone else out there use 1.5 x .120?

[Marcus Miller]

Originally posted by Dick Elliott@Aug 29 2005, 09:53 AM
Why would you want to change anything, when you have your own RX-7 class (IT7) in the MW region. You should be happy with the present rules. People tryed for a long time to get IT7, so leave it alone, and go racing.

[snapback]59200[/snapback]

No IT-7 here
*Back* to NASA I go?

Marcus

[Marcus Miller]

Originally posted by Speed Raycer@Aug 29 2005, 08:31 AM
How about not allowing a header on the rotary? We already have rotary specific engine rules, and I'd ASSUME that the use of the stock manifold cuts the power output ability a fair amount. What kind of #'s are the Spec-7 motors putting to the ground???

[snapback]59195[/snapback]

My Pro7 (ITA engine rules sans header, and requiring an 81-85 intake carb combo) put down 118 horse on a dynojet. Most dyno between 113 and 118. 118 is the high end.
This was with a 2.5 inch full ength exhuast with dynomax ultra flo muffler & a Yaw -ish carb

Marcus

[Chris Taylor]

Thanks for translating, AB.

[lateapex911]

I don't think IT7 is the best solution. It doesn't exist in many areas, and really, I would prefer the variety of the class I joined.

IT-7 is really the sign of a problem, and a band aid solution at best.

The solution is to have cars classed with a chance to run at the front no worse and no greater than any other.

Unfortunately, that's a tall order.

In terms of moving the car to ITB and using a stock manifold to restrict the power, that wheel number is too low to fit competitively.

A move to B would require, basically, 12 new wheels, (race, test and rain tire sets) a change in tire section, (due to lack of sizes avaible) which would likely result in an overall diameter change, necessitating the re-gearing of the axle.

Then there would be the testing and re-setup to accomodate the change in ride height and change in center of gravity.

A move to B isn't easy!