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!!

59137


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...

59161


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.
59175



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...
59185
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! :happy204:

[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.

59200


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.

59200


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???

59195


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. :smilie_pokal:

[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!

[dyoungre]

Originally posted by lateapex911@Aug 30 2005, 06:37 AM
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!

59265

Jake,
I understand your point; I think that ANY change will require a financial and sweat equity impact, and I don't want to minimize that fact. I think it is cheaper in the long run, though, than selling an uncompetitive car and buying/building a new car simply because it is (now) better classed.

The more I think about it, the more I like the idea of an overlap rule for recognized tweeners: race ITA at one weight with ITA wheels/rules, and ITB at a higher weight with ITB rules. No car should be classed as such as new, but I could see legacy cars being allowed the opportunity to compete in the lower class.

[Jake]

Originally posted by dyoungre@Aug 30 2005, 01:19 PM
The more I think about it, the more I like the idea of an overlap rule for recognized tweeners: race ITA at one weight with ITA wheels/rules, and ITB at a higher weight with ITB rules. No car should be classed as such as new, but I could see legacy cars being allowed the opportunity to compete in the lower class.

59285


That sounds like an excellent idea. Why not?! If I drove a Miata I could pick and choose what class I wanted to run in.

[ddewhurst]

***The more I think about it, the more I like the idea of an overlap rule for recognized tweeners: race ITA at one weight with ITA wheels/rules, and ITB at a higher weight with ITB rules. No car should be classed as such as new, but I could see legacy cars being allowed the opportunity to compete in the lower class.***

I also like this as a method of allowing car owners to make THEIR DECISION on which class they run. Many of us understand that we will not win given either class. Or at least we SHOULD UNDERSTAND. :023: Given the choice of A or B I would continue to run A. I can live with doing my best at lowering my lap times in A & finishing less than 1st. If there comes a day when I have a desire to win then I can spend whatever & change to B.

[mustanghammer]

My car was originally built with 1.75x.120 tubing in the mid 90's. Now it has a mix of 1.5x095 and the original 1.75x.120 tubing. All of the ITA/EP RX7's that I have seen built in KC have 1.5 X.095 tubing.

I would also support dual classing of the RX7 between ITA and ITB. As one of the 4 MiDiv IT7 regulars I too think that the ability to compete competitively in an offical IT class offers me more of a future in IT.

[dickita15]

Well I have three cars in my shop, two of which are being activley raced. I checked today and they are all 1.75 tubing ranging from .100 to .137 (wow) thickness.

i would love to hear more real world data

[dickita15]

I spoke with another car owner last night 1.5 x .120. It looks like many of have heavy cages.

[Speed Raycer]

Originally posted by dickita15@Aug 31 2005, 06:11 AM
I spoke with another car owner last night 1.5 x .120. It looks like many of have heavy cages.

59367

LOL by my count in this topic, its 6 .120+ to 5 .095's... not counting every RX built by KC Raceware using .095. If they only built 1, then were running 50% ;)

[dyoungre]

Originally posted by Speed Raycer@Aug 31 2005, 02:23 PM
LOL by my count in this topic, its 6 .120+ to 5 .095's... not counting every RX built by KC Raceware using .095. If they only built 1, then were running 50% ;)

59389


I was suprised by how many cages were built with .095, but I think the knowledge that it is 50/50 could support making a decision that provides an opportunity for 1/2 the existing cars.

[Speed Raycer]

If it truely was 50/50, then the dual class @ different weights might work. Those cars that are 10/10ths with the .095 cages can run in A @ 2380/2200 and those with the heavier cages have the option of B @ xxxx/>2200

Other options.... ITB cars get rear drums, 81-85 intake manifolds and ....

IMO, the biggest thing to slow the car down would be the exhaust and possibly the Intake manifolds being restricted to 81-85's. Most guys seem to be running a "stock" Nikki carb anyway.

Personally, I'm so slow in my RX that I end up racing the B guys anyway (and loosing) :D

[mustanghammer]

"not counting every RX built by KC Raceware using .095. If they only built 1, then were running 50%"


KC Raceware has built 3 ITA RX7's, 1 ITS 2nd gen and 3 EP first gen RX7's

Of the ITA cars:

1 ITA RX7 is owned by someone in KC - 1st IT car that KC Raceware built
1 was killed at an ARRC by Charlie Clark - it's cage is in an another car that is nearing completion
1 was converted to E Production - Chuck Clark's car

They didn't build my car all though it has a Nico fabricated exhaust and a Nico installed driver's door bar.

So there is one out there but it is inactive at present.

Regarding the ITB ideas that are floating around. I really like some of the restrictions that are being proposed instead of adding massive amounts of weight. A heavy car on narrow rims will be a tire and brake killer. Not to mention that this would be hard on already fragile front spindles. I would much rather give up a header and my rear disks than add another 100lbs to my already bloated ITA/IT7 car.

[ddewhurst]

Those of you that think giving up the rear disc are a good idea obviously race on tracks where required HARD braking is not required. My second race out in my at the time SRX7 at Blackhawk Farm was with 75% rear shoe remaining & 10 laps in the brakes went south. The rear shoes were GONE.

The car never went on track again untill the disc brake rear went in & it will never go on track again without rear discs.

BAD IDEA folks.............

[dickita15]

I agree david
if weight is not an easy way to limit performance on tweeners that I would rather limit power that hurt brakes.

a question for the ITAC guys. has there been any discussion of the SIR restritor like the are now useing in GTL instead of the more conventional flat plate. It seem like a pretty cool piece.

[Dick Elliott]

What do you think we used for the first few years of IT? Rear disc were not allowed in IT on a RX-7 for several years after the class became a SCCA class. I think 84 was the first year, and rear disc were not legal untill the 85s became legal for IT. We did just fine with rear drums, and I know people who still use them in IT. My own GT-2 RX-7 used drums in the early 80s with no problems. Just a tale from the past.



The car never went on track again untill the disc brake rear went in & it will never go on track again without rear discs.

BAD IDEA folks.............

59433
[/quote]

[mustanghammer]

Originally posted by ddewhurst@Aug 31 2005, 07:16 PM
Those of you that think giving up the rear disc are a good idea obviously race on tracks where required HARD braking is not required. My second race out in my at the time SRX7 at Blackhawk Farm was with 75% rear shoe remaining & 10 laps in the brakes went south. The rear shoes were GONE.

The car never went on track again untill the disc brake rear went in & it will never go on track again without rear discs.

BAD IDEA folks.............

59433



Okay, I agree. I seem to recall that Charlie Clark had the same experience with his fisrt 1st Gen RX7 when it was in ITS. I would and will not propose this.

Devils Advocate here:

With some exceptions there seems to be an agreement that the 1st Gen RX7 12A cannot compete in ITA. From the paper and on track data that I have seen in the Midiv and at the ARRC the 1st gen RX7 is a good fit in ITB as is. So why does an RX7 need to give anything up, other than 7" wheel width to compete in ITB? Under what formula is an RX7, a car that has no torque but decent HP, an instant over-dog in ITB?

Flame away....but seriously what is the objective reason why this is not true?

[lateapex911]

Not that lap times should be taken with too much importance, butttt.....

Last years ARRC laps, in equal track conditions:

IT7: Lukas- 1:47.3
ITB: Blethen- 1:48.6
ITA: Serra- 1:43.3

IIRC, LOL, there was about 1.35 second or so differenece on a track almost 2 minutes long. Of course the track isn't representive of every track, but, ...

Well, the ITA cars were running 1:43.3, so the RX-7 was closer by far to ITB than ITA, LOL

[lateapex911]

OK- let me suggest some big picture thinking here....Blue sky stuff.

Question 1-
IF the car can't go to ITB for whatever reason, what would you do in ITA to make it more viable. Remember, blue sky, but show your math, so to speak.

Question 2-

If the car goes to B, how will you make it fit?


Dick- The SIR is an item being discussed, but there are no immediate plans to implement it to any specific car as far as I know, at this time.

The joy, from what I understand, of the SIR, is, unlike the typical plate restrictor, is that it is "invisible" to the system until it reaches it's effect threshold, then that's it...no more air. So, throttle response is unaltered, midrange power is the same, but peak hp is capped.

The other cool thing is the simplicity of the item. The math, from what I understand is clean and consistant. You buy the little donut looking thing, and put on the end of your snorkel. All air passes thru it, and thats it, you're done.

It is very common in many classes, you can see it on the ALMS LMP2 cars in the nose, and hanging off the sides of certain Formula cars. It's been around for awhile, and has a good reputation. As the shape has already been optimized it is basically tamper proof.

From MY point of view, it seems like an item that can make a car that is a current overdog for a class, and has weight issues, fit the class in an easy to check, and cheap way.

[Eagle7]

Sorry to go a little off-topic, but is there any reason why an SIR wouldn't have been a good choice for the BMW in ITS? How would its effect on a 12A compare with its effect on a boinker?

[lateapex911]

I think an SIR is a very viable option for the E36.

I think, (it's being researched as we speak) that it could be very effective on a rotary.

[Marcus Miller]

Based on the ARRC lap times form last year, it loks like we need to pick up 4 seconds, which seems extremely difficult, or lose a second.

I'm assuming the quickest and easiest way to pick up four seconds at Road Atlanta would be horsepower.. the only way to do that is porting, similar to what is allowed for piston motors. I think we all know (believe) that is not going to be allowed, and likely would not be enough, anyway.

To lose a second per lap, maybe I'm way off base, but I think the 6 inch wide wheels would do it; beyond that, maybe restrict the cars to only using stock exhaust manifolds?

Marcus

[lateapex911]

Originally posted by Marcus Miller@Sep 5 2005, 05:31 PM
Based on the ARRC lap times form last year, it loks like we need to pick up 4 seconds, which seems extremely difficult, or lose a second.



we could make the fast guys run on 6" rims and add a few pounds..;)


To lose a second per lap, maybe I'm way off base, but I think the 6 inch wide wheels would do it; beyond that, maybe restrict the cars to only using stock exhaust manifolds?

Marcus

59656


Well, THAT would do it, but the concept scares me....I wonder if we could touch the Audis and Volvos on the straight!

Wouldn't that suck?? A backmarker in A, then a backmarker in B? LOL.

[Marcus Miller]

Originally posted by lateapex911@Sep 6 2005, 12:11 AM
we could make the fast guys run on 6" rims and add a few pounds..;)
Well, THAT would do it, but the concept scares me....I wonder if we could touch the Audis and Volvos on the straight!
I'll go o nthe record, that if we had a cage exception, 100 lbs + 6inch rims wouldn't get an argument from me.


Wouldn't that suck?? A backmarker in A, then a backmarker in B? LOL.

59678

yep! Right as a I finish my car too :unsure:

Marcus

[ScottNutter]

We have 2 more ITA rx7's with 1.5x.120 tubing

[dyoungre]

...and Owen Schefer (Barney, the MARRS Purple Dinosaur) is another 1.5 x 0.120

[fiat124girl]

Our RX-7 has 1 1/2 .095 but we would not be too bothered by cutting out the cage and having to put a new one in. We have been thinking bout doing it anyway because some of the welds are not so pretty.

As long as we have a place to race the 7 I am happy. We built the 240SX to be competitive, the RX-7 is a toy.

[tom_sprecher]

According to my log book I've got the following

Main hoop - 1.75 x .120
All others - 1.75 x .095

I'm going to put the car on scales tonight to see where I'm at.