Rev limiter for Carb'd cars

Questions and answers about CMC and NASA rules

Moderator: Al Fernandez

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Tue Oct 07, 2014 2:50 pm

The advantage is the ability to hold a gear another 100 to 200 ft allowing for no shift.
Texas Region AI/CMC Series Director
Inferior Driver, Superior Platform…. since 2005.

User avatar
roadracerwhite
Posts: 361
Joined: Mon Oct 15, 2007 8:06 am

Postby roadracerwhite » Tue Oct 07, 2014 3:12 pm

I thought I would post my dyno sheet just to throw some data out there.

Image

Personally, I don't want to add another component which has the opportunity to fail. I shift my car around 6000-6200 rpm.

Bryan
Bryan White
#18 CMC
Former Midwest CMC Director

suck fumes
Posts: 458
Joined: Thu Jun 28, 2012 4:21 pm

Postby suck fumes » Wed Oct 08, 2014 4:51 am

But what's the difference between the rev limiter and using diff gear ratios? They both have the same adv and the gear swaps are legal.
2013 CMC NATIONAL CHAMPION

Motorsportheaven.com

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Wed Oct 08, 2014 5:26 am

Gear swaps affect mechanical leverage. So running a taller gear results in a loss of torque multiplication. Sort of offsets.
If we have the same gear, I shouldn't have an rpm disadvantage. The carb guy gets the same torque multiplier and can hold the gear longer if needed/when needed.
Texas Region AI/CMC Series Director

Inferior Driver, Superior Platform…. since 2005.

User avatar
aschroeder
Posts: 41
Joined: Wed Aug 03, 2011 9:03 am
Location: Fresno, CA

Postby aschroeder » Wed Oct 08, 2014 7:43 pm

Dyno sheet for my throttle stopped, carb'd 302 from 2013. Had the tuner set me on the conservative side because it was the dead of summer in Fresno (115F) and I was headed to Laguna Seca (70s) and I didn't trust the mobile dyno they were bringing (turned out to be moot and the car made identical numbers). The car can easily make the horsepower number, but doesn't make anymore torque. I need to experiment with smaller headers I guess.

The car has always raced with a MSD limiter, mainly because I don't trust myself not to float the valves or worse. I have 6,000rpm pill in it. The factory duraspark II box has no electronic rev limiting capability.


Image

DAlgozine
Posts: 309
Joined: Tue Nov 18, 2008 8:19 am
Location: Crown Point, IN

Postby DAlgozine » Thu Oct 09, 2014 7:55 am

For those who don't think an RPM limit is a good idea for the carb'd cars, for whatever your reasoning is, are you all ok with removing the RPM limit on ALL cars? Because personally, I know there are couple locations at a couple tracks that I would love to have the extra 100-200 RPM's and not have to lift or shift, especially when I'm in a heated battle with someone, and end up on a less then ideal racing line. I'm all for making it fair, across the board.
This change can tie right into, being able to have the non-essential computer items removed....While the computer is being modified, just eliminate the RPM limit :D
Dave Algozine
CMC #12

User avatar
roadracerwhite
Posts: 361
Joined: Mon Oct 15, 2007 8:06 am

Postby roadracerwhite » Thu Oct 09, 2014 9:59 am

If we as carb cars have to have a rev limiter, can we have aluminum heads so we can get rid of that 45 lbs of disadvantage an advantage which most of the fi cars have ?
Bryan White

#18 CMC

Former Midwest CMC Director

User avatar
wastntim
Posts: 298
Joined: Tue Mar 31, 2009 7:07 pm

Postby wastntim » Thu Oct 09, 2014 10:47 am

roadracerwhite wrote:If we as carb cars have to have a rev limiter, can we have aluminum heads so we can get rid of that 45 lbs of disadvantage an advantage which most of the fi cars have ?



I vote Yes!
:D
Robert #24
NASA Midwest - CMC2
HeavyImpactMotorsports@gmail.com
Sponsor: Cassidy Tire/Tiresdirect.net & CTW Motorsports

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Thu Oct 09, 2014 11:03 am

roadracerwhite wrote:If we as carb cars have to have a rev limiter, can we have aluminum heads so we can get rid of that 45 lbs of disadvantage an advantage which most of the fi cars have ?


You could put an LT1 in yours and have all that. I can't put a carb on mine.
Texas Region AI/CMC Series Director

Inferior Driver, Superior Platform…. since 2005.

User avatar
roadracerwhite
Posts: 361
Joined: Mon Oct 15, 2007 8:06 am

Postby roadracerwhite » Thu Oct 09, 2014 11:14 am

Glenn wrote:
roadracerwhite wrote:If we as carb cars have to have a rev limiter, can we have aluminum heads so we can get rid of that 45 lbs of disadvantage an advantage which most of the fi cars have ?


You could put an LT1 in yours and have all that. I can't put a carb on mine.



But you could sell your car and buy/build a carbed third gen to not run a rev limiter if it is such an advantage.

I don't want to run fuel injection. I really don't want a rev limiter. I don't want to go cutting into my distributor wiring just to install something which could fail.

For a class with a history of banning anything or anyone with the MSD logo on it, we sure are excited to jump into something which just isn't necessary.

And if you make me install this bullshit, EVERYONE better be checked at every event. what kind of tolerance or equipment are you going to have to check it? Most tachs aren't accurate enough to use.
Bryan White

#18 CMC

Former Midwest CMC Director

User avatar
wastntim
Posts: 298
Joined: Tue Mar 31, 2009 7:07 pm

Postby wastntim » Thu Oct 09, 2014 11:30 am

roadracerwhite wrote:
And if you make me install this bullshit, EVERYONE better be checked at every event. what kind of tolerance or equipment are you going to have to check it? Most tachs aren't accurate enough to use.


:o

I'm gathering Bryan is not in favor. :wink:
Robert #24

NASA Midwest - CMC2

HeavyImpactMotorsports@gmail.com

Sponsor: Cassidy Tire/Tiresdirect.net & CTW Motorsports

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Thu Oct 09, 2014 11:32 am

Biased.
I don't like changes to 4th gen either. Biased? Sure.
Texas Region AI/CMC Series Director

Inferior Driver, Superior Platform…. since 2005.

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Thu Oct 09, 2014 11:37 am

Keep in mind guys that once upon a time we had to run OEM valve springs. Now we are limited to anything that drops in without machine work. This is the slippery slope.
Open up springs we were asked.
No reason to require OEM junk.
There are better springs for less or same money.
Well this is the downside. Now that the springs can hold more RPM without float, this should be considered.
Texas Region AI/CMC Series Director

Inferior Driver, Superior Platform…. since 2005.

DAlgozine
Posts: 309
Joined: Tue Nov 18, 2008 8:19 am
Location: Crown Point, IN

Postby DAlgozine » Thu Oct 09, 2014 1:18 pm

roadracerwhite wrote:If we as carb cars have to have a rev limiter, can we have aluminum heads so we can get rid of that 45 lbs of disadvantage an advantage which most of the fi cars have ?


My answer would be yes...........but I don't see that getting approved anytime soon. But in all seriousness, why not write up a request for aluminum heads for all cars. Why not ??
I've asked the question in the past, but what's the point of the class,...mostly stock cars ? ........or cost effective , equal cars? Because if its cost effective , equal cars, then there needs to be a shift in thinking and some "more" changes to complete that goal, but as we have heard from many..........change is bad.
Trying to keep 4 different platforms that have several different versions of each platform mostly stock, cost effective and equal is a huge challenge.
Like we say in contracting work, you want it fast, cheap or done right? You can only have 2 of the 3.

Heres my concern about no RPM limit.......there is not limit. How can there be anything in a severely limited mod class that has not limits on something?
Dave Algozine

CMC #12

User avatar
roadracerwhite
Posts: 361
Joined: Mon Oct 15, 2007 8:06 am

Postby roadracerwhite » Fri Oct 10, 2014 5:45 am

Glenn wrote:Keep in mind guys that once upon a time we had to run OEM valve springs. Now we are limited to anything that drops in without machine work. This is the slippery slope.
Open up springs we were asked.
No reason to require OEM junk.
There are better springs for less or same money.
Well this is the downside. Now that the springs can hold more RPM without float, this should be considered.


Here we go again with the texas rule book. If we are allowed to use any spring, why would we be limited to those without machine work. Isn't that the whole point to allow everyone to use cheaper and more reliable parts? Isn't that one of the goals of change requests.

The vortec head I am using off of a truck have unique valve springs to vortec heads, when I got them redone for CMC (they had several broken valve springs) I had them changed over to the more regular springs, all of the pockets had to be machined for this. Besides not one of us is an expert on valve springs. So why do we continue to worry about these things we can't possibly check. Oh we can check them, I don't know about anyone else, but I could not tell you if your valve springs are legal or not.

Every year I find out about some illegal insignificant part which is fine in every other region, somehow is taboo and gospel in Texas. SFI steel flywheels is an example. A heavier flywheel, I had assumed it was legal for years, wrong. I was told it could be an advantage, a heavier flywheel an advantage? Here I had a safer part on my car for years not realizing I could be dq'd for it. And for what, it made the car slower anyway.
Bryan White

#18 CMC

Former Midwest CMC Director


Return to “Rules Questions/Answers”

Who is online

Users browsing this forum: No registered users and 2 guests