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Rev limiter for Carb'd cars


D Algozine

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I've been biting my tongue on this since I've yet to get the car together, but I really agree with Pete's post.

 

Every chassis has a handicap in one way or another. Has anyone even looked at dyno sheets to see if this is a possible red herring before we go Dianne Feinstein on this?

 

I can understand that it may be frustrating for someone to be able to hold a gear longer, but what's next? Spec final drive ratio? It's sure frustrating when someone else chooses the right ratio and they don't have to shift and you do. Same theory.

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I can understand that it may be frustrating for someone to be able to hold a gear longer, but what's next? Spec final drive ratio? It's sure frustrating when someone else chooses the right ratio and they don't have to shift and you do. Same theory.

 

I think the key phrase is "chooses the right ratio". The choice in this matter is whether you choose to run carb'd or fuel injection as their is no choice as to your rev limiter when running fuel injection as we are limited to the oem program on the PCM.

 

When Bob was still running his carb'd motor, he would pass me on the straights everytime I had to shift at 5,700 rpm and he could wind his motor out to 6,500rpm. He passed me at RA this way.

 

The question simply comes down to whether or not the directors want to have certain platforms have advantages over the others IN CERTAIN AREAS?

 

To be honest, I think all of the cars should have the same restriction on rpm and it should be set. This would require FI cars to program their PCMs to be the same, but it would eliminate this disparity. This would also eliminate the disparity that can exist on the PCMs. Although I am not an expert, I believe that depending on the year the car was built, the PCM may have different rev limiters programmed in it already. This results in "PCM shopping" whereby individuals will buy certain year PCMs as they have a higher rev limiter.

 

Additionally, limiting the revs easy enough to check on the dyno.

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We can't have one limiter to rule them all, that would only work if everyone had the same engine. AFAIK autos and manuals are the only ones that have differing limiters and the rest are all the same regardless of year. Doesn't a Fox body have a limiter if running the factory distributor with brain box? Someone school me on that one, because I could swear that they do.

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If a 3rd gen with a carb can spin 6500, that is reason enough to limit them. If we told everyone today that all limiters can be set to 6500, who here wouldn't make that change? That alone is reason enough to impose a limit. But who says 6500 is the real number? What if today it is 6500 and tomorrow it is 6800? May as well set a limit now so guys dont start dropping coin on crazy springs and valves.

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Even if you spin it up that high almost all cars stop making power at 5800-6000 sometimes less so there is not really a big adv there I don't think.

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

 

bryan_dyno_2014_zpsa40b690b.jpg

 

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

 

Bryan

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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.

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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.

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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.

 

 

A9F31C29-1A1F-40E2-9C64-ACE470885FC9_zpspvuwdu6r.jpg

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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

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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 ?

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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!

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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.

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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.

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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.

 

 

I'm gathering Bryan is not in favor.

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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.

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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?

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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.

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Is there any evidence that carb cars are running amok and need to be reined in? Have the carbed cars been dominating at the regional or national level? First step in solving a problem, make sure there is really a problem.

 

Not sure I'd say this is problem, but it already has been taken advantage of at the National level. 2013

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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 ?

Are you saying running a carb is heavier than running FI?

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Are you saying running a carb is heavier than running FI?

 

With iron boat anchors, absolutely.

 

I guess it's different for the 302 Ford camp, because the 3rd gen stock FI is such an effort in pissing into the wind for 260/310 that we don't even think about it. In my mind, the 3 options are carb small block, LT1, LS1.

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Thanks TJ, that is what I was guessing. We had a Ford racer switch over to a carb recently and I think I remember him stating it was about 25 lbs lighter.

I'm still not quite sure what that 45 lb disadvantage is Bryan was talking about. If it is iron heads then we can put the 302's in the same camp. ;^)

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Thanks TJ, that is what I was guessing. We had a Ford racer switch over to a carb recently and I think I remember him stating it was about 25 lbs lighter.

I'm still not quite sure what that 45 lb disadvantage is Bryan was talking about. If it is iron heads then we can put the 302's in the same camp. ;^)

 

Iron heads are what I was talking about in a round about way. I have no doubt that a carb setup is lighter than a TPI or 302 Ford EFI setup. I believe the 25# number is probably close, too.

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