Rev limiter for Carb'd cars

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DAlgozine
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Postby DAlgozine » Sun Oct 12, 2014 7:56 am

PeteL wrote: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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Postby TX#11CMC » Mon Oct 13, 2014 7:21 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 ?

Are you saying running a carb is heavier than running FI?
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Postby nape » Mon Oct 13, 2014 2:07 pm

TX#11CMC wrote: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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Postby TX#11CMC » Mon Oct 13, 2014 5:13 pm

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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Postby nape » Mon Oct 13, 2014 6:01 pm

TX#11CMC wrote: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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Postby aschroeder » Tue Oct 14, 2014 8:33 am

TX#11CMC wrote: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. ;^)


How much torque was he making? I am curious because I have yet to see a Ford carb setup making more than low 280s.

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Postby TX#11CMC » Wed Oct 15, 2014 4:45 pm

aschroeder wrote:
TX#11CMC wrote: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. ;^)


How much torque was he making? I am curious because I have yet to see a Ford carb setup making more than low 280s.

Not sure, I'll find out though. We have two carb guys in TX.

I'm on my 3rd EFI motor over 9 years and the most TQ I ever made was 291. My current motor is at 284. I guess those in the 300's for TQ are the lucky ones.
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Postby Trublu » Thu Nov 06, 2014 8:56 am

I swapped from EFI to the carb set up last year in an effort to simplify the car's wiring and general under hood stuff. Additionaly I'm more familiar with them than EFI so I felt any issues could be addressed at the track more readily.

There is a weight savings there but I'm not sure I'd go to the trouble and expense to save it. Much easier to remove the strut tower brace if you are running it, the weights are comparable.

In principal if I were required to run a rev limiter I would, I actually considered it when swapping to the carb set up, but it would add a component that could cause engine failure at some point so I'd very much prefer not to.

I think the over riding question is why require a rev limiter. Aaron makes some very valid points; anything past an RPM around 5600-5800 is on a declining torque curve; and revs within the torque curve can be managed by rear end gear ratio to the track.

I had some close races with other mustangs and 4th gens, I see no performance advantage to running a carb. Arguably I'm giving away some torq.

I think this RCR does not address a real issue.
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Postby DAlgozine » Thu Nov 06, 2014 9:21 am

Trublu wrote:I swapped from EFI to the carb set up last year in an effort to simplify the car's wiring and general under hood stuff. Additionaly I'm more familiar with them than EFI so I felt any issues could be addressed at the track more readily.

There is a weight savings there but I'm not sure I'd go to the trouble and expense to save it. Much easier to remove the strut tower brace if you are running it, the weights are comparable.

In principal if I were required to run a rev limiter I would, I actually considered it when swapping to the carb set up, but it would add a component that could cause engine failure at some point so I'd very much prefer not to.

I think the over riding question is why require a rev limiter. Aaron makes some very valid points; anything past an RPM around 5600-5800 is on a declining torque curve; and revs within the torque curve can be managed by rear end gear ratio to the track.

I had some close races with other mustangs and 4th gens, I see no performance advantage to running a carb. Arguably I'm giving away some torq.

I think this RCR does not address a real issue.


Likely in your particular situation, it wouldn't make a difference to have a rev limit, which likely is the case for many.
However, if someone (already been done) built some very solid internals (no one ever checks), ran a low rear gear (3.08-3.23 ish), and rev'd the snot out of the car, they would:
Eliminate several shifts per lap.
Provide additional options to shift or not shift, depending on circumstances.
Be able to hold a gear in various situations, including: a particular section where most need to shift, and off line while racing hard.
All of which is an advantage over all other cars with limits.

Again the whole point of the class is to keep it simple and cost effective. This closes a loop hole for spending big money to gain an advantage. And to answer the question ...again. Yes this has already worked as an advantage......and yes on a big stage. And likely someone else will in future. And no....its not killing the entire class, but whats wrong with getting items figured out before they become a big deal...again ?
Dave Algozine

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Postby jim » Wed Nov 19, 2014 3:23 pm

Dave says,
Again the whole point of the class is to keep it simple and cost effective. This closes a loop hole for spending big money to gain an advantage.


In a way, cost is relative. I do 99% of all work myself as someone else may elect to farm it out driving up their costs that way. Do you put your $ in someone else's pocket or do you build it yourself and put the $ in the motor or any other part of the car?

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Postby DAlgozine » Wed Nov 19, 2014 3:29 pm

My reference to cost relates to expensive internal engine parts, which are illegal, but are nearly impossible to police. And expensive as it relates to spinning an engine to higher RPMs leads to breakage and higher wear.
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Postby nape » Mon Nov 24, 2014 6:31 am

No need for even expensive parts. My AI engine is a 2-bolt main, stock cast crank, Eagle I-beam rods (cheaper than getting stock rods resized + ARP bolts), and hypereutectic cast pistons. It's seen 7600RPM according to the tell tale.

Does it make sense to spin a CMC engine like that? No.

Like I've said before, I'd concede a rev limiter to get AL heads any day. :wink:
TJ Bain

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