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Rev Limiters like the Bee-R Rev Limiter are used for the purpose of capping your RPM's so that your car will not rev passed the limit it is set at. The Bee-R rev limiter works by cutting the ignition upon hitting the rev limit. This is prefered over fuel cut because, according to the site:

Fuel cut, as used on many standard vehicles, risks damage to high performance engines when at high revs.

Rev Limiters offer a solution to change the stock limit and not have to worry about spooling your RPM's over the red line. Most modern cars have built-in rev limiters. But being able to change the limit can be a good modification to help improve launching of the car from a stop, or setting it at low rpm for a car's break in period.

My question is, when using a rev limiter (and hitting the rpm limit as intended), will this cause any wear on the engine? Is it safe to be hitting the rev limit in this way?

  • Is this on a pretty stock street car, or a modified racing car? Stock exhaust? – JPhi1618 Mar 23 '18 at 19:04
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    Going to the extreme on any engine is going to wear it out faster than if you run it at normal speeds (driving). Obviously, if the engine is built to take the higher revs, it's going to last longer at that high end RPM level, but it's still going to fail faster than if it was only run at the lower RPM levels. Would highly suggest you read a book by Carroll Smith called Engineer to Win. It tells a lot about metallurgy and why engines fail. – Pᴀᴜʟsᴛᴇʀ2 Mar 23 '18 at 21:15
  • @JPhi1618 This is for a modified Subaru Impreza STI – tqrecords Mar 25 '18 at 20:45
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I'll admit that I don't have experience with these rev limiters, and I'm drawing conclusions from other experience. That said...

On cars with catalytic converters in the exhaust, when the engine detects a misfire, the check engine light flashes rather than just coming on steady to let you know there is an immediate, important issue. The idea is that when unburnt fuel gets into the exhaust, it can ignite in the catalytic converter because of it's high heat, and if this happens too much, the cat can burn out and ruin itself.

I assume that stock limiters cut the fuel so that unburnt fuel isn't allowed in the exhaust. I would think the engineers would prefer that safety over possible overheating, because a normal driver would only hit the limiter because of an accident with the clutch or transmission, etc.

So, if the device cuts ignition, but fuel continues to inject into the cylinders its like you're manually causing a misfire. Of course, an actual misfire problem can cause the cylinder to not fire as long as you continue to drive (seconds - minutes). A rev limiter is only going to kick in for very brief intervals, and probably not that often.

  • Is it safe to assume with the info you have provided that ignition rev limiters are safe to use and also safer that fuel-cut limiters? – tqrecords Apr 8 '18 at 17:49
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    @tqrecords, I was thinking that fuel-cut would be safer since that is what manufacturers are using, but again - I'm not an expert. To me it seems like taking combustable fuel out of the equation is safer and more fuel proof than letting fuel flow and cutting the spark. What happens to that unburnt fuel? – JPhi1618 Apr 9 '18 at 3:27
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The limiter does not cause any damage.

How you use the limiter, and how often you wind the engine to said limit is a completely different question.

As a generality, it is not going to be detrimental for you to set a limit which is relative for your build. Being greedy and setting it too high is asking for trouble, obviously. Cutting Ignition is far better than Fuel, yes. Cutting Fuel would cause overheating.

Without specifics, this query is going to get a lot of subjective replies, though.

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