ZX rev limiter

oscarloco · Post by **oscarloco** » 13 Mar 2006, 22:15

What kind of rev limiter does the ZX have? I'm afraid to try mine, so I would like to know if it's of the spark retard type or the fuel cut-off type.

AndersDK · Post by **AndersDK** » 14 Mar 2006, 11:24

No rev limiter AFAIK.
Its limited by the ECU max capabilites - except for the strenght of the cam belt. My guess somewhere in the area of 8000rpm.
It would be pretty useless at that rpm as its the max rev it can barely keep itself running.

Note that any petrol engine has a rather steep Bhp curve over the rev increase until the engine design max rpm, from where it drops rapidly, even abruptly, in Bhp going any further in rpm.

oscarloco · Post by **oscarloco** » 14 Mar 2006, 17:57

AndersDK wrote:No rev limiter AFAIK.
Its limited by the ECU max capabilites - except for the strenght of the cam belt. My guess somewhere in the area of 8000rpm.
It would be pretty useless at that rpm as its the max rev it can barely keep itself running.

Note that any petrol engine has a rather steep Bhp curve over the rev increase until the engine design max rpm, from where it drops rapidly, even abruptly, in Bhp going any further in rpm.

Thank God I've never tried it

I have noticed that the engine does not like to be revved >6000 RPM. It can't breath. I want to try it in the strip, shifting at 6000 RPM vs shifting at 5750 RPM (the HP peak) and see which is more efficient. I feel better performance at 5750 but only the clock can tell.

Sl4yer · Post by **Sl4yer** » 15 Mar 2006, 08:55

Even my 1.4i had a limiter, so I'd be amazed if the sporty 2.0i didn't. I would imagine the ECU would adjust the fuelling to stop overrevving. It felt like an on-off pulsing.

Of course, one of the ways Superchip, etc. achieve more power is to raise the rev limit slightly.

Kowalski · Post by **Kowalski** » 15 Mar 2006, 11:13

Sl4yer wrote:Even my 1.4i had a limiter, so I'd be amazed if the sporty 2.0i didn't. I would imagine the ECU would adjust the fuelling to stop overrevving. It felt like an on-off pulsing.

Of course, one of the ways Superchip, etc. achieve more power is to raise the rev limit slightly.

Rev limiters don't work by adjusting the fueling because that leans out the mix which can cause pinking and engine damage. Closing the throttle is a little too slow too (i.e. it takes time to mechanically close the throttle and you can't stop fuel that is already in the cylinder from burning by closing the throttle). Almost universally rev limiters (on spark ignition engines) cut the spark, the downside to that is that the catalyst gets unburnt petrol thrown at it and that is not good for it.

As Anders has said above, most petrol engines have their peak power at a specific point and power drops off above that point. Setting your rev limiter higher doesn't guarantee more power if you've already gone higher than your peak power but it will shorten your engine life.

Bear in mind that there are two things that limit the speed of your engine, one is the strength of your mechanical components e.g. the big end bolts, the other is the speed at which the valve springs can close the valves, at very high revs the valve springs can't close the valves fast enough so you'll get burnt valves/seats. If you go to fast it'll break