Hi, my apexi commander shows very low engine knock when engine is ticking over and when the revs increase so does the engine knock. I don\'t know a great deal about engines so I\'m just trying to understand more things, cheers.
Whoops! What I was ment to ask was, is this normal?, cheers.
Yeah, knock (a.k.a. Det or Detonation or pinking) is caused by the fuel igniting too early, so instead of a nice smooth explosion forcing the rotors round you get a series of irregular ones. This puts all sorts of horrible stresses on the tips and causes tehm to break off.
When the engine detects knock, it retards the spark timing to alter the moment when they fire, thus smoothing out the exposions again. Its usually caused by running too lean.
Now, the knock sensor on the RX7 is a microphone placed next to the engine block, which is crap to be honest. Just because the commander shows knock all its actually showing is signals which the microphone interprets as knock (my dump valve sets mine off). My understanding is that as you put the foot down, you should get LESS knock (more throttle = more more fuel = richer mixture). this leads me to believe you have a crap sensor!!!
Knock is only a problem on wide-open throttle so if you are all mapped up properly i wouldn;t worry about it too much.
HTH
graeme
Cheers for the info fella!
Might be an idea to get an air/fuel gauge to check to see what the fueling is like :)
Can you guys give me some advice about knock levels. Just purchased a single turbo converted rx7 using a power fc. I was amazed to see the knock levels, cruising at 60-70mph the knock is around 20-30 with very rare occasional peaks to 40-50. The engine still has warranty so I spoke to the builder who assured me it was normal. The reason I find this odd is I also have a moddified impreza sti with a power fc, it normally never goes higher than 5/6 with a very occasional high of 15.
Can someone put my mind to ease, thanks.
yeah thats fine. knock is measured by a microphone which picks up all engine vibrations, and then looks for noise spikes within certain frequencies. different engines and different sensor locations will give different values, and so you are looking for things out of the ordinary rather than actual values. also, depending on the sensor you will tend to get more general noise at higher revs, and so knock levels will tend to rise (although some monitors can account for this)
Thanks for the reply Marco.
i was wondering about the knock aswell cheers for all the info
Kris
Knock readings can also be affected by the exhaust popping which makes the figures jump.
My Purple FD never went over 38 knock level, whereas the satin FD would jump over 100 if there was a exhaust pop at high speeds