what is knock?

[tezz12345]

got pfc and ben told when heat light flashes this means knock above 5000 revs what exsactly does this mean

[rx7veilside]

knock is when mr engine knocks on you door and says ime going to screw you big time mother

[chrisJDM]

If you are getting this then it could be bad and you could end up blowing your engine, so take it easy and get it looked at by a specialist.  Means you could be getting detination which is usually caused by fuel issues ie running lean.  Sometimes it is nothing and is caused by a dodgy knock sensor as they are prone to break, but get it looked at or you could cause serious damage to your engine.

[tezz12345]

it has just been mapped and running nice n rich and no knock but heat light flickerd on dash a bit today at around 6k so just worried everthing has been checked n map is good, may be dodjy senser, only has done it when second turbo boosting

[tezz12345]

oh only running 0.8 boost too so should be safe

[tezz12345]

only mods r apexi pfc decat anf exshaust

[chrisJDM]

sounds like you might have a dodgy knock sensor then, they are very prone to breaking.  Mine was dodgy then got a second hand one which was also dodgy then got another one from Tim (rx motors) and has been fine since.  

I think the heat affects them and the material they are held in by melts and goes soft and then they dont work properly

[gsb876]

You have a Apexi PFC yes ?

So next time you give it some boost look at the knock reading to see what it says, anything under 70 is good anything over that is bad, over 100 really bad although if the car backfires it will send the reading higher :King

[tezz12345]

ok great thanks ill do that, thats what i wanted someone to tell me something to check, will look on commader. been so worried bout using commander but red all instuctions and as long as i dont go into settings should be fine

[tezz12345]

tomorrow after work i will moniter knock n see where it is under boost

[tezz12345]

oh and thanks i love this site

[probedb]

the pfc also uses the light for other stuff so not necessarily knock.

[wow]

where by is the knock sensor and how much are they to buy.
 
cheers

[chrisJDM]

you can get them from mazda but i expect they are a bit pricey, you are probably looking at around 100 quid but you can get them second hand, alot of the tuners keep them, although the problem with getting one second hand is it might be faulty aswell

[tezz12345]

my car went to 96 at low revs under no boost when popping and gargling
but stays very low under all boost so think thats all good