High Knock Correction value

[caister]

I took a log for my 20 odd minute communte yesterday using my RStuner and noticed at one point the knock correction value was at 5.25 which i thought was pretty high.

After an email to Henk he seems to think it could be high carbon build up in the engine and that I need to drive it more agressively?!?

I spnd most miles on the motorway but do give the car some beans most days. Could it be time for a new knock sensor or something to add to the fuel to remove carbon build up etc???

Thanks

 

[Jay Payne]

Ive no idea what the readings should be but i got 65 on a different diagnostic system at idle.

 

[Rasclart]

If it is similar to other cars. A knock level of 65 at Idle would be not good at all. But I dont think it would be as high as that and your engine still be running especially when on WOT

However scale might be different? The reading of 5-6 again if same sort of scale is fairly high but some are more sensitive than other. 5-6 could be phantom knock on one car and serious on another

 

[BenR]

carbon :S

 

[caister]

Ive got a max knock value of 94 and a max slow knock correction value of 5.25. Not both at the same time. The 94 occured about 4000rpm. I know what knock is but I dont really understand what the values mean, but i read the correction value should not go above 2.25.

 

[caister]

It runs smoothly and returns good mpg so im not too worried. But I was just supprised to see it that high.

 

[partyboy23]

question,dnt wana sound dumb but what is a high knock valve

 

[caister]

not a clue thats what im trying to establish!!!

 

[mattjk]

What fuel are you using? Try some higher octane fuel and hopefully the values will reduce.

Heres a pretty good Q&A for you to have a gander at cos its far more detailed than what I would be bothered to write!

http://wiki.answers.com/Q/What_does_a_knock_sensor_do

 

[caister]

shell v-power so ron98

 

[mattjk]

Sorry I thought youd be using peasent grade fuel (like the this cheapskate). Not a clue then!

Ps Shell V power is 99 lol

 

[caister]

^oh right never relised that. Is that too high to be using??

 

[mattjk]

Nope, its not the fuel thats causing it.

 

[ed1801]

Carbon build up is not too bad to sort though, either use a treatment thingy like: http://www.seafoamsales.com/motorTuneUpTechGas.htm or loads of throttle body cleaner down the intake (don't let the engine stall), this will clean out your plenum nicely too! Did this on my old Mx5 and it vastly improved idle performance - it was gunged to f**k though. Keep the revs high while you are spraying so that it doesn't stall - it will take ages to restart if you do stall it.

Or even tiny amounts of water down a vac line. The steam blasts the carbon away. If your going to do that, I would connect a narrow bore syringe needle to the vac line that you are going to suck the water up so that you can't suck in loads and lock your engine. You'll be able to get needles at the pharmacy I should imagine, just don't sleep so you have black circles under your eyes (and so look like a junkie) :dead:

 

[Jay Payne]

^ ive seen brake fluid used for that too. Down a vac line

 

[caister]

Hmm dont like the sound of using carb cleaner hasn't it got some nasties in it??

 

[ed1801]

Hmm dont like the sound of using carb cleaner hasn't it got some nasties in it??

Get the Wynn's throttle body and carb cleaner from halfrauds or similar. It comes in a spray can.

Yes, it does contain nasties. From the MSDS:

Ingredients
Chemical Entity: CAS Number: Proportion:
xylene [1330-20-7] 30-60%
acetone [67-64-1] 10-<30%
ethyl acetate [141-78-6] 10-<30%
butane [106-97-8] 10-<30%
propane [74-98-6] 10-<30%
detergent lubricant <10%​

None of them will hurt your aluminium engine though! It will sting like anything on your skin or eyes, so wear glasses and gloves.​

This stuff dissolves gunk literally straight off. Take off the throttle body to air filter pipe. Start the engine. Ph1: run engine up to 3k ish rpm by turning thingy that the accelerator cable connects to and spray pulses past the butterfly. Stop spraying when you hear it bog down and wait for it to pick back up. Do NOT let it stall or you will be trying to start it all day (although it will start eventually). Ph2: get someone in drivers seat to try and maintain 3k rpm whilst you do the spraying. ​

Easy peasy, safe, and really works.​

 

[mattjk]

Umm its probably not even due to carbon build up. If all you use is Vpower and the car is driving relatively hard I doubt it will be carbon I'd investigate other avenues.

 

[Fred@BTM]

too much info is a dangerous thing?

 

[Lagerlout]

too much info is a dangerous thing?

First thing I thought lol

Sometimes ignorance is bliss!

 

[caister]

im starting to think that!!!

 

[BenR]

Why blast all the dirt through your engine?

And I doubt its carbon, the layer or carbon in your chambers is a few thou thick and actually aids correct combustion.....its not inches thick with carbon that it'll affect anything. Excess carbon cannot build up, it just get burt or blown off in the combustion process.

 

[caister]

Why blast all the dirt through your engine?

And I doubt its carbon, the layer or carbon in your chambers is a few thou thick and actually aids correct combustion.....its not inches thick with carbon that it'll affect anything. Excess carbon cannot build up, it just get burt or blown off in the combustion process.

^^ hence the thread as im not 100% sure. Car runs fine produces good power and is pretty economical, do you think anything needs doing about it or is it what fred said and a little too much information is a bad thing?!