Lets Talk About Knock

[SargeRX8]

Well I had the car tuned not too long ago and the fueling issues have been creased out. When it was tuned, the max ping/knock on power FC we saw was about 19. 2 months later, today, I was driving home and gave it a little squirt. Got home and checked my hand controller and saw 60 knock. First time ever above 19. From 19 to 60 is a big change... When the car was tuned, it was tuned on the Caltex 98 Vortex fuel. Currently it has BP ultimate in it. Could this have any effect? Also it was tuned during the colder days of winter. The weather has been a little warmer.

I was reading that knock above 60 is somethign to worry about. For me knock above 20 - 30 makes me feel uncomfortable. This with the old tune for stock parts never knocked past 4. Is this something I should look into? Is it a one off? Could it be other engine noises which caused it to register?

If you've got a power FC, what knock do you get and what do you feel comfortable below?

I'm gonna stick with using Caltex fuel from now on in, see if that makes a difference. I'm taking the car up to jez soon to get it retuned for more boost so maybe if these temps are a little warmer the car will be adapted to this shit winter we are having.

[T.D]

Mate, that is EXACTLY the same problem I was having/still have lol

My knock level used to stay below 15 during "spirited" drives but then out of the blue, one day the highest knock reading I got was 128. Ever since then, the knock reading had been between 50-90 when giving it a boot so I took it in to the tuners and noticed my car will only not knock as bad if we retard the timing about 6-degrees from what it orignally was (which means less power )

I'm still trying to figure out what the problem is to have caused this to happen

I'm very interested to see what the solution is

Oh, and I run BP Ultimate

[R31Nismoid]

Anymore than 40 is a problem. 45 check engine light will flash.

If its only occured once, then its once-off.

Next time it does it note down RPM/gear/rough load. Could just be a cell or two that required slight adjustment.

[SargeRX8]

Mate, that is EXACTLY the same problem I was having/still have lol

My knock level used to stay below 15 during "spirited" drives but then out of the blue, one day the highest knock reading I got was 128. Ever since then, the knock reading had been between 50-90 when giving it a boot so I took it in to the tuners and noticed my car will only not knock as bad if we retard the timing about 6-degrees from what it orignally was (which means less power )

I'm still trying to figure out what the problem is to have caused this to happen

I'm very interested to see what the solution is

Oh, and I run BP Ultimate

We shall see what happens in my situation. I forgot to check the boost levels I hit to see if there was a spike or anything which could have caused a slight lean mixture. I will be trying to recreate the knock again. I drove first gear quietly into second then at low rpm kind of pushed it to about red line(hit the limiter lol) then cruised into third and gave it a little moosh and that was it. The road was dead flat but maybe the extra load on 2nd from the low rpm and the lag of the turbo had some effect? Not keen on trying it out again but I need to.

Anymore than 40 is a problem. 45 check engine light will flash.

If its only occured once, then its once-off.

Next time it does it note down RPM/gear/rough load. Could just be a cell or two that required slight adjustment.

Fairly sure its 60 as that is what my tuner has told me and that is what is written on paul r33's Power FC FAQ.

If the KNOCK wARNING is set to ON the engine light will flash when the knock level exceeds 60

The first thing I notice is the engine light flash, it did not flash that is why I had no idea it knocked. Only when I parked the car, I was like

I can pull timing on the whole tune if it starts to rear its head again but I am truly hoping its a one off.

[Rolls]

Could be faulty knock sensors or engine noise and not real knock, it could also be really bad real knock and the sensors are not picking it up. I would highly recommend getting a tuner with a set of knock ears to sit in the car with you, drive it around hard on boost and then sit idling for 10-15minutes to really get the under bonnet temps to soar and heatsoak into the radiator/intercooler, then rev out 3rd or 2nd up a hill and get the tuner to listen, if it going to knock it will knock then, if it doesn't you can be pretty certain it will be safe all the time.

The hotter the weather when you do this the better, I had my car tuned but a reputable tuner and I got some bad detonation after doing this on a 28c day, we took 2 degrees out around peak torque and it never happened again, car didn't feel any different to drive either.

Edited August 3, 2011 by Rolls

[T.D]

We shall see what happens in my situation. I forgot to check the boost levels I hit to see if there was a spike or anything which could have caused a slight lean mixture. I will be trying to recreate the knock again. I drove first gear quietly into second then at low rpm kind of pushed it to about red line(hit the limiter lol) then cruised into third and gave it a little moosh and that was it. The road was dead flat but maybe the extra load on 2nd from the low rpm and the lag of the turbo had some effect? Not keen on trying it out again but I need to.

Best bet is to get it to the tuners so they can verify it's real knock cos you do get "phantom" knock sometimes. I got mine verified by a tuner and some headphones and yeah, FML.

[89CAL]

Just FYI I used to get alot of random knock. Changed to a carbon fibre timing cover not long ago and my knock decreased

So think I have faulty sensors. Especially seen as I can get 20ish knock on startup and got 61 knock over a second after I had backed off the throttle another time

Modifying a car can throw them out too apparently

And can confirm default setting for knock warning is 60. Tuner can change this but

[DVS JEZ]

Correct. Knock warning is factory 60. I normally set mine to 50.

89cal it might be that when u set ur cas back into place the base timing is now a little lower.

Sarge i have seen knock spike during gearchanges. So keep and eye on it. We will do some logging on the road when u come up and watch for when and if it spikes. Ill put my kmon on and have a listen too

[Rolls]

Why would timing cover make any difference?

[JonnoHR31]

if it only ever happens when you hit limiter then its almost certainly a false reading. to be sure you could pull a bunch of timing out of the cell after limiter to make sure its not pinging.

[paulr33]

the powerfc faq has 2 topics on knocking

Tuning Information

# I always have knocking, is it true, is it lies or is something wrong?

http://paulr33.com/powerfc-faq/powerfc-faq.htm#66

# How do I debug knocking, how can I make it go away?

http://paulr33.com/powerfc-faq/powerfc-faq.htm#67

The most likely scenario is when the car is tuned on the dyno it uses a certain set of axis and the tuner mainly focuses on these.

The environment is usually controlled and the tune state is fairly static given the conditions and environment.

Then you get the car and flog the absolute crap out of it and touch cells that might not have been tuned as well, or have as much variance to account for different conditions.

End result is it knocks so you might need to do a map tracer, find the cells you hit, and tune them a touch, takes 5 minutes and the FAQ tells you how to do it and costs you $0.

This is a key advtange with the powerfc

you have the faq

the power fc flashing the knock warning light

a simple hand controller interface to fix the issue

lots of people willing to help

most cases should cost you $0 and doesnt need a "retune"

[Don Dada]

Most of the time tuners focus on full throttle runs in a particular gear when tuning so there are lots of load pts that are not touched when on the dyno.

The dyno is also different in terms of what load cell it would use compared to driving on the road under the same conditions....for instance i had a couple cells on part throttle that would knock only in fifth gear on the road, and purposely left it like that to go on the dyno and tune it out but when i was on the dyno trying to replicate it, i couldnt get it to knk for nuttin.

So best bet is get someone with knk ears and hit the road as it seems that your prob is on part throttle as what you described

[DVS JEZ]

Why would timing cover make any difference?

You hav to remove the cas to change the timing cover.

So when u refit the cas it may be different.

if he didnt check and note the base timing before removing the cas then how can he be 100% sure its the same

[Rolls]

You hav to remove the cas to change the timing cover.

So when u refit the cas it may be different.

if he didnt check and note the base timing before removing the cas then how can he be 100% sure its the same

Almost certainly retarded the base timing slightly then.

[SargeRX8]

^ Very true. Changing the cover wont fix it, but one dial back will pull the timing back to a point it almost will never ping(if the tune is already safe and had rare det, it should be "safer").

I can understand the car is now out of original spec so there could be numerous things triggering the sensor. I hope it is a one off, so I'm gonna take it easy on the car until the retune with Jez. There are alot of clunks and clanks which could trigger the warning, but turning a blind eye to it, especially if it happens again, is a stupid move. Better safe than sorry.

Does anyone know what the voltage range of the knock sensor is for the R33 Series 2 RB25 motor? I want to build a knock gauge and have it calibrated for the voltage range of the knock sensor.

I don't believe there would be a max voltage(well there would be but technically there is no limit to how hard an engine can knock, is there?) so I assume it would start from 0v. Depending on how it increments ill calculate something to give a out of 100% figure. I think that is why Apexi just display a number. Numbers are infinite so its just the higher the worse, there is no real red line. Its 12am and I'm tired.

Edited August 3, 2011 by SargeRX8

[89CAL]

My timing cover was vibrating a bit when I had the stock one on. Was sometimes really obvious at idle.

I just think I eliminated a strange noise that was giving false readings. Given I think my sensors are faulty anyway it might have been causing some fake knock. But I may have bumped it back slightly on base timing and am getting a placebo effect from this lol.

[Rolls]

Sarge it isnt a voltage it is an analog signal and you have to filter the knock frequency from the mech noise with a band pass filter, not exactly trivial unless you know electronics theory and opamps + building filters, you would then need to determine a threshold via inducing real knock, better to buy an existing setup, there is a reason why good knock ears

Cost 2k

[sucram]

Couple of things tha havent been mentioned.

Fuel pumps dont last forever but it could be a dying fuel pump

Engine breathng heavy. It could be flinging more oil into the PCV or intake

Weather is a big factor. The power fc doesnt have a great intake temp compensation, the oem sensor in the rb26 is coated so its slow to respond anyways.

If you get your car tuned in winter, there is a good chance it will knock in summer as you cant heat soak and engine or replicate 40deg c temps easily. However

it is possible to take an educated guess at it. Its a compromise but beats a retune for summer or winter whch isnt really feasible.

Fuel is an interesting one too. When vortex first came out, it was more oxygenated then BP/Shell/mobile however I found that you could run a bit more

timing on shell for example but it would run richer. It seems they have changed their fuel as now it is very similar to what shell used to be. Its not likely

that a tuner will tune so close to the edge that it will det on change of fuels, but if you have a combination of things going on it will contribute. Say your

pump is getting tired, engine is breating a bit more, hotter weather then when it was tuned, going through cells not ususally seen on the dyno

Biggest one, air temp compensation, the power fc's isnt great but it can be effective enough

[Harey]

Some good points made there sucram, however it sounds like it is intermittent and doesnt happen everytime on the one tank of fuel or temperature etc. To me the experience described by Sarge would be more likely that some of the tuning cells are not set correctly and it is only when it hits these cells that knock is experienced.

Sarge you seem to have glossed over PaulR33's update?? That is the first place I would be investigating.

[r33cruiser]

What condition are your plugs in?

Have you actually pulled them out and checked them yet?