Apexi Pfc Knock Readings!

[ScarifieR32]

Hey

I just got my car back from X Speed

they are reknown tuners for powerfc and ant scali knows his stuff

The car over all runs pretty good and the knock levels are ALWAYS below 20

Except once last night i got cut off by a car and went past him on gate in 4th gear

it rev'd out to 5600rpm and read a knock of 126?

i was concerned and cleared the hold settings , put it in 3rd and reved it out to 6000rpm and it didnt go above 14 (did the same 4-5 times more that night still the same)

Am i worrying for nothing? because basically its cost me a small fortune to upgrade to the 25 after blowing 2 rb20's in my 32 and i really dont want to blow another engine

its tuned very safe - no timing at 14psi with 11.8 afr and lower with a max power of 312hp

Also is it possible for a rock or something making a noise in the engine bay to cause a knock reading?

Im new to the pfc so any information will be appreciated!

[R31Nismoid]

Take the car back to the tuner.

126 is not acceptable.

20-30 is, no more.

cheers

[ScarifieR32]

even if it was a once off?

it was a VERY cold night aswell

[paulr33]

have a read of the pfc faq in my signature

covers everything you need to know on knocking and how to debug it

it could be a big problem, it might not be, have a read and you shall learn

[sweetr33]

yeah that would scare the pants off me if mine knocked to that, highest ive seen on mine was 50 and thats because a certain someone got abit throttle happy before it was tuned <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

[ScarifieR32]

HAHA NOW YOUR ALL WORRYING ME!

should i just keep an eye on it and if it happens again then get it sorted

or would you advise not to give it shit at all and contact x speed?

i have been reading the pfc faq but i dont want to play with any settings yet

so basically that knock reading wouldnt of have done any damage?

[N I B]

Did you hit the rev limiter as ive seen high counts on the limiter.

Get Ant to put the Datalogit in your car and drive it on the street and see where the count is as it could be timing wrong/Fuel at one point or just a random noise and try hitting the limiter.The PFC count is a guide but not 100%.

I have seen higher counts on the road than the Dyno.

[paulr33]

it is as nib said, a guide

the higher the level, the higher the knocking or detonation

it wont be related to speed but load

more often that not, in most cases;

car is tuned

runs prefect on dyno

jack all knock

car is taken on street

user loads it up

see's knocking

what generall occurs is you load it up on the street and you touch some areas of the map that weren't

tuned or have a bit too much timing. the dnyo is a simluator so it does a pretty good job

but its pretty common to see a car knock a bit differently on the street

if it was me and its my work shop i would tune the cars

then tell the owner to take it for trash and come back with the top score knock figures

then re-adjust based on that, ive seen so many tunes get done, then knock on the street after it

its no ones fault if that make sense, its just load variations and how much you give it curry on the street

not a big problem - easily fixed and sorted

[fEkuaR]

so how fast were you going at 5600rpm in 4th gear?

[paulr33]

193.45km/h

[fEkuaR]

193.45km/h

sounds like its a pitty his engine didnt pack it in ... might want to slow down a bit on the public roads eh?

[LTHLRB]

iv seen it happen a bit to mine, got tuned on dyno, the tuner hooked his laptop up i took it for a hammer on the limiter something savage and very hard driving.. come back and 20 - 25 MAX.. at time i get some crap air or anything and knock may go to 60 for a split second.. had it checked over and is perfect.. the tune is perfect.. Also on my brothers 180 it went over 50 and it had a manifold gasket leak.. checked it over on the tune, was perfect, changed gasket.. highest hit was 20..

It could be noises, leaks, rattles that the knock sensor may pick up.

[BAMR33]

Is it over boosting or anything? Besides that could be as mentioned earlier a blown gasket.

[ScarifieR32]

what i thought was a dodgy dump gasket ended out being the 6th cyl mani gasket leaking BAD

i think this may have something to do with it

it only happened once and other than that its NEVER gone into the 20's

the tune was a very very safe tune and had timing taken out of it up top

i havent hit the limiter yet and dont intend to anytime soon

it was night time and cold and i dont have a boost controller on it yet but the dyno reported very smooth boost levels and because of the timing taken out up top it drops the boost down a bit

ive got a blitz ebc on order and when it comes im goin back to x speed for a retune

and fekuar , when a person pulls infront of u when your doin 110 they deserve to be gated

once they copped some of that then i went back to the speed limit

[sweetr33]

bouncing off the limiter shouldnt effect knock reading to much, mates 400hp 180 drifting on track never see's a knock reading higher than 35 and he bounces off limiter endless times.. a mate of mine used to record a knock reading of 95 when he started his car up on pfc h/c but once cleared and driving never went abover 30 knock, yet 95 on startup... bizzare

[ScarifieR32]

fEkuaR 1 other thing......

my speedo said i was going 0kph so i wasnt speeding

or is that because i dont have the speedo drive installed yet?

[Leadfoot]

As NIB says I recommend you take it back and get some timing taken out of it.

Probably best to note what rpm and conditions occured at the time of knock so they know where to take out the timing.

Its funny you should have the same problem as me.

Got mine tuned at X-speed the first time about a month ago and I have now have the exact same problem.

I have recorded knock as high as 90 although it has spiked up to 70 probably about three times.

20 to 30 is the max I ever use to see on the old tune so it will definately be getting a retune.

I am completely refraining from boosting anything over 0.9 bar at the moment.

I will be taking the car back to have this sorted shortly. My guess is that the standard timing map used by Xspeed is probably a good compromise for general street driving and also gives a good result on the dyno. Usually what most customers want.

A knock of 150 is regarded by the factory Nissan ECU is true detonation so a knock of 120 will need a retune.

I get high knock during heavy acceleration when combined with wheel spin.

Alternatively a high boost setting of 1.2 bar and around 5500 rpm will do it (knock of 50 or so). Was reluctant to repeat to prove conclusively.

Just holding the throttle pinned in second gear and hitting the limiter was not enough to induce any knock over 20.

Because I race at the AHG driving center the engine is encountering these types of conditions for a duration of 1 minute over the short-tight track layout.

I have a Blitz IBC and I have tried all sorts of EBC settings such as gain and manual control which has not on its own (short of reducing boost to 0.9 bar) stopped the occurance of occasional high knock.

I definately wont be competing again until I have had a retune. I am quite happy to sacrifice some top end power however to improve engine longevity if that is what is required. Unfortunately the ignition map has been hidden or I would post up some timing values for comparison.

Basically I think road and track conditions are a lot more arduous than the steady ramping of a dyno roller and hence introduce dynamic transient conditions such a rapid acceleration or throttling on and off at maximum horsepower. The airflow meter probably doesnt react quick enough under these situations.

I dont see this as Xspeeds fault as I did not advise them the car would be used for these types of activities.

They also indicated (when picking up the car) that they would have tuned the car differently if I wanted a tune for "response" as compared to "horsepower". I guess I originally thought the standard map would suit both spirited and casual driving styles alike however may have been an oversight on my behalf.

Advising the tuner of the required vehicle use may have avoided the need for a retune in my case.

However, no harm seems to be done, and a lesson was learnt.

Would be interested to here how you go and whether you get it sorted as this has caused me some concern also.

[ScarifieR32]

yeah i got them to tune it as a safe safe tune and hence they took timing out up top and left everything else standard on the timing side of things

ant said if it had timing put into it aswell as ultimate fuel (tuned on vortex) it would make 350 easily on 1 bar

im not after max power

all i want is reliability with a bit of poke

so far im very happy with everything , im just cautious because of the money and stress the car has caused me

the main reason i chose a pfc is because of the knock sensor reading and when i seen a high reading i worry

i just want to enjoy it and drive it from now on without the stress!

[SimonR32]

Take the car back to the tuner.

126 is not acceptable.

20-30 is, no more.

cheers

do you have any idea what engine noise is?!?

[The Mafia]

It could have been:

Engine noise

Could have hit a really cold patch of air

Something might have rattled

a backfire

Rev Limiter

Bad Fuel

anything

Even if your tune seems "safe" you'll still see a bit of random knock here and there. You can never stop it. There are too many variables. Just make sure that it doesn't happen constantly.