Knock and Ping Mystery

[rev210]

No it's not the title to a chinese who done it.

I have a strange little problem with a mystery 'knock'.

I can give it a full throttle take off from standing and 1st gear all the way to 7000rpm is without a rattle. Into second and third there is just a brief knock at 5000rpm each gear.

I was wondering if this is the sign of a dicky fuel pump or perhaps something else?

[PSIKO]

how far advanced is your timing rev210?

[skyzerr33]

fuel pump possible same symptons to what i had when my pump kicked the bucked.

[Jay95R33]

You probably know this, but remember that the higher the gear the more load is on the engine and therefore more likely to ping.

You might have to pull 1 or 2 degrees of timing off of her.

Or doesn't it happen in 4th and 5th??

I suppose to find out if it does ping in 4th or 5th you'd have to be doing mach 3 or something

[rob77]

Could be a dicky fuel pump or the stock pump cant keep up with what you've done. Or it could be all the advance, higher intake temps and higher boost catching up with the stock intercooler.

[NO_RSPECT]

doh the cooler argument had to come about, now take it easy REV

count to 10 deep breaths

but yeah I am agreeing with the timing story

[GTS-t VSPEC]

rev,

Is the knock light from the SAFC2 coming on? I'd get a dyno run done, then you can see if the fuel pump is causing it to lean out.

See'ya:burnout:

[rev210]

thanks for the ideas so far.

No it's not a timing issue, the knock is 'before' full power and timing can be pulled back 10 degrees and it will still occur at the same magnitude. Obviously I take off timing if I can 'hear' a ping at any time but, quite often this is just a very strong 'knock'

I had a feeling it might be a fuel supply issue.

[Jay95R33]

This might be a long shot - but it could be the harmonic's of the motor at those RPM/Load. Sort of extra 'noise' that the knock sensors think it's knock...

Any idea when your peak torque is?? Could be doing it on your peak torque too??

Strange stuff though - like said before, might be time for a test and tune on a dyno..

[rev210]

Jay95R33,

Nah, it's not harmonics. Your knock sensors don't pick that up.

I take the dyno tune advise on board, I've got to admit defeat unless someone has encountered this before.

Anyone got a spare gtr fuel pump?

[2rismo]

My vote is with the pump, but a VERY close 2nd place is the load variance in higher gears.

My fuel pump is A1 and it does this.

Adrian

[puckish]

Rev210 Check ya timing. I had some pinging and decided to check the timing on the weekend.

Try 40 degrees avanced !

[macka]

Originally posted by Jay95R33

You probably know this, but remember that the higher the gear the more load is on the engine and therefore more likely to ping.

You might have to pull 1 or 2 degrees of timing off of her.

Or doesn't it happen in 4th and 5th??

I suppose to find out if it does ping in 4th or 5th you'd have to be doing mach 3 or something

Yeah i agree whack some timing out to be sure...do your octane.....do it on a cold night...only one at a time and u should figure it out easy enough.

Dont forget rb25s are prone to pinging with their high comp ratio...

If the fuel pump was dying u would ping all the way and your engine would last 2 minutes.

ur saying its only faint? turn your stereo up

[bless_you]

rev,

I have the exact same problem, i only have an exhaust, filter and BOV.

I put on a atomic bleed valve to upped the boost to find that it got worse (obveously), then wound it down to find that it was still there. i have have plugs changed, platniums make no diff, and changed the gaps with no luck. my only options left are the Air flow meter (could be that) or the fuel system (like a coil pack or the like). waiting until i get motec before i look further into it. its just too much hassle looking for this thing blind.

Although run BP ultimate, this made it less.

Good luck and let me know what you find out.

[skyzerr33]

bless up

does the engine warning light flash ?

3 flashes is ping

2 flashes is AFM

[macka]

3 flashes is ping??

serious?

my light nes never flashed altho it can ping its nut off when it wants to

Bless you

timing? checked or not?

[bless_you]

never flashes.... i dont think that its a pinging however, it sounds more like a popping from the exhaust with a engine retard at the same time. the car exhaust rumbles off load and backfires between low speed up changes.

havent checked timing though. ive had it a slakos whoes done a full check on the thing and sees nothing wrong with what could be obveous, went to cred and they just changed to platnuims, worked fine until i got home... then you guessed it... back again.

[macka]

pinging will usually happen under full load, full throttle

if u back throttle off...its not ping....

maybe your too far retarded.(timing )

usually advancing to 15 deg and over makes the pop pop go away unless u have a straight thru with only one muffler so the engine doesnt have alot of backpressure

anyway.....

[bless_you]

thanks macka,

the sad thing is that i cant even get the thing up to full boost at the moment as the clutch is on the way out, it will slip shortly after 5krpm.

geting it replaced next week, and i will get the guys to have a look at the timing at the same time.

i do have a 90mm straight through exhaust to a tip muff. i also have a rx7 racing cat on the thing... it sounds blooody mean i tell you. would think that it would be a issue though...

[rev210]

I have run octane shmooster and it persists. Backed the timing off.

I've got some BCPR7ES plugs in now and still it persists (better power delivery up top tho' with a nice 1.0mm gap.

I'm thinking its a fuel thing, might have to try a big wack of extra fuel just before 5000rpm. The other thing it could be is cooling system (say it aint so!).