Rb25Det - Knocking

[Aleckr33]

Hey everyone,

Im reading knock levels of 90 - 105 on my Power FC... Only on full throttle i see these high readings (2 occasions, 98 first time, 105 second time with engine light flashing both times) Injector duty at 85 - 90% MAX.

Car is a Skyline R33 GTST. with the following mods

Unopened RB25DET

Power FC

Z32 afm

ATR43G3 .82 IW turbo

Nismo 555cc injectors

Unknown Front mount.. decent size though..

Tomei fuel pump

The car is tuned at 256rwkw with a slipping clutch, left the workshop with a slipping clutch because i couldn't afford a new clutch at the time, changed the clutch at another workshop about a month later... the car didn't feel right..

I found an intake leak underneath my stock plenum not long after i changed clutch... Gasket was shot, changed that. Now im very happy with the car! much smoother and pulls much harder throughout the rev range.

Now my question is, now that iv fixed both these problems, is it possible my car is making more power than 256rwkw? and would that explain the high knock levels? Should i take it back to tuner?

Cheers.

[WYTSKY]

Well by the sounds of it, it is tuned for that power but you had a slipping clutch at the time, so there was no or less load on the motor when it slipped. Now you have fixed that, the car can rev right out and there is probably a couple of higher rpm and load cells that need to be fixed.

A rule you can go by is anything above 60 in higher rpms is bad and you shouldn't leave the tuners with a car that has a bad knock. obviously its not urgent if it is only on WOT, because you can drive normally with it, just dont put your foot to the floor until you get it back there.

[NSNPWR]

Try dropping the boost or pulling a few degrees of timing from the map and see what happens...every chance that now its got a decent clutch in it that the motors under more load, making more power and running lean?

[Aleckr33]

Ok then, Thanks. I will book it in ASAP. And i left the workshop not knowing that the car was knocking, because i had a slipping clutch i obviously didn't give the car a hard time. And even after i changed it, knock levels were nice and low.. But now since iv changed the Plenum gasket the car does feel a lot better but with high knock readings.

[JonnoHR31]

you removed a boost leak, it'll now be running richer under vacuum and leaner under load, along with the extra load from a working clutch it'll be out of tune. take it back for a touch up and take it easy until you do so

[Room42]

If it was tuned with a leak then it would probably be running more boost now. If you know how pull some timing off the map temporarily until it doesn't knock then adjust the ign map accordingly. ONLY IF YOU KNOW HOW!!! The fuel map may need a minor touch up as well. Unless you are very good at tuning take it back to your tuner and get it fixed. Tell him/her you fixed the leak and they should be able to sort it for you quick as. Don't flog your car with that much knock. Its not good for it. Make sure you run 98 premium fuel ALWAYS. I only see 20 knock with united98 and 45 with bp98....lastly I gotta say again don't touch it unless you know what your doing. You may end up cracking or bending something. Read http://www.paulr33.c...powerfc-faq.htm

[Pattygtst]

I would be checking with a tuner if there is any audible knock. I think knock readings are bullshit. Mine reads that high all the time but it's not actually pinging. I don;t pay attention to the readings anymore. I assume its the knock sensors.

Do you get inconsistent readings whilst driving the car hard?

[DVS JEZ]

Should never assume.

Get it checked.

A good way is to trim 5 degrees out and see if the level drops

[tridentt150v]

I drove around with knock levels at +100 for aprox 12 months. And it was real knock. I just monitored it, took it easy, and didn't do anything silly. So no panic, but do get it seen to as soon as you can. i didn't do it sooner because i was installing my WMI and few other things, so I let it wait. I actually drove to the GC and back approx. 3,000km while it was like this.

My problem and solution was totally different to yours though [my knock couldn't be tuned out, and I luuuuuuuvvvvvvv WMI].

WMI actually increased my fuel economy, gave me an extra 30kw, and I lost my oil consumption due to overfuelling [tuned in/used to compensate for the knock, a dirty solution that only partially worked]. So now I go further, go harder, and don't use any oil

[JonnoHR31]

the damage varies. my old 25 copped 100s and 100s of knock readings well over 100 (some over 200) and never had any problems whatsoever, and yes it was genuine knock. pulled the head off and the pistons have slight detonation damage but nothing severe. on the other hand my 25/30 with a slightly bigger turbo setup (better manifold and bigger a/r housing) pinged hard once and 2 big ends and 1 main bearing ate the crank.

better to be on the safe side and get it checked, in the meantime keep it off full load.

[Room42]

Example: I run 17 degrees timing at full load at 14 psi on a stock turbo. Makes about 20 knock or less. 18 degrees makes about 35-40 knock and 19 makes over 60. The other week I completely unscrewed my boost bleed valve hose and saw about 22 psi that tailed off. The knock went up to 135. I took off 4 degrees timing and the knock was back to 35. 0 to 100kph burnouts were had by all...Actually only me and only 2 of them. Then I turned the boost down before the turbo shit itself. Some useless/useful info there.