Jump to content
SAU Community

Knock On Back Off/coasting - Pfc

Kwyjibo

By Kwyjibo,
in Engines & Forced Induction

 Share

Recommended Posts

Kwyjibo Rising Star

Kwyjibo

Posted
Posted (edited)

Hey,

Have checked Paul's FAQ page and done a search but can't find anything on this.

I know the knock sensors are fairly dodgy but I'm noticing that I get spikes of up to '40' knock when I come off throttle on my PFC. I also get knock of around 20-30 when coasting with absolutely no throttle. As soon as I open the throttle this drops to below 15 right through the rev range.

Just wondering if this is normal? I have heard knocking at low revs/load isn't *as bad as at higher loads but I would have thought getting knock anywhere still means premature ignition and damage to pistons.

If this is the case where would I look at reducing timing? Just wherever the map tracer is sitting when coasting?

Cheers,

Adrian

Edited by Kwyjibo
Link to comment
https://www.sau.com.au/forums/topic/284700-knock-on-back-offcoasting-pfc/
Share on other sites
skylinecouple Experienced

skylinecouple

Posted
Posted

Hey, would like to jump in here. How much have you added to your numbers ? I am at 46 in the LO1 and 2 at No7 throttle area and not getting more than 3-4 knock. How hi can this keep going before it knocks at say ten and like you said, every engine is different. Have posted in Paul's PFC thread but I guess there aren't too many people tuning their own cars.

Kwyjibo Rising Star

Kwyjibo

Posted
  • Author
Posted (edited)

Haven't actually adjusted it from standard yet. Pretty much just finished all my mods and I'm about to organise my tune. It defintely feels as if the timing is much more retarded than my original ECU as it is a lot less snappy. I did try doing the temp ignition correction for one small drive(+2 and then +4) and it brought it back to how it felt previously and knock levels stayed exactly the same. Of course don't know how this would affect medium to high load situations as I didn't want to risk it.

I think I'll just talk to my tuner to make sure its safe.

Edited by Kwyjibo
Kwyjibo Rising Star

Kwyjibo

Posted
  • Author
Posted (edited)

Nope. Just took it around the block a couple of times to make sure it was running ok after putting some stuff back together. I want to make sure everything is sorted and working properly before I spend money on a tune. Basically I just checked that its running safe AFR's for the drive to the tuner but then noticed this funny situation.

My impressions from the Power FC faq is that the standard maps are pretty similar to the standard ECU.

But seriously can someone tell me if I should be worrying that knock jumps up under absolutely no load but is fine off load? I would have thought premature ignition is bad at all times but I'm not very mechanically minded and the FAQ indicates otherwise.

Edited by Kwyjibo
JonnoHR31 Grand Master

JonnoHR31

Posted
Posted

it can be bad but no where near as bad as under full load. 20-30 under light load before a tune is nothing to worry about. myne was pinging its tits off on the base pfc map, just use the temporary adjustment until you get it tuned properly

~Nvied~ Rookie

~Nvied~

Posted
Posted

I reckon those knocks are fine. Anything over 60 should be concerning. I run a pfc as well and i get no knock at all through low rpm and i get knock of about 6-7 at 2500 to 2800 rpm for some odd reason. I also get some knocks off like crazy 100 or higher the odd few times hardly ever though.

Any my engine is still running like knew so i reckon after a tune ... you'll be all sweet. I wouldn't recommend driving it before tuning it properly though incase there is too much difference which may end up causing damage to your engine.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
Nope. Just took it around the block a couple of times to make sure it was running ok after putting some stuff back together. I want to make sure everything is sorted and working properly before I spend money on a tune. Basically I just checked that its running safe AFR's for the drive to the tuner but then noticed this funny situation.

My impressions from the Power FC faq is that the standard maps are pretty similar to the standard ECU.

But seriously can someone tell me if I should be worrying that knock jumps up under absolutely no load but is fine off load? I would have thought premature ignition is bad at all times but I'm not very mechanically minded and the FAQ indicates otherwise.

You have not tuned it - and you are asking about possibly wayward knock numbers...

Been a while since i've heard something like that.

Every car is different. Go and get a TUNE. Driving around on the stock map proves/achieves nothing.

The FAQ assumes you actually have gone and had the car tuned, it does not assume you are driving around on the stock map.

Kwyjibo Rising Star

Kwyjibo

Posted
  • Author
Posted

Sorry I guess my original question should have been 'do you think this will be safe to drive to the tuners'. I am wondering if it is usual for knock to go up when letting off the throttle. I know the numbers are going to be screwy before getting a tune but if I drive its 10km and I don't want to destroy my engine in the process.

PsYLoR Collaborator

PsYLoR

Posted
Posted

Yes it will be safe to drive it 10km to the tuner? - you should re read the Power FC FAQ again, then read it once more after you've read it twice already.

If your still worried, when you drive it there go to SETTINGS,,,, IGN/ INJ

Change the Ign Timing down -10 so the whole map is down 10 degrees everywhere - wont see much knock then.

Kwyjibo Rising Star

Kwyjibo

Posted
  • Author
Posted (edited)

Relax, no need to be like that. Above I posted I dropped it 2, and then 4 degrees retarded and exactly the same thing keeps happening, no change in knock. I'll just drive it there.

Still am interested to know if anybody has any theories as to what could cause this spike to happen in an engine when you back off, lets say after it HAS been tuned.

Sorry for the newbie questions but I am a Software developer, not a mechanic and I'm building this car up as a hobby so I have much to learn and the best way is too read and ask questions.

Edited by Kwyjibo
PsYLoR Collaborator

PsYLoR

Posted
Posted

It could be related to any number of things, it helps to be more specific with what you have done to the car if you want some help, but at the end of the day its all going to be speculation until you take it to be tuned professionally.

Seriously now.... It could be as simple as something taping from the change in inertia and making the knock sensor give a reading.

skylinecouple Experienced

skylinecouple

Posted
Posted

Once you have it tuned with the correct AFR's then you can go ahead and tune the timing for a best result. There is no way the tuner is going to put in hours of work to tune the ignition from idle to redline, he'll just make it safe from boost transition to the red.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • sunsetR33
      Unpeeling the Orange

      By sunsetR33 · Posted

      Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • Kapr
      What brakes on R34 GTT(Europe)

      By Kapr · Posted

      No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • wizlb
      Who has a Infiniti Q60, Q50 (V37)?

      By wizlb · Posted

      I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
    • Kinkstaah
      Starting again

      By Kinkstaah · Posted

      Yea - I mean I've seen my fuel pump which is decades old and uh, while I'm not saying this with real knowledge... but I sure get the ick at using anything in the fuel system that produced the state of that pump. Many years ago I went through multiple pumps (and strainers) before I dropped the tank to clean it out with extreme violence. I'm talking the car would do maybe 50km before coming to a halt, which resulted in me cleaning out the filter with some brake cleaner and going on my way. None of my stuff ever looked like what came out of your fuel tank. I don't think I'd be happy with it unless every single component was replaced (or at least checked/cleaned/confirmed to be clean here).
    • GTSBoy
      What brakes on R34 GTT(Europe)

      By GTSBoy · Posted

      I'm not going to recommend an EBC pad. I don't like them. Just about anything else would suit me better. I've been using Intima pads for a while now.
×
×
  • Create New...