Retaining Knock Sensor With Pfc

[GTR32]

Guys;

Does anyone know if this is possible? It makes me a bit nervous that the PFC won't retard ign via the factory knock sensor, seems the best way to protect the engine so not sure why they don't have this feature. Don't hear of many stock engines detting themselves to death. I know that the dash light flashes when there is det but I'd rather the ECU do it's thing instantaneously. I understand the D-jetro does this so they must have the tech to do it.

Cheers

[omg]

Within the power fc itself it won't do it however from what I've seen you might just see some cheap acessories for the power fc which will do this (among other things) hitting the market in the near future

[Sydneykid]

I get asked this a lot, my usual response is, what is it that you want to protect the engine from?

For example, if it is excessive boost causing the knock (eg; stuck wastegate or dud boost controller), then you protect the engine via the boost correction table. When the boost exceeds your programmed levels, throw some fuel in there.

If it is excessive water temperature (eg; hot day, busted radiator hose), then you protect the engine via the temp correction table. When the temp exceeds your programmed levels, retard the ignition.

If it is excessive air temperature (eg; hot day, busted intercooler), then you protect the engine via the temp correction table. When the temp exceeds your programmed levels, retard the ignition. If you have a Datalogit and a PFC Boost Control Kit you can also reduce the boost levels in three steps of inlet temps. Even go zero boost if you want.

There are other correction tables for battery voltage (dud alternator), ignition dwell (dud ignitor) that also retard the timing. You can also adjust the dash light flash for injector warning, knock warning and air flow warning.

That's a hell of a lot of programable protection without resorting to the simplistic limp home style that you find in standard ECU's. Plus it makes finding the problem (the one causing the excessive knock) a whole heap easier.

Hope that helps:cheers:

[Scooby]

Thanks SK;

1. Trying to protect it from detonation....I like the factory system because it's a failsafe, no risk. And that means not incurring RB26 DEBT.

2. While you can prog for some eventualities you can't prog for all. How about bad fuel or a combination of some events you have described, not just the event eg air temp, or water temp in isolation. A combination of big enough (but below programmed threshholds) events might bring about the right circumstances for detonation. Dud injector maybe?Unlikely perhaps but I'm not gambling with a 12k rebuild.

3. I have to rely on someone else to tune it for me. And, as you know, it's all in the tuning. I don't have the expertise to know what to tell the tuner re thresholds, and I have no way of knowing if what they have done is going to protect the engine.

4. I'd rather spend $ and time finding the problem that $$$$ and time rebuilding an engine ie see point 1.

I once put the question of knock detector absence to a well respected tuner in Sydney. His response was 'just don't go mad on a hot day'. Please! I'm not going to risk my engine on that basis. I want something that will allow me to flatten the thing under any circumstances irrespective of weather. That may not make him well respected in your eyes but then I doubt he has your experience, unfortunately he's about the best most of us can get access to and I suspect he's conservative.

And I still don't know why it's not a standard feature.

Regards

Hi omg;

that would be v interesting. I look forward to seeing something about it.

[Sydneykid]

Thanks SK;

1. Trying to protect it from detonation....I like the factory system because it's a failsafe, no risk. And that means not incurring RB26 DEBT.  

2. While you can prog for some eventualities you can't prog for all. How about bad fuel or a combination of some events you have described, not just the event eg air temp, or water temp in isolation.  A combination of big enough (but below programmed threshholds) events might bring about the right circumstances for detonation. Dud injector maybe?Unlikely perhaps but I'm not gambling with a 12k rebuild.  

3. I have to rely on someone else to tune it for me. And, as you know, it's all in the tuning. I don't have the expertise to know what to tell the tuner re thresholds, and I have no way of knowing if what they have done is going to protect the engine.  

4. I'd rather spend $ and time finding the problem that $$$$ and time rebuilding an engine ie see point 1.    

I once put the question of knock detector absence to a well respected tuner in Sydney. His response was 'just don't go mad on a hot day'. Please! I'm not going to risk my engine on that basis. I want something that will allow me to flatten the thing under any circumstances irrespective of weather. That may not make him well respected in your eyes but then I doubt he has your experience, unfortunately he's about the best most of us can get access to and I suspect  he's conservative.  

And I still don't know why it's not a standard feature.  

Regards.

The reason why it is not standard is Apexi don't think it needs it. They believe (and I agree) that there are enough maps/correction tables to cover the circumstances, let me try and look at your examples;

Water temp, I have my water temp correction starting at 5 degrees above normal running. Anything less than that would have no effect on knock levels, so you gain no extra protection from having knock retard.

Air temp, the inlet air temp correction table has multiple points, so you can start protection at any temp you like, as little as 2 degrees if you want. That is way less than would have any effect on knock, so you gain no extra protection from knock retard.

Even if I add the two together (say 4 degrees water temp and 2 degree inlet temp) the knock would not increase enough to trip the knock protection. Plus it is worth mentioning that the standard ECU will only retard the ignition, the PFC will add fuel AND retard the ignition. So I could easily argue I have SUPERIOR protection for my engine.

Knock retard won't do much for you with a single dud injector, there are plenty of standard ECU RB20/25/26's around with holes in pistons and the knock protection didn't help them. Fuel bad enough to trip the standard ECU knock protection is so bloody obvious from the driver seat, you would stop driving long before the standard ecu did anything. Plus the dash warning light is going to warn you and you can see what is going on via the Commander.

As for tuning, well you are always in the hands of your tuner. If he stuffs up or tunes it too hard (zero safety margin) then knock protection isn't going to save you. I srongly suggest you establish a relationship with your tuner and discuss what it is that you expect/want from your engine. None of what I have posted here should be foreign to any decent engine tuner. If you talk to your tuner and he doesn't display sufficient knowledge and/or understanding in response to your questions, then I respectfully suggest you find another tuner. I think I have given you enough ammunition to ask sensible question and audition your tuner, if not please feel free to send me a PM and ask any question you want. I will do my best to answer them.

The bottom line is, there are plenty of people around who will confirm that the standard ecu (with knock protection) is not going to help you in most circumstances on a highly tuned/worked engine. It works OK on a stock standard one. But Apexi have designed a better system for your purposes, because it is designed for modified/tuned engines.

I can assure that I feel far safer driving my RB31DET with a Power FC looking after it, than the RB25DET with a standard ECU.

My 20 cents worth:cheers: