Was feeling paranoid about engine detting after various mods, so thought a Knocklink sensor and led indicator would put my mind (whats left of it) at rest. But then I thought (on a different day) why bother - if it dets, the ecu will automatically retard timing to stop it (won't it ?).
Any reason to buy one other than something to watch when driving ? (in between answering the phone and messing with ICE )
Serious answers please - OK - ANY answers
Stan

[This message has been edited by StanS (edited 12 June 2001).]

 

Stan,

A Knocklink is good after mods, because the standard ecu may not retard enough, which can happen if running a substantial amount of boost or from bad fuel or incorrect fuel mixes plus excessive temperatures. The Knocklink, which lets you see if the engine is detting, allows you to back off and drive the car easy, till you go and fix the problem .

I'm not the best on here when it comes to explaining but like to have a go if I think I can help. The 'guru's' usually come to the rescue after I post with even better info,correcting me or giving a more in depth explanation. The above is just a basic outline of why I think a Knocklink is needed.

Regards,
WREXY.

P.S. I have a Knocklink on it's way for my car.

[This message has been edited by WREXY (edited 12 June 2001).]

 

because it looks good. and makes my car look like kit out of knightrider.

 

Cheers Wrexy
I naively thought the ecu would retard until det stopped.
I assume that with higher boost (eg 19psi on a cold day with a PPP) the ign needs retarding more anyway due to the higher pressure mixture igniting more readily ie before it should, but assumed the ecu would sort it out. Also that if pressure was increased to say 20/21 psi same would apply.
Maybe there are programmed limits to how far it will retard ign (not expecting say 20/21psi). Wouldn't octane booster counter this ? So a knock link would just give a visual peace of mind that the problem was being solved by the ecu ??
It would be nice to have an unbiased definitive answer from one of the true experts (trained/qualified) who read these threads and no doubt sigh with dispair ! PLEASE
Stan

 

Knocklink is only for visibility. The standard ecu may retard enough for 19psi but may not. You don't know. That's why the Knocklink is good to have, To be able to catch a bad situation before damage. Maybe your stock knocksensor (as an example) would have stuffed up and there would be no retarding at all. At least with the Knocklink you will see it and take action. Programs are available for correct fuel and ignition curves to suit higher boost such as a Link ECU or Motec or the Unichip. But as a safety measure the Knocklink rules. Feel free to add to this, guru's

WREXY.

[This message has been edited by WREXY (edited 12 June 2001).]

[This message has been edited by WREXY (edited 12 June 2001).]

 

Stan
The ECU map has fixed parameters. It will only retard so far, to whatever the degree of maximum retard that particular map is set at and that's it. If it isn't as much as the physical needs of the engine in those particular circumstances that is where a problem may occur.

A custom mapped ECU for the particular engine and its requirements is the safest option.

 

Even with a custom mapped ECU a Knocklink is essential.Other things may change in the car/fuel/enviroment that could cause it to det despite a expertly mapped ECU.

 

There are no experts to my knowledge tat post on here, but I would trust Bob Rawle and R19KET over all others.

I dont know what the safety parameters of the standard JECS ecu are (pat??) but if the standard knocksensor was faulty, I assume, the ecu would automatically retard. If it didn't then the knocklink would allow you to stop the knocking from occuring by calming down on the loud pedal.

To my knowledge, after tuning, the amount of knock can give you soem indication as to whether or not you have improved things, eg. charge cooling will reduce knock, so fitting water spray should show you less knocks (not much good if you didnt get any before hand).

When mapping an aftermarket ecu, you will often have to access a different menu to check on knock (you do with the link) so this allows yuo to see what you can get away with in real time.

Plus, I dont believe some ecus (motec??? - someone please correct m,e if I am wrong here) has an automatic retardation on detection of knock feature. I know the link does, but I think it is removed higher up the price ranges So if you have a dodgy batch of fuel with lower RON than quoted, if you couldnt see the det and your extensively modified ecu cant correct for it, then your engine will go bang without warning.


The most important reason for buying one is as sam says, the Knight Rider effect.

For this, might I also recommend a lambda link. Guages will also make your car feel more focussed, and intended for high speed action thats why I bought them.

 

The standard JECS has a basic map and will learn to advance to suit fuel and local conditions. It is possible to reach the retard limit of the map and so have continuous detonation. That is why many Phase II Sti V engines have let go.

Either a blown piston or knackered bearing due to increased heak soak and increased (badly timed) pressure in the cylinder due to pre-ignition.

The Link will enable safe (ish) running by retarding 1 deg for each knock event in a specific load cell. It has a maximum retardation of 6 degs. If you exceed this and continue to get detonation then God forbid.

The standard approach to fitting a Knock Link is to also fit a second knock sensor - belt and braces. So with a Link if the standard knock sensor fails you still have a visible warning of impending doom.

To my knowledge, with a JECS a knock sensor circuit failure will cause the engine to stop running and the Check Engine light will flash a semaphore at you indication Knock Sensor Circuit failure. If the sensor is subsequently disconnected then the car will run in JECS failsafe mode which will not allow boost to build up and will limit revs to around 4,000rpm. (I have not experienced this, however this is true for the other key engine sensors so I draw the analogy).

Also, AFAIK, the new MY01 has a different advance philosophy where a very advanced ignition curve is used and the ECU will then retard in real time to suit the prevailing conditions. The scope for retardation in this scenario would seem to be greater and therefore safer. Perhaps less need for a knock link.

Finally, also AFAIK, the Motec does not have automatic retardation - but you would need to check this. I was told this by a Motec owner and was somewhat surprised!

Splish, splosh,

Trout

 

Thanks for all your input/time guys.
OK - its a visible check on whats happening, as long (I suppose) as its fitted/working correctly.
I still do not know if the PD ecu will retard until det stops or not with raised boost, and if octane boost will help/cure det at high boosts.
My other worry is that my ecu (PPP) has never cut out even at 21psi (allegedly).
Stan

 

Thanks for all your input/time guys.
OK - its a visible check on whats happening, as long (I suppose) as its fitted/working correctly.
I still do not know if the PD ecu will retard until det stops or not with raised boost, and if octane boost will help/cure det at high boosts.
My other worry is that my ecu (PPP) has never cut out even at 21psi (allegedly).
Stan