joecitizennn

How effective is the KLR at controlling detonation? Does it simply retard timing in responst to knock or are there other things it does as well?

Thom

Under boost, in case there is still knock after it retarded ignition, it uses the cycling valve to reduce boost.

joecitizennn

it seems then that the KLR would be worthless protection against pre-ignition in a system where the timing valve was bypassed.

Thom

Definitely.

Oddjob

Hard to say. I have seen a stock motor destroyed from detonation. The KLR did not protect it. I have done a lot of trouble shooting and testing of the knock systems on a couple cars, and could not confirm that the KLR will actually pull timing or reduce boost. You can unplug the knock sensor and drive around, and the KLR will never identify a fault with the knock system. So I am no longer convinced the KLR on the 951 is a good, functional knock protection system.

W/o the CV, the KLR cannot reduce boost in a knock situation. But, if the system is functioning correctly, it would still have the ability to pull timing up to 6 deg on the knocking cylinder. I just dont know that it will actually do that.

joecitizennn

what good is retarding timing when you are dealing with possible pre-ignition?

Oddjob

Are you asking about pre-ignition or detonation?

Chris White

The stock system does a very good job in protecting the engine – if it is all stock and all the parts are running correctly. Once you mess with boost levels via an ‘enhancer’, any type of boost controller or a shimmed wastetgate you have changed the basic parameters.

Pulling timing will help to reduce or eliminate detonation caused by too much cylinder pressure. It won’t help much with preigntion caused by hot spots in the cylinder. 6 degrees of timing reduction at stock boost levels will make a big difference in detonation – but if you don’t get the boost reduction you will not notice a large reduction in power and, most likely, you will still run it flat out and you will raise the EGTs by a lot – to a dangerous level!

67King

Yep, the only way to stop pre-ignition is to cut fuel.

Oddjob

Is there monitoring equipment currently available that can be hooked up to a motor/harness to determine if the KLR and knock system components are functional and correctly pulling timing? Something that will log the actual ignition timing on each cylinder for the stock DME/KLR?

joecitizennn

I suppose tapping with something metal in the close vicinity of the knock sensor while the motor is running should tell you if it is retarding timing if it slows the engine idle. That said I have never tried it.

Oddjob

Only if you have the ability to create a vibration that is within the frequency and amplitude that the KLR identifies as detonation through its signal filters. And unlikely that a momentary ignition timing retard of a few degrees would generate a noticeable change in idle speed - but I have never tried it either.

fast951

In theory, you should be able to "tap" on the engine next to the knock sensor in order to simulate knock.

As Jim (Oddjob) mentioned, you must generate the correct frequency and amplitude, which is no easy task to do by "tapping" on the engine. In addition, the "simulated ping" must occur at the exact time the KLR is looking for detonation based on the engine firing.

However, based on my experience, unless you have the proper test equipments, tapping on the engine to simulate knock is trial and error.

As far as knock detection goes, the KLR has all sort of filters and algorithms to detect knock based on the 951 engine architecture. When knock is detected, the KLR retards ignition by as much as 6deg. The ignition remains retarded for a short while then it goes back to normal when the knock clears up.

By relying on the KLR to detect knock and to make its own adjustments, there are ways to allow the user to define what other task to perform (further reduce ignition, reduce boost...).