An EGT reading will tell you that you are in a dangerous state - but it doesn't tell you why. It could be timing or fuel ratio.

AFR readings from anything other than a wide band lambda sensor is pretty much uselsess. When people talk about monitoring AFR for engine tune - it should be with a calibrated wide band limbda sensor.

A wide band lamda sensor measures partial pressures in the exhaust to interpret the components of your induction charge. Unlike O2 sensors which are only accurate around a very narrow range near stoic a good wide band lambda can provide you with your AFR from 10:1 to leaner than 20:1 - if it has been calibrated for your fuel inputs (i.e. gasoline, methanol, propane, etc.) and has been calibrated for any water injection rate (since water injection dilutes the partial pressures and apparently tends to cause readings closer to stoich than truly exist).

In knock limited tuning situations, most setups have known AFR limits. For instance a given engine may run fine at 20psi and 11.25 AFR at MBT with 93 octane, but need to be at 11.00 AFR with 91 octane and 10.50 AFR with 89 octane. This is why many prefer to tune by AFR - the target is known from many uses. Once you are at the target AFR the tuner is able to tune to MBT. This becomes the "preferrred" tuning and monitoring tool for tuners that want to run at MBT and use fueling levels to suppress knock.

Yes if you run past MBT you will get knock at appropriate AFR levels even rich AFR levels.

With water injection and other knock suppressing technologies AFR no longer becomes a target - but a result. Without knock limits you can tune for maximum AFR power - using either a dyno or cylinder pressures. Then you can advance from there to MBT.

There is no single best monitoring tool. EGT is a quick check if everything is OK, but will not tell you what exactly is out of tune fuel or timing. AFR is good only if you know what your AFR is supposed to be for the components your charge mixture in the cylinder (including correct octane) and the sensor is calibrated for your charge mixtures. To the extent possible good quality knock monitoring with timing retard will protect your engine - but does not necessarily resolve a bad tune.

Hi all,
the trouble with knock detection is if your engine hasnt got a system on it, like mine hasn't, then i think its very difficult to detect as the after-market systems Ive heard of are a compromise, so im led to beleive. I did hear of a chap who recommended making a tube with a horn type of arangement on the top and bolting that to the cylinder head to amplify any noises, but thats a bit impractical in my mind,
Phil

That is a good way to detect knock. The Aquamist manual for the 2s installation gives directions for doing that.

Brad,
Im sure your right but would it amplify it loud enough to hear it while driving do you think? Also my bonnet line is close to the engine so they would need to be quite small,
Phil

If you don't have knock detection a Steelman Chassis Ear or something similar would be a good listening device. Comes with headphones, an amp etc..

A peice of copper tubing smashed on one end and bolted to the block with a doctors stethascope(?) connected to the tube. Have seen this used on a chassic dyno by the tuner.

Of course, too much ignition advance and/or bum A/F ratios can raise EGTs to dangerous levels (and increase risk of engine damage from knock). My comment that EGT will always be reduced with more ignition advance with injection of alcohol or water, is ONLY up to the point of not exceeding the new injection produced knock threshold while maintaining the proper A/F. That's a tuning common sense given, but guess I didn't stress that completely enough. TuboIce has explained it much better in his response above.

Brad,
I like the sound of the idea, especially as its quite cheap and not too difficult to do, would anywhere on the heads do to bolt it on? As I have 2 heads, no im not a monster (wife probably disagree) I assume i could just connect both copper tubes together with a tee peice and use some form of ear peice connected to that?
Phil

Philip, Any where will be fine. the nosie will travel through the engine. A head bolt or a place on the block will do. The is a company, Diamond Racing that has a knock sensor the taps into the water jacket. It can be adjusted for sensitivity. I gives a 0-5 volt output as knock increase. Do not beleive they have a web site. The price is about $600.00.

Thanks Brad,
$600 is a lot of money compared to a bit of copper tube, so I think I'll try that,
Phil