NineMeister

Given the lengthy debates that always ensue when we make comparisons between the relative merits of certain engine management systems, I thought that this little snippet from the latest copy of Race Engine Technology would be of interest to some of you who race without the protection of knock control:

"Its all very well talking about adjusting the engine through software but in the real world once it starts to knock you lose it. With our engine it is not viable to let it knock - knock retard isn't effective enough. So our strategy has always been to avoid knock in the first place, by setting the compression ratio and the ignition timing at points where we don't expect knock to happen under normal conditions.
"If we induce knock on the dyno through too high a compression ratio or too much ignition advance, the power will decline. You can retard the ignition in response to knock but you find that you cannot get your power back, even though you have retarded it back to where it was before it started knocking. That is because the knock in itself generates more heat and also it erodes the piston and the head and that increases the surface area , so the surface becomes more open and thus runs hotter.
"In fact the only way that you are really going to stop it is to get off the throttle, let it cool and start again. In my experience you are much better off just to be a bit conservative on the mapping, to the point where it won't knock in the first place."

The words come from a certain John Judd Senior (of UK race engine design and manufacturers Engine Developments Ltd) talking about their current Le Man's 2nd place V10 Judd GV5.5 (5.5 litre naturally aspirated engine which has it's roots in the 1985 Indycar Honda/Judd and 1991 3.5 litre Judd V10 F1 engine).

He then goes on to stress the importance of full wide band lambda control. Seems to know what he is on about....


In the same magazine there is also an article about the Superflow "SmartFire" ignition system which appears to be a production version of the Woodward spark ion ignition system invented by Ed VanDyne.
As well as being a stand alone ignition module, the unit monitors the spark energy demand and uses it to prevent the onset of knock in the cylinder before it actually occurs, in one test on a sportscar engine it was found that engine block flex affected the accuracy of a conventional block sensor to the point where the system removed 12 degrees of timing unnecessarily due to the cornering loads transmitted through the engine.
Similarly a Nascar team using the system found one side of their V8 engine being spark retarded during cornering which was traced to the g-force affecting the mixture of the inside bank - fitting sided accel pump jets solved the problem and the car was faster as a result.

There's a lot more, but you should buy the magazine (excellent read by the way - even at £10 an issue) or do a search on Google to find the rest...

Red rooster

Colin,

Good to see you keeping going on an "anti knock " role !

The John Judd satement of "Its all very well talking about adjusting the engine through software but in the real world once it starts to knock you lose it" is certainley not accepted for production motor engineering .

Le Mans motors are run at very lean fuel ratios at full load for consumption reasons , which makes them very fragile and so motor self destruction is an ongoing problem where knock ,amongst others ,is almost always too close to the edge .
I would find those running conditions not applicable for normal road/race conditions .
I have watched John Judd ( and others )motors explode on a regular basis at Le Mans !

Ion sample during running has been investigated in depth for many years but has yet to become a volume system .

Wide band control , where Catalyst control is incorparated , is a widespread system in use .Take a look at a normal Wide band Lamda part ?

Maybe some reading of Automotive Engineer ( I Mech E ) would clear some of these points from the perspective of production vehicle system development .

Hope you dont think I am attatcking you or John Judd but some of this stuff just makes good publication text and is not too relevant to the bigger world .

Geoff
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KS400200,the oldest 964 on Rennlist,unless you know differently !

NineMeister

Not at all Geoff. Even though the thread was definitely posted with my tongue firmly embedded in my cheek, the serious point is that there are always two views on any subject, but there are very few who can actually see both of them at the same time and I was also careful to specify race engine in my leader line. Judd's experience reflects my own playing with Motec to a large degree, but in production terms with relatively sane states of tune I agree that knock control has its place.
I think the Superflow development is interesting as they appear to be selling a serious development tool that will eventually see production, no prices from them yet though.

Red rooster

Colin,

I recognised the tongue and cheek ! You are wicked !
My life is Motronic + Siemens and yours is Motec .
People probably do not know how many years we have known each other !

I enjoy coming back to the earlier stuff to see what is going on . Still got my C4 with a 993 motor . 17 inch rims and RS brakes . Even that is a bit quick for this part of the world .

Lets see what other replies get fired at you . Maybe we will both get a go at
hammering away !!

Geoff
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KS400200,the oldest 964 on Rennlist,unless you know differently !