Re: Quick question
The AEM adds another huge enhancement to that however. You were speaking about frequencies that determine knock, however you didn't mention the amplitude of the signal as it relates to RPM.
The AEM EMS filters for the knock frequencies already, but as RPM goes up, the amplitude of those signals increases drastically. It's this amplitude that describes the magnitude of the pre-ignition or whether the pre-ignition even exists. This is absolutely critical in the analysis of pre-ignition because without mapping it against engine rpm you cannot determine whether it occured.
To even more accurately detect knock we use a knock noise table in the AEM that charts knock sensor voltage as it relates to rpm. It goes from a signal of around .5V at low rpm to well over 4V at the higher rpms. Here's an example of the knock noise table that's included in the base map from AEM.
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Anytime a knock frequency exists at an amplitude over the standard amplitude that the engine generates on it's own (defined by this knock noise table), the AEM determines the amount of knock and it will inject extra fuel and pull out timing in a manner that you specify based on the severity. It will also show up on that datalogs which will allow you to tune ignition timing exactly.
We use this method to achieve over 1,000rwhp in 183 cubic inch Supra motors. Every degree of timing makes a dramatic change in power, and we're able to set timing exactly at every rpm for the gas that we're running.
Did you guys know that you can advance timing from peak torque all the way to red-line? Peak torque will typically have the lowest timing setting, from there we usually pick up 2-3 degrees of timing from to redline which adds quite a bit of power you wouldn't have otherwise known you had.
Here's Ken's Viper that came in yesterday. A very sweet ride.
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I snapped some pictures of underneath and we came up with a few locations for the knock sensors. I'm not sure about the water jacket location by what Doug said. Those are 15mm in diameter, and here's a picture of one of them. There are 2 on each side.
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Here's another shot of the motor.
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After much thought, Sean and I think the best location may be the motor mount bolts that hold the motor mount to the block. It would be a different kind of knock sensor that Doug and one of our tech's here suggested. Those are very common knock sensors and are used in Land Rovers and other cars, so we could certainly use them in our testing.
We will have a prototype Viper EMS here very shortly and will begin using it in conjunction with another Viper Performance Shop which we will mention shortly.
Thanks again Ken for bringing your car in. You may want to mention how your first dyno pull went.
Take care,
Chris.
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Chris, What you are saying makes perfect sense! I am not supprised to see something like that knock table.
From your table, it appears that you would 2.6-2.8 volts at 6,000-6200 RPM which is interesting to say the least.
One thing is for sure: You import guys have been doing the forced induction longer than the Vipers have been around!
It only makes sense you are way ahead of the Viper game in the tuning technicalities and tools to do so.
The AEM system looks to all to Motec does and more WITHOUT having to rewire the car. Plug and play rules!
I predict the AEM will revolutionize all aspects of Viper tuning for forced induction AND naturally aspirated applications!
Hey ==> Hurry up and get that thing done already! Come on now!