Detonation warning indicator

[Vipermed 97.01]

we have been in the process of designing a dash or steering column mounted led light warning of climbing cyl. pressures,that will be displaying real time,we are finding that with some of the louder Vipers and some of our cust. that arent sure weather they are hearing damaging detonation or not this will be a good indicator to let you know if you are in the danger zone or even getting close,I will be installing prototype on my 97 tommorow,will be sharing results soon

 

[HP]

Scott, is this just a knock sensor - to pick up on the irregular
signals from pinging - with a red flashing display.

It would be nice if it could be mated with a MSD advance retard.

**I posted the prospect of this combination on another Viper
site and a VCA member - Davem - said he is an electrical/computer engineer, and he would have no problem providing the units, but
it would be a few months before he could get to it.

 

[davem]

Scott,
That was me that offered to take on Hugh's suggestion, which I think is a very good idea. I'm busy building our TT Viper, which will use a knock sensor and can't take on his project until we are done. I offered because I will be doing the following work anyway, and it would be simple to take it to the next step for him and interface it to the MSD box. I do one off electrical stuff like this for customers all the time.

You probably already know this, but here goes anyway:
There are two major types of voltage output piezo knock sensors, one type are tuned to specific "ping" frequencies (usually 4-5Khz), and others recoginize a broad spectrum of noise. So you will find you need to record the output of the knock sensor and find a way to introduce knock into your engine, with your SC it should not be a problem to get a good audible ping.

Sample the knock sensor output, and electrically filter everything else out so you don't flash your light when your not getting knock. It could also change depending on where you mount the sensor, you may want to experiment and see where the stronger knock signals come from. A filter and peak detector or comparitor circuit should do the trick. Are you using a 1 or 2 wire sensor?

Keep us posted- I can help if you want,
Dave.

 

[John Moore]

Vipermed,
That sounds like an awesome product. Do you have any projections on cost?

 

[MES]

If you want to make a simple knock retard switch using the MSD box here is how:

BTW I drew a schematic then realized I left my digital camera at work so I couldn't post it, anyway:

1. Use the MSD box, Knock retard sensor, and a relay
2. hook it up per schematic shown (crap no camera)

3. The relay is normally closed and placed in parallel to the MSD ***, thus shorting out the MSD *** (the variable 1-2-3 knob)
4. When the knock sensor detects the knocking it opens the relay allowing the pre-set knock retard knob to retard the timing (i.e. if you set the knob at #2 it would retard the timing as if you moved the knob from the zero to the #2 position in one nano second)
5. This assumes two things 1) the knock retard signal is constant and not pulsating 2) the MSD *** is at zero ohms when the knob is set to zero. If the *** is not zero ohms at zero, adding a resistor in series with the normally closed relay will solve the problem by choosing a resistor value the same as the "zero" setting on the MSD ***. This same optional resistor could be used to pre-set a minimum amount of timing retard, example it could be set to the #1 setting so it would never retard the timing less than 1

Essentially the MSD box will be set to zero (or the pre-set minimum) all the time until it detects a knock then it will retard the timing (pre-set by the MSD knob) until the knock goes away. Once the knock is gone the MSD box will return to zero again. A cheap and dirty way to protect your engine. A more sophisticated variable retard could be devised (i.e. would take out just enough timing to stop detonation) but this would be rather difficult to perfect and potentially unreliable IMHO.

 

[WESTCOAST JASON]

I am convinced that the knock sensor you describe would be a hot seller. The theory of operation sounds great and the fact that the retarding by MSD is done by modyfing the crank sensor as opposed to the camshaft position sensor allows them to not 'bump' heads. My testing has shown that you can get a 'dual' retard using the MSD and any other piggyback on the camshaft sensor as long as neither off them attempt to pull more than 10 degrees. If you pull 10 total from both methods you trip a light.....

Mapping my splitsec to pull up to 10 as a base map and using the MSD as designed for 'specific' times (traffic heat soak etc.) gives the additional needed retard. Cold days and no heat soak there is no use for the MSD, once up to temp and warmed heads will require just a touch of the msd (less than 1 on the dial) - your knock sensor in place of boost sensor should be PERFECT for a handsoff approach.

.02

 

[HP]

By the time you progress to the point of worrying about the
possibility of pinging - your car usually is too loud to allow you to pick up on the audible warning signals. I would feel better about letting
the electronics correct the problem through a retard device, but it would also help to have a LED alert- light display. When someone builds a combo unit, there will be a line of buyers waiting - if the price is reasonable.

 

[MaxedGTS]

Hey guys.......I already have a knock sensor on my DLM car. I know it wasn't cheap but it works like a charm. It does not pull out timing by itself although Doug said he can make it work that way. I can tell were I need to remove timing and what type of fuel to use. It has a gauge and warning light and you can use it to data log. I'll try to post some pictures later.

Max

 

[v8huntr]

i have installed MSD knock alert in my car and it works great. MSD unit is bolt on and you can get one from jeg's or summit for $149.

 

[prevnine11ownr]

What about a pyrometer?? I have the computech in my 69 Z28....works great. It taps into the header and gives me real time exhaust temp..

 

[HP]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by prevnine11ownr:
What about a pyrometer?? I have the computech in my 69 Z28....works great. It taps into the header and gives me real time exhaust temp..

<HR></BLOCKQUOTE>

Exhaust temp is one variable to check A/F fuel mixture, at
one time it was one of the few available methods -
now we have the wideband O2 meter. But pinging has other
origins besides A/F ratio - it also is a factor of cylinder
pressure - from forced induction and NOS

 

[KepRght]

build it and they will buy