Lotus Esprit V8 "In-Dash" Knock Sensor Alarm

Now that additional performance modifications have been completed and installed, it is imperative we know whether the Electronic Control Unit/Module (ECM/ECU) is providing the engine with enough fuel under high boost and/or load. If the mixture is to weak, and the engine is starved at high boost and/or load levels, irreversible (and very expensive) engine damage can occur.  In order to ensure this does not even get close to happening, Air Fuel Ratios must be monitored closely during any high performance testing situation.

Now, you can go and buy the monitor from your favorite after market parts store, and install it somewhere in the car where it is guaranteed to look like an "afterthought", or you can do a proper job.  We chose to build our own Knock Sensor Alarm and integrate it into the Dash so it looked if it was there from the factory. This takes a lot of planning and measuring, in the long run it will look perfectly acceptable to the most discriminating connoisseur.

The first thing you need to do is acquire an electronic Knock Sensor Alarm, or make one using our plans as described in this article.You will need to be reasnablely proficient with a soldering iron and lead solder, as you will be using them a lot. (Or you could get someone else to do it)

This article is for the real "Do It Yourselfer", we designed and built our own Knock Sensor Alarm, and that is what this article covers.  If you buy one ready built, and want to install it in your dash, as we have, then simply skip the Schematic Diagram part and go directly to the in-dash installation.

Main Knock Sensor Alarm Schematic Diagrams

For those who have a reasonable understanding of electronics, here is the interesting part.  The following diagrams show the details of the monitor:

Knock Sensor Alarm Main Schematic Diagram (Not To Scale)

As you can see by the schematic, there are very few components. The heart of the unit is a NE 555 Timer Integrated Circuit. The signal comes into the unit from the ECU/ECM Signal side of the Knock Sensor.  This signal can be derived directly from the Knock Sensor itself, (Located under the intake plenum, and REALLY hard to get at) or from the ECM Pin ? (TBA). We chose the ECM Pin ? source. We unwrapped the ECU wiring loom about 2 inches, located Pin ?, spliced into it, and re-wrapped the loom.  This task took a grand total of 30 minutes so it is not hard, if you know where to look.  The ECM is located above the right hand fuel tank.  You will need to remove the cosmetic right hand shelf to get at it.  Remember to DISCONNECT the BATTERY BEFORE beginning any work in this area. We simply removed the ECM main plug and worked with it in situe. Once spliced in, the wire can be run through the hole that was previously made in the rear firewall. (Please refer to the details on installing the Water Injection System or Boost Controller for details)

If you wish to construct a Printed Circuit Board as we did, here is some more diagrams that you may find useful.

Main Component, Layout, Component Side, Actual Size

Main PCB, Trace Layout, SOLDER SIDE, Actual Size

The power for this device is derived from +12 volts from the positive terminal of your car battery via a 1 amp fuse. (or some other fused source, we used the dash/fascia board light +12 volt supply line) It also needs a good ground. (Again the dash/fascia lighting ground was used)

As you can see the circuit fits quite nicely onto a small Printed Circuit Board (PCB) we made ours using standard "off the shelf" parts, easily available parts from Radio Shack. Total cost to build is about $25.00 in parts plus your time.

Installing The Knock Sensor Alarm in the Lotus Esprit Dash

This is the part we were quite concerned about doing, but a quick call to our friendly Lotus dealer, reassured us that the parts we were about to potentially destroy were available as replacement parts. The cost surprisingly enough was not as expensive as we initially anticipated. Armed with this "insurance" we proceeded very cautiously. The following steps involve drilling and cutting the dash assembly. Unless you are pretty good mechanically, we recommend you simply read this for interests sake, and put a commercially available Knock Sensor Alarm somewhere in your car. If you do choose to remove the dash assembly for any reason, do not forget to DISCONNECT THE BATTERY.

Step 1 - Remove The Dash Complete With Gauges and Wiring

This is a very easy procedure. You can refer to the Lotus Esprit V8 1998 onwards, workshop manual for details. We proceeded as follows:

• First remove the 2 allen screws holding the Binnacle over the dash/gauge assembly, then slide the Binnacle forward and remove it. Put it to one side and store.
• Remove the two black sheet metal screws on the left and right had edges of the dash assembly.
• Remove the two bolts and their associated lock washers that secure the dash to the main body of the car. These are tucked away at the base of the dash assembly, one on the left and one on the right. They each go through a lug on the dash assembly, and are easy to get at.
• Remove the two electrical plugs that provide power and signals to the dash, this is a little tricky as they are tight. Take your time and they will part sooner or later.
• Remove the dash assembly and place it on a clean protected workbench. (We used towels to protect the dash form unnecessary scratches)

Now that you have removed the dash assembly, the fun can begin.

Step 2 - TBA

We hope you find this article interesting. Please email us if you would like more information on you can get one.

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