Anybody has it??

 

what's that???

 

You mean the ESM??

Only AEM has a replacement, and thats for the entire on board computer.

Nick

 

If you mean ESM (comes in the computech SC kit) then I think it's only useful on forced inducted engines.



E.S.M. (Electronic Signal Modifier)
$149.00
NEW!
This adjustable switch is commonly
used to keep the ECU from seeing a boost
signal from the MAP Sensor when you are adding
a turbo or supercharger to a car that didn't come that way.
Can be used on any car or sensor up to 3.4 volts.
Easy4 wire hookup. Comes adjusted for Honda/Acura
MAP voltage signal, but is easily adjusted to
needs of other cars. Universal fit.
Not subject to CARB certification.

I've been doing research on the electronics end of the CLS, so I can try to understand WTF scalbert and the other guys are talking about (DTC's, ESM's etc, etc)

I must buy the Helms manuals....

 

 

i thought this was only applicable to the SC...

sidemarker

 

It is or even a turbo application. We have a two Bar MAP sensor so it can read above ambient pressure or in other words, up to about 14.7 PSI boost. But the ECU does not expect there to be pressure in the manifold so if it seems any noticeable positive manifold pressure (about 3.5 VDC on the MAP output is the ECU threshold) it will set a DTC. This unit clamps the MAP signal output at 3.4 VDC (by default but is adjustable). Refer to the below:

MAP---------->ESM-------->ECU
1 - 5VDC------------------>1 - 3.4VDC
0 - 2 BAR----------------->0 - 1.2 BAR

The ESM just intercepts the signal before it reaches the ECU and limits the output at a certain level. So yes, the ESM is just used on a boosted engine to keep the ECU from seeing the boost and setting a DTC.

 

scalbert, what happens when the ESM clamps the signal doesn't this mess up the timings?

 

Timings??? Are you refering to ignition or fuel injector timing?? If so the MAP plays little to no part in the ignition or injector timing. So no, holding the value at a certain level when the MAP output reaches or exceeds this value will not affect timing.

In stock form the most the ECU ever sees out of the MAP is about 3 VDC.

 

Okay... in other words, What the MAP is used for? The function that depends on this signal would be "inccorect" when the signal is clamped...

 

The MAP (Manifold Absolute Pressure) is used to determine the amount or vacuum/pressure in the manifold and is one of the primary sensors used in determining load, or rather the amount of fuel needed. It does this in conjunction with the IAT sensor. Since you have a fixed volume in the manifold and if you know the pressure and temperature you can then determine the density and thus know the amount of fuel needed. This is called a speed density system where there is no direct measurement of mass flow but is derived by other known values.

Base ignition timing is a set value based on table look-up from a myriad of parameters; the manifold pressure would be part of it but one among many. There are two other sensors that will affect the offset of the base timing; it is the engine temp and the intake air temp. This is one reason why you have less power in weather; the air is less dense but also because timing has been backed off.

Remember, the stock tables are not designed to read positive manifold pressure so clamping the output is just a method to keep from setting a DTC. Even if the DTC would not be set I doubt Honda would even bother to extends the tables to account for positive manifold pressure when there is no reason (for them) to read boost values and calculate for them on a stock engine.

 

Can we conclude that for FI appication like CT SC the stock ECU is not adequate and an aftermarket ECU like AEM's would be great idea to better tune the SC.

 

Well, yes and no. More modest gain and low boost levels using a rising rate FPR will provide adequate fuel (along with clamping the MAP signal so you don't get a check engine light). But if higher boost levels are run the simple mechanical means (rising rate FPR) of adding the additional fuel won't be enough. Additionally you can squeeze more out of the FI engine by using an aftermarket DFI system since it can be tailored.

But IMO, with the modest levels being run with the Comptech SC the components supplied are certainly adequate. But if someone really goes all out and adds a turbo or even runs the boost up much higher an aftermarket DFI might be a better solution.

 

Scalbert, if you continue posting stuff like this, I might actually learn something

Thanks for the informative post.

JP

 

He always does, scalbert the MAN!

search for all his posts, hes educated...