Problem with MAP sensor clamping

Des Curly
Posts: 22
Joined: Fri Feb 08, 2008 9:07 am

Problem with MAP sensor clamping

Postby Des Curly » Fri Feb 08, 2008 9:21 am

Hello,
I'm new to the Haltech world, having just picked up my shiny new Interceptor Platinum (Miniceptor) this Monday, though I've been researching the Haltech (and other interceptors) for quite some time now and have been familiarising myself with the programming software long before I finally decided to buy.

I'm wanting to hook the unit up to my MY99 Subaru Forester GT to take advantage of my turbo, intercooler and exhaust upgrades. I'm doing the install/setup myself though will be taking the car to a workshop for dyno tuning. Before I hook the unit up to my car, I've been doing some preliminary bench-tests to make sure I know what the unit is doing. This is where my problem has arisen. As part of the installation, I will be intercepting the MAP signal in order to avoid the factory ECU's boost-based engine cut (I believe it's a fuel cut, but that's not important). To do this, I need the Haltech to clamp the MAP signal at a value just below the point where the factory ECU performs the cut. As far as I have been lead to believe (through Haltech's documentation and the software) this should be both possible and also easy to do (it's one of the claimed functions). However, I _cannot_ get this to work. On the bench, I've hooked up power and comms (and can successfully talk to the unit through the software). I have a multimeter setup to monitor the MAP output (I'm using the 99-00 WRX mapping so MAP in is analogue in 3 and MAP out is analogue out 3) and I have a simple variable voltage source to simulate the MAP input. The MAP input seems to work fine. I change the input voltage and the software displays the correct values (according to the MAP voltage-to-pressure setup). However, no matter what values I use in the software, the MAP output is _never_ clamped, it _always_ follows the input, above and below the clamping limit I've given. Clearly this is not what I expected to happen and not what _should_ be happening.

I would greatly appreciate any advice that can be offered that will help me sort this out. I am 99% sure there is nothing wrong with the unit (as I said, it's brand new, never been installed and only ever tested on a bench). Everything _seems_ to be working fine, _except_ the MAP clamping, which is critical to my application. Thanks in advance.

Cheers,
Des

Des Curly
Posts: 22
Joined: Fri Feb 08, 2008 9:07 am

Re: Problem with MAP sensor clamping

Postby Des Curly » Fri Feb 08, 2008 12:10 pm

Problem solved with many thanks to Scott from Haltech.

Cheers,
Des

stevieturbo
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Joined: Sun Oct 14, 2007 2:50 am
Contact:

Re: Problem with MAP sensor clamping

Postby stevieturbo » Sat Feb 09, 2008 2:30 am

Can you elaborate on the solution, in case others come across the same issue ?
9.85 @ 144.75mph, LS1 power :)
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

Des Curly
Posts: 22
Joined: Fri Feb 08, 2008 9:07 am

Re: Problem with MAP sensor clamping

Postby Des Curly » Sat Feb 09, 2008 6:57 am

No problem.

As it turns out (and probably not so surprisingly), the problem was simply with my misunderstanding of the two MAP clamping parameters, one referred to as an overboost level, the other a clamp level. The clamp level does what I had assumed, but I really wasn't at all sure what the overboost level was for.
Operation is as follows: for MAP input signals _below_ the CLAMP level, the MAP output signal is a copy of the MAP input. For MAP inputs _above_ the CLAMP level and _below_ the OVERBOOST level, the MAP output is clamped to (held at) the CLAMP level, fooling the factory ECU into thinking the boost is still at what it thinks is a safe level. For MAP inputs _above_ the OVERBOOST level, the MAP output is again an unaltered copy of the input so the factory ECU sees the real boost level and any safety features it has (fuel cut for instance) can be activated. Clearly then for this to work, the CLAMP level must be set _lower_ than the OVERBOOST level. It is only in the range _above_ CLAMP and _below_ OVERBOOST that clamping occurs. I did not realise this and most likely had either set OVERBOOST to be the same as CLAMP or less than it. It's very simple, once you know how those two variables are actually being used. (The fact that the documentation is for an earlier software version with different labels and features didn't help one bit.)

Perhaps this will be useful for others.

Cheers,
Des

stevieturbo
Posts: 696
Joined: Sun Oct 14, 2007 2:50 am
Contact:

Re: Problem with MAP sensor clamping

Postby stevieturbo » Sat Feb 09, 2008 9:18 pm

Interesting. I havent used one of these yet, but always like to find out as much info as possible before doing so, on how they work.

So I must assume you are using an external map sensor ?

Is the map sensor the main load parameter on your engine ? And if so....how are you finding fuelling adjustment ?

Are you running standard injectors, or bigger ones ?
9.85 @ 144.75mph, LS1 power :)
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

Des Curly
Posts: 22
Joined: Fri Feb 08, 2008 9:07 am

Re: Problem with MAP sensor clamping

Postby Des Curly » Sun Feb 10, 2008 9:25 am

Not sure what you mean by "external" MAP sensor. The Interceptor definitely doesn't have one built in, so _any_ MAP sensor you use is external. Do you mean an aftermarket (versus factory) one? I have an MY99 Forester GT. It has a MAP sensor as stock, which is what I'm using. There's also an AFM, though, which is (and will continue to be) the primary load signal. (TPS will also be wired in, though I'm not entirely sure if/how that effects the Haltech's load estimation.) I'm running stock injectors, though I have no idea what size they are.

I can't comment on how it runs as I haven't installed it yet, as per my original post. At the moment, all my testing has been done on a bench. My plan is simply to install it and set it up to run with no corrections whatsoever, make sure it's all functioning properly, then take it to a workshop to get it dyno tuned. The only thing I may play with before hand is the boost control, as I'm not using the factory boost control solenoid. I have a three-port solenoid (from an RS Lib or thereabouts) that I'll be using, so I will need to play with the boost control side of things to make sure I've set all that up properly (the wiring and plumbing will all be custom work and not making use of stock lines).

Des

stevieturbo
Posts: 696
Joined: Sun Oct 14, 2007 2:50 am
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Re: Problem with MAP sensor clamping

Postby stevieturbo » Sun Feb 10, 2008 10:40 am

If using the standard map sensor feeding the Interceptor....

Then surely any boost cuts/limits etc can only be effective at the same levels as the factory.

If you were to run say 20psi, when the std map sensor stops reading at 18psi, then you could never have an effective overboost limit, regardless of what dummy signals it creates.

AT least with an external map sensor like a 3 bar ( ie, not the factory one ) feeding the interceptor, you could use whatever boost levels you wanted, and retain boost cuts etc, assuming you had enough scope with the fuel control.
9.85 @ 144.75mph, LS1 power :)
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

Des Curly
Posts: 22
Joined: Fri Feb 08, 2008 9:07 am

Re: Problem with MAP sensor clamping

Postby Des Curly » Sun Feb 10, 2008 4:38 pm

You are partially right.
If your factory boost limit occurs because the MAP sensor has reached its peak signal level, then you can't effectively boost higher than that (if the MAP limit was 20PSI, the Interceptor wouldn't be able to tell the difference between 20PSI and 200PSI, for instance). However, if the factory limit is not the result of a MAP limit, then there's still scope to increase boost. My factory boost limit is around 14PSI, but the MAP sensor can go well beyond this. When my factory ECU hits boost cut, it isn't because the MAP sensor is at its limit. As such, I've still headroom to increase boost beyond the factory cut level, with effective control via the Haltech.

I don't remember the exact figures, but say my factory MAP sensor's limit is 20PSI and the factory boost cut occurs at 14PSI. I can still run something like 16PSI with the Haltech. I'd set the clamp level to be 13.5PSI (a bit below the factory cut), and the overboost level to be 18PSI (a bit above my target boost to allow a little overshoot). At 13.5PSI the Haltech clamps the value, making the factory ECU think there's 13.5PSI of boost, a level below where it would otherwise perform a cut. This continues up to my target boost of 16PSI. If things go bonkers and I get above 18PSI, the Haltech releases the clamp, the true boost level gets passed to the factory ECU, and it can perform its cut and (hopefully) stop the engine going boom.

Des


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