Help sought with MAP clamping on 1JZ

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Joined: Mon Jun 13, 2011 1:12 pm

Help sought with MAP clamping on 1JZ

Postby Wilkinator » Tue Jun 14, 2011 7:37 pm

My tuner netted me a very healthy 227rwkw on what he said was 16 psi (though I had asked him to go to 18). Having hit fuel cut a couple of times I tooled around inside the Haltech Interceptor and discovered that he hadn't been able to sort out boost cut and he'd actually pegged boost at 15psi (why I oughta!!!).

Anyway, I've figured out that boost cut is achieved via the Fuel Control, I'm just not too sure what value I should be setting the Fuel Clamp Load Limit to, 70%?, 80%? I've seen mention of 3.9V on other EMUs. Additionally, should I be adjusting the "Load at which to pass freq limit"?

So assuming I'm able to remove boost/fuel cut with the correct clamp value, will it then be necessary to adjust the fuel map? Will I need to pull more fuel out than previously mapped or will I need to add more? My gut says it's just going to run a bit rich if I clamp at 70-80%. For reference I'm using stock turbos, a Bosch 040 and Supra 440's.

Anyway to attach images to posts or is it links only?

Posts: 25
Joined: Thu Sep 10, 2009 9:43 am

Re: Help sought with MAP clamping on 1JZ

Postby vosadrian » Thu Jun 16, 2011 3:29 pm

There is two ways on the interceptor to clamp a signal to avoid a boost cut. Which way you use depends on what the stock ECU uses for the boost cut. If the main load reference of the stock ECU is a map or maf (air flow) sensor, and you are intercepting this for fuel control and this is also used for boost cut, then you can use the fuel clamp load limit to put a clamp on the fuel output. Ideally you just keep lowering it until you get no more boost cut, but realise that since the ECU uses this for the ECU load for fuel calculations, that the result may be leaning of the mixtures once in the clamp condition, so you want to just clamp it before the cut level and not much more to maximise the fuel capability.

If the ECU has an air flow meter (used for fuel control), and map sensor, it may do the boost cut based on airflow and/or boost. The interceptor has a seperate function to enable you to read MAP signal on a spare analogue input and output the signal but clamped on a spare analogue output. The settings for this are in the analogue inputs section under map sensor. You can select a slave output to clamp in the input section. You can run both clamp mechanisms at the same time if desired.

I am not that familiar with the ECU you are using to know which applies. You also should be able to datalog the output signals with the software to see the clamping in operation.

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Joined: Tue Jan 18, 2011 11:04 pm

Re: Help sought with MAP clamping on 1JZ

Postby Jaronimo » Wed Sep 21, 2011 12:11 am

Hey there, I have a similiar problem with my interceptor running on a 99gt forester tuned to 12psi running the stock EBC bleedoff wastegate system,my problem being it hits boost cut at 15psi since the cooler days started, tuned in end of summer

I have also looked into the map setting and can see the overboost level in analogue signals map 1 is set to 35psi? 2393mbar,
and the map clamp level set to 26psi 1793mbar

how is my boost level set and achieved through the interceptor? can I just lower the boost to move it away from the boost cut, or should I just run a MBC?

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