Is it possible to retrofit a 3 bar map sensor with the stock electronics? What would be the disadvantage of the stock 1 bar map sensor with the stock ECM in a turbocharged application? How does this affect tuning?

 

boost blows the diaphrams in the map sensor. 2 or 3 bars have like a two way valve

 

so what exactly does this mean in regards to his question?

 

What it means is if he uses the stock 1 bar map sensor he is going to eventually blow it. if he uses a 2 or 3 bar he most likely wont because it is no longer using a diaphram to read manifod air pressure/baro pressure.

 

ok cool, where do you get a 2 or 3 bar MAP sensor that will work with our setup?

 

First off the stock map sensor is a 1 bar which means it reads up to atmospheric pressure ,i.e it can not read boost. 2 bar or 3 bar maps sensor are just like a 1 bar just more pressure range.

To put a 2 bar or 3 bar map sensor in the car you would need to do one of two things:

1. Best method - rewrite the code section and data tables of the pcm to accept a 2 bar map. Some of the Australian guys claim they can do this. This way you can actually tune for the extra range. You would have use some special software, probably loose portions of other tables (limited ram).

2. Find a 2 or 3 bar sensor with the same output voltage range. Based on the difference of the curves modify the pcm tables. So if you have a 2 bar map installed instead of 1 bar map you would modify all tables that use the map sensor by a factor of 2. You lose half your resolution doing this.

So it can be done but at this point more hassle than its worth. The maf correctly reports the mass flow until you max out the computer at 512 g/s so the map no reading is not that bad.

Gary

 

Thanks for the info.

So what you're saying is as long as you don't max out your MAF you should be able to tune without any real significant disadvantage. As long as you have the flow value, the pressure value is insignificant?

 

Actually you have two types of pressure sensors: Manifold Absolute pressure (MAP) sensor monitors engine intake manifold pressure and provides engine load information. Where as the Barometric Pressure (BP) sensor monitors atmospheric pressure, allowing for adjustment of A/F ratio as a function of Altitude and barometric pressure. These two types of sensors used to be two distinctly different sensors but now they are combined into one.

BP/MAP sensors that are combined and found on most vehicles to day are what is called a 1 Bar sensor because they have a fixed pressure and a diaphragm and this allows them to read up to atmospheric pressure. When you add a supercharger or a turbocharger you well exceed the limits of the Diaphragm. This stretches out the lining in the diaphragm and eventually it will rupture.

That is why you wish to go to a 2 Bar or 3 Bar sensor depending on application. The 2 and 3 bar are similar design and function of the original Barometric pressure sensors in the way that you almost have two opening points one for Baro pressure and the other for Manifold vacuum. This is what is called a Differential pressure sensor where as the 1 Bar is considered an Absolute pressure sensor. By using the Differential pressure sensor you are able to apply boost with out worrying about blowing the diaphragm.

A 2 bar MAP sensor are used to measure up to 15 PSI of boost. They can measure more but you would be pushing it. 3 BAR sensors on the other hand will measure up to 30 PSI of boost.

Personally I would install a BAR 2 sensor and then tune for now not having a fixed pressure in the MAP sensor. Even if you are not maxing out your MAF your PCM looks at your MAP signal for support and for additional tuning. At that point you would be helping it in narrowing down it parameters for better A/F + Spark adjustments.

 

Thanks for the responses fellas...keep em coming.

So it isn't necessary to change the MAP. However, I personally I would prefer to run a 2 bar MAP considering the info from Jlm44.

Red ws6 99, I'm trying to understand if the resolution lost when using a 2 bar map sensor would be significant. It's possible the resolution of the ECM is the limiting factor of overall resolution. It may be wishful thinking on my part, but without knowing the range of the microprocessor we won't know for sure one way or another. Do you know what kind of A/D's are used in the microprocessor? I have an electronics background so if you have any information I may be able to determine if the lost resolution is significant or not.

The big question is if there is a 2 bar map sensor with a similar output voltage as the stock sensor?

 

Email keith@hptuners.com he was working on a way to use a 2 bar map sensor with the stock pcm.

I run a 3 bar with my FAST bank/bank.

 

The resolution I am talking is editing the data tables in the ecm with hp-turners or ls1-edit. You only have a few cells that correspond to map points, etc. When using a 2-bar map the computer still thinks that a 1 bar is connected.

There are several 2 bar maps that have the same output range as the stock unit. I believe the cyclone map has the correct output.

Gary

 

what is the cost for a cyclone MAP sensor? Our 1 bar is like 76 bucks

 

I don't have LS1 edit, but a screenshot of what you're referring to may be useful if you could. What value are the datatables made up of? If it's a 2 digit hexadecimal value, I would assume the microprocessor is using an 8 bit value.

Also what range of values are inputted in to the cells that correspond to map points?

I would like to get a little bit more background on the subject before contacting keith at hptuners.

Edit: The fact that there are not many cells that correspond to map points may indicate that high resolution is unnecessary.

 

B_Pay- I can't for the life of me remember what bit value the microprocessor is using...I have all the information that you are mostlikely looking for in my book at school. I try to post it later on tonight other wise I'll post it first thing tomorrow morning.

 

Any luck jlm44?