Hi boost with a MAP Sensor

greypride · Post by **greypride** » Sat Jan 06, 2007 5:15 pm

Hello

ive just been reading on the site that the MAP sensor reads upto 255 KPa, about 21 psi of boost

Is there another sensor that can be fitted into the unit if i plan on running upto 30 psi?

Thanks

4600cc · Post by **4600cc** » Sat Jan 06, 2007 5:20 pm

255 kPa is actually 36.975 PSI

a lot, and not practical on pump gas!

You can also use TPS, explore that option. But yes, to my understanding another MAP sensor could be used, AND the new firmware will support MAP sensor calibration. So by the time you get around ordering parts, you will be able to calibrate for the new MAP sensor if needed.

greypride · Post by **greypride** » Sat Jan 06, 2007 6:11 pm

excellent

its been a while since ive had my car running, but i think it reads about 100kpa on idle, and my 14psi was something like 195kpa

so does that 255 include atmospheric pressure? (sorry if thats a dull question, im just trying to get things sorted in my head)

Ill be using the MAP sensor as its ideal for the turbo as i can run more advance when the car is low/off boost

also would it do any harm to the sensor if more than its max pressure was run on the engine, (so that i could retard it at max value) or would it cause damage to the sensor?

right now to look into this calibration lark

Thanks for your rapid reply

Post by **brentp** » Sat Jan 06, 2007 6:18 pm

The MPX4250 measures 255KPA of *absolute* pressure, and yes that does include atmospheric pressure. It does <b>NOT</b> read up to '36 psi' of boost.

There are GM MAP sensors that will go up to 3 bar- they are external units, however. The 3.1.0 firmware will allow you to recalibrate the controller to use an external MAP sensor like this, so that is a good thing! So in the future the "TPS" version of the controller will really be a "TPS / External MAP" version.

Regards,
Brent

MartinM · Post by **MartinM** » Sat Jan 06, 2007 6:21 pm

The 255kPa does include atmospheric - so the max boost it can measure above atmospheric is about 150kPa or about 21psi.

The sensor data sheet isn't clear about the max pressure before it gets damaged - it may damage straight away, after an unknown period of time or be OK at 350kPa for ever. Maybe someone should try it!

There's nothing yet published about how the sensor calibration will work in the new firmware (as far as I know) apart from that it will be there.

So the challenge is to find an easily available, and cheap(!) and reliable commercial pressure sensor that operates on a 5v supply and reads 0kPa to 350kPa absolute....the hunt is on!

Post by **brentp** » Sat Jan 06, 2007 6:32 pm

Freescale has a line of pressure sensors that read beyond 255KPa, that cost about as much as the MPX4250AP. Unfortunately, they're not completely hobbyist-friendly as they are all surface mount designs. Not impossible to use, of course.

greypride · Post by **greypride** » Sat Jan 06, 2007 6:45 pm

ive been doing a bit a research, (on someting that i dont really know about)

on this page http://www.digikey.com/scripts/DkSearch ... t=0&Page=3 are some details for the sensor we're using (MPX4250A-ND)

If you compare that to http://www.digikey.com/scripts/DkSearch ... t=0&Page=4 and the sensor MPX 5700A ND

from what i can read there they seem to be the same, but im sure theres something im not correctly reading there, would it be a case of unsoldering it and recalibrating the unit?

I also found this pdf http://rocky.digikey.com/WebLib/Motorol ... SERIES.pdf
It states the properties for the sensor, and at the top of page 2 the maximum exposure value of the sensor is 1000kpa

im using version 2 of the board, will i still be able to run the configure things with the software?

many thanks

Post by **brentp** » Sat Jan 06, 2007 7:18 pm

It looks like you might've found a drop in replacement candidate for the MPX4250AP. I think it's a pretty new part since I did some extensive searching on this recently!

<a href="http://www.freescale.com/files/sensors/ ... 0.pdf">MPX 5700 datasheet</a>

<a href="http://www.freescale.com/files/sensors/ ... A.pdf">MPX 4250A datasheet</a>

Appears the pinouts are the same. I guess I need to get a sample!

Edit:

Yes, with the 2x board you will be able to update the load calibration table.

greypride · Post by **greypride** » Sat Jan 06, 2007 7:47 pm

Excellent!!

so when will the new firmware be looking at being released?

how exciting!!

Post by **brentp** » Sat Jan 06, 2007 8:16 pm

I'm working on it as we speak. Possibly by the end of this weekend. We'll see.

Remember, it will be a pre-release version, as stated in the 3.1.0 post it will need some significant testing.

Brent

ivanhoew · Post by **ivanhoew** » Sat Jan 06, 2007 8:43 pm

well done , one thing that jumps to mind is , if one has 5 volts at 101 psi ,therefore a total boost of 101 minus 15 so 86 psi , the sensitivity of the volts per psi ,or ''resolution'' may come into it all , and it wont work as sensitively as before ?
what do you think brent ?
regards robert .
oh brent i forgot to say when testing the latest softweare i was using my old 98 se laptop , so i think it does work on that os.
ill double check it when i get home .

Post by **brentp** » Sat Jan 06, 2007 8:47 pm

Yes, the mesaurable resolution will be proportionately reduced. For that reason the MPX4250 is the best, all-around sensor for both MAP and 'normal' boosted engines. 21 PSI of boost is still a lot!!

Brent

ivanhoew · Post by **ivanhoew** » Sat Jan 06, 2007 9:12 pm

putting a small leak in the boost pipe would fool the sensor and extend the range ?

4600cc · Post by **4600cc** » Sat Jan 06, 2007 9:35 pm

>"The MPX4250 measures 255KPA of *absolute* pressure, and yes that does include atmospheric pressure. It does NOT read up to '36 psi' of boost."

Im not clear here, 255 KPA convert to 36 PSI. Please explain to the stupid, lol.

greypride · Post by **greypride** » Sun Jan 07, 2007 1:03 am

its something todo with the natural atmosperic pressure of the environment (being something like 1 bar (14.5psi), this makes up the difference between the 21psi and 36psi. e.g you its already there on top of what is being measured in the engine.....

(hehe hello robert, it was more fun finding sensors than doing college work!!)

Autosport Labs

Hi boost with a MAP Sensor

Hi boost with a MAP Sensor

255 kPa is actually 36.975

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The MPX4250 measures 255KPA

The 255kPa does include

Freescale has a line of

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Yes! good job!

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I'm working on it as we

blimey nic ,and thats with flu !!!

Yes, the mesaurable

leak ?

>"The MPX4250 measures

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