Boost sensor info

Re: Boost sensor info (vlvman)

[showing ignorance here]

Isn't this a GREAT way to have a boost gauge without having to T the vacuum hoses, kink them through the firewall etc?

all electric = no leak!! me likey

Grants further investigation!!

http://********************/smile/emthup.gif http://********************/smile/emthup.gif

I have not seen a BG install based on this principle (except IPDs datalogger I guess)....has it been done before?

Re: Boost sensor info (vlvman)

Nice work... going to see about a redesign for my boost gauge that I have now with this valuable infor.

Re: Boost sensor info (vlvman)

The MAP (manifold absolute pressure) sensor isn't reading 0psi at ambient, it's reading your local barometric pressure. 15.5psi is a little high, so let's guess that it reads about 0.5V in a true vacuum (0psi).

If you want a tru "boost" gauge, you'll need to subtract off the ambient baro to read the actual turbo pressure rise. Usually, this is what people want to measure. The ECU, however, wants to see absolute, because it's using it to make mixture and emissions decisions.

Good info, and have fun with it! Be sure your tap to measure the signal doesn't load the value seen by the ECU. A high-impedance digital VOM type reading is best.

Tom.

Re: Boost sensor info (MightyQ)


Haha seen it first hand in Nick's car, it's a beauty http://********************/smile/emthup.gif. That was my point that you'd need a control module to take in the signal from the sensor which in turn makes it easy just to use an electronic gauge.

Re: Boost sensor info (tmtalpey)


ah so is this MAP or boost? (I feel like I've read discussions on this before, and I know you (Tom) answered before, apologies if that is the case)

IIRC MAP can be read from OBD (which is even better, not even a high impedance connection is required)

So to the OP, is this MAP or boost? I would have thought that these cars measure boost.....so there's got to be an atm. pres. sensor somewhere in the car

Re: Boost sensor info (FEO)

The raw reading from the sensor is MAP - the actual pressure not the boost. Boost, as it's usually defined, is the relative pressure, i.e. the rise over atmospheric. That's somewhat more interesting if you want to know how much work the turbo is doing.

Also note most "boost" gauges plumbed into the manifold have a negative range, to show you when the engine is actually pulling on a closed throttle. Any negative reading is certainly not absolute! But it's interesting from an engine-load perspective and is typically what drivers want to see.

The sensor in question isn't located within the manifold, it's on the intercooler output before the throttle plate. So it won't ever go "negative", in fact it may stay significantly positive even when the throttle flap is closed.

Because these cars use a MAF computation, measuring air mass to compute their mixture response, they don't technically require a MAP sensor to operate. But the MAP is important to monitor turbo performance, and guard against overpressure and detonation. And, the sensor is certainly handy.

You cannot read the R's MAP with standard OBDII protocols (the 0x0B PID). Volvo turbo engines don't provide it, though most Volvo NA engines do. One can, however, read the value with proprietary tools from within the manufacturer-specific ranges. This is not at all easy, or universal across the product line. Very few Volvo-compatible units support this.

Tom.

Re: Boost sensor info (tmtalpey)

ahhhh thanks for the explanation Tom. Neat trick with the abs pressure cal. with engine off.

if only I had a million dollars...and a million hours





http://www.freescale.com/files...A.pdf

Too bad Juve has a boost gauge already

Re: Boost sensor info (FEO)


lol, nice.

who needs ECT anyway

Re: Boost sensor info (phuz)


LOL I know

I have been an advocate of extirpating that useless temp gauge and reuse it to show boost instead. This gauge doesn't serve any purpose currently

a) It doesn't tell you the actual temps
b) It goes to the middle and stays there, impervious to even engine blowup!!!! (someone had this happen)
c) the engine actually tells you on the DIM when it's too hot, so why have this "on/off" analog gauge at all???
d) it would be even more classy than MightyQs install!!! (hard to achieve)


FTW

Re: Boost sensor info (JimLill)

I saw my name mentioned here so I'll jump in....
I'm actually, as we speak working on an upgrade to my simple oil temp led project that I currently have in my R. The new display will be an OLED 96x64 display screen hooked up to a PIC to accept readings from a thermocouple. Maybe boost could be displayed as well through those voltages??!?! Another temp monitoring point I was toying with was Haldex operating temp. But yeah, too bad I already have a boost gauge