GM 2 bar MAP Sensor

[slobra96]

I am a member of the FSAE team for Temple University and the engine we are using is from a 2007 Yamaha Phazer. We first tried to use the stock map sensors but they did not seem to work. We then went to autozone and purchased a duralast map sensor from a 2005 Cobalt SS which uses a gm 2 bar sensor so we figured they would be the same. Now when we got back and plugged in the values(which we found online) to calibrate it, we get map readings for around 70-80 Kpa. It definitely runs a lot better with this map sensor when compared to the stock ones, but the it idles very high and keeps on reving higher. I was just wondering if we did something wrong with the calibration or do you think this duralast map sensor wont work because its not a true gm 2 bar map sensor?

What we plan on doing now is buying a gm 3 bar from online, but just wanted to hear some peoples input before going ahead and doing this. Thanks

[24c]

The MAP sensor shouldn't make that much difference, and I would think the stock one was a 1bar type, as the engine isn't turbocharged. AFAIK, fitting a 2bar one isn't detrimental, but I don't know whether the sensitivity is different without trolling spec sheets.

70-80 kPa doesn't seem too high for a high revving modern twin cylinder. I am running around 70 kPa at 900-1000 rpm (idle) on a 1990s YZF1000 engine, but your advance settings will affect this. Single cylinder bikes have spiky MAP transitions, and your twin will be no different, but you say it is better with this 2 bar sensor, and keeps on revving higher...is that just at idle? Is this as the bike warms up? If your ignition or fuel values vary with the MAP fluctuations at idle or your WUE is not set up you might see this. Also, is there some sort of mechanical warm up enrichment on the throttle body?

I think it is likely to be a settings issue, so why don't you datalog the behaviour and post a .msq, that way we can see what is happening.

[slobra96]

Sorry I wasn't that clear when explaining it, but the map sensor reads around 80kpa with out the engine running when we enter the correct values in from online. When we started it, it would only idle with the computer unplugged, and it seemed to be idling around 3k. We then tried messing the with map values so it would read 100Kpa when it wasn't running, and this caused the engine to sky rocket up to 5k when we started it. The map values were almost down to 30kpa when it reached 5k before we shut it down.

Do you still think its something the settings?

[24c]

Sorry I wasn't that clear when explaining it, but the map sensor reads around 80kpa with out the engine running

OK, that could happen if you were at high altitude, but have you got the map sensor wired correctly. Obviously you have some calibration values for the MAP sensor, OEM or otherwise and you have put these in your table. 30 kPa does seem a little low for a motorcycle engine idling, you would get this on a closed throttle on overrun, but I wouldn't expect to see this on a normal intake.

Are you running the restrictor set up?

[dontz125]

24c - he says he's getting 80kPa with the engine OFF. If this is the Temple University in Philadelphia (39 fasl), it SHOULD be reading a lot closer to 100kPa.

Either you have some significant calibration issues, or your Vcc to the sensor is way off.

[24c]

Thanks for that dontz125, I realised second post he said engine NOT running, but had no idea where Temple University is, being a Brit, so I was just being polite with the high altitude. I reckon it's a settings or wiring issue too.

[dontz125]

Heh - I'm Canadian, and my first thought with "Temple University" was Utah & the Mormons. A quick Google later - nope, Philly it is...

[Bernard Fife]

s96,

It's worth noting that the MAP sensor reading wrong (or any other sensor problems really) will not cause excessive rpm. All those sort of problems will reduce the rpm. The only thing that can cause excess rpm is a vacuum leak (i.e. too much air entering the engine).

This can be a missing/misaligned gasket, a missing vacuum fitting, an IAC stuck open, a throttle stop mis-adjusted, etc., but somehow the engine is getting too much air. So fix that first before doing anything else.

Lance.

[slobra96]

Thanks guys, were gonna try calibrating it ourselves tomorrow and try it again. I will update you guys tomorrow, thanks for all your help. And yea Temple University is in Philadelphia, PA hahah.

[slobra96]

We calibrated the map today our selves and it works like a charm. We also figured out why it was reving up so high, and it was because of the IAC being open all the way. Thanks for all your help, Ill let you know what other problems we run into.