Thread: MAF->MAP conversion with Tunercode?

Does it matter that our motors usually pull about 20psi vacuum?? which is a little over 14.5psi. Or does that have absolutely nothing to do with it??

Yes, it would matter if the engine pulled more than 1 bar at idle or during engine braking, however I think you've confused inches of mercury with pounds per square inch. Last I checked our engines never really draw more than -0.8 bar at most which is equal to -23.6 in·Hg and -11.6 psi. Good question though.

Vacuum is not measured in psi.

They don't pull 20 PSI vacuum, they pull 20 in/hg vacuum.

If you wanted to convert the 20 in/hg to a unit of psi, it would be -9.8 psi.

The GM 3bar can read from about ~ 29 in/hg vacuum to 29psi of pressure.

You just need to get the units right, as your boost gauge has two different units for pressure and vacuum.

Exactly, in/hg and psi are totally different readings. I have my aem setup in kpa and with the car off your kpa reading will be 100 which is 1 bar, at idle your kpa is around 30-40 depending on your engines vac pull.

Dont get them confused. For most of us a gm 3 bar sensor is perfectly fine

1 bar absolute. 0 bars relative. Man I hate relative pressures... That's why we love Pascals. They are always absolute. =D

Edit: I take that back. Pascal can be used relative too.

Just basing that comment on my personal opinion, from personal experience. A buddy of mine in a stock bottom end LS/Vtec swap would need around 19psi of boost to achieve my power levels at 15psi when I had my car. We both had EL manifolds, he had a 3.5" TBE vs. my 3" TBE, and he had a 35R vs. my 30R. His setup was very well put together.

Just saying

lol, yeah gotta include the absolute and relative in there. haha Its easy to understand when you get the hang of it. Hell your the one that confirmed to me about the whole 1 bar absolute thing anyways. I kinda figured thats the way it worked but you confirmed it when we spoke.

Its easy though, people just overthink it.

I think that may just be from a lack of displacement. Especially for the torque numbers, lol. But most honda's ive seen boosted make pretty good power on lower boost levels.

Please take the Honda vs. Nissan discussion to another thread.

And Pascal is just another unit of pressure measurement that can be absolute or relative (gauge) pressure.

Thanks,
Dave