Megasquirt Advice and discussion.

[rotaryracer]

MS Systems don't have enough support in the midwest. I've worked with Haltech and MSD w/carb set ups. Some of my friends that drive spec miata's and can't find help that can tune their cars. Rich condition/higher rpms.

[Shadow24v]

Some interesting and valid points in this thread.

I would like to put in my .02 on MS though.

i started with MS as a raw green n00b. Never touched an EMS in my life. I built it from scratch and eventually got it to run. some of the main hurdles i had was no one had MS'ed the v6 i was working with so it was all trial and error to figure out what works. Now, I have launch control/flatshift set up, Knock sensing about to go in, and a decent tune in preparation for supercharging the v6. (which wasn't that hard really, used the clutch switch and it works like a charm) Which, BTW, gets nearly 30mpg highway and mid-high 20s mixed, runs 14.712@93mph in the 1/4 for now and is my DD

That said, I am probably going to go with the MS PnP offered by DIYAutotune for a couple reasons.Mainly COST. i don't make that much and am doing a lot myself and budget oriented where i can. Familiarity is a bonus too. However i will say that there are others that probably have more features, support and what have you, but not everyone can throw $1000-$5000 in for an EMS system.

Again, as stated, to each their own, But i'd say that if someone takes a little time MS is not that big of a hurdle if you RTFM x 20 and take your time. The forums are a big help even if no one has done your motor as 90% of the issues i ran into were easily solves as irrespective to engine specific things. Usually the "Ughnown" is scary because it looks and sounds worse than it really is

[Max777]

wait, so while an RX7 PnP megasquirt is around $450, NOT INCLUDING A WIDEBAND...

and it costs roughly the same ($500) to build the entire system yourself, including a wideband setup, how is this affordable to go with a PNP?

And then you also retain the factory wiring, and all the 20yo sensors as well... which can break and make the car run bad...

Stock you got:

MAP
MAF
Variable resistor
injector resistor
coolant
intake
emissions wiring
etc

Custom install, you got a few new sensors, like the GM coolant and airflow, and a built in MAP sensor in the Megasquirt itself (kinda dumb but I can live with it) fresh wiring, no problems.

[antman0408]

I would rather get an older haltech, you can find e6k's for $500-600 with wiring harness and sensors.

[TitaniumTT]

Originally Posted by Max777

Stock you got:

MAP
MAF

Oh really?

Originally Posted by Max777

Custom install, you got a few new sensors, fresh wiring, no problems.

OH REALLY?!?!?!

[Whizbang]

::waits for stupid owl picture::

[djmtsu]

[Max777]

uhh... i dont get it... You have a pressure/vaccum sensor on the shock tower, and a trap door style airflow meter.... what did I say wrong?

Please educate.

[85rx-7gsl-se]

Its a pressure sensor...A MAP sensor is what is used on FDs instead of an MAF.

[TitaniumTT]

Yeah, one or the other as described in more detail in the PM I sent you.

[Max777]

Well, I know that the trap door sensor is a bit different from a "hot wire" style MAF, and that this is used for fuel on the stock ECU. I also know that the pressure sensor looks at boost/ vaccum and these parameters affect the timing on the RX-7... so what's different between a pressure sensor and a MAP sensor? I thought that these were the same thing, no? And if you cant have both, then why does this car have both systems?

I mean, a "pressure sensor" is fundamentaly the same thing as a MAP sensor, they both sense pressure, or am I totally missing something?

[85rx-7gsl-se]

Its all formalities I think. Almost all cars either use a MAP or a MAF system exclusively. 2nd gens use a MAF system. 3rd Gens use a MAP system.

[RETed]

Originally Posted by Max777

Well, I know that the trap door sensor is a bit different from a "hot wire" style MAF, and that this is used for fuel on the stock ECU.

Yes, two different ways of doing this same thing.
They both measure "mass air", or the amount of air flowing into the intake / engine.

so what's different between a pressure sensor and a MAP sensor? I thought that these were the same thing, no? And if you cant have both, then why does this car have both systems?

Good question...
IN GENERAL:
A "pressure sensor" can only see pressure or positive pressure relative to "0 atmospheric (pressure).
A "MAP sensor" (remember, "MAP" stands for "manifold absolute pressure") senses both pressure *and* vacuum.
The "absolute" part means it ignores "relative to 0 atmospheric (pressure)".
What this means is that MAP sensors start at "absolute vacuum" or very near that level - this is it's zero point.
(Absolute vacuum is considered 30.0inHg or "-14.7psi" - most people don't like seeing "-" and "psi", but it's easier to explain this way.)
At sea level or "0 atmospheric pressure", a MAP sensor will actually "see" ~14.7psi.
http://wiki.xtronics.com/index.php/P...nversion_Table

Now, in the FC's case, Mazda does call the non-turbo FC's pressure sensor a...well, "pressure sensor".
The turbo FC's pressure sensor is called a "boost sensor".
That just confuses the whole issue. :P
This the learned, the non-turbo FC pressure sensor is actually a "1-bar MAP sensor" (reads vacuum up to "0" atmosphere); the turbo FC pressure is actually a "2-bar MAP sensor" (reads vacuum up to ~15psi of boost).

I mean, a "pressure sensor" is fundamentaly the same thing as a MAP sensor, they both sense pressure, or am I totally missing something?

Yes, in a sense.
I hope the above clears things up.


-Ted

[RETed]

Originally Posted by 85rx-7gsl-se

Its all formalities I think. Almost all cars either use a MAP or a MAF system exclusively. 2nd gens use a MAF system. 3rd Gens use a MAP system.

Not true...

Although the FC uses the air flow meter as it's primary load sensor, the pressure / boost sensor also affects both fuel and ignition timing.
More specifically, we have confirmed that for a turbo FC, changes in vacuum will change fuel delivery.
Once in positive boost, the boost sensor will primarily affect ignition timing.
The RTEK guys (Henrik) will also tell you this.
So to use the word "exclusively" is not correct in this case.

The FD does use a MAP sensor based load system.
The FD MAP sensor is some funky version that goes up to like 17psi, I think.
(Most MAP sensors are in 15psi increments.)
The FD has no idea what the actual amount / mass of air going into the engine, but it does calculate that figure by looking at the engine RPM's and MAP sensor readings (primarily).
This is why it cannot tell differences in engine VE when you start modding your engine, i.e. change intake, exhaust, engine porting, bigger turbo, etc.
To the FD stock ECU, 15psi is 15psi.


-Ted

[TitaniumTT]

It should be noted that 15psi is not 15psi in all cases. Which is the main reason a MAP based system much more sensitive to changes in airflow. Taking two extremes, the stock HT-12s vs a GT45R. @ 15psi of MAP, a GT45 will flow much more air than the HT12's. So, by bolting on a GT45 you need to re-tune a MAP based system due to the drastic change in VE. When you start to mod a stock MAP based system and you increase the effiecency of the turbo's, you change the output of the compressors slightly. 15psi may still be 15psi, but the actual flow is changing and the Lambda's are now incorrect. A MAF based system is still subject to changes in VE but much less so tan a MAP based because it is measuring the airflow through the sensor, not just how much pressure is in the manifold