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Discussion Starter · #1 ·
alrighty lets break it down and get technical for a min. since there is no MAf with the ms, i am going to hvae to do something special for the fuel maps when the imrc opens...

IE at 4k with the imrc closed at 10'' the ms will think its getting the same as at 4k with the imrc open at 10''.

before when the imrc opened, the maf read more flowage. but since im using a map sensor, im giong to have to do something different..

does anyone know how much more air/flow goes in with the imrc open
 

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he is referring to the standalone fuel computer known as megasquirt. when the "intake manifold runner control" activates, it opens a valve, and lets more air in. but i believe that manifold vaccum should decrease when this happens, and the ms code can be set to accomodate this. have you tried it yet? i say set it rich then tune back from there....
 

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Discussion Starter · #4 ·
i did some more thining about it. i dont think it makes more air go in, i think it just makes it easier for the air to get in the cylinders. the ms can control the imrc by its self.. with its 2 rpm switches.. i think ill try running the normal map all the way thru with the imrc open at the normal time and see what happens. if the o2 reading is off, the ms will compensate and ill change the map for more or less fuel.i think the ms is one of the most badass things ive dealt with so far.
 

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Flyguyeddy said:
he is referring to the standalone fuel computer known as megasquirt. when the "intake manifold runner control" activates, it opens a valve, and lets more air in. but i believe that manifold vaccum should decrease when this happens, and the ms code can be set to accomodate this. have you tried it yet? i say set it rich then tune back from there....
I know what a mega squirt is. I've had a SDS EMS and now a Haltech E6K EMS. I just don't under stand what he is talking about or trying to say.
 

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Discussion Starter · #6 ·
with the intake runners closed(1.9 mode) the fuel curve would stay somewhat str8. but with the intake runners open(spi mode), its letting more air in. more air requires more fuel..right?

the question was... how much more fuel does the motor require when the intake runners are open... if any at all?
 

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MAF>MAP :p


The MAP will see see the same value any time the throttle body is all the way open, does'nt matter if your flowing more air with the IMRC open or less air with the IMRC closed. This is why I like MAF's, it can actully see the volume of air entering the motor instead of just a vacuume reading that requires a look up table with other varible's thrown in the mix.

Can the MS be changed to a MAF and the software reprogramed to recalculate the air flow signal?
 

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Discussion Starter · #8 ·
Jeffescortlx said:
Can the MS be changed to a MAF and the software reprogramed to recalculate the air flow signal?
im not sure. since the map is built in to the actual unit,, it might be hard. i dont have the funding to experiment with it either. im already into deep with this project anyway.

so u dont think the fuel map will(should)change when the imrc is open?
 

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yes it should. more air=more fuel. the first port is for high velocity low volume low end tourque. the other one is for high volume low velocity air movement. so, you get more air coming in.

am i preaching to already informed masses?

if i am, please dont take it as an insult....
 

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marclar said:
Jeffescortlx said:
Can the MS be changed to a MAF and the software reprogramed to recalculate the air flow signal?
so u dont think the fuel map will(should)change when the imrc is open?
Yes the fuel map will need to change, other wise you'll run a good AFR with it closed and a lean AFR with it open, or the other way around depending on the tune.

You could allway's program the MS to open the IMRC and than at the same time have the cruve take a jump richer?

MAF's own! They dont need a RPM look up table. X amount of air flow = X amount of fuel, end of story. :p
 

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What variables determine whether or not the IMRC opens or closes?

The further you can place the vaccuum port from the runners, the more accurate the reading will be.

The IMRC should only change the amount of vaccuum (and the intake air velocity) within the runners. The air in the open plenum should be in accordance with the total amount of air that's being injested. The IMRC (if working properly) should be maximizing the amount of air going into the cylinders.. so even when it's closed.. it's letting in more air (than it would if it were open under those conditions). That's just the nature of the system.


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MAFs are great under most situations. When you've got a highly turbocharged small displacement engine, a MAF needs to be large enough to not restrict the full power potential, yet small enough to be sensitive to idle and narrow throttle inputs. Also, a MAF only works on ambient air pulled thru it from a vacuum. You cannot use a MAF to measure boosted air.
 

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marclar said:
with the intake runners closed(1.9 mode) the fuel curve would stay somewhat str8. but with the intake runners open(spi mode), its letting more air in. more air requires more fuel..right?

the question was... how much more fuel does the motor require when the intake runners are open... if any at all?
Oh, this is a LX thing...
 

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Discussion Starter · #13 ·
definately an "LX thing"


you can use MAF's for "blow thru". this i have found is the most efficient way to use MAF;s with boost. the "draw thru" always gave me trouble.

the MS has 2 rpm activated switches that can be set to any rpm.i am going to have it open the imrc at about 3300, with a 2ohm resistor.
 

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Beaverboy said:
MAFs are great under most situations. When you've got a highly turbocharged small displacement engine, a MAF needs to be large enough to not restrict the full power potential, yet small enough to be sensitive to idle and narrow throttle inputs. Also, a MAF only works on ambient air pulled thru it from a vacuum. You cannot use a MAF to measure boosted air.
In most of the I4 MAF turbo'd car's I see, the MAF's are larger than the throttle bodys, so there should'nt really be an issue with the MAF being the restriced part of the system.

This does bring up a interesting point: A MAF can not measure the boost in the intake manifold like a MAP can. But, what is "Boost"- It's just a measurement of how much back pressure there is in the intake manifold from inbetween the runner's/head with the turbo pushing on the other side of the throttle body.
With just the "psi" reading (MAP), that is not enough info to figure out how much fuel is needed to be injected to make that perfect AFR. That is where the look up table comes into play, it looks at the RPM and manifold pressure and picks a number off the table to find out the amount of fuel. Just knowing the psi doesnt tell you the volume of air being taken in, just the pressure of it.
While a MAF on the other hand, can see the total amount of air the motor is taking in. No need for a "pretuned" look up table to make that perfect AFR.
 

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Discussion Starter · #15 ·
there are ups and downs of using a maf/map. if only we could make them work in partnership with eachother....to make the most precise fuel map

but we still need to figure out how much more fuel ill need in spi mode..
 

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marclar said:
there are ups and downs of using a maf/map. if only we could make them work in partnership with eachother....to make the most precise fuel map

but we still need to figure out how much more fuel ill need in spi mode..
Make a MAF work, then you wont need to figure it out, it will figure it out for you. :p
 

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You'll have two parts to the fuel map from what I understand while reading the MegaManual. One part will be the MAP pressure and the other will be engine RPM. So, just make sure that when you hit the IMRC crossover point, reguardless of MAP pressure, that you just enrich the fuel curve a little. If memory serves the table looks somewhat like this.

VE table where the fuel requirement is expressed in Volumetric Efficiency (VE) %

MAP kPa {some number}
--------{10}.. [VE%]. [VE%]. [VE%] .[VE%]. [VE%] .[VE%]. [VE%]. [VE%]. [VE%] .[VE%] .[VE%]
--------{20}.. [VE%]. [VE%]. [VE%]. [VE%] .[VE%] .[VE%]. [VE%]. [VE%] .[VE%] .[VE%] .[VE%]
--------{30}.. [VE%]. [VE%]. [VE%]. [VE%]. [VE%]. [VE%] .[VE%] .[VE%]. [VE%] .[VE%] .[VE%]
--------{40}.. [VE%] .[VE%]. [VE%]. [VE%] .[VE%] .[VE%]. [VE%] .[VE%]. [VE%] .[VE%]. [VE%]
--------{50}.. [VE%]. [VE%]. [VE%]. [VE%]. [VE%]. [VE%] .[VE%] .[VE%]. [VE%] .[VE%] .[VE%]
--------{60}.. [VE%]. [VE%]. [VE%]. [VE%]. [VE%]. [VE%] .[VE%]. [VE%] .[VE%] .[VE%] .[VE%]
--------{70}.. [VE%]. [VE%]. [VE%]. [VE%]. [VE%] .[VE%]. [VE%]. [VE%] .[VE%] .[VE%]. [VE%]
--------{80}.. [VE%]. [VE%] .[VE%]. [VE%] .[VE%] .[VE%]. [VE%] .[VE%] .[VE%] .[VE%] .[VE%]
--------{90}.. [VE%]. [VE%]. [VE%]. [VE%] .[VE%]. [VE%] .[VE%] .[VE%]. [VE%] .[VE%]. [VE%]
--------{100} [VE%]. [VE%]. [VE%]. [VE%]. [VE%]. [VE%] .[VE%]. [VE%]. [VE%] .[VE%] .[VE%]
---------------{1000}{1500}{2000}{2500}{3000}{3500}{4000}{4500}{5000}{5500}{6000}
--------------------------------------Engine RPM
 

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Onegimp said:
Make a WOT run, data log it. Adjust lean spots.
Maybe after a halfway tune and a couple of lower speed runs. Don't want to blow it right off the bat. :wink:
 
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