:::RHMT::: Real Home Made Turbo
General Category => Engine Management => Topic started by: PhilStubbs on November 17, 2011, 03:14:48 PM
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I did some reading when I first got my 07 SI saying that the factory tune was rich and that hondata gained power by leaning it a little and lowering the vtec point to make their universal reflash. I have been thinking about playing with the intake diameter to try to get the same leaning. Has anyone tried doing the same thing? The exhaust on the car is black, it's 100% stock with the standard IHE. I figure I can hook up my wideband and keep increasing the tube size where the MAF sensor is till I'm happy.
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Problem that you will find is as you start to increase tube dia. it will not be a linear amount of leaning out. You might find it will run great up top but be really lean down low due to the fact there is not enough air moving past the wire to let the computer know whats up. I remember I tested one of the first 4.6 3v turbonetics kits and it placed the stock maf in a 4" dia. tube and it ran like total ass till the maf got enough airflow to gather an accurate reading. I brought it to there attention and newer kits are a blowthru type still using the factory credit card maf.
Not knowing exactly how large you have to go but I think you might find it hard to get the exact dia. tube you need.
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I was thinking about that where part throttle might suck but wide open would be good. Right now, part throttle has issues in a couple spots but it's very minor. If I was tuning it I would fix it, but I don't have flash pro and don't really want to spend the cash when I have no plans to do any more modding to the car.
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Problem that you will find is as you start to increase tube dia. it will not be a linear amount of leaning out.
The change in flow is a function of the cross-sectional area, and therefore linear. The manner in which the air tumbles at low flow skews the way the MAF sensor reads, introducing uncertainty, and that changes for every permutation of intake tract. There are also some harmonics taking place that skew the way a MAF works, as well.
You see, your problem is that you ASSume the factory MAF curve is correct in the first place, which it is very much NOT. Fords apply half their fuel trims towards a MAF trim in order to learn the MAF, when you changed shit up it not only had the *wrong* MAF curve (despite whatever you were using to spoof the stock curve), but likely the learned MAF trim stacked on top of it.
It's kinda wierd you use a 3V example, 110% of those cars kits come with something to reflash the ECU that raise a bunch of max fuel pulsewidth limitations in the code. Kinda hard to do one right without directly editing the ECU for the changes made.
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I'm not expecting to work magic or anything. My main goal is a little better mpg, cleaner exhaust and if I gain some power in the process then that's cool too. I also want to get rid of this random low rpm, high load issue. I wish I could just tune the damn thing with Crome, I could have everything I wanted then. Flash pro is just too damn expensive when the current boot ons are all the car will ever get.
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This is like tossing on a B&M command flow and leaning out an integra. You're just doing it with air. If your entire tune is rich, it will be okay. You'll also be running a bit more timing though, since it's reading off a different load cell rather than just dumping less air.
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I'll pull plugs too. I have tuned tons of map cars, but never really messed with MAF cars except fixing them. We will see what happens. I think the current intake is 2.5", I have a 3" tube I'm gonna try.
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This is like tossing on a 4 bar MAP sensor and leaning out an integra.
Fixed.
Bigger sampling tube bigger metering capacity kthxbai
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The MAF sensor is small, it seems like a lot of air would get passed it without it reading it. Of course this is all just theory in my head since I have no real experience.
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The MAF doesn't read every molecule, it reads a sample of the whole and presumes the rest of the tube is flowing the same. Enlarge the tube and that sample moves slower/less air for the same overall CFM's.
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The MAF doesn't read every molecule, it reads a sample of the whole and presumes the rest of the tube is flowing the same. Enlarge the tube and that sample moves slower/less air for the same overall CFM's.
Or exactly what i said in my first post. And going from 2.5 to 3" is a HUGE change
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The MAF doesn't read every molecule, it reads a sample of the whole and presumes the rest of the tube is flowing the same. Enlarge the tube and that sample moves slower/less air for the same overall CFM's.
Or exactly what i said in my first post. And going from 2.5 to 3" is a HUGE change
Dear sir,
Where is my money.
And Fuck you. :)
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The MAF doesn't read every molecule, it reads a sample of the whole and presumes the rest of the tube is flowing the same. Enlarge the tube and that sample moves slower/less air for the same overall CFM's.
Or exactly what i said in my first post. And going from 2.5 to 3" is a HUGE change
Not really. 2.5" to 4" sampling tube, maybe.
Compressing the first seven volts of a hotwire's output to five volts is a HUGE change.