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View Full Version : Way to get around the MAF and have 2 airfilters



bradc
11-09-2005, 08:29 PM
As everyone knows the stock MAF makes it impossible to have 2 air filters that each go to a turbo because all the incoming air has to go through it. I'm quite keen to get all the tubing done before I get an ECU, but then the intake would have to be redone to get the 2 air filters, each hooked up straight to a turbo.

I don't want to have that small tube coming from the MAF to the front turbo at all because it is just so small.

Then an idea suddenly occured to me, why does the MAF need to be just after the air filter? Why couldn't it be after the intercooler, just before the throttle body?

This way the MAF is in a straight piece of pipe that can easily be ripped out when I change ECU's, and the turbos don't have any restriction on their intake side. The MAF is also closer to the throttle body which should mean that the air it is sensing is not delayed at all, whereas I would imagine that in the standard setup there is a bit of a delay from when the air is measured in the MAF to when it actually enters the throttle body.

Thoughts? Would the MAF be screwed up by the heated air coming in to it after the intercooler? That is the only problem I can think of.

psbarham
11-09-2005, 08:35 PM
would it be able to cope with the presure ? normally it works on negative pressure , whereas if it is mounted after the turbos it is in a positive pressure area

AllBeItMine
11-09-2005, 08:53 PM
no - wont work after the turbos. its called a MAF for a reason. Mass Air FLOW. not Mass Air Pressure.

bradc
12-09-2005, 12:09 AM
ahh ok, worth a shot anyway ;)

bradc
12-09-2005, 12:10 AM
thinking about it some more then, how does the ECU cope with a change in the ambient air pressure?

Kenneth
12-09-2005, 12:56 AM
it has a barometric adjustment signal that comes from the MAF. not sure exactly how it goes about it, but it is used to adjust the mixture.


I have an idea which I want to try. Just need some time and a couple of MAFs (need 3 in total for the testing and calibration)

It goes like this:
Calibrate the 3 MAF sensors so they show the same (or as close as possible) frequency at various air flows.

Install all 3 MAF sensors. 1 in the original location, the other 2 split off eithier before or after.
Work out the relationship between the frequencies on the split MAF sensors to the original.
Apply the relationship to the signals (ie: add both together) and send to the ECU

you then run dual intake with 1 MAF sensor on each intake.

I have most of the gear to do this, I just need a couple of MAF sensors for initial testing.

bradc
12-09-2005, 03:34 AM
Ask You See if he has his MAF sensor still from his ECU work, and when I get an ECU I'll be keen to give you mine as well (after I get the mag wheel to you!)

Kenneth
12-09-2005, 04:02 AM
Ask You See if he has his MAF sensor still from his ECU work, and when I get an ECU I'll be keen to give you mine as well (after I get the mag wheel to you!)

Ill have to wait and see what is happening with my car, then ill get back to you.

ako
12-09-2005, 05:13 AM
The stock AFM / MAF isn't a restriction at anything under 500hp. The evo boys have proved this over and over.

Just make new piping after it :) Its not exactly hard work.

The one big thing to remember is that the ECU will ALWAYS be holding you back. Rhys (-legnumvr4- ) made up new pipework, put on an intercooler, and the exhaust work... That alone has limited his car to around 10 - 11 psi before the fuel cut comes in.

Do the ECU FIRST - you'd be amazed what these things can do once you take away the factory safeguards.

One other idea - go to a MAP ECU, its a NZ made device. It lets you run AFM - less (or go open turbo inlets for the most flow possible), and sends a signal to your ECU that it can understand. It also doubles as an AFC, so you kill two birds with one stone, just costs a bit less than a full ECU.

bradc
12-09-2005, 05:57 AM
The main reason I want to do it is so that I can have proper 2 or 2.25" piping from the air filter to the turbo, the current pipe is very small and restrictive as Rhys knows.

If you are changing the ECU, then I figure you might as well take full advantage of it.

You See
12-09-2005, 06:06 AM
Ask You See if he has his MAF sensor still from his ECU work, and when I get an ECU I'll be keen to give you mine as well (after I get the mag wheel to you!)
Don't think I've still got it....most of the crap was trashed. I'll see what I can salvage.

ako
12-09-2005, 06:56 AM
The main reason I want to do it is so that I can have proper 2 or 2.25" piping from the air filter to the turbo, the current pipe is very small and restrictive as Rhys knows.

If you are changing the ECU, then I figure you might as well take full advantage of it.

Yeah, you can still quite happily do that with the MAF still in place. Just get a Y pipe after it.... No need to stuff round with wiring or anything, just make the pipes.

bradc
12-09-2005, 07:56 AM
It would be quite difficult though. I think that putting the MAF where the battery is would be an ok option, have the air filter down in the front bumper somewhere.

zentac
12-09-2005, 09:18 AM
what you need to do is convert to a MAP and do away with the MAF all together.

AllBeItMine
12-09-2005, 09:09 PM
he's going to get an aftermarket ECU and that will run off MAP anyway.

jaimz
12-09-2005, 09:45 PM
Brad,
Be careful putting your filters too far down in the engine bay. You don't want water splashing up into them when it's raining... /Hmmm

bradc
12-09-2005, 10:32 PM
I will get an ECU anyway, but this is just a concept that might help out.

Jaimz, I've thought about that, remember the water still needs to go all the way up to the engine bay anyway, what does it matter if the water goes up a tube, then gets to the airfilter, or the other way around?

Kenneth
12-09-2005, 10:48 PM
I will get an ECU anyway, but this is just a concept that might help out.

Jaimz, I've thought about that, remember the water still needs to go all the way up to the engine bay anyway, what does it matter if the water goes up a tube, then gets to the airfilter, or the other way around?

If you get enough water into your cylinders your engine will hydraulic. goodbye engine. I don't know what it would do to your turbos, but it cant be good!

If your intake is low and you go over a large puddle of water, you can immerse the intake in water. im not even sure if you need to immerse it to hydraulic.

anyway, hopefully you get the gist. imagine trying to compress a cylinder full of water... even half full

Louis
12-09-2005, 11:25 PM
Once the engine is running it is sucking air in, you hit a puddle and it sucks the water up the pipe straight into the engine, (bad news).
Anyhoo! Don't Skylines run with two air filters, and two maf sensors, one to each turbo?, (back three and front three, straight six engine). I know a guy who uses two 350z maf sensors on his skyline engine.

Kenneth
12-09-2005, 11:33 PM
yeah, at least the GTRs do. When I was in England, the guy I was staying with was repairing a R34 GTR Vspec...

jaimz
13-09-2005, 03:10 AM
That's right. If the engine weren't sucking in so much air due to the turbos it might be safer. I wouldn't go there dude.
I agree with ako. If the tiny pipe to the front turbo is the main concern, then do some custom pipework. By the way - shouldn't the pipe to the rear turbo be the same diameter...? Would seem weird to me if it weren't...

bradc
13-09-2005, 08:11 AM
The pipe to the front turbo is definately smaller and more restrictive than the pipe to the rear turbo.

The intake will still be ~200mm from the ground, I'm sure it will be fine, I never ever drive through water anyway ;)

AllBeItMine
13-09-2005, 09:14 PM
i still dont understand why you are going to do it.

you say you are going to do the "Ground work" first. but if you mess around with these pipes to both go through the AFM, you will be throwing away that work later when you do get the autronic...

bradc
13-09-2005, 09:22 PM
Yeah I know, but I'm allowed to change my mind too :D

I'm now contemplating spending about $10k all at once and getting everything done, I don't really know exactly what I'm going to do. My engine should be here in the next few days, so I'll start on the throttle body and inlet manifold soon.

jaimz
13-09-2005, 09:58 PM
Crikey dude, new engine!!? 10k!!?
You must have some serious plans for the thing! /yes
What are they..?

bradc
13-09-2005, 10:26 PM
the engine was scored for $300 from trademe, it is seized, but I don't care, I'm going to take it's cams, throttle body, intake manifold, and get those worked on, and heaps more stuff too :D

TTV6VR4
14-09-2005, 12:57 AM
Can you just set it up so you have the intake pipe and then a POD filter on the end, no AFM anywhere. I see the GTR's with the big single turbos with a intake and 2 POD filters and no sign of an AFM anywhere. Where would be the AFM on this?:

jaimz
14-09-2005, 05:26 AM
Great stuff Brad!
Make sure you post LOTS of pickys. :-)

bradc
14-09-2005, 06:39 AM
You need to have the MAF if you don't have an aftermarket computer. In that picture I guess the MAF might be hidden under the tube coming up from the intercooler.

TTV6VR4
14-09-2005, 09:46 PM
So if you have an aftermarket computer, you don't need the MAF?

AllBeItMine
15-09-2005, 09:22 AM
some cars ECU's run off Air Flow Sensors - some cars ECU's run of Air Pressure Sensors. and the same can be said for Aftermarket ECU's

In some cases, an aftermarket ECU can be tuned to run of MAF OR MAP.

but you need *something* to tell the ECU how much fuel is going into the engine - it can't guess.

jaimz
15-09-2005, 08:35 PM
If I was an after market ECU, I'd use the force.