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Tuning for 3" MAF housing

6K views 43 replies 7 participants last post by  1turbofocus 
#1 ·
I currently have a MAFia and a stock MAF with a draw-through configuration.
I'm moving to a 3" housing and blow-through with no MAFia.
I know this will end up being a drastic change in the MAF Transfer table, which I can handle.
What I'd like is a suggestion on a starter tune for adjusting to the 3".

My thought was to reload the MTF and manifold volume back to stock, and then add 10% fuel to the MTF just to get started and see how it runs.
Perhaps load a 5%, 10% and 15% richer MTF tables into the xcal to save some time.

So my questions:
1) What can you all suggest as a starter MTF for the 3" housing?
2) What oddities should I expect to run into? (aside from leaner AFR due to lack of metering of the extra air)
3) Will any idle functions need adjusted?

All tips I'm looking for are regarding N/A tune.
However, if anyone has a suggestions for boost and 3" MAF tube I'll welcome those too.
My plan is to run with the wastegate open until the base tune is where I want it.
By then I should have enough data to make educated adjustments to the upper portion of the MTF table and start running boost again.
I should also mention my car is already tuned for 9.5psi boost with the draw-through setup.

Thanks all. [wrenchin]
 
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#9 ·
I had a 3" MAF Tube on my duratec for a while when I first started playing with the SCT PRP.

If you PM me, I can e-mail you my value files if you want. They should work better than illinipo's zetec files.

It worked OK for me, but I was still running stock cams at the time so the resolution was crappy at idle/low RPM and very hard to tune below 2000 RPM.

I ultimately settled on a 2.75" MAF.
 
#3 ·
(aside from leaner AFR due to lack of metering of the extra air)
What extra air?

Also dont forget to de-scale your injectors and engine displacement, and manifold volume if that was scaled before as well

I had no change in any idle or dashpot functions when I went 3", but you are also changing your piping configuration so there might be some tweaking to do there

When I did mine I went by the r2^2/r1^2 multiplier compared to stock which is I believe (3/2)^2/(2.16/2)^2 = 1.93, and it was WAY off I had to pull back like 25% from that.
 
#4 ·
Oh, I didn't mean literally more air, just that there will be a certain volume of air that will "escape" around the meter causing a lean condition.
Hmm I'll look into the scaling done to the injectors.
They are 55#, and Don LaSota originally did my tune.
There are values such as timing tables and injector values I have not had to change since I bought the PRP and built off his tune.
 
#5 ·
Fortunately the MAF doesnt measure volume, it mostly cares about the speed of the air going past it, which changes how much the wire gets cooled. Bigger maf tube means slower air, so you get more range on the maf. But lower resolution.
 
#6 ·
Yeah, but the whole idea of going with a larger housing is to "fool" the sensor, thus permitting a greater volume of air to get past.
 
#7 ·
Not exactly. Bigger tube means slower air velocity in the maf tube which cools the wire less. It's called a MASS airflow sensor not a volume airflow sensor.

http://en.wikipedia.org/wiki/Mass_flow_sensor#Hot_wire_sensor_.28MAF.29

Also I just realized you have a duratec. So my file will likely not even be close to what you need but it will be closer than a stock MTF.
 
#8 ·
OK, I just learned something.
That's downright embarrassing to be working on MAF vehicles for this long and even tuning and not know how a MAF actually works. [facepalm]

Not exactly. Bigger tube means slower air velocity in the maf tube which cools the wire less.

http://en.wikipedia.org/wiki/Mass_flow_sensor#Hot_wire_sensor_.28MAF.29

Also I just realized you have a duratec. So my file will likely not even be close to yours but it will be closer than a stock MTF.
 
#11 · (Edited)
I agree, if the TB is in the stock location on the stock manifold then there's no reason to use anything except the stock manifold volume parameter unless someone was trying to fudge someting in the tune...

Since he's changing the whole set-up from draw thru to blow thru, he might be changing back to a stock manifold from a custom one?
 
#12 ·
Your going to blowthrough , that changes things all in it self , blowthrough does not use the same MTF as suckthrough so you will just have to play with it

By reading what your saying about your tuning this , you need to stop get the SCT book and go over a few things so you dont hurt your engine , the MFT is some what easy in the scale of things that need to be done

Tom
 
#14 ·
Your going to blowthrough , that changes things all in it self , blowthrough does not use the same MTF as suckthrough so you will just have to play with it
I'm curious, why is that so?

I thought that since the MAF hotwire will cool off proportionately based on the density of the air etc, that having boost flowing through it versus air at near atmospheric pressures would be irrelevent?

I don't doubt you, I'm just trying to understand why....
 
#18 ·
At atmospheric pressure in the inlet pipe, the mass of air will take up more space and therefore move faster than it does in the pressurized charge pipes.

Since it is moving faster it will have a higher reynolds number and the boundary layer will be taller, making the tube effectively smaller and further increasing the velocity of the air in the inlet.
 
#19 ·
If any of you are wondering the proper way to tune your MAF transfer table. There are a few steps you should follow to make th process much easier.

1. Force the EEC to run in open loop. This makes it much easier to tune the lower voltage part of the function because the o2 sensor is not having any say over fuel.

2. Set your base fuel table to 12:1. This is your target AFR.

3. Datalog. You will need to log AFR with a wideband and you will need to log MAF voltage. TPS and RPM are fun to have but are not needed. Make sure your engine is heated up all the way before logging cause cold start enrichment will throw it off a little.

First you log the 0-2 volt part of the curve. Once the car is running and heated up and you start logging. leave it in neutral. Ease on the throttle slowly and steadily. keep increasing the throttle until you reach 2 volts or you dont want to free rev it any higher.

Once you are done the log. Then you need to tune. for example. if at 1.2 volts your afr is 14:1 and your target afr is 12:1 then you need to multiply the airflow value at 1.2 volts by 1.16. You go through all of the values from 0v to 2v in the same manner. The process may have to be repeated a few times to get it as close as possible.

Then you are ready to do some datalogs while driving for the 2v to 5v section of the transfer. You always want to ensure that you are starting in the rich side. Doing hard pulls leaner than 12:1 can get dangerous. Especially with forced induction. I find a good way to get a ballpark figure of what the transfer values should be before starting is multiply the values proportionaly to the size of the MAF upgrade.

For example. If your starting with a 60mm maf and converting to an 80mm maf then you would multiply all the values by 1.3 as a starting point.

Again, you get the engine up to operating temp. Then you find a nice open strech of road ( or a dyno). You get logging and start doing moderate pulls. I find 3rd gear works real well. You want to make sure to make slow and steady pedal movements. This helps to make nice smooth datalogs that are easy to read. Let the car slow down to the bottom slowly accelerate to the top of the gear. If you are on the rich side then it is ok to start doing some good hard pulls as long as it stays on or below 12:1afr.

Once you think you have enough clean data to tune as many data points on the curve as you can (except the high 4v area. If you get up here you still need a bigger MAF!). Then you start rebuilding your curve by multiplying the airflow values at each voltage data point relative to the amount that the logged AFR is away from your target 12:1afr. You may have to repeat this process a few times to get it perfect.

When the MAF transfer is spot on. The AFR will hold at 12:1 all the time. Idle, light cruise and WOT. The only time it should stray fronm 12:1 is when decelerating.

Once you have the MAF curve done. Then you are free to set Base Fuel table back to stock and enable closed loop fuel control. That way you can have you lean idle and cruise with input from the o2 sensor.
 
#23 ·
1. Force the EEC to run in open loop. This makes it much easier to tune the lower voltage part of the function because the o2 sensor is not having any say over fuel.
Why, when the trims tell you exactly where you need to be?

MAfs are designed to meter Mass Air flow when the air is at or near standard pressure and density. When you put your MAF in a blow through configuration after the turbocharger you are trying to make it meter air in a way it is not designed to.
If you read the wiki article I linked you will understand that it IS designed to do that.
 
#22 · (Edited)
When going with a bigger MAF you should also lower your minimum maf voltage setpoint because you will be closer to it with a larger maf at idle. It could possibly set off codes.

Another trick is to put a honeycomb air straightener out of a GM maf in your sample tube. The honeycomb out of a 3" GM maf will press fit directly into a ford 70mm sample tube. It will dramaticly clean up your maf's voltage signal and makes your MAF respond the same way regardless of positioning near bends.

MAfs are designed to meter Mass Air flow when the air is at or near standard pressure and density. When you put your MAF in a blow through configuration after the turbocharger you are trying to make it meter air in a way it is not designed to. It is much harder to tune in that configuration because of the dynamics of the environment. I always make mine draw through. It works much better for me.

Keep in mind it is only truly nessecary to upgrade your MAF when when you have reached the limit of its metering capability(4.5+ volts). If your routinely getting way up there then you should consider upgrading MAfs. I dont think the stock Zetecs will max out thier stock MAF but if your going turbo you will need at least a 70mm.
 
#29 ·
I am only going to start with #1 because I dont have the time or am I going to take it to teach you tuning

The Focus has closed loop , the closed loop function trims the fuel automaticly at idle and part throttle , change your MTF by how much the closed loop is trimming by % wise and your done

Most cases you can do idle , 2000 , 3000rpm in "N" and your about 85-90% finished with your MTF till you go open loop WOT

No forcing open loop , having to drive and having to watch AF , just log and slight changes when you return , faster , easier , let the ECU do as much of the work as you can

Tom
 
#30 ·
Ah, I see. You go about it a different way than me.

I view closed loop operation as a variable, and opt to disable it. You use it to your advantage.

Perhaps you didn't notice the end

When the MAF transfer is spot on. The AFR will hold at 12:1 all the time. Idle, light cruise and WOT. The only time it should stray fronm 12:1 is when decelerating.

Once you have the MAF curve done. Then you are free to set Base Fuel table back to stock and enable closed loop fuel control. That way you can have you lean idle and cruise with input from the o2 sensor.
Tom, It seems to me, both our stratagies have the same end result.
I agree, your way does sound easier.

My way must be old school. But hey, works great for me.
 
#31 ·
You way WONT WORK , if you set idle / cruise target in OL to 12.1 then when you go back to closed loop it targets 14.7 which is where idle and cruise should be targeting so the trim is WAY off and you still have to make adjustments to the MTF

You should never target the idle , cruise for 12`s allways 14.7 , 14.7 is stoich

Tom
 
#32 ·
Actually Tom that way does work, maybe you're just misunderstanding something in his process? If 12 is in the base table and you tune perfectly to 12 in open loop then when you go back closed loop it will be spot on 14.7. Base table is the target no matter what in open loop. And the MTF doesnt care about what afr it is targeting.

But man it is so much easier to just use the trims
 
#35 · (Edited)
Working on the tune now...
FYI, I have 55# injectors.
I took my previous tune which ran/idled fine and reset the values that were changed specifically for the MAFia (IM volume, engine displacement, FI high slope, FI low slope).
I also reloaded the MTF table back to stock, then multiplied by 1.50.
I have not fine-tuned the MTF because I haven't driven anywhere yet.

Right now the STFT is fantastic, but my idle is sputtering around 800-1000 RPMs, not drastic like there was a vac leak, but very "rough".
There is also some roughness when holding the throttle steady open.
So let's just say there's roughness across the board.

Any help appreciated.

Seems as if I've missed some injector settings or displacement/manifold adjustment somewhere.
Doesn't seem to be any vac leaks.

EDIT:

For troubleshooting purposes, here are the things I changed not dealing with the tune:
- New pipe from FMIC to throttle body: 2.5" out of IC for appx 90* and then to 3" to throttle body (2.75").
- MAF is positioned after around 10" of straight 3" pipe.
- Moved the coolant expansion tank to make room for the air filter and new ambient pipe (2.5").
- Cut off most of the bracket which the expansion tank mounted to, but maintained a section for the ground cable.
- Removed the evap canister (I believe that's what it's called) to repair a broken nipple, which was previously causing a vac leak.
- Had the turbo fitted with a larger compressor wheel and the housing machined.
 
#38 ·
Thanks Tom, you don't know how much I appreciate it.
Let me know what you'd like to see in the logs.
I probably wasn't monitoring as much as you would even though I saved my log, so I'll need to do more logging real quick.
 
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