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Discussion Starter · #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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Token Engin-nerd
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PM me your email I can send you a value file with my 3" maf data to start you off
 

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(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.
 

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Discussion Starter · #4 ·
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.
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.
 

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Token Engin-nerd
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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.
 

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Discussion Starter · #6 ·
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.
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.
 

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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.
 

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Discussion Starter · #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.
 

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PM me your email I can send you a value file with my 3" maf data to start you off
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.
 

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There is no need to change th intake volume either

Tom
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?
 

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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
 

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There is no need to change th intake volume either

Tom
A lot of people scale manifold volume when they do the mafia scaling so I was saying he should reset that to stock if it is changed.
 

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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....
 

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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....
While you have the theory right, reality doesnt always match the books.

Theres also a lot of difference due to the filter turbulence in drawthrough vs nice straight tubing in blowthrough

Plus with a higher reynolds number due to higher velocity in drawthrough, the boundary layer will be higher off the tube wall, effectively making the tube even smaller and making the air go even faster.
 

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While you have the theory right, reality doesnt always match the books.

Theres also a lot of difference due to the filter turbulence in drawthrough vs nice straight tubing in blowthrough

Plus with a higher reynolds number due to higher velocity in drawthrough, the boundary layer will be higher off the tube wall, effectively making the tube even smaller and making the air go even faster.
OK, that makes sense.

While the basic theory is correct, there are mittigating circumstances and other theories that ultimately dictate what goes on in the MAF tube

Thanks for helping me understand that. I can get a full night's rest now....[thumb]
 

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While you have the theory right, reality doesnt always match the books.

Theres also a lot of difference due to the filter turbulence in drawthrough vs nice straight tubing in blowthrough

Plus with a higher reynolds number due to higher velocity in drawthrough, the boundary layer will be higher off the tube wall, effectively making the tube even smaller and making the air go even faster.
I dont buy all of that , the boundry layer will only be higher IF it is effected by placement of a turn before or after the MAF , If there is enough distance this wouldnt hold true , I dont feel it makes the tube seem smaller or that the air is moving any faster through the tubes then with suckthrough but all of this will depend on how the piping is made , amount of turns , distance from MAF to the closest turns

Tom
 

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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.
 

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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.
 
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