MAF sensor, relocate or not???

[bradc]

We have dyno tested a few vr-4s in NZ with pods back to back with the stock setup and the pod has always lost power. I don't beleive a 400m run is valid as there are too many variables such as wind, fuel, launch, gear changes and so on. Do it on a dyno on the same car on the same day and let me know what happens

[Turbo_Steve]

Brad, the back-to-back tests are actually LESS relevant than an on the road dash:

1) On a Dyno there is no airflow. The readings you get, Especially with a pod (which will draw in hot air at high load when the car is stationary - something it will NEVER do on the road) are usually not that accurate.

2) The Dyno tests were all pods mounted direct to the MAF. I wholeheartedly agree that this doesn't work. In some cases it works briefly, but as the filter gets dirty, the air pattern tends to change, and BAM there's your MAF misread again.

3) Nobody has tested additional stabilisation properly. Alan did it, (kudos to Alan) it wasn't sufficiently scientific to prove it decisively either way (i.e. over 10,000miles or similar, with EvoScan and mpg readings). Kiteman has also tried a similar setup, and it worked well until the filter started to get dirty - then he started to have serious fuel cut issues.

In the absence of an airbox, the MAF CAN be persuaded to read correctly - it just needs stable airflow. I think it was DaveZJ who actually came up with a really neat solution, but nobody has tested it:

A Matrix of small bore pipes glued together inside the MAF feed pipe, around 2cms long. The feed pipe needs to be at least 10cm diameter...if not more.

This is extremely similar to Alans setup, which didn't cause him any problems, or differences in fuel economy, even at higher boost.

The factory airbox is not the be-all and end-all, Brad: it's just simpler if you don't want to mess about!

[AlanDITD]

I wonder how many times this argument will come up over the years....

any way once i have the pipe back from pete i have a plan....

[bradc]

The irony is that my map sensor equipped car has a pod and a sealed air box

Ultimately though the problem of getting an air intake design that delivers the correct airflow is very hard to solve unless you do have a full set of monitoring tools and use evoscan to compare maf hz figures a wideband and so on.

[Turbo_Steve]

Strictly speak, all you need is EvoScan and a flat bit of ground a couple of miles long.
Do a hard pull on one setup, quickly swap it to another and try again.

Plot MAF output against time on both pulls, and analyse the difference...

[bradc]

You also need to have a wideband to see if your first run was spot on or not to know if your next run which may have higher or lower maf hz numbers is 'better' or 'worse'.

[Turbo_Steve]

All the wideband will tell you is what fuelling the ECU thinks it needs for the reading the MAF has already given you, brad?

You could, I suppose, compare the wideband against the known contents of the factory ECU to see if you're hitting the target AFR for that load point, but as far as I can recall it's all just "9" anyway so if you see anything other than 9.....the Hz graph should show it by miles!

[AlanDITD]

Is this how your current car looks now brad?

http://www.clubvr4.com/forum/vbpicga...?do=big&p=1584

I know your running map and there feeding the turbos directly, just looks pretty good, is it pods in the box?

[bradc]

Yep, thats how it has been Alan since the ECU was installed. There is just one big pod in there sealed onto those two pipes. It works well with a big hole cut in through the battery tray

Steve, true but I still think it is important to have on hand.

[AlanDITD]

Yeah man looks sweet, there any vids of your car 0-60's etc

Off topic just havent seen it before really

[bradc]

http://www.clubvr4.com/forum/showthr...light=vids+car

[AlanDITD]

hmm not bad....very good for the gear its in...need some launches and 0-180s though

[Turbo_Steve]

Steve, true but I still think it is important to have on hand.

But what for - if it's JUST EvoScan, then it's likely that any number of people may be able to have a go at trying some different things. If they need a wideband as well, they're likely to be put off....and it's not going to tell them anything!

EvoScan has knock monitoring, so the risks are non-existant anyway - What is it that the Wideband is going to tell you other than Rich....Still Rich....still really Rich.....

[1timeVR4]

http://www.clubvr4.com/forum/vbpicga...?do=big&p=1584


This is very similiar to what im looking to do, create a stainless airbox in place of the battery and extend the air inlet pipe.


Thanks for the link alan, good pic to reference from


Its also day to day performance im interested in, Ive only done a 1/4 mile once and that was years ago in a 406 turbo. Where I live top speeds up and down the bypass are more important......

[bradc]

Steve, true but it will be able to tell you if you've gone from 10.4 to 10.7 for example somewhere in the middle of the range. If you are going the other way then you know you are really doing it wrong!

[Turbo_Steve]

Actually, going to have to disagree again! (Sorry). If you're making an inlet that flows better, the ECU is going to see more airflow = more load = running richer.

All the AFR does is tell you how much load the ECU thinks the MAF is seeing. Which is what EvoScan tells you.... it's all in the chart, trust me!

The shape of the curve should be broadly the same, but chances are the better flow will result in it being moved towards the Y axis slightly more.