# BMW Airflow Meter Swap How To (Digifant II Vehicles)



## Digiracer (May 5, 2002)

moved to the 8V FAQ Section
http://forums.vwvortex.com/zerothread?id=1019859



_Modified by Digiracer at 8:56 PM 7-13-2004_


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## AV_Dub (Apr 7, 2004)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

Very nice. and thank you!








I had a hard time wading through that MAF post to find a straight answer...


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## Jeramiah (Sep 10, 2003)

*Re: BMW Airflow Meter Swap How To (AV_Dub)*

awesome!!!!!!!!!!!!!


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## MDVDuber (Nov 20, 2002)

*Re: BMW Airflow Meter Swap How To (Jeramiah)*

Are you seeing any issues with the open element and the higher summer ambient air and engine temperatures? i.e. does it feel slower (seat of the pants) then it did back in January when cold air was plentiful?


_Modified by MDVDuber at 4:35 PM 7-14-2004_


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## Man&Golf (Oct 2, 2001)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

Hi guys........can someone tell me where I can get an AMS chip from?
i looked on their website and there was nothing for MKI's or MKII's.....
and search in out classifieds but didnt find anything.
how much do they go for?
thanks heaps. http://****************.com/smile/emthup.gif


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (MDVDuber)*



MDVDuber said:


> Are you seeing any issues with the open element and the higher summer ambient air and engine temperatures? i.e. does it feel slower (seat of the pants) then it did back in January when cold air was plentiful?
> Sure their's a difference but I feel a loss of power regardless of if it's an open element or modded air box. I live in a very humid area Cleveland, Ohio less than 10 miles from Lake Erie. The high humidity has a huge effect on power. Once the car is moving though, airbox or open element it doesn't make any difference. The gains with the BMW AFM still overshadow anything lost with an open element or a stock AFM in an airbox.
> I started just with a K&N panel filter/swiss cheesed airbox, then to a Eurosport CAI, then went back to just a K&N Panel with stock airbox w/ just the snorkel removed. I found that just the plain airbox with removed snorkel worked best but with the gains with this BMW AFM I'm never looking back.
> It was an animal back in January, all that cold dry air & slick roads it was a handlefull, you can mash the gas loafing in 3rd & just torch the tires on a roll.
> ...


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

I just updated the How To.
More info & more pics
Check it out
post any questions you have on this thread.


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## username (Mar 27, 2001)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

THANK YOU!!!!

i am totally going to try this, seeing as how i already have a mildly ported head, 260 cam, AMS chip, intake, exhaust, ABA bottom end, blah, blah, blah

btw: the AMS chip was discontinued i beleive but you can find them from time to time in the classifieds, i was lucky enough to know a guy in my club that was selling one after putting in a 1.8t http://****************.com/smile/emthup.gif


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (username)*

you're very welcome
Are you sure about the AMS Chip being discontinued?
If it's true I'd say it was just a matter of time, but I hope they're still available.
Just a suggestion, have you thought about a bigger cam?


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## username (Mar 27, 2001)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

well, there's no mention of them on their site although i'm sure i t wouldn't hurt to call...
well to be honest i _think_ that's what in there, the guy i bought it from said there was a cam in it and the idle proves it.....before and after the motor swap while it was going from the old head to the new one asked my buddy doing the work if he could identify it but he could not, other than it did not have the markings of a stock vw cam...for all i know it could be a 270.....i'm just staying conservative when it comes to saying whats in there since i'm not sure











_Modified by username at 5:26 PM 7-20-2004_


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (username)*

That's interesting because this is a common upgrade for our BMW 2.5 engines








Here's a stock 2.5 with 3.5 afm








And here it is with with 4.0bar of fuel (from 3.5bar)








GET YOUR CAR DYNOED.!! 
http://****************.com/smile/emthup.gif








Couriouse to know how it works with a 4cyl 2.L.








How much are you hopeing for?







*Sorry for the bmw content.*










_Modified by Slow1.8 at 11:50 AM 7-21-2004_


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## MDVDuber (Nov 20, 2002)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

Thanks for the reply. I'm just playing with ideas here. Have you tried the BMW AFM with a K&N in the stock box vs. K&N in the stock box and no snorkle vs the ram air set up?
Are our stock boxes too restrictive to work well with the BMW AFM?
Thanks.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

This is great info slow 1.8, thank you. http://****************.com/smile/emthup.gif 
Even on a stock 2.5 gains can be found with this mod. It looks like they found about 7 more peak horsepower & 4 more peak ft ibs of torque in this case. On the road that must feel like a chip upgrade to the driver IMO. So this says BMW sized the stock unit fairly well for this 2.5L engine. This is also reinforces why I state this must be one of your last mods.
I'm sure that revy 2.5L would scream up to 7K+ rpm if it had a nice pair of Shrick cams in it, alittle port work & a better exhaust.
I wouldn't expect much with this 3.5 L AFM on a stock 1.8L VW engine but I have alot of work done to my 2.0 Liter. 
I'm expecting alot more, the results will be more dramatic. I've picked up a heck of alot more torque than only 4 ft ibs. The torque gained is everywhere, I notice better pull from only 2,000 rpm. My engine used to run out of breath @ 5,600 rpm or so (only peaked @ 5,000 rpm on dyno in 3rd gear). Now it'll scream to the 7,000 rpm revlimit in every gear, except 5th (.80).
I can't credit all my gains to the bigger AFM, I also upped the intake piping size to 3inches. 
Did you up the intake piping size on the 2.5 Liter too? I'd think you would have to.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (MDVDuber)*


_Quote, originally posted by *MDVDuber* »_Thanks for the reply. I'm just playing with ideas here. Have you tried the BMW AFM with a K&N in the stock box vs. K&N in the stock box and no snorkle vs the ram air set up?
Are our stock boxes too restrictive to work well with the BMW AFM?
Thanks.

This BMW AFM is too big for your stock airbox, it won't fit. 
The BMW AFM is physically huge compared to the puny stock unit.
You have to use an open element.
Sell the stock airbox on Ebay. lol 
Besides, the opening in the airbox is only as big as the stock afm, meaning the larger afm will only flow as much as the stock afm using it (if it fit). What's the point?


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## MDVDuber (Nov 20, 2002)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

Cool, Thanks, I didn't realize it was that large!


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

I updated the How To again.
Pics of the BMW AFM vs the VW AFM size comparisons. 
Measurements of the Door, Inlet & Outlet in standard & metric.
Found a deal on Intake Piping too.


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

*Digiracer* Yes, I had to use a bigger intake boot and mod the air-box. It's a minumal gain but still noticable. http://****************.com/smile/emthup.gif 
I'm not using a K&N panel or cone because it's been DYNO PROVEN to
decrease HP and TQ. Mahl paper element have been proven 
to flow best with a drilled air box








Great work documenting this!







http://****************.com/smile/emthup.gif








P.S: This mod is as good as having a MAF (at least for flow) 
I'll post up a dyno of a "split-second" brand MAF on a stock 2.5
with a gain of only 5hp







http://****************.com/smile/emthup.gif (Same gain as the 3.5 AFM)




_Modified by Slow1.8 at 1:07 AM 7-22-2004_


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*


_Quote »_I'm sure that revy 2.5L would scream up to 7K+ rpm if it had a nice pair of Shrick cams in it

I wish it was twin-cam!








It's a crapy little single-cam. They do rev to 7k+ though









*Sorry for off topic*










_Modified by Slow1.8 at 1:14 AM 7-22-2004_


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## Jeramiah (Sep 10, 2003)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

Curious to know what the difference is between the Neuspeed p-flow and the BMW one? anybody know? Or is the p-flow something else not related to AFM?


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## username (Mar 27, 2001)

*Re: BMW Airflow Meter Swap How To (Jeramiah)*


_Quote, originally posted by *Jeramiah* »_Curious to know what the difference is between the Neuspeed p-flow and the BMW one? anybody know? Or is the p-flow something else not related to AFM?

the p-flow is nothing more than a cone filter in place of the airbox


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## 2002maniac (May 3, 2004)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*


_Quote, originally posted by *Slow1.8* »_*Digiracer* 
I'm not using a K&N panel or cone because it's been DYNO PROVEN to
decrease HP and TQ. Mahl paper element have been proven 
to flow best with a drilled air box








_Modified by Slow1.8 at 1:07 AM 7-22-2004_

Ive never heard this. quite interesting. Can anyone support this? any sources for Mahl filters other than the stealership? its about time to replace the filter in mine and I was planning on a K&N. More details please!


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (2002maniac)*

...Ok, here's ONE of the flow tests done. 
I'll see if I can dig up the one i'm talking about.
http://www.bolhuijo.com/airflowtest/index.html

We have a big air-box


















_Modified by Slow1.8 at 8:37 AM 7-22-2004_


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## MDVDuber (Nov 20, 2002)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

Very nice experiment! I think a nice next step would be to see how they flow after a bit of use. Another thought would be to see what kind of material actually gets through each type of filter, i.e which provides the best protection?
*Digiracer:* All the dryer vent hose I've seen has "ribbing" which I think would seriously effect the velocity of the airflow. Or would it create a "boundary layer" that would effectively narrow the intake? It looks like the Summit racing stuff is just fiber re-inforced plastic tubing. Do you have a part number for it? Does the Sears stuff not have the standard ribbing?
How did you secure the AFM to the car?

_Modified by MDVDuber at 9:20 AM 7-22-2004_


_Modified by MDVDuber at 9:23 AM 7-22-2004_


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (MDVDuber)*

*Digiracer:* All the dryer vent hose I've seen has "ribbing" which I think would seriously effect the velocity of the airflow. Or would it create a "boundary layer" that would effectively narrow the intake? It looks like the Summit racing stuff is just fiber re-inforced plastic tubing. Do you have a part number for it? Does the Sears stuff not have the standard ribbing?
How did you secure the AFM to the car?
Sure this probably affects ultimate air flow potential but hey, it's still 3inch piping. (It's still blowing the stock setup out of the water)
The Summit Racing Stuff can be seen on my setup in the pic, it's metal tubing, it looks stainless. 
Most flexible tubing you find is going to have some ribs in it. (This allows for flexiblilty) 
Even the stock rubber VW peice is ribbed. The Sears Tubing is identical to the Summit Stuff at only $2.50 a foot.
The stuff you see in the picture is clear Vinyl PVC Hose.
I ordered some from WYNN Enviromental Sales Inc.
It's actually used for air filtration systems & saw dust removal.
I'm going to give it a try with my CAI setup to see how well it holds up.
It comes in 10 ft sections for only $33 http://****************.com/smile/emthup.gif (I couldn't go wrong)
Let me know if you find some internally smoother/higher flowing tubing.
Right now, this is kind of on a grass roots level. I've yet to find a good place that makes dedicated intake tubing that doesn't cost a million bucks a foot.
One way you can do this.
Go to a custom muffler shop & have them fab you up an intake with mandrel bent 3inch exhaust piping. http://****************.com/smile/emthup.gif 
Another way is to use PCV pipe.
How did I secure the AFM?
At first, with nothing then I noticed it did move too far over, during hard cornering.
So I just used a big zip tie to keep it secure. Problem solved


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## MDVDuber (Nov 20, 2002)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

Thanks, Just so you know, I'm not trying to put down your ideas or effort, I think this is an incredible development and think it's great that you are so willing to share it with us and help us to work it out in our cars.








I'll keep my eyes open for some smooth walled tubing http://****************.com/smile/emthup.gif


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (MDVDuber)*


_Quote, originally posted by *MDVDuber* »_Thanks, Just so you know, I'm not trying to put down your ideas or effort, I think this is an incredible development and think it's great that you are so willing to share it with us and help us to work it out in our cars.








I'll keep my eyes open for some smooth walled tubing http://****************.com/smile/emthup.gif 

It's cool man, I'm just trying to share the knowledge or atleast get the knowledge out. It's people that don't share that hold us all back.
Hey & thanks for looking out on the tubing.








I want this How To, to be as complete & as up to date as possible. 
If anyone has any questions, suggestions, links, hookups on any of the materials needed for this project let me know.


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (Digiracer)*


_Quote, originally posted by *Digiracer* »_
It's cool man, I'm just trying to share the knowledge or atleast get the knowledge out. It's people that don't share that hold us all back.
Hey & thanks for looking out on the tubing.








I want this How To, to be as complete & as up to date as possible. 
If anyone has any questions, suggestions, links, hookups on any of the materials needed for this project let me know.

I found this earlier, and it proved to be educating and discomforting at the same time.
http://frwilk.com/944dme/afm.htm
Sorry, it was the wrong link. Fixed.



_Modified by 91driver at 11:22 AM 7-23-2004_


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## Danbodia (Sep 3, 2003)

*Re: BMW Airflow Meter Swap How To (91driver)*

maf and afm are two different things.


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (Danbodia)*

How identical are the MAF between the 328 or 535 and DigII? Doe anyone have both so that we can have a comparison between electrical readings at different points. Digiracer, do you have the BOSCH book on fuel systems? I've heard that it is mostly a physics related precision technical reference, but maybe this will help in understanding these systems better. I really don't like the possibility that my system could be learned out at WOT or any other point. I will be picking up the exact same AFM as Digracer in the next week or so. What does the stock BMW air box look like?


_Modified by 91driver at 11:27 AM 7-23-2004_


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (91driver)*

Here's a picture of the air-box from one of my junkyard hunts.

















_Quote »_How identical are the MAF between the 328 or 535 and DigII?

What do you mean? 328? 535? digi2 and Maf?


_Modified by Slow1.8 at 6:59 AM 7-24-2004_


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*


_Quote, originally posted by *Slow1.8* »_
What do you mean? 328? 535? digi2 and Maf?


I mean I'm a dumbass and kep typing MAF instead of AFM.
Are the resistors in the meter the same in Digi II as they are in the 2.8? If so, is there a difference between the 2.8L and the 3.5L AFM resistors? I'm trying to guarge the compatibility between the three. My guess (and hope) is that they are all the same. If there are variations between the three, there may be flaws with this swap. I doubt that there is a difference as this would increase cost for Bosch. My only other worry is adjusting the spring tension and any effect this may have. I'll try and figure out a way to monitor the range of movement as the car is actually driving and also at WOT. Any ideas on how to physically measure/reference spring tension of a stock digi so that the 3.5 can be adjusted to match the tension of a stock digi unit? Of course this dosn't matter as long as the resistors don't match, that is unless they are swappable. 
My .02 at this time.


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## Slow1.8 (Oct 9, 2003)

*Re: BMW Airflow Meter Swap How To (91driver)*

I've never looked at a digi afm.. don't know..









The only way to get the 3.5 meter to work right with my 2.7 was to swap in the 2.5 guts. Real easy to do.


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

Nice, I saw the screws and figured it was swappable. Now onto the spring tension. I hear that there is a shop near me that does flow testing, but I think a rough comparison can be done more easily.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (Slow1.8)*

Thank you for posting this BMW AFM/Junkyard pic Slow1.8.
Did you snag that BMW AFM after you snapped it? (I hope you did, with it & a few more goodies your 1.8 won't be slow for much longer







)
Note: in the pic you'll see the underside of the BMW AFM, it's mounted right on the valve cover, see 91Driver?








Regarding swapping out the AFM guts, what for?
This has been covered to death in the MAF Discussion.
http://forums.vwvortex.com/zerothread?id=1052915
It works, I don't have any lean issues, the resistance values are identical to stock. I run an Air/Fuel Ratio Gauge. I hit spikes as high as 13.8 in lambda mode & as high as 13.2 in WOT mode. This is the AMS Program dictating the A/F ratio not the AFM. 
The ECU, AMS or not will compensate for additional air to maintain it's preprogramed A/F maps.


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

http://forums.vwvortex.com/zerothread?id=1052915<----the next hour of my life


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## racingvw92 (Apr 17, 2003)

*Re: BMW Airflow Meter Swap How To (Digiracer)*


_Quote, originally posted by *Digiracer* »_ I run an Air/Fuel Ratio Gauge. I hit spikes as high as 13.8 in lambda mode & as high as 13.2 in WOT mode. 

The lambda scale is based on a scale of 1 being neutral, 0.8 is about where you would want to be to make the most HP, and thats a little rich. What your talking about is AFR, where 12.4 AFR is equal to 0.8 lambda. 13.8 AFR is close to running lean, be careful.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (racingvw92)*


_Quote, originally posted by *racingvw92* »_
The lambda scale is based on a scale of 1 being neutral, 0.8 is about where you would want to be to make the most HP, and thats a little rich. What your talking about is AFR, where 12.4 AFR is equal to 0.8 lambda. 13.8 AFR is close to running lean, be careful.

These Digifant II cars typically run very lean, around 14.7:1 in Lambda mode & maybe 14.2 in WOT mode.
13.8:1 is fine & 13.2 is great @ WOT Sure I'd love to be closer to 12 but I didn't program the chip lol


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## racingvw92 (Apr 17, 2003)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

Alright, just wanted to make sure. http://****************.com/smile/emthup.gif


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## username (Mar 27, 2001)

*Re: BMW Airflow Meter Swap How To (racingvw92)*

ok, i just wanted to send this up now that i've got a line on an AFM.....


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## Tattoo Collector (Jul 23, 2003)

*Re: BMW Airflow Meter Swap How To (username)*

OK. Just to be sure..we are talking about the air meter that is bolted into the airbox on our cars, right? Here's why I ask. My buddy is big into XR4TI's and his air meter is the same as ours. It is the same size, layout and has the same connectors. The only difference is that there is a little cone adapter on the end of theirs so that you can put the cone filter on it. I put one on my car one time and I noticed a difference in the car immediately. The car seemed like it was running pig rich. I am not sure of this b/c my car has 151000 miles on it and nothing is ever the same from moment to moment with that car. I am gonig to be putting my built ABA in within the next week or so. I will try to put that air meter back in once that engine is in and I'll try to get some dyno numbers for everyone. I am assuming that it would be telling it to give the car more fuel than usual b/c the XR is a factory turbo car. I know one of the upgrades for that is to use the air meter from an SVO for some more power, so maybe that is an even further upgrade I can check in to.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (Digiracer)*

The BMW Airflow Meter Swap How To has been updated & revised w/ some more info, links & afew pics.
Just to let you know








If anyone has completed this swap or needs some help/advice feel free to IM me or email me.
I'd like to tally how many people have done this sofar. 8 & 16 valves
Tattoo Collector
Good idea on the SVO AFM.
what's the deal on that SVO AFM?
I wonder if it shares a similar part # & size to the BMW AFM.
Looking on Ebay I noticed the older (1990) Porsche 911's also breathed through this type of Bosch AFM. It's gotta be larger than the 944 unit. I wonder if the 911 AFM is larger than the BMW 3.5 L. AFM?


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## 91driver (Feb 25, 2004)

*Re: BMW Airflow Meter Swap How To (91driver)*


_Quote, originally posted by *91driver* »_
I found this earlier, and it proved to be educating and discomforting at the same time.
http://frwilk.com/944dme/afm.htm
Sorry, it was the wrong link. Fixed.

_Modified by 91driver at 11:22 AM 7-23-2004_

To quote myself earlier, you should really check ou this link digiracer if you haven't already. Interesting stuff. I myself aquired the BMW AFM as soon as this subject came about. I consider myself lucky that I found one so close and so easy. On another note, I've started getting hardcore into riding my bikes again soooo.....what BMW sensor sitting in the garage? I atually need to have someone set my idle a/f this week and am going to pass for now on experimenting with the AFM. I havent read the entire original BMW thread from a while back, so I'm going to have to do that and maybe compare the resistor tracks between units, maybe switching them entirely. I just got the car running super smooth, so I'm a tad reluctant to jeopardize that. I'm not running any other mods, except the cat I will be putting back in this week after the adjustment







. I'm sure i'll get the hankering for more as soon as I'm driving it every day, but until then, research.


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## Digiracer (May 5, 2002)

*Re: BMW Airflow Meter Swap How To (91driver)*

Yes I have read this before & it is very informative, thank you.
In your quote you said, 
"I found this earlier, and it proved to be educating and discomforting at the same time."
I found it very educating aswell, it just taught me a better way to test the Potentiometer Range with a 9 volt battery for example.
So explain to us all why it's so "discomforting".
It's almost as if you read this one link & took as the holy grail of AFMS & decided to punk out on the BMW AFM Swap.








One of the things I made very clear at the beginning of the How To Thread was that this mod is not for stock vehicles. 
Here's the quote, 
"The Point: Significant increases in Horsepower & Torque throughout the entire rev range. I'll have some dyno numbers soon. If you're serious about big horsepower and you've done everything else (cam, intake, chip, exhaust) this is the next step. If you didn't catch that, this should be done last."


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## blackrack (Feb 14, 2003)

*Re: BMW Airflow Meter Swap How To (91driver)*

what have you guys found out about adjustable FPR's from http://forums.vwvortex.com/zerothread?id=1523014
which one is the easiest fit. etc


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