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406 Posts
Discussion Starter #1
Gentleman Drivers,

Recently I installed a Miller 3rd gen MAF & WAR chip combo in my E28 M5. I thought I'd describe the install and a few bumps I found along the road. Miller's instruction manual is good, but little bit dated now and some of the installation is different than described.

I'll break up the install into a few different categories since the installation covers a few different areas of the car.
-MAF Installation
-WAR chip Installation
-Wiring modification
-Programing the WAR chip
-Things I didn't know before the project began
-Initial impressions

Below is what Arrived after a decent wait (ordered in August, arrived in early November) as Miller apparently is having a hard time with production keeping up with demand. I think there are worse situations in this world than too much demand!
-Miller WAR chip (quality piece!)
-Millers custom 4" MAF that plugs straight into the old AFM plug.
-4" to 3" silicone reducer made specifically for the gap between the MAF air plenum.

DSC_7534 by ericandshovin, on Flickr

The old bits before the tools come out.

DSC_7535 by ericandshovin, on Flickr

MAF Installation:
Removing the airbox and AFM is quite simple. Undo two hose clamps, remove the plug connecting the AFM to the engine harness, and undo a 10mm nut on the right side of the airbox. The most difficult part of removing the airbo/AFM is the coolant return lines get in the way a bit. You can wiggle around them, or just remove the hose connected to the coolant reservoir to gain more access. I am terrible at installing those push lock hose clamps, therefore I elected to wiggle the whole assembly around the small coolant lines.

Once you remove the airbox & open it up, you can see exactly what the S38 breathes through in stock form.

DSC_7540 by ericandshovin, on Flickr

I didn't want to just go buck-wild with a grinder, so I made a little template using a sharpie and an old document envelope to trace out the MAF. This type of cardboard is thin enough to easily cut, but stiff enough to keep it's form. Cereal boxes work well for templates too.

IMG_3506 by ericandshovin, on Flickr

Cut out with a razor blade, and compared to the AFM's gasket.

DSC_7541 by ericandshovin, on Flickr

Comparing the template to the original opening it becomes clear that the new MAF is significantly larger than the OE AFM. The internet can argue until it's blue in the face whether or not the S38 should have a 4" MAF or a smaller one. I'm not an engineer and have not studied fluid dynamics so I'll reserve judgment.

DSC_7542 by ericandshovin, on Flickr

After the initial cut using a dremel, I was a bit conservative, so a little bit more needed to be trimmed. To cut the metal I used the cutoff wheel to remove a bulk of the metal, and the "561 Multipurpose Cutting Tool" to trim it down to size making sure I kept my fingers well clear of the spinning digit shredder.

DSC_7544 by ericandshovin, on Flickr

Once the big hole was cut, I drilled 3 new holes for the bolts to secure the MAF to the airbox, and made a quick trip to Lowe's to grab some new M6 nuts and bolts that were the correct length. Lowes/Home Depot's metric selection is usually quite terrible, but in this instance they had some nice black bolts with washers already attached in the "automotive" drawer. To me, this makes the install look more OEM and draw less attention.

To seal the MAF to the airbox, I used a bit of black permatex gasket maker and bolted it all together letting it sit overnight. I have a 1 year old and a 4 year old so my garage time is usually pretty limited.

IMG_3258 by ericandshovin, on Flickr

The next afternoon I put a new BMW air filter in the airbox and got to work sticking it all back together. The neat-o silicone tube is much much stiffer than the rubber boot it replaces, so putting the airbox + MAF + tube was nearly impossible. I found that if you shoved the 4" side as far up the MAF as possible (past the moulded in stops) it helped tremendously. To get the 3" side onto the air plenum I did my best shoving & twisting the tube onto the intake opening until most of it was on. Then I pulled out my harbor freight dental pics and started pulling and prodding the last bit of the silicone tube onto the air plenum. It was not simple since the silicone is so stiff, but with a bit of determination, It finally slipped on.

I was a bit short on pictures for the installation, but here is the finished product. Also, notice the coolant temp sensor hanging off the side of the radiator. If you get too rough with wedging the airbox back in it's spot, this can crack the radiator resulting in an expensive mistake.

DSC_7598 by ericandshovin, on Flickr

Now the astute reader might notice that the plug for the MAF is on the opposite side compared to the AFM plug. As you can see below, there is not enough cable to easily connect the MAF to the factory harness. Pulled very tight it will physically connect, but I do not trust it as a long term solution.

DSC_7600 by ericandshovin, on Flickr

So a trip to the U-Pull-N-Pay junkyard was in order, and I came up with these guys from a donor E30 325iC. The pin layout for the AFM on the M20/M30/S14/S38 is all the same, so a few snips, a couple of screws removed and my extension cable idea was becoming a reality. As a side note, I found it sad that there was only 1 80's vintage BMW in the lot. 5 years ago old BMW's in yards was much more popular.

DSC_7546 by ericandshovin, on Flickr

A bit more of Dremel "561 Multi Cutting Tool" trimmed down the AFM side connector, a terrible attempt at soldering, and some harbor freight heat shrink resulted in this little beauty.

DSC_7603 by ericandshovin, on Flickr

And here is the final product tucked in nice an happy.

DSC_7604 by ericandshovin, on Flickr

WAR Chip Installation
Moving on to replacing the factory 28 pin e-prom that controls fuel & timing tables with the sophisticated WAR processor. This process is no harder than replacing the factory chip with a Mark D or Conforti chip, but it does have a few extra steps that isn't needed with a conventional chip replacement .

The WAR chip is not specific to the S38 or any other engine like a normal performance chip would be. To make the chip unique to your motor, you must load tunes onto it using the supplied USB cable and software provided by Miller (more on that later). You can load the tunes either before or after the chip is installed in the ECU.

Pulling the ECU is pretty straight forward. Open the glove box, remove the leather flap to expose the ECU. Remove the four 10mm bolts holding the ECU to the dash, and disconnect the wire harness by pushing on the silver metal tab on the firewall side of the ECU (grab a flashlight if you cannot feel it).

Once the ECU is out of the car, use a small flat head screw driver to pry the 10 tabs up.

DSC_7569 by ericandshovin, on Flickr

Once I get them up a bit, I use a set of needle nose pliers to pull them straight up. You can accomplish the same results with just the screwdriver, but this is easier. Caution that the tabs aren't bent too far back as they can break easily.

DSC_7570 by ericandshovin, on Flickr

The circuit board is visible once the cover is removed and you can see that it is actually two separate boards with a bit of ribbon cabling connecting the two. The chip is on the top board, so separating the boards is the next step. No need to remove any screws, just pop the little plastic stanchions on either side of the ribbon cable. Place your fingers on either side of the stanchion and gently apply pressure up and down evenly until it pops, then move to the next one. Being delicate here is important since these parts are NLA.


DSC_7575 by ericandshovin, on Flickr


DSC_7576 by ericandshovin, on Flickr

Next, you need to depress the two tabs holding the circuit board up against the black plastic connector housing. Here you can see the tabs after the circuit board has been removed.

DSC_7578 by ericandshovin, on Flickr

These are the tabs before removing the circuit board. To release them, use your flathead screwdriver and depress one while simultaneously gently prying the edge of the circuit board away from the black plastic connector housing. This is where a third hand comes in handy.... While maintaining enough pressure to prevent the tab from snapping back into it's place, depress the other tab and gently pry the other side of the circuit board.

DSC_7595 by ericandshovin, on Flickr

Once both tabs have been depressed pull the circuit board away from the black plastic connector housing to reveal the guts of your ECU! As you can see my car was already running the Jim Conforti/Turner Performance chip. A solid upgrade in it's own right and much better than the Dinan chip that was previously in the car.

DSC_7579 by ericandshovin, on Flickr

Gently pry the chip out of it's socket taking care not to bend any pins. Then place the Miller WAR chip in the old chips place. There is a 1/2 circle notch on the WAR chip that needs to be lined up with the 1/2 circle detent on 28 pin receptacle. Both the notch and the detent are visible in the picture below

DSC_7585 by ericandshovin, on Flickr

Now your war chip is installed! At this point you can either button everything back up (basic reverse of disassembly) and the WAR chip will function like the chip you just replaced running solely on the default map (we'll get into that later) or you can hook up the cables to truly get the maximum potential out of the WAR chip.

DSC_7586 by ericandshovin, on Flickr

Two cables accompany the WAR chip. A USB cable that allows you to hook a Windows XP laptop up to the chip and a TCM (Tune-Control-Module) knob that allows you to select 4 different tunes. Plug the cables into the designated ports on the WAR chip as shown below.


DSC_7587 by ericandshovin, on Flickr


DSC_7588 by ericandshovin, on Flickr

Together (playing around with my 50mm 1.4 lens...)

DSC_7589 by ericandshovin, on Flickr

However these cables do no good if they are not accessible. To be able to actually use them, you need to drill a hole in the side of the metal ECU case. Another trip to Lowe's netted these nice rubber grommets to keep the wiring from chaffing on the metal case. Miller sells a grommet for about a buck which is probably a better piece than my Lowe's one.

DSC_7592 by ericandshovin, on Flickr

I chose to drill the hole in the back of the case as that seamed like a less congested area of the circuit boards. Routing the wires in the most direct configuration didn't look that good to me as it would be resting on different components that more than likely get quite hot. Once I drilled out the hole to the appropriate size, installation of the circuit board and case was a simple reversal of disassembly. The extra wiring made it slightly more cumbersome but not difficult.

Wiring modification
The final piece of the puzzle before you can put it all back together involves a bit of soldering. It is not difficult, but does require permanent modification to the wire harness. Take your time reading Miller instruction manual and double checking that you are cutting/modifying the correct wires!

The large connector that the ECU plugs into needs to be modified a little bit to ensure the MAF talks to the ECU correctly. Millers directions work well here, but their pictures are from a different car.

To remove the cover and expose the wire harness, first remove the small screw at the end of the harness, then clip the zip ties at the back of the harness where the plastic cover meets the factory electrical tape. 223,000 miles of use made my tape a bit stubborn and I had to persuade it with a box cutter to free up the plastic cover.
Once the cover is free you need to slide it away from the harness and the pin-out area. I put my flathead screwdriver in the gap between the pin-out and the cover and pry'd it apart a little bit. Below you can see the opening that is created as the cover starts to slide.

DSC_7555 by ericandshovin, on Flickr

Slowly work the cover off until it slides completely off.

Once you have removed the cover you need to locate two cables. One is located at pin 9 and the other is pin 35. Miller specifies multiple times that the wire color is often what they described, but not always. My S38 powered M5 was exactly as they described.

Pin 9 is usually a grey/white wire

DSC_7558 by ericandshovin, on Flickr

And pin 35 is red/blue (note, another wire nearby looks similar but is blue/red so ensure you get the correct one!).

DSC_7568 by ericandshovin, on Flickr

After you locate the wires highlighted above, cut the wire that belongs to pin 9 and connect it to the wire that belongs to pin 35. I used a t-joint and a crimp connector to make the wiring modification because I plan to dyno tune the car in a month or so. During the dyno session I plan on reverting the car back to stock to see if there is a measurable difference between stock/Miller MAF/custom dyno tuned Miller MAF.

DSC_7567 by ericandshovin, on Flickr

The above method works, but is FAR to bulky to allow the plastic cover be re-installed and I will be soldering this connection together after the dyno session has happened.

Once you have finished the solder job and taped up the new joint, put everything back the way you found it ensuring none of the wiring becomes pinched as you put the cover back on. Reconnect and reinstall the ECU as this part is finished!

Programing the WAR chip
I am not a huge computer person. Not to say that my googlefu isn't impressive, I'm just not that great with software anomaly resolutions. Once I acquired a laptop and installing the appropriate programs, I was able to pull up Millers software program and create my own chip.

I set the ECU type to the S38's 079, and loaded 4 tunes. Miller has a few video's tutorials that explain how to program the chip as well as how to modify it. I'd highly recommend you watch their vids as it really helps out!

Things I didn't know before the project began
I thought I had done my due diligence before beginning this project, and although I read the S38/M88 installation instructions on Millers site & many articles on forums; I still found a few things that bothered me a little bit with the kit.

-Miller states, "You may need to trim the opening to get the full 4” benefits."
--Trimming is an understatement! So much of the airbox was cut away, I will no longer be able to use it if I wanted to revert back to the stock AFM. If for some reason I ever want to go back to stock, I will need to purchase another airbox.

-Millers MAF instructions show an older (I'm assuming GEN II) normal looking chip in their S38 instruction manual. You must read the Miller WAR instructions for WAR specific instructions.
--It would have been nice if the MAF installation guide reference the WAR instruction PDF for the users that are installing the WAR chip instead of the regular GEN III chip. I thought I had read up on everything pertinent, but I missed a pretty big chunk of useful information!

-Handy links that I wish I had found earlier
S38 MAF install: M88&S38 MAF instruction manual GENIII.pdf
-WAR chip install: Chip - Manual.pdf
-Software tutorials (very helpful to me): WAR Chip Tech Videos

-Windows XP computer (laptop) required.
--Since I did not read the WAR instruction PDF until day 3 (kids take up a lot of time) I did not know that only XP computers could be used with Millers proprietary software. I've been virus free on a macbook for the last 4 years, so I was a bit bummed that I'd need to start hunting down an old laptop on craigslist instead of testing out the M5 later that evening. Luckily a co-worker had an old laptop that soon became mine for a delightful $15.

-Java is required
-- If you have recently acquired a co-workers laptop, make sure you have Java installed. Millers software does not work without it...

-MAF plug wrong side.
--I'm sure Miller uses the same MAF for multiple applications, but having to make an extension plug is a bit annoying. An E30 M3 friend of mine says he needed to make the same thing for his install.

Initial impressions
I've driven the car exactly twice since installing the MAF and the car feels pretty good. I don't notice a gigantic increase in power over the AFM/Jim C combo but throttle response does feel quicker. This could be all in my head too, but RPM's seam to fall quicker when lifting.

Currently it's cold here in Colorado, and the car starts and idles nicely with no indication that your running anything other than OEM components. A few of the tunes I have tried out had problems with very small throttle inputs. An example is driving at 50mph with the cruise control on and the grade of the road increases slightly. The car stumbles for a bit before regaining composure. Or at idle, a blip of the throttle causes the RPM to drop and engine stumbles. One of the tunes runs fine, and I haven't messed with the others since.

I'll continue to add to this review as I drive the car more, hopefully with a bit of track time later this month, and a dyno session before the year is over.

601 Posts
I had no idea anything like this was available for e28 M5's!! Good show! Looking forward to hearing some measured results!

Also, are you selling your JC chip? Which iteration of the chip do you have?

10,449 Posts
Nice write up!
Regarding the mafs wiring, why not just rotate the mafs 180 degrees, so the connector is on the bottom, but facing the right way? Wouldn't that work?

939 Posts
Nice write up!
Regarding the mafs wiring, why not just rotate the mafs 180 degrees, so the connector is on the bottom, but facing the right way? Wouldn't that work?
I think the airflow direction would then be wrong for the MAF - see pic with the directional arrow stamped on the new MAF.

406 Posts
Discussion Starter #10 (Edited)
Any dyno tune updates on this???
Reading back through old threads, I now realize that I never posted my Dyno results! I wrote this little article for our local chapters newsletter. Either I never finished it, or it got lost in an editor shuffle... not sure which, but none the less, it's cheesy and your free to read it or scroll to the dyne plot at the bottom!

Making old new again.

New is nice. New food is almost always better than left overs (except spaghetti for some reason). New clothes get worn while the old duds sink to the bottom of the dresser. My newish MacBook is ages better than the 10 year old laptop it replaced. So why then do new cars come and go in my life but old ones seem to stick around for the long haul? I've wondered this many many times in years past. Our MINI Clubman was fantastic, doing everything our growing family could possibly need from it. The GTi before it was also lovely. The F11 530d I drove extensively in europe was exquisite... nothing better than cruising at 220kph with the fuel economy of a Prius.

My 1988 M5 turned 26 in November, hardly new, and if you measure car years similar to cat years, this old girl should be in the golden age of her life. I don't drive the M5 every day, but every time I sink behind the wheel, my bond with the Garching creation grows deeper. This summer I was lucky enough to take the M5 to Monterey for the 45th annual BMW CCA Oktoberfest, and one of the many great things to happen at this event was experiencing the M5's powerplant at sea level. Oh. My. Goodness. Experts say your loos 3% for every 1,000 feet of altitude. The seat of my pants tell me that the S38B35 is much more responsive and lively at 10 feet above sea level than Colorado Springs 6,035 feet above sea level.

Since returning to the mountains, I've been craving the power I felt ripping around Laguna Seca and carving a few lonely backroads in the coastal mountains. To do this, I decided to add some new technology by way of Miller Performances MAF conversion and custom dyno tune from MAC Autosport in Parker CO. The M5 and most BMW's built in the 80's came with an air flow meter (AFM). This is basically a barn door that is spring loaded shut. Engine vacuum sucks the door open and a potentiometer at the top of the door measures how much the door has moved. The more it opens, the more fuel is given. The boys at Miller take the AFM and chuck it in the trash, replacing it with a giant 4" mass airflow meter (MAF), and a new eprom called the W.A.R. chip. Most cars up to 1996 can benefit from the W.A.R. chip custom tuning ability.

The MAF/W.A.R. chip install was pretty straightforward. only a bit of airbox trimming and 1 wire rerouting were needed. After installing the Miller setup, I honestly didn't feel much performance difference over the factory AFM with a Jim Conforti chip installed. The motor ran well, but still felt a bit lethargic and lazy. Luckily the front range is blessed to have a great tuner in their backyard. MAC Autosport has a AWD Dynojet dynamometer able to handle anything under 1800hp and their tuner, Nick, is a bit of a BMW gear-head. He currently owns a 400 something horsepower turbocharged E34 535i and another turbocharged S50 swapped E30 that is even more ridiculous!

One run on the Dyno showed that the Miller supplied tune was very rich which was affecting a smooth power band. Still the S38 lay'd down a respectable 220whp & 215 torque. Nick quickly got to work adjust parameters in both the fuel & timing cells. Soon the M5 was consistently making around 227whp but was making an odd fuel dump blip at 5,500rpm. They dyno plot showed at 10whp drop at this rpm when the air fuel ratio dipped. A bit more fine tuning smoothed out the rich fuel problem and netted an extra few ponies. The M5 was now making 234whp and 226 torque.

Nick explained that the older generations of 8-bit fuel injection are much more difficult to tune than current 32-bit technology. I relate this to playing Mario Bro's on Nintendo vs. Call of Duty on PS3. He is able to reflash the E46 M3's Seimens MSS54 ECU and has seen 16whp gains! This is more than plug & play flash's most popular companies are offering and if it's anything like my M5's gains, the area under the curve gets a big boost.

Our final step was to see what the motor makes completely stock. For this I borrowed a factory airbox, AFM and ECU from club member Tom Schultz. His E28 M5 is tucked away for the winter, so this was a perfect time to do a baseline run using his parts! Completely stock, the M5 made 211rwhp & 209 torque. For rear wheel drive cars, Nick uses a 19% drivetrain and altitude loss to convert the rear wheel horsepower numbers to crank horsepower. Factoring in the drivetrain loss, my 222,332mi M5 made 252hp, only 4hp shy of factory specifications! With the new technology and wizardry of MAC Autosport, my M5 now runs a healthy 278hp!

Screen Shot 2014-12-28 at 6.48.07 AM by ericandshovin, on Flickr

and a vid!

601 Posts
Great numbers!! How does she feel on the butt dyno compared to JC or Dinan?

406 Posts
Discussion Starter #15
First post here goes; any progress on this?

Just bought a E28 M5, and this seems interesting.
Hi Lupoz,

I recently sold my M5 and only put a few miles on it with the new motor setup. My motor eventually had: Enlarged air filter box, Miller MAF, 4" (100mm) silicone pipeing, 4" airbox inlet (pictured above), Fresh top end rebuild, B36 intake cam, slotted and custom tuned cam gears, M88 headers, Frank Fahey midpipe, Stebro exhaust.

I can't say specifically how much HP the larger inlet made, but seat of my pants... the car pulled so much better! It revved just a bit slower than an S54 and was just a joy to drive.

If you want to enlarge your airbox inlet, I'd be happy to do it for you for the cost of materials. I was really happy with the refinish job my friend sourced, I could help you with that as well if your interested. No sales pitch here, just happy to help if you'd like!


21 Posts
Hi Lupoz,

I recently sold my M5 and only put a few miles on it with the new motor setup. My motor eventually had: Enlarged air filter box, Miller MAF, 4" (100mm) silicone pipeing, 4" airbox inlet (pictured above), Fresh top end rebuild, B36 intake cam, slotted and custom tuned cam gears, M88 headers, Frank Fahey midpipe, Stebro exhaust.

I can't say specifically how much HP the larger inlet made, but seat of my pants... the car pulled so much better! It revved just a bit slower than an S54 and was just a joy to drive.

If you want to enlarge your airbox inlet, I'd be happy to do it for you for the cost of materials. I was really happy with the refinish job my friend sourced, I could help you with that as well if your interested. No sales pitch here, just happy to help if you'd like!
Okay cool, thanks for the added info. Shipping the airbox to colorado from denmark might be a bit excessive, especially since i can TIG myself :)
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