MarkD Chip vs Miller MAF w/ Basic Chip

[James Crivellone]

Damnit, just typed up a long response and bumped the freaking back button on my mouse.. Go.. me

Anyway, I run the Miller W.A.R and 2.7inch MAF on my 2.8L M20 Stroker in my Mtech E30, and honestly it runs pretty damn good.

Even on the stock 2.5L tune it did really well. I spoke with Brody over the phone several times when I first installed it.. including the time I plugged the MAF plug in backwards and it ran like total crap... It did list that in the instructions that I didn't read.. maybe a yellow sticker on the maf saying HEY IDIOT read the instructions would be a nice touch.. or I could just read it.

Brody even sent someone down to Kirkland WA (he was working on something else as well so not just for me) to custom Dyno tune the car, got the A/F perfect and the engine runs great.

I still may go MSS54.. cough NANDO cough in the future (For the hell of it to play) however the car runs great on Miller and i have not had any support issues with Brody over the years.

I have heard of others having some problems, and it seems as if Brody is the one person to talk to at Miller to get stuff done, hopefully they figure that out as one person being the eyes and ears of a company is not the way to do it.

Truthfully the only issues I have with Miller relate to little things

1) Check engine light is ALWAYS ON, battery reset clears it for a little, but it comes back. I heard it was a Checksum issue and I figured I just need to unplug the light.. have not done that yet

2) W.A.R room.. yeah I know it got hacked, Brody if you need ANY help with that please let me know. I'd love to work with you on bringing that back. R3V can certainly lend some time and resources to helping other customers enjoy the original thought process being sharing tunes with each other. Hell my Dyno tuned 2.8L M20 tune I'm sure someone else could use.

I'm not dismissing others having issues with Miller. Its clear issues have come up, however every time i deal with Brody he is professional and helpful, perhaps Miller just needs more Brody's to help everyone out..

My

[digger]

Do you guys know how the AFM works? Just because you are full throttle doesn't mean the AFM flap is full open. The AFM outputs a 0 to 5 v signal. Until you are at maximum RPM/Flow, the flap will not be open its fullest anything less than max flow at max RPM and the flap is restricting the flow.

i don't agree with this at all. the flap is wide open well before max rpm at WOT i've seen if for myself when on the dyno and black cover off (no amount of bastardizing the spring is going to change that) and i am pretty sure i read that in the bosch fuel injection book or similar. logic says it has to be. the flow difference at WOT and low speed and rpm cruise is massive the AFM hasn't the ability to meter such huge variations in flow so there is a point where it stops metering so to speak and other means and sensors are used to determine fuel, timing inputs.

[LJ851]

Interesting note.
I'll use a yamaha R6 as an example. When it went to drive by wire they determined that keeping the throttle plate at the minimum angle to create maximum torque actually increased torque at lower rpms compared to WOT. End result is that no matter what you do to the throttle, the ecu never opens the butterfly past that ideal amount until you get past 5k rpm or so and makes more power in the process.

[brody]

i don't agree with this at all. the flap is wide open well before max rpm at WOT i've seen if for myself when on the dyno and black cover off (no amount of bastardizing the spring is going to change that) and i am pretty sure i read that in the bosch fuel injection book or similar. logic says it has to be. the flow difference at WOT and low speed and rpm cruise is massive the AFM hasn't the ability to meter such huge variations in flow so there is a point where it stops metering so to speak and other means and sensors are used to determine fuel, timing inputs.

If what you say is truly what you saw happen then you have just proven how inaccurate the AFM is. There is a reason there is a "max voltage" before fuel CUT from the afm. it's so you dont flow more air than the sensor can handle. How would you get to fuel cut? By the flap opening too far.

If you saw the afm "full open" as soon as you did, then the ECU is not measuring the air accurately. The more accurate you can get woth air metering the more power you will get. Our software uses the MAF signal at all times by measuring the flow, not guessing the flow based on other sensors.

Also the curve of the voltage output is critical. If you measured the voltage instead of looking at the afm to see if its moving, if you saw voltage still climbing, the gate is still opening more and more.

[LJ851]

The AFM gate does stop moving well before max rpm.

As far as max power is concerned, for a given ignition curve with a meter that doesn't restrict the amount of air needed by the engine to make max power, if doesn't matter if the damn thing uses smoke signals as long as the AFR's are correct.


The addition of a tuned "torque tube" intake (Miller PSIK) is another story and can boost power in parts of the overall curve.

[bmwman91]

Guys, the AFM's door is not restricting squat. Period. The engine can pull nearly a full vacuum, -14.7PSI, behind the throttle plate. Even a pin-hole sized vacuum leak messes up the idle. To suggest that the spring-loaded door in the AFM poses any restriction is laughable. The issue is the 5cm x 5cm (25cm^2) opening in the AFM's body, not the flapper door. If you found a MAF with a 5.6cm diameter ID (25cm^2), it would restrict air just the same. Actually, the outlet of the AFM is even smaller, so wherever the smallest crossection happens to be is where you'll have your restriction, and a MAF with the same crossectional area would restrict air just the same.

The IC engine is a glorified air pump. Pressure drops in the intake will inhibit its ability to pull in air. The drop we are talking about across the little flapper door is seriously like 0.1PSI. If you taped the door open in the AFM and ran max air flow through it, you would be dropping more than that across the AFM itself just because of the small opening size. Seriously, the little tiny spring that closes the door isn't a barrier to performance. You can push it open with your little finger. You can obsess over that 0.1PSI drop from the door, which is sucking 0.7% of your engine's power away, or you can save up for an extrude-honed manifold and a porting job which will get you many whole percent more power.

Here's a thought experiment for you.
Install an M30 AFM or the Miller MAF setup so that those send the load signal to the ECU. Then put the stock AFM on the intake tube, not hooked up or anything. Get on a dyno and test these two scenarios:
- Stock AFM in place with door free to move
- Stock AFM in place with some scotch tape holding the door all the way open

Which one makes more power? If you think that a piece of scotch tape can buy you multiple horsepower, then I have a bridge to sell you.

Also, I have the actual Bosch data sheets for a bunch of AFMs and MAFs. The M20B25 AFM can handle 450m^3/hr (265CFM) at 90% of output voltage. Presumably it can go higher, but Bosch doesn't guarantee accuracy above that. The M30B35 AFM can handle 620CMH (365CFM) at 90% output, and it has a 29cm^2 inlet section. Better than the M20's, but still more restrictive than a 7cm ID MAF (38.5cm^2). The pressure drop across the sensors will increase with increasing air flow, but the MAF will be less restrictive simply because it has a lot more open flow area.

----------------------

Digger, you aren't quite right about how the ECU deals with the sensors' inputs at WOT. When at WOT, the ECU stops reading the O2 sensor and uses only the AFM as its load input (open loop operation). The AFM is the single most important piece of the ECU's load calculation from which the injector duty cycles are derived. As I have been stressing above, it just doesn't matter if the flap door is open all the way or not.

[digger]

If what you say is truly what you saw happen then you have just proven how inaccurate the AFM is. There is a reason there is a "max voltage" before fuel CUT from the afm. it's so you dont flow more air than the sensor can handle. How would you get to fuel cut? By the flap opening too far.

If you saw the afm "full open" as soon as you did, then the ECU is not measuring the air accurately. The more accurate you can get woth air metering the more power you will get. Our software uses the MAF signal at all times by measuring the flow, not guessing the flow based on other sensors.

Also the curve of the voltage output is critical. If you measured the voltage instead of looking at the afm to see if its moving, if you saw voltage still climbing, the gate is still opening more and more.

once the flap is wide open the load is considered 100% the TPS would also be at WOT position so the fuel and timing is determined by WOT map which is basically temp and rpm.

if on the stock car the flap magically is open exactly 100% at WOT and peak power rpm lets call it 6k, then on a modified car it would open alot sooner maybe 5k and what would happen? the sky would fall down.

im not saying the MAf isnt better

[digger]

Guys, the AFM's door is not restricting squat. Period. The engine can pull nearly a full vacuum, -14.7PSI, behind the throttle plate. Even a pin-hole sized vacuum leak messes up the idle. To suggest that the spring-loaded door in the AFM poses any restriction is laughable. The issue is the 5cm x 5cm (25cm^2) opening in the AFM's body, not the flapper door. If you found a MAF with a 5.6cm diameter ID (25cm^2), it would restrict air just the same. Actually, the outlet of the AFM is even smaller, so wherever the smallest crossection happens to be is where you'll have your restriction, and a MAF with the same crossectional area would restrict air just the same.

The IC engine is a glorified air pump. Pressure drops in the intake will inhibit its ability to pull in air. The drop we are talking about across the little flapper door is seriously like 0.1PSI. If you taped the door open in the AFM and ran max air flow through it, you would be dropping more than that across the AFM itself just because of the small opening size. Seriously, the little tiny spring that closes the door isn't a barrier to performance. You can push it open with your little finger. You can obsess over that 0.1PSI drop from the door, which is sucking 0.7% of your engine's power away, or you can save up for an extrude-honed manifold and a porting job which will get you many whole percent more power.

Here's a thought experiment for you.
Install an M30 AFM or the Miller MAF setup so that those send the load signal to the ECU. Then put the stock AFM on the intake tube, not hooked up or anything. Get on a dyno and test these two scenarios:
- Stock AFM in place with door free to move
- Stock AFM in place with some scotch tape holding the door all the way open

Which one makes more power? If you think that a piece of scotch tape can buy you multiple horsepower, then I have a bridge to sell you.

Also, I have the actual Bosch data sheets for a bunch of AFMs and MAFs. The M20B25 AFM can handle 450m^3/hr (265CFM) at 90% of output voltage. Presumably it can go higher, but Bosch doesn't guarantee accuracy above that. The M30B35 AFM can handle 620CMH (365CFM) at 90% output, and it has a 29cm^2 inlet section. Better than the M20's, but still more restrictive than a 7cm ID MAF (38.5cm^2). The pressure drop across the sensors will increase with increasing air flow, but the MAF will be less restrictive simply because it has a lot more open flow area.

----------------------

Digger, you aren't quite right about how the ECU deals with the sensors' inputs at WOT. When at WOT, the ECU stops reading the O2 sensor and uses only the AFM as its load input (open loop operation). The AFM is the single most important piece of the ECU's load calculation from which the injector duty cycles are derived. As I have been stressing above, it just doesn't matter if the flap door is open all the way or not.

seriously who cares whether its the spring loaded flap door or piss pore shape and small area? the AFM "unit" as a whole restrict things....

having done dyno tests with custom chip tuned M30AFM vs extremely half assed tune standalone it makes a big difference losing the AFM on a modded car. if the standalone had been properly tuned it would be even more gain.

i didnt even mention the O2 sensor.....of course the AFM is the load device but it does go 100% before peak power rpm and yes it doesn't matter there are other ways for the ECU to deliver the right fuel if you get the chip calibrated.

a properly setup AFM is still a pretty good thing on a healthy engine but the world has moved on for lots of reasons

[bmwman91]

Gotcha, missed the part about stand-alone. The stock ECU would have some big issues if the AFM maxed-out, but a stand-alone leaves lots of options.

The long explanation about the AFM flap door wasn't directed at you. It was more general since there still is a ton of misunderstanding about the AFM and why it is restrictive. Everyone seems to think that the flap door has something to do with it, which isn't the case. I'm with you though, in that the AFM is an old technology that really has no place given the cheaper, faster and more reliable options out there.

I am definitely skeptical about the "AFM going to 100% output voltage at WOT" thing. At least with a stock ECU. Did you actually have a volt meter on there to see it exceed 4.50V at the output terminal? Based on what I know of the Motronic, the WOT maps require accurate AFM load input and RPM to properly dictate fuel injection. This is obviously not the case for stand-alone where you can run Alpha-N or some such at WOT. Maybe there is a misunderstanding on my part about what you are saying.

Also agreed that the tune is the most important factor in all of it. You can have the most awesome hardware setup ever, but if the tune sucks then it's useless.

[digger]

The AFM gate does stop moving well before max rpm.

As far as max power is concerned, for a given ignition curve with a meter that doesn't restrict the amount of air needed by the engine to make max power, if doesn't matter if the damn thing uses smoke signals as long as the AFR's are correct.


The addition of a tuned "torque tube" intake (Miller PSIK) is another story and can boost power in parts of the overall curve.

i did some basic dyno testing of various tube lengths on my engine from a

- cone filter on the end of the TB (short pipe)
- a few feet of tube between TB and cone filter

plus a few lengths in between the short and long tube cone

I found nothing to get excited about other than the shortest length made the most top end hp from 5200rpm+ by about 3-4% hp over the longest tube but lost out below 3000rpm by slightly the less than the same amount. midrange was identical on all. the AFR showed where the flow had changed and this showed more or less hp depending if it went leaner or richer. you aren't talking alot of hp change between the different tube lengths but this style of setup will easily outperform stock airbox if you can keep the charge cool

so anyway i kept my custom bigger airbox with bigger panel filter which is better optimized for flow as it showed noticeable gains over stock. dont let anyone tell you the stock airbox is good that is BS there is some hp to be gained but if you draw hot air you will lose any flow gains and then some

your results may vary

[digger]

Gotcha, missed the part about stand-alone. The stock ECU would have some big issues if the AFM maxed-out, but a stand-alone leaves lots of options.

The long explanation about the AFM flap door wasn't directed at you. It was more general since there still is a ton of misunderstanding about the AFM and why it is restrictive. Everyone seems to think that the flap door has something to do with it, which isn't the case. I'm with you though, in that the AFM is an old technology that really has no place given the cheaper, faster and more reliable options out there.

I am definitely skeptical about the "AFM going to 100% output voltage at WOT" thing. At least with a stock ECU. Did you actually have a volt meter on there to see it exceed 4.50V at the output terminal? Based on what I know of the Motronic, the WOT maps require accurate AFM load input and RPM to properly dictate fuel injection. This is obviously not the case for stand-alone where you can run Alpha-N or some such at WOT. Maybe there is a misunderstanding on my part about what you are saying.

Also agreed that the tune is the most important factor in all of it. You can have the most awesome hardware setup ever, but if the tune sucks then it's useless.

to be honest the AFM testing on basically stock car was like 8 years ago so details are sketchy these days. LJ851 has said the same so i am confident i was not rteading things wrong. i did source a few different AFM and play around but came to the conclusion why stuff around when there are better alternatives

[digger]

Interesting note.
I'll use a yamaha R6 as an example. When it went to drive by wire they determined that keeping the throttle plate at the minimum angle to create maximum torque actually increased torque at lower rpms compared to WOT. End result is that no matter what you do to the throttle, the ecu never opens the butterfly past that ideal amount until you get past 5k rpm or so and makes more power in the process.

i've wondered about that, maybe it is something to with fuel preparation? the throttle blade and shaft on a ITB setup causes local turbulence which is good for fuel atomisation. same reason why position of an ICV on a ITB runner engine matters as you can stragically inject air to help with fuel mixing and atomisation at idle.

[bmwman91]

I was JUST thinking about the optimum distance between throttle plates and the injector. I can see a situation where you would have it too close and a stream of fast air would just blow the fuel into the port walls.

As for the AFM maxing out, maybe we'll never really know. My engine sure doesn't max it out, even with a 2.1L Metric Mechanic engine sucking on it. I'll get my MAF conversion on there someday.

How's THIS for a stock airbox retrofit? All the protection of a nice stock paper panel filter, with 60% more surface area (M42 and M20 use the same size stock filter too)

http://www.r3vlimited.com/board/showthread.php?t=291676

/thread jack

[digger]

I was JUST thinking about the optimum distance between throttle plates and the injector. I can see a situation where you would have it too close and a stream of fast air would just blow the fuel into the port walls.

As for the AFM maxing out, maybe we'll never really know. My engine sure doesn't max it out, even with a 2.1L Metric Mechanic engine sucking on it. I'll get my MAF conversion on there someday.

How's THIS for a stock airbox retrofit? All the protection of a nice stock paper panel filter, with 60% more surface area (M42 and M20 use the same size stock filter too)

http://www.r3vlimited.com/board/showthread.php?t=291676

/thread jack

nicework! i have the same M30airbox but cbf modding it so i did something different and this is the one i made, . it uses a bigger panel but not quite as big as that M30 version. i bought the top half and had to slightly mod it and made the bottom half to suit the M20

http://www.e30tech.com/forum/showthread.php?t=89097

[EatsHondas]

/thread jack

Go for it man, my original question was more than answered.