Inexpensive power upgrades for the 325i/iS/iX motor

**Mystikal** · 06-21-2005, 12:02 PM

Thought I'd compile a list of cheap M20B25 HP upgrades, all in USD for a good frame of reference:

Injectors: Factory injectors are barely adequate to even feed a stock motor when they're new, chances are they aren't feeding enough fuel above 5500 any more. You will want to upgrade your injectors before doing any other upgrades. Any other worthwhile modification will max out your stock pieces and be theoretically useless. Cheap replacements include stock pieces from an M50/S50 motor (E36 2.5 and 3.0, rated 17.5lb/hr) and Ford V8 (Mustang/Crown Vic/etc, rated 19lb/hr). Either set will do the same thing, but using the M50/S50 ones is a little easier because they are all Design II type, meaning the fuel sprays out of 4 pintles instead of 1. Better atomization.
Price: Typically go used for anywhere from $30-80, good idea to get them flow matched and rebuilt afterwards ($25/ea typically).
Installation Difficulty: 3/5 (you need to get dirty for this).

Chip: Because the motor was designed to run on 87 octane, there is a lot of potential in aftermarket software programming that is designed to use 91 and above. Good quality chips not only improve maximum power, they change throttle response at all openings and result in a smoother, more responsive feel. Reputable tuners include Jim Conforti (also labeled under Turner Motorsports) and Mark D'Sylva (MarkD, EAT, Ultrachip). Jim's software requires 91 octane, while Mark has two versions, one that requires 91 and a more aggressive chip that needs 93. Back to back comparison tests have been performed between the JimC and MarkD 93, and the MarkD software had a distinct power advantage. MarkD's website
Price: $249 for JC, $199 for MarkD (91 or 93).
Installation Difficulty: 2/5 (don't bend the pins!).

M30 AFM: The stock AFM is a known bottle-neck of the induction system, to the point where improving flow north of it (read: upgrading to a CAI or running no filter at all) doesn't improve power at all. The M30 AFM is larger and allows better airflow, and is worth about 5hp up top. You will want to use an AFM ending with the part number ending in 027, this one is plug and play with the M20 electronics. You can use the stock M20 airbox if you heat it up a bit to stretch it over the slightly larger M30 port, or you can get a 3" K&N cone filter and slap that on for bling and a cool sound (get a heatshield if you don't want to lose power). Keep in mind, after this mod is done.. the throttle body becomes your next intake bottle-neck. EMPOWERD can bore the stock one out (PM him) or with some modding, you can replace the M20 one with the larger M30 body. Dave Adams did a full write up on the AFM upgrade, here. In case the link goes down, here is the dyno graph hosted on my server.
Price: $30-80 for the "027" M30 AFM, $25-45 for a K&N cone (optional)
Installation Difficulty: 1/5 if you get a K&N cone to mount, 2/5 if you want to use the stock airbox.

Any comments or suggestions for additions, post them up and I'll consider adding them to the list. For now, these are tried and true upgrades that provide solid gains for little dough.

BMW BMXer · 06-21-2005, 12:40 PM

Oh so etas just get the shaft eh?

Woofer · 06-21-2005, 06:45 PM

lol no eta's are special thats y bmw bmxer. Our cars are too cool for mods

lol

Axxe · 06-29-2005, 07:51 PM

Quote:

Originally Posted by Woofer

lol no eta's are special thats y bmw bmxer. Our cars are too cool for mods

lol

Haha, special enough for second gear clutch dumping? ROFLMAO, still laughing at all the "dorifto" styles you have

wyze · 06-30-2005, 12:12 PM

hmm can't forget nitrous oxide

got a zex kit for about 400 can

and while running a 50 shot didn't need to make any mods to the car

King Luis · 06-30-2005, 08:30 PM

now for the AFM upgrade....do you need to get a fuel regulator and all that stuff like dave adams did? or is the plug and play literitly plug and play?

bmwm5lover · 07-01-2005, 01:53 PM

Luis, it is just plug and play. You stretch the rubber boot over the bigger AFM opening, move the little gear inside(on top) to tune it to your liking, and you are ready for some fun.

rwh11385 · 08-21-2005, 04:52 AM

um, Jay. Tell Mark good damn call on the M50 injectors. Like sex. More torque and a lot smoother than the 19# injectors, and better mpg. (but buying cleaned and flow-tested ones helped too)

I'll post something about it when I get back to school tommorrow. Lime > Lemonade injectors.

**Mystikal** · 08-22-2005, 12:28 PM

Quote:

Originally Posted by rwh11385

um, Jay. Tell Mark good damn call on the M50 injectors. Like sex. More torque and a lot smoother than the 19# injectors, and better mpg. (but buying cleaned and flow-tested ones helped too)

I'll post something about it when I get back to school tommorrow. Lime > Lemonade injectors.

Was it Mark that first put the 17.5 idea on the table? I remember it was Stu McHenry who really convinced me to stay away from the Mustang sprayers, but Mark may have said something at the dyno. Sadly I never got my S50 injectors flow tested, but they had an actual 40k on them and all the rings looked brand new, so I took the chance.

BTW I have two 027 AFMs sitting here now, will be dyno testing them against the M20 piece in the next few weeks. FWIW neither one worked smoothly without any wheel adjustment (one set off the check engine light, one just runs horribly), and I refuse to open them up unless I have a wideband connected. In reality, adjusting an AFM without an exhaust sniffer is pretty sketchy. For now I'm back to the M20 AFM.

e30_kid89 · 01-18-2006, 09:41 PM

wha about da m42?would i b able to go with a bigger injector upgrade?

ZiMMie · 04-27-2006, 10:45 PM

anyone thinking of gettin an intake for thier car should read this.

http://www.bolhuijo.com/airflowtest/

Derek89E30 · 05-30-2006, 08:17 AM

Quote:

Originally Posted by bmwm5lover

Luis, it is just plug and play. You stretch the rubber boot over the bigger AFM opening, move the little gear inside(on top) to tune it to your liking, and you are ready for some fun.

Hey guys, im in the process of doing the AFM conversion...what does this little gear you speak of do? does it somehow adjust the flow through the AFM?

In daves write up, he uses a 3" aluminum tube to connect the AFM to the throttle body...is this nessecary to do, or can you position the AFM close enough to the throttle body that you can simply just connect directly to the AFM?

I'm going to put a K&N cone like the one dave used...any thoughts on this? are theyre better filters than K&N? Ive read the article on filters, but i think i would still like to go with a cone filter, looking for some sweet sound. does anyone have a sound clip that compares a KN filter to the stock M20 air filter, id love to hear the difference.

Thanks alot guys

**Mystikal** · 06-01-2006, 09:35 PM

Good article regarding the AFM: http://frwilk.com/944dme/afm.htm Ignore his comments on not adjusting it.

No need for the aluminum tube, just buy a new rubber intake boot and stretch it over the .5" larger AFM flange. To do this soak the boot in boiling hot water for a few minutes then pull it over. It'll fit.

There are better than K&N (like ITG) but the issue with the M20 engine bay on cars with cruise control is a complete lack of space. Most 3" filters will not fit in there, only K&N has a diverse enough catalogue to provide a proper sized M20 cone.

Here's a clip of my car at an auto-x. Only mods are a MarkD 91 chip and the K&N cone: http://www.utsc.utoronto.ca/~04chang...0Aug%2004.mpeg

Blackout · 06-11-2006, 05:55 PM

but honestly where are all the 325e mods?

Woofer · 06-12-2006, 12:59 AM

not much you can do really. I had a straight pipe with a borla exhaust. Cone intake. The old owner of my old eta said there was some sort of cam work and head work done to it. Not sure if that was true but i can say that it was one hell of an eta. A little more peppier then most stock eta's.