Olli Snellman

Question to all pro's; tell me advantage/disadvantage to place AFM this way:

fast951

Slightly better turbo response. But you must change certain things in the chip to compensate.

theedge

The best way to improve performance by relocating the AFM is to relocate the AFM to the bin....

Olli Snellman

Any idea why Bosch choose another location ?

rberry951

I believe it was BMW that chose the location, not Bosch. Interesting setup. I think I would go one step farther and run a pipe from the turbo down in front of the passenger side wheel well and put the filter there. Some fellows have done that with the 951s. I can't really see the passenger side in front of the turbo, do you have a duct over there feeding air straight to the filter?

Regards,
Russell

gjoey66

I relocated it in my headlight bucket and drilled a hole through...then placed the filter below...before the mod the car was running 20psi getting 235 rwhp and 258 ft-lbs...afterwards I decreased the boost to 15psi...where it was supposed to be in the first place and with the new intake setup achieved 253 rwhp and 250 ft-lbs...so I gained 15 rwhp with 5 lbs less boost...but my torque dropped off slightly...probably due to the 5psi decrease in boost...overall i can actually feel the difference in the pull because i'm getting a much more linear power response...I would run it at 20 psi...but it should never have been run there in the first place...

lee101315

A lot of people do that when they turbo the Bmw M20/M42 engine if they are on a budget and cant afford a standalone/ piggyback fuel injection.

Is that your car? That looks like a serious top mount turbo!

Olli Snellman

This is not my car, i have a 951. I just have discussed with the owner why he has plumbed it that way. It is a M42 16V engined E30 318IS. It's not a factory installation. It just have SMT6 and Garret turbo added, otherwise engine is toatlly a factory stock. Original 136 hp was risen to 200hp with 0,5bar boost.
I have not seen any factory car with Motronic/AFM hooked that way. Seems to me many BMW owners does it that way. I have seen maybe about 5-6 years ago here on Rennlist a pictures of a 951 which has AFM connected similar way.

Transaxle

Can this really work?

My understanding is that the AFM measures a volume stream (m3/h). It does not measure any density of the air (kg/m3). It should be difficult to adjust the DME with changing boost levels.

This should work with a MAF that measures the mass of the air stream (kg/h) and is able to compensate the changing air density.

Bosch placed the AFM in turbo applications on the atmospheric side to get a constant air density.

lee101315

Well, it will work ok under boost... the afm door just blows right open.

It's ok for low boost/ low power applications, but that setup will never allow that turbo to realize its full potential.

Get an aftermarket fuel/timing setup and it will make a big difference

Olli Snellman

As i wrote earlier, this is NOT my car. I have a 951.