open / closed loop, calling all Bosch FI guru's

andnew · 09-13-2003, 02:55 PM

I'm in the process of transplanting a motor (rebuilt by me) into an 83 944.

I already have some friends in a local exhaust shop, and a set of headers on the motor.

I'm thinking of going to a dual header back system, there's plenty of room for it. The question is, when I go duals with no cats, (off road, of course) will I pick up enough of a HP gain to make it worth the effort. Secondly, does anyone know of any documentation to convert the DME to ROW with no cat / 02 sensor?

BTW I have access to a 4 gas analyzer and am familiar with adjusting the AFM to the required 1.8 - 2.0 CO.

Thanks all!

ae1969 · 09-13-2003, 06:36 PM

Honestly............ just getting rid of the Cat will be enough for your NA.

The headers on the 944 are actually quite good. You would need to really do some agressive cam work/head work to justify spending money on any upgraded headers.... IMO

andnew · 09-13-2003, 06:42 PM

I certainly wouldn't have bought them, they came with the donor motor :-)

Just trying to squeeze the easiest bang for the buck while the motor's out. (It's hard to get much more out of a stock N/A, except with large bags of cash).

They do weigh 8 pounds less.

Roger Hall · 09-13-2003, 06:43 PM

There are alot of people who belive that lowering the back pressure will lower your HP. Creating a dual header system would possible be to free flow for the 944.

It is my understanding that if you simply disconnect the O2 sensor wire your DME will ignore it. If thats correct there is no reason to convert the DME. I think the euro DME's do have some advantages but its not worth converting IMHO.

andnew · 09-13-2003, 06:57 PM

Cool! I was wondering if it just went straight to fixed mapping when O2 was disconnected.

I was still going to be running a relatively quiet dual muffler setup if I do this. I think this will still keep enough back pressure in the system. I've played with straight pipes on some bikes, the HP definitely drops when there is 0 back pressure.

The last thing I want is for this to look like some rice monkey, I want it to be tastefully done. (Read no 3" dumps or SS mufflers) Just stock diameters through a staggered rear muffler setup and a dual outlet that mirrors the stock look.

Oh, and no cats ;-)

gearhead290 · 09-13-2003, 09:00 PM

I think you should just gut the cat and call it good. IMO a 4 cylinder with dual exhaust is just sheer rice, you can acheive the exact same result with running a larger diameter single exhaust, not to mention you would be saving the weight. If you're wanting to make your ideal exhaust build a custom 2.25 or 2.5 inch mandrel bent with a straight through muffler.

andnew · 09-13-2003, 09:10 PM

hmmm. That's a damn fine idea. I might just do that.

nige944 · 09-14-2003, 09:30 AM

You could fit an FRWilk Powerprom + adaptor board (adaptor required for pre 85.5 cars) they are currently on sale - see other posts. I just did mine and i have zero soldering skill, well i did have when i started. :-)

The FRwilk chip ignores the 02 sensor, and generates noticably more power in the low end and the kind of induction noise between 4k-6k that i have only heard when i forgot my K+N was in the sink being oiled and drove to the store without one.