[torsen] Pushing the N/A engine

JShadzi at aol.com JShadzi at aol.com
Wed Oct 24 12:08:02 EDT 2001

Hi Dave,

 <<What can I do to the NF engine in my '89 90q.  I know, I know, swap for a 
 turbo.  Well...assume for now that it's not an option (I have).>>


Ohh, more on this later ;)

<<What are my options here? >>

On the street?  Not much, you only have a few options if you are ruling out a 
turbo swap or going to the 20v head.

Flow- A cam will help, as will port matching the manifolds and polishing the 
ports in the head on in the intake manifold, but you already have the big 
valve head.  A good exhaust is a must, the stock manifold is pretty good, a 
small improvment can be had with the triple outlet manifold from the 4kq.  
Not much you can do on the intake side, you could bore the throttle body for 
some high end increase, but not much.  As long as you are sucking throught 
that CIS metering head you are limited.  I would estimate a really hot motor 
with a well executed porting job, cam, throttle body, free flowing exh 
manifold/system would loose some bottom end power,  but could probably make 
150hp at 6k RPM, a 20hp increase over the stock 2.3 NG/NF output.  Still not 
a fast car, but might pick of a second or so in 0-60.  Cost to do all this, 
probably $1k to1.5K after the head rebuild, etc, pretty expensive for 20hp 

-Displacement- Using the Eurovan 95.5mm stroker crank, you could create some 
additional displacement, about 2.5l or so.  Add this to the upgrades above, 
and IME you could have about 170hp, with much more torque to boot.  This 
would be a real stump puller, super long stroke, you would loose some high 
RPM performance and smoothness, but have a great bottom end.  This one starts 
getting expensive, after machining, custom rods, stroker crank etc, you could 
easily have another $2000 into it.  Of course, this stuff always starts 
adding up, well, now that you're in there, the clutch, etc, etc.

So, after these two areas of modification, you could have a quick, peppy car, 
very tourqey, with good all around power, for about $3.5k-$4k (probably a lot 
more), a 50 hp increase.  Remember, the 1994 BMW 325i came with 190hp and 
variable valve timing.  Those are not considered "FAST" cars, and you would 
be lucky to keep up with one of those, and you can pick one up in great 
condition in the low teens these days.

My recommendation is to do a turbo conversion, simply by swapping in an MC 
motor into your car, but keeping your stock fuel and ignition system, you can 
safely run 8psi boost which equates to about 180hp too, with a lot of torque, 
especially if you used a K24, turbo lag would be non-existent.  This swap 
could easily be done for under $1k, get a junk yard motor and replace the 
seals and headgasket.  Very hard to beat, without all the wiring and fuel 
system swap you have to worry about with a full MC conversion.  

I ran my 80q like this with a similar conversion for over 30k miles, 
performed very well and reliably, and I have assisted others in doing similar 
conversions with similarily great results.

Javad Shadzi

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