ATI Supercharging

[Seth Allen]

On Wed, 3 Apr 1996, Frank Parker wrote:

> Date: Wed, 3 Apr 1996 15:15:07 -0500 (EST)
> From: Frank Parker <fparker at umich.edu>
> To: Doug Gubbins <doug at apogeesys.com>
> Cc: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re: ATI Supercharging
> 
> > 
> > I'm running an aftermarket intercooled supercharger on a 1.6L Mazda Miata.
> > Max boost 12psi, using 93 octane fuel, higher when I can find it. The system
> > uses a boost-controlled variable fuel pressure regulator and an MSD spark
> > retarder.
> > 
> > 
> > I am considering replacing the MSD spark retarder with a knock sensor
> > package that also contains an LED oxygen-sensor monitor. But it isn't cheap.
> > 
> I have a lot of experience using those fpr and msd boost retard. The first
> thing you need to do is find out if you are rich which I suspect. The O2
> sensor does put out a voltage when changes very little from rich to very
> rich unless you buy expensive $2500 UEGO sensor/electronics package. You
> need to dial in the a/f ratio better and it is hard to do with fpr. Can
> adjust to be ok @ 5psi, then off @ 12psi and reverse. There are some new 
> electronic controllers to chg fuel press with boost but much more 
> controllable. 
> Hook digital voltmeter up to o2 sensor and monitor while driving. Will
> jump around but average about .5 during cruise. If lift throttle will drop
> to 0 as cpu shuts off fuel and @ wot should be about .8 volts. 
> I have lots of other things you can do. email mail back if interested.
> 
<snip>

 Frank Parker> 
<paste>
--I mostly agree with Frank--

IMHO, it is running rich,  which results in the highest exhaust temp.  
Lean has excess oxygen, but the temp is cooler, the excess oxygen burns 
valves and seats that way. A lean misfire with unburned fuel and oxygen 
would really heat up the catalyst as it burned in the matrix. You could 
detect a lean misfire as it stumbled under boost.  Leaning it back to 
stoichiometric would cool it off a bit, but if it got lean, the exhaust 
valves could have a hard time.  I think you might need a bigger catalyst 
to reduce the catalyst loading. The stock catalyst cannot put up with the 
extra exhaust gasses.  The stock catalysts on my VW golf will eventually 
die an early life when exposed to continuous full throttle and stightly 
rich mix. (My friend had this problem with his Golf gti, I had slight 
clogging with my rabbit gti).

So, IMHO get a larger catalyst, maybe V8 sized.

Good luck, 


Seth Allen

WWU Vehicle Research Institute

These opinions are just my own, and no warranty is expressed or implied.