lightning

Hi All,

I'm looking at a 1986 model carrera 3.2 with US specs and with a catalyst (207 bhp compared to the non catalyst version 231 bhp). The car drives like it was upphill all the time compared to a non-catalyst car. Can I remove the catalyst an retain the 24 lost bhp's as on the non catalyst version? I fully understand how to remove the catalyst but what about the rest of the engines management system?

RANDY P

be just fine, just make sure to use a Dansk Euro premuffler or equivalent - and make sure you have the O2 hole so that can be plugged in Best results are achieved using this vs. going with a straight through pipe. Something like 8-12 HP esp. if you swap for a free flow muffler.

rjp

ron mcatee

Lightning, I replaced my calatytic converter with a Fabspeed euro pre-muffler with a O2 sensor boss. All I did was remove the O2 sensorfrom the cat converter, screw it into the pre-muffler and disconnect the sensor in the engine compartment. This way if you ever have to recoonect due to inspection requirements...it's all there. I do suggest that if you disconnect the O2 sensor, you have the CO checked since the sensor is no longer in the system. My 88 Carrera was set at 1.0 and is very fast.

lightning

Thanks for the answers,

Randy P you write that I would gain 8-12 bhp, but where are the rest of the 24 lost bhp?

I live in Sweden and you dont have to have catalysts mounted on a car produced before october -87 .

MikeF

Spider,

Why unplug your O2 sensor? As I understand, it is an integral part of your DME fuel management system (assuming a US spec car). The sensor communicates changes in exhaust gases to allow the DME to optimize settings for various conditions (elevation, temperature, etc.).

dial911

There seems to be some confusion here...
The O2 sensor on DME cars *must* be connected.
It constantly adjusts fuel mixture as engine requirements change.

On Lambda equipped 3.0 motors, the O2 sensor *can* be disconnected. The frequency valve then operates at a 60% duty cycle as the system runs open-loop. The CO can be adjusted with the mixture screw on the CIS fuel distributor.

lightning

Now i'm really confused. "Spider911" you suggest that I shall disconnect the O2 sensor and set the CO value to 1.0. Then "dial911" you tell me that i shall keep the O2 sensor since it adjusts fuel mixture.
As I see it there should'nt be any wrong with keeping the O2 sensor connected but then again the european non catalyst cars doesn't have any sensor and they runs just fine with 231bhp. Could it be so that the noncatalyst cars have an other type of DME or perhaps just an other type of chip?

ron mcatee

Lightning, all I meant was you have the options to go either way. I tried both and found that by doing the CO adjustment at 1.0 and disconnecting the O2 sensor, performance improved at idle and top end.

You can leave the O2 hooked up, but you still need to ensure the CO is in specs and the O2 sensor works or it won't adjust the fuel mixture.

Since mine ran so bad with the O2 hooked up , the sensor may have been bad. I worked with one of the better shops here in San Antonio to get the car running superbly.

My 88 runs so much betterw/o the sensor and gas mileage also improved. If I stay off the accelerator, I get 29-30 mpg. When I autocross or drive it hard , it drops to about 24 mpg.

lightning

Thanks Spider911,

I like options so I will try both ways.
I will keep you updated on the results when I do this later on this spring.

/lightning

RANDY P

"Randy P you write that I would gain 8-12 bhp, but where are the rest of the 24 lost bhp?"

lightning -

A few guys at pelican did some dyno runs - the runs were with Motronic Carrera's and the general consunsus is that a Euro Premuffler and freeflow are so close to SSI's that the Euro Premuffler is the way to go. (true dual output)

Links:

<a href="http://forums.pelicanparts.com/showthread.php?s=&threadid=88732&highlight=euro+premuffler+dyno" target="_blank">http://forums.pelicanparts.com/showthread.php?s=&threadid=88732&highlight=euro+p remuffler+dyno</a>

this one has an email sent by Bruce Anderson himself to Steve W concerning this very topic; Bruce gave info on some dyno runs between SSI's and Euro Premuff - my interpetation of his data was that between the two it's negligible. The thread is kinda long so weed through it - it's on the 2nd page:

<a href="http://forums.pelicanparts.com/showthread.php?s=&threadid=86338&perpage=20&highlight=euro%20premuffler% 20dyno&pagenumber=2" target="_blank">http://forums.pelicanparts.com/showthread.php?s=&thr eadid=86338&perpage=20&highlight=euro%20premuffler%20dyno&pagenumber=2</a>

this one was done by Dickster in UK - he's got an US spec 86, and after adding a Euro premuff and dansk freeflow muffler he gained 12HP.

As of the other 12, the US cars had 9:8:1 CR vs the Euro 10:3 - handicap.

And if anyone is wondering, same mods on a CIS car are worthwhile - esp, for how cheap it all can be had for.

rjp