Steve Wong/911chips.com

[GH85Carrera]

The biggest difference with a cat delete is a stinker exhaust, especially in the garage at startup, a deeper and richer sound from the muffler, and maybe a couple of HP. More if your cat was partially plugged.

Most come with a O2 sensor bung, so the computer is happy. And the bypass is much cheaper than a new cat.

[PopsRacer]

Originally Posted by GH85Carrera

The biggest difference with a cat delete is a stinker exhaust, especially in the garage at startup, a deeper and richer sound from the muffler, and maybe a couple of HP. More if your cat was partially plugged.

Most come with a O2 sensor bung, so the computer is happy. And the bypass is much cheaper than a new cat.

Yes, kept the O2 sensor. I read an old thread here with the experts and if i understood it right, the ecu will run lean with no signal from the sensor, so thats out.

[mysocal911]

Originally Posted by PopsRacer

Yes, kept the O2 sensor. I read an old thread here with the experts and if i understood it right, the ecu will run lean with no signal from the sensor, so thats out.

Guess again. It's just the opposite, a little richer!

[proporsche]

i took off the oxy sensor the 1st week i got my 85 911 back in 1996..Those days i even pass the smog in LA, so it is all about adjustment no oxy needed...
Ivan

[famoroso]

Originally Posted by PopsRacer

not to get back on topic

Aaaand we're back.

Originally Posted by GH85Carrera

The biggest difference with a cat delete is a stinker exhaust, especially in the garage at startup, a deeper and richer sound from the muffler, and maybe a couple of HP. More if your cat was partially plugged.

PSA: Have you shaken your cat lately?

[scarceller]

Originally Posted by mysocal911

Guess again. It's just the opposite, a little richer!

Agree 100%, if you setup mixture correctly to spec you don't require running a stock O2 sensor. It won't run lean, it actually will run like the ROW cars that have no cat converter.

The O2 closed loop was simply a way to bring mixture back to a baseline if the base mixture drifted off lean or rich. This can occur if fuel pressure goes off spec, a injector or 2 get bad spray pattern or clogged, ... bottom line the O2 closed loop is NOT required even in a USA car. Furthermore, if you have removed the cat converter you really should not be running the stock O2 sensor.

[scarceller]

Originally Posted by famoroso

Aaaand we're back.



PSA: Have you shaken your cat lately?

That cat sounds like someone tried to gut it out?

[fetus]

Originally Posted by scarceller

Agree 100%, if you setup mixture correctly to spec you don't require running a stock O2 sensor. It won't run lean, it actually will run like the ROW cars that have no cat converter.

The O2 closed loop was simply a way to bring mixture back to a baseline if the base mixture drifted off lean or rich. This can occur if fuel pressure goes off spec, a injector or 2 get bad spray pattern or clogged, ... bottom line the O2 closed loop is NOT required even in a USA car. Furthermore, if you have removed the cat converter you really should not be running the stock O2 sensor.

Is that also true for a stock 1995 993 motor? I am running 1 3/4” headers, no cats.

[scarceller]

Originally Posted by fetus

Is that also true for a stock 1995 993 motor? I am running 1 3/4” headers, no cats.

I suspect the answer is the same for the 993 Engine, if you don't have a cat converter then the engine should run fine with no O2 connected.

But the best way to check is to install a decent WideBandO2 (WBO2) gauge and confirm AirFuelRatio data as follows, with engine fully warm, O2 disconnected:

At idle - 13.8 to 14.5 is a decent idle AFR target

3000RPM in 4th gear on level road, this is steady state part throttle check, you want to be in the 14.4 to 14.8 AFR range

Then anytime you are at WOT you MUST be less than 13.0AFR, stock chips tend to run richer in the high 11s to low 12s. The important thing is never run leaner above 13.0AFR

[famoroso]

Originally Posted by scarceller

That cat sounds like someone tried to gut it out?

No sir. Actually, the unit appeared normal upon a visual inspection. The honeycomb was intact on both the header and muffler sides. Somewhere in between though, the ceramic matrix had given up the ghost.

Thankfully, my curiosity caused me to shake it, otherwise, I may have reinstalled it, none the wiser..

[sus911]

So you want a little more than anecdotal?



This graph shows the car around 2007 with the WOT switch not adjusted correctly on Run 1 & 2, the switch correctly adjusted Run 3 & 4, and Steve Wong chip Run 5 & 6. Car is stock ROW '84 3.2



This is the same car in 2019 with the only change being 993 Bischoff HE's & M&K 2 in 1 out muffler fitted. Looks to me like about a 5HP gain from the exhaust change. AFR looks a little better also.

Both graphs are same dyno, same car, 12 years apart.

Funny how our ROW cars don't make anywhere near the reported HP of the lower compression stock US cars!

[ant7]

Should be the other way around in reality, we have access to better fuel, hence can take advantage of the higher compression ratio, so not sure what's going on there
Ant.

Originally Posted by sus911

So you want a little more than anecdotal?



This graph shows the car around 2007 with the WOT switch not adjusted correctly on Run 1 & 2, the switch correctly adjusted Run 3 & 4, and Steve Wong chip Run 5 & 6. Car is stock ROW '84 3.2



This is the same car in 2019 with the only change being 993 Bischoff HE's & M&K 2 in 1 out muffler fitted. Looks to me like about a 5HP gain from the exhaust change. AFR looks a little better also.

Both graphs are same dyno, same car, 12 years apart.

Funny how our ROW cars don't make anywhere near the reported HP of the lower compression stock US cars!

[wazzz]

Looks like the transmission is eating near 30% of power. Something has to be wrong here. Engine, trans, or bench.

[sus911]

Originally Posted by wazzz

Looks like the transmission is eating near 30% of power. Something has to be wrong here. Engine, trans, or bench.

I hear you but be assured that there's nothing wrong with the car. It has proven that over my 38 years of ownership on the road and the track.

But numbers are just that and only relevant when variables are kept consistent, such as using the same dyno, environment etc...

I have tuned many motorcycles on dynos with varying results from different dynos. Comparisons become meaningless. A 15% drivetrain loss on a motorcycle is a widely accepted phenomenon (chain & sprocket drive). It's not hard to imagine that a car has significantly more.

In any case, the purpose of my post was not about HP numbers but the delta resulting from small changes.

I hope this helps some owners out there with their expectations.

[87m491]

My car came with the Ruf 9s and 10's. Way too much tire for the car. 235s and 285s I think. No fun at all around town. When I let other folks drive the car they were not impressed w Porsche or with the steering effort.
Not sure how long you drove the 930, but outside of hwy speeds or the track I passed.
Now run turbo look wheels, just like the car.

Originally Posted by famoroso

Fair enough. Soooooo... What, if anything,.can be done to improve WB steering feel?

Somewhat separately, as much as I'm a 16" Fuchs, especially Fuchs Evo, fan boy / devotee, I think my '89 M491 "hot rod" build (eventually shooting for ~2,500 pounds & ~350 hp) is likely gonna need more rubber than my current 205 & 245 happy place. If I do Ruf 9&10 x 17 wheels, what are the recommended tire sizes? I'm not looking to cram the absolute largest tires possible under the fenders as I would A) prefer to avoid fitment issues and B) attempt to preserve some steering feel.

BTW, I know we've gone completely off the rails / this post's original topic.Such is life in the big (Pelican Parts forum) city.

Drove this Ruf wheel "laden" '89 930 last fall. It and it's wheels "left a mark."





Thx!

[PopsRacer]

Finally got the car on a dyno this past Saturday. 134,000mi, and some pretty bad valve guides so I was really looking at a ‘before’ measurement as the engine is coming out this winter for whatever it needs. Currently running a FS euro pre-muffler, dansk 1:1 sport muffler, cup-style airbox cover (mostly for service access) and a SW chip dialed in for 91 octane and the exhaust mods. With an ambient temp of 70 F, it put down 217 at the wheels and 186 ft/lbs. (249 & 213 resp) which far exceeded my expectations, and explained the ease of throttle steering I have been enjoying. . It is running the O2 sensor.

[VegasMat]

About to pull the trigger on a '95 Carrera. The seller isn't sure if it has the chip or not. The only way to know for sure is to see it on the DME, correct?

Thanks

[Terrafirma]

Originally Posted by VegasMat

About to pull the trigger on a '95 Carrera. The seller isn't sure if it has the chip or not. The only way to know for sure is to see it on the DME, correct?

Thanks

You have to open up the mototronic ecu under the seat. There is instructions on 911chips website

[GH85Carrera]

Originally Posted by VegasMat

About to pull the trigger on a '95 Carrera. The seller isn't sure if it has the chip or not. The only way to know for sure is to see it on the DME, correct?

Thanks

A 95 is a totally different animal. It has a chip, but it is not a G body car.