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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. |
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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 |
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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. |
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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 |
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Thankfully, my curiosity caused me to shake it, otherwise, I may have reinstalled it, none the wiser.. |
So you want a little more than anecdotal?
http://forums.pelicanparts.com/uploa...1756504655.jpg 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 http://forums.pelicanparts.com/uploa...1756505667.jpg 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! |
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 :confused:
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Looks like the transmission is eating near 30% of power. Something has to be wrong here. Engine, trans, or bench.
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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. |
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. Quote:
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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.
http://forums.pelicanparts.com/uploa...1756734568.jpg http://forums.pelicanparts.com/uploa...1756734568.jpg |
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 |
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A 95 is a totally different animal. It has a chip, but it is not a G body car. |
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