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ike84 · 09-16-2021, 05:51 PM

Silber,.

Fuel injected engines that run closed loop operations shoot for stoich. Nbo2 sensors actually only work around 14.7 because of their design. Always (unless manipulated

). This is because of emissions.

Open loop operations are different. They run much richer (afr 12-13) for better power production, retaliation prevention, and cooler running. But open loop operations only happen under very few circumstances.

I have a wbo2 installed and can confirm that the 986/996 does run at 14.7 closed loop, 12.3-12.5 open loop)

Long before there were o2 exhaust sensors, pilots used cylinder head temp and exhaust gas temp readings for each cylinder to understand what was happening inside their engine at all times. It's a simple system that can tell you an exceptional amount of a running engine.

In terms of temp numbers, egt is representative of the combustion process and changes with each stroke. stoich is max exhaust temp. Max power is about 75deg lower than stoich (this is referred to as rich of peak, or ROP).

Cylinder head temps are different. They are closest you can get to measuring the actual cylinder temp. Much slower to react to changes because we're measuring the temperature of metal but still very important because it shows what's happening to the engine material.

For example, if you run lean and start to detonate, your head will often heat up because of improper flame wave propogation. However, less fuel causes a cooler burn, so you'll see a cylinders egt drop and cht rise.

Back to your problem though -

Ok looked at your pics. Was your gasket intact on cylinder 2? That pic is concerning but I don't know if that was the culprit.

The exhaust valves are sodium filled. Good luck melting one of those. A garage in ga with extensive m96 data who actually shares his data (NOT RABY) found the only valve related issues on the 2.7 and 3.2s to be related to lifter springs. Navarro mentions that on his website as well.

https://newsite.hamheads.com/2016/12/01/m96-m97-porsche-cylinder-head-specifications-and-general-info/

I guess I'm a bit confused though...How do you know what your valves look like if you have pulled your head yet?

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09-16-2021, 05:51 PM	#26
ike84 Registered User Join Date: Oct 2020 Location: KY Posts: 1,216	Silber,. Fuel injected engines that run closed loop operations shoot for stoich. Nbo2 sensors actually only work around 14.7 because of their design. Always (unless manipulated ). This is because of emissions. Open loop operations are different. They run much richer (afr 12-13) for better power production, retaliation prevention, and cooler running. But open loop operations only happen under very few circumstances. I have a wbo2 installed and can confirm that the 986/996 does run at 14.7 closed loop, 12.3-12.5 open loop) Long before there were o2 exhaust sensors, pilots used cylinder head temp and exhaust gas temp readings for each cylinder to understand what was happening inside their engine at all times. It's a simple system that can tell you an exceptional amount of a running engine. In terms of temp numbers, egt is representative of the combustion process and changes with each stroke. stoich is max exhaust temp. Max power is about 75deg lower than stoich (this is referred to as rich of peak, or ROP). Cylinder head temps are different. They are closest you can get to measuring the actual cylinder temp. Much slower to react to changes because we're measuring the temperature of metal but still very important because it shows what's happening to the engine material. For example, if you run lean and start to detonate, your head will often heat up because of improper flame wave propogation. However, less fuel causes a cooler burn, so you'll see a cylinders egt drop and cht rise. Back to your problem though - Ok looked at your pics. Was your gasket intact on cylinder 2? That pic is concerning but I don't know if that was the culprit. The exhaust valves are sodium filled. Good luck melting one of those. A garage in ga with extensive m96 data who actually shares his data (NOT RABY) found the only valve related issues on the 2.7 and 3.2s to be related to lifter springs. Navarro mentions that on his website as well. https://newsite.hamheads.com/2016/12/01/m96-m97-porsche-cylinder-head-specifications-and-general-info/ I guess I'm a bit confused though...How do you know what your valves look like if you have pulled your head yet? Sent from my SM-G970U1 using Tapatalk __________________ 2000 Box Base, Renegade Stage 1 performance mods complete, more to come When the owners manual says that the laws of physics can't be broken by this car, I took it as a challenge...