AFR with Supercharger on 95+ (1 Viewer)

[lumbee1]

I pulled my engine and had it rebuilt in the fall of 2021. In October of 2022, I installed a supercharger, In April of this year, my head gasket failed by the water jacket of cylinder 6 after 15K miles with the supercharger. I replaced the head gasket with a Toyota OEM v2 gasket and installed ARP head studs. The engine never went critical while running hot so it didn't require machine work.

I finished the head gasket replacement at the end of August but I've been driving the truck lightly in fear that I might blow the gasket again. My plan was to add an AEM AFM and fuel enricher to ensure the engine never runs lean under boost and to prevent another failure. I recently installed an EMS exhaust and had a bung for the wideband added in for the air fuel meter. The fuel enricher has not been added yet.

I've been monitoring my AFR for the past three days of mixed driving and I'm trying to determine if the next step is a boost gauge for additional monitoring or to complete the installation of the enricher.
- Driving around I'm averaging 14.6.
- WOT I've seen as low at 10.4
- 3000 rpm at 80mph is around 14.2 to 14.4
- Punching it for a downshift typically results in 13 to 14.

My concern is that the engine is not dumping enough fuel to compensate for boost and sometimes it is slow to richen the mix as the boost starts to climb. Is this normal and I shouldn't worry and was my original head gasket failure just a fluke?

BTW, my 1st replacement gasket was not Toyota OEM but rather LC Engineerings gasket. It was based on Toyota's OEM v1 gasket with triangular jackets for the rear of the head. The Toyota v2 gasket has round water ports.

LC Engineering left, OEM v2 right

 

[Saito]

10.4 is rich. 16 would be lean and a danger zone. 14ish is stoichometric(sp). Doubt you need the enricher if you’re OBDII.

 

[pavell]

Too much spark/timing can pop the HG

 

[ppc]

An AFR gauge will provide some information but to really monitor things I would install a Exhaust Temp gauge. With that gauge you can tell when its time to back off the load. A reading in the 1300 degree range is most likely not going to be a problem but when approaching 1400 for any extended time the risk of damage high is time to back off, At 1500 degrees is time to back way off.

 

[Odilon Noble]

Given the AFR values you are seeing it make sense to be concerned about boost richness. A boost gauge would give you useful data, but installing the fuel enriche would give you peace of mind and avoid lean spikes

 

[ppc]

Given the AFR values you are seeing it make sense to be concerned about boost richness. A boost gauge would give you useful data, but installing the fuel enriche would give you peace of mind and avoid lean spikes

A boost gauge is a useful/fun tool when you first install the supercharger but on a day to day basis doesn't give you any indication of lean or rich. My experience is that you are going to be running zero or 5 psi, nothing inbetween. It's very difficult to feather the throttle to get, as an example 3 psi. You have to be on a lonely road with your attention completely on the boost gauge. During any normal highway driving you will not be able to that.

 

[landtank]

The stock ECU is a really robust unit and if you don’t have a CEL you doing just fine.

 

[pavell]

The stock ECU is a really robust unit and if you don’t have a CEL you doing just fine.

But does the stock ecu use a narrowband or wide band ?

 

[ChargedSHOTaco]

But does the stock ecu use a narrowband or wide band ?

I believe they are narrowband.

 

[landtank]

It uses a narrow band.

 

[scottryana]

Realistically it isn't that the computer is robust, it is that the computer is a turd, but that works in our favor with regard to SC and low power turbo setups because the computer is not in closed loop as often as it could and instead is in open loop dumping fuel allowing boost.

I would say if your truck is in normal operating conditions it has been proven through tens if not hundreds of thousands of miles that the fuel and timing conditions work just fine with stock ECU and TRD SC.

 

[landtank]

Realistically it isn't that the computer is robust, it is that the computer is a turd, but that works in our favor with regard to SC and low power turbo setups because the computer is not in closed loop as often as it could and instead is in open loop dumping fuel allowing boost.

I would say if your truck is in normal operating conditions it has been proven through tens if not hundreds of thousands of miles that the fuel and timing conditions work just fine with stock ECU and TRD SC.

Believe what you want. I’ve done countless tests on how our ECU responds to un favorable fueling situations and even when the CEL light was on it was fueling the engine the same according to my wide band.

Only when I installed 600 cc injectors which delivered half again the amount of expected fuel did I start seeing issues with drivability and a rich running situation.

I stand by my claim that if you don’t have a CEL light on you are fine.

 

[scottryana]

Believe what you want. I’ve done countless tests on how our ECU responds to un favorable fueling situations and even when the CEL light was on it was fueling the engine the same according to my wide band.

Only when I installed 600 cc injectors which delivered half again the amount of expected fuel did I start seeing issues with drivability and a rich running situation.

I stand by my claim that if you don’t have a CEL light on you are fine.

That is exactly what I just said.

"I would say if your truck is in normal operating conditions it has been proven through tens if not hundreds of thousands of miles that the fuel and timing conditions work just fine with stock ECU and TRD SC."

But it isn't because the ECU is robust it is because it is old

 

[landtank]

That is exactly what I just said.

"I would say if your truck is in normal operating conditions it has been proven through tens if not hundreds of thousands of miles that the fuel and timing conditions work just fine with stock ECU and TRD SC."

But it isn't because the ECU is robust it is because it is old

My point is even if the ECU is outside normal operating conditions and the CEL light is on it adapts and still fuels the engine as if nothing was wrong.

It’s only when things are crazy out of whack that bad things might happen.

It’s this adaptive ability that I’m referring to as it being robust. That and all the monitoring and protection aspects as well.