Another S/C'd member worried about his AFR

[Loren]

Without taking the time to read through this whole thread... some thoughts.

What does "open loop" mean? It simply means "not closed loop". Closed loop means that the ECU is using feedback from the O2 sensor to fine tune the fuel mixture and keep it at stoich (or, I suspect maybe even a tad lean on the Yaris, but that's just a guess). In open loop, the ECU is most definitely still making adjustments and still has complete control of timing and fuel, it's just ignoring the O2 input and using intake air temp (temp affects density, a critical factor), air flow, and RPM to look up the appropriate fueling and timing in a table. By design, this will always be a rich mixture, and timing will be "conservative", similar to that of a distributor with no vacuum advance.

Now, I was thinking about all of this worry about being lean on these SC cars. (because I noticed one for sale for $2500 and had a fleeting moment where I was thinking about it... until I remembered that I don't have the money) Remember, even though your car is "forced induction" with the SC kit, it's a VERY light boost. What is it? 4psi? Maybe 6psi? Guess what? The real problems with fuel and spark retard don't happen until way beyond there. You guys are applying the kind of fear that one should have with a medium-high boost turbo to a low-boost supercharger, and I really don't think it's warranted at all.

I'd rock a Blitz SC right out of the box. Run premium fuel and be happy. Life is too short for such paranoia!

[Nexus1155]

See, but thats the thing, you can get one of these out of the box be happy and be fine, but not run optimally. I think thats what everyone is looking for. And it is such a small amount of boost that supercharger is running.

What I am trying to think now is that if you do have extra injectors it might be the only feasable option to get the AFR correct for now until someone finds an interceptor for the O2 Sensors, but will it cause a rich condition and trigger a CEL as well!. Damn these cars to hell

[Loren]

Originally Posted by Nexus1155

See, but thats the thing, you can get one of these out of the box be happy and be fine, but not run optimally. I think thats what everyone is looking for. And it is such a small amount of boost that supercharger is running.

What I am trying to think now is that if you do have extra injectors it might be the only feasable option to get the AFR correct for now until someone finds an interceptor for the O2 Sensors, but will it cause a rich condition and trigger a CEL as well!. Damn these cars to hell

Okay, I'll buy that (though I don't think there's THAT much more to gain by tuning the fuel WITHOUT adding more boost). But, the topic of this thread was, I thought... "worry" about being too lean. Worrying, I assumed about possible detonation and engine damage, not about leaving a little bit of power on the table.

One last thought: Tuning to get every last HP out of an engine is an art as much as it is a science, it's hard to do. If you screw up in the process of tuning it, you can do some damage. And once you've tuned it, you're right on the ragged edge of... trouble. Unless you're running a race team with a budget to replace the engine when it breaks, it's a lot smarter to go ahead and leave a little bit of performance untapped. Leave some margin for error. Leave the tune such that if your fuel happens to be 88.5 octane one day instead of 91, the engine still won't detonate. Out of the box, the Blitz is giving you 20% more power than stock... be happy! Be RELIABLY happy! (isn't that why you bought a Toyota?)

What's left on the table with the Blitz, anyway? Another 2%. Is it really worth all of the extra money, hassle and potential reliability issues for 4-5 hp? Every wire you cut and splice, every wire you add, every piece of hardware you add is another potential point of failure on your car.

[largeorangefont]

Originally Posted by Nexus1155

See, but thats the thing, you can get one of these out of the box be happy and be fine, but not run optimally. I think thats what everyone is looking for. And it is such a small amount of boost that supercharger is running.

What I am trying to think now is that if you do have extra injectors it might be the only feasable option to get the AFR correct for now until someone finds an interceptor for the O2 Sensors, but will it cause a rich condition and trigger a CEL as well!. Damn these cars to hell

You are really overcomplicating this. If you really want adjustability, go buy a Greddy Emanage and be done with it. I know that is not the answer you want to hear, but in the end it is the simplest and cheapest.

[largeorangefont]

Originally Posted by Loren

Now, I was thinking about all of this worry about being lean on these SC cars. (because I noticed one for sale for $2500 and had a fleeting moment where I was thinking about it... until I remembered that I don't have the money) Remember, even though your car is "forced induction" with the SC kit, it's a VERY light boost. What is it? 4psi? Maybe 6psi? Guess what? The real problems with fuel and spark retard don't happen until way beyond there. You guys are applying the kind of fear that one should have with a medium-high boost turbo to a low-boost supercharger, and I really don't think it's warranted at all.

I'd rock a Blitz SC right out of the box. Run premium fuel and be happy. Life is too short for such paranoia!

This is what I said the the beginning of the thread. These guys are not going to blow their cars up, they are just not optimal. They would get better mileage and more power under the curve with more agressive timing and richer AFRs, VS. the current setup of leaner AFRs and conservative timing.