Apexi Neo

[Deathstar]

Since we still do not have a SCT for the PT officially, I purchased a Apexi Neo to lean the motor on my 06 NA. The Neo simply changes the airflow sensor readings going to the ECU. Question is:

Will the ECU use the O2 sensor and see that I am leaning out the motor and will continue to try to compensate by adding more fuel? The Neo will make it think there is less air flow than what there really is, this will make it run leaner, but will the ECU ignore that if it sees a lean condition coming back from the O2 sensor?

Trying to make sure I am not adding a piggyback system that simply will not work on our cars.

[CREWZIN]

Pricey little piece of equipment for what you might get out of the N/A PT. I would think the ECU would try to compensate for whatever you try to do. The 02 sensors (front and rear) plus the IAT and other sensors feed into the ECU for it to make decisions on how to manage the fuel system.

I'm no computer wiz so maybe your Neo hooks up in a way to manage the ECU controls then you and lean out whatever you want without a problem.

Same as the little so called "chip" (resistor) that is added to the IAT that they sell on eBay. Makes the computer think there's colder air coming into the throttle body and the ECU adds more fuel to compensate for the denser air thereby giving a bit more performance, just like driving in cooler weather compared to driving in the heat of the summer. Only thing is, the computer is adding more fuel all the time, even during a normal in-town drive and even at idle, so there goes your fuel mileage.

[Johns Steel Blue]

I am still at a loss as to why those that have "A Need For Speed" buy a PT Cruiser

[Deathstar]

The neo basically just changes the reading on the mas/speed air sensor. Our cars run too rich, the goal is trick the ECU into thinking it is getting less air so it will lean the motor to gain more power. Thing is, I can only control the one sensor. Our PT's have smart ECU's that compensate for everything, including your driving style. So I am afraid I may be wasting $350 on something that my ECU will learn to ignore. I need a "Don't Ingore Me" button on the dash.

And yes, my PT is no race car, but it looks hot, has some decent power now and definetly turns heads compared to other rice burners.

[JoeHundredAire]

You could always put an inline resistor on the rear O2 sensor to have it give a constant reading. I know this is one method used in running aftermarket exahusts that eliminate the cat converter without tripping codes.

[THS_Cruiser03]

I'm remembering when we talked about this in the "Porting NA head" thread. You mentioned getting the Neo computer (nifty device btw). My guess is somebody in Tech. support for the Neo knows how it works with the PT computer (unless they don't sell it for our NA PT application) and can explain it.

But I still go back to my original question: Since the PT does have dual O2 sensors and MAP or MAF sensors it knows the following:

It knows how much air is getting pulled into the motor (and that air's temp.)
How rich/lean your exhaust is....
And will compensate (up to the capacity of your stock fuel injectors) accordingly.

Why would you need the Neo? I'm guessing if you have a turbo car and you drop in a wild race cam & increase boost pressure 8 or 10 PSI above stock then you're fuel system might "lean" out because it can't provide enough fuel for the added air coming in, thus cooking your motor.

That's probably where the Neo comes in to help control the larger injectors and dial everything in. My impression is that the Neo will then replace your stock ECU.

But maybe I'm thinking wrong on this one?

[Deathstar]

Actually you are thinking in reverse for the Neo. I do not have a turbo, so I will not be forcing in additional air and needing to add more fuel. It is the exact opposite. Our cars run rich all the time to begin with, so the neo will make the ECU think it is getting les air so it will lean out the fuel, meaning run less fuel. This will give you more power. Everyone make their first mistake by adding large injectors and no good way to control them. Running too rich cuts your power. You want the A/F to be perfect and the stock ECU trys to run a little rich to keep the motor safe.

So. I will be adding the Neo in a week or so, just as soon as the new bored TB comes in. I will finally be off to the Dyno for tuning and measure the effects of the ported head, TB, cams, exhaust, underdrive pulley, Neo, fiberglass hood, etc. We will see what a NA PT, built by a weekend warrior, can do... once and for all.

Actually there will be a little 75hp Nitrous on it too. I am betting on low 15's possibly high 14's in the quarter.

[Deathstar]

Originally Posted by JoeHundredAire

You could always put an inline resistor on the rear O2 sensor to have it give a constant reading. I know this is one method used in running aftermarket exahusts that eliminate the cat converter without tripping codes.

That might be a good solution to help control the O2 sensor if it keeps causing the ECU to override the Neo on the Air meater. I am thinking a very high quality variable resistor so that I can slightly tune it with the NEO.

[cleverklutz]

I think one problem you'll run into is what Crewzin touched on, that past certain degrees of throttle application the PT starts ignoring certain sensors. Essentially it goes from closed loop to open loop. I'm not sure which sensors it cuts out, but I think the 02 is one of them for sure. MX5 discovered this when he was writing the installation guide for the JET chip. Anything past a 85% throttle angle the system would go into open loop and no longer "see" the chip.

How rich does the PT run? Most guys try to aim for an air fuel ratio of 12.5:1 which gives you maximum power with a naturally aspirated engine. Most manufactures aim for 14.7:1 where the least amount of pollutants are produced.

The second 02 sensor or aftercat sensor, only tells if the cat is working or not. If it's not, it will pull the CEL. It doesn't modify the AFR any.

I would suggest maybe looking into megasquirt. I don't know if you've heard of it before, it's a do it yourself ecu system for cars. You have fully programmable volumetric efficiency tables and timing tables, and full control over anything you want. Lots of guys have done it with the older turbo mopars. If you go to turbododge.com or turbo-mopar.com you can find more about the system. Guys have been using it with hybrid motors, 2.2 blocks with 2.4 heads.

Here's a link to megasquirt

I have a programmable ecu on my atv which I think is based on the microsquirt setup. It's pretty much the same as megasquirt but open loop, no 02 sensor. The ecu I have allows me to change anything I want, add or remove limiters for reverse or diff lock, raise or lower rev limiter, change injector size, change injector open time (latency between the injector being triggered by the computer to actually opening), change warm up values, complete control over fuel table in 200rpm increments, complete control over timing table in 200rpm increments.

Just something you may want to look into as it would be a complete solution and you then will know that it won't cut out when flooring it!

Ben

[Deathstar]

Thanks Ben, I am hoping that the ECU does lock out the O2 at wide open throttle, that means it will not try to adjust the fuel. What I hope does not happen, is that ignores the the MAS air sensor. That is the one I am modifying with the Neo. I would not think it woudl ignore it becasue that is how you can richen a fuel system with a turbo. Just not sure how the NA ECU handles things.