Hi John,

Thanks for the kind reply. I'm still trying to wrap my head around this.

The larger number in the air/fuel ratio is the number of parts of air in proportion 1 part of fuel.

I don't have the X308 Engine Management System manual, but I do have one for the X300. To quote that manual, "A closed loop system between fuel injection, ECM control, and exhaust oxygen content feedback is used to maintain an optimum air/fuel ratio as close to 14.7:1 as possible. In response to oxygen sensor voltage swings, the ECM continuously drives the air/fuel ratio rich-lean-rich by adding to, or subtracting from the baseline injector pulse duration."

So here's where I'm not quite following you:

An AFR of 13:1 equates to a mixture of 7.7% fuel.

The AFR of 14.7:1 stated as ideal in the manual equates to a mixture of only 6.8% fuel. You state, "Most cars from factory run way too rich," but the factory-designed target AFR is actually leaner, not richer, than your stated ideal AFR of 13:1.

If my math is correct, you are attempting to achieve a result of a richer AFR, which seems to be in direct opposition to your stated goal of a leaner mixture. Please explain.

Thanks!

Don

 

You must be making your own space program or shooting for a new land speed record. You have made the right choice, possibly protecting millions of investment dollars

Or perhaps just not willing to share information with a user group having similar interests

I've been in the auto industry long enough to know that is has to be one of these.

 

Instead of using a band-aid like the Apexi unit why not go with a fully configurable stand-alone system that can be had for not much more money and allows a great deal more configurability and engine control while allowing for compensating controls that the factory "rich" setup was designed for?

Elevation, air pressure and humidity play huge roles in trim needs.

 

Not. In Australia at least a stand alone computer is $2000 or more, then you spend two days wiring it. That is if it works being a late model car and being automatic is a problem.

 

A system like megasquirt is available globaly for a few hundred bucks, transmission control can still be handle by factory ecu or tcm. Since eec is available and terminated at the bulkhead wiring it can handled in a few hours. If you are assembling and coding your own ecu I would allow a day for tuning.

Any performance tuner worth his salt should be able to pull this off with little effort, you just may have to put in some leg work to find the right guy.

The age of the car is usually not a concern, worse case scenario you setup batch fire and then build up from there. Ditch the maf, go map and play on.

I'm not a fan of "industry secrets" so if you have any questions please feel free to ask and I will be more than happy to assist. I've been building all matter of cars for 20+ years so have I quite a bit to offer.

Please check your ego and sarchasm at the door.

 

So how much do you think this would cost set up in the car? It is not a flash tune and requires wiring in doesn''t it? Suggesting going from individual injector drive to batch fire is a backwards step.

Don B I am not talking about, idle,light throttle and cruising, rather under load where 02 sensors are not used. Under load AFR's ideally as I said should be 13-1. for normally aspirated engines.

What we did was modify, or rather replace, the factory restrictive snorkel to the intake and run secondary hose from the air box past the air flow metre to the intake. Note the car already had a K & N filter, which made a big difference years ago when we tested it. Around 10rwkw from memory.

 

Really depends on how far you want to go, as little as $300-$400USD if you know electronics. Batch fuel and wasted spark isn't backwards if your goals are more performance minded than fuel economy and all have their own merits.

I am just speaking of one system because it is one I have the most experience running and being involved with. There isn't much meat on the bone in XJ8 tuning unfortunately without really getting into power adders. Magical HP is a thing of the past with newer cars, without internal engine work or adding FI you aren't going to get much of an ROI with simple systems.

Wiring is wiring, thats all knowledge and very little cost of material.

What flow restrictions were you seeing with the factory intake setup? Adding unmetered air to the intake carries it's own set of problems, not not something I can recommend to others, especially those in varying climates.

 

Thanks for the additional info.

So with your setup, are you saying that the AFR will always be in the range of 13:1, or only under load? If it's always near 13:1, is there a risk of premature Cat failure?

Do you happen to know the standard AFR mapped into the Jag ECM for load enrichment?

Does your setup cause the system to trigger any fault codes?

Thanks,

Don

 

Hp increases still happen much the same. Easy things like free flowing exhausts always gains power, improving the intake etc Tuning fuel and ignition maps improving on the factory docile settings in most cases see produce good gains. Although more complex on some later model cars.

Setting cars up to run closer to 13 to 1 AFR rather than running too rich is better for the engine and Cats. Cats can damage by getting too hot from having too much un burnt fuel going through them.

 

Ok, so I got my head around what you are claiming, I think. That is, the factory open loop control is running near 12 to 1 AFR and you have made it go to 13 to 1 AFR under WOT for a boost of HP. Is that it? Ok, I suppose that is useful info for some.

My experience is only on the road with data logging from the car's wide band lambda sensors, but I do not have the sense that my MY 02 XJ8 is anywhere near as rich as 12 to 1 AFR while near WOT. How was your AFR data measured?

And, do you have an answer to AVOS' question about the anomaly on the data for your first dyno picture for the red version?

 

Also before anyone gets hung up on HP, remember this

Horsepower sells cars, Torque wins races.

 

Yes correct torque is what pushes the car. See the second dyno pic which shows a huge increase everywhere in graph. Even my wife noticed after driving the car.

AFR was measured on our Dyno Dynamics Dyno which uses a 4 wire wide band 02 sensor.

We did this for an increase in power, (both kilowatts or horse power and torque) and economy and driveability improvement, who doesn't want that?

 

As far as the anomaly with the air fuel ratio of the car car as it was standard, red line. I see it seems to flat line to start with around 14.4:1 then it makes its way down richer to around 12:1, finishing at 11.7:1 on that run at least. After modifications, it seems to run richer earlier in that run, as per the blue line, when it's under load, it is around 12.7:1 and finishes off a bit richer. We have just changed to a new dyno sensor after this as it was playing up a little. The runs start at a slightly different speed. Performing numerous runs on the dyno, we get an average and it's still very safe and the power improvements can be seen.

 

If I understand the goal of your setup, it is to lean the AFR without the ECM correcting for the unmetered air. Is there any concern that your setup could compromise the ability of the ECM to adapt fueling in response to extreme ambient air temps, barometric pressure, or altitude? Is there a risk of rough idle or other symptoms of an intake air leak?

Don

 

I am sure it will be fine the AFM still measures most of the air and it has plenty of head room as the AFR's are still a little rich.