Hey all,

I am working on my air intake setup and saw that Pro M makes several MAF's that "work " with the 04 xjr. MAYBE ill get some questions answered here:O)

1) How many have done this?
2) Has anyone upgraded injectors along with the upgraded MAF?
3) Tuning Options? Reflesh? Dyno Tune? Any do it yourself setups>

Ive been tuning my own cars for many years from SCT software to Megasquirt. Just wondering my options here.

I realize in the end my mods are going to be limited by my ability to tune (regardless of what anyone says!)

Many thanks

Damon

 

I know of one X350 XJR that has had the MAF changed for a Pro-M style configurable MAF, but it hasn't been documented anywhere online, so I can't tell you much more than that.

I don't know of anyone who's gone for bigger injectors though, the injectors on these 4.2L S/C engines can support 600HP (see Avos posts about the Twinscrew kits) so I guess that's why nobody's gone bigger yet.

Tuning the ECU is possible, it's a Denso unit, has been mentioned a few times here on the forum. BUT the ECU has to come out and be reflashed on the bench, it can't be done via the OBD port, and there's nothing user-friendly like the SCT tuning boxes, unfortunately...

The hardware for modifying the ECU tends to be the Alientech K-Tag, but some other gear might also work.

EDIT

There is one thread here in the X350 section, where a member in Europe had his XJR tuned by "a local guy" and have a look in the S-Type section, one of the guys had his car tuned by Eurocharged.

The S-Type R has the same driveline and ECU as the XJR.

 

I looked at it and quickly worked out you would need a custom tune on the ECU or a device to also fiddle with the O2 signals

Our ECU runs closed loop. The fueling for the injectors is driven from the adaptions primarily shown as the long and short term fuel trims

The ECU constantly attempts to get a 14.7 air/fuel ratio (AFR) and the main way this is done is via the fuel trims.

So if you alter the MAF to fool the ECU signal using the PRO M, the O2 sensors will still read the true AFR. So if the signal is adjusted too far you will just generate a code and get a restricted performance message.

So lets say you reset the adaptions which caused the ECU to run open loop. Yes the PROM will have an effect as you are running from the fixed preset values but once you get to open loop it will be compensated for and have no effect

So you get down to the both the MAF and the O2 need to be adjusted. This can be done by reprogramming the ECU (which I cant do) or altering the O2 Signals. I know there are boxes that can do this but I never go that far

Adjusting the MAF signal alone is not like increasing the boost as you dont actually have more air going in. IE the changing pulleys or adding the twinscrew increases the air going in. This causes the O2 to read a change in the AFR and compensate with the fuel to get the 14.7 AFR. Changing the MAF signal just tells the ECU more air is going in when it is not but the O2 will not see this change and not adjust the fuel

Bottom line you need more air in or adjust the MAF and O2 together

PS you may need another MAF and bigger injectors of you put on a twinscrew that is big enough so that the MAF and injectors are now to small. Also putting in bigger injectors will have no effect either for all the same reasons. Bigger injectors will just have a lower dusty cycle but squirt the same amount of fuel

Cheers
34by151

 

So if I want to tune my XJ8 I have to pull the ecu out your saying

Is there anyone in Australia that can do this would like to dyno it when I have my new diff gears fitted

 

I actually have much experience tuning my other vehicles. If Pro M has the Jaguar transfer function they will just scale it to adjust for the difference in diameter of the pipe. The computer things everything is ok as do the 02's. I PM's Avos about a twin screw kit. I do however want to see what I can do with the eaton setup first. In reality without a limited slip unit I have no idea what good any of this extra power could be! But I always need to make a vehicle mine so to speak. And I like a challenge. And something different..And this project certainly seems to be challenging. I personally don't like having to rely on a shop to tune my car....BIG challenge #1. If it doesn't seam like I need larger injectors for the first round of mods that's great. But Im SURE jaguar was very conservative with the factory tune

 

The PRO-M has an X308 scale, but I'm pretty sure the X350 one is different, but Avos will have the X350 one too, if you ask him nicely

Don't expect too much from a tune, the STR that was done by Eurocharged picked up 10hp at the wheels, and I was told by a local tuner who dyno'd my car that there was about 10hp to be had bad on the AFR's, if you could do the timing and the fuel maybe 20hp at the wheels, maybe.

Not a big enough gain to justify the costs, in my mind anyhow.

 

XxSlowpokexX,

You would only need a bigger MAF or Injectors if they are too small. IE the boost is increased to a level beyond the injectors or a point where the flow in the MAF becomes restrictive.

A bigger injector just squirts more fuel for the same "on time" of the injector. The on/off time is called the duty cycle. The effect of larger injectors will be a lower duty cycle or more "off time" as the ECU will learn and reduce the fuel. This is done by the O2 sensors as they will see the change in the gasses and adjust the fuel trims down so you settle back down to the the 14.7 AFR

The same is true for changing the MAF signal. The changes will be seen by the O2 sensors and the trims adjusted

The starting point is the O2 sensors this can be done by a piggyback or a custom tune but as Cambo indicated its just getting around the edges. The best gains are more boost either a pulley change or S/C upgrade. In the case of an S/C upgrade you may go far enough to need bugger injectors or a bigger MAF as you may reach the limits of what they can provide

Assuming you start with a pulley upgrade the next logical step, without changeing the s/c is a cam change. This will need a lower AFR so your back to a piggyback on the 02 or a custom tune

Hope that helps

Cheers
34by151