What they mean is that the cannot do it via the OBD port, the ECU has to come out, taken apart, and the new file written directly to the processor.

The later cars can be done via the OBD port, which is nice.

Oh and Majik, if you are worried about a tune being "a must" if you up the boost, please ask the guys running >20psi with twinscrews about the tunes they have.

 

Jaguar uses a propriety protocol to program the ECU for the x100 and x103, and iirc pin 13 is the one used to get data to the ECU. Have tried to crack it but didn’t succeed.
The WDS/IDS can of course program the ECU, so all you need to do is to alter the file F27SC074.B68 (this one is for a AJ27, and is located on the wds/ids), and upload it with the tool. Only tuners that understand the denso setup well would be able to tune this file, so very few (especially not the resellers) are able to do this. Just to let you know it can be done.

If you up the boost (and also add additional heat) you must retard the ignition to stay on the safe level. So Eurotek is correct here as from a certain boost level you must do this. The ECU itself is already retarding the timing partially based on the IAT#2 sensors input (and of course the stock pressure/heat), however on the AJ27/AJ26 that is a slow sensor to react, so more care has to be taken with these.

On a stock car you can advance timing a little to gain power, which on the shelf tunes do. Some tunes also lean the mixture a little, which is ok for a stock car. However the rich mixture is also there to cool the charge, kind of an extra help to avoid detonation.

Bottom line, Upping boost and using an off the shelf tune goes against each other, and is dangerous as you can see!

There is some room to up the boost without a tune, and on a car with a twin-screw you can go to about 20 psi, or in other words, the timing and boost go very well together here, meaning no tune is needed as nothing is to be optimized.

I have no idea what the max psi is for the stock (h)eaton setups without a tune as that unit produces much more heat as well, maybe 15psi?

 

With the eaton I would see 15psi on a cool day with the water methanol injection. Similar conditions with the twin screw give 21psi.

The outcome of that STR thread suggests that with reasonable mods (pulley, intake,etc) there isn't a lot of be gained by even a dyno tune on these engines.

The 5.0L responds very well to tuning, but it has an ECU controlled bypass valve, so the tune can also increase boost. On the 4.0 and 4.2L the valve is vacuum actuated and is simply open or closed.

 

I have some 4.0/4.2 SC performance parts for sale at classifieds, including additional ECU for stock/mild modified engines.

 

So the consensus is that I should not waste money or worry about a tune? I'm doing both the lower and 3 psi upper pulleys...along with intake and exhaust. I don't know what the AJ27/AJ26 sensors are, so you kinda lost me there...

Anyone have experience with the Arden additional ECU? There's not much info on their site. I'll pick it up if you guys think it will complement the pulleys, exhaust and intake.

 

I think that is the long and short of it. It was a surprise after I bought the car and found out that there were no "hand tuners" or laptop programs to do any tweaking as there were for my previous car and tons of other cars out there. What is available from shops like Arden and other custom tuners seems like poor bang-for-the-buck. On the other hand a simple pulley swap is relatively cheap and should give you something noticeable.

Doug

 

I bought the ECU directly from Arden, used it with 169mm lower pulley, 200cell cats and catback.
Arden dynod 423bhp from new car with the ECU, cats and catback.

 

I'll say this, after driving my car with a massive intake leak coming from the elbow where it mates to the supercharger, if somehow you could increase the diameter of the intake elbow inlet, and the install a larger throttle body, you could see an pretty good increase in hp. With the intake leak the car has, it feels like it gained a good amount of power, say around 30hp. The accleration is just effortless, and the car just wants to pull in every gear. If in a higher gear at slow speed, the car will just pull effortlessly. As far as the intake leak, I've been posting about this problem on another thread.

Jim

 

I agree about the airflow path. The path seems pretty circuitous to me ending with the final 90-degree bend into the throttle body. My last car had a straight shot into the throttle body that was mounted at the front of the intake which seemed much more direct/efficient.

My impression is that the cheapest bang-for-the-buck with the supercharged cars would be going with a pulley swap. But the bucks go up quickly if you want some meaningful horsepower numbers. I wonder if it is a better route to try and shave some weight off the car?

Doug