98 xjr. Proud owner, originally came here for help with my 89 xjs v12. Glad I sold it. 98 xjr is more better lol. Anyway. I want to go faster. Is our mass air meter a restriction? I'm almost 100 percent positive it is. Its at least choking off 10hp. Its size in comparison to the throttle body tells me its a issue. I know pro m makes good meters, I know they send a conversion sheet for tuning. Anyone know where to start for tuning? I know of alien tech. But I have no knowledge on tuning ecms, but I have great knowledge on tuning itself. Got the car for $1800 BTW, with only a few minor issues.

 

Do you have the AJ26 or the AJ27 engine ?

Editing

See page 43 and 101

ECU pin EM12 - 13 at 1,2 volts DC at idle as a reference for the base of idling correctly

point 62 circle E is on page 35 to power the sensor at B+ volts DC and not a 5.0 volt DC reference voltage

http://www.jagrepair.com/images/Auto.../jagxj1998.pdf

See file below :

http://www.jagrepair.com/images/Trai...ual-9-5-01.pdf

 

Well, if this helps, as I understand, you can get spray cans of mass Air Flow sensor and Throttle Body and Air Intake Cleaners by using a product like CRC's:


And you should be able to increase your car's performance.

Especially for the Mass Air Flow Sensor, do not use carburetor cleaner, as it will damage it!

Also, don't forget to check the air cleaner.

 

Aj26. Your speaking Chinese. I'll try to read and learn. Looks like a cheat for the ecu! Thanks.

 

****** pebble from hand Grasshopper

 

The 1998/99 XJR are all AJ26.

bob

 

The restriction by the MAF sensor is negligible as it is very short, especially so on a supercharged engine as the supercharger pulls more than enough air for the engine's full power. On the other hand, MAF is a very high precision sensor so tuning/programming another one would be a nightmare. If you want a bit more power and torque, just replace the supercharger upper pulley with a bit smaller one. A 6% upper pulley does not require any ECU re-tuning and runs with the same length belt. This, with a higher cooling capacity aftermarket supercharger radiator and a higher flow electric pump will give you good extra power.

 

There is a vacuum in that intake at WOT. Which lets less air in. And the reduced area of the air meter is about 2". That hurts flow. Found a good thread. https://www.jaguarforums.com/forum/x...easily-119287/

 

A bigger diameter MAF alone will not reduce the vacuum much. Air will just flow faster through a restriction like the MAF. The impediment to the air flow is caused by the friction between the air and the walls of that restriction (the friction, and the impediment, are greater at higher air flow speeds). However, as this increased friction is only along the short length of the MAF, it will not cause any significant impediment and rise of the vacuum.

To achieve a measurable drop in vacuum, not only a bigger MAF but also a few other things would have to be done like higher flow air-filter (the paper filter itself probably causes greater impediment to flow than the MAF), a more free flow intake tube (the friction losses are greater here due to the length of the tube). Then come the exhaust manifolds and tuned exhaust system, possibly higher flow injectors, ECU reprogramming etc.

It all depends how much extra power you want. A 6% smaller SC pulley will certainly give you more extra power/torque than just a bigger MAF. A 10% smaller SC pulley will give you even more but it needs ECU re-programming and also more significantly improved charge cooling. Otherwise, at higher boosts (by a smaller pulley) and stock charge cooler, the intake air temperature will just rise very quickly and the ECU will start cutting the boost (and power) down.