lol just google "Big Daddies Garage Mini Cat"

But... and there is always a but...

I got not a single code or CEL on my XJR with the 100 cell cats fitted...and did not have minicats on the downstream O2 sensors.

Hopefully we find out exactly why that is next week...

 

If all goes according to plan in a few weeks I have 2 fitted to my XJR (100cell cats) that I will be willing to part with

Cheers
34by151

 

What link do mean ? .

 

Hello Cambo , I still haven't worked out why it took about 250 kms each time to throw the light on .

 

The upstream and downstream o2 sensors monitor the exhaust
The upstream sensor is mounted before the cats and the downstream after
The ECU does a comparison to determine the cats efficiency and when this is out of range you get a CEL code

By installing 100 or 200 cell cats you have more emissions at the downstream o2 and are closer to triggering a CEL code
IE its more sensitive

The next part is the codes
P0420 Catalytic converter system efficiency below threshold – bank 1 and
P0430 Catalytic converter system efficiency below threshold – bank 2

To throw the code you need to register the fault on consecutive trips

The OBD system defines 1 TRIP as an ignition cycle (ignition key OFF; wait 30 seconds; ignition key ON) plus a minimum engine coolant temperature increase of 22 °C (40 °F) after which, the engine coolant temperature has to reach a minimum of 71°C (160 °F).

So if these 3 things are not met, you get no code

What the minicats do is explained on the website but in essence the gas passing through to the sensor passes through a cat built into the adapter so the gasses passed to the sensor have lower levels and hence you never get a code

Cheers
34by151

 

Thanks 34by151 , that would explain why the CEL didn't come on straight away .
Although mine is NA , the cats did make a noticeable difference .

Cheers ,

BTW , where in Sydney are you ?

 

Ive moved to the Sunshine Coast, thanks for reminding me to fix the profile location

Cheers
34by151

 

So you fitted 100 cells and had no issues??!

That makes me feel better about going to 200, I was just waiting for all my other mods to be complete to move to those cats as I want to remap last..

 

For what its worth , I had the 200 cell before I went to 100 , I f you can go the 100 , do it there is a difference down low .
I was was shown a cut a way view of both cells , almost look the same , certainly didn't go the same .

Cheers .

 

Maybe I didn't do enough trips, but either way watch this space, should have some hard data fort you next week.

 

OK, so we have some news regarding a re-map for the 4.2L N/A engine.

I'm sure mastersid will chime in with his comments as well, seeing as though it's his car, not mine.

Long story short, his car no longer has minicats fitted, and no warning lights / error codes...

Yes we loaded a tune, in order to get rid of the minicats, and try to find some improvements in economy, and power.

Everyone want's dyno results, so here they are, before and after;



These results are only what you get from 3500rpm to redline, dyno's cannot show results lower than that because of the car always kicking down a gear.

Anyhow, it's a small gain in the top end. There could be more by adjusting the fueling in the upper rev range; as you can see it's still quite rich. But from Sid's point of view, he's happy with the overall outcome, and the time/effort involved to chase another 5-10hp is hard to justify, since the car is a cruiser, not a racer. For a cruiser it's more about low-end torque, which you can't see on the dyno.

I'll let Sid tell the rest of the story later, but the major difference is the improvements in fuel economy and low-rev responsiveness, it is quite a different car now.

 

One happy X350L owner ,

Well , If you didn't know before you do now ,

You can improve a 4.2 N/A engine ( to some extent )

The vehicle was driven for 560km's after the reflash was done , enough time for settling in / ECU re learning ,

first of all transmission , distinct change in up shifting , It now doesn't change out of first gear as quick as it used to , particularly on light throttle .

I now seem to be backing off the throttle more than usual in city driving , slightly smoother on take off , the lag on acceleration in neutral when cold is now non existent . Tail pipes show little to no black soot ,

my usual 300km round trip ( Sydney to Newcastle expressway) fuel average at end of trip was 9.2 L/100km it normally reads 9.8 L/100km average , this is always set with cruise control at 120kmh ( Yes I know I'm speeding ) sitting on exactly 1,800 RPM . There is no noticeable difference in average fuel around town.

No fault codes or engine / warning lamps have come on .

Like Cameron said , no real gains in top end performance , but better low down power and fuel economy . In my opinion , dyno graphs before and after looked the same to me , but add up all the little improvements and it does make a difference , I should know , I drive it almost every day .

I probably wouldn't have gone ahead if it wasn't for Nasso --L ( thanks mate ) ,

Finally , I would just like to say If you have never met Cameron ( Cambo ) , he is an absolute Gentleman and a straight shooter true to his word , and I feel very privileged of his involvement in all of this .

I know there are things I may have missed so , if you have questions I'm happy to answer .

This all happened over an eight day period .

What a good forum , if you want to learn .

Sid

 

Thanks for kind words Sid. But I did not do all this myself, I was just the guy in the middle

Might as well put this picture up too:



Well yes, there you have it, if you are looking for peak HP numbers in the top end on a 4.2L N/A, there isn't all that much to be had from a tune alone, could maybe scratch out another 5-10rwhp by cleaning up the open-loop WOT-enrichment, it's still pretty rich up there, but it would be time consuming and ultimately you will struggle to notice another 5hp or so in the top end, it's not that big a jump.

I think a big improvement was already there on this car, in the 100 cell cats and the full exhaust. From my own recent experience of blocked cats on my XJR; stock cats, old cats, blocked cats, whatever, they rob you of power. Maybe you "gain" 5-10rwhp from the cats, but in reality you are recovering hell of a lot more than that, getting back the power that was lost by the old cats that were choking the engine.

If you want more out of the 4.2L N/A then I think it's really the camshafts that are holding it back, the cam specs are quite sedate compared to similar engines that are tuned for power (think of the Aston Martin 4.3/4.7, much higher lift and duration, but overall a much more aggressive engine too, not as smooth or refined) and for the time/costs involved in getting all four cams re-worked, with removal/installation and so on, it doesn't make sense from the perspective of hp per $ on a car like the XJ8L, that's not what they were built for.

The power gains here are lower in the rev range, which is where you get the most benefit in a street car, but it's also something that can only be judged from behind the wheel. The highway fuel consumption improvement is also nice twist.

Just for interest sake, here's some pics of the minicats that came off the car;





You can see that what they mostly do is take the sensor out of the gas stream, acting as a spacer or stand-off. You no longer get gas flowing directly though the sensor. On some vehicles a spacer or stand-off is enough to stop the CEL coming on, but not on the Jags. The difference with the minicats is they also have a small catalyst in there (you can see the honeycomb substrate) and that's just enough to clean the gas & trick the sensor.

But no longer needed

 

Yes Cameron your right , the 100 cell cats on there own made a very big difference to the performance , I think the reflash was the icing on the cake as it now seems to run a little smoother along with all the other improvements .

I think doc was right and I certainly agree with him that a reflash on its own to stock motor would make little difference or any sense for that matter .

If you can't or don't want to reflash , the mini cats did the job in cancelling out the CEL / ENGINE light .

I sent a PM to that special person who made this all possible in the first place and thanked him personally , pity Moscow's so far away !

I wouldn't touch or tamper with any thing else on the engine , after all it's an L series not an R . I really believe it's now running just right :-)

Thanks again mate ,

 

Although the mini-cats do stop the CEL from coming on, they also mess up the fueling, here is an excerpt from the X350 Technical Guide, note the comments about how the HO2 sensor 2 "aids closed-loop fueling control"



So removing the mini-cats is probably the major contributor to your newly improved fuel economy

Might also have a lot to do with the air-fuel-ratio curve looking a bit more normal after they were removed and the different settings flashed to the car.

EDIT

I think this means I won the bet with Dale! LOL

 

As I understand it , in closed loop mode the the H02 1 sensors or as we call them OXYGEN SENSORS , communicate with the fuel injectors via the ECU , so if it's running to rich , the injectors will back off the fuel amount or supply more fuel if it's too lean .

So in open loop mode the communication is broken so as not to lean out the fuel mixture when the engine is cold as naturally the engine needs more fuel when it's cold .

Given if that is the case , I always thought that the H02 2 sensor was not really that critical for fuel consumption/economy .
But like I said , you learn something new every day on this forum :-)

And yes , you did win the bet with Dale as it's recorded on his own Dyno sheets .

 

Closed loop is when the fueling is calculated by the ECU based on the Air-Fuel-Ratio, as determined by the O2 sensors, with the Jags it's both the upstream (before cat) and downstream (after cat) sensors which provide these measurements. Closed loop is when the engine is at operating temperature, and not under too much load. For example while you are cruising on the motorway at light to moderate throttle.

Open-loop would be when the ECU is running off the fuel tables only, for example at wide open throttle or high load, although it's still monitoring various sensors (upstream O2, knock sensors, & others, but not downstream O2) & will react if there is an abnormal condition.

So when you were cruising down the highway in closed-loop, the measurement from the downstream O2 sensors that were fooled by the minicats was not in harmony with the measurement of the upstream O2 sensors, so the ECU responded with a more conservative (i.e. rich) fueling as a precaution because it was getting conflicting information from the upstream and downstream sensors.

By removing the minicats so the downstream O2 sensors can get an accurate measurement, the ECU can provide correct fueling for closed-loop operation. And by disabling only the "catalyst efficiency" function of the downstream O2 measurement, you don't get the codes / error messages.

The open-loop is not really affected by the "false" downstream O2 measurement when the minicats were fitted, as it primarily is determined by the fuel tables, and readings from other sensors.

So to perfect the tune in your car, there is still some tweaking to be done for open-loop / WOT that could release some more HP in the high rev range. This would not have any effect on the closed-loop running of the car, i.e. low-rpm, part throttle, highway cruising, etc. But if you don't need/want it, it's really no worse than a standard tune at full throttle now.

Well that's how I understand it anyhow...

 

Yeah , I kinda thought my understanding was too simple , thanks mate I think I know how it works now .

cheers

 

Sounds awesome guys
I cant say my car gets better economy either after the tune cats O2 sensors map and maff and plugs and then the exhaust X pipe but its a fantastic thing to drive

I absolutely love driving my one had a hesitation at first after going from a highly modified XJR6 thought I wouldn't like the N/A 4.2 but its beautiful motor
and as for economy it might be better if I stopped putting my foot into it all the time LOL
For fun I have my Capri when I get the engine back but that's another storey for another forum LOL

 

Hey doc , after all the mods and work you put into your car who wouldn't put there foot down all the time .

And your right , these cars are a real pleasure to drive .