It starts with a T and ends in winscrew... LOL

 

I managed to borrow my daughters old Android phone tonight and put Torque on it and that seems to produce more granular results.

Peak logged was 397.58 in second gear or around 437 hp so it might just crack 400 G/S in 3rd gear.

 

Nice!

But you are still recording four parameters, g/s, mph, rpm and then it's calculating the HP

If you did a run with only the MAF rate in g/s it will be even more granular.

So the updated tune has made some difference in the top end?

 

The HP was added to the spreadsheet by me but out of the box Torque seems to log the following and at first glance I can't see a way to stop that:

GPS Time
Device Time
Longitude
Latitude
GPS Speed (Meters/second)
Horizontal Dilution of Precision
Altitude
Bearing
G(x)
G(y)
G(z)
G(calibrated)

I then added the other 3 to see how it coped just logging those. It is handy to keep speed so that you know which gear the reading is from but revs could be left off.

The figures certainly indicate an improvement from the last tune but it could also be that the readings are more granular.

 

. Hmm so judging by the numbers ,high flow cats really don't seem to improve the flow much on these cars. I'm getting nearly identical number with stock cats
Can you turn the tune off and see how much your getting with stock tune? That way it might be easier to see how much tune and cats are adding up separately.

 

Not sure if you saw the thread but I put the car on a dyno before the tune so you can see what the difference is between no cats v no cats + tune.

4.2L XKR Tune – Results - Jaguar Forums - Jaguar Enthusiasts Forum

Unfortunately I didn't get it dynoed stock or with just the supercharger pulley so I don't know what improvements there have been over stock or whether I lost power when the exhaust mods were done but the acceleration is noticeably better now post tune.

I think high flow cats would make some difference but you may get the most out of them with a tune that takes the changes in to consideration because from what I understand both the pulley ratio and exhaust back pressure are used for the volumetric efficiency calculation in the ECU which is how it calculates the expected torque.

 

This is just my opinion/experience, and I may well be wrong (i actually would like to be proven wrong).

I ran my XJR with stock cats, the pulley & intake mods for ages, it always trapped 105/106 mph consistently.

When the cats choked up and I had all those problems, the car lost power.

I put in 100 cell cats, the car got louder, it stunk, but it still trapped 105/106 mph.

Bear in mind the ECU in the XJR is different to what's the the X150 XKR, it does not make a torque calculation so you can make whatever modifications you like (within a certain scope) and it will adapt.

So on the XJR, high-flow cats = no benefit.

Now with the X150 XKR, the ECU is dependent on the calculated torque and any changes to the exhaust, pulley, etc need to be accounted for in the tune.

What this means (to me anyhow) is;

High flow cats without adjusted tune = loss of power
High flow cats with adjusted tune = no difference

Yeah maybe there is a difference, but not enough to be noticeable.

Just the cars are louder.

Which is why in the other thread I was talking about trying 400 cell cats, because I don't want the noise, but I don't want to pay OEM prices either...

 

Results of a AM 4.3 Vanatage with over 40 power runs

Stock - 378bhp
Gt4 mufflers + x pipe mid pipe + 200 cell - 399bhp
As above however catless - 408bhp

 

Perhaps the naturally aspirated engines respond better to high-flow cats than the supercharged ones...

 

It's looking that way

 

Yes My thoughts exactly....

 

Only if there would be a large restriction in the exhaust (and cam design), you could see a difference in the airflow. Now I don't think the stock system is to restrictive, so I wouldn't have expected any airflow differences here.

A sport cat may help to gain about 10 rwhp, but not something that will be clearly showable via airflow into the cylinders. Better flow out would mean less power consumed (ie the possible 10 rwhp extra) to push the cylinders up.

If you have a tune advancing timing about 3 degrees or so, you again don't see any difference in airflow, yet you could roughly gain about 20 rwhp.

So same airflow number with the above adjustments could already have a real world difference of about 30 rwhp, which is why you should only use the MAF reading to check the airflow only if you have made differences in the flow into the cylinders (and with more granular readings ).

 

UPDATE: Must Use correction factor for Density Altitude to figure hp out of G/S MAF
So I went to Vegas over the weekend and did some 1/4mi runs. Best was 13.15 at 107mph (Uncorrected) . During my runs I did have logs turned on as well, and to my surprise my peak MAF g/s was only at 349, which is around 40 less than I normally get at home in San Diego. It dawned on me that just like with a dyno stand, a correction factor must be taken into account for Density Altitude to get proper results. I used this site which has weather info for all tracks and weather info DA Calculator - Density Altitude Calculator - DragTimes.com my calculated Density Altitude at the track was 3500ft which translates into 12.9 at 109mph corrected. I used another calculator http://www.wallaceracing.com/braking-hp.php to figure out loss of hp at that altitude and got a number of 44hp lost, divide that by 1.1 (our previous formula for g/s into hp) =40 lost g/s which once again is astonishingly accurate given that I lost approximately 40 g/s in Vegas

Everyone who posted G/S numbers if you could find DA for your location and time of your test, This would give a more precise hp number. BTW my numbers were all done near sea level 100ft , so that my numbers might actually be lower than most of you who posted.