|
That's pretty amazing and the fastest 4.2 X150 XJR I've seen from memory. Almost the same mph as a twin screw X350! Well done.
I wonder if matching the 12.3 at 119mph of a stock 5.0 xkr is possible with further mods? Is there a specific reason you're going for a larger crank pulley as opposed to the usual 1.5lb supercharger most have gone for? I'm guessing it's a EAPJ one. |
In simplest terms once the top pulley gets small enough it'll start slipping. Surface area of the ribs x belt tension x friction coefficients = torque. Smaller pulley, less surface area.
|
Originally Posted by JagSTR2004
(Post 1787381)
That's pretty amazing and the fastest 4.2 X150 XJR I've seen from memory. Almost the same mph as a twin screw X350! Well done.
I wonder if matching the 12.3 at 119mph of a stock 5.0 xkr is possible with further mods? Is there a specific reason you're going for a larger crank pulley as opposed to the usual 1.5lb supercharger most have gone for? I'm guessing it's a EAPJ one. The 12.3 @ 119mph was the XKR-S GT, the quickest stock 5.0L XKR i've found was a 12.2 @ 114mph. That shows you how much the 5.0L get's throttled back / torque limited with the stock tune. I think a 12.3 from the 4.2L will be tough, and I have no interest in Nitrous or time/budget for fitting a twinscrew.
Originally Posted by Ranchero50
(Post 1787388)
In simplest terms once the top pulley gets small enough it'll start slipping. Surface area of the ribs x belt tension x friction coefficients = torque. Smaller pulley, less surface area.
|
I have to jump in here. I have numerous mods (take a look at my signature) and indeed they are worthwhile and make a difference in my particular case, some more or less than others. But I really did not notice gain the full benefit of these changes until I was able to do a proper re-map of the ECM & TCM. After several years of searching and researching, mostly looking at what others experiences were here on the forums, in 2016 I settled upon a respected vendor for a tune. For the investment, the result was less than impressive and the tune itself had a number of faults. I gave up, frustrated and angry. Then I came upon Cambo and his tune and the results were both spectacular on paper (dyno before & after) and on the street with a gain of about 80ft pounds of torque. Even with the Quaife LSD, I had to drop the MPSS tires in favor of MPS Cup 2s just to stick to the road on launch. Now the recent latest version I am running is phenomenal and will snap your neck with no hesitation as it propels from 0 to 70+ in seconds. I haven't had a moment to do another dyno pull but everything is telling me incredible gains such as the Sport Cup 2 tires are no longer sticky enough and methanol injection kicks in at lower RPMs and for longer duration than it did previously. Anxious to get to the track for a slip this season. Will post once it is in hand. Also still need to get custom front intake ducts fabricated and further exhaust tuning.
|
Originally Posted by Cambo
(Post 1787420)
The 12.3 @ 119mph was the XKR-S GT, the quickest stock 5.0L XKR i've found was a 12.2 @ 114mph. That shows you how much the 5.0L get's throttled back / torque limited with the stock tune.
https://s3.amazonaws.com/amv-prod-ca...short-take.pdf Maybe they got a particularly good example. |
It seems way too good when you look at the 1/4 mile results from 5.0L XKR owners on this forum, for example https://www.jaguarforums.com/forum/x...vs-tune-76368/ that bloke knows how to drive too...
119mph trap speed is XKR-S territory, not XKR. |
Originally Posted by neilr
(Post 1788718)
Car and Driver figured a 2010 XKR 1/4 mile at 12.3 @ 119mph:
https://s3.amazonaws.com/amv-prod-ca...short-take.pdf Maybe they got a particularly good example. Considering Cambo has run a legitimate 12.6 @114mph in the 4.2 engine variety with no pulley upgrades just a tune,LSD and free flowing exhaust its nothing short of amazing. He's knocking on the door of 5l power. |
Smoked that M5, disregarding the horrible start.
|
Originally Posted by Cambo
(Post 1606096)
I posted this in the other thread, seems like the right place to post it again, given the subject matter.
I had a chat about this exhaust/cats subject, with my ex-JLR friend who writes tunes. Here's what he said; ------------------------------- Exhaust backpressure is very important on the torque based PCM's, i.e. the 2006 onward models like an X150, since this parameter is used to calculate engine VE (volumetric efficiency). So, put in an x-pipe or remove the cats (or install 200cell, 100cell, etc) and the fuelling would be off, because the VE of the engine no longer matches the stock parameters, resulting in high LTFT/STFT %'s. This would limit the perfomance somewhat and/or cause some hesitation in certain RPM/load regions. VE, in turn, is used in the torque calculation (driver demand, calculated indicated torque, which are compared to the estimated torque table in the PCM). In HEAVY cases SOMETIMES it may even trigger limp mode (been there, done that). ------------------------------- And this makes perfect sense to me now, since we had the experience of flashing the factory XKR-S tune into a standard R and it did not make good power. Yet we have also flashed the stock XKR-S tune into other cars that were fitted with the XKR-S exhaust (with the x-pipe) and it made great power. There are dozens and dozens of maps/tables and factors in the PCM of the X150, even things like the supercharger pulley ratio are in there and can (must) be modified. So with an X150, any mechanical changes you make to the car, be it exhaust/cats, pulley's, intakes, they have to be acommodated for in a custom tune. Yes the PCM will adapt somewhat, but it won't be perfect, and in some cases I guess you could even go backwards, if the tune is not matching the mechanical changes. I've never seen any fault codes related to that stuff since I did the exhaust modifications but I guess it'll only log codes if the trims go out above or below a certain range of values... |
Originally Posted by 8bit
(Post 1789888)
Cambo, I've changed the exhaust on my otherwise (effectively) stock 4.2 XKR. I've got an x-pipe mid section without the two small silencers/resonators and I've changed the back box for a smaller one. The information you posted from your contact there suggests that these may be material enough changes to require the ECU software to be adjusted to suit, is that right? Is it a case of monitoring trims to determine if they are now excessive and if so, what sort of values should I be looking out for?
It might also be that with the stock cats, and a lot of miles on them, they are choked up enough to increase the backpressure, and the new free-flowing exhaust is not making that much difference as a result. What I can tell you, is that after changing out my original choked up cats, and putting in the straight through centre section with the x-pipe, the car actually lost a bit of power & responsiveness, mostly in the lower rev range, it just felt sluggish. After flashing in the corrected stock tune (all fuel, spark, limiters, etc stock, only the exhaust backpressure values changed) it felt like a totally different car, and went like one too, that was when it did the 12.9 @ 111.5mph, which was a fantastic result compared to the 13.2 @ 106.5mph it did "stock" prior.
Originally Posted by 8bit
(Post 1789888)
I've never seen any fault codes related to that stuff since I did the exhaust modifications but I guess it'll only log codes if the trims go out above or below a certain range of values...
|
Thanks for the input. The car is showing about 93k miles now so not inconceivable that the cats (stock and original as far as I know) could be the bottleneck here. As regards using SDD to measure the trims, is that possible without the measurement module hardware? If so, can you point me in the direction of some instruction as to how to go about this?
If SDD is a no go without the hardware, I do have the Torque Pro app and a bluetooth OBD2 adapter, I could at least get whatever is presented in standard OBD2 format over that bus. |
Even a cheap OBD tool with live data (elm327 etc) will let you look at trims. £5 and up.
|
I have one of those and yes, it does using Torque Pro. But there are often manufacturer specific oddities with apps that read generic OBD data so I'm not sure if this is one of these, and I need to know what values I'm looking for anyway.
|
2 Attachment(s)
IDS/SDD gives you a much more detailed view of the fuel trims in the 2006MY onward cars.
Attachment 205595Attachment 205594 Note that in the 2nd pic a lot of data is missing because the car didn't do enough miles at that time after the PCM had been reflashed (which cleared the adaptations) |
Thanks Cambo. Do I need the measurement module hardware for that? In either case, is it just a case of reading the values, or should I clear the adaptions and do some mixed driving for a couple of weeks and read the values after that?
|
No it's just read over the OBD port, with a VCM, DA-Dongle, etc... you do not need the VMM for this.
If you clear the adaptations it does take a while for the re-learning to be completed, when I took those pictures i'd driven 300km since the reflash, and they were still not complete... |
OK, I changed my MAFs a couple of months back (maybe 300 miles in that time) but I didn't think to clear adaptions back then. I'm not an expert but I'm not seeing anything in those screenshots to say that the relearning is complete, or is it not shown there? Is it a case of covering a certain distance after clearing adaptions?
|
You see the black boxes in the 2nd pic of the LTFT's, it's not recorded any values yet.
|
OK thanks, I'll look into this, cheers.
|
Originally Posted by tberg
(Post 1605731)
I've had the pulley, tune, and a slight exhaust mod done, and I'm not sure there is much noticeable or usable gain. It's not thousands of dollars, though. Several of the tuner companies have run specials for well under a $1000 dollars, and the X pipe addition with the center resonator removal cost me $280 including the X pipe and installation. So, altogether I spent about $1100.00. The X pipe/resonator removal mod produces a great, subtle growl and was certainly worthwhile. The rest is more about ego.
|
| All times are GMT -5. The time now is 06:33 PM. |
© 2024 MH Sub I, LLC dba Internet Brands