Matt in Houston: What's your 1/4mile ET? 650bhp has potential to make good numbers.

 

I haven't been to the 1/4 mile track yet to find out. Right now my car is in the garage until Jaguar replaces my CF front splitter and side aero piece that they cracked coming down an alignment rack.

I am tempted to try a few runs at the track, but I will need new tires for sure. Thinking of upgrading the PZero's to the Pilot Super Sports very soon. Maybe I can order them now and have them shipped to the dealer and have them mount them when I go back in for the repairs.

I would expect my times to be in the 11's, @ 120+ MPH. Seems reasonable I think.

 

Sounds good. We need more Jags into 11sec...
https://www.jaguarforums.com/forum/m...andings-84783/ . I have set my long term ( 2015? ) target to 10.Xsec.

 

Best 1/4 mi I have seen reported for stock Xkr-s is 11.9 @ 121. However, most times are 12-12.2. You should defininately be in the 11's if the conditions are ok
Are you going to get 305's in the rear? I'm going that route with mpss when I'm up for tires next. Unfortunately, I got a nail in one of my rear P0's that couldn't be repaired, so I ended up getting 2 new rears p0's a couple mo ago

 

I am definitely going 305 in the rear...they have those in stock. The problem I am having is deciding between 265's or 255's up front. The 265's I want (99Y XL) are out of stock until Feb. 28th. The next option is a 265 SL with a lower load rating but I'm not sure if that will work.

Otherwise tire rack is recommending the 255 (95Y) with 7/32 tread and they are in stock...it has a 1600 lb load rating which is only 75 lbs more per tire than the 265 SL's above.

If those won't work then looks like I will probably wait.

 

Wow...being in the 10's would be very fast. I look forward to the day you meet your goal!

Looks like if I went to the track I have a good chance to be at the top of that chart. Well, at least until you take the top spot one day.

 

I plan on just sticking with 255 on the fronts- don't think there is much benefit from going bigger up front

 

I'll try when I have a few free moments as I'm in Texas on a business trip.

I spoke with the tuner and programmer today and he said he thinks he knows whats happening and for some reason the timing is getting retarded at higher revs as it just feels like its not pulling as hard around 5000. That makes sense as the car just feels out of breath at high revs. He agreed the car should be seeing trap speeds around 125. So a new tune is one the way and we will see how it goes in the next couple of weeks. He also recommended trying a smaller spark plug gap as I'm running a 3LBS pulley and with combustion pressures being higher this may be the case.

 

It sounds scary to be pushing the car on a tune that doesn't have all of the kinks worked out yet... be careful...

 

If anything the car is running super rich as the pipes are black and the car is kept spotless. I may try out another tune as I see Euro-charged has a home tune system.

 

@Maxima,
When your tuner hasn't got rid of all the limiters, the ECU wil reduce power via the throttle blade (they should know if is a tuner). So you could even put a 30lbs pulley on, the ECU will regulate that again back there where it wants it (ie to stock boost levels).


If you don't have the delaer tools to measure, just check the boost level, if it hasn't increased by 3 psi, there are still limiters active, which could explain the power difference you feel.

 

I think that is whats happening as well, as it feels real strong then just slows. The trap speeds are higher then stock but not what you should see out of ~620HP. Plus the soot tells me its running super rich and more so then the typical safety margin?

When you say the excess boost is blown out of the throttle blade, is that located at the back of the engine? I haven't looked at the intake setup so I'm not 100% sure. If it routes around the back that answers the whistling noise I'm hearing above 4K. Think we are on to something thank you!!

Wish I could post the video, wait let me email it to a member who may be able to post it.

 

I hope you get your tune sorted. I am extremely satisfied with my Eurocharged tune but it also is pretty rich. Jerry specifically said the tune was rich and stock-like on the AFR's. My exhaust also gets a little soot on the tips quite easily. If your tuner doesn't come through I would definitely consider them. My car pulls very hard throughout the RPM band and the same day before/after dynos back up my gains.

I am happy to report I pulled the trigger on the Michelin Pilot Super Sports, 255/35 up front and 305/30 for the rear. Looking forward to some additional traction over the PZero's.

I noticed they had a couple different 255's that would work. I went with the K2 Ferrari version that comes with 7/32 tread. They might not last as long but should feel crisper right out of the box.

 

I don't have time to argue with tuners and I'm not risking my 3500 mile engine on one.

Matt who should I contact? Can you please PM me there info and hopefully I can have the self tune kit at home tomorrow. They seem like the way to go as a few forum members have similar cars dynod at over 600BHP.

 

Wish you would have mentioned the 305s, I have brand new pair of Super Sports I'd give you a great price on!

 

@Maxima
It is easy to tune the stock XKR to XKR-S power, anyone with the dealer tool can do this, but also that one has still limiters active. So you might stil be stornger than stock, but you don't reach the power levels with the pulley as it should would it be unrestricted.


There is no boost blow off, the ECU just closes the throttle until it gets ot a max defined torque level. So smaller throttle opening, is less air, so less boost.


@Matt,
Do you know what boost level you have now? That would be interesting to know.

 

Doh!

Oh well, hopefully someone else reading this thread will pick them up!

PM sent with regards to my contact for the tune.

 

No, I don't know my boost levels...but I am fairly certain from looking at my dyno plots that the limiters have either been removed or considerably raised. Traction has become my main area of concern at this point, especially with these cooler temps. Its almost comical.

Maybe I can go by their shop sometime and check my boost levels.

 

@avos thank you for the info its much appreciated as I'm still learning the details of these cars.

Matt , thank you I'll give them a call today!

Oh and if anyone needs brand new pilot super sports 305/30/20 XLs let me know. 500 for the pair, you pay shipping.

 

As I understand it, the ECU limiter is there because the standard torque converter can not (reliably) handle more power/torque. When the 75 came out, it was fitted with an uprated torque converter, and that was carried over into the R-S.

I'm sure the standard torque converter can actually handle more, but manufacturers are conservative because they need to ensure high reliability. So the ECU limits the engine output to avoid stressing the torque converter.

Maybe that can be overridden by changing the ECU software, and perhaps some tuners only change the map rather than the software. I don't know the detail of what elements are software and what are data that the software uses.