Avos I dynoed at 359 with pulley and no other changes. I Don't have bare stock Dyno numbers , I suspect around 10-15 hp gain without the tune due to pulley. Remember that in our cars certain maps must be changed to take advantage of the upper pulley modification otherwise your fighting the ECU trying to keep new boost levels down I would say pulley with proper ecu adjustment alone is 20-25 rwh.
With high flow cats I was at 432rwh and it doesn't look like having the cats gutted have gained anything as I'm still around that number. So the current gain is 73 wheel horsepower. When we got the maximum of 453 rwh that was experimenting and pushing the boundaries a little bit, but decided to dial back down so I am still at around at 430 wheel horsepower range.
As far as the intake restriction: I have measured before the throttle on one side where the part load breather connects and there is a minimum of .6-.7 Psi restriction there with a clean filter, this is with the bottom of my air box cut out, without the cut out it's about .1 higher per side. Correct me if my measurements are wrong but all I did is multiplied that number for the other side and came up with minimum of 1.2- 1.5 PSI restriction overall.
I don't want to go with kn do to lower filtration qualitiy So this is what I'm working on , retrofit from another vehicle, should allow at least double the amount of air flowing while retaining perfect stock filtration quality

 

Hi, I`m a total newby to Jags but treated myself to a 4.2 2007 XKR convertible a while ago and love it , I`m thinking of getting the SC pulley upgrade and the remapping to go with it , I`ve seen what sort of BHP increase I may get but what is that in acceleration terms, ie 0-60mph and 0-100 mph

any feedback would be great , especially if any of you guys have done these mods to your XKRs

thanks Gary

 

Gary,

Save your money and put it towards a 5.0L XKR if your 2007 isn't fast enough for you. Just my

Stuart

 

^ ^ ^ ^ ^
The conventional wisdom in this forum for many years is that if you want more power the cheapest way possible, sell the 4.2 and get a 5.0 //R.

 

I Disagree: from my own experience, as 4.2 with just basic bolt ons and a tune is right there with a stock 5.0 ,even with a tuned 5.0 I would say 0-60 is near identical. My best with tune on street tires was 3.8 sec with 1 ft rollout or 4.05 without . Not many 5.0 xkr or even xkrs can manage those times... Now top end power of the 5.0 is a different story but on street a tuned 4.2 is just as fast

 

Thing is, although you can get extra oomph from the 4.2 with some tricks so you can match the 5.0, you can ALSO do similar tricks to the 5.0 and get that much more.

 

Ah ok, I thought I read somewhere 330 or so as stock, that figure would be more normal for a dual small roll dyno with a stock engine, so I still think the numbers out of this dyno are higher then normal.
I doubt the small pully would already trigger the 1st limiter, I have only seen this with much higher air flow with the panpag ecu.
Its an open system, so .6 is the pressure.
Be careful with sharp tunes, it is tempting to go for high numbers, what may just work for the road may be to sharp for racing (already on 1/4 tracks). For the road one should already use higher octane fuel than what is given as minimum by the manufacturer.

Edit: So for street driving in the EU, minimum go for 98 ron vs 95, and for the US go for at least 92/93 AKI, instead of 85. When racing, go for the highest available for some insurance!

 

It would be nice to see a 5.0 stock xkr on the same dyno to see results.

 

With just a pulley, on a DynoJet single roller (drum) I was also around 360 at the rear wheels and after latest Old Jag tune I saw about 50 HP more and 90 more TQ at the wheels. Since changing cats, full exhaust and intakes I have not taken any more measurements. I use 10% ethanol 98 RON Shell exclusively in all vehicles and one time ran a $150 tank of VP MS100 (105 RON) ethanol free at the track. I still say there are too many variables with dynos or at least most dyno pulls to get a 100% accurate measurement, unless in the same day you can start 100% stock and then do runs with tune and mods back to back. The transmission challenges don't help either. I have a friend with a hub dyno which he insists is way more accurate than a rolling road, I may try that out some time.

 

As for the 5 litre, the TVS blower is more friendly to porting and tunes and increased boost. Going to 600 horsepower or even higher is easily attainable but I personally don't need that much power and need reliability more for road course driving. The 4.2 I feel is a much more robust motor solely based on feedback I have seen on these forums and from main dealers over the last 7+ years. That said I have a supercharged Range Rover 5 litre and a 3 litre Discovery 4 which are basically the same motors (same parts) save of one being 2 cylinders short and they have been fairly reliable other than pulleys and coolant piping failures.

 

Wow, those are impressive results , I`ve had my 2007 for around a year and knew previous owner so known the car for several years so would`t want to get rid for a 5.0L as this one is reliable as hell and runs like a dream

Thanks for the advise and info guys , very much appreciated

 

Avos there are a number of limiters which are related to boost pressure and supercharger ratio , even with stock supercharger pulley those limiters are triggered and even more so with the upgraded pulley.
From what I have seen stock sc 4.2 with 5th gen m112 Dyno around 370 on Dynojet . Either way 73rwh gain Translated into crank is around 86hp and at least that amount in torque, I suspect it's a bit higher.

 

My '07 XKR was just over 340 stock when I put it on a dyno.

 

590 Lb/Ft of torque??????? That's Big Block stuff. OR, was in in like First or Second gear during the run...? Nah, can't be at 190 kmh

 

I would have to agree
, u102768 torque numbers like that you would see in lower gear. My 3rd gear runs were 550- 590 range thats why they were discarded as inaccurate . Stock peak torque numbers done in 4th gear should be very similar to peak hp in our cars as in my Dyno chart above.

 

Ha ha. I think you can safely ignore that scale.

I wasn't very impressed with the company who did my dyno runs. They kept replacing their dyno computer and didn't keep the old runs so I couldn't overlay them and totally changed the graph type and switched from using kW/Nm to bhp/lb-ft half way through my exploits with my 5 litre.

They also weren't able to get a decent run with the car in its current config and actually came up with a bhp number that was less than stock. It clearly isn't as I have gained nearly 9mph in the standing quarter runs compared to when it was stock and over 6mph more than when it had just XKR-S tune, supercharger pulley and XKR-S mid exhaust on so I gave up using them in the end. There are a few more dyno companies in the area and I might try again one day but to get a meaningful comparison you ideally you need to use the same machine as you make changes to the car.

 

Block is from a 4.2 SC but basically everything else is bigger and/or stronger or other way upgraded. I guess this is still not a private forum to talk real power numbers. Our country has it's own rules for the allowed mods and power/weight. Last time there was too smart young inspector who realised that the SC has been changed and he cancelled the inspection. So, we have to go for special inspection with dyno papers and mods done and limit the power to the desired level.

 

dynos are the great lie... different brand dynos give different readings and they can be manipulated by the operator to make you feel happy

 

Yes, that's why just engine dyno should be used or at least hub one. I don't care so much about the dyno numbers. If the car feels like a catapult and goes 9.9 - then everything is fine

 

Sounds like you live in California.