Got my Mina exhaust and pulley done, and tho I am very happy with it's mid and upper range power, it doesn't seem to have that "punch" from a stand still.
Are there any upgrades for this, or how do I go about getting more "start off" power?
Thanks

 

By the way...thanks for the info on the supercharger pulley upgrade.

In response to the low end power improvement, I'm not sure what the perfect solution would be, but I did have that in a recent vehicle.

Until it was stolen, I used to have a 2005 Quad Cab SRT10 Ram Truck with the Viper engine. Sent it out for mods that included supercharger, exhaust, ecu remap and loered suspension. When I got it back it was dyno'd out at 643 RWHP with just 5.2 lbs. of boost. To say the least this thing was a beast. With the 4:56 gearing there wasn't a lambo, porsche or ferrari that could take me from light to light. I destroyed quite a few egos with my 6,000 lb 4 door pickup.

Our Jag's on the other hand seem to be detuned somewhat in the lower end. I find that sometimes when I jump on it taking a corner at lower speeds it actually bogs out like turbo's usually do until they spool up. A true improvement in the bottom end would likely be from ECU work and perhaps ( an expensive option) changing the gear ratio.

Personally I'm not too disappointed with the bottom end, as it seems to have more than enough to smoke off the tires if you turn off the traction control. And if you consider the cost of these cars, the bang for the buck is pretty good. most cars that start with a 5 or more in the HP category tend to go for far more money than these.

I currently also own a 2005 Bentley GT that I had GIAC do the ECU reprogramming. She's pushing around 660 HP at the flywheel but is probably slower than the Jag from 0-120 MPH. In my opinion the Jag is a bargain at 1/3 the price of the GT.

Ernie...

 

Duh, peak torque is detonation limited. It doesn't matter how much boost you try to achieve the combustion chamber can only produce so much bmep before it starts to detonate.

If you overspeed the supercharger you move the detonation curve down the rev range which is why Jaguar didn't do that.

Horsepower can be increased relatively easily with a supercharger (mechanical or turbo) but peak torque cannot be so easily played around with. Usually you can get higher peak torque only by shifting it up the rev range where detonation only comes at higher bmep.

Direct injection engines have a built in advantage due to extensive charge cooling resulting from relatively cool fuel being injected directly into the compressed air near TDC, both the fuel and the ignition can be timed as well. DI is like free bmep, higher torque at lower rpm and higher hp.

Audi's new supercharged V6 is a good example of current limits for street engines: DI, full engine management in 3D and a supercharger which boosts quickly and at low rpm but uses a sort of wastegate technology borrowed from turbocharging to allow overboosting at low rpm without blowing the heads off at higher rpm. Very neat. The DI Jaguar XFR and SC use similar electronic controls I believe. The older 4.2 is pretty basic tried and true supercharging with port injection, by comparison. Hard to improve on Jaguar's engineering decisions.

 

@Jagular,
There is plenty of room to increase torque, guess I proved this, and although I don't have any direct experience with the 5.0 SC cars, am sure there is some too.

@Mafosteel
Guess you may find the solution in the ECU tune, I have no experience yet with the 5.0SC cars, so can’t tell (other than make educated guesses) why this has been chosen.

 

More torque but where in the rev range? The new 5.0 supercharged XFR engine advertises the same peak torque over approximately 4,000 rpm which is impressive.

 

All over the rpm range, from low to end.

Jaguar has cut the peak torque, and flattened it, so by eliminating that you can gain some more low/mid.

 

^^^Avos, how do i cut/eliminate the cut in torque to gain more low end?

 

Speak to tuners that have made a tune for the 5.0 SC cars. You could try to talk to these guys for instance:
http://www.viezu.com/blog/archives/tag/jaguar-ecu

But please note that I have no direct experience with them, only know that some resellers (like Paramount Performance) actually get their maps from them.

 

Supercharging can provide the benefits of variable valve timing without the valve timing being varied, with the right software. Mechanical superchargers produce boost pressure in a fairly linear way. Turbo superchargers do so exponentially. The trick is in the software controlling the dumping of "excess" boost. Variable valve timing allows maximum efficiency in engine breathing over a variety of rpm ranges. So can variable boost control.

By upping the rate at which the supercharger boosts the intake pressure and then controlling the peak boost with a wastegate controlled by an ECU one can indeed increase torque at lower rpm by cutting boost pressure (by bleeding excess off) at higher rpm. Then one optimizes the ignition advance or retard appropriately to maximize bmep at the desired rpm. I think the new 5.0 has some form of variable valve timing also. Jaguar has used two stage intake manifolds and two stage exhaust systems to allow fine tuning of engine breathing.

There's no free lunch though. Changing engine performance from the factory settings will use more fuel, make more noise, require more servicing or last shorter mileages before breaking, create a peakier engine delivery or some other change Jaguar thought was undesirable.

As the CO2 reduction mania and fuel economy obsession get worse there will be more and more scope for aftermarket tuners to ruin the factory engines with their ideas about "better" performance.

 

How can there be excess of boost ;-)
Jaguar doesn’t control boost on these engines (and it’s already relatively low at top boost).
The OP is only talking about relatively small changes, and cheaper lunch than this isn’t available I would say. Fuel consumption is at most marginally affected for these cars if you just go for an ecu tune and faster spinning sc (even on my car/setup). Of course when you want to enjoy the power you will consume more, but that will also be the case for a stock one.
Any car/engine needs to be treated with respect tuned or not, that gives the best chances for longevity.

PS Although I appreciate what a car manufacturer makes, I am even happier now with my setup.

 

The OP has a 4.2SC it appears. Avos - which tuning companies do you like for the 4.2?

 

That changes a bit; as there isn't that much you can get from the 4.2, maybe 20 hp via a ECU tune. I would guess that they (viezu) also have included a quicker throttle response, best is to contact them directly and checkout what they offer.

 

I am going to say the 4.2L is far more limited in reliable, "easy" gains - the 5.0 has .8 more liters and has a DI setup and ONLY makes 50ish more hp stock...

 

I also read somewhere that the XFR's peak power and torque was limited by Jaguar due to concerns about transmission durability. Most likely ECU limited.
I expect the tq and hp numbers to increase as the new 8 speed tranny become incorporated.

 

Unfortunately, mine doesn't have a turbo but it does "bog out" if I'm aggressively cornering. Let me know how it goes remapping your ECU.

 

Hey avos... I contacted Viezu a few days ago when you mentioned them and waiting for a response still. Yes, I have the 4.2L motor from 09. They're in the UK, so I asked about stateside reps that could tune the car.
I've been talking with Singh Motorsports outta of CA which claim to be the best. They work directly with Arden out of the UK. He is telling me 20-20 rwhp from the tune, and he said the timing is off on the ecu due to new 2.5LB boost pulley and performance exhaust. He claims the car will run way better (seems great minus the initial hesitation/lag) and can take out that initial hesitation on the take off. Cost of tune is $995 for the 09 s/c xf.
Thoughts please? Thanks...

 

All sounds sensible, 20 rwhp might indeed be possible, and quicker throttle response is also part of most tunes they do in the uk, and the price I guess is ok, would be great if you could do a before and after dyno.

PS, Arden is German based, and normally they don’t do their own tuning, the price you mention also seems highly unlike Arden…