Thanks, however this is not a back to back comparison unfortunately,a different intake was used (is extremely important, one of the most underestimated areas I have seen so far here). Next the 2.6H was running at max about 20.000 rpm, vs the 17.000 of the 2.8H, so it was really out of its range. The engine was a 5.8 Ltr version, and the ford engines have much higher lift cams, so they probably breathe easier with the superchargers

Attached is an example from KB website, where you see that the same pressure only yields very little between a 2.6 and 2.8H, ie at 18 psi on 3 rwhp more, but of course the H keeps growing in power the higher the pressure as you can see,
https://kennebell.net/KBWebsite/SC_p...g4.6(5-10).htm

Also attached is a dyno where the 2.8H is compared to a 3.3 Lysholm kits at the same pressure, hence I take it the 2.9 will not deliver more power (unless again you go higher then 25 psi).

I’ll see if I can dig up more info if the 2.8H could deliver me more power, if I find some good evidence the 2.6H is yours ;-)

 

A quote from the article to alleviate your concerns about the inlet (footnote to the dyno chart I shared):

"Here are both runs for the 2.6H and 2.8H. Notice how wide the margins are between the two superchargers. The JLP PowerFlow blower inlet manifold also contributed to the massive gains over the 2.6H baseline, which used a Kenne Bell cast inlet. Remember, the PowerFlow was worth 62 rwhp with a 2.6H on a similarly prepped Lightning truck. We figure the increase in blower size is still easily worth 90-100 rwhp."

Some more information from KB's site on the 2.8LC kit for the 4.6 SVT Cobra:

"MAMMOTH™ Kits.
Up to 119 more HP than even our 2.6H Kit (774 vs. 655HP). Recommended for those looking for the ultimate supercharger with the highest HP potential that will fit under the stock hood. All the features of the 2.6H but engineered to simply flow more air and make more HP than the competition."

I think the Lysholm/KB dyno comparison is a bit meaningless, simply due to the fact they significantly underspun the 3.3 to generate the same boost as the 2.8H. That's like me putting a much larger pulley on your 2.6H to the point where it's making similar power/boost to a 2.1 or 1.7. It's nonsensical, because with a larger SC you get more boost at the same pulley ratio and hence are able to get more power. Even the dyno chart you attached of the 3V 4.6 showed the 2.8H's advantage at any equivalent pulley ratio.

Ultimately it'll come down to whether you run higher boost and make more power using a larger displacement charger. You didn't on the 1.7 and 2.1, so you must've surely gotten used to the 2.6 by now

 

Hold your horses! You’re missing my point, I am not talking about what the maximum power is you could can get at very high pressures (i.e. way above 25 psi), that’s a completely different story!

So to make it clear for my setup, I don’t want to increase pressure, only increase efficiency at the same pressure levels I’m at with street fuel. In addition also keep the best properties of the supercharger like quick pick up in lower rpms and low noise. So comparing different size supercharges at similar rpms is not relevant in this case.

That is actually what I found with the 2.6H for our engines, and I can still boost it up much more by spinning it faster (ie above 25psi), but that’s NOT what I want(ed).

I hope you see now also that the efficiency difference between the 2.6H and 2.8H might be small, but I'm open-minded, if we find dynos that show good enough power difference I would be tempted to go ahead.

 

I see what you mean, I was confused for a second and thought you were saying the 2.6H would make more power on your engine and respond better due to the displacement of your engine which I don't really agree with if you run it as its designed to be. Although I see your point about only wanting more efficiency at the same boost. I think it would just because it'll run cooler and you wouldn't have to spin it so fast for the same boost. Plus you'll have more in reserve when you turn it up on Meth/race fuel.

You can get 700HP from your average performance German grocery getter these days with just a tune and I think your XKR is still hungry

 

A lower spinning twin-screw has a lower volumetric efficiency, so you still need to take this all into account. Attached is a supercharger performance diagram for a 3300 lysholm, and here you see how efficient a supercharger could work in different pressure/rpm ranges. These (and the Whipples) have an internal pressure ration of 1.35, and the H series from KB work at 2.0, hence these ones should only be used with 15 psi and higher. I wish there where graphs available from KB, but never found/gotten them, these lysholm ones are probably very close to a Whipple designs. Unfortunately these graphs shows only a limited area, it would have been great for more insight to see more, i.e. above 2.2 pressure (so above 17 psi) and higher rpms.

Am always interested in increasing efficiency more, however my time/funds have now other priorities which really limits my possibilities now.
The 630 rwhp recorded was with the 2.6H running 15.000 rpm, so there is still 3.000 rpm to go that theoretically with just pulley changes bump the power up to 700 rwhp, but I am more than happy now to have someone else lead the power pack after 10 years ;-).

 

Yeah the bigger superchargers definitely need to be spun quickly, but when you do they seem to show a marked improvement over the 2.6H which I still believe is a great SC for a GT car. The ridiculous power mustangs all seem to use the massive SCs but I think a lot in America run E85 which I don't think isn't as available in EU, certainly not UK at least.

That power from only 15,000rpm is quite impressive, but there's at least two Jaguars in the world which are more powerful than yours. They have been converted to American engines though so read into that what you will!

 

If top power is the only concern (and special fuel not an issue), then there are indeed better options, besides bigger superchargers bigger (non-jag) engines of course.

My comment about leading the power pack is related to being on the front power wise of the jaguar engine/drivetrain (have no interest in other engines, nor comparisons there), every big step in increasing power gave me brown underwear when testing as there was just no reference, so it could have gone caboom any time as far as I was aware. Please feel free to take it further ;-)

 

Yes there's some very powerful Jags running 8 and 9 seconds at over 150mph in the quarter mile, but that's apples and oranges as you say as they're purpose built for speed. Here's a cool one which ran into the 8s almost a decade ago using a 9.1l big block Chevy: Bob English 1967 Jaguar

I personally don't see a problem with engine or gearbox swaps, especially when you've gone to go the extent you, I and others have fitting TS superchargers or even manual gearboxes. But even within Jaguar engined cars, I'm doubtful whether your XKR could beat some of the tuned F types running 10s or low 11s. You've got the power, but it seems the tuned AJ133 cars put it down much better than the TS AJ33s.

 

Without any data, I would say what plays against the “older cars” is gearbox (shifting times/gear ratios), total end gear ratios, weight (possibly weight ratios as well) and possibly suspension, so yeah I may not have enough extra power above the f-types to overcome these weaknesses to be faster on the ¼ mile, but I have never given it a go/test to see what’s possible here, and as there is no other xkr close to my current power levels, there is no data available, so who knows .

My area of enjoyment (besides of course fast take-offs now and then) is mostly in overtaking/accelerating at speeds above 50 kph. Remember the XKR isn’t meant to be a nimble light sports car; it’s a GT, without a back breaking suspensions setup, where I enjoy the elegant cruising with the occasional ability to warp in time when required ;-)

You can’t turn this car into anything else imho, you indeed need to go the f-types, Nissans or porches or whatever, but that is not the type of car this was meant to be nor what I want(ed) it to be.

It’s great to see more enthusiasts making improvements/refinements here whilst keeping the spirit of the car (and most components) where I have an obvious weak spot for power, but I am not religious of what one should or shouldn't do.

Lets see what Badcat's car can do here, no matter what we will learn from it again.

One thing that may need some extra attention on his setup is the position of the air intake right before the air vents, as these actually exhale the heated air from the engine bay right into the intake. I guess the splitter will give some more lower pressure below the engine bay, however I still think heated air will be exhaled due to the low pressure above it, which is not what you want of course.

 

Very honest of you to admit that, I think a 60-130mph etc or accelerating from motorways speeds would play into your advantage but from a standing start I'd bet on a f type, even more so if the AWD version. I hear the replacement for the AJ133 may be a BMW twin turbocharged unit, which represents a lot of potential for tuning again if tuning companies offer turbo kits like they do with current M cars.

I agree that you can't turn these cars into something they're not, or neither should we want to. Although I know I could get an XFR and tune to 650bhp + relatively easily, I think my older S-type has more character and because I've tuned it and made it my own, it would be difficult to replace it after having it almost 4 years.

I too am just happy that a different TS system is being tested and there's another option for us. From my knowledge, TS superchargers including 1.7, 2.1, 2.2, 2.6H and now 2.9 are currently being used on our engines which is quite a nice range. Hopefully you can add the 2.8H to that list and I'll get a nice hike in power some day

 

Any updates on the Whipple project for the 4.2L?

 

 

Some considerable time ago avos made one final offer for kits but I believe that is now permanently closed.