I just installed the PowerHouse lower pulley supercharger upgrade on my 2000 xkr and oh yes, the low/mid range acceleration is quite impressive! I would agree with others who said it feels like the engine has an extra liter. Been testing for a week and no issues.

I had previously installed the Mina cone intake kit but kept getting "too lean" error codes so reinstalled factory box (I kept the aluminum intake). But with the new boost upgrade I'm revisiting how to improve upon the restricted snorkel of the intake box. I'd like to keep the original box, but am thinking of drilling a few holes below the snorkel, so facing the wheel wall, hoping the air stays cool there. But, I'd also like to add a spring door or thin rubber flap so that the holes are covered unless the vacuum is strong enough to open - that way using the snorkeled air most of the time and the extra intake mod only when she needs it. Has anyone heard of anything like this? Seeking suggestions and feedback. Thanks!

 

I’d advise against drilling any holes in the air box which are open to the engine compartment. The air temp under the hood, even by the wheel well is going to raise the temperature of the incoming air charge and negate the benefit of your intercooler.

if you have evidence that the engine is actually starving for air, then make a new larger connector that goes to the wheel well, where the air is significantly cooler than the under hood air.

it might be instructive to examine the air intake of the Ford Lightning Pickup. It uses the same supercharger as the Jaguar, but spins it to a higher boost level. The Ford engine also has a higher displacement than the Jaguar .

Z

 

To my knowledge, you are describing the stock XKR air box. There is already a trap door that opens under acceleration as-needed. There is a solenoid that sometimes fail, but it is sort of all already there.

 

I don’t think the 4.0 XKR’s have the trap door air box. Maybe just the 4.2’s.

I might have missed it, but don’t recall seeing one when I had my box off. I’ll check again on that.

Z

 

As per the electrical guide the "Air Cleaner Solenoid Valve" seems to appear for MY 2003. Maybe procuring one of those and retrofitting it to the earlier model is the way to go. The solenoid valve would have to be activated with some form of custom controller. Or maybe off the circuit for the secondary fuel pump.

 

I don’t think the 4.2 XKR’s have 2 pumps, just the 4.0’s. But the one 4.2 pump is very pricey. Much more than two of the 4.0 XKR pumps.

As usual, I could be wrong about that too.

Z

 

Yes, no trap door in the 4.0 XKR, which is what I have. I don't have any way to control a solenoid if I were to try to fit a 4.2L air box. I'm basically trying to mimic the idea using vacuum to control a spring loaded door or rubber flap.

 

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You may be putting the cart before the horse.

I’d want some definitive data to show that the engine was starving for air before changing the stock air flow arrangement.

Yes, aftermarket supercharger pulleys do increase power. But I haven’t seen any hard information showing the stock air box can’t still provide the needed air flow. There are a lot of folks on the forum who have the different pulleys installed. But I haven’t read of anyone needing to modify the air box to fix an issue.

of course I might have missed something.

Z

 

The only evidence I have is the intake snorkel from the wheel well feeding the box is smaller than the rest of the intake pipe. And, with the larger lower pulley I'll be pulling even more air at higher RPMs. Seems intuitive the factory intake snorkel is a choke point but I could be wrong.

 

it could be a choke point if it keeps the engine from getting all the air it needs. Your fuel trim numbers will show heavily too rich if that is the case. And the engine will be sluggish at the high revs.

Remember , these cars are not sport cars designed to run on a track or highway at maximum rpm continuously. They are GT cars that can be happy putting in long hours at moderate rpm in relative comfort.

A lot more than pulleys will need changing to make these engines reliable at continuous high rpm.

just my opinion of course,

Z

 

I have had the larger crank pulley for several years and have never had the motor starved for air.
Not a street racer but do give it some serious pedal on occasion.

 

Very good point. I'm not really concerned about running at high RPMs for extended period, the boost at the low to mid range was my original objective and that has been met with the pulley upgrade. I think I'll just leave it as is and keep an eye on the trim numbers. Thanks

 

Great to know you've been happy with the larger pulley and not had any issues. I'll leave the factory box alone and enjoy the extra pep at the low/mid range. Thanks

 

That is why I was suggesting possibly driving that air box solenoid off of the secondary fuel pump circuit somehow. I believe the secondary pump is activated only under high rpm/load, i.e., when there is more air going in, and might overlap nicely to drive the solenoid. Just an off-the-cuff thought.

The context is that when Jaguar increased the displacement of the engine by 5% (4.0 to 4.2), the engineers with all the data somehow convinced the accountants to spend money on this trap door for extra air. It would stand to reason that if your pulley pulls in, say, 5% more air in, upgrading the air box makes some sense.

Best of luck, keep us posted.

 

Opening up the front right of the airbox pulls air from factory locations and at idle is the only time heatsoak could be present in that area. Besides, there is an intercooler so a slightly higher intake temp is inconsequential. This is definitely a supporting mod because by itself is not a substantial difference.

On a completely stock XKR 4.0 with the front right of the airbox cut off, removed the snorkel from the inner fender and added a K&N filter in preparation for the lower pulley, datalogging showed marginal gains and aside from a slightly quicker throttle response there was no noticeable difference. After the pulley install the K&N was swapped for a paper filter and the reduction in power and throttle response was noticeable, it is likely the opened airbox makes a difference at the higher boost levels.

 

I'm so happy you know about the XKR air box flap. I've had a hard time finding anyone or anything with info on this. Many parts places don't seem to know they exist.
So how do i know if mine is operating correctly? After I first opened my 2004 XKR airbox to check the filter, I have a slight but very noticeable to me, hesitation on a medium acceleration. Somehow the tiny supercheap spring had come loose on the flap after my actions. I fixed it but still have the same problem. I've cleaned, and replaced tge MAF, removed the full plastic tube to check fir a crack up to the throttle body and found none. So I keep coming back to this flap. Do you know how to test, measure, check that flap for proper operation? Thank you.

 

I had the same question when thinking of how I would measure the effectiveness of a rubber flap or spring door mod to the airbox. I was thinking I'd secure a GoPro in the box with a flash light and take it for a spin. Never tried it of course.

 

I checked out the Ford Lightening intake box and the snorkel looks 2x larger than the 2000 XKRs, so it does seem the engineers undersized it for some reason.

.

 

What is a go pro? Flashlight? some kind of camera?
My flap is actuated by an electric soleined. There must be a way to test, 1. The solenoid is properly responding to the current applied, 2. that the current is applied at the correct time and voltage.