thought i read it somewhere - maybe on xk forum.. 11 or 12 psi?

 

 

i doubted it as well. the reason is (and based in rough logic, not exact science) that a 5.0 liter getting almost an entire doubling of atmosphere crammed into it would almost behave like an 8.0 or 9.0 liter n/a engine, right? Again, realizing this is not the exact case or proper way to calculate it, I'd think factory boost level would be closer to 8 or 9 psi, but perhaps someone else will know better.
i just think of all the various v8 american made engine aftermarket s/c kits that take an approx. 350 - 400hp n/a engine and add about 100 - 125 hp with 8psi kits.. seems like that rough relationship with engine size and boost pressure would mean the jlr 5.0 is very inefficient at using boost if it needs 12 psi to do something similar..

 

Boost on the stock XFR AJ133SC engine is 11.6 psi.

 

 

Boost and timing limiting are the 2 most likely means of power limiting. Bypassing is more efficient than throttle limits, on a SC engine.

 

I don't see why that has to be true. It's perhaps more likely that no more air can get in to the NA's cylinders due to their size.

The SC gets more in due to the boost.

 

I think he is referring to the different power levels (470 vs. 505hp) available on the supercharged 5 liter motors.

 

Im strictly talking about the 5L Supercharged variants. They range from 470hp to 575hp with no change in supercharger, pulleys, or anything. The power from what I understand is controlled by the ECU through different models controlling requested TPS vs actual TPS and to a lesser extend exhaust differences. From all my research there is no form of boost bypass as it would be after the MAF which is a no no. I wonder if there is something that controls the amount of air being introduced to the supercharger other than limiting the actual amount the TB is opening through the TPS control as stated above.

 

But if boost on all AJ133SC engines is 11.6 then there is no controlling of boost???? Otherwise the boost would be different for the different 5L SC trim levels.

 

as the foremost non expert, I'd say something definitely has to be different between the various claimed power levels.. lol.
as BigWill said, there are several pathways to do so - all within tuning.
The supercharger's internal bypass just makes the boost recirculate to itself and the engine can quickly consume the remaining boost as soon as the computer determines that there is no need for it any longer. It doesn't discharge to atmosphere like a turbo blow off so i'd say whatever air mass and density determined by the mass air sensors is accurate and still within the intake or already used up. it's a vacuum operated setup in the earlier denso managed cars and an electronic solenoid in the later bosch controlled cars.
what if at all levels of claimed power the cars made the same boost and simply revved to lower levels (hp = torque x engine speed) OR, more likely, the camshaft durations were shortened or lengthened relative to the programmed and intended output of said engine? same intake pressure x shorter opening to fill the cylinder plus mixed to an optimal blend with fuel per the reduced amount of atmosphere should equal a bit less power developed in the burn, yes?
also re: where is the 11.6psi measured? (there is a mapt sensor in rear of driver's side s/c "wing" that is likely the computer's point at which to read the pressure and temp of the intake after pressurization by the s/c) this is not a static pressurization like in a stored air tank. it's very dynamic and constantly changing.

 

Actually boost made by the SC (MAX of 11.6) and boost induced to the engine (variable up to 11.6 by use of a bypass valve) can be different depending on tune, driving conditions etc.



The AJ133SC super charger bottom up, the bypass valve is that gold circle, any time it's open you bleed off boost. 2010, 11 were vacuum actuated, 2012 on are electronic.

And all boosted engines must run some sort of boost bypass or bleed off, if not anytime you let off the gas you'd damage the engine with an over boost situation.

 

Guys, I am getting readings of 22-23 psi boost on the torque boost gauges. I'm running the velocity tune/lower crank pulley and the mina upper pulley.

 

How does it measure it? (It sounds like: wrongly.)

 

Seems a bit unrealistic

 

How does it measure it? I don;t actually know..I assume MAF/MAP and/or a combination of other factors. I do know that it hits those numbers on a regular basis. I will set up a cam to record the gauges next week and post on here.

 

With the engine off and ignition on, what is the measurement shown by Torque? And what does it show at idle?

There are two manifold pressure PIDs in the Torque App, you need to have the right one, and also set the offset correctly.

 

What are we specifically looking for in the torque app to know that the manifold pressure is set correctly? What should our idle vacuum pressure be at idle/ignition off?

 

there is a boost/vacuum PID that I use. At engine off, live ignition..it reads 0...at idle is is in vacuum and at WOT on the freeway I can reproduce boost levels in the 22-23 PSI range.

Curious why offset is need as well?