Hello all, my XJ is finally in the shop for the timing chain upgrade. Since everything comes off and I’m getting the snout replaced as well, I think now is a good time to get the supercharger pulley replaced as well. My only two questions are which one should I go with? I want the best performance. And second, would there be an issue if I ran the pulley on the stock tune for now?

 

Looks like you already have a supercharger pulley from ETG. I do not k now if ETG has a tune for a crank pulley, but Velocity has and I'd be replacing the crank pulley as the OEM has to come off during the guide and tensioner repair.and does more for the tune than the supercharger pulley. IMO

 

That tune and pulley you’re referring to on my car is for my 09 XF SC not my XJ. And I want to run a pulley on stock tune if possible. I don’t want to increase a lot of power as I’m happy with the current amount. Do you think it would be fine to run the crank pulley on a stock tune? Thanks

 

The way I have understood in this platform is that throttle opening is not 1-1 gas pedal to TB blade and it’s all in the mapping and torque values. Therefore there is little results to have from just a SC pulley or crank pulley for that matter. You will also increase blower speed making dragging slightly ever more when not under boost. Also creating added intake charge heat which leads to faster heat soak and could negate any increase in HP due to timing being pulled to stay safe. A smaller pulley should provide better low ene torque assuming the stock tune demands full torque at the specified engine speed. Assuming the intercooler cores can manage the added heat it should provide some gains for the added
boost. I’m not sure data is present to definitively give a gains answer. You could do a crank pulley later as that might provide more reliable overdrive and less chance of belt slip. But there is a 800 dollar difference in price for relatively the same results.

Bottom line do a tune If you want more HP, the pulley just complements the fore mentioned tune.

 

From similar discussions on the F-Type forum you can run with a smaller SC pulley with the stock tune but that will achieve very little and be very poor "bang for your buck", but you cannot run a larger crank pulley with the stock tune for any length of time, not only does it achieve nothing but once you hit 5,000 rpm the car will go into limp mode.
Your best bet is a larger crank pulley plus suitable tune, for example a VAP pulley and tune.
You can fit the pulley then apply the tune a little later, that is what I did, just make sure that if/when you drive it home after fitting the pulley you take it real easy.
The beauty of a VAP tune is that you apply it yourself at your own leisure in your own garage, and you can flash back to the stock tune whenever you want.

 

Interesting about the limp mode on the crank pulley, do we know why? Is it because it’s 2.5lbs vs 1.5 from an upper SC pulley? Does the car think it’s over boosting on stock tune? I can’t see why mechanically speaking why one way creates a calibration issue as they are both mechanical ways of increasing boost. But it’s good you pointed that.

I am torn myself wether to do the upper as I have the snout off the car and just waiting on parts to arrive to complete my repairs. I believe the better choice is a steel upper but that that needs to be pressed on. The Aluminum ones are good for the bake and slip on DYI but not ideal material for longevity and belt slip prevention.

Another point is that the stock tune limits boost electronically, the stock pulley is capable of getting to the predetermined boost levels already, you might fatten the bottom as you reach boost quickly by overdriving but I suspect the stock torque map will eat away the gains via the throttle body, by not opening it fully and contradicting the gas pedal input.

A point for upgrading the pulley while the car is apart is good but with the expectation the tune will follow in the future. I am contemplating this but piggie bank is broke now that I decided to do guides and tensioners.

I am in the original posters shoes.

 

that’s the issue, I don’t want the extra power that comes with a tune. Just wanted a little more lower end torque which I thought the pulley would give me So out of all the tunes available, VAP is the best?

 

Why it goes into limp mode is explained somewhere on the F-Type sub forum by Stuart from VAP, I have searched but sorry I can't find the exact post.
IIRC it's something to do with the crank pulley raising the boost beyond the parameters the ECU expects to see.
This post might help a bit regards dual pulleys: https://www.jaguarforums.com/forum/f...8/#post2195813
Read the whole thread if you have time, it's very interesting (but loooong!).

 

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