Hi all. I’m thinking of fitting a powerhouse 10% supercharger pulley to my 2009 4.2 XKR. Has anyone on the forum fitted a 10% pulley on their car then regretted it?
Thanks, Gordon.

 

A pulley without a tune is money into the intake and out the exhaust with no benefit.

A few guys in here may be willing to help you out with a tune, however.

 

https://www.powerhouse.uk/content/ja...er-pulleys.php

My Indy has advised me to go no greater than 6% on my 5l and they are fitting a custom SS 'bolt on' type which are easier to service/remove.

My car already has a 7.5 ali pulley fitted, since this was done prior to my ownership I can't really compare to stock.

As CJ has said a waste without a tune (and zaust mods if yours is stock) there's no point.

Good luck

 

Thanks for the advice, I hadn’t realised that a tune was needed. I’ll look into it.

 

I don’t believe is tune is “necessary“.

The pulley will spin the supercharger faster so it will pump more air and the ECM will provide more fuel so you should be seeing plenty of new power. The tune of course will try to extract more power by adjusting things like the fuel tables and timing and torque management
But the pool alone will give you some horses

 

Any time air, fuel or spark are modified, the ECU needs to know what to do with this modification. It doesn't already know the requested parameters, so it guesses.
Just a pulley MAY give you a pony or three, but that's not even worth five bucks. Lose ten pounds of body weight instead, it'll have the same result.

 

So just like the ECU increases the fuel levels by adjusting the fuel injector duty cycle when there is a vacuum leak, it would do the same when the supercharger pumps more air into the cylinders when you spin it faster with a smaller pulley.

Do these engines resort to a preprogrammed fuel map at WOT? If the ECU uses a preprogrammed fuel map at WOT, does the ECU monitor the O2 sensors at WOT and modify those fuel maps if it sees excessively lean conditions?

I thought the it starts with a base fuel map which gets adjusted using the STFT's and LTFT's based on O2 sensor readings......

In SDD, I can look at my fuel trims across the RPM range and Various loads and see the adjustments the ECU made so it does modify the tables based on what it sniffs from idle up to some high rpm range

And I thought the reason people see more power with a programmed ECU is because the programmer can push the limits on things like timing and mixture to increase power over the stock baseline. For instance instead of staying with a factory 30 degree advance max, the programmer can bring it to 38 degrees. and instead of trying to get the mixture to 12.1 AFR the programmer can change it higher or lower for max power.

 

Im not sure how many times I have to repeat this: at least on newer 4.2 cars Yes you do need a tune for a pulley unless you want to have marginal and minimal benefits, but to each their own. I don't just throw theories around like some for what will work and won't , but actually test , track, dyno results. Dyno and track times are in my threads.. And to your AFR and timing theory, on these cars there are dozens of various torque limiters alone, and many other maps I won't mention that must be adjusted besides just timing and AFR. It's a bit more complicated than just timing and AFR, like a lot more
To the original poster , proper remap will actually allow boost and power from the pulley to be used to full potential. Even with a stock setup power limiters can be hit and for sure with a smaller pulley. Potential gain from 4.2 later cars is 75% in the tune and 25% in hardware modification, so even on a completely stock car there is a huge gain with ECU tune and small in comparison from pulley and exhaust mods. Pm me for details..

 

Over and over and over as long as we continue to bring on new members the same questions will arise. Alex please keep answering queries as some of us are slow learners.