s5 intake on s4 - need backpressure?
 

hi, im thinking about putting the s5 uim + vdi section on my s4 block as icemarkand a few others did.....

i was told you need the airpump to run this setup, and the s5 aux ports are controlled by the airpump....

so if the s5 uim + vdi are put on an s4 block with airpump, do you still have to worry about backpressure to open the ports?

if so, is there a way to eliminate the need for backpressure on an s4 block.

and the last question......if this is accomplished, and the need for backpressure eliminated, would the best flowing exhaust, be the best?

Re: s5 intake on s4 - need backpressure?
 

Correct.
No. It's one or the other, not both.

thanks, the s4 airpump will do this fine?

^

anyone?

Correct the S4 pump will work fine. I recently did this swap while installing my LT-8 last weekend. However i wired open the VDI and removed the 5th/6th sleeves from the motor. So i did not have to keep the Air-pump. I've also removed ACV, BAC, Cold start valve and secondary plates in the Throttle body.

You'll need a diegrinder to remove some casting from the rear iron. You'll also need to run a S5 TB or die grind the bottem of the S4 Throttle body. IIRC you'll need a LIM too.


Good luck, you'll be happy with the upper RPM results

-Markus Reschny

well im leaving the s4 lim, and just port matching there.....

doesnt removing the 5th/6th ports + wiring the vdi totally kill your low-end torque?

i've got our S5 ports wired open as well as the VDI. Torque loss is hardly noticed as there is not a whole lot to lose anyways. I did this cause our air pump bracket kept breaking and i got tired of looking at the emmisions crap and air pump finally. Soon the port sleeves will come out , and VDI.

i have pr sleeves installed (kevin landers loctited the shit out of them and guaranteed they arent coming out)........

will these have any affect?

almost the same as removal....removal for me is just a piece of mind that the wires don't come off and the sleeves accidently close. Just piece of mind of 1 less thing to go wrong.

hmmmmmmm there has to be some major drawback to this....if this mod will truly add 10-12 rwhp.....i'd guess it'd be more popular since the parts are like $50 to do this.