There is no point in replacing S4 parts with S4 parts, unless it is completely necessary. Fairly simple question, Will the FD throttle body properly function on an S4? If no, im guessin an S5 throttle body will bolt on to an S4..?

 

The S5 TB will "bolt" on to the S4, but that doesn't mean it will function properly. The S5 uses 2 TPS, incorporating a wideband TPS also. I dunno what it takes to work, maybe someone else will chime in..

And the FD TB, you'd want to get the FD UIM also. Not sure if the TB will bolt right to the S4 UIM, but I'd guess no..

 

What is wrong with S4 parts? Why on earth do you have this false notion that you should not replace S4 parts with S4? The S5 TB is identical inside as the S4!

Outside they are compleatly different. I have moded a S5 to work on a S4 but it is alot of work and I have posted it befor if you insist search for it. If you ask this I would asume you dont have the skillz to look it over and figure it out so I would not sugest it. Why b.c you have to take apart the linkage and modify the TPS mounts.

 

The reason i say to not replace s4 parts with s4 parts unless necessary is because many of the S5 parts are better and stonger. Lets start with the brains - Rotors. The S5 rotors are lighter than S4's. S5 alternator cranks out more amps than the S4, FD even more than the S5. 5/6th ports are activated by the air pump on an s5 instead of exhaust back pressure on the s4 (better in my mind). I'm sure the list could go on, but obviously some parts should be replaced with the same one. I wasn't exactly sure on this one.

My problem is 2-4 minutes after i start my car, is spurges/the throttle blips without my foot on the gas. RPM's will jump from 1400-1500, 1350-1450, 1300-1400, 1250-1350....down to about 1050-1150 then sits at 1k and idles between 8 and 9 when fully warm. TPS is fine i checked it the other day. No vac leakes that im aware of. My only other thought is that my throttle body is sucking in air somewhere. My throttle body was cleaned about 4 weeks ago. Any idea on that one?

 

[QUOTE=Mills604]The reason i say to not replace s4 parts with s4 parts unless necessary is because many of the S5 parts are better and stonger.

Lets start with the brains - Rotors. The S5 rotors are lighter than S4's.

--So... S4 is stronger and has lower compression. Most shops when they mill the rotors prefer S4

S5 alternator cranks out more amps than the S4,

--This is mainly b/c of the extra electrical load on these cars with things like a E-OMP so the overall function is about the same in a S5 as it is in a S4

FD even more than the S5.

--Yes the FD alt is good.

5/6th ports are activated by the air pump on an s5 instead of exhaust back pressure on the s4 (better in my mind).

--I would say worse. What if you have no emissions? You remove your air pump what then? Just to much cluttter when not needed. Simply taking care of you 6pi on a S4 is all that is required.

I'm sure the list could go on, but obviously some parts should be replaced with the same one. I wasn't exactly sure on this one.

--Main things that are betor on a S5 is interior plastic rotor housings stat gears and some rear irons but have to consider the different port timings on S5 compared to S4

My problem is 2-4 minutes after i start my car, is spurges/the throttle blips without my foot on the gas. RPM's will jump from 1400-1500, 1350-1450, 1300-1400, 1250-1350....down to about 1050-1150 then sits at 1k and idles between 8 and 9 when fully warm. TPS is fine i checked it the other day. No vac leakes that im aware of. My only other thought is that my throttle body is sucking in air somewhere. My throttle body was cleaned about 4 weeks ago. Any idea on that one?

--Try adjusting the idle. Sounds alot like the fast idle cam adjustments and wax pallet not alowing the linkage to return fully. You are certain of no vacc leaks?

 

No, it won't even bolt on.

Yes, because they're basically the same other than external linkages for the S4's mechancial OMP and the S5's dual TPS's. There would be no point in swapping them, and it would also render your OMP inoperative.

 

you gave some good examples, too bad the throttle body is not one of them. save yourself some headache and just use what you have as there is no upgrade to switching to an S5 and it would be a real PITA to make an S6 one work if it's even possible.

 

a mod some people claim is a little bit benifitial is to use s5 intake manifolds on n s4

you botl the s4 throttle body onto the s5 manifolds to make it work easily though.. emission removal is probably easyer to simplfy things as well

 

Thanks for the replies, I'll replace the thermowax pellet as soon as i can. I doubt it has been replaced in long time anyway. About the vac leaks - i have no loss of power, when warm my idle is steady at 900, about 850 with the rear defroster on. Just when she's cold she will sputter a bit, iv'e been told this is unharmful to the engine and its just something that'll **** you off (yup, pisses me off).

 

If the engine isn't ported switching the S5 UIM into a S4 makes a bit of difference as long as you have the VDI rigged to open properly.

Otherwise the S4 intake has a higher flow capacity so it works better for seriously ported engines.