CALPICO

iTrader: (4)

hey all, i have an 90 TII and I recently took a closer look at the engine while taking off the intercooler today. I noticed that my UIM (dynamic chamber as the Haynes manual calls it) might be from an S4...are there any definite ways to tell the difference between an S4 and S5 UIM? Also, what are the differences...I'm pretty sure the main block and everything else is S5 (hopefully)... would there be any reason the previous owner might have put an S4 UIM on an S5 block? can you mix match S4 and 5 UIM and LIM? I'm really just trying to understand the engine and what the previous owner did...

also, on the back of my throttle body which is modded by previous owner...ugh...there seems to be a vacuum nipple pointing towards the UIM. I looked at the diagrams in the Haynes manual and it seems to be connected to the BAC. But mine is not connected to anything. It does have deleted AWS and all emissions except the BAC blocked off....

Thanks in advance! any help is appreciated

RotaryEvolution

iTrader: (30)

the S5 TII UIM has progressively longer/higher runners as you move one by one towards the firewall. the S5 UIM also has a dimple in it on the driver's side front of the dynamic chamber to clear the intercooler. aside from those 2 things, there is no other easy way of telling the differences.

as for power, the S5 has longer runners which no one has really benchmarked each setup with, i did notice a slight shift from mid range to top end power with the S5 over the S4 UIM but i cannot say if that was just in my head or realistic.

the blocked off line you're referring to is probably the thermowax, which doesn't necessarily have to be hooked up.

CALPICO

iTrader: (4)

thanks for your reply. are the S4 TII and S5 TII LIM/UIM interchangable? as in S4 UIM and S5 LIM. I'm beginning to wonder what else the previous guy might have done to this engine haha

AmT_T

iTrader: (11)

Ur gonna have to swap them as a set, keep the uim and lim together they will not fit on each other but the entire manifold (uim and lim) will bolt right up.

RotaryEvolution

iTrader: (30)

the S5 UIM can fit on a series 4 lower with about 2 minutes and a dremel to the 2 outside bolt holes. my S5 UIM has been atop a series 4 lower for about 8 or so years. i do believe i did port match them also though but the differences were minimal. the S5 has slightly larger runners going into the engine also, so a S5 LIM on a stock S4 block will taper down to go into the engine.

both series manifolds do have a bit of room with the tapers during port exchanges. basically if you look at the irons there is a taper just before and after the flange, same as the LIM to UIM exchange.

CALPICO

iTrader: (4)

ahh i see, thanks for the replies! that definitely helped me out. next time i remove my intercooler, ill definitely take a closer look at the UIM and see what it is...im hoping its an S5 so itll save me some work of buying a replacement and installing it hahah thanks again