I must say this is quite a thread. I only wish I had come across it sooner! I have been playing with intake modifications since June, trying various tweaks etc. I have been wanting to do a plenum upgrade, but after recently installing (in my garage) a Spec 3+ clutch, LWFW, IMS replacement, & semi solid trans mounts, I couldn't justify spending another $900 on the aftermarket plenum options right now. I first came across this thread a couple of weeks ago and immediately ordered the required parts from dealer and a used throttle body from Oklahoma Foreign. Came out to less than $275 for shipping and all.
Post installation, I love the upgrade. After disconnecting battery and completeing the circuit between the disconnected cables (reset fuel trims/maps etc), I drove vehicle 50 miles without "hard" acceleration (hard enough to map pedal positions etc though) so the computer could make its adaptations. It was a long 50miles, but I wanted to observe the "butt dyno" without the computer inefficiencies blurring my perception of increases. But then I let her rip. The car seems significantly faster in the 3,500-5,500 RPM range. The speedometer often jumps 4-5 miles per hr at a time in 2nd and 3rd. The rest of the range feels improved as well, but at 3,500-5500 it rockets off. Lower end power had dropped before this mod due to an aftermarket intake, but feels improved now. Stock intake still provides for a torquier low rpm range but I am rarely below 3300 or so rpm so it doesn't bother me at all. LWFW makes up for it on uphill starts.
As I mentioned earlier I have been playing with intake mods for several months trying different things. It's surprising how the smallest change can make a drastic difference. The new TB obviously requires a 50% intake redesign. I have tested everything from modifying the OE tube to ABS pieces routed in all ways possible. I still haven't settled on a final setup but am close. I looked at all the aftermarket intakes out there and saw inefficiencies or some sort in each. I still have to make it pretty but it is pointless until I settle on a final design. I wanted the following things out of the intake:
-no hard 90 degree bends
-smooth airflow surface
-no diameter restrictions less that of throttle body
-100% outside air consumption
Currently, I am still working to meet all of these criteria at the same time. My setup as of now from throttle body to vent in fender:
-Like others I put a specter hose in order to fit new TB (only temporary; I tried the ABS tubing first but took it off after 100 miles because I didn't trust it to hold due to tight areas and "making it fit")
-factory MAF housing removed from air box
-KN Apollo filter with inlet tube extending almost out to vent cover
I Know, I know. You aren't supposed to use oiled filters etc. I have researched this until blue in the face and decided to use one. KN has done extensive research on this and if anyone has the incentive to disprove this and the funds required to perform scientific tests, it is KN. They say it doesn't hurt them and if you think that the oil ruined yours to send it in and let them break it down and diagnose it. I've read plenty of posts from people who used them without any issues. It's a fragile part indeed however I think people are too quick to blame their filter oil. I've got 12k miles on an oiled filter without any MAF issues.
I've come to decide that silicone tubing in as few pieces as possible is the way to go. I put the Spectre piece on while I figure out the best way to proceed with tubing. Any recs on where to find long pieces of 3.25 ID with built in gradually curved ends? Two pieces of silicone tubing between tb and MAF is the best thing I can think of other than having a 1 peice tube custom made (which takes months I think). ABS has good sound but gets too hot with little room for insulation. Spectr flexible tube is too narrow plus it seems the wire ribbing would cause all sorts of turbulence.
I initially used a KN Dryflow filter but replaced it with Apollo for better heat shield fitment. The Apollo has got to go though because its outlet is my greatest restriction at about 2.5". The Dryflow was a little larger outlet but a much larger filter surface area. In retrospect I miss the Dryflow because the idle sounds it produced were intoxicating. It had that low rumble/gurgle of a rich A/F mixture. I have never gotten so many compliments on anything in my life. The Apollo killed that sound. I'm still deciding on the best option for an air filter/box. Any recommendations? I'm hoping to make my 3rd filter purchase the charm haha. I would love to hear input on intake ideas and experiences. I've learned a lot over the past several months and I'm sure others have too. Maybe with our combined inputs we can come up with an ideal intake setup to compliment the throttle body and plenum? Thanks for the great info guys. The tb upgrade is definitely worth it. Almost ready for a tune to make it all work together
Let me know if anything needs clarification. It's late and I have been trying to cover everything on my mind. Hopefully it's coherent and I am not delusional
. gdnite
1994 BMW 3
Daily Driver
Dangermobile
"Bernie" - PONZI that 'made off' with my money!
Hybrid Mode
