» Site Navigation | | » Recent Threads | | | | | | | Secondary Throttle Delete (mainly for the swap guys...) Published by J!m 04-28-2012 | Secondary Throttle Delete OK Here is something I've been meaning to do for a long time. Delete the secondary throttle. Basically, in front of the 'real' throttle (which is normally closed) there is a secondary throttle, which is normally open. When the ASC detects unequal wheel speed front and rear, the ASC sends a signal to the actuator that closes the secondary throttle, thereby robbing power from the engine until the speeds match again. When it is working well, it is rubbish, so we might as well delete the unneeded throttle all together to clean up the air flow path and shed a pound (or two?). Oh, another bonus: the non-ASC boot (we are now putting in) is actually less expensive than the "correct" ASC boot, even though it is larger. So, if you own the car for a while, this can save some money! This is a simple deal, and should take less than an hour to complete. You need: 5 mm allen wrench 10 mm deep socket 10 mm wrench (maybe) Ratchet 1-inch extension 6 mm nut driver Flat head Screw driver "Boot" P/N 13 54 1 738 757 Hose clamp; 77-84 mm range (get it at BMW so it is not too wide like the US spec. ones are) Another hose clamp, 25-35 mm range (I forgot to look at the size after I pulled it from the box) Start by locating the traction control actuator. It should be next to the air box, on the inner fender. Open the top and remove the cable. Remove it from the secondary throttle as well. Here's what we're up against now: Note: you need to dissconnect the secondary throttle position sensor as well, if you haven't yet. Make sure the key is off (no need to dissconnect the battery) and unplug the air mass meter. Next, use the nut driver to loosen the hose clamps on the intake boot (don't loose the one at the air mass meter end as it will be reused on the new boot ): (continued...) | Tutorial Tools | | | | | | | By J!m on 04-28-2012, 12:59 AM | then pop the clips on the air mass meter: CAREFULLY remove the air mass meter, and set aside: Now you need to remove the idle control valve hose from under the boot. It may be difficult, but do not damage the plastic fitting on the end of the hose. The boot will be replaced, but we can reuse the hose and plastic connector if you don't screw it up... It is hard to see in the pic, but the screwdriver tip is pointing to it. (continued) | | By J!m on 04-28-2012, 01:06 AM | Once you have wrestled the hose out from under the boot, you can remove the boot from the secondary throttle. The large hose clamp at this end will not be used (although I think fully closed it will JUST make it); however the air mass meter side clamp is re-used, so don't loose that one! Next. take your 5mm allen wrench and remove the two allen head bolts on the front and rear sides of the secondary throttle body: You will need the 1 inch extension to get the rear one: Then the secondary throttle comes off easily: Now remove the rubber gasket ring: (continued) | | By J!m on 04-28-2012, 01:16 AM | Now switch to the 10mm deep socket to get the primary throttle body mount bolts. These hold the secondary throttle body mount bracket in place. Although it appears the new boot will fit with this bracket in place, it serves no purpose any longer: Remove all four bolts and set aside for re-use. Then the bracket falls off: Replace the four mounting bolts. Although you could use 5mm shorter bolts, the original ones are fine. They do not bottom out. Be sure to tighten them corner-to-corner and a little at a time. You are tightening into PLASTIC don't forget! Once those are snugged up (don't go crazy on them!) you need to deal with a small problem: plugging an extra hole in the new boot. I used a 5/8 inch dowel (actually a drum stick) to plug the extra hole. I pressed it in (it fits better in the hole you need to plug; the other hole is larger) and then marked it for cutting. Once installed, I tightened a hose clamp on it to ensure no leaks. Any leaks will give you a poor idle... (continued) | Last edited by J!m; 04-28-2012 at 01:39 AM.. | By J!m on 04-28-2012, 01:26 AM | Installed, the plug looks like this. If your's is in the other hole, you have to move it... Tighten the hose clamp on here (a US style one is fine here): Place your new hose clamp (the 77-84 mm size one) on the throttle body end of the boot, and the other clamp on the air mass meter end of the boot: "dry-fit" the hose as you will likley have to rotate the plastic idle hose connector a bit to get it to line up, as well as to get the angle of the boot correct. This is a fiddly bit, but necessary to ensure the life of the boot is not shortened due to engine movement. DO NOT FORGET THE IDLE CONTROL VALVE HOSE and make sure it is fully seated in the boot bottom. This is the worst part of the job. a DROP of silicone lube may be used, but I did mine dry with no issues... Now make sure the air mass meter is in place correctly and the clips are secured. (continued) | Last edited by J!m; 04-28-2012 at 01:42 AM.. | By J!m on 04-28-2012, 01:32 AM | Once you are happy nothing is tugging, mis-aligned or otherwise out of whack, tighten the hose clamps. Note you may need to loosen the air box mounting nuts (10mm wrench) to change the angle slightly. Finally, plug in the air mass meter connection (yes, I know I need to replace the lock nut on the air mass meter connection... It's on the list! ). Finished job looks factory original: Epilogue: I left my secondary throttle actuator in place and plugged in. I am reasonably certain it is not doing a damn thing there. You may be able to unplug the actuator and save another half pound of weight or so, but I am not 100% what, if any, code might be thrown if that is not there. have fun! | Last edited by J!m; 04-28-2012 at 01:44 AM.. | | Looks good. Any seat of pants difference? You get an will get an ASC light on the dash if you unplug that sensor. | | By J!m on 04-28-2012, 01:41 PM | This is not a performance mod per se, rather a removal of un-needed equipment. The throttle body is not enlarged or anything else that might 'increase performance'. If you had a damaged stock boot (as I did) your idle will be improved significantly, and I presume the fuel economy as well, as all the air the engine ingests will be measured. You also save a few bucks on this boot as compared to the ASC boot. I will pull the plug on the actuator today and see what happens... | | | I plan on doing this soon. I've heard rumors that it feels more responsive because the resistance of the second throttle body is gone. Just rumors. Did it feel any better on the butt dyno? | | By J!m on 04-29-2012, 04:14 PM | It does feel better, but the old boot was cracked (which prompted this whole thing). So, yes, it feels 'better' but that could be due to fixing the leaks after the air mass sensor with the new boot. I don't think this should be called a 'performance' upgrade really. | | By J!m on 04-30-2012, 12:54 PM | That looks better than my drum stick! (too bad no one will ever see it) | | By J!m on 05-08-2012, 11:15 PM | I think you could polish the Turner plug, and then lok at it with a mirror every so often to gain full enjoyment from it... | | | Hello-- I have a 98 318ti and have been having an ASC problem. I could care less about having the ASC system work. Your pics dont really look my 98 stock engine. I am having terrible surging at cold, hot, driving on the freeway, in traffic-- and its intermittent. I can do the battery off the post for a night and it goes away the light goes off and all is right with the world-- then I feel the surge, the light goes on and its bucking again. Its just terribly annoying and bad on the mileage-- which is the reason for buying it in the first place! The car has 180k on it now if that matters. It doesn't seem like when I unplug the ASC motor on the drivers inner fender that anything better happens and the ABS light of course comes on. I have taken it to a BMW guy -- which I have serious doubts about-- and I remember on his scanner it mentioned something about the brake light switch being an issue. Is there any way that the wiring harness could do that and a $15 part is kicking my ass? I have a friend with a 02 Accord and the brake light switch did a lot and fixed many issues-- just wondering if thats my problem. I dont want to just throw parts at something. Thanks for any help, Matt | | | | Currently Active Users Viewing This Tutorial: 1 (0 members and 1 guests) | | Posting Rules | You may not post new threads You may not post replies You may not post attachments You may not edit your posts HTML code is On | | | |