Rossco 0 Posted March 2, 2005 The flap on the bottom of the throttle body where it dumps air (which sounds bloody mental) should it not have a filter on it as its sucking at idle? I know its blowing at any time where its not on vacum but at idle it does suck and its quite a suck, unfiltered air is something i dont want in my lump?? Any theories anybody, dazzer??? Quote Share this post Link to post Share on other sites
W3RKD 0 Posted March 2, 2005 i had this conversation with brian last night.... IT CANT SUCK its allways under a positive pressure. you have problems if its not under positive pressuse on that side of the throttle body. Quote Share this post Link to post Share on other sites
Rossco 0 Posted March 2, 2005 I must have problems then, why would it be sucking in?? It runs super good, any ideas?? Quote Share this post Link to post Share on other sites
stevemac 0 Posted March 2, 2005 Copied from http://www.snstuning.com - _________________________________________________________ You should see 84-104 readings fluctuating with idle. Anything higher than 104 is not right (vacuum leak). Much less than 84 is probably too much timing advance. A pullied charger should not make less than 11.6psi, and even so, thats weak. A Stock charger should make ~~11psi in perfect shape! USA EURO Hg(#'s of boost/vacuum) Comments 15 200 -23.7 55 400 -17.8 90 600 -11.9 - Idle 127 800 -5.9 148 1000 0 (Atmosphere- ala no boost, charger is bypassed) 172 1200 2.9 psi (Your charger is dead or big boost leak) 192 1400 5.8 psi (Your charger is about dead or big boost leak) 211 1600 8.7 psi (Your charger needs new apex strips or big boost leak) 228 1800 11.6 psi (Great for stock pulley, Probably needs new apex strips if 68mm pulley) 242 2000 14.5 psi (Great for 68mm pulley on stock charger) 255 2200 17.4 psi (Great for 68mm pulley on heavily ported charger, hold on to your ass fast!!) ____________________________________________________________ Somebody's gonna have to correct me if I'm wrong here - Look at the boost reading figures for idle speed, the car is on negative boost.. :shock: According to this scale, it must be spinning at a speed faster than idle even to reach atmosphereic pressure. In this instance it would suck air directly from the boost return - no reason why it shouldn't, the air's already been filtered (if the return pipe is still in place). Daz - your picture may well be correct while the engine is giving positive boost, would it also be correct on negative boost - at idle. :?: Quote Share this post Link to post Share on other sites
Rossco 0 Posted March 2, 2005 Copied from http://www.snstuning.com - _________________________________________________________ You should see 84-104 readings fluctuating with idle. Anything higher than 104 is not right (vacuum leak). Much less than 84 is probably too much timing advance. A pullied charger should not make less than 11.6psi, and even so, thats weak. A Stock charger should make ~~11psi in perfect shape! USA EURO Hg(#'s of boost/vacuum) Comments 15 200 -23.7 55 400 -17.8 90 600 -11.9 - Idle 127 800 -5.9 148 1000 0 (Atmosphere- ala no boost, charger is bypassed) 172 1200 2.9 psi (Your charger is dead or big boost leak) 192 1400 5.8 psi (Your charger is about dead or big boost leak) 211 1600 8.7 psi (Your charger needs new apex strips or big boost leak) 228 1800 11.6 psi (Great for stock pulley, Probably needs new apex strips if 68mm pulley) 242 2000 14.5 psi (Great for 68mm pulley on stock charger) 255 2200 17.4 psi (Great for 68mm pulley on heavily ported charger, hold on to your ass fast!!) ____________________________________________________________ Somebody's gonna have to correct me if I'm wrong here - Look at the boost reading figures for idle speed, the car is on negative boost.. :shock: According to this scale, it must be spinning at a speed faster than idle even to reach atmosphereic pressure. In this instance it would suck air directly from the boost return - no reason why it shouldn't, the air's already been filtered (if the return pipe is still in place). Daz - your picture may well be correct while the engine is giving positive boost, would it also be correct on negative boost - at idle. :?: This is my point, i stuck my hand back there on idle and im pretty sure it was sucking??? Quote Share this post Link to post Share on other sites
olly elworthy 0 Posted March 2, 2005 Copied from http://www.snstuning.com - Look at the boost reading figures for idle speed, the car is on negative boost.. :shock: According to this scale, it must be spinning at a speed faster than idle even to reach atmosphereic pressure. In this instance it would suck air directly from the boost return - no reason why it shouldn't, the air's already been filtered (if the return pipe is still in place). Daz - your picture may well be correct while the engine is giving positive boost, would it also be correct on negative boost - at idle. :?: that negative "boost" / vac is measured from within the inlet manifold, the throttle is closed so therefore the engine is trying to draw air in that it cannot have, hence the vacuum, Daz is talking about the other side of the throttle body, when the charger is spinning at idle it is still producing pressure which is vented out of the return butterfly,, as darren says this part of the throttle body is always blowing not sucking,, hope my explanation helps,, Quote Share this post Link to post Share on other sites
stevemac 0 Posted March 2, 2005 Cheers Olly, that explains it fairly well. Logically, that must mean that the ISV is actually a 2-way valve letting air into the inlet manifold to stabilise the idle as well as bleeding air out when too much boost is present ? Quote Share this post Link to post Share on other sites
Rossco 0 Posted March 2, 2005 Yeh olly that does make sense, ill have to investigate and make sure its blowing not sucking (oooerrr). ISV must be a 2 way valve yeh Quote Share this post Link to post Share on other sites
gibber 0 Posted March 2, 2005 Just spray a bit of carb cleaner over it, and listen to see if you engine note changes! Quote Share this post Link to post Share on other sites
Chippie 0 Posted March 2, 2005 It is not possible to be sucking,because at idle,blows all the air from the charger. At WOT, it seals the the hole..... Quote Share this post Link to post Share on other sites
olly elworthy 0 Posted March 2, 2005 Cheers Olly, that explains it fairly well. Logically, that must mean that the ISV is actually a 2-way valve letting air into the inlet manifold to stabilise the idle as well as bleeding air out when too much boost is present ? yeap the idle valve works the same as the n/a vehicles until you have an overboost situation, thats why on the boost return removal kits Daz supplies a small filter for the ISV as at idle its sucking the air in to stabilise the idle. :wink: Quote Share this post Link to post Share on other sites
CoxyLaad 0 Posted March 2, 2005 ummmm, not sure how the g60 piping is routed but on most supercharged cars, the section after the charger and before the TB will run in a vacuum at idle and low revs cos the engine is drawing more air than the charger is supplying, They only start to produce posative pressure around 1500 to 2000rpm ? Thats always how I saw it Quote Share this post Link to post Share on other sites
dubster82 0 Posted March 2, 2005 the way VW did it is to use a different throttle body, as the Charger is always on positive boost, and the engine doesnt require it so therefore it bleeds off through the flap on the throttle body. as soon as you plantt he foot the flap on the throttle body closes and the boost is used straight away. Quote Share this post Link to post Share on other sites
