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MG MGF Technical - TF Exhaust Flap Mod
| Having read several (thousand ?) posts on the TF exhaust flap mod, I went out to my garage last night and carried out 'the operation' on my TF135. It was very simple to do, although it required both arms thrust into the engine bay to undo the connector. Result = both pipes blowing smoke at idle, a free breathing engine with slightly more power and a better sports car exhaust note in the lower RPM band. No obvious disadvantages at all - recommended. |
| J M Noone |
| I'm starting to wonder if the flap in my TF's exhaust is working as it should. I tried this mod the other day by disconnecting the vacuum pipe from the exhaust flap and found it made no difference whatsoever. Certainly I could detect no noticeable difference whilst on the move making the mod totally pointless IMO. 1. Engine off - Mechanical action of flap checked, ie. make sure it was not seized. OK. 2. Engine idling, vacuum hose still attached - Flap remained in it's "parked" position, ie. same as when engine off. When engine revved usual sound experienced. 3. Vacuum hose disconnected - Flap naturally remains in the parked position. Engine revved no real difference in exhaust note experienced. 4. Engine idling, exhaust flap manually moved - exhaust note altered, sounded slightly more sporty IMO. 5. Car driven with vacuum hose disconnected - On the move no noticeable difference in exhaust note could be detected. Admittedly the hardtop is on, but even with the window down and accelerating hard there was no worthwhile improvement in exhaust note IMO. The conclusion I came to was that the exhaust flap mod just did not make any worthwhile difference. If anything it seemed to point to the flap being functional as being preferable. Very odd, unless as I say the flap on my exhaust is not working correctly. However, even if this was the case what I tried in 4. above suggests that the exhaust note would be better with the flap working. =-s Not that this is really important anymore as my Phoenix exhaust arrived today and it will be fitted in about 10 days. Give me a proper sports exhaust anyday! Vrooom VROOOOM gurgle gurgle pop..... :))))) |
| Paul Lathwell |
| I seem to remember that the flap was open to start with and then clanged shut after a couple of seconds of running when the vacuum built up. It used to make a noise like a blowing silencer on that side, not very sporting. When I pulled the pipe off it would re-open but the vacuum would hiss away so not good for the MEMS I suspect! The noise after pulling off the electrical connector is much better at idle and low revs under power and maintains the vacuum in the inlet system, I can also hear when the SO comes home now where as she used to sneak up before! Is this MG's intro to the Dark Side? |
| tony |
| Paul, when you say "parked position" what do you mean: was the flap open or closed? When the control for the flap is disconnected, it should default to 'open' (I gather that someone inside MGR intended that it should be that way - and when the flap does eventually seize up, it would be in the sporty 'open' position! Top chaps!). If when you disconnect the vacuum hose (the alternative is to pull the electrical connector - possibly better to do this rather than introduce a vacuum leak into the system) - what position does the flap go to? In my experience, you should at least notice the increased volume of noise if not necessarily any change in performance... |
| Rob Bell |
| Is this flap on the F as well? |
| AndrewMc |
| Flaps on the exhaust pipe? not on mine mate, just a long smooth curvy pipe with not a lot to slow down the music!! I recommend a large hammer! that's got to come off straight away! |
| Neil |
| My TF (Mar 02) has always emitted smoke from both pipes at idle ... should it be doing anything different? |
| Steve Greenhalgh |
| >> Is this flap on the F as well? << No, with the sole exception of very late MGF Trophy160s Andrew. :o) >>My TF (Mar 02) has always emitted smoke from both pipes at idle ... should it be doing anything different? << Gasses should only be exiting from the LHS tail pipe at idle Steve - but to be honest, I wouldn't worry too much about it! LOL |
| Rob Bell |
| Thanks Rob. |
| AndrewMc |
| Rob, >Paul, when you say "parked position" what do you mean: was the flap open or closed? By "parked" I was refering to it's natural position with the engine switched off. Suppose I should have made that clearer, so effectively in it's open position. >When the control for the flap is disconnected, it should default to 'open' Yup, it does do that. My main point here was that with the engine idling the flap remains open. This is as you'd expect TBH due to the lack of sufficient vacuum at idle - I would only expect the flap to move at higher engine speeds. >If when you disconnect the vacuum hose (the alternative is to pull the electrical connector - possibly better to do this rather than introduce a vacuum leak into the system) - what position does the flap go to? With the engine at idle the flap basically does not move at all - it remains fully open. The only time it will begin to close is when the vacuum increases with engine speed. >In my experience, you should at least notice the increased volume of noise if not necessarily any change in performance... TBH, I was not looking for or expecting any change in performance. It was more a curiosity (sp?) test to see just what difference in exhaust note could be gained. Basically I could detect no worthwhile gain. Now whether this is due to a fault with my exhaust or the difference is just so little I really could not say. My main problem was not being able to observe the movement of the flap when the engine was revved - needed a second person to operate the throttle. As I say though getting a Phoenix system will sort it properly anyway. <BG> :) |
| Paul Lathwell |
| >If when you disconnect the vacuum hose (the alternative is to pull the electrical connector - possibly better to do this rather than introduce a vacuum leak into the system) I knew there was something I also meant to say.... I took the much easier option of blocking the vacuum hose. A 4mm Allen-Bolt is ideal. By far the easiest way of disabling the flap. ;-) |
| Paul Lathwell |
| I asked my normally very good MG technician about this. He asked the factory and came back with the story that it was for drive by regs, controlled by the computer and after about 500mls from a MEMS reset operated the valve to shut one pipe off at low / stable engine speeds. After that mileage it kept the pipes open regardless and thus a free-flowing exhaust. I can't be bothered to follow up/check but might answer why some see a benefit others don't. Anyway, there's nothing on the function/operation on the MGR 'Rave' technical info CD ROM |
| Ian Walker |
| Ian, You mean the the mod isn't needed if ther's more than 500 miles on the clock? Sounds odd as a lot of people have done the mod - and at least some of those cars must have done 500 miles before the mod was attempted. |
| J M Noone |
| Paul, at idle or low speed speeds, the flap should be closed. However, I think that Ian's comments could shed some light on this: "I asked my normally very good MG technician about this. He asked the factory and came back with the story that it was for drive by regs, controlled by the computer and after about 500mls from a MEMS reset operated the valve to shut one pipe off at low / stable engine speeds. After that mileage it kept the pipes open regardless and thus a free-flowing exhaust. I can't be bothered to follow up/check but might answer why some see a benefit others don't. Anyway, there's nothing on the function/operation on the MGR 'Rave' technical info CD ROM " Ian, your source could so easily be right!!! LOL >>I took the much easier option of blocking the vacuum hose. A 4mm Allen-Bolt is ideal. By far the easiest way of disabling the flap. ;-) << Be little wary of using bolts to block vacuum lines: the screw's thread means that getting a good vacuum seal is not easy :o( |
| Rob Bell |
| Assisted in my first TF flap mod over the weekend - very easy to do, but access is a nightmare - we resorted in the end to removing the engine bay access panel, but even then it was tricky. Recommend disconnecting the electrical plug rather than the vacuum hose(s) for the reasons stated above - note electrical plug has a metal wire spring clip to hold it in place, to remove depress the middle fo the metal wire, this puches the side clips out of the way and allows the plug to be disconnected (towards the cabin). There are a couple of other similar clips in the engine bay (2 of them are near the potentiometer), with the access panel removed you can have a play with them to get the technique right. The owner was very pleased with the mod - and it made a bit of difference to the noise fo the car - not hugely mind, but enough to be noticed. Overall, a pretty good mod - benefits are minor in nature, but the mod is free and reversible if necessary. So nothing to loose really. SF |
| Scarlet Fever |
| Rob, >at idle or low speed speeds, the flap should be closed. Hmmm, looking at the design of the flap this all seems a little odd to me and it would appear the opposite should be true... I'm skipping what Ian has said for now BTW... 1. The flap is sprung towards the open position when the engine is switched off. 2. With the engine running there should be a minimal vacuum acting on the flap and therefore little force to pull against the spring. 3. As the engine speed increases so should the vacuum and therefore cause the flap to move more. IMO, and from what I've seen on my own exhaust it seems the flap should gradually close the faster the engine is running, not the other way round. Now this does throw up a couple of questions.... 1. Is my exhaust flap simply not working as it should? 2. Is the operation of the exhaust flap a lot more sophisticated than I would expect it to be. i.e. is the supply of vacuum to the flap regulated and not directly related to engine speed. If I get chance I will have another look at the flap and see if I can suss it out a little more. Running out of time though as the car will be dropped off at the dealers on Saturday for servicing and Phoenix exhaust fitment on Monday. :)))) |
| Paul Lathwell |
| >Be little wary of using bolts to block vacuum lines: the screw's thread means that getting a good vacuum seal is not easy :o( Sorry I meant to add to this. A 4mm screw is a snug fit, the thread was a good 10mm long and the head of the screw also sat flush against the end of the rubber vacuum hose. Although I cannot gurantee a 100% seal I'm pretty certain there would have been a very small leak if anything at all and certainly not enough to cause and problems IMO. Still it was only a temporary test anyway. :) |
| Paul Lathwell |
| Hi Paul, mine used to be open with the engine off and at start-up the flap would shut after a few seconds and it would go with quite a sharp action as if being pulled over-centre. I think the vacuum then just maintains it in this position until about 4000 rpm when the ECU switches a valve to dump the vacuum and the flap opens. I did try this once on the drive but am a bit too sympathetic mechanically to try it again on an unloaded engine! At switch-off the flap would stay shut for a few minutes and then you would get a twang as the sping would beat the presumabley decaying vacuum. Maybe you had a slight leak in the pipework? Interesting about the 500 miles thing as you see loads of older TFs with different coloured tailpipes so maybe it is a newer mod on the ECU. Lets all go out and get Pheonixed - I was following a yellow Trophy the other day with one and it sounded the mutts nuts :) |
| tony |
| >> 2. With the engine running there should be a minimal vacuum acting on the flap and therefore little force to pull against the spring. << I think that Tony's observations are spot on Paul: there is a vacuum accumilator reservoir that is used to control the flap - otherwise, as you quite rightly say, there wouldn't be enough manifold depression to operate the flap at all. This system has some parallels with the servo assistance on the brakes which again use engine vacuum, yet work perfectly well even when the engine is idling... The flap operation is then simply controlled by the ECU, probably in a very binary manner: "0V" flap closed, "+12V" flap open [probably MEMS grounding the earth lead actually]. Well, that's my guess, I've not used a multimeter to confirm this. >> 1. Is my exhaust flap simply not working as it should? << Based on Ian's answer, it may be that your flap is working exactly as predicted! ;o) If Ian's source is wrong, then your flap is not operating correctly, but that is nothing to worry about :o) |
| Rob Bell |
| Tony, What you have reported sounds more like what I expected to happen given what other people had said in the past. I had my car running at idle for several minutes at lunch time and the flap did not move at all. I can only assume that what Ian reported is correct or my flap just does not work as it should. As I've already said though, the Phoenix will be fitted soon (Monday) so this is no great issue for me. :) Rob, I did text you today - not sure if I still have your correct moby number though. Just to say that the flap basically was not moving at any time. Still roll on Monday. ;-) |
| Paul Lathwell |
| Paul, thanks to the technical wonder that is T-Mobile, I only received the text this morning! D'oh! Reply sent... not sure when you'll get it based on recent performance!!! LOL |
| Rob Bell |
| Rob, Ah, the marvels of modern technology. I grabbed a pigeon earlier gave it the reply and sent it on it's. Needless to say it took off, crapped on my car and then flew off in the wrong direction. =oD The question is - who do we know who may be able to find out the all important answer? =-s |
| Paul Lathwell |
| Way |
| Paul Lathwell |
| >> Ah, the marvels of modern technology. I grabbed a pigeon earlier gave it the reply and sent it on it's. Needless to say it took off, crapped on my car and then flew off in the wrong direction. =oD << ROFLMAO ;oD |
| Rob Bell |
| Burp! Pidgeon Pie yum! ;-) SF |
| Scarlet Fever |
This thread was discussed between 11/03/2004 and 18/03/2004
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