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I have just been reading several threads on exhaust fumes in the cockpit with the roof off. Apparently the twin tail pipes either side of the number plate are the worst. They certainly are and I wish I had done my reading before I did my buying! Any tips other than scrapping the system and spending another load of money on a different system?

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6 hours ago, Mike C said:

If you  have a PI, make sure it's tuned correctly and the mixture isn't rich.

Definitely a good thing to look at, when there is poor combustion you can get carbon monoxide that hasn't changed into carbon dioxide, so worth first checking you have no leaks causing the MU to lose vacuum, enriching the mixture. Also get your throttle plates in sync. 

Gareth

 

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The tuning is not a problem. It's running a modern fuel injection system so mixture control is pretty good with pretty clean burning on cruise and only goes rich when giving it some heavy foot. My EGO gauge tells me it's squeaky clean on cruise and moderate acceleration.

I will spend another ÂŁ30 on some exhaust tips to make them a couple of inches longer and pointing downwards and report back. I spotted another possible solution where the pipes were cut at an angle just after the silencers so the exhaust was emitted before the rear valence. Not sure I like that solution so that will be the last option to test before buying a new system. Not even entirely sure that would be legal in the UK.

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I am also interested in this topic. I was checking out the position of the end of the tail pipes on the 6’s at Malvern to see how they would compare with mine.

I have the standard set up, in stainless, but I think my pipes stick out a bit further than a lot of others. I do get a bit of a problem with fumes, which is more apparent with my windbreaker with the windows up, particularly at lower speeds.

Does it actually make any difference, or do you get more or less the same result wherever they are. Would be great to see the results of a 6 in a wind tunnel!

Rob

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If anyone has mechanically challenged TR6 which is burning some oil it should be easy enough to get a drive-by picture of the swirl pattern. Luckily (or not in this case) mine doesn't burn any oil.

This is the pipe style on mine which I think just perfectly chucks the exhaust into the swirl at the back ready to be deposited back into the passenger space. I like the look of the pipes and I think that new downward angle tips will not be quite as easy on the eye, but I can't put up with the stink as it is now.

IMG_1595.jpeg

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I’ve suffered from the fume issues for years even after modifying my twin sports exhaust tail pipes to horizontal outlets. Hood down, the smell is worst under acceleration, thereafter it’s very low but after a trip the clothes and boot smell of fume. As discussed in another thread of mine I plan to change the MU as it’s quite old now. Thereafter when funds allow, the exhaust is going in the bin. 

81549400-E7BD-41CC-94B3-631E29DD81F5.jpeg

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I have twin pipes as described with one either side of the tail.

My solution was to use some adhesive backed closed cell foam tape maybe 10mm thick and stick to the boot lid so it sits on the standard weatherstrip when closed.

Closing force goes up but eau d 6 fumes go down.

Simples!

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An update.

1. I first went over the bulkhead very carefully and sealed any holes. That had not much effect which is not really surprising as I always have the roof down anyway.

2. retuned the idle to run at 14.7:1 rather than 13.5:1 air fuel ratio along with all the cruise area of the fuel map. That had a massive effect on the stink and a significant improvement on the fuel consumption but still not acceptable.

3. I added an extra breather from what was the fuel pump boss on the block and joined both this and the rocker box breather to a catch tank, then the catch tank to each of the 3 air filter backplates. This along with the mixture improvements has pretty much fixed it. I had an hour in her yesterday with no stinky cloths or headache.

So I think it's fair to say that on my car at least it was a combination of breather fumes needing to be burned not dumped under the car and tailpipe fumes which can be greatly improved with better mixture control. I think more generally for standard PI cars, where that level of mapping is not possible because they run slightly rich by design, the answer is to use an exhaust with the tailpipes where the factory intended them to be.

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Good conclusion and update. Also non standard rocker covers don't have the baffle where the oil breather comes out which should help stop oil in the fumes making its way out into the plenum. 

Gareth

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I used a Zeitronix wide band EEGO meter and gauge.

http://www.zeitronix.com/Products/Zt-3/Zt-3.shtml

http://www.zeitronix.com/Products/ZR-3/ZR-3.shtml

 

On mine it's easy enough to adjust as it's just a case of plugging in a laptop but for a standard Lucas PI you would need advice from someone more knowledgable on that system than me.

 

 

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  • 3 weeks later...

 Hi All,

A very interesting thread which may hold the clue to my current fume problem.

During a recent (very poor and disappointing) restoration I had a Phoenix super sport cross box system fitted and now get a much worse fume problem than with my old standard mild steel system.

I notice that my pipes stop approx 8cm or just over 3 inches short of the rear bumper whereas the original system ended flush with the bumper.

Has anyone else got this same system with one large pipe into the silencer but two out to give a sort of original look? If so, could they please measure how far the tail pipes are from the rear of the bumper. My restoration was so poor I wouldn't be surprised if my exhaust was fitted incorrectly.

Would 3 inch tail pipe extensions be likely to help reduce the problem?

Mike C's post about running rich may also be part of my problem. I was told my CR car was fitted with a CP cam during the restoration but I am not at all sure that the restorer will have changed the springs in the MU which I guess would contribute to rich running and the general poor performance I am experiencing. Can I check which springs I have fitted in the MU by removing the top four screws and lifting the lid? I am a bit scared something will go ping and I won't get it all back together.

Grateful for your thoughts

Regards

Les

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I have the same exhaust, if I get a chance to look I'll let you know, mine was running very rich, which I've now sorted. 

You are correct about the springs in the control part of the MU, it is easy to check by taking the top off, also it gives you a chance to see if the diaphragm is intact (if its torn/holes of broken off the mounting screw, it'll run super rich at idle).

Also it's a good idea to test how much vacuum you are getting as later cars get around 12hg early are lower at around 8hg I think and have corresponding springs to match (red - early, black - late, blue - 2500 pi).

Pics show what it looks like taken apart. 

20210820_154411.thumb.jpg.45c430de096bbe7fb0cc131f134daf09.jpg20210820_154416.thumb.jpg.91f598092a539d399f112240968de072.jpg20210820_154421.thumb.jpg.38c5447a32d4c48aa2934635b8f3151b.jpg

Gareth

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Wow thanks Gareth,

That is very helpful and gives me the confidence to lift the lid on the MU. I will be very interested to see what I have underneath.

When you have a moment, if you could let me know the position of your tail pipe versus the rear bumper that would also be helpful.

Excuse my ignorance, but how do I check the vacuum as that might help me figure out which cam has been fitted to my car?

Many thanks

Les

 

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No worries, Les.

Just take a note of what's under the casing, but it's all pretty simple. 

I've used a vacuum gauge on the servo take off hose to measure what I get at idle, badly set butterfly's and out of adjustment valve clearances can affect your readings. 

If I get a chance I'll take a pic and measure my exhaust. Note that I've custom fitted it with a non Phoenix stainless header, but I would think the rear cross box can only fit in the standard position. 

Gareth

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Hi Les,

My son and I went thru this on his 74.  We installed a new SS factory style exhaust but the tips angled up.   This started a long exercise  of chasing down where the exhaust could enter.   

While figuring out your running condition, you might want to look at the condition of the seals around the rear tail lights, reverse lights, all grommet in the trunk pan, any grommets under the gas tank (US models have two both of which were shot)  finally, the grommets for the e-brake cables thru the bulkhead behind/between the two seats (again, both shot)

The e-brake grommets were the toughest to identify - out of sight out of mind, but the small C02 monitor we had kept going off when placed on the driveshaft cover between the seats.  Once replaced the C02 detector hasn't gone off since.  

Like others, our theory was that with all that gas swirling around it could even find its way even up in that area. 

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Thanks Yankee,

I am noticing the problem with the top down, my breezebreaker in place and the windows up so I think it is swirling fumes from the exhaust being sucked back over the top of the car but I could be wrong as I also get a lot of fumes in the boot (trunk).

Talking with Derek Graham (TR6 Registrar) he told me the boot seal should meet at the front (nearest the filler cap) and the joint taped over, but needless to say mine had the joint near the lock and no tape.

I like your idea of checking all the other seals and the use of a CO2 meter.

I recently replaced the fuel tank and had to cut down the foam washers that fit round the drain plugs so will check that area.

The problem has got much worse since the car was 'restored' and the old mild steel exhaust system replaced by a stainless steel one. As I said earlier the SS exhaust finishes 3 inches before the bumper whereas the old one was flush with the bumper. 

Does anyone think tail pipe extensions would help?

My wife refuses to come in the car until this is sorted so I have to do something.

Thanks for your suggestions, it has given me few things to try that I would not have thought of.

Regards

Les

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I use tailpipe extensions on a standard exhaust and it made a big difference when I was on PI.

Tim

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21 minutes ago, Les Pettitt said:

Thanks Yankee,

I am noticing the problem with the top down, my breezebreaker in place and the windows up so I think it is swirling fumes from the exhaust being sucked back over the top of the car but I could be wrong as I also get a lot of fumes in the boot (trunk).

Talking with Derek Graham (TR6 Registrar) he told me the boot seal should meet at the front (nearest the filler cap) and the joint taped over, but needless to say mine had the joint near the lock and no tape.

I like your idea of checking all the other seals and the use of a CO2 meter.

I recently replaced the fuel tank and had to cut down the foam washers that fit round the drain plugs so will check that area.

The problem has got much worse since the car was 'restored' and the old mild steel exhaust system replaced by a stainless steel one. As I said earlier the SS exhaust finishes 3 inches before the bumper whereas the old one was flush with the bumper. 

Does anyone think tail pipe extensions would help?

My wife refuses to come in the car until this is sorted so I have to do something.

Thanks for your suggestions, it has given me few things to try that I would not have thought of.

Regards

Les

These two pictures well illustrate how far behind the bumper the exhaust should be, neither of these cars suffer from fumes.

Stuart.

 

Marko 012.jpg

Marko 065.jpg

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Les, as shown by Stuart and as discussed the exhaust should extend at least to the rear of the bumper. Triumph had this issue when developing the TR6 and ended up having to extend the tail pipes at least 3" on the TR5 exhaust that they used on the TR6 prototype to stop debris being drawn onto the rear of the car and also to stop exhaust fumes being drawn into the cockpit.  They also ended up painting the rear of the car matt black because of the **** being drawn onto the rear of the car.  

Derek

 

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I just checked my Monza exhaust. The four tips are flush with the rear bumper with a 60mm gap between the top of the exhaust and the bottom of the bumper.

I had a severe petrol smell problem , for years I believed the Triumph  included changing clothes and showering after a long run. In the end I had the MU and injectors rebuilt &  recalibrated for other reasons and afterwards noticed that the smell had finally gone. 

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