Exhaust backbox. - How to change

7 years 9 months ago - 6 years 8 months ago #380 by cjj
I bought a nice shiny stainless steel Daytona



With quad finishers.



Once you have your new exhaust the first thing to do is choose the worst day you can to fit the exhaust.



Well actually, I got P'd off waiting for the rain and snow to stop. Been waiting for days. So I found a use for the extremely large tarp' that I bought in a Halfords sale (knew it would come in handy).

Reversed the car up onto the ramps and erected the makeshift cover. That and the 1Kw light kept me dry and warm.

So first I soaked my nuts in penetrating oil, then I thought I better get on with the car. ;)



This is the other joint (back box to Cat). I decided to leave this one after I discovered all the nuts were well and truly seized.



The easing oil didn't work, so I ended up drilling down the side of each nut, hitting with a cold chisel, hammering a socket on and then relying on brute force. It did the trick.

A lot of people just grind the nuts off, but there is very little space and I forgot to buy some discs



It is well worth removing the O2 sensor from the Cat pipe at this point, if you can. I couldn't. It was well and truly seized on.



Here is a better view of it. It is a 22mm nut but there is hardly any room to get any weight behind the spanner.



For these reasons I unplugged the sensor up just beside the ECU. You need to unplug it and then disengage the socket from the metal bracket (just pull it upwards with a bit of force), which allows the cable to pull through to the exhaust. This allowed me to use a lot of force to remove the sensor once the exhaust was removed. Spanners work much better when you are standing on them.



Once this is disconnected and the 3 nuts are removed it is a case of separating the flanges (you need to bend the lugs from the bracket that holds the backbox strap in place). Once the flange is separated you need to unbolt the backbox offside hanger and remove it.



And then, using a suitable lever (I used a hammer handle) remove the hanger from the rubber.



Also, remember to remove the vacuum pipe from the exhaust emission control valve on the offside exhaust pipe. It is just a rubber push on (or pull off) connection.



Once the hanger bracket and the vacuum pipe to the valve are removed you can slide the backbox towards the nearside of the car and disengage the second hanger. The backbox and cat can now be lowered to the floor and removed.



Remove the hanger bracket from the new exhaust



And push the new backbox into place on the nearside hanger.



Now push the offside hanger into the rubber hole and bolt onto the backbox. This will hold the backbox in place.



Now that the backbox is taking its own weight, you can bolt the sports cat (or decat) pipe in place. It might be worth attaching the O2 sensor back on the new cat at this point. I didn't and it was a pain to do in situ. A soft metal gasket fits between the cat and the downpipe and another between the cat and backbox. Some people like to use exhaust paste as well. I haven't bothered as I wanted to see how effective the gaskets were. Insert the 3 bolts at each flange and add the nuts (Copper or stainless are best if you want to get the thing off next time. Don't forget the bracket for the strap (I did and had to take the nuts off again) at the downpipe end.



This shows the strap and bracket on the old exhaust.



and the new one



Once everything is in place tighten the 3 flange bolts at each end. Then place the strap around the backbox and bracket and tighten that into place (just like a big jubilee clip with a bolt instead of a worm drive).

Now that everything is in place you can fit the finishers which just slide over the exhaust pipes. I went for the quads but there are ovals etc.



Make sure that they sit centrally in the bumper holes otherwise they may knock and/or melt the bumper.



Now you can tighten the finishers in place with the supplied U bolts. I later changed these for some stainless steel exhaust clamps.



Last thing to do is block the vacuum tube (I used a self tapping screw) and tiewrap it safely out of the way.



You should also remember to refit the O2 sensor plug back onto the bracket and reconnect it.

Check all of your connections are secure and take it for a test drive.

And for those of you who said this was the inoffensive exhaust, I would hate to hear the Miltek. Sounds nice though, and seems to pull better. Just feel sorry for the neighbours when I leave for work at 6am on a Sunday morning.

The setup that I have fitted is a Daytona backbox and a Janspeed sports cat, all stainless steel.

I forgot to mention at the beginning, but if you are working under the car make sure that you chock the front wheels for safety. A pair of safety glasses or goggles are worth the expense as well (got mine free).


After taking it for a test drive, the whole backbox shifted to the offside. Re centered it, but it shifted again.

As there was no adjustment I used a small jubilee clip as a stop on the nearside hanger to stop it moving. This seems to have done the trick.

The following user(s) said Thank You: Leigh Ping, COMMANDER

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7 years 9 months ago #381 by cjj
Here are some pics of the finished exhaust.







The following user(s) said Thank You: Leigh Ping, bandit, Fatbaldingoldgit, COMMANDER

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6 months 2 weeks ago #174933 by graham1
nice job. with not owning a MGTF before I was wondering what the rear off side pipe was hanging with a small bolt pushed into it, will have to try and tie it up somehow, but does this have any negative feed back with MOT??????.thanks :broon:

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