How to install a 3 inch exhaust system.

"Installing a new exhaust system, how hard could that be ?" you might ask. The answer is that it's not hard at all but to get it right on the first attempt you would have to be very lucky, or having read this piece of information.
This info is based on installing the 3 inch Mongoose exhaust system onto a 1992 For Escort RS Cosworth but it might be helpful with other makes of exhaust systems too.

So, here's how to do it in a few easy steps:

1. When you have received your new exhaust system or brought it home check that it fits together easily. A very smart thing to do as the ends that slides into each other could easily be bent out of shape and not being circular as they are supposed to be. It will be much easier to find out before you mount it on your car than afterwards. If it's a little bent just bang it till it fits. If it's a lot out of shape bring it back and exchange it for a part that's not damaged.
2. Remove the old exhaust system in this sequence: Loosen an remove the clamp that holds the downpipe from the turbo to the middle section. Remove all the rubber grommets that holds it to the car, starting at the backbox. Remove the last grommet that sits close to the downpipe-junction and slide the system out of the rear bumper. Loosen the bolts that holds the downpipe to the turbo, loosen the front stabilizer bar clamps from the chassis and slide the downpipe out from under the car. It might work to take it up through the engine compartment too but I thought it was too cramped up there and wouldn't risk destroying anything..
3. Slide the new 3 inch downpipe up to the turbo and fit 3 new all metal locking nuts, do not tighten yet. Refit the front stabilizer bar clamps to the chassis and tighten to 70 - 90 Nm.
4. Slide the rear silencer through the rear bumper and secure it with the rearmost rubber grommet. Place the middle section of the exhaust system under the car and lift it up to approximately the right position. Apply some grease or anti seize compound to the end of the downpipe and slide the middle section about halfway onto the downpipe. Remember the exhaust clamp, but don't tighten yet. Fit one of the rubber grommets to the center section.
5. While one person is underneath the car checking the clearance between the downpipe, the propshaft and the chassis another person should tighten the nuts that holds the downpipe to the turbo. It is important that the clearance between the downpipe and the propshaft and the downpipe and the chassis is about the same. If they aren't it could easily lead to vibrations and lots of noise. I tried to make it a little closer to the propshaft to increase ground clearance a bit.
6. Put the exhaust clamp onto the rear section, apply anti-seize compound to the end of the middle section and slide it into the rear section about halfway (about 5 cm). Do not tighten the exhaust clamp.
7. Refit all the rubber grommets to the exhaust system. To make this a little easier use some spray-on grease or similar, and a long screwdriver.
8. Check the clearance between the left-side trailing arm and the back of the center section. Then the clearance between the rear diff assembly and the back of the center section. Adjust these two to make them about the same. Do this by sliding the middle section more or less onto the downpipe. I found it to be about right when the middle section was slid about halfway as far as it would go onto the downpipe.
9. Check that the middle section sits where it's supposed to and that all the rubber grommets are fitted. Tighten the exhaust clamp onto the joint between the middle section and the downpipe, about 1 cm from the joint. Make sure the bolts face up/sideways so the exhaust clamp don't get closer to the ground than it needs to.
10. Adjust the amount the tailpipe protrudes from the rear bumper by sliding it further in or out on the middle section. When it's right tighten the exhaust clamp in the same way as on the front joint.
11. You're done!

I found that the tailpipe sits a little too far to the left on my car but that's probably due to production tolerances.

Back to www.wrc-cosworth.org