WARNING: Track Guys, Check Your Exhaust Systems

[Green Hornet]

Originally Posted by Chili Red

Took my diffuser off the other day and my exhaust clamp was loose enough that I could move it with my hand. Bolts were about finger tight..

+1

My muffler moved down the cat pipe until the diffuser stopped it.

When rubbing the diffuser it is occasionally very obnoxious sounding at low engine speeds, then is unnoticeable as revs climb.

The OEM exhaust clamp and muffler mounting do not seem up to the job.

[jkolb]

After I did a mild port of the stock exhaust manifold I had the inside coated with the same ceramic that they coat piston tops with, and the outside with a silver colored ceramic ($150). I have a 2bular decat and GT3 style muffler with a Von Hep panel eliminator. The 180 bend on the decat is ceramic coated. My system stays relatively cool, but I have also adopted the policy that race cars (and Loti are race cars) require constant attention when they are to be driven hard. I drop the diffuser and rear under panel before every time I am going to run hard, and check the torque of every bolt I can get to, make sure that my brake lines are running true, check brake pads, shake the muffler to see if anything is loose, etc. After replacing the diffuser and underpanel, I check all of my fluids and torque all of the wheels. All of this takes about an hour, thanks to the quick release fasteners, and it is actually kind of fun to commune with my car. Although my wife is still not happy with the exposed muffler and exhaust, I think that the rear panel delete at least makes the job appear to be easier and I pay more attention to details because it is all out there in front of me. The system stays very cool compared with the old stock system.

Jerry

[Casey]

I strongly urge all Lotus owners who frequently track their vehicles to remove the oven like heat shielding and the rear grill. I also recommend upgrading the engine mounts to limit the torsional rotation of the exhaust system.

[pixlpush]

I had the tips of my old style Larini SE exhaust tack welded in place because I couldn't keep them in place. The new ones are one piece. What about having the cat -> exhaust joint tack welded? Seems like it might solve the issue of the joint coming loose, what do you guys think?

[fishguy]

just throwing this out there as an idea.
what if naca ducts and some tubing were installed on the rear clam itself to provide some airflow to vent the rear end.
I have a home made brake duct venting system on the spec 944 i just bought, and the previos owner says it makes a huge difference. maybe something simple like this could be applied in this instant as well.

also just another reason to have a firesuit/gloves on while you are on track..........the unforseen can happen, and fire is a bitch that does not discriminate between burning your car or you.
Fishguy

[Jack]

Originally Posted by pixlpush

I had the tips of my old style Larini SE exhaust tack welded in place because I couldn't keep them in place. The new ones are one piece. What about having the cat -> exhaust joint tack welded? Seems like it might solve the issue of the joint coming loose, what do you guys think?

Two issues are at work, both can cause a fire. 1) Cracked cat weld which eventually fails and muffler separates from cat with clamp in place and 2) clamp failures at slip joint -- Lotus specifies that the muffler clamp is a one-time use item

Recent Lotus TSB on the subject:

BULLETIN..... Model: Elise/Exige/Europa/2-Eleven

TITLE: Precautions when re-fitting exhaust muffler on any Europa or Toyota powertrain Elise/Exige/2-Eleven.


REASON: To ensure adequate sealing and security. The slip joint between the catalytic converter outlet 'U' bend and the exhaust muffler is secured by a strap clamp and pinch bolt. This clamp is designed to apply the correct clamping force to the pipe when the pinch bolt is tightened to the specified torque of 54 Nm. In order to guarantee this result, the clamp is for one use only, as some stretching and settling of components will occur in service. Be aware that the security of this joint is essential to ensure the integrity of the exhaust system, in respect of emissions, noise, heat release and safety. Extreme temperature gradients and powertrain shunt (especially with track use), will subject the joint to additional stress, and for cars
used on closed circuits or in similar conditions, the Pre-Track Use Check List, LSL520 should be followed, which includes an operation to check the exhaust system for sealing and security.

ACTION: If an exhaust muffler is at any time removed or replaced, the following points should be observed:

1. Ensure that the clamp (A120S6000S or B116S6001H) is renewed, if necessary cutting the tack weld (used only to assist factory build) with a precision rotary tool to remove an old clamp from a muffler which is to be re-fitted.

2. Position the new clamp to be flush with the end of the muffler pipe, and orientated with the clamp split equidistant from the two patented joggled seal slots in the pipe. Tack welding the new clamp is not necessary.
Note that all new standard fitment mufflers, and Lotus accessory sports mufflers LOTAC05334, LOTAC05335 and LOTAC05450, are supplied with new clamps tack welded in position. Elise S sports exhaust LOTAC05391 will require a new clamp, A120S6000S, to be ordered separately.

3. Dependent on model, be aware that the optimum position of the muffler may not be determinable without trial fitment of the diffuser in order to centralise the tailpipe(s) in the diffuser aperture (note: access to the clamp is not available with the diffuser fitted). In this situation, the clamp bolt should be only nipped up for the position assessment, prior to torque tightening on final assembly. Achieve the maximum possible engagement of the 'U' bend pipe into the muffler inlet, consistent with acceptable tailpipe position. Assemble the joint dry.

4. Finally, torque tighten the clamp bolt to 54 Nm. From this point onwards, the clamp should be discarded if the clamp bolt is slackened.

5. Manually attempt to slide or rotate the joint. No movement should be possible.

[xxxotic]

Originally Posted by knucklehead

I just recently started to have this exact issue. Please post what you discover is the problem.

To Loki and Somyunguy, sorry to hear about you cars.

Me too.

When I put the car in reverse and let out the clutch when reversing up a slight incline and am not giving quite enough gas, it sometimes makes a loud grating vibrating sound that seems to be coming from the exhaust. Also, when I am driving at highway speeds I get a slight buzzing sound that seems to stop after I put in the clutch. At first I thought it might be that the performated plastic piece that has the rear reflectors (05 cars) was rubbing against the back of the clam, but I put a piece of foam in between to stop any rattles, but it still makes the buzzing noise. Howver the buzzing is much quieter less gritty sound than the reversing sound.

I only went on one autocross in the rain, and drove hard on a road that was in a closed off community where houses havent been built yet, and did about 10 laps around the road course at Homestead taking it fairly easy. I doubt this was enough to loosen anything up.

To check the exhaust do you just take off the rear undertray, or do you have to take off the whole rear section with the license plate holder, relectors, etc to get to it?

[LarryB]

Sounds like it maybe a combination of several factors. Engine flex putting a bit of strain into the exhaust system. Clamps that if not properly tighten or if reused not doing the job, coupled with a fair amount of heat build up…

[vyuen]

I too am considering deleting the heat shield and rear panel but I'm concerned about the parts near the exhaust cavity area. The reason the heat shield is there is to prevent other parts near it from melting. Are we solving one problem only to create potential new problems?

[def]

I have been meaning to check mine since last auto-x, have another one Saturday. Saw some soot in the first picture coming out of the defuser - NOT a good sign. You can see the small hole in the exhaust pipe in the 2nd picture. Need to rectify this before saturday's autox. It got too dark out tonight to try to loosen clamp, shift exhaust, and re-tighten. But with all of the clamp talk, maybe I should go get another one.

Sorry for the bluriness in the 2nd pict, lighting was bad so I tried to take a longer exposure, while under the car... after manually taking off the diffuser... and lifting weights earlier

[Darth G-F]

Originally Posted by Casey@ForcedFed

I also recommend upgrading the engine mounts to limit the torsional rotation of the exhaust system.

How big a job is this (upgrading engine mounts)?

[loki]

Originally Posted by pixlpush

I had the tips of my old style Larini SE exhaust tack welded in place because I couldn't keep them in place. The new ones are one piece. What about having the cat -> exhaust joint tack welded? Seems like it might solve the issue of the joint coming loose, what do you guys think?

There is a lot of movement in the engine when you throw the car around the track like a Lotus should. I think a tack weld would invite a break in some other part of the system. Working on some more flexible soloution. Will Report.

As per firesuitand most especially gloves, I generally wear them (my wife worked with burn veterans) and get looked at funny when it is 110 at Thunderhill but you only need it once...or not.

[DPM]

One of the main problems with the exhaust is that it does not move enough, if at all, with the engine. I posted a picture last month regarding this topic and I made temporary modifications to check my theory. Now my tailpipe moves with the engine, as it should. Eventually header bolts and / or the exhaust clamps start to work loose and you get pure exhaust leaks which apparently has lead to the fires recently posted or, as in my case, damaged shifter cables (they are plastic coated and melt) from turbo exhaust. My problem is completely gone since I dumped the muffler and catalytic converter. I plan on reinstalling them with a modification now that I know it works and that is to replace the CAT with a 3" flex pipe to handle the torque of the engine moving (I don't need it for track use). This should eliminate the problem entirely. Look at my O2 sensor cable that was melting from the exhaust before I made the change and that was without any rear panel.

Have someone rev the engine while you look at it from behind, the tail pipes hardly move. Take the car over a speed bump or a rumble strip and it's even worse as all the torque is transferrred to the fittings.

Just go back and pull up on the tailpipes with the engine off, they don't even budge! The stock system is way too ridged and poorly designed.

Another help would be a NACA duct with pipe directed into the exhaust compartment. The duct would probably be best from the top of the rear clam as most of the air around the wheel wells is probably dead air and wouldn't work too well.

[Mag]

Originally Posted by DPM

Another help would be a NACA duct with pipe directed into the exhaust compartment. The duct would probably be best from the top of the rear clam as most of the air around the wheel wells is probably dead air and wouldn't work too well.

good idea.

[DPM]

Another option I forgot to post was to loosen up the bolts that the muffler is hanging from. They used rods that go through rubber clamps and there is a lot of tension here too. This is probably the primary point of the bind from my analysis. Even with the ForcedFed engine damper installed, this engine still moves a lot. Without the damper installed the engine is really moving a lot more and that just magnifiies the entire problem with the exhaust even more.

[DPM]

If someone fabricated a 3" flexpipe that could be easily exchanged trackside for the CAT then that would be a fix to use only when needed. Hey Sector111 or ForcedFed, did you get that? Send me a proto for the idea!

[coulthard fan]

Originally Posted by Jack

Two issues are at work, both can cause a fire. 1) Cracked cat weld which eventually fails and muffler separates from cat with clamp in place and 2) clamp failures at slip joint ...

Just last weekend at the track I had failure #1 (described by Jack above) at the weld on the output side of the cat before the U-bend. It got noisy and exhaust gases were leaking from this crack that went almost all the way around the circumference of the pipe/flange, but luckily it never separated. My shop is going to try to reweld it. I suspect this is a temporary fix because this looks to me like a design flaw.

As a point of reference: this is a stock 2005 Elise; 23k miles; sees street, track, and autocross use.

[Lancia]

Do these systems use a flex joint(s)?
If not, they should.

And I'm told flanges are the reliable way to have parts that can separate.


There are some superb spring loaded clamps made in the UK.
That might help if you're using clamps.
Fasteners ~ Protex Fasteners Ltd

[plastique999]

Originally Posted by Casey@ForcedFed

I strongly urge all Lotus owners who frequently track their vehicles to remove the oven like heat shielding and the rear grill. I also recommend upgrading the engine mounts to limit the torsional rotation of the exhaust system.

I am naked....what engine mounts do you recommend...there are a few out there.

My Larini SE keeps tipping south...assuming it's loose, and need to check it.

[SweetDaddyD]

Need to check mine. I wouldn't be able to tell if it "got louder" I don't think. I have heard a rattle lately on start up, just figured it was the pipe hitting the edge of the cut out again as I've had that before and it was still close after grinding back a bit. Saw the same thing happen on a 211 at LOG this year.

I smell someone developing a new clamp soon.