Exhaust protection

Lambo911 · Post by **Lambo911** » Tue May 05, 2015 2:00 pm

Hi,

I think the ride height on my S3 is about normal and the exhaust is mounted up close to the floor but it still grounds out quite easily.

Then on Sunday, thought I'd take the car out in the sunshine and I caught the exhaust on the metal channel the garage door runs in and I've broken the manifold or downpipe, not sure which bit yet.

Has anyone fitted something like a skid plate to try and protect the leading edges of the exhaust?

Post by **mgcjag** » Tue May 05, 2015 3:21 pm

Hi Richard..this may be of interest see the last couple of pages a S3 owner trying to increase ride height viewtopic.php?t=6841&postdays=0&postorder=asc&start=50 sorry cant help with the skid plate idea.but have a look at the exhaust clamps and make sure the thread ends are not pointing down..Steve

malcolm · Post by **malcolm** » Tue May 05, 2015 3:54 pm

Worth checking you've got the right exhaust hangers fitted - shouldn't really bottom out that easily.

D COUPE · Post by **D COUPE** » Tue May 05, 2015 5:05 pm

I have just had this issue it was catching every where. Even when I attended a surprise birthday on a glorious sunny afternoon......... I saw the electric gate STOP in the middle of the drive but before I could take evasive action it pulled the exhaust clean out of the down pipes. Embarrassed is not the word. So after that I thought I need to cure it once and for all.

I split the exhaust in to its components and fitted it back piece by piece.
My first observation was that where the front box attached to the down pipe it actually pointed downwards which in effect made all the exhaust hang low. I undid the three bolt flange and raised the short pipe section so it was ever so slightly inclined and tightened it. When I fitted the first box it then tucked up closer to the heat shield. I then turned my attention to the 'Hook Clamp' that goes round both centre boxes. I bent the hooks down wards which actually then stretched the rubber donuts. This then held the rear of the center boxes higher and more into the heat shield area.

Two things to look for here is that the center boxes are twisted ever so
slightly upwards and just for a bit of extra support if you have the hooks aligned correctly you can twist the donuts to keep it nice and tight and out of the way. Has soon as I replaced the rear pipes I could see the whole exhaust was out of the way and now it clears 90% of humps and gate STOPs. Hope this helps

DC

Lambo911 · Post by **Lambo911** » Wed May 06, 2015 8:59 am

Thanks everyone. I'll go through the system again. when I fitted it last time I did attempt to minimise 'lowness' but I'll have another go. The car does sit slightly low on the drivers side front corner (especially with me in it!) so I'll also sort this out.

Cheers

paustin · Post by **paustin** » Wed May 06, 2015 10:50 am

Hi Richard, I fitted AJ6 Enginering Extractor Exhaust System - it dispenses with centre boxes. Result, improved ground clearance slightly improved performance and acceptable noise levels.

Regards,
Phil Austin

Lambo911 · Post by **Lambo911** » Wed May 06, 2015 11:07 am

Ooo sounds nice, how much are they ?

Is it just the exhaust or the manifolds too ?

PeterCrespin · Post by **PeterCrespin** » Wed May 06, 2015 12:05 pm

Google AJ6 Engineering. Replaces Y pipes with two long extractor pipes each side that merge further back. Available in two flavours - twin pipe at the back with significant silencers (the system referred to here) or a cheeky quad-tip version with nominal resonators that liberates ponies and decibels in greater measure. I had a twin system. Very well made.

Woolfi · Post by **Woolfi** » Thu May 21, 2015 10:45 am

If the back pressure of a exhaust system is lower, the mixture is becomming leaner. This will first slaughter some ponies and later kill some pistons.

A cheap and quick trick for a morte "sporty" sound is to "make" the front silencers with a big hammer and a "sharp" iron a freeflow-through box. The sound will remain very similar, but it will be a little bit lauder and more "sharp".
Regards Wolfgang Gatza

PeterCrespin · Post by **PeterCrespin** » Thu May 21, 2015 2:25 pm

Woolfi wrote:If the back pressure of a exhaust system is lower, the mixture is becomming leaner. This will first slaughter some ponies and later kill some pistons.

Not really, at least not during normal driving with constant vacuum carbs. Remember the exact same jetting was used on 3.4/3.8 and 4.2 triple SUs. The S3 Stranglebergs operate on the same principle and a change in mixture demand doesn't really mean a change in mixture strength as it might with other inductions.

Yes, for full race exhausts, or extreme driving that breaks every country's limit except Germany's, it would be safer to set the carburation up for prolonged use at target revs. But for day-to-day driving the AJ6 system is fine.

Woolfi · Post by **Woolfi** » Thu May 21, 2015 4:28 pm

"Not really, at least not during normal driving with constant vacuum carbs."

Hmmmm . . . Bywater is writing the same on his homepage, when offering his exhaust systems. But:
1. I have "opened" the front silencers of my EV12 5,3 to a straight through 48 mm. After this my car had flat spots when accelerating strong, BECAUSE of too lean mixture. I have a innovate LC1 Lambda-gauge in my car, and could see this very clearly.
After I have reshaped the 4 needles, the flat spots disappeared.
2. A friend has done the some with his silencers. He also had to "reshape" his needles.
3. On another EV12 a garage has mounted 2 glaspacks instead of the 2 front silencers. Since this change the car is running bad. I think because of lean mixture.
4. Grandmaster of (SU-) tuning David Vizard wrote about this: " Changing the silencers often affects the calibration of another components such as carbs and ignition timing." . . . Change the back pressure and you change the world the carbs sees . . . removing the silencer will generally cause the mixture to ge lean." Page 265, in "Tuning the A-Series Engine", 3rd edition , 1999.
5 After I have changed to a 6,0 l motor from a 1993 limousine, I again had to reshape the needles of the 4 Strombergs, that the mixture would be correct. AFR 14 at idle. AFR 15,5 - 16 at part throttle, 13,5 at full throttle. Plugs bright gray, gas consumption roundabout 19 mpg, motor runs perfect. With the original needle the motor would not run.
All this was my experience in reality, not in theory, not in my believes.

Also I don't believe, that the mixture at the 3,8 and 4,2 motors would be the same, when having the same needles.

If the back pressure of Bywaters exhaust systems is similar to the original system, there would be nearly no need for another needle shape. I believe that the back pressure of the AJ6 system is lower and the driver does not feel the small lack of power, because of leaner mixture. The lambda-gauge would open his eyes.

If there would be no need for a different needle, after having changed the back pressure od the exhaus system, why are existing X00 of different neeldes for a SU-carb ?

Regards Wolfgang Gatza

PeterCrespin · Post by **PeterCrespin** » Thu May 21, 2015 7:04 pm

Clearly messing with the exhaust can affect mixture and as you say any change (including the inlet side) that enhances air flow tends to lean out the air fuel ratio. I'm not disputing that.

And I would certainly expect a greater change from messing with baffled silencers than absorption types. Same for messing with front silencers closer to the engine than straight-through resonators further back - especially simply smashing holes in the baffles and destroying the tuned resonances and chamber integrity. So Vizard and you and I all agree.

At wide open throttle, when the engine is pumping its ultimate airflow, there is no more adjusting or feathering and you have to set the main jetting right to get the right fuel/air mixture. At WOT the needle has negligible effect, it's the jet orifice that controls fuel flow. In many cars yes, to get the best clean-running performance on modern fuels and with non-standard parts you should ideally set the car up on a rolling road and may well need a different needle. There are different needles made because there are many different cars and settings. They did not use one needle on one E-type and a different needle on the next one down the line, or the one after that.

Same with 3.8 and 4.2 E-type SU jetting - the carbs are the same. In fact I think only the piston damper and maybe return spring changed on the MkX/420G, but could be wrong. Someone will have the huge application chart. Your gauge is a perfect tool to get it right. I wish I had one.

My comments were specifically about normal driving with that AJ6 system. I've done a lot of exhaust modification in my time and I had one of those AJ6 systems myself once. The longer intermediates create a column of gas that extracts more exhaust in mid range. They are not perfect for every speed and I have no idea about the other cars you mention - it sounds likely you are right in your diagnosis but cause and effect may not be proven.

MfG

Pete

Woolfi · Post by **Woolfi** » Fri May 22, 2015 10:27 am

Hello Pete !
Thanks for your explanations.
I was thinking about, to buy two TT-piepes from Bywater, because of the extraction effect. But I do not trust Bywaters words so much. He has a big amount of knowledge, but he also wants to sell his parts.
Have you felt a difference, after you have mounted the TT-system from AJ6 ? Are you shure about this difference ? Is the extraction effect reality or only a marketing fairy-tale ?
The best toolf I have ever bought for my EV12 was the innovate LC1 for roundabout 200 Euros. I can see clear how the mixture is at any moment of driving. I have only two measuring positions in my car. Therefore I will measure left or reight bank. Still there is a chance, that there is a difference between the cylinders 1, 2, 3 and 4, 5, 6, becaus e of different carbs.
If you are sometimes tuning you cars, a LC1 would be very interessting to watch. The carbs have no secrets against you anymore.
Regards Wolfgang Gatza

PeterCrespin · Post by **PeterCrespin** » Fri May 22, 2015 11:46 am

I worked for a couple of years in the village where Roger lives and have been to his house a few times. I have rarely met a vendor who is less pushy or prone to BS, as you can tell if you read his books on engine technology. He is an evidence-based sort of guy but if you're asking me have I seen his dyno charts no I haven't.

If his products looked a bit wacky or his claims sounded bogus: "these new square exhaust pipes add 30 bhp!" then we'd all be suspicious. However, since his extractor exhaust fits perfectly with the theory of exhaust design I see no reason to doubt his claims. There is even a higher-performance noisy version where you can see the different pipework and figure out why it works better still, but would be loud on the road. 'If it looks right it usually is right' applies here I think. He does not make the exhausts himself, he uses a specialist in a nearby town and we used an X300 car of mine to make a prototype mid-catalyst replacement section, which improved computer mpg and performance by a few percent and the car still passed emissions due to Lambda control.

Instead of buying two, why not just get one and see if you like it? There is no silver bullet power enhancer but you obviously have the ability to dial everything in and get the maximum out of your exhaust (excuse pun).

MfG
Pete

Lambo911 · Post by **Lambo911** » Mon May 25, 2015 9:32 pm

Well, I've managed to get access to the manifold to check out why it is blowing, the right hand front manifold has snapped completely and the rear is cracked so they both need replacing.

I'm guessing the stock manifolds are fairly efficient as most of the sports exhausts advertised connect up the standard downpipes? The only ones I have seen are tubular ones which then require a slightly different exhaust system.

I don't want to replace the exhaust yet as it's in good condition so I think I'll just get a couple of replacement manifolds from DMG at ?175 a piece unless any one has a better suggestion ? Or a couple of good second hand ones lying around?

Cheers

Sjmmarsh · Post by **Sjmmarsh** » Mon May 25, 2015 11:51 pm

Richard

I suspect one of my manifolds is blowing as well - how did you get access to check? Put it on a 4 post lift?

Steve

Lambo911 · Post by **Lambo911** » Tue May 26, 2015 8:43 am

Steve, you can get a partial view from underneath but the only way to properly inspect them is to take the carbs off and the heat shield, it's not difficult but you do have to drain the coolant and take the thermostat housing off. So you'll need some gaskets before you put it back together. The instructions in the workshop manual are easy to follow.

There are a couple of manifold bolts that are going to be tricky to get a ring spanner on to loosen, the manifold is scrap though so I should be able to grind them back to get some access.

Sjmmarsh · Post by **Sjmmarsh** » Fri Sep 18, 2015 5:59 am

I had to resort to using a garage to getting mine off as some of the bolts were seized and in the end needed stud extractors to get them out. At least it want an engine out job, although it looked that way for a while.

It turned out that all 4 manifolds were cracked to some degree and the silencers had started to blow so were replaced as well. It turned out that one of the silencers had been fitted back to front, which also explains why the exhaust never quite looked right...

The car is so quiet now!

Steve

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