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dumping exhaust at the diff

Started by makka , May 11 2006 04:52 PM

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#1 makka

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Posted 11 May 2006 - 04:52 PM

Gday all, I just dropped my exhaust at the diff and it sounds really good, its a pity that its only a tempory measure!
the only problem I have is that at low revs the floor of the car resonates, could this be fixed by putting some dump pipes on the end of my mufflers?
If that works I might leave the pipes dropped at the diff. If not I am going to have to make some new tailpipes that go under my diff.
Does anyone have some pics of pipes under the diff on a LH/X?

Cheers
Cohen

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#2 rodomo

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Posted 11 May 2006 - 04:58 PM

I don't think that would be legal, from memory I think only IRS can go under axle.

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#3 makka

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Posted 11 May 2006 - 05:04 PM

I thought it was leagal if the diff didnt come in contact with it? shortened shocks would fix this.
I just got sick of the clunking of the exaust and diff coming together every time I hit a bump so I ripped the tailpipes off till I can sort something out

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#4 rodomo

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Posted 11 May 2006 - 05:42 PM

I think you would find that to put them under the axle they would then be overall too low as per regs. Keep in mind that axle must be clear of exhaust at full travel of suspension.

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#5 _high_rpm_

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Posted 11 May 2006 - 06:01 PM

I don't think that would be legal, from memory I think only IRS can go under axle.

well the cars probebly gonna get defected anyone if they see the exhuast under diff as the rims are to big and probebly to low anyway

Edited by high_rpm, 11 May 2006 - 06:02 PM.

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#6 makka

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Posted 11 May 2006 - 06:06 PM

dont be too sure there luke, 15s are legal, and the height is close to legal.....

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#7 _high_rpm_

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Posted 11 May 2006 - 06:12 PM

thought you had 17's? or was that just a temperary thing

Edited by high_rpm, 11 May 2006 - 06:12 PM.

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#8 _Herne_

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Posted 11 May 2006 - 07:46 PM

My single 2 1/2" exhaust runs under my diff and I know it is legal as it had to be inspected by rego mechanics/engineers here in Canberra - we call it 'over the pits'. My car is lowered and normally runs 15" rims I also have a set of 14's I sometimes put on.
It had the 14's on for rego purposes. For what it's worth the lowest point of the car has to be 100mm from the hard deck (ground) thats what applies in Canberra but I cannot speak for other state rules and regs.

I will try and get a photo of it tomorrow for you Makka. Just depends if it turns out viewable or not

Cheers
Herne

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#9 _LJ355_

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Posted 11 May 2006 - 07:54 PM

I got twin 2.5 under my diff no prob and my car is lowered hers a pic

http://s54.photobuck...t=GTRXU1185.jpg
http://s54.photobuck...t=GTRXU1184.jpg

Edited by LJ355, 11 May 2006 - 08:03 PM.

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#10 rodomo

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Posted 11 May 2006 - 10:59 PM

Dusted off the old Vic Roads RWC books and had a look tonight. No mention of under axle being illegal but 100mm off roadway stands as mentioned above. With regard to suspension "must have adequate clearance between components and vehicle body" and with regard to exhaust "must be secure and have adequate clearance between all other parts of the vehicle and the road". I would suggest that means you would have to limit your suspension downward travel.
It also states regarding lowering that "the clearance between the suspension bump stops is not altered by more than 1/3 of that specified by the manufacturer.
Hope this info helps.

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#11 _high_rpm_

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Posted 12 May 2006 - 12:24 AM

here in sa it isnt just 10cm from the lowest point but every car has a differnt measure ment from the centre of the wheel to the wheel arch my mate got defected 2 weeks ago in his vl lowest point was 11cm but the centre of the wheel to the wheel arch was 220mm and had to be 245mm

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#12 makka

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Posted 12 May 2006 - 10:38 AM

cheers for the pics LJ355
Cheers for clearing that up Rob.
did you know that in Vic, the 100mm rule only applies within 1m either way from your axles, then they give a formula that is something like the ground clearence must be at least the distance between the axles x 33mm, that means that if your car has 2.01m between the axles, the midpoint between your axles only has to be 66mm!

Edited by makka, 12 May 2006 - 10:39 AM.

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#13 _Herne_

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Posted 12 May 2006 - 10:58 AM

here is my pic of the exhaust under the axle (best angle I could get) From this angle it might appear that the exhaust is very close to the drop tank but thats not the case and it never touches.

Posted Image

Cheers
Herne

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#14 _TORANR AMORE_

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Posted 12 May 2006 - 03:49 PM

Herne: When you jack up the car (so that the diff hangs) does it hit the exhaust?
This is the way I wanted mine done but the exhaust guy said that the diff would constantly bash into it when the car is bouncing around on the road.

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#15 _Herne_

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Posted 12 May 2006 - 04:51 PM

Herne: When you jack up the car (so that the diff hangs) does it hit the exhaust?
This is the way I wanted mine done but the exhaust guy said that the diff would constantly bash into it when the car is bouncing around on the road.

To be honest I have not jacked the rear of the car up since the exhaust was fitted that way. As you can see right now I have the front jacked up to enable me to work under it whilst the engine is out.

I do not take my car off the bitumen but having said that I have been known to drive quite hard and corner reasonably fast - faster than many!. The Diff does not touch the exhaust whilst on the road at all and never has. As for bouncing around the road?? My car sits flat and firm.

Next time I raise the rear of the car I will have a look to see how much clearance I do have.

The only reason mine is under the diff and not over is due to extremely limited clearance between the exhaust and the drop tank. There is enough room for it to fit but it's a nightmare for the exhaust fitter. My exhaust guy looks after me very well price wise so I have not insisted he runs it over the exhaust

Cheers
Herne

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#16 _devilsadvocate_

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Posted 12 May 2006 - 09:52 PM

Cheers for clearing that up Rob.
did you know that in Vic, the 100mm rule only applies within 1m either way from your axles, then they give a formula that is something like the ground clearence must be at least the distance between the axles x 33mm, that means that if your car has 2.01m between the axles, the midpoint between your axles only has to be 66mm!

Wouldnt the dist between the axles be the width of the diff? Or is it the dist bw the wheels?(2m is a very very wide car if it is) or is this the dist between front and rear axles, assuming they mean the line connecting the front wheels?

Re exhaust under axle, it would be wise to see if the axle clears the exhaust when weight taken off springs. This situation might not seem likely on the road, but if going over a rise at speed, full extension could be an advantage(to avoid that flying feeling). Or could even be an issue under hard braking.

Edited by devilsadvocate, 12 May 2006 - 10:06 PM.

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#17 _devilsadvocate_

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Posted 12 May 2006 - 10:10 PM

Must be the dist bw the wheels on the same axis, wheelbase of a torrie is over 2m.
Probably only applies to trucks, doesnt make any sense that a truck can be closer to the ground though.

Edited by devilsadvocate, 12 May 2006 - 10:11 PM.

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#18 rodomo

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Posted 12 May 2006 - 11:36 PM

The good book says,
"GROUND CLEARANCE
The ground clearance of a vehicle measured from a horizontal road surface to any point on the underside of the vehicle except the tyres, wheels and wheel hubs shall, with the vehicle in its loaded state as specified by the manufacturer, be not less than,
a)for any point in the WIDTH of the vehicle which is within one metre fore and aft of any 'Axle', 100mm.
b)for the mid-point between any two consecutive 'Axles' the dimension in millimeters obtained by multiplying the distance between those two 'Axles' in metres by 33.33"

Maybe I should start my own "Gospel" thread? The missus isn't too happy about having the dusty old book in the dining room though :blink:

Having said that, I am happy to "quote" but reluctant to comment.

Edited by rodomo, 12 May 2006 - 11:48 PM.

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#19 _devilsadvocate_

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Posted 13 May 2006 - 12:19 AM

Thanks for clarifying above, so for a torrie with 2.5m wheelbase, you can have some items within the 50cm of middle of the car 88mm off the ground.
Which is really the bit where you need the most clearance to clear speedhumps etc.

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#20 rodomo

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Posted 13 May 2006 - 12:35 AM

Doesn't make much logical sense does it :blink:

That's why I will "quote" but not comment.
My experience with Vic Roads is everything is just about a "grey area" which nearly means "we are non comittal".
Boils down to the individual testers "understanding" of the text.

Edited by rodomo, 13 May 2006 - 12:36 AM.

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#21 _Yella SLuR_

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Posted 13 May 2006 - 06:50 PM

Bags not following you on a dirt or gravel road Makka, damn things throw rocks and crap up at the vehicle behind you. I'm not a big fan of em.

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#22 makka

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Posted 14 May 2006 - 10:40 AM

Bags not driving down a dirt road!
I have found engine fans are worse at throwing stuff up.
the dumps have made a fair difference, they made it a bit quieter
Posted Image

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#23 _BMXer_

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Posted 16 May 2006 - 12:13 AM

i got twins running under the diff but it wasnt always the case.
i had it dumped like you did, but damn cop heard it as i drove past at an intersection, not saw i had no pipes. pulled me over and defected me for exhaust not protruding out the rear of the vehicle and not for noise cuz he said that was a worse offence or sumthing, go figure?

he then insisted in checking the engine number wih the rego as he was convinced that lx's didnt come with V8s in them and my car wasnt registered with one in it, the car came stock with 253 but now has 308 but he still insisted, scratching away the paint on the block with a key to read to numbers more clearly the blind idiot. he then said after all that, he wont fine me because he would rather see me spent the money on getting it fixed up.

he also breath tested me, which by the way i was coming home from work at about 10:30pm on a wednesday, i blew 0.00. he then wrote the defect for a full inspection, not to just inspect the exhaust but the whole car. i had illegal wheels, 14x7 and 14x8, you cant have different sized wheels someone told me and the mufflers would be the 100mm off the ground with the mags, but i had to use stockies for the pits.

so i put tail pipes on thinking it would be ok with a flange plate to keep it quiet just after the mufflers. it cleared the dB test which is amazing for twin 3 inch with race magnum mufflers haha.

dumb asses at RTA measued the flange at extractors... too low. checked the car over, was fine. went to exhaust bloke and said get rid of the flange. went back thinking it was fine... now he measured the mufflers and cleared 80mm, but he didnt tell me this the time before so i was fuming. i still had the old exhaust - 2 1/4 single over diff, told exhaust guy to take off the twins and chuck the old one back on. with 3 weeks stuffing around it was done but i was at least $250 out of pocket by the time i spent money on the inspections, and exhaust changes, not to mention a huge waste of my time. the exhaust is still loud, but not as loud and not resonating as before. twin 3inch pipes painted black out the back look sick... i know 3inch is too big but oh well, was a cheap exhaust for me to get.

i got lowered pedders shocks and springs and the shock travel is very small, so the diff doesnt hit the pipes at all, but its close.

now my rant is over, id make sure your pipes are not too low, keep the rear springs the same height, dont lower any more looks good and will keep exhaust higher off the road. having tail pipes makes it legal so its one less thing to attract cops... but in my case i dont think even having a stock car will stop cops pulling you over if you have a nice big red p plate on the car...

cheers and i hope my story helps in your decisions...