cars too low

SMOOTH 480 · Post by **SMOOTH 480** » Sun Jul 27, 2008 2:16 pm

cracked the joint once again in the week yesterday i took it off and put more joint paste and exhaust repair gum around the cat to down pipe flange !
all was well until today !!!!!!! came to a speed bump and started to crawl over when a tit in a vectra was obviously not taking note of my brake lights started skidding towards my rear end

foot off clutch and over the bump a bit smartish to avoid a crunch and i catch my exhaust once again resulting in a high pitched scrapping noise and loads of crunching from the under side

car now sounds like a massey furgoson special once again

i pulled over to inspect the car and the tosser in vectra drove past still arguin with his mrs

the result is me being out side for 2 hrs under the car in this nice weather trying to seal it up again
so whilst i was there i took all the neccesary measurments and started searching demon tweeks for slim line high flow boxes !!!

result !!!!!!!! mid box works out at Ã‚Â£50 and then i can make a twin flanged decat pipe
brackets i will make myself and then eld to the car to pull it up out the way. The only problem i can see is the part of the floor pan that has a small cut out o allow the exhaust to pass under may be too small for the box -- so a minor amount of reshaping may have to take place

lee · Post by **lee** » Sun Jul 27, 2008 3:09 pm

you so need to bring that car to the regular meet mids meet for me to have a look at as there is something seriously wrong as i have had mine lowered to 60mm with harsh konis on catch my exhaust everywhere yet it never once fell off or came disconnected in anyway shape or form

esta · Post by **esta** » Sun Jul 27, 2008 3:26 pm

Hey unlucky Smooth.

Its odd as my car isnt lowered and still scrapes against the bumps at the Kingsbury Island shopping place...which is daft really to have speed bumps there considering there is a Halfords and all slammed cars shop there!!

JohnTurbo · Post by **JohnTurbo** » Sun Jul 27, 2008 9:45 pm

Lee...remember the 'zaust on the 2.0 hangs low like your doggie's danglies.

SMOOTH 480 · Post by **SMOOTH 480** » Mon Jul 28, 2008 3:38 pm

yep there is a defo difference between the turbo and the 2.0 exhausts

it pains me to think the exhaust isnt 4 months old yet and the cat is quite badly scratched on the bottom side

lee · Post by **lee** » Mon Jul 28, 2008 8:14 pm

i know that the exhaust is slightly lower but my car was 20mm lower than yours with a larger bore exhaust than stanard and it was a crappy powerflow. Also dragon had his lowered 40mm on koni's with his monster 3inch bore which went under the rear axle. This again never came apart.

I feel there is a lot more involved in this exhaust matter than its lowered and the exhaust hangs lower.

There has been people come and go on here with lowered 2ltrs who haven't reported any such problems. Defo more to it in my opinion

aibast · Post by **aibast** » Tue Jul 29, 2008 5:58 am

I have no problems with my exhaust. Haven't scraped any speedbumps. Even if it sits lower than the cars other parts. As the sports cat and 2 resonators didn't have much of a space to go into. Its more or less 7cm off the ground.

pol · Post by **pol** » Tue Jul 29, 2008 9:15 am

There is a lot of room to manipulate / re-position the exhaust. I guess it depends how it has been fitted. It would help to have someone else fit / adjust the exhaust with you. It may help to use a jack to support the exhaust where it hangs low and then tighten up the mounts to the cat...

pol

Yossarian · Post by **Yossarian** » Tue Jul 29, 2008 9:16 am

I've got a 2.0 with standard wheels and exhaust and at college I used to occasionally bottom out on the speed bumps in the carpark.

That said, the bumps were fairly large, and it used to happen frequently if I went over at a funny angle.

aibast · Post by **aibast** » Tue Jul 29, 2008 9:52 am

I used a stand to press the entire exhaust to the cars bottom and then fabricate it step by stepp. After when I had everything connected and on the hangers, let the stand down and the exhaust got a nice 1 cm clearance. It does hit the body on rough cornering sometimes, but that is all. This is how low is my exhaust

You can see I have patched some places as my frind didn't weld so good and it leaked a little. Also on the top there is a small hint of the back resonator. The other 2 resonators and a cat are in line in the center of the car.

SMOOTH 480 · Post by **SMOOTH 480** » Sat Aug 02, 2008 10:57 am

to be fair the exhaust doesnt fit too well!! Its been pulled up as tight as it will allow me with the brackets and smaller rubbers but it still catches

and vibrates every now and then on the body pan if hard cornering ...
its the flange joint on the cat to down pipe that keeps getting caught and it pulls it open slightly ( enough to make it sound like a tractor )
if i can get some heat safely in there then im going to re-bend the down pipe so its at a better angle chop the mid section out complete and replace with a slimmer box ( ill be keeping all the bits for the mot man )
All i hope is that the box ive found doesnt make it too noisey it shouldnt as the back box will be the same
would like to do away with mid boxes altogether but lack of back pressure would mean lack of torque and much more noise

@ lee id love to go 60mm lower but 45-50mm is low enough for now untill the boxes have been sorted then its time to look at the 55mm options

aibast · Post by **aibast** » Tue Aug 05, 2008 8:53 am

there is no such thing as back pressure. Its a myth. You need a exhaust gas pulse velosity to remain for the torgue. But for a turbo car. It doesn't matter much. As the turbo kills the pulsed flow anyway. Mine is 2,5" thats 60 mm straight trough, from the turbo to the back, the exit from the last resonator is 2". With sports cat and so on. Here is how noisi it is

All you need is resonators to muffle the high pitch sound.
http://www.youtube.com/watch?v=jub0d2qdXDc
http://www.youtube.com/watch?v=Z24SXELhuLA

thats with some leaks in the system

SMOOTH 480 · Post by **SMOOTH 480** » Tue Aug 05, 2008 3:57 pm

mines not a turbo !
back pressure and the exhaust gas pulsation should work together to create dynamic scavanging where the exhaust works to pull the exhausted gas out of the engine in harmony with the valve over lap to channel it as quick as possible to the out-let ...
on a turbo car this isn't really as important as the turbo spooling will pull most the burned fuel gas out of the engine whilst the valve over-lap will have air-fuel gases being pushed into the cylinder under pressure pushing the gases out the exit !! If i had a turbo on the car then there would be a 3" straight through pipe to a nice 4" box at the rear with a 3" tip
but ... as its a non turbo and the pressure is needed to keep the car running smooth i will have to add a box half way down and pull it as close to the under-side of the car as possible -- removing the cat will also aid in clearance as on measuring the cat to ground clearance i have just over 3 "

Ive already made a few brackets that need welding into place and i have some spare rubbers knocking about in the garage

aibast · Post by **aibast** » Wed Aug 06, 2008 5:59 am

then go with a nice equal length manifold 4 to 1 to 2,5" and in the end go small. Like 1,5". I had this setup on my mazda 626 GC form 1984. And it had a lot of low end torque and managed to rev it freely to 8000 rpm. That was on a 2.0L 8v single 2 barrel carb engine. Was slower than the 480 turbo, but still fast for that type of a car. Also make a ITB in the intake side. + the usual port job. But I think you know this stuff anyway

But a straigth trough design resonator in place of a cat. It just keeps the ricer sound out of the exhaust. Also there is a small trick with a free flowing exhaust thats nice and quiet. Its hard to fabrikate, but it can be done. They used to do this stuff on truck here in estonia in the solviet times to get the sound levels to normal.

You take a staigth proper size tube and weld it there a 0.3 mm steel plate thats been slightly corkscrewed. The gasses flow around it freely , but the sound is muffled. My dad wanted to make this on my car, but he passed away