Backbox tinkerage - GOT VIDEO but can't put it up!

[Daveyboy20]

My backbox is fecked on the MK5 Tina, my mate can knock up aluminium pipe for me in any shape so im thinking of grinding the box off completely and just putting the pipe on for some tasty noise - thinkg is, will the heat adversely affect the pipe, and will the loss of backpressure be bad for the engine or will i just lose a bit of torque? Would there be anyway round it like maybe tacking something inside the pipe like some sort of washer? Ideas?

[Fiesta Steve]

Back pressure is a bad thing. Reducing it can gain you a lot of horsepower but will probably only cost you a very small amount very low down the rev range, not even enough to worry about.

 

I race mine with no system at all, straight out the manifold and run 13.8 with a x-flow so it certainly won't hurt especially if you tend to drive enthusiastically anyway, and by looking at your sig pic I assume you do

[orionmojo]

i would imagine the washer idea is bad, if it did create back pressur it would also create heat and it might do mor damag than good. i had a hooge backbox on my 1.4 cvh and it lost torque but still went on to do about 14000 miles before i sold it, when i put the original back on.

[Daveyboy20]

I always thought that you needed back pressure, so its actually better to have no boxes at all then? Cool, well jobs a goodun then im gonna make up a cardboard template tomorrow and get it sorted! I heard you lose torque though is that a myth? Oh and yeah i do tend to drive with a degree of 'enthusiasm' every now and then!

[Fiesta Steve]

Let me tell you a little storey

 

I had an 'off the shelf' manifold and system on my car, both were crap and I was convinced they were holding my engine back. The engine made 139 bhp on the rollers.

 

I had a custom manifold made up with huge 1" 3/4 primairies and a 2.5" system with one straight through back box. The chap that made it said i'd lose low down torque.

 

I took it back to the same rollers with no other changes and it made 153 bhp (+14 bhp )at peak and 17 bhp extra higher up the rev range after the power used to drop off with the old set up. It also gained about 5 lb/ft of torque at peak.

 

It did lose a very small amount of power and torque at around 2750 rpm and below.

 

But with the engine I have and the carbs and cam i'm using, the engine very rarely get down to those revs anyhow. So for me it was win win all the way.

 

As said, when racing, the revs are never that low so it can only help, and on the road, the loss is so small I wouldn't worry about it

[jlf70]

Very very interesting dude !

 

Think i'm gonna have to get the hacksaw out!

[Daveyboy20]

Sound! Right its coming off today then and my buddy is gonna have to get busy with his pipe bending skills!! Its a shame the pinto manifolds are so shite really as that'll be holdin it back a bit, looks like it was made with a hammer and chisel!

 

What sort of noise do you think it'd make? it'll be a totally standard exhaust except the backbox will be replaced by an aluminium pipe - do you reckon ill get any pops and bangs on the overrun? Its a 1.6 pinto with a 2 litre carb and k and n filter

[Copey]

Sound! Right its coming off today then and my buddy is gonna have to get busy with his pipe bending skills!! Its a shame the pinto manifolds are so shite really as that'll be holdin it back a bit, looks like it was made with a hammer and chisel!

 

What sort of noise do you think it'd make? it'll be a totally standard exhaust except the backbox will be replaced by an aluminium pipe - do you reckon ill get any pops and bangs on the overrun? Its a 1.6 pinto with a 2 litre carb and k and n filter

 

why dont you get a 4 branch manifold then??

 

not sure about the pops and bangs though

[mk3tina]

nothing at all different, my backbox got chopped off and the sound was just the same!

[orionmojo]

i'd say it will pop on overrun, mine did, sounded feckin great dropping to second at 45mph .

[Daveyboy20]

Well, just done it and it sounds feckin great! Havent got it warm or under an load yet as ive only started it on the axel stands but just revvin it it snarls when you let off the pedal, you know that rooooAAAARRR- GAAAhhhhhhhh noise you get! Im chuffed! He hasnt made me the fulllength of pipe yet im using the 10 inch smaple he gave me which doesnt quite come out under the valance but it'll sound the same. Great! oh yeah CopeyCapri, Ive got a 4 branch on my Capri but it cost nearly £100 and itt match up to he standard system as its a lot longer than the original manifold so if i was spending money on manifolds i may as well buy an ashley sytem and i can5 afford it at the mo!

 

Made up with this one though its gonna look and sound ifferent to most so im pleased My guess is that with a bit of heat and a bit of load say in second as you say it'll pop and crackle judgin by the noise

[Stu_B]

love the DIY approach! I have a wyleco racecan off a Buell on my daily driver - sounds great!!

[orionmojo]

nice one, get a vid

[Daveyboy20]

Just done a little vid on the digital camera and its picked it up well but i cant put it up. Its 40 MB, I tried to put it on photobucket but it never got past the 0% uploaded screen! Ill try again...

[orionmojo]

40mb!!!

 

try turning the quality down on the cam

[Daveyboy20]

Ah right it see! Is there anyway of compressing it at all? Ill just make another one later or tomorrow if not, a bit shorter perhaps!