Hey,

Im just about to pruchase a eb xr8, as soon as i get it i will be throwing a custom exhaust on it, how much ruffly would a set of pacemaker extractors (or genie), hi flow cats (good quality), and then a custom twin 2.5" mandrel bent setup dumping at diff cost?
also will the v8 run orrite with having this setup, and what will it sound like?

Thanks, Scott

Pacemakers should be around $500 supply only, cats around $200ea, and around $600-$1k for the exhaust depending on if you want stainless or mild and what mufflers you will run.

IMO twin 2.5" is way too big and will end up costing you overall power, it has been shown many times that a single 2.5" or twin 2.25" will give the best performance for stock to mild engines, its not really until you get over 260kw or so that you need larger.

i agree. stick with twin 2 1/4'' to single 2.5'' or just a single 2.5'' straight through. thats enough for stock to mild 5ltrs. do the eb-ed's all have twin 2 1/4'' from extractors?

I got the twin 2.5 is very rumbly, feels a lot freer than stock but haven't compared to any other setup so i'm not sure how much power loss i have over a 2 1/4 etc. Cost me 1800 with tips - PM extractors, 2 high flow cats, 2 mufflers, no rear resonator (is kinda loud, just the way a v8 should be) over the diff and out the normal rear opening. They did some fancy work with the bending to make it fit but no resonator gives a lot more room in the back to fit the pipes. Very happy, except my car is so low the diff hits the system sometimes ( ultralows in rear

would you be able to record the sound of your exuast note?

and would it being chopped at the diff too loud? just how loud

Curious!! Could someone explain the theory behind loss of performance through bigger pipes, I assume from thread and others similar that there is reduced back pressure, what is back pressure and how does it effect v8 engines in particular.

thanx

it has nothing to do with back pressure no matter what anyone tells you.

with a pipe that is too big you loose to much gas speed at low RPM wich will drop your torque a bit.

to build the gas speed a low RPM you need a smaller pipe, wich in turn creates back pressure higher up in the RPM. Back pressure is the enemy of horespower. building a good street exhaust for N/A is balancing act between gas speed and back pressure.

then how does the speed of exhaust gas, more or less affect torque. What components of the engine are relient on the gas flow to create torque.???

to be honest it's beyond a simple post on here to explain it all. it actualy takes 200 odd page book to cover it all.

but basicly if you have a pipe that is too big for a street engine the speed is low at low rpm and that gives poor scavenging on valve overlap, more so if the engine doesn't have extractors. as the stock manifold is very poor at scavenging. on valve over lap you are using the vacuum (and sonic pulse, but thats a whole other story) created by the by the previous exhaust gases to draw out the residual gas in the chamber and draw in fresh charge.
low gas speed results in a lesser or zero in some cases vacuum.


you need to match the pipe size and extractor type to the expected use of the engine.

there is a whole lot more to exhaust systems then just the usual answer of get some 'good' extractor and a good cat-back of 'blah' size .

but for the most part the duel 2 1/4 system will be fine for your average street 5.0L along with off the shelf extractors of what ever brand you want, as they are all a compromise between what fits, what is easy to make and the ballance between upper rpm power and lower rpm power that a street engine needs

Nicely covered tickford_6, back pressure myth put to rest.

Go to this forum if you want some more opinions Scott...
http://www.fordmods.com/forums/viewtopic.php?t=22664
I only just got a 2.25" twin system put on my Fairlane...it really is the best sound I've heard out of the 5.0L's IMO...I'll post a sound file as soon as my car gets back...

Hmm don't have a microphone but I'll see what I can do...

yeah 1 5/8 pacemakers with twin 2 1/4 to single 2 1/2 works real nice for stock to mild 5.0's adds heaps more torque down low