guys just a quick question , i know it needs to go on the rollers but.. what do u think my bhp will be ?
i have a supersprint cat back zaust, a k&n panel filter with a modded air box, and a gtec1... any ideas?

240-250bhp.

Ross

somewhere around 240-245 bhp me guess

LUM

i rekon fmi next..

260 on a healthey engine me thinks.mine did 245 with just exhaust and filter

228.4bhp

I stimate bout 234.9 rake orse ower

934.7

it's only the G-tec thats actually doing anything

the panel filter is just a filter that you can clean

the cat back won't do a thing because you still have the restrictive downpipe and cat

and..... modified air box? modified for what?

do you mean drilled? if yes... that does noting but make noise

Spot on dude. Thats why i think all the other mods will just confirm the power of the gtech.

Ross

see



i'm not just a pretty face

(i'm not even that)

ha

The cat-back will still be good for 5-10BHP.


coupecraig = FAIL

Pinin - dont think so dude. The downpipe and cat are the biggest restrictions.

Ross

Undoubtedly, but a sports cat-back is going to be less restrictive than the normal from the cat-back, you still have the mid and back-box.

Shut up ya pair of bawbags.

think of it this way...

get a straw, pinch it at both ends (so air can get through) and blow down it

it's hard to blow ye?

now let go of the end that is furthest from your mouth, is it any easier? no, because you're still getting restricted by the part you are pinching by your mouth, this is like fitting your cat back system

Oooooft.... hate to admit it, but it makes sense!!!

Ross

I get the idea - I mean I know what I have to do - but I can't find a straw.

When i was typing that, i was wondering how many people would get a straw after reading it

haha

lmao only asked..

o by the way, k7n panel filter is less restricitve than a standard filter, drilled air box does improve airflow, more air flow better throttle responce ect, used to drill air boxes on rd350s gave a bigger power band.

Are you gonna go and get it tested?

Ross

yep
i rekon surrey rolling road is the nearest to me? whats it cost?

my rolling road cost 55 inc vat

thats not to sad

So you really think a cat-back gives absolutely no power gain I guess we need to test this on the rollers. I still say it's worth 5-10BHP easy on a turbocharged car that has 220BHP standard.

i agree to be honest as some boxes will be less restrictive than standard

oh and my first coupe just had a modded airbox with cold air feed and gave 243bhp on the rollers

In relative terms, no.

Yes its less restrictive, but bhp is top end power. Is it less restrictive top end? Doubt it. The downpipe and cat are strangling it. It might give more midrange torque.

Ross

i think this could go on all day to be honest, some will say yes others will say no.
i think until we have figures then all will be speculation.

having looked at the hall of fame i think all coupes will react differently to a cat back depending on the engine health.
loads of different mods giving loads of different figures and impossible to gauge what you'll get????

Yeah its all on the assumption of a healthy engine. If you take an average of cars with gtech and exhaust its 250bhp.

Ross

exactly, like i said my first coupe only had a modded airbox and gave 242bhp!! no other mods.

All that really means, is that when you add more mods, it doesnt give as much an increase. I.e adding the gtech wouldnt give you 30bhp more. It would give slightly more than stated 250 but not 30bhp ontop of the 242.

Ross

260 hp.

The end

228.4

Maybe on a significantly tuned coupe, however the standard downpipe is not going to be strangling that much an otherwise standard coupe I don't reckon.

Yeah but we are talking about 2 restrictive parts, that were designed for 220bhp, low amount of noise and to pass emissions tests.

Ross

I totally agree with that statement Ross! ho hum this could go on forever, let's leave it there

try the straw thing

well will let you all know at end of month , winner gets a 4 pack

deffo 228.4

The straw thing is an interesting analogy. TBH, it depends upon how big the restrictions are and what the flow of gas is (according so some chap called Bernoulli ) There will be pressure drop all the way down the exhaust until, pretty much at the end of the exhaust (just past it) it will be at atmosphere. Each bit of pipe (downpipe or cat say) only "sees" the pressure upstream and downstream of it. Any restrictions downstream will limit the pressure drop possible across the component: Flow = function of Pressure Drop.

What I'm trying to say (in a very long-winded way) is that the back cat bit will have some impact almost certainly but its effect will be governed by how much of a restriction it is relative to the others. Electronically minded of you can draw parallels with resistors. Voltage is the pressure drop, current is the flow of gas.

Hope that helps

Richard
Fellow of the Institution of Mechanical Engineers

237

I think I find you more interesting on the washing machine thread

Damn - I thought that might be the case PMSL