Whos got them? Where did you get them? Pros and cons etc etc?

Time to replace mine and I'm starting the research

Cheers lads

J

 

pros.. Possibly a little more power, but I have never seen a back to back comparison.

cons.. You loose the famous rumble

 

I know the burble goes but I'm not that bothered. Thanks for the reply mate

 

I wouldn't say it totally goes:
Type R, Blitz Exhaust, OBX EL manifold, ticking over/light revving at standstill

 

ive been told you get more low down torque but less top end power! ive got the powerstation equal length headers.i wasnt that bothered about loosing the burble,and the gain of higher torque was a plus.the only problem ive had is the brackets snapping off(the ones that tie the tubes together).

 

Not that I'm an engine design expert, but knowing a little (very little!) about turbocharger and exhaust theory this sounds like another case of rules of thumb for normally aspirated tuning being wrongly applied to turbocharged tuning. On a Scoob, power fundamentally is a result of boost pressure, above all other things. Whatever is the quickest way of spinning up the compressor, and keeping it spinning across the broadest range of revs is the best. This means the biggest bore and shortest exhaust system you can practically get on it - or put up with. Before the turbo, this means a fat, high flowing up-pipe. The turbo itself is largely kept spinning efficiently by regular pulses of exhaust charge from the exhaust headers. The more irregular they are, the less efficiently the turbo works. The layout of a Scoob boxer with its standard unequal length headers gives the signature off-beat engine note, but also means the turbo is being driven inefficiently. Equal length headers ensure absolutely regular exhaust gas pulses along the up pipe with a corresponding increase in efficiency and thus power. There are no downsides to this that I can see apart from the loss of the unique sound.

With a normally aspirated engine, exhaust tuning (diameters, lengths, 4-1 or 4-2-1 layouts etc) is crucial for extracting optimum output whether this is biased towards top end power at the expense of a good spread of torque, or vice versa. On a turbocharged engine exhaust tuning is very simple - get the exhaust pulses regular, get them to the turbine fast, get them out along the downpipe fast. The way to do it is equal length high-flow headers and a wide exhaust system which creates as little back pressure as possible.

IMHO!

 

i have scoobyworld open neck downpipe, helix up pipe, straight thru centre with blitz nurspec s rear section, all with equal length headers and i have to say its the coolest soundin car ive ever owned/drive, doesnt completley lose the burble and sounds mental at revs!!!

 

Nick Read -

Cracking response mate, thank you - even I can understand that!

All -

Any recommendations?

J

 

probably lost about 400 rpm ( getting 1 bar by 3400 rpm on a vf35 with p18 exhaust housing) to 1 bar boost but gained on torque at the top end 320 bhp/ 320 lbs
sadly havn't got back to back results

I have also got powerstation headers but have had bo problems

 

That's not a characteristic of EL headers - just of tubulars in general. You never hear rally cars without ELs but i don't think the gains are worth that much unless you're passing the 400bhp mark IMHO

 

Sorry tath, find this a bit confusing. What point are you making here?

Cheers

J

 

tubular headers move the spool up the range slightly. I doubt the equal length is responsible for the shift of 400rpm, if anything the smoother gasflow should spool a turbo earlier?

 

what tath is saying (regardless of wether equal or unequal) is that tubular headers on a relatively small turbo wont do a lot for you. prior to a map i put UEL ones on (mated to o.e P1 VF28) and they definetly made it spool a few hundred RPM later than with the cast headers

if you are at this spec(ish) you are better off porting the standard cast ones.

only at higher horsepower will the benefits of tubulars make themselves known, when (i presume) the innacurracies and bends of the cast ones will become a restriction.

not actually sure anyone has done conclusive back to back testing of EL and UEL tubulars TBH. would be interesting to see, i suspect the results wont be massive %age wise.

 

oops sorry tath!

 

it's ok i was making both these points but i thought that the first one was the one causing confusion

Recap -

tubular headers move the spool up slightly higher.
tubular headers give better top end results, especially on highly tuned engines.
this might be pointless/damaging to driveability on a 280bhp car.
EL headers are marginally better, again moreso at big power, but won't cost any spool up.

 

Guys

The reason why tubular (be it unequal or equal length) spool later is due to their diameter usually being wider than OE, hence gas speed is slower pre turbo. Before the turbo is boosting (i.e. as it spools) the engine is NA - all be it with a restrictive turbo in the way.

The OE headers cannot make as much power than the usual aftermarket types due to the smaller diameter pipes becoming restrictive at a certain point. But because the OE headers have smaller diameter and short length pipework, they will spool the turbo quicker.

So basically tubular headers will give you more power but the torque curve will be delivered later in the rev range.

 

Perfectly put.

 

Surely the narrowest point where gas speed will be at its highest is at the entry of the volute inside the turbo. All turbos have a tapering exhaust inlet so what does it matter how big in diameter is the up-pipe as long as its at least as big as the entry to the tapering turbo inlet?

Or are you advocating that the up-pipe should be narrower than the entry at the inlet flange?

 

Brackets unbolted themselves on mine, but otherwise exacly same experience. Had a remap down and mapper commented on how much advance car was now able to run

 

Thanks for all the responses fellas. Is it agreed then that more low-end torque is acheivable with EL headers, this is what I would like to achieve even if it is at the sacrifice of BHP.

 

I'd imagine the highest gas speed would be just after the first turn in each header, just after it's come out of the exhaust port. More heat = more energy = more velocity. By the time the gas is at the turbine it's lost heat and velocity already (hence one of the reasons to heat-wrap your headers and up-pipe). I'd have thought OE headers, although narrow and conducive to good velocity if done right, are pretty rough cast inside? Therefore even a set of tubular headers with identical dimensions as OE would be an appreciable improvement.

So you want tubular headers rather than cast for the internal smoothness - not necessarily the diameter of the runners. That should presumably be the same as OE or perhaps slightly larger but not too much.

 

The gains on equal outplay the gains on unequal, ie you dont gain anything on unequal except the burble.
Equal will give you better torque and power, hence you see the new age JDM STi's pushing more BHP AND torque over the classic but without the burble.

Tony

 

Nothing to do with the twin scroll?

 

Nope the avacs and turbo give the low down grunt, the equal length will improve on that, better more even flow and smoother, if they ever get engineering to the point where everything is totally smooth/perfect, everyone would be happy but equal length is the way to go

Tony

 

Surely it is not just the pipe diameter that gives the higher spool-up speed, it is the layout. OE runner from each bank join up in a short distance. Tubular usually have longer runners before they join, so even with the same diameter they have a lot more volume. It is larger volume that increases spool-up revs as it takes longer to get up to pressure when you open the throttle.