hrubago

Can anyone agree? Better horsepowers bud smoother exhaust sound. Which your experience?

ChristianR

iTrader: (1)

i have a hks manifold, sounds great. Much quieter inside, and yes you do loose the sound... but it is still their, just not as loud

hrubago

Some HKS manifolds are (friend told me) for Subaru original manifold sound. But PE not...........

uxg

Don't quote me on this as this is just something I heard so am not 100% sure but doesn't this have something to do with the fact that the pipes on the orignal Subaru manifold aren't even length whereas most aftermarket manifolds are. This helps increase the hp on aftermarket ones but does somewhat reduce the flat four warble.

nom

Something like that. But, as usual, rather more complicated...
The HKS does stay similar to the original, just with most of the drone gone, making the cabin a nicer place to be on long journeys!

harvey

iTrader: (48)

Have recently fitted Ion Spec 4-1 tubular headers from Canada.They are coated inside and out to improve thermal dynamics.
Burble has mostly gone.More like my GSX 1100 R but the performance gain over my previously ported cast headers is beyond belief and the rolling road figures back that up too.
When I went home for the first few nights after fitting the headers my dog did not recognise the car because of the different sound.

hypoluxa

The standard cast Subaru manifold is what causes the Impreza off-beat sound. With the turbo being offset to one side of the engine bay (left), exhaust gases from the opposing side (cylinders 2+4) have to travel further before they are all united together in the up-pipe.

An equal length header will space out the exhaust pulses so that they arrive at the turbo evenly spaced. This helps the turbo spool up better and work more efficiently.

The HKS headers are a good option if you want to retain some of the scoob sound as they are not equal length.

iirc mapping a car with the HKS headers we had to add about 6% more fuel top end ( but had to take out a similar amount low down). Sound lovely.

Harvey,

I have some custom 4-2-1 equal length headers going on my car next week, I would be very interested to see how they compare with yours.

harvey

iTrader: (48)

Happy to share the info. I was going for 4-2-1 and had them on order when Ion persuaded me that for my spec 4-1 was what I needed. Fortunately I took the advice based on my spec.
Bell me sometime 07860 302020.

Hoppy

Harvey is right - the unique sound of a Scoob is all to do with the unequal length header pipes and nothing to do with the flat-four cylinder configeration. So much I know. The next bit is what I believe to be true, but I'd like someone with real knowledge to comment, please?

The stock unequal length headers give better bottom end power, and lose a bit up top. The longer pipes are better low-down and the shorter ones up top, so a good compromise.

Equal length headers are not only the same length, but shorter. I have ScoobySport's system on my UK00 car and while not exactly equal length, they're quite close. They transform the car in a few ways.

The car now sounds nothing like a Scoob but very like a noisey bike or a Caterham. It is much quieter (no other exhaust components changed) but I think this is an illusion. The car has lost it's bellow and gained a bark, with the new headers moving the resonance up the scale a bit, which sounds quieter but probably isn't. The car no longer shakes the house windows!

When you get the old pipes off, you'll be astonished at how heavy they are! I didn't actually weigh the ScoobySport system, but I would guess at least 8kg lighter. If you want to put the undertray back on it needs a bit cutting away to clear the new pipes. Not a problem. Best lag them as they work better when hot, and there's some wiring down there that needs protecting.

Oh, and by the way, the car now goes like the clappers I've not lost much low down that I can feel, but the way the car now rockets to the red (even more so now that John Banks has done a Tek3 for me) is amazing and addictive. A wild guess, but I reckon maybe 20bhp extra at around 6,500rpm? It just wants to rev and feels smoother, too (probably it's the different sound playing tricks).

Conclusion. Don't like the sound, but love the performance with hybrid TD04L from Mark R19KET and big TMIC from the Spin Doctor's collection of go-faster cast-offs. Fantastic combination and bargain prices. 310bhp JB reckons.

Hope this is of interest/helps.

Richard.

JIM THEO

PE 4>2>1 true equal length headers before six months, I lost completely the boxer sound and some of the torque below 2900-3000rpm but huge difference in the middle-high range. Currently my car is TEK3 from John, VF29, Magnex downpipe, PPP centre section and muffler.
Same performance with a friend with TEK3, VF23, APS induction kit, 5Zigen exhaust which shows how much difference the new headers did.
JIM

harvey

iTrader: (48)

Actual measurable power gain was 16BHP on top of an already well ported stock cast header. This included up-pipe. Weight saving was3.9kgs after lagging. Was not 100%confident it would be a good move overall because of what others that had tried different tubular headers had told me. Very happy with my result and conclude that there are good and not so good tubular headers on sale in the after market.
My response and spool shifted up by the smallest margin measurable but an in gear acceleration time I use as a bench mark and on which I control the perameters stricktly came down from 13.79secs to 12.21secs on a six run average each time. 13.79 was already a fast time. This figure started off around 16.5secs last November when the car was standard and all mods are tested to measure the improvement.(or otherwise on odd occassions)
On top of the power gain is the ease and speed at which revs now increase beyond about 3300-3500rpm.


[Edited by harvey - 10/20/2002 3:49:14 AM]

john banks

I have now mapped five cars with three different manifolds:

1. TD04L with HKS manifold
2. 2 X TD04L hybrid with SS manifold
3. VF28 hybrid with SS manifold
4. VF29 with PE manifold

1 & 2 were the best despite what people say about the TD04L with a manifold. They seemed to genuinely lose very little in spool up but had considerably more top end.

3 was my car and with the VF was frankly a slug so it came off. I was getting 1 bar at 3200 RPM but it was flat below there. With original ported manifold I now have 1 bar at 2900 RPM in similar temperatures, and now at 2800 RPM now it is a bit colder. Maybe Harvey's higher compression ratio and different manifold make his bottom end response good whereas mine was crap.

4 was good IMHO and behaved like a VF23 with the original manifold - would have been cheaper to just get a VF23? Also there was some low down torque missing, and this is what the owner wanted.

Sometimes there is a problem holding much top end boost with a manifold too. Sometimes an actuator or restrictor change is required.

I gather Bob has done at least twice as many cars with manifolds as myself and has generally found them disappointing. Some cars do work very well, but it is difficult to suggest a proven method. Stephen Done's car with the PE manifold is excellent, but notably when I had a hybrid TD04L with stock headers it spooled up earlier than his standard TD04L with PE manifold. My car has always spooled up quite early (I used to get 19 PSI at 2400 RPM on the orginal TD04L so perhaps my CR is a bit higher than average - the flip side of this if true may explain why I have had to pull a lot of timing at high boost compared to some others with similar cars).

harvey

iTrader: (48)

Nah John !!! Just put in more Broquettes.!!!
Anybody going tubular should give serious consideratin to the headers like mine which also came ceramic coated inside and out.
The effect with the new turbo will further prove their worth or otherwise and I have kept my ported headers in the meantime just in case.

dowser

I've found fuelling and ignition between 2 and 3k has a significant effect on spooling with the PE manifold, less and more worked for me. So much so that my 'on it's way out anyway' clutch now can't hold on in 4th and 5th (Mark - have you got flywheels in stock? )

Richard

PS: you completely lose the Scoob sound with the PE item - it basically sounds like a very big engined bike.

[Edited by dowser - 10/21/2002 10:39:45 AM]

StephenDone

Speaking to others about the manifold, it's effect depends on the size of turbo that you have. It works extremely well with small turbos, such as the original td04 or slightly larger - spool up actually improves. When you have a very big turbo, the spool isn't as good.

It seems in all cases though that the midrange improves greatly.
You can add in more ignition advance if you have that option too.

Side effects seem to be much higher airflow with lower manifold pressures. Confusing to the punter with a boost gauge, but reassuring to someone watching actual air flow. Due to less air queuing in the intake, due to better extraction of exhaust gases.

Noise drops dramatically, completely losing burble. This may or may not be to your liking. I like stealth, so this was right up my street. 311 BHP, 308 LBFT at dyno day this month.

Cheers

Steve

dowser

Yep - with a vf23 I didn't gain or lose anything over spool up with the OE manifold. But playing with timing and fuelling brought it up quicker.....assuming the slipping clutch wasn't adding to it....will see Friday night.

Richard