lizzard

Can any one enlighten me as to which is actually the better downpipe. I have seen both and know about the difference in the metals used. Besides this the HKS has the half where the waste gate would open blanked off where as the Scoobysport goes into a chamber then to the 3" downpipe. Why is the HKS so different in its dedign? The original downpipe from the MY02 is shaped like the HKS aftermarket downpipe. WHY?

I would love to get some feed back as I am looking to buy A HKS Super Dragger however I want the best and also looking at the Haywood & Scott stainless steel one.

Thanks

Mickle

You can mix and match the HKS to the H&S you know!

I've got the full HKS but as to which is the best ???

alanjack

Had both and HKS wins

Midmotorsteve

Super Dragger maybe top of the range but the hiper mufflers HKS's performance system, can be a bit droney apparently.

ptholt

The Hayward and scott downpipe flows more as was proved when our car was linked, the hks down pipe we had originally restricted how far we could go, whereas the Hayward and scott we could go beyond the limits of the hks when we fitted it and went back for a remap.

The hks Super Dragger is a lovely exhaust, but if its outright performance you want then you would be better with the Hiper muffler though it is a fair bit louder just depends if you like that sort of thing

HKS Hiper

HKS Super Dragger

[Edited by ptholt - 1/26/2003 11:58:40 AM]

martin850

iTrader: (51)

I have got an HKS Hiper and I can honestly say that it is a fantastic system with a great sound. I am looking to also get a de-cat down pipe like you but I am also baffled by the different types so am interested in the responses you get.

PICKLE

I've heard stories of the HKS downpipe being about an inch too short when fitted to a different mid-section! If the whole HKS system was to be used then this probably won't be a problem!
I've got the obligatory SS downpipe mated to HKS Hiper and it fits a treat

ptholt

The only time i've had problems are with uk bugeye cars which when decatted led to hks exhausts fitting short.
There is a piece which now rectifies this.

Bee

I've got an HKS Super Drager system on my MY99,not too loud. As said before, if your after greater performance then the Hiper is the one to get. Not as good to look at though IMHO.

I'm looking to get a DP shortly, prob either a Magnex or Scoobysport, would bodyswerve the HKS though....

The TunnelMeister

Hi Lizzard, I sent you the pictures of a ScoobySport D/P, you not getting one made now?

Some figures for you for what its worth:

P1 - Blitz LM induction, full decat inc. Scorpion CLOSED face d/p (as HKS) 297bhp 278lbft

P1 - Blitz LM induction, full decat inc. Scoobysport OPEN face d/p 326bhp 270lbft

Same car,no other changes, same RR, second figures are from today.

You have pictures of this actual d/p.

I'm now working on getting the torque back up, to say.. 300lbft.

This help you choose then?

Steve.


[Edited by The TunnelMeister - 1/26/2003 5:30:50 PM]

lizzard

Thanks for the replies

I looked at the original MY02 Sti7 downpipe and the HKS downpipe. The flange that matches up to the turbo housing are identical. The downpipe flange face section of both the HKS and the original have a 5" flat surface which then goes into a 3" mandrel bent pipe. The waste gate bypass air gets into the exhaust downppipe by the fact that the wastegate is recessed into the turbo housing so there is actually a small space between the downpipe face surface and the turbo.

The MY00 original downpipe however is made up very differently. There is a shallow "bowl" shaped area on the downpipe that the wastegate air flows to. In otherwords on the MY02 the bypass air has to turn 90 degrees to the right as it comes out of the wastegate and then 90 degrees to the left to mix with the exhaust air and continue through the downpipe. On the MY00 the wastegate bypass air flows into the shalow "bowl" before mixing with the exhaust gasses.

The Scoobysport downpipe has made the "bowl" area much larger and the entire flange area which is about 5" in diameter tapers to the 3" downpipe in one smooth transition; like a funnel.

Obviously the biggest restriction in the original downpipes on either the MY00 or newer MY02 is the catalytic converter and this is where most of the power gains come from whrn it is removed.

I would really like to know why Subaru changed the face of the downpipe frim the MY00 to the MY02.

The reason for mandrel bends in the exhaust is to increase the exhaust efficiency by reducing the losses in velocity of the gasses as they negotiate the bends in the exhaust.

For this reason I am unsure as to why Subaru would want the wastegate gasses to go through these large angular changes over these very short distances which will reduce its velocity. Can it be something to do with helping to controll the spool up (spiking)?

It would be very interesting to hear from someone out there who would have a more technical background in turbo designs and the airflow characteristics.

I will try to post some pictures to assist with the above info.

It would be interesting to see some dyno tests with the identical exhausts but with a HKS downpipe VS the Scoobysport one. This would then prove which design is really better.

lizzard

The TunnelMeister are you the same as Phil ?

Thanks this really does help.

I was composing my essay and did not see your post

I wonder why the slight loss in torque with the Scorpion d/p?
Clearly the scoobysport is the better one for hp. What other mods do you have on the car and what type is it ie WRX or STi and year?

Which downpipe pictures would you like?

You can email me at jdefreitas@wow.net

The TunnelMeister

Hi Lizzard, Steve here again.

I was pointing out that you asked for some d/p pics and I posted some for you. They were of a ScoobySport, 3" to 2.5" open neck version, made by Hayward & Scott.

If you would like more technical info about d/p's go to 22b.com where there is an excellent Topic on the subject.

Open/Closed.... I was originally very sceptical that there would be much difference if both were decat versions. Today's rolling road test proved me very wrong!

Higher bhp but lower torque with the ScoobySport version.... open neck/larger bore has this effect. Balancing the two is the modifiers search for the Holy Grail & what keeps everyone going!!!

An open neck 2.5" would probably hold the torque a little better with slightly less bhp.

The car I run is a Prodrive P1, a slightly modified UK version of the STi 5 2 door. (see Prodrive website for details)

Those I listed are the only mods, ie Blitz LM induction & ScoobySport/Scorpion zorst.

Hope this helps,

Steve.

lizzard

Thanks Steve

I am going back to the threads to find the pics that you posted as I never did see them.

AH HA !!!

You post here under two titles so that had me a little confused!!!

Found the link!!! and the pics !!!

It seems though it would be better to find a used one in the UK as you suggest and send it here...da you have any one in mind who has a Scoobysport to sell?

Thanks again.

The TunnelMeister

Decat downpipes are very sought after on Scoobynet.

I'm afraid it's a case of posting in 'Wanted' and also watching the 'For Sale' section very closely. You will prob. get one for around £150.00 GBP plus shipping.

There is a twin dump d/p for sale at the moment though I've no experience of these. Perhaps some of the other guy's can advise???

I will keep a lookout for you.

Steve.

siwrx

speaking to scoobysport about this and they say it depends what you want, their pipe gives more bhp but less torque, the hks gives some back pressure so low end torque is upped

P1 Owner

Lizzard, HKS Hiper on the P1 m8' its the dogs danglies... Vroom Vroom!

lizzard

From Steves post above it seems that the HP went up by 29bhp but he lost 7 ft/lbs torque by replacing the Scoripon with the Scoobysport d/p. Does the increase in bhp outweigh the loss in torque?

What do you think Steve, and how are you going to get the torqur back up?

Pete Croney

You really need to look at the whole graphs to get the full picture. If they can be posted up, it will show a much more accurate picture.

A small exhaust, or one that is restrictive, will give more peak torque but this will tail off quickly as the flow exceeds the ability of the pipe.

If the runs were not done on the same day then 7lb difference is negligable.

What is more relavent is how wide the torque curve is. BHP is Torque divided by 5252 times revs, so assuming peak power was at 7000 rpm, the HKS had 222lbft of torque at 7000rpm and the Scoobysport had 245lbft at the same point. The other point that isn't noted is where peak torque occured.

The other thing to look at on the graph is the point where usable torque was first achieved.

The aim is to have as much area under the torque curve as possible. This creates the most drivable cars.

Steve_F

Hello Pete, seems a long time since 'Catalunya' !!! You may recall Banshi & I had the stickered P1's? I hope you are well.

The comparison above (Scorpion & S/Sport) is from my P1.

The 297 bhp & 326 bhp were on different days though similar conditions, same RR.

Five runs were done, this included two 'warm-ups' at 'standard' which gave an average of 312 bhp on the day. (the last 3 were 308, 326 & 326 bhp)

Below are the torque graphs which bear out what you say.




A similar shape at 300 lbsft would be nice?

Will be keeping the Scoobysport one.

Hope to see you at an event soon.

Cheers

Steve.

JIM THEO

I wonder why a small splitter in the open neck downpipe (as Scoobysport or H&S are) gives such big difference on spool up times-driveability-torque as Michael (MSR in Australia) asserts and so many customers confirm?
I guess that at lower revs where wastegate is closed (almost!) this helps by creating some backpressure while in the higher rpms when wastegate opens more and more there is no restriction as the splitter is small and the gasses flow now free.
Pete or anybody else did you try a similar design downpipe (Janspeed bellmouth) with splitter and what are the results?
JIM

lizzard

Thanks guys for all the help. I am trying to decide now between the KHS Hiper with a Scoobysport d/p and a Hayward & Scott stainless system with their d/p which is like the Scoobysport one.

Any one out there with views on which is the better system?