Piper Exhausts turbo downpipe development thread

[PiperRS]

Hello all!

As many of you know we manufacture an exhaust system for the M100 Elan and its proved quite well, We also do the pre-cat eliminator. the only part we dont do is the turbo elbow/downpipe.

Recently we have seen a lot of interest in this part, so we have decided to start development of it.

We have got to the stage where we need professional advice - YOURS! We want your comments/feedback on this, im aware that a few others have developed these, if anyone has fitted some we would like to hear feedback on them and see where we can improve, there appears to be two types:

a single - large entry, reduced down
a twin/bypass - two entry pipes, that join together later down the pipe.

I would like to know which design seems to work best, pros and cons of them?

Anything that we should be aware of before we start developing the part? I have a car that i have been told is standard with just a mountain chip. This will ensure that we are working from true measurements to start with to ensure the best fitment when fitted to either your standard system or your Piper exhaust.

If anyone has any comment on this please post them below, I look forward to hearing from you.


Kind regards
Tom Edmunds
Piper Cams and Exhausts

[Avonvilla]

Am i correct in thinking this will replace the pre cat housing too ?

[HJ2]

Am i correct in thinking this will replace the pre cat housing too ?

Very

[saska]

a single - large entry, reduced down
a twin/bypass - two entry pipes, that join together later down the pipe.
I would like to know which design seems to work best, pros and cons of them?

It's been a long time since I did fluid dynamics at uni but airflow from a turbo spinning at 180,000 may be similar so here goes.
1. First off the single pipe is probably lighter.
2. The std turbo wastegate is 15-16mm but lots of people have ported them to 20-21mm (to prevent boost creep with free flow exhausts -- like yours) so in either design a 21mm wastegate design should be implemented. If you make a twin pipe system where the wastegate pipe is much larger then the flow will expand and slow down so will cause a lot of turbulence when it re-enters the main pipe when the slow gases mix with the fast ones. If you make it smaller then the flow will speed up -- or you'll get boost creep. Ideally the wastegate pipe in a 2 pipe system ought to be the same as the wastegate port. Given you're looking at making a design for many different cars then i'd think doing the wastegate pipe at 21mm should work well for all applications.
3. Given the wastegate pipe is only going to be employed when the boost reaches 0.9 Bar (Everest) the twin pipe system will produce more turbulence than the single pipe under <0.9bar conditions since there is always a big hole where the wastegate pipe rejoins the main pipe. So the exhaust gases will expand and then contract back into the exit pipe to exhaust -- lots of turbulence. In a single pipe system the wastegate hole should be volumetrically much smaller so less impact on the flow and it is also much higher up. Much less turbulence going into the exhaust.
4. As always, things are a compromise, i'd think from a driveability point of view the single pipe system would work well. From a performance point of view (>0.9Bar) then the twin pipe system would probably edge the single pipe system.
5. Were it me I'd look at re-introducing the wastegate pipe in the 2 pipe system a bit higher up -- just above the bottom pipe weld in the second photo so both flows were going in the same direction when they meet. If you get the second wastegate pipe the correct diameter then the gases should merge at pretty much the same speed.
2p

[Monty]

I have the Stiffy fitted which is the single large entry, it also has a bracket which attaches to the engine block to prevent movement. I have no ideas on which is best as i have no ideas on flows etc and i only did a rolling road after which was 206 bhp at the fly with Everest chip, 2 1/4" pipe and the stiffy. Best thing about it makes for working on the car easyer, ie it`s smaller than the cast lump, easyer to remove when doing turbo work or removing the head etc and saving on weight.

BTW, mine is made of stainless and is ceramic coated

Some pic`s here
viewtopic.php?f=79&t=2737&start=160

[steve matthews]

Tom, The dyno tells all.

Peco 2.25, K&N inlet, Everest chip, Pce, no main cat.

Prior to install of Fed. down pipe.
194 Wheel hp, the only hp that counts.
This required 14.97 lbs of boost to create the 194 Wheel hp.

After install of Fed. down pipe.
200 Wheel hp, the only hp that counts.
This required ONLY 13.6 lbs of boost to produce.

I now have a net gain of 1.37 lbs. of boost ready to be taken advantage of.
Also by coating with the White Lightning interior temperatures at the turbo
down pipe decreased 400 deg. No heat shields required.

Performance of the Fed. down pipe = V-6 and some V-8 engines.
Instant throttle response allows the turbo to now spool low in the rpm range.
This lets you (BURP) the engine, small quick spurts of turbo around the auto cross
course.

This pipe will make you re-learn how to drive the Elan fast.
As for the Technology behind this design, KnoxMotorSports will have to answer.
I will say a good amount of time went into the development. The questions you
are asking have been asked before and answered by one resource or another.
Knox has done their homework, hopefully Billy or Lawrence will chime in on this
debate, me I am just the driver.

Steve

[steve matthews]

Also forgot to mention.
IT LOOKS GOOD

[bobbrown]

Here's a bit of information from a turbosystems engineer at Garret.

Turbo Exhaust.pdf

[superbad]

Here's a bit of information from a turbosystems engineer at Garret.

Turbo Exhaust.pdf

Look at that, actual engineering input. That is a great read.

[Karl Martin]

Very interesting reading from Saska and Bob, with somewhat conflicting ideas as to the distance that the waste gate should join the turbo discharge flow pipe.

All the racing fraternity I have spoken to have told me that the best solution is to completely separate the two (as in Bob’s link), you can even vent the waste gate directly to the atmosphere, its called a screamer pipe and for good reason, they are ridiculously loud (and illegal).

So could there be a third even better alternative that Piper would consider....run the waste gate pipe next to the turbo discharge pipe all the way under the car and simply join it at the silencer? (or something similar!) It would surely be less complicated to produce, just more material costs?

However, of the above offerings, theory is one thing, tried and proven is another, so my vote still goes to Knox’s design, I am still surprised Billy hasn’t offered to do the production run and have tried to contact him to build one for me, if Steve would allow a replication of his, to see if it would fit the U.K cars without problem, no offence to Piper (I have their twin silenced 2.5” with PCE and very nice it is) but Billy seems to have gone to ground.

[bobbrown]

All the racing fraternity I have spoken to have told me that the best solution is to completely separate the two (as in Bob’s link), you can even vent the waste gate directly to the atmosphere, its called a screamer pipe and for good reason, they are ridiculously loud (and illegal).

Nothing to stop you fitting a silencer to the seperate wastegate pipe, it would then not be as loud.

As I see it there are 3 options

1. single pipe exit
2. twin pipe exit with the wastegate rejoining the main exhaust 12 to 18 inches from the turbo
3. totally seperate system.

The current cast section does keep the two flows apart but only for a small distance from the turbo so I think the best option would be option 2 as per Knox’s design.
As with all things it is always a compromise, option 1 is going to be be the cheapest to produce, option 2 is going to sit in the middle and option 3 is going to get expensive never mind trying to route the pipe.
That said my Elan is easy, I just need a nice 4 into 2 into 1 manifold with 36" primarys and 2" secondarys all the same length not too big and not too small in diameter.

Bob

[Monty]

The current cast section does keep the two flows apart but only for a small distance from the turbo so I think the best option would be option 2 as per Knox’s design.

That said my Elan is easy, I just need a nice 4 into 2 into 1 manifold with 36" primarys and 2" secondarys all the same length not too big and not too small in diameter.
Bob

Or you could always fit a turbo or a SC

[bobbrown]

Or you could always fit a turbo or a SC

A nice set of throttle bodies and a new ECU would probaly give close to 180/200hp with out the aggro of a turbo, I like to press the loud pedal and go

[Brit-Car-Nut]

Very interesting reading from Saska and Bob, with somewhat conflicting ideas as to the distance that the waste gate should join the turbo discharge flow pipe.

All the racing fraternity I have spoken to have told me that the best solution is to completely separate the two (as in Bob’s link), you can even vent the waste gate directly to the atmosphere, its called a screamer pipe and for good reason, they are ridiculously loud (and illegal).

So could there be a third even better alternative that Piper would consider....run the waste gate pipe next to the turbo discharge pipe all the way under the car and simply join it at the silencer? (or something similar!) It would surely be less complicated to produce, just more material costs?

However, of the above offerings, theory is one thing, tried and proven is another, so my vote still goes to Knox’s design, I am still surprised Billy hasn’t offered to do the production run and have tried to contact him to build one for me, if Steve would allow a replication of his, to see if it would fit the U.K cars without problem, no offence to Piper (I have their twin silenced 2.5” with PCE and very nice it is) but Billy seems to have gone to ground.

Hey! Billy and Steve DID offer to do a production run and everyone "over there" put their noses in the air and said such smart things like "it doesn't look right" or The US car is different from ours.

Also, the "Won't the hotter exhaust melt our cars"? This because they coated their pipe , so the heat must go down the pipe to be vented...

The Fed car is extremely similar to the closed circuit SEs and certainly the CAT equiped S2.

I have seen Steve's car after MANY visits to the track and although he has no heat shield, there is no blistering of the paint or plastic around the exhaust and turbo.

I understand that Phil has been working on his pipe with Piper for quite a while but somehow, Billy and Phil and Piper and Billy's shop need to start working together.

Billy never quoted a price because nobody responded to his offer so he could get an idea as to how many to produce. One piece is ALWAYS more expensive to build that a run of 10 at the same time as there are set-up costs and minimum material purchase requirements.

I would really love to see Billy, Phil and Piper get together and look at Billy's designe carefully. Maybe Piper can show some engineering improvements to Billy's design, but they are currently looking at a very early prototype of Billy's that doesn't fit any cars. Maybe all Piper needs to do is produce Billy's pipe for the UK buyers and Billy produce the pipe for the North American buyers.

Just my 2 cents (pence)

[Monty]

Well thats not true, i offered to test it if they could send it over and asked on the cost with no reply

There other reasons too, ie import duty and Vat which comes in at about 25% add on. Piper can test fit to cars with A/C (my pipe won`t fit one with A/C) and with Piper already doing the Exhaust for the Elan the down pipe will become an of the shelf part

But glad Knox have give valuable info on the fed down pipe which we all can benefit from.

(wonder if Piper will do a pipe for the Garrett turbo lol )

[Brit-Car-Nut]

Again, I think Piper production for UK and Knox production for US as the cost to ship to the US is dear and VAT is also dear.

I just don't see why two different groups are trying to reinvent the same wheel.

I doubt Piper would quote you the price for a one-off test pipe any quicker than Knox did.

Once you get the pipe, it is gone for all practical purposes. Knox needed several orders to justify making more.

Unfortunately, one wanted for testing would be a financial disaster.

Does that mean Knox doesn't want their pipe tested? No, just no future if nobody else orders one. They tested it pretty heavily at the track and on Dynos. That data was presented and really should have had everyone drooling and clamoring for a pipe of their own.

That didn't happen, so They went on to other projects, now insulted (my observation) because everyone is jumping on the Piper group where there isn't a price or even a physical pipe.

Why would anyone want to develop anything else in that atmosphere?

I have no relation to Knox Motorsport except to have collected the remains of Steve's M100 from there.

I have seen Steve's car and without any heat shield, it looks to be staying more than cool enough to minimize those that forecast melted bonnets and floors.

I know the UK group is tight knit, but you blew it with a really interesting pipe that unfortunately came from the US.

[esprit888]

I think, and i could be wrong here as it has been known to happen that there is a point being missed here. I have just (as in today) bought this

Impulse RS -1.jpg

and the most prudent thing to do would be to ensure that the pipe fits both cars thereby making it a much larger potential market ( there is a TON more room in the RS impulse, i can actaully put both hands on the pre-cat!) The fact that knox made one is very comendable, but i asked and was never given a price or delivery date so i had to drop it and put my name on a list that appears to be going somewhere (Just my humble opinion) I bought my PCE from piper and dont see the shipping being anything out of line. I would just as happily buy from Knox as i would buy from Piper, if it becomes available, and i dont think i am alone there??? (more on the RS in another thread as i need a turbo ) Make it fit both, now i need two

Again, I think Piper production for UK and Knox production for US as the cost to ship to the US is dear and VAT is also dear.

I just don't see why two different groups are trying to reinvent the same wheel.

I doubt Piper would quote you the price for a one-off test pipe any quicker than Knox did.

Once you get the pipe, it is gone for all practical purposes. Knox needed several orders to justify making more.

Unfortunately, one wanted for testing would be a financial disaster.

Does that mean Knox doesn't want their pipe tested? No, just no future if nobody else orders one. They tested it pretty heavily at the track and on Dynos. That data was presented and really should have had everyone drooling and clamoring for a pipe of their own.

That didn't happen, so They went on to other projects, now insulted (my observation) because everyone is jumping on the Piper group where there isn't a price or even a physical pipe.

Why would anyone want to develop anything else in that atmosphere?

I have no relation to Knox Motorsport except to have collected the remains of Steve's M100 from there.

I have seen Steve's car and without any heat shield, it looks to be staying more than cool enough to minimize those that forecast melted bonnets and floors.

I know the UK group is tight knit, but you blew it with a really interesting pipe that unfortunately came from the US.

[Monty]

I doubt Piper would quote you the price for a one-off test pipe any quicker than Knox did.

Once you get the pipe, it is gone for all practical purposes. Knox needed several orders to justify making more.

Unfortunately, one wanted for testing would be a financial disaster.

Does that mean Knox doesn't want their pipe tested? No, just no future if nobody else orders one. They tested it pretty heavily at the track and on Dynos. That data was presented and really should have had everyone drooling and clamoring for a pipe of their own.

That didn't happen, so They went on to other projects, now insulted (my observation) because everyone is jumping on the Piper group where there isn't a price or even a physical pipe.

Why would anyone want to develop anything else in that atmosphere?

Yet another reply from someone who doesn`t know the facts and trying to cause an issue which isn`t there

Knox had a spare pipe which was iirc there prototype and was willing to send over for test fitting and i put my name forward to test fit and heard nothing and as you can see others were interested but a thread was never started by knox to see how much interest was out there to get a group buy going. If you look at Phils thread you can now see how much interest there is, why? because he started a thread to see what interest there was. Simples

and the UK being tight nit is just bolloxs, we`ve been in group buys and ordered stuff from the US and US have done the same. UK members have a good relationship with US members and some have been over to visit.

This thread is to talk about which Design is the best performance gain, lets stick to the subject

[PiperRS]

[/quote]

This thread is to talk about which Design is the best performance gain, lets stick to the subject [/quote]

Agree!

We are starting production of the downpipe entry flange, this is to have a separate hole for the turbo and a separate hole for the wastegate.

I think the better design will be a separate wastegate tube, but bore size, length and re-entry point are still to be determined.

In this image, you can see where the turbo gases will be heading down the pipe, the wastegate pipe joins and due to the angle of this it looks as though the turbo gases are hitting a right angle and then continuing on, it seems this would be quite restrictive and cause a bit of turbulance in the downpipe, i will lookinto a different desing that introduces the wastegate pipe in a better position.

Anyone have any input on this?

[bobbrown]

I think the picture is of the prototype and did not fit so version 2.0 is different if you look through this topic link you will see version 2.0 has a better entry for the wastegate flow.
As with most things it is a compromise and certainly the best option seems to be the two pipe aproach as the dyno graphs tend to indicate.
The gas flow directly after the turbo is much improved with the wastegate entering further away from the turbo and you no longer get the choppy reponse from the engine as the flow is disrupted as the wastegate attempt to control the boost.

One area you may want to take into consideration is the transition from the outlet from the turbo it's self to the pipe as any step in diameters will have a detrimental effect on flow as it it just another area to create tubulance, better with a trumpet shape but may be difficult to achieve.

Bob