Possibly eating my words .

discopotato03 · Post by **discopotato03** » Tue Jun 03, 2008 7:49 pm

Hi all , possibly the next to do on Ellie will be the exhaust and it seems people in the know are saying go with 2.5" tube size .

After a bit of research some of the more realistic WRX's are using 3" from the turbo to the last joint and gently reducing down to 2.5" through the last muffler .
The logic is supposed to be that the exhaust gas temperature falls rapidly (quoted figures by Michael South were 60% in the first 300mm from the turbo) so the 2.5 bit allows for the density drop and stops the gas speed falling too far down the back .
The interesting thing is that he was measuring no pressure difference in the front of the 3" exhaust regardless of whether the last section was 3" or 2.5" .

My thoughts are that even a good spec EA82 is no EJ20 so being 200cc's smaller and not breathing as well possibly 2.5"/63.5mm tube (2 3/8 or 60.3mm ID) could just be the sweet spot .
Michael likes HiTech mufflers which I've used in the past and even makes dump pipes for the JDM Twin Scroll turbos ie VF36/37/38 . The dark forces in my brain are agitating for a TS BB VF38 and seperate pipes from each head to the TS turbine housing should not be to hard to make .
If the funds don't stretch then a fresh TD04 wouldn't be too foul either .

Cheers A .

steptoe · Post by **steptoe** » Wed Jun 04, 2008 9:07 am

having 2 1/2" from cat through to tail on mine I'd reckon any more diameter anywhere would be a pain more than anything else clearance wise

discopotato03 · Post by **discopotato03** » Wed Jun 04, 2008 9:58 am

From what we saw when the down/cat pipe was out there is lots of room behind the turbo , I agree that from the first joint to in front of the rear NS axle is a bit cuddly .

Yesterday I was looking at 3" Rex exhaust pic's and some of those had a long "hot dog" shaped muffler behind the first joint , I'd be looking real closely up the guts of anything like that to make sure it wasn't any significant restriction .

Anyway packaging exhausts is a bit of an art and the rally people are good at it because if its not done properly they soon get torn off . They needed to be as high as possible and any edges like the front of a muffler need skid plates welded on so they don't catch on things and get left behind .

More research , cheers A .

discopotato03 · Post by **discopotato03** » Wed Jun 04, 2008 10:06 am

From what we saw when the down/cat pipe was out there is lots of room behind the turbo , I agree that from the first joint to in front of the rear NS axle is a bit cuddly .

Yesterday I was looking at 3" Rex exhaust pic's and some of those had a long "hot dog" shaped muffler behind the first joint , I'd be looking real closely up the guts of anything like that to make sure it wasn't any significant restriction .

Anyway packaging exhausts is a bit of an art and the rally people are good at it because if its not done properly they soon get torn off . They needed to be as high as possible and any edges like the front of a muffler need skid plates welded on so they don't catch on things and get left behind .

More research , cheers A .

discopotato03 · Post by **discopotato03** » Wed Jun 04, 2008 10:22 pm

Been in contact with Michael South of MSR because he apears to have some good ideas with production class rally Impreza's .

This is a good read .

Cheers A .

discopotato03 · Post by **discopotato03** » Wed Jun 04, 2008 10:26 pm

Been in contact with Michael South of MSR because he apears to have some good ideas with production class rally Impreza's .

This is a good read .

http//www.msengineering.com.au/exhaustsystems.html

Cheers A .

chubby37 · Post by **chubby37** » Fri Jun 06, 2008 8:59 pm

i spoke to a guy at a shop and his advice one time was anything over 3in on a standard turbo car would reduce back pressure to the piont of loosing power.he mentioned an open 2.5in exhuast with hi flow cat...open by way of using as good a cannon or open muffler as you can get...well he also said that a turbo car dose not really need a muffle as it does not produce the same db range as a none turbo car like an EJ22..its more air pushing then engine noise if that makes sense....

discopotato03 · Post by **discopotato03** » Sat Jun 07, 2008 11:01 am

The value of "back pressure" is an urban myth - it does nothing positive for you NADA .

All exhaust systems of any worth have a "tuned" section at the front and generally everything behind that should have low pressure/restriction .

Where this theory comes undone is in the "modern" emissions and now noise era . A production car is tuned closely around what it has std meaning from the filters air intake to the tip of the exhaust . Exhaust pressure is taken into account because of how it affects things like EGR .
This is why often turbo cars get a performance increase from less restrictive exhausts but you need to be careful because this changes the way the engine runs and you have to hope that its fueling and timing control systems will cope with the changes .

What the uninformed have to accept is that overly huge exhaust systems reduce performance because the exhaust will stop and reverse direction if it has no momentum ie velocity .
Remember in basic terms a piston engine is an air pump , it doesn't pump very well if the gasses are reluctant to travel in the right direction .

Cheers A .

Gannon · Post by **Gannon** » Sat Jun 07, 2008 11:36 am

discopotato03 wrote:The value of "back pressure" is an urban myth - it does nothing positive for you NADA .

You hit the nail on the head there. A lot of people simply wont believe me when i say things like that. They say an old mechanic told them back pressure makes power. And they wont believe anything else.

jzk25 · Post by **jzk25** » Mon Jun 09, 2008 10:07 am

discopotato03 wrote:.
The dark forces in my brain are agitating for a TS BB VF38 and seperate pipes from each head to the TS turbine housing should not be to hard to make .
If the funds don't stretch then a fresh TD04 wouldn't be too foul either .

Cheers A .

A TS turbo is not going to work as intended on an EA82 because of the siamese exhaust ports. The TS requires the pairing of opposed cylinders in the firing cycle to evenly space the exhaust pulses into each scroll. This is not possible with siamese ports.
VF38's are not ball bearing either. They were also replaced with a TS TDO4 around 05 sometime.

A TDO4 or TFO35(if you want better response) is a logical choice for an upgrade and cost very little. A better header design would probably help too.

2.5" tubing is more than enough for an EA82T but you could use 3" at the turbo tapering off into 2.5".

schultzie · Post by **schultzie** » Mon Jun 09, 2008 8:09 pm

i have a 3" all the way no cats with a 25mm dump pipe. and a turbo muffler car is legal noise wise and being 85 cats arent needed

also turbo is a high flowed standard job

discopotato03 · Post by **discopotato03** » Mon Jun 09, 2008 9:30 pm

The Mitsuibishi turbo your talking about is a TD04HLA-19T .

Like the VF36 the VF38 does use a ball bearing center section , it's the VF37 that's virtually a plain bearing twin scroll clone of the VF36 .

Yes you don't get the full advantage of the twin scroll system but the turbine does get four less molested exhaust shots and the ganged waste gate flat valves have far more combined area and only two cylinders to control .

Cheers A .

jzk25 · Post by **jzk25** » Tue Jun 10, 2008 9:07 pm

How do you know a VF38 is ball bearing? From googling it or from actually seeing one.

The VF38 is not in the same family as a 36/37. It is a completely different turbo.
There is no harm in using a VF38 but I don't think you will get any benefit from it and you will only add complexity to the headers in doing so.
The wastegate ports are tiny, there area combined would not be any bigger than a TDO4L's single wastegate.

discopotato03 · Post by **discopotato03** » Wed Jun 11, 2008 11:06 am

If you look around that's what they are advertised as having .

Twin scrolling and four cylinder engines .

The idea is to group cylinders 1-4 and 2-3 in an inline 4 with 1342 firing order . From that firing order you can see that you will have each cylinder exhausting into each side at 360 crank degree intervals (remember the 4 stroke cycle needs two complete revolutions per cylinder or 720 crank degrees ) .
What then happens is each exhausting cylinder has the longest period to blow down through its half of the divided turbine housing and the next (in each pair) will be venting into an area of lower pressure . With an open or single scroll turbine housing each cylinder is venting into an area of higher pressure so not as much velocity per cylinder is available to drive the turbine .
The flat fours firing order is different I think 1324 so to twin scroll them as you said the front and back pair of cylinders needs to be grouped together to achieve the same thing - if you have separate exhaust ports .
Technically you can do this to an EA82 head by using a divider plate up the middle of the exhaust port but getting it to seal on the port divider would not be easy .

If you run two engine pipies from the siamesed exhaust ports the effect is not the same because you are only getting 180 crank degrees between each bank having an exhaust event .

If you look at the pics of the TWE EA82T headers at USMB you'll see that they run two engine pipes to a collector just before the turbo's mounting flange . It would be a simple matter to lose the collector and have the engine pipes welded to the twin scroll turbos twin entry flange plate .

Out of time , cheers A .