Jump to content


Photo

Z22Se Standard Exhaust Manifold Modifications


  • Please log in to reply
24 replies to this topic

#1 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 05 July 2020 - 08:11 PM

I was able to get a new (secondhand) exhaust maifold from a member on here.
The following details what I did to modify and get rid of the hateful EGR take off on No.4 cylinder.
I am aware that equal length manifolds and various configurations (4-2-1, 4-1) are both available and an improvement on this boat anchor, but I like to make the best of things. And I have a ton of time on my hands.

The first operation is to remove the manifold to downpipe studs. Penetraing oil overnight and the 'double nut' method was used to get them out.
ec39b91348424720.jpg

Next was the obligatory weighing: 4.649kg
85cba11348424743.jpg

Casting flash is dead weight, as is the comically thick boss for attaching the heat shield lower bolt to.
31f0df1348424759.jpg

More flash removal
38bd4c1348424777.jpg

Immediatley we have lost dead weight: 4.498kg now - 0.15kg of nothing removed.
4cd68a1348424799.jpg

Some pre modification shots showing surface roughness:
1292271348424819.jpg

ac14721348424832.jpg

8e73e91348424853.jpg

5543ee1348424873.jpg

07881b1348424895.jpg


With the outside shaved it is time to turn attention to the important bits.
Some calipers can help you transfer the dimensions of the port to a drawing or a table to make sure you match all the ports to the same dimensions. Clearly this will be limited with a cast manifold due to the 3D shape the ports take, as opposed to nice tubular manifolds, but you can do the first inch or so with care.
b24a481348425057.jpg

c396c11348425078.jpg


There are two schools of thought (and both have merit) on exhaust ports - 1. you match the manifold port to the head's port and lose no energy in the transition OR 2. you leave a step, whereby the exhaust port is slightly smaller than the manfold port and lose energy in the spreading jet flow that ocurrs, but have some defence agaist unwanted high pressure waves reflecting back up the manifold (anti-reversion lip is a name used for this).
I recommend using bore guages for this rather than calipers, but you can use calipers.
5d63cb1348425101.jpg

98ebe31348425118.jpg

You can see the exhaust port is smaller than the manifold port, and for no reason other than trial-and-error i'm choosing theory 2 here; Anti reversion. The reasoning here is simple - you can grind a bit out, but you can't grind a bit back in.
b205311348425141.jpg


With the manifold ready it's time to fit a plate into the EGR channel and tack it up.
d4063a1348424918.jpg

Adjust to length (leave a lip, dont dig intothe manifold surface)
9c84a61348424960.jpg

Lay weld on the back
3f193c1348424994.jpg

Add metal to the port:
89a5ea1348425020.jpg

#2 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 05 July 2020 - 08:23 PM

you'll need to re-shape no.4 manifold port:
ec25311348425324.jpg

Apply some engineers blue:
bac0871348425338.jpg

Scribe off an exhaust gasket (I have no in-progess photos):
21c9f81348425347.jpg

Then it's time to get stuck in to the manifold ports and pipes with a cutter and sanding mandrels to get rid of the surface roughness:
e50e851348425372.jpg

Two shiny shots:
e6e49f1348425399.jpg

bb192c1348425414.jpg

The all important weight: 4.415kg
f34aec1348425427.jpg

Gasket in position (marked, but not dowelled - I elected not to do that for now)
7926771348425451.jpg

Comparion of the manifold from the car:
b6bcd01348425476.jpg

Three pictures of the manifold on what I believe is a Tullet downpipe and cat (let me know if i'm wrong, please):
afa3531348425499.jpg

4af8511348425518.jpg

e124c61348425529.jpg


WHATS NOT SHOWN: The 'bumps' in the manifold ports that allow casting thickness and clearance for the manifold studs were also shaved down during the port smoothing.
Prior to removal they can be seen in the first post during the measurement phase - the paint was used to highlight them.


How does it feel? It feels better in the mid-range, but thats using a bum-dyno and I also removed the EGR from the software and that could affect it.

Edited by blackoctagon, 05 July 2020 - 08:25 PM.


#3 smiley

smiley

    Thetan level 15

  • 10,324 posts
  • Gender:Male
  • Location:Netherlands

Posted 05 July 2020 - 08:41 PM

Interesting.

Your downpipe looks oem. Tullet is stainless.

 



#4 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 05 July 2020 - 08:48 PM

Okay, i'll take that onboard.
So the OEM system is a flexi pipe (thats what's under the wrap) that goes down into a small welded-in cat?
The part does not look OEM, and i was told by the previous owner it was Tullet, but that was maybe only the backbox (it is certainly not OEM). It has no sign of the pre-cat, or having anything removed inside.
However, if it not a well-regarded part (so it is OEM) then i'll feel better about scrapping it when I make the 4-2-1.

Edited by blackoctagon, 05 July 2020 - 08:49 PM.


#5 smiley

smiley

    Thetan level 15

  • 10,324 posts
  • Gender:Male
  • Location:Netherlands

Posted 06 July 2020 - 07:19 AM

When the precat has been removed cleanly, it will not show any traces of previously being there.

 



#6 Arno

Arno

    Need to get Out More

  • PipPipPipPip
  • 1,216 posts
  • Gender:Male
  • Location:Netherlands

Posted 06 July 2020 - 08:01 AM

Nice work!

 

Hopefully the manifold won't develop the classic cracks on/in the 'Y' sections like many do.. :(

 

Bye, Arno.



#7 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 06 July 2020 - 11:32 AM

The new manifold is sound - I had a look in each valley, top and bottom, for cracking.

The manifold that came off the car also appears to be in good condition, although i've not cleaned it up thoroughly yet.
I'll probably just sell it on after i've got the dimensions from it, as I don't feel there is a 'Mk.2 modified part' to be had from the cast manifold.
It's a grim design and I doubt the development team were proud of it, other than it meeting emissions specifications.

#8 smiley

smiley

    Thetan level 15

  • 10,324 posts
  • Gender:Male
  • Location:Netherlands

Posted 06 July 2020 - 12:10 PM

It was fit for purpose on the Vectra/Astra. and just ended up on the VX, as part of the Z22SE package.

Luckely that makes them p*ss cheap to replace for other oem.

 



#9 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 06 July 2020 - 12:42 PM

I know - i've been there. Still heartbreaking when you have see a sub-optimal part go out the door though.

I've taken the part as far as I can, or at least as far as I can be bothered.
Finding out that downpipe is not a good one has at least meant that I can make the 4-2-1 now without worrying about expensive waste.

Edited by blackoctagon, 06 July 2020 - 12:42 PM.


#10 smiley

smiley

    Thetan level 15

  • 10,324 posts
  • Gender:Male
  • Location:Netherlands

Posted 06 July 2020 - 12:52 PM

You planning to make a 4-2-1 to mate with the oem downpipe, or will you also custimize that one?

If you do manage to pull off a 4-2-1 within the available space, you may thing about creating more and put them up for sale.

 



#11 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 06 July 2020 - 01:18 PM

Keeping a cat on the car means that the primaries and secondaries will be sub-optimal without cutting into the car's clam, and i'm drawing a line there.
The primaries will be around twice as long as the OEM, the secondaries around a OEM-cat's length, then you need some length in the tertiary before the cat, otherwise you get a nasty reflection wave right back into the secondaries. You still will, of course, but you can place it to leave some distance, and hence wave travel time.
The design I have in my head will be significantly better than OEM, but not as good as having a free hand on the packaging. But it's a road car for me.

I would consider moving the cat to the backbox space to lengthen the secondaries and put a bend between the tertiary and the cat matrix. The bend between the tertiary and the cat would slightly attenuate the reflection wave strength (not by much though).


I would not be producing them, but i'm happy to let someone else do it if they like the design.


I did have one ineresting/cost-reducing idea though - I had a Citroen AX GT a long time ago. It had a 4-2-1 manifold from the factory by using a single-looking downpipe, which was actually packed with two semi-circular pipes. From the outside it looked like a 4-1, but the 2 was in the downpipe and the tertiary came before the flexi joint.
It still leaves the manifold as a problem, as it's 1-2, 3-4 pairing is not great and I can't see a path to changing it without heavy modification, and that effort is probably better spent on a new manifold.

#12 oakmere

oakmere

    Scary Internerd

  • PipPipPipPipPipPip
  • 2,114 posts

Posted 06 July 2020 - 07:55 PM

I use the tsudo header (weapon r) from the US to form a 4-2-1 system. It is far from optimal but works much better than the OEM and is cheap and reliable. Do a search there is quite a few examples.

#13 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 09 July 2020 - 10:35 PM

Thank you for pointing me to that - i've had a cursory look and it looks like it would fit, albeit with some downpipe surgery.

I'll see where they are for sale.

#14 vocky

vocky

    Moderator

  • 11,965 posts
  • Gender:Male
  • Location:Earth

Posted 10 July 2020 - 03:36 PM

thats not a standard downpipe/car section, the cat is similar to the Tullet, so probably is a Tullet



#15 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 10 July 2020 - 10:34 PM

Thank you for weighing in on this.
I have one count for and one count against.
It certainly does not have the hallmarks of an OEM/mass produced pipe, but I have no point of reference, and it is a Lotus with all that that entails.....
I do believe it is an aftermarket piece, and the previous owner said it was Tullet, but ill hold tight in case anyone else wishes to speak up.


It dosn't matter so much now as I ordered a 4-2-1 from California today, so when the time comes i'll either be selling a manifold and Tullet, or a manifold and OEM.

#16 The Batman

The Batman

    Super Moderator

  • 30,247 posts
  • Gender:Male
  • Location:FLD mum's bed

Posted 11 July 2020 - 03:08 AM

it doesnt look oem but looks way to big to be tullet, here is a pic of tullet 200cell downpipe

 

JFPko8u.jpg



#17 smiley

smiley

    Thetan level 15

  • 10,324 posts
  • Gender:Male
  • Location:Netherlands

Posted 11 July 2020 - 08:09 AM

Did i miss a lesson in science class?
How does a stainless pipe get rusted?

 



#18 aquilaproejct

aquilaproejct

    Member

  • Pip
  • 234 posts
  • Location:Australia

Posted 11 July 2020 - 11:13 AM

Not all stainless is created equal. 😉

#19 blackoctagon

blackoctagon

    Member

  • Pip
  • 98 posts
  • Gender:Male
  • Location:Lothian

Posted 12 July 2020 - 10:25 AM

Smiley,
Most stainless steels will take a light film of corrosion if they are heat cycled in an oxygen containing atmosphere. There are plenty of grades that stay quite 'metal looking' and a lot that take an oxide layer.

The stainless that OEMs use is often a 400 series and it can look okay for along time, but aftermarket will often use 300 series stainless and they behave differently (they even behave quite differently to each other).

The downpipe is one of those grades. I have access to ways of testing, but i'm not bothered now that i've sorted out where I am going on the exhaust idea.
I might take it to work when it is next off, just to answer the question though.

#20 martinf

martinf

    Member

  • Pip
  • 90 posts
  • Location:Wiltshire

Posted 19 July 2020 - 07:13 AM

Thank you for weighing in on this.
I have one count for and one count against.
It certainly does not have the hallmarks of an OEM/mass produced pipe, but I have no point of reference, and it is a Lotus with all that that entails.....
I do believe it is an aftermarket piece, and the previous owner said it was Tullet, but ill hold tight in case anyone else wishes to speak up.


It dosn't matter so much now as I ordered a 4-2-1 from California today, so when the time comes i'll either be selling a manifold and Tullet, or a manifold and OEM.

 

Hi, I'd be interested to know what 4-2-1 you have ordered from the US, would you be able to post a link? Thanks.
 






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users