CNC Header Flanges

[RallyBob]

Originally Posted by neuropel If you have a design for a turbo header that you're using in a GT, I'd be interested - steel would be fine but stainless steel would be superior.

Make sure you guys are using the same turbo then. Flanges differ, as do external dimensions, which will affect the clearance to other components.

I think mild steel would be fine, with a similar Swain coating.

As long as it's thick wall, then mild steel will be okay. Schedule 40 (.134" thick) steel pipe is okay in mild steel, but you can use schedule 10 (.109" thick) if you make in it with 304L stainless 'weld-L's'. Regular thin wall (.049" or .065") header tubing is a no-no! Or you can use .065" thin-wall if it's type 316 or 321 stainless, but at that point the materials will set you back $400-500 alone!

[Hiro]

Originally Posted by Gumby I'll send it on my personal name and declare it used then. What is the threshold before they charge you?

less than $100 should be OK to escape custom survey,
Hiro

[Tru-Craft]

I would be interested in a steel flange, my header won't last forever.
How are you planning on cutting the flange?
Plasma, water-jet.....
Thanks for thinking of us.
Lyle

[Gumby]

Originally Posted by RallyBob Make sure you guys are using the same turbo then. Flanges differ, as do external dimensions, which will affect the clearance to other components. As long as it's thick wall, then mild steel will be okay. Schedule 40 (.134" thick) steel pipe is okay in mild steel, but you can use schedule 10 (.109") thick) if you make in it with 304L stainless 'weld-L's'. Regular thin wall (.049" or .065") header tubing is a no-no! Or you can use .065" thin-wall if it's type 316 or 321 stainless, but at that point the materials will set you back $400-500 alone!

haha what no one wants an inconel header?

They'd all likely be built to order because everyone is going to want something different. Alternatively I've given some thought on what it would take to make the header capable of accepting adapter plates so the end user could make the choice of what turbos will meet their needs and still fit.

Originally Posted by Hiro less than $100 should be OK to escape custom survey, Hiro

It's a good thing shipping isn't part of the declared value. Thanks for the info.

Originally Posted by Tru-Craft I would be interested in a steel flange, my header won't last forever. How are you planning on cutting the flange? Plasma, water-jet..... Thanks for thinking of us. Lyle

CNC Mill

[RallyBob]

Originally Posted by Gumby haha what no one wants an inconel header?

How much then?

They'd all likely be built to order because everyone is going to want something different. Alternatively I've given some thought on what it would take to make the header capable of accepting adapter plates so the end user could make the choice of what turbos will meet their needs and still fit.

The issue is that not only does the flange potentially change, but the turbo gets bigger. So it will enlarge in almost every direction, which might prove to be a BIG problem for clearance in already tight confines. I think you need to establish a turbo size you will use, and build that header. Others will have to follow your lead, or build their own header! Too much variation otherwise.

How much power are you honestly looking to make? Remembering a stock 1.9 Opel makes 45-55 wheel HP, is 200 whp a target...or more? The Garrett GT2554 turbo I bought for my Opel wagon can support up to 240 hp, and that's about as small as they come in a ball-bearing T25-style turbo (T25 is the family of turbos, it's defined by the small flange dimensions).

I'm (really!) not trying to complicate things, just bringing some potential issues to light before they confuse matters more and skew the whole project.

Bob

[RallyBob]

This might help:

T25 flange

T3 flange

T4 flange

[Gumby]

Good point. Building the header to fit a small common turbo is probably the best and most cost effective way to go.

200hp at the wheel is plenty from the 1.9 at least for me. I am not sure what everyone wants from a turbo 1.9 but my goal is to make boost nice and low in the RPM range. An increase in torque is what I am really looking for, max hp is irrelevent to me since the engine will never see those rpms on the street.

[RallyBob]

This was the turbo I picked up for my wagon.

Garrett GT2554

[RallyBob]

Originally Posted by Gumby Good point. Building the header to fit a small common turbo is probably the best and most cost effective way to go. 200hp at the wheel is plenty from the 1.9 at least for me. I am not sure what everyone wants from a turbo 1.9 but my goal is to make boost nice and low in the RPM range. An increase in torque is what I am really looking for, max hp is irrelevent to me since the engine will never see those rpms on the street.

Believe me, 200 real whp (not speculated) in an Opel moves right out! We're talking 4x the stock power. We're talking trashed 4-speeds, smoked clutches, busted torque tubes, and blown rear ends.

In order to make a 'big' turbo work on a small lower powered engine, you'd need to modify the engine not only for strength, but for breathing (cam, head porting, etc) so it doesn't run into compressor surge in normal driving conditions.

So as you said, sizing the manifold for a small turbo that can make between 150-250 hp and spool up fast is a better choice. You can increase the hp just by increasing boost if you want to (and if octane + tuning allows it).

Bob

[neuropel]

This is partly why I asked about flanges - the header could be left with a collector so that others can add any flange they want. I'd be good with the T25 flange since space is at a premium in a GT. Good suggestion to go with one flange type and others can either follow or make their own. Getting this in stainless would be pricey I'm sure, but wouldn't it essentially last forever? Any chance they'd come in under $600?

Todd

[RallyBob]

Originally Posted by neuropel This is partly why I asked about flanges - the header could be left with a collector so that others can add any flange they want.

Not so simple as I explained before. The flange dimensions vary greatly, so a collector for a T25 is too small for a T3 flange, and vice-versa. And the location of the collector (and therefore flange) would likely change as the turbo size grows due to clearance issues. I think this is a perfect example of the 'Choose any color you like as long as it's black' mentality you need to make this work. Space is at such a premium you won't have the luxury of making one size fit all.

[Gumby]

Originally Posted by RallyBob Believe me, 200 real whp (not speculated) in an Opel moves right out! We're talking 4x the stock power. We're talking trashed 4-speeds, smoked clutches, busted torque tubes, and blown rear ends. In order to make a 'big' turbo work on a small lower powered engine, you'd need to modify the engine not only for strength, but for breathing (cam, head porting, etc) so it doesn't run into compressor surge in normal driving conditions. So as you said, sizing the manifold for a small turbo that can make between 150-250 hp and spool up fast is a better choice. You can increase the hp just by increasing boost if you want to (and if octane + tuning allows it). Bob

200whp seems like an attainable goal. Besides that brings the power to weight ratio in the neighborhood of 10lbs/hp. That's good enough for me. I just want something more peppy. I am not into street racing.

Originally Posted by RallyBob This was the turbo I picked up for my wagon. Garrett GT2554

Nice turbo but yikes fitting is going to be a little bit of a challenge even with one that small. I am not sure equal length runners is going to be economical/possible without cutting sheet metal. I think we may have to have the turbo close to level with the exaust ports and towards the front of the engine to make sure it can fit without cutting any sheet metal. What are your thoughts Rallybob?

Also what was the price on that turbo?

Originally Posted by neuropel This is partly why I asked about flanges - the header could be left with a collector so that others can add any flange they want. I'd be good with the T25 flange since space is at a premium in a GT. Good suggestion to go with one flange type and others can either follow or make their own. Getting this in stainless would be pricey I'm sure, but wouldn't it essentially last forever? Any chance they'd come in under $600? Todd

Not exactly... most opelers looking for SS would go with 304 which is more durable than A36 mild steel but still one of the cheapest and least durable stainless you could use to make a header. The real reason to go with a better header material is weight and durability. 316, 321, 625, 630 etc can be made progressively lighter because the material is more durable at higher temperatures... but costs will skyrocket with the better metals and obviously there are diminishing gains. Cost of owner ship on a street vehicle will be cheaper for the A36 turbo header even if it has to be replaced a few times during the lifetime of the car. The cheapest I can find 304 is still more than two times the expense of A36... 316 or any of the other alloys are only going to be worse.

[opelbits]

A correctly designed mild steel non-turbo header would be nice. Short of that, I'd be happy with a tubular version of the stock exhaust manifold. Keep the same headpipe flange location so that it could be bolted in place of the stock manifolds and it would fit any 1.5-1.9 Opel.



Does anyone know if a thin copper gasket would work well with the exhaust/intake combo on the Opel? I really liked the copper gaskets used on the Alfa exhaust, but I don't know if it would be good on the Opel given the manifold arrangement. A single gasket like the stock one (is a copper gasket okay for the intake portion?), or a separate copper gasket for the exhaust only (would this cause too much of a problem with a decent seal for both gaskets?)? I don't mind having to make the raised compression rings by hand, that is relatively easy.
Would the copper be good for a turbo set-up?

[Gumby]

It sounds like you basically want a tubular "sprint" manifold.

I think the plain header project is in the works. I'm not heading that one up so I can't really speak for anyone. Personally I think those would be the easiest to make. I still haven't heard back from my welder friend. I'll be calling him tonight and post an update afterwards.

[oppositelock]

Originally Posted by Gumby Is anyone other than Rallybob interested in stainless steel flanges?

You can count me in for a stainless flange for sure. I want to make a header for my rally car and stainless has better scavenging and less radiated heat.

[opelbits]

Originally Posted by Gumby It sounds like you basically want a tubular "sprint" manifold. I think the plain header project is in the works. I'm not heading that one up so I can't really speak for anyone. Personally I think those would be the easiest to make. I still haven't heard back from my welder friend. I'll be calling him tonight and post an update afterwards.

Well, if the regular header doesn't pan out, I think a tubular version of the sprint would be nice. The prices for those are getting high enough to justify checking out the viability of a tubular replacement. The primary tubes could be enlarged a little to mate up to a larger headpipe. It wouldn't be equal length, but it would fit more cars (which might mean more sales and a lower cost?). It might weigh a bit less than a cast iron sprint, too. Unless I did the welding...

[RallyBob]

Originally Posted by Gumby Nice turbo but yikes fitting is going to be a little bit of a challenge even with one that small.

Yup, and most 'junkyard' turbos are even bigger by virtue of their vehicle-specific bracketry and flanges. This is about as small as they get while still flowing enough to make decent power.

I am not sure equal length runners is going to be economical/possible without cutting sheet metal. I think we may have to have the turbo close to level with the exaust ports and towards the front of the engine to make sure it can fit without cutting any sheet metal. What are your thoughts Rallybob?

I gave up on making the manifold for my wagon equal length, as the benefits of making the bends less severe (better flow and faster spool) outweighed the benefits of 'equal length' primaries in a street turbo application. Plus, have you looked at some of the OEM cast manifolds out there? Some are horrid-looking, yet still make very good power.

Also what was the price on that turbo?

I paid $835 for mine last August. Probably more expensive now... got it through TurboKits.com, great to deal with! List price was about $1000 BTW.

HTH,
Bob

[opelwasp]

Would the IHI VF24/24/29/38 turbo fit? Or even Mitsu TD04? A GT/Manta?