Secondary/Collector Sizing

[drxlcarfreak]

This may be a dumb question, but I am working on a twin scroll manifold for a HX-52. I plan on using 1.5" schedule 10 stainless for the primaries, but with the location of my turbo, it makes sense to merge the 1&4 and 2&3 primaries into two secondaries a little over a foot before the actual turbo. Would I benefit from upping the size of the secondaries to 2" schedule 10?

My quick calculations show that the area of 1.5" pipe is 2.22 in^2, 2" pipe is 3.65 in^s and a single scroll of the HX-52 is 2.67 in^s. My thinking is that reducing the area of the exhaust 50% at the secondaries, just to increase them 20% at the turbo may create weird flow or back pressure/velocity issues. Whereas if I merge them to a 2" pipe, I am reducing the area 18% at the secondaries and then another 26% at the flange. Thoughts?

 

[drxlcarfreak]

No one has any thoughts, or is it just a dumb question that I should already know the answer to? If it helps, this is the layout I am planning on.

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[RWD4G63]

I'd say that the inside diameter of the 1.5" (which is 1.682) is going to be plenty, even merged. You'll want to keep velocity high with that kind of exhaust manifold anyway. If you need to make it larger to meet the T5 flange, I'd do it right before the flange.

 

[drxlcarfreak]

True. Even approaching 90lbs/min you dont think it would become a restriction?

How would I enlarge them just before the ports?

Thanks!

 

[RWD4G63]

True. Even approaching 90lbs/min you dont think it would become a restriction?

How would I enlarge them just before the ports?

Thanks!

I doubt it would become a restriction with the length of the manifold and the A/R you're running.

Transitions could be handled with a cone like this, obviously hammered to shape:

1 5 to 3" Stainless 304 Exhaust Transition or 2" to 3" | eBay

 

[drxlcarfreak]

Good enough for me, I will stick with 1.5" sch. 10.

Cool, I wonder if I can get that in thicker schedule 10 somewhere...

 

[TSITurbo95]

Told you so!

 

[CODE4]

Good enough for me, I will stick with 1.5" sch. 10.

Cool, I wonder if I can get that in thicker schedule 10 somewhere...

1.5 does come in a variety of schedules, most commonly 5, 10, 40, and 80. Not sure how difficult it would be finding something in between. If available the 90s and 45s might be even more difficult.

 

[drxlcarfreak]

Told you so!

Haha, that you did sir.

Code4: Sorry I wasn't very clear. I am already using schedule 10 for the piping and elbows, I was talking about the 1.5" to 3" reducer that RWD4G63 showed me.

Looks like Ace has 2" to 1.5": 2" x 1-1/2" Schedule 10 Concentric Reducer 304L - Schedule 10 - 304L - Concentric Reducers - Butt-Weld Fittings - Ace Stainless Supply

 

[CODE4]

I am sure it exists. I re read what you originally typed and got it now

If you come up blank on finding one, PM me and I should be able to get one via work. I will try and find a price tomorrow.

Just found this while googling:

in 304L: http://www.globalindustrial.com/p/p...10-concentric-reducer-3x1-12-butt-weld-female

in 316L: http://www.globalindustrial.com/p/p...10-concentric-reducer-3x1-12-butt-weld-female

Never ordered from them so I cannot offer any review on their service.

 

[drxlcarfreak]

Cool. Thanks for looking into it. Wow, at $82 a piece I may have to make the 1-1/2 to 2" work!!

 

[LandSpeed-DSM]

In my own experience, backed up by sentiments of several builders including some recent comments on the subject from Shearer on Link (IIRC) - a properly designed "small" runner manifold can compliment a setup, but they are less forgiving with any flaws vs. a larger (>1.5" ID) runner manifold.

I designed mine in Sch40 pipe, ID is close to 1.7" and while my main goal was keeping a stock radiator, the aim was to make it equal length and smooth into the turbine housing.

Another trick, picked up from some of the turbo Pro-Mod folks was to extend the manifold a short distance into the turbine housing, almost like a slip fit and matching the surfaces to each-other as tight as possible. This being a logical step further from regular gasket matching I suppose.

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[99gst_racer]

I designed mine in Sch40 pipe, ID is close to 1.7"

It should be about 1.6" ID, right? 1.9" OD with a .145" wall.

I haven't worked with sch40 yet, but I imagine that header has some serious weight to it.

 

[LandSpeed-DSM]

Ill have to check the schedule chart, but I think you are right about the ID.. OD is visibly bigger than a sch10 unit made for a guy's Honda at about the same time, to similar spec.

This manifold was made ~2 or so years ago at this point, so I may be off on some details. And yes, she is on the chubby side, but so are the turbo/gates/pipes it's supporting The shipping weight when I bought the turbo was like ~60lbs or thereabouts.

We welded 2 flanges together.. One 1/2" the other is something like 5/16 I think and ran the pipe into both, obviously using extended studs, to help spread the load a bit and keep the runner shape I wanted while clearing the front balance shaft hump with that monster turbine housing.

Went into this with the mindset of everything needing to be heavy-duty as this particular application is one that will subject all parts to more stress than most drag cars and certainly more than any street car could reasonably put it's parts through.

 

[RWD4G63]

I'm a firm believer in running the smallest piping that isn't going to be a big restriction. We generally build manifolds using 1.25in schedule 10 piping for guys wanting to run around 650whp, any more than that, and we'll up it to 1.5. The response difference is definitely noticeable.

Referencing the Link thread, Kiggly moved down in piping size (2.25 to 1.625) and up in turbine housing A/R (1.1 to 1.25) and the setup stalls faster and has the same top end.

 

[LandSpeed-DSM]

I'm a firm believer in running the smallest piping that isn't going to be a big restriction. We generally build manifolds using 1.25in schedule 10 piping for guys wanting to run around 650whp, any more than that, and we'll up it to 1.5. The response difference is definitely noticeable.

Referencing the Link thread, Kiggly moved down in piping size (2.25 to 1.625) and up in turbine housing A/R (1.1 to 1.25) and the setup stalls faster and has the same top end.

Kevin also has MIVEC..

 

[CODE4]

Ill have to check the schedule chart, but I think you are right about the ID.. OD is visibly bigger than a sch10 unit made for a guy's Honda at about the same time, to similar spec.

This manifold was made ~2 or so years ago at this point, so I may be off on some details. And yes, she is on the chubby side, but so are the turbo/gates/pipes it's supporting The shipping weight when I bought the turbo was like ~60lbs or thereabouts.

We welded 2 flanges together.. One 1/2" the other is something like 5/16 I think and ran the pipe into both, obviously using extended studs, to help spread the load a bit and keep the runner shape I wanted while clearing the front balance shaft hump with that monster turbine housing.

Went into this with the mindset of everything needing to be heavy-duty as this particular application is one that will subject all parts to more stress than most drag cars and certainly more than any street car could reasonably put it's parts through.

OD will not change on pipe schedules as you change wall thickness. You lose ID as you move up in schedule rating.

On sch 10 1.5" you have a .109" wall vs a .145 wall on sch 40.

 

[LandSpeed-DSM]

Then it looks like I should see if I can find my notes .. mine for sure is sch40 1.5.

 

[RWD4G63]

Kevin also has MIVEC..

Yes? He moved down in piping size and gained response and didn't lose power with the same setup otherwise. It should work the same for a standard DSM engine.

I was using it to illustrate my point that I'd rather have a small manifold and big turbo than a big manifold and small turbo.

 

[tkelly27]

With equal length and twin scroll, you should have a very limited amount of overlap in the pulses, if any at all. The flow requirements shouldn't change a whole lot from primary to secondary. What you could try is SCH 40 for the primaries and SCH 10 for the secondaries. They don't make 1.75" sadly. SCH 10 1 1/4 in the primaries might be a bit too small for a HX52 set up.

If you are planning on making a few iterations of this manifold and testing them sch 10 1 1/4 primaries will be easier to fit, and should be a bit cheaper. If you're only going to do it once, sch 10 1 1/2 all the way is what I would choose. Highly tuned naturally aspirated engines will have size transitions to take advantage of pressure waves, maybe you could make the transition in the primaries

http://www.scrutinizef1.com/wp-content/uploads/2013/01/3-redgrove-exhausts-f1.jpg

I was using it to illustrate my point that I'd rather have a small manifold and big turbo than a big manifold and small turbo.

Yup. The flow losses from the tubes are going to be pretty low compared to the giant turbine in the way of the exhaust.

Here's the list of schedule pipe sizes for anyone wondering

http://www.engineeringtoolbox.com/steel-pipes-dimensions-d_43.html

Is the transition from the head flange to the primaries smaller? Are you considering any anti-reversion?

 

[drxlcarfreak]

Wow, I didn't realize that people were still responding to this, sorry about that!

I found that thread about Kiggly going from 2.25" to 1.625" picked up a good amount of spool. I am pretty set on the primaries sticking to 1.5" schedule 10, already have a bunch sitting in my garage waiting for me to get other projects out of the way. 1.5" schedule 40 sounds like a really rigid manifold!

With equal length and twin scroll, you should have a very limited amount of overlap in the pulses, if any at all. The flow requirements shouldn't change a whole lot from primary to secondary. What you could try is SCH 40 for the primaries and SCH 10 for the secondaries. They don't make 1.75" sadly. SCH 10 1 1/4 in the primaries might be a bit too small for a HX52 set up.

If you are planning on making a few iterations of this manifold and testing them sch 10 1 1/4 primaries will be easier to fit, and should be a bit cheaper. If you're only going to do it once, sch 10 1 1/2 all the way is what I would choose. Highly tuned naturally aspirated engines will have size transitions to take advantage of pressure waves, maybe you could make the transition in the primaries

http://www.scrutinizef1.com/wp-conte...xhausts-f1.jpg

Quote:
Originally Posted by RWD4G63 View Post
I was using it to illustrate my point that I'd rather have a small manifold and big turbo than a big manifold and small turbo.
Yup. The flow losses from the tubes are going to be pretty low compared to the giant turbine in the way of the exhaust.

Here's the list of schedule pipe sizes for anyone wondering

http://www.engineeringtoolbox.com/st...ions-d_43.html

Is the transition from the head flange to the primaries smaller? Are you considering any anti-reversion?

I would like to not have to make multiple manifolds if at all possible. I was trying to find calculations or general sizes for to help take advantage of pressure waves and maximize anti reversion, but in the end I could not find any solid data on the subject so I basically jammed the piping in there as tight as I possibly could to keep everything in its stock location.

As for the head flange to primaries I was planning on using something similar to this to keep fabrication easier, and keep a nice transition: Exhaust Head Flange - Mitsubishi - Mitsubishi 4G63 Exhaust Head Flange

I can't remember the area of the ports, but I think that the 1.5" schedule 10 is just slightly larger than the port area. It was one of the original reasons why I was thinking of going 1-1/2" to 2" to the turbo. Cross sectional area would step up at the primaries, step up at the secondaries and then step back down at the turbo scroll to increase local velocity. Rather than step up at the primaries, step down at the secodaries, and step back up at the turbo scroll. It just seemed like it created two different places for reversion to start and slow the velocity of the exhaust down and increase back pressure.

But sitting back and thinking about what everyone is saying, even at 8500RPMs, opposing cylinders are firing about 140 times a second, which means each scroll will have 0.007 seconds per exhaust event. At 1,000 degree exhaust temperatures, the speed of sound is 1,872 feet per second. By the time cylinder 4 fires, the pulse from cylinder 1 theoretically should be 13 feet away.

 

[RWD4G63]

But sitting back and thinking about what everyone is saying, even at 8500RPMs, opposing cylinders are firing about 140 times a second, which means each scroll will have 0.007 seconds per exhaust event. At 1,000 degree exhaust temperatures, the speed of sound is 1,872 feet per second. By the time cylinder 4 fires, the pulse from cylinder 1 theoretically should be 13 feet away.

That is pretty cool.

Yeah "stepped primaries", or any step in the exhaust manifold, are to broaden the powerband, sometimes it has a nice side effect of reducing reversion, but not always. It creates a secondary pressure wave that can help pull on the exhaust/fresh intake charge depending on your cam setup.

BUT, in a turbo system, the turbo is a big restriction and/or pulse damper, and to me it seems you'd just want to keep velocity high without creating a restriction.

 

[drxlcarfreak]

That is pretty cool.

Yeah "stepped primaries", or any step in the exhaust manifold, are to broaden the powerband, sometimes it has a nice side effect of reducing reversion, but not always. It creates a secondary pressure wave that can help pull on the exhaust/fresh intake charge depending on your cam setup.

BUT, in a turbo system, the turbo is a big restriction and/or pulse damper, and to me it seems you'd just want to keep velocity high without creating a restriction.

I definitely agree here. Sure, a turbo is a restriction/pulse damper, but from what I have learned, for the most part, what makes an all motor engine breathe better works just as well on a turbo car. It is just usually harder to implement due to constants in calculations changing and getting everything packaged in.

 

[swifteagle]

I did a budget manifold for a friend of mine with 2" runners in to a 4" collector with a divided td04 flange.