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Old 01-10-2020, 03:01 PM   #901
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Duder- that was why I decided on my design (it’s in the recent page of the build thread) mid length 4-2 twin scroll header, 14.75” near equal length +/- .25” to merge, then the intake is right around 11.75 total length with enough room to decrease to 10” or increase to 13”. Looking at Indy car stuff and seeing how most designers have come pretty close to equal volume on either side of the turbo system, and some of the things gathered from people I’ve met through work as well as picking your brain some, I feel like I should see benefits in low-mid-high rpm as well as significant gains in transient response. Basically I’m shooting to get net volume from valve to wheel as close to equal as possible in order to maintain high efficiency of transient response, if that makes any sense.
It does make sense! Good deal man. Having equal pulse timing is key for transient response; as the pulses impinge on the wheel you get a much higher apparent turbine efficiency with those "staccato" hits of energy and momentum transfer. It's not a steady-state phenomenon, in other words. If the flow paths are unequal in length or volume then the exhaust pulses themselves can interfere, lose energy, and diminish the gains. The whole twin-scroll housing concept is based on this but it applies for any radial turbine really. A 3-cylinder engine is perfect for transient pulse tuning without the need for twin-scroll; same exact benefit is seen with twin mono-scroll turbos on an inline six.

The wave reflection stuff is of course key for engine breathing and VE across the entire rev range, cylinder filling, and so on. As far as the turbine is concerned though the pulse effect becomes severely diminished as engine speed increases. So you can optimize your turbine match for good steady state / high flow / high engine speed efficiency but then tune the pre-turbine exhaust system to give good pulse effect at low speeds but also better engine breathing at high speeds. It's fascinating stuff really!
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Old 01-10-2020, 03:09 PM   #902
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Culberro summarized it nicely to me: Those things still matter, but 2 psi of pressure at the back of the intake valve means a whole lot more in a naturally aspirated motor than it does in a turbocharged one that already has 20. The difference is 200% in an NA car, but maybe 10% in a largely similar turbo engine, to grossly generalize for the sake of driving the point across. In DTM you care about getting that little bit of extra powerband and less thermal loading at the cost of packaging and serviceability; that is to say the DTM car gets taken apart every week whereas a street driven 700 hp RS7 with air conditioning, ULEV emissions, the expectation of going for at least 100,000 miles before even having to glance at the turbos and silent operation, uses a much bigger engine with the exhaust manifolds molded into the cylinder head. Its all in the application and its associated restrictions.
All good points; DTM target life is only 6,000 km (~3700 miles). I'd just add that the DTM constructors are now designing engines to last for a full season. The ITR has a complicated formula for determining how many spares can be used per car and per team (because of course they do) but in the design & durability testing phase the target is a full season of engine life, including the turbo. Having said that it's still much shorter than road vehicle engine & turbo life.

Of course you can always strap a bigger turbo onto your Redblock, swap injectors and AMM, make 300hp and be happy, without getting into any of this stuff. It's all about the application, for sure.
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Old 01-10-2020, 03:41 PM   #903
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I'm glad we are getting so far into this stuff. My car is probably the last one on Turbobricks that will need to be taken to that level, but I do like the science.

I just ordered some 1.75" OD aluminum tubing for a test intake runner. I just need to know that I can ovalize the end into the proper size/shape, then I'll start designing the manifold.

I also ordered a bunch of schedule 10 weld els and some straight, so the manifold stuff can start soon.

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Old 01-10-2020, 07:53 PM   #904
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Typical mounted 16v < Horizontally mounted 16v

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Old 01-10-2020, 08:05 PM   #905
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Typical mounted 16v < Horizontally mounted 16v

Tell that to my intake manifold...
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Old 01-10-2020, 08:51 PM   #906
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I want to build some weld-el manifolds soon too, so I'll follow along with interest...
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Old 01-10-2020, 09:25 PM   #907
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Typical mounted 16v < Horizontally mounted 16v

It helps that the head was obviously designed for vert mounting when you look at it closely.

Tyler, as a PS now that homeboy ^ reminded me, I highly recommend you add an oil feed port at the back of the intake cam galley, to extend the life expectancy of your bearing journals
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Old 01-11-2020, 11:28 AM   #908
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It helps that the head was obviously designed for vert mounting when you look at it closely.

Tyler, as a PS now that homeboy ^ reminded me, I highly recommend you add an oil feed port at the back of the intake cam galley, to extend the life expectancy of your bearing journals
Oh really? I haven't heard this.
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Old 01-23-2020, 01:19 PM   #909
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Another very small update. Noah and I started to make the turbo manifold. It's a mild steel flange, 304 schedule 10 pipes, and a cast 304 collector with provisions for two wastegates. I'm cutting and fitting everything at my place, then driving to his to have it tacked, then ultimately welded. I wanted to tack it all with my MIG, but we were having problems when he'd TIG over my MIG tacks. This way it will be 100% TIG, and that's cool, even if it takes a bit longer.

You may be able to tell from the pictures that it won't have equal length runners. I just don't have the skill or patience to figure out how to do that in the space I have. The easiest way is to make it a top mount and have all the runners curving around underneath the collector, but the inner fender, oil filter, and alternator or down there. I decided to just focus on placing the turbo is a useable spot, and obviously pairing cylinders 2+3 and 1+4.

2 and 3 will be fairly similar in length, but 1 and 4 will be the most different from each other. I was thinking that at least making each pair equal length would be better than nothing, but that went out the window when I started fitting things up.

So, here it is. I shudder to ask, but does anyone have any speculations about this?



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Old 01-23-2020, 05:39 PM   #910
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Should be fine. If you were trying to squeeze everything out of that motor you might want to push harder for equal/tuned length runners. But I’d just rock with what you can get.... might be able to get closer than you think if you dropped runners 1-4 just under the flange and came up between 1-2, then had 2-3 go out wide then wrap up and in, but that might lend best to having the turbo facing 90* from where you have it
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Old 01-23-2020, 07:53 PM   #911
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In terms of turbine performance you will still get some pulse effect due to the 1-4 separation from 2-3. It won't be ideal with unequal lengths as the pulses will reach the turbine wheel inducer at irregular intervals, but should still show a benefit vs. a log manifold or 4 into 1 manifold on a single scroll turbine housing. By benefit I mean an improvement in transient response or the time delay between requesting torque with your foot and getting full torque output from the engine.

In terms of wave dynamics and negative wave tuning, your cylinders will all be essentially optimized for different engine speeds, and you'll see variations from cylinder to cylinder in exhaust flow, scavenging, and VE. If you were building a high-strung race engine with individual cylinder trims you could work around this, but I think if you tune it fat & happy you'll just end up with some cylinders running richer than others.
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Old 01-23-2020, 10:48 PM   #912
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Should be fine. If you were trying to squeeze everything out of that motor you might want to push harder for equal/tuned length runners. But I’d just rock with what you can get.... might be able to get closer than you think if you dropped runners 1-4 just under the flange and came up between 1-2, then had 2-3 go out wide then wrap up and in, but that might lend best to having the turbo facing 90* from where you have it
Yeah the ideal way to get longer runners is flipping the collector 90 degrees and doing a top mount, but it's not happening with the number of constraints I have. But like you said, I'm not trying to squeeze everything I can out of this engine.
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Old 01-23-2020, 10:52 PM   #913
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In terms of turbine performance you will still get some pulse effect due to the 1-4 separation from 2-3. It won't be ideal with unequal lengths as the pulses will reach the turbine wheel inducer at irregular intervals, but should still show a benefit vs. a log manifold or 4 into 1 manifold on a single scroll turbine housing. By benefit I mean an improvement in transient response or the time delay between requesting torque with your foot and getting full torque output from the engine.

In terms of wave dynamics and negative wave tuning, your cylinders will all be essentially optimized for different engine speeds, and you'll see variations from cylinder to cylinder in exhaust flow, scavenging, and VE. If you were building a high-strung race engine with individual cylinder trims you could work around this, but I think if you tune it fat & happy you'll just end up with some cylinders running richer than others.
Good to know that I probably won't negate all the benefits of the twin scroll housing. Do you think there's a good reason to try to make #1 longer so it's more closely matched to #4? Would two paired 5" runners and two paired 10" runners be better than four runners that were all quite different? I ask because I may be able to add a big bend in #1, but that particular cylinder would then flow worse than it would as a straight shot.
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Old 01-23-2020, 10:56 PM   #914
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your car might sound like a Saab with those runners being unequal length, but I'm sure you won't mind, being a Saab guy and all
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Old 01-23-2020, 11:00 PM   #915
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your car might sound like a Saab with those runners being unequal length, but I'm sure you won't mind, being a Saab guy and all
Ha, that did actually cross my mind. I doubt it'll sound quite as burbly, though, the SAAB manifold is terrible. If it has a little bit, maybe it'll keep me from looking at SPG classifieds every single day.
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Old 01-23-2020, 11:32 PM   #916
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Ha, that did actually cross my mind. I doubt it'll sound quite as burbly, though, the SAAB manifold is terrible. If it has a little bit, maybe it'll keep me from looking at SPG classifieds every single day.
Orange 99 turbo 2 door hatch or yellow 900 spg vert, be still my heart
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Old 01-24-2020, 09:24 AM   #917
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Couldn't resist showing off my c900 now you're talking about them in this thread lol. I guess I'm lucky that I can scratch the Volvo itch with my roommate's '75 245 ;)
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Old 01-24-2020, 09:52 AM   #918
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Ha, that did actually cross my mind. I doubt it'll sound quite as burbly, though, the SAAB manifold is terrible. If it has a little bit, maybe it'll keep me from looking at SPG classifieds every single day.
My high school SPG with a straight pipe sounded like an old boat, I loved it.
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Old 01-24-2020, 10:40 AM   #919
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Orange 99 turbo 2 door hatch or yellow 900 spg vert, be still my heart
Don't talk about 99s. Every time I hear that number, I die inside a little bit for the FREE 99 I had to pass up. I spent two days swapping the interior between to 99s at a local SAAB shop so I could take the one they didn't want. Then I bought a house with zero land, and had a baby, etc.
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Old 01-24-2020, 10:41 AM   #920
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Orange 99 turbo 2 door hatch or yellow 900 spg vert, be still my heart
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Couldn't resist showing off my c900 now you're talking about them in this thread lol. I guess I'm lucky that I can scratch the Volvo itch with my roommate's '75 245 ;)
That car looks so familiar. Were you on SAAB Central forums back in the day?
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Old 01-24-2020, 10:42 AM   #921
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My high school SPG with a straight pipe sounded like an old boat, I loved it.
Same, dude, same. Only I was a few years out of high school and should have known better.
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Old 01-25-2020, 04:31 PM   #922
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That car looks so familiar. Were you on SAAB Central forums back in the day?
Nope, not actively (and I've only owned this one for 2.5 years). You may have seen me post it on some FB groups, I think I recognized your 142 from a Saab group as well
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Old 01-26-2020, 03:06 PM   #923
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Good to know that I probably won't negate all the benefits of the twin scroll housing. Do you think there's a good reason to try to make #1 longer so it's more closely matched to #4? Would two paired 5" runners and two paired 10" runners be better than four runners that were all quite different? I ask because I may be able to add a big bend in #1, but that particular cylinder would then flow worse than it would as a straight shot.
I think it depends on how different your 1&4 length would be from your 2&3 length. If #1 was close to 2x the length of #3 then the pulses from those cylinders would reach the turbine wheel at approximately the same time, then you'd have a long wait and then #4 and #2 would reach the wheel at the same time as each other. It might give you some sort of "big bang" effect that could be interesting to study.
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Old 01-26-2020, 07:23 PM   #924
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I think it depends on how different your 1&4 length would be from your 2&3 length. If #1 was close to 2x the length of #3 then the pulses from those cylinders would reach the turbine wheel at approximately the same time, then you'd have a long wait and then #4 and #2 would reach the wheel at the same time as each other. It might give you some sort of "big bang" effect that could be interesting to study.
Interesting. I've got all the runners except #1 done now, and I'll probably just make it a straight shot. The bends required to get close to the length of #4 would get pretty wild.
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Old 02-11-2020, 09:34 PM   #925
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Well, the manifold is still in progress, so I started doing some other stuff while I wait for time to bring it back to Noah's.

The old setup had a bit of a cooling problem, and I'm trying to figure out if it was the radiator size. It was a new Northern Radiator with a 2.25" x 16x 15.5" core. The cooling fan was admittedly not powerful enough, but it occasionally ran hot at speeds above 30 or so, which tells me it wasn't just the fan.



If I decide to use the same radiator, I'll notch the front frame rail so I can move it lower and more forward. Then I can fit a full size 14" fan, instead of the slim 14" I had. If I need a bigger core, it'll have to be really wide and short, and I haven't had much luck finding anything. A Scirocco style radiator may fit under the hood, but those are only about 13x22". A little more surface area, but not much.

Anyone have some advice on how to properly size a radiator core?
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