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Old 06-01-2018, 06:59 AM   #31 (permalink)
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i6 is a nice, balanced design, but fewer and larger cylinders deliver better fuel economy, are less expensive, and probably more reliable too.

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Old 06-01-2018, 12:30 PM   #32 (permalink)
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Here's a quote from a very informative site on engine building. I'm going to build a header for my inline six based on this info.


According to the turbocharger engineers, the most important aspect of designing a good header system for a turbocharged application is to maximize the recovery of exhaust pulse energy. This energy recovery has at least two components. The first is to provide evenly-spaced exhaust pulses to the turbine. To accomplish that, it is helpful first to be working with an engine (or bank of an engine) which has evenly-spaced firing intervals. In an application in which the cylinders feeding a given turbine or turbine section have even spacing, the lengths of the primary tubes should be as close to equal length as possible.

The second component is to maximize the recovery of pulse velocity energy. For that purpose, turbine housings are available in split housing, or "twin-scroll", configurations, in which there is a divider wall in the center of the turbine nozzle housing to separate the incoming flow into two separate streams. That allows the nearly ideal pulse separation of 240 crankshaft degrees to be achieved on an inline-6 engine by grouping the front 3 cylinders into one side of the housing and the rear three cylinders into the other side. The same effect can be achieved on a V6 engine by grouping each bank separately.

Here's where the site is for a good read

Exhaust System Technology: Science and Implementation of High Performance Exhaust Systems
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Old 06-02-2018, 07:52 AM   #33 (permalink)
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(David Vizard was always the best read on exhaust systems. Racing is a world of its own. Removed from daily concerns. A twenty minute WOT grade ascent with a trailer is quite different than the track. Good luck)
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Old 06-02-2018, 10:49 AM   #34 (permalink)
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Turbo efficiency has a little to do with fuel efficiency I would think. The header will lower the rpm for peak torque, making the truck more driveable. Peak torque and peak fe are at the same place on the curve. I was just trying to give praise to a small i6. I'd love to get my hands on one. Apologies for getting off topic.
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Old 06-02-2018, 02:27 PM   #35 (permalink)
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Turbo efficiency definitely affects fe. Especially on a full size truck where you will be in boost a lot, whether you like it or not, just specifically because of the weight of the vehicle.

[Edit]: Back when I had my 2016 civic, I noted noticeably better fe in town if I rolled into 1-2lbs of boost while getting up to speed. Mainly because the car ran 14.7 until 4lbs where it would start to richen up. Benefits of DI.
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Old 06-03-2018, 11:53 AM   #36 (permalink)
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If we're talking turbo header design, Mazda's new 4-3-1 deserves a mention.



And it has flapper valves and dual ports!

Interesting way to bypass the heat problems that hobble VGT use on gasoline engines.
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Old 06-03-2018, 06:30 PM   #37 (permalink)
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And look at that wee intercooler on the EGR! Even smaller than those turbocharged kei-car intercoolers!
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Old 06-04-2018, 12:42 AM   #38 (permalink)
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Quote:
Originally Posted by samwichse View Post
And look at that wee intercooler on the EGR! Even smaller than those turbocharged kei-car intercoolers!
It's a water-cooled EGR system. Diesels have had to use them for the past few years to meet stringent EURO emissions regulations. (together with adblue injection, this adds a lot to the upfront cost of diesel!)

Never seen it on a gasser before, though.
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Old 06-04-2018, 07:35 AM   #39 (permalink)
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Quote:
Originally Posted by niky View Post
It's a water-cooled EGR system. Diesels have had to use them for the past few years to meet stringent EURO emissions regulations. (together with adblue injection, this adds a lot to the upfront cost of diesel!)

Never seen it on a gasser before, though.
More generally, with all the cost of better efficiency gas/diesel engines, it's just one more supporting reason why small cars are going hybrid/electric.
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Old 06-04-2018, 09:57 AM   #40 (permalink)
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Quote:
Originally Posted by niky View Post
It's a water-cooled EGR system. Diesels have had to use them for the past few years to meet stringent EURO emissions regulations. (together with adblue injection, this adds a lot to the upfront cost of diesel!)

Never seen it on a gasser before, though.
Toyota has been using water-cooled EGR for several years on at least the Camry, Prius, and Prius c, probably others I don't know about. Or did you mean on trucks specifically?

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