Engine technology thread.

[Ryephile]

It's possible Formula 1 are currently using multi-wall tubing in conjunction with merging the exhaust valve ports in the first few inches of the primary tubing, then what appears to be a step another several inches later...however it's possibly a Helmholtz resonator using the multiple-walls as tuning forks. It's also possible that it's a simple step-primary and the delta versus straight diameter primaries nets a marginal gain solely at crazy high RPM [i.e. not relevant for road cars]. Any gain in F1, however, is worth the cost.

For us, it's rather academic and not terribly practical. Having Burns hash out the design with their software is likely going to get us much further than the OEM setup, and further than the usual hack aftermarket offerings.

[Dimman]

Originally Posted by Ryephile

It's possible Formula 1 are currently using multi-wall tubing in conjunction with merging the exhaust valve ports in the first few inches of the primary tubing, then what appears to be a step another several inches later...however it's possibly a Helmholtz resonator using the multiple-walls as tuning forks. It's also possible that it's a simple step-primary and the delta versus straight diameter primaries nets a marginal gain solely at crazy high RPM [i.e. not relevant for road cars]. Any gain in F1, however, is worth the cost.

For us, it's rather academic and not terribly practical. Having Burns hash out the design with their software is likely going to get us much further than the OEM setup, and further than the usual hack aftermarket offerings.

Moar bigger = moar powah!

[ryun84]

Some of you gearheads might appreciate this:

http://www.ft86club.com/forums/showt...7453#post77453

[Dimman]

Ryephile:

I noticed in the Engineering thread that you are an acoustical engineer.

Is it possible for you to explain the acoustical tuning aspect of intake runners/plenums? And possibly the same with the exhaust headers/collectors and their pressure waves?

Relating this to Burns' products, their collectors can sometimes referred to a 'venturi merge collectors'. (depending on whether the end tube stays the same diameter or expands) Looking at them, this makes sense, the runners merge, and smoothly neck down, before the combined tube gradually expands out.



Inertia-wise you can 'see' the venturi, and since the low pressure area is where the runners meet, it makes sense that if they are matched to appropriate firing order, the next runner's exhaust gets the benefit of less pressure in its tube. Like a carb, the first rush of exhaust is the air, and the next connected rush is the 'fuel' and gets a pull from the venturi. And back and forth (2-1) or round and around (3-1, 4-1, etc...).

But what do the high (speed of sound) speed exhaust pressure waves do when they hit the gradual area change of the collector, instead of one where the just end inside a cone? Is it any different?

[Ryephile]

In all honesty, it's much more complicated than simple acoustic tuning like a Helmholtz resonator or reflex port. I also don't practice nearly as much acoustics as I should to keep fresh, so I'm pretty rusty with execution without the crutch of my software programs.

With an intake manifold it's reasonably corollary, as the cylinder suction combined with the transient of the valve timing can create standing waves within the intake port and improve mass air flow [and thus VE]. This is basically why high RPM engines use short intake runners and low RPM engines use long intake runners, to set a resonance at a frequency corresponding to the operational RPM range the engine designers choose. Going further, it's why you see complicated active intake port geometries [BMW did an active intake manifold on one of their V8's, though I can't recall which one off the top of my head].

With exhaust tuning, the acoustics are one aspect, but actual particle exhaustion is critical as well. With a traditional loudspeaker bass-reflex port, the air particles are suspended within the port. This resonance is counter productive to particle flow in engines. Thankfully, the positive displacement nature of engines force the particles out the exhaust pipe. The trick now is to set up a complicated series of resonances between the primary and secondary tunings along with not ruining the particle flow with overly abrupt transitions [i.e. crappy collector, sharp bends, or old school restrictive cats]. To try to answer your question, a poor collector is similar to simply dumping all 4 primaries into free space; you get no benefit of the negative wave pulling the next cylinder wave. A terrible collector will actually inhibit pressure wave complimentary interaction and will likely impact particle flow in practice as a result. A properly merged collector will manage the cross section and perceived volume such that each primary slowly expands [relatively speaking] so it doesn't stall and negate it's intended function as a scavenger. If you can envision intake and exhaust flow as an AC circuit [RPM acoustics] with a DC bias [MAF], you're pretty close to the right headspace.

I hope that comes across how it sounds in my head!

If you haven't read it yet, Burns' explanation is a good abstract.

[Dimman]

Thanks, don't know how I missed that page, but most of my time there is comparing the bend prices.

Best part was this:

For more detail on the specifics of header theory read ‘The Scientific Design of Exhaust and Intake Systems' by Phillip H. Smith’.

Off to the bookstore tomorrow!

[Ryephile]

It's a pretty good book [I have it in my bookcase] and worth getting if nothing more than to be an educated consumer.

[arghx7]

One of the things that really makes intake and exhaust manifolds complicated are variable cam phasers (VVT). Here's a case-in-point, the 2.4L direct injected nonturbo engine on the Hyundai Sonata. This engine has variable cam timing on both intake and exhaust, as well as a variable intake runner system:



As counter-intuitive as it may seem, it actually runs short intake manifold runners at low speed and longer runners only in the mid range. Here is a cam timing map for that engine using isobars:

[Dimman]

Originally Posted by arghx7

One of the things that really makes intake and exhaust manifolds complicated are variable cam phasers (VVT). Here's a case-in-point, the 2.4L direct injected nonturbo engine on the Hyundai Sonata. This engine has variable cam timing on both intake and exhaust, as well as a variable intake runner system:



As counter-intuitive as it may seem, it actually runs short intake manifold runners at low speed and longer runners only in the mid range. Here is a cam timing map for that engine using isobars:

I think a lot of the 'Long runner= low-end power' and 'short runners = top-end' has to do with the fact that they didn't have cam phasing back then.

It likely has to do with which wave reflection they were tuning for.

On a short runner it may be possible to get a positive wave on an early reflection at low rpm, but probably at the expense of corresponding negative wave a little later in the power band. What the cam phasing can do is change when the valves open/close/overlap related to when the good and bad pressure waves come back.

With a longer runner but unable to change cam phasing, maybe to get the low/mid rpm positive wave boost, the later negative reflections will only come back at an rpm higher than the motor runs. So with cam-phasing this can be tuned around now.

Fat power bands are becoming the norm now, which is why I don't believe the brochure torque number is a peak one. An example is the LFA with two stage intake induction. It makes 90% of peak torque from 3700 rpm to probably its redline. (At the minimum a bit past its 8700 rpm power peak.)

[Ryephile]

From The Toyota UK Press release:

Toyota has added its D-4S injection technology to Subaru’s new, horizontally opposed, naturally aspirated 1,998cc four-cylinder boxer engine. This system features separate twin injectors for both direct and port injection, and a high 12.5:1 compression ratio, increasing power and torque across a wide range of engine speeds without sacrificing fuel efficiency and environmental performance.

This four-cylinder “boxer” unit generates 197bhp at 7,000rpm and maximum torque of 205Nm at 6,600rpm, giving engaging performance.

Another confirmation of 197 HP @ 7k RPM and 151 LbFt @ 6600 RPM. Still no word on the rest of the power band.

[Dave-ROR]

Originally Posted by Ryephile

From The Toyota UK Press release:



Another confirmation of 197 HP @ 7k RPM and 151 LbFt @ 6600 RPM. Still no word on the rest of the power band.

Exactly like most of us knew it was going to be

[Levi]

For engine/performance comparision:

Renault Clio RS III Cup

NA 2.0l I4
201 PS @ 7.100 RPM
215 Nm @ 5.400 RPM (engine is not quadrat, it has long stroke, that is why more torque)
Redline @ 7.500 RPM
Curb Weight: 1230 kg
0-100 km/h: 6,9 sec
V-max: 224 km/h
Price: 24.000 €

[serialk11r]

Eh that's almost exactly same, maybe FWD has horrible grip?

[blur]

Originally Posted by serialk11r

Eh that's almost exactly same, maybe FWD has horrible grip?

Or gearing.