Engine technology thread.

[serialk11r]

Ah perhaps F1 engines have such high compression that they don't see quite as big gains. At the high rpms they run, cooling loss is pretty small, and they have extreme precision and advanced materials on their side, as well as practially restriction free induction and exhaust, so the advantage is perhaps not as big.

[Dimman]

Originally Posted by serialk11r

Ah perhaps F1 engines have such high compression that they don't see quite as big gains. At the high rpms they run, cooling loss is pretty small, and they have extreme precision and advanced materials on their side, as well as practially restriction free induction and exhaust, so the advantage is perhaps not as big.

7% more 'free' power at their high levels is pretty significant.

Now back to induction...

(SolidWorks is for noobs)



Okay, so there's my lovely diagram. (please ignore the accidental penis shapes, I didn't feel like re-drawing after I noticed...)

Now where was I? What I'm interested in is the merge area and the runner of the closed plenum.

In a similar application of a venturi merge collector in the exhaust, that low pressure area is used to make it easier for the next batch of exhaust gas leaving the connecting runner to exit the cylinder. This is inertial scavenging as opposed to the wave-type scavenging mentioned a few posts up.

The main difference between the exhaust merge collector and my dual runner idea is that at low rpm, the connected runner just stays closed.

What I'm guessing is that this will try to suck some of the upper runner's charge into the runner and cause some unpleasant turbulence. Part of this can be reduced by the way the two transition, flow likely trying to stay attached to the divider, and the fastest portion being kind of in the middle. But this is the part that makes me think of blowing air over the opening of an empty bottle (closed secondary plenum being the bottle). So could the turbulence and the low pressure area create vibrations/resonance that could be harnessed? And if so how?

The way the port flows, the turbulence being mostly on the bottom will not be that big of an issue as more than 50% flows over the 'top' side of the valves normally. So I may get a bit of 'free' low rpm flow because the velocity gains (yay!) will be on the 'good' side of the valve/port and the increased turbulence (boo...) will be on the 'bad' side of the valve/port.

I believe when Toyota/Yamaha did this on the original TVIS 4AGE the runners were side to side each runner aimed at its own valve. To me that doesn't make sense from a low rpm fuel distribution point of view. I would envision more puddling on one side than the other. But they may have been going for low rpm swirl. Still doesn't make that much sense since the angles should be already optimized for tumble at high rpm? Maybe just a packaging issue? (refer to epic diagram for difference between tumble and swirl if you don't already know...)

Next part is acoustic tuning (shudder...). I've got a basic idea of single runner wave tuning. But on this... I'm envisioning 3 reflection conditions.

First, The primary runner. Length, from valve to plenum.
Second, the secondary runner. Length, from valve to it's plenum (could be the same as primary or different).

Working with these two at high rpm, the pulse will leave the valve at the same time and then split down the different runners. Different lengths means the returns occur at different times. This could be used to tune for a flatter torque curve.

Now the next part is what happens at low rpm, with the lower plenum closed? I'm imagining that the two lengths involved would be the standard primary length and the other length I would guess would be from the intake valve to somewhat near the begining of the transition area because of a pressure difference? And/or maybe the entire length as well, once a wave starts bouncing around? Headache time...

Then there is moving things around with a dual VVT-i system... Variable overlap can change how big the time window is to get the waves into the cylinders, plus advancing/retarding can affect which/how much of the waves get used... Ow...

(PS Anyone have an idea what's the cheapest North American *Dual* VVT-i motor I could easily get my hands on? 2AR? Other brand dual cam-phasing motors?)

[serialk11r]

Yes! This extra runner can be tuned to make this work. If the resonance frequency matches the frequency of the primary runner, you'll see low pressure in it at the end of the intake stroke, which then causes air from the primary runner to go into the secondary, and then this air comes back out hopefully at the right time to go into the cylinder. The place you outlined in purple also experiences lower pressure, but the behavior probably needs to be modeled with a wave.

As far as dual VVTi motors go, I don't know which ones are continuously variable and which ones aren't...but a lot of companies have it on their motors now. Hyundai? :O

[Dimman]

Question about intake/exhaust pressure waves. When they change from positive to negative (and the reverse) on terminating against a valve or a volume change, do they lose power? Are they weaker once they change sign?

Also, would a smoother diverging/converging separation like a merge collector create a reflection? Or reduce the intensity of the reflection?

[serialk11r]

I think if the wave hits something "solid" like a valve it doesn't lose energy, as long as the valve wasn't partly opened. If it's at an open end though, yes, just think of a flute; You play a note, it doesn't last forever! When the wave reaches the open end of the flute, most of the momentum in the wave goes into the atmosphere, but not very much makes it back in.

[Dimman]

Inertial stuff is sooo much simpler...

What I'm trying to figure out is whether or not there will be a reflection at the 1-2 transition. Then what happens if they are different lengths and (because they are not synched) when one positive is coming down and a negative is going up, what happens?

Also does diameter have any effect on the waves?

[serialk11r]

I'm not really clear on this stuff, I think the diameter would affect it because we're not just talking about a standing wave, but the air actually has a net movement. Waves don't reflect though, they just "combine" (interference).

[Dimman]

Is this my vertical dual runner idea in the FA20???

[serialk11r]

Dunno dude, I can't tell what those drawings actually depict. Too fuzzy.

Since this thread is hopefully alive again, I am going to say again, I have STRONG feelings this engine will get a major update. 30mpg they say? Ain't gonna cut it when EPA says this is a small car that should get 40 in a test that makes you use the brakes (anyone ever seen the EPA cycle? highway test is definitely not what a typical day of driving looks like, even in traffic). 197hp is also pretty pathetic considering the 2ZZ made like what 189? It doesn't matter that the EPA wants less CO/hydrocarbon whatever emissions, if 197 is correct they don't have much to show for all the effort that went into this engine...

Considering how the phase in of direct injection and legit VVT is not going as fast as originally promised, I think this is just an interim engine that they're sticking into this car so it can be released in 2012, not 2014.

[Allch Chcar]

This was mentioned in the CoG, Weight distribution thread.

Originally Posted by syldrin

just curious but with this vehicle being a direct injected car does that mean lowering the comp ratio will ruin the combustion cycle? i've just heard that direct injection are difficult to change compression ratios on. please clarify. i really want this car but i don't know if i want if i am limited to my power options.

This is not even an issue. Delphi DI engine efficiency look at the picture of pistons for a DI engine at the top of page 4.

The article is largely about Ethanol blends and thermodynamic efficiency but since it uses DI with various compression ratios it is completely relevant. High octane gasoline is only US 91 octane, BTW. Note that the engine is a 2.0L Ecotec with a 86mm square bore x stroke. That is the turbo engine, I believe. I think the N/A Ecotecs are all 2.4L in size.

Any turbo build needs to be compared with doing a swap. EJ207 ftw.

[Dimman]

Originally Posted by serialk11r

Dunno dude, I can't tell what those drawings actually depict. Too fuzzy.

Since this thread is hopefully alive again, I am going to say again, I have STRONG feelings this engine will get a major update. 30mpg they say? Ain't gonna cut it when EPA says this is a small car that should get 40 in a test that makes you use the brakes (anyone ever seen the EPA cycle? highway test is definitely not what a typical day of driving looks like, even in traffic). 197hp is also pretty pathetic considering the 2ZZ made like what 189? It doesn't matter that the EPA wants less CO/hydrocarbon whatever emissions, if 197 is correct they don't have much to show for all the effort that went into this engine...

Considering how the phase in of direct injection and legit VVT is not going as fast as originally promised, I think this is just an interim engine that they're sticking into this car so it can be released in 2012, not 2014.

Not necessarily. Going back to my torque conspiracy theory, it is the torque curve, not the max power that will show off any accomplishments in the motor's development.

The 200PS/197 bhp was probably a design target. Making 200 hp from a 2.0L motor is old news, so it would be up to the engine team to optimize emissions, economy and power delivery.

Imagine if the C&D number of ~170 (I'm going to pick 168) lb-ft @ 4000 rpm is correct. Now imagine that the brochure number of 151 lb-ft (which would be 90% of the peak using 168 lb-ft) @ 6600 rpm is also correct. And the peak power of 197 bhp @ 7000 rpm and the 7400 rpm redline are correct, too.

That would be an outstanding 197 bhp NA performance motor. It would pull from everywhere.

[blur]

So much smart guy talk goin on in here! Love it. Always something to learn.

Anyways, I've been scratching my head over a particular thing. I own an Accord with a J30 in it and have been looking into the J32 swaps. I came across a couple of dyno sheets, and I was wondering, how come they look so much more predictable and ideal than 4 cyl engines? Is it just a matter of displacement?

[serialk11r]

A possibility is larger cylinders makes thermal losses through the water cooling system smaller, and so it varies less across rpms. I wouldn't know though. Perhaps smaller displacement engines are considered too "weak" and thus are more optimized for certain rpm ranges.

[arghx7]

Originally Posted by blur

So much smart guy talk goin on in here! Love it. Always something to learn.

Anyways, I've been scratching my head over a particular thing. I own an Accord with a J30 in it and have been looking into the J32 swaps. I came across a couple of dyno sheets, and I was wondering, how come they look so much more predictable and ideal than 4 cyl engines? Is it just a matter of displacement?

To make it look pretty the smoothing factor is high and the window has been stretched. It's a common trick used by tuners. Go to the Dynojet website and install their free WinPEP7 software. Play around with it and you'll see what I mean. I have a side business tuning cars. Aftermarket performance tuning is on a day-to-day level a completely unregulated industry... there's a lot of Wizard of Oz/smoke and mirrors stuff that goes on.