yikes 4000RPM for closed loop? On my car, my closed loop operation ends at like a guesstimate of 40% throttle, and if im doing highway (50-60mph) speeds at 2500rpm im out of closed loop.

Are you saying you think the frs/brz will have that high of compression?

If they are looking to getting ~200hp out of a 2.0l NA i4 then I would think the compression has to be at least 12:1. Which is what worries me about trying to run FI on this engine without some serious internals workup... I wish I would have boosted my 97 acura 2.2cl... compression ratio of 9.2:1, would have been boost city!

The direct injection should make this less of a problem. First because I don't think the compression will need to be that high, and second because DI allows a lot higher compression. Audi's 2.0T has 11.1 compression. Also Mazda has new DI engines coming out soon that run 13:1 compression on regular gas.

So with premium fuel, and 12:1(or lower) compression we should still be able to see at least 8psi of boost.

the ferrari 458 runs 12.5:1 CR. i honestly dont think they will go above that. yes the mazda skyactiv uses 13:1 (US cars) and 14:1 (world) CR but the engine also makes 150 hp. its an economy car tuned engine.

fixed

Haha, thx, can you tell I'm anti-subaru?

Correction... if you wanna go w I, V, W and so on, gotta use H :thumbsup:

Well my numbers are from the Honda Fit! :P Are you talking about your gas guzzling Rotary?

Ichi, are you familiar with the EJ204? That would be a good starting point for where the new engine is going to be. I've heard it has 190PS at 7800 RPM, with around 10:1 compression :iono:. And it's 10+ years old. I believe it was available on the Legacy GT. But I have only read wiki articles on it and read rumors about it since it was never released in the US.

12:1 seems high. the civic si has 11:1 and it has 200ish hp. just seems a little high.

12:1 would be great, since the K20 with 11:1 can get 200hp at like 7000 rpm? 12:1 plus direct injection would mean they can get more than 200 at 7000rpm, or 200hp with better fuel economy. Well, all else being equal.

Does the Mazda Skyactiv engine use decreased intake duration? I am fairly sure you can't do 14:1 without a charge density reduction. They say they use long tuned exhaust headers, combustion cavity in the pistons, but that's clearly not the whole story as there are plenty of tuned exhaust systems and everyone has shaped pistons. In the ideal cycle you have no residual exhaust gas, and I'm fairly sure you can still hit the autoignition temperature with 14:1 compression ratio.

k20z3 redlines stock at 8250 and make its peak power more like 8000.

Sorry about that wrong detail then.

I just came across something...rather crazy. This is like the Ferrari VVT system (I think? I read this somewhere, it's a continuous cam lobe that has short duration on one side, long on the other, the whole camshaft shifts)...Helical camshaft O_O

If the Ferrari continuously variable duration cam lobe were modified to have extremely long duration, it would work exactly the same way except of course needing to shift the entire camshaft. This IS the ideal valve actuation system...holy shit. Ferrari just needs to extend the maximum duration and use late intake valve closure. With a direct injection system like D4-S, charge mixing can be overcome.

Has anyone seen articles talking about auto manufacturers experimenting with a mechanical continuously variable duration system?

Yes, EJ204 was NA w AVCS pushing 190hp. That thing was nice... except ECU IS A BITCH! One wrong tuning and this thing gonna bitch worse than some of you guy's wives. :bellyroll: Don't get me wrong, engine itself is awesome. Some Legacy owner felt it was weak (not enough tq in the low end)... but what do you expect from +-1,600kg (+-3,500lbs) AWD drivetrain car? Of course it's gonna feel weak pushing that fat car around. :)

If they put it in Dex, Trezia and all those subcompact cars, the review on this engine would of been different

Sooooo people seemed to either have missed my post or don't know what I'm talking about.
3d profile cams like Ferrari...with a greater range of duration change, Ferrari could implement late intake valve closure. Or we could use a system like the "Williams Helical Camshaft" which is basically like the Ferrari cam except instead of the whole shaft moving one piece stays fixed and the "helical" part moves around it to vary timing. The problem with non variable lift in the second example is poorer low end performance, but something tells me a system like D4S would help. I don't know which one is easier to implement, variable finger follower pivot => early intake closure or this, seems like the first. The improvement would not be that much greater than say Valvematic or Valvetronic or VVEL, but combined with one of those systems it could be highly effective, though probably too complicated. Discuss?

Not gonna see that tech debut in a $20k sports car. Valvematic maybe, and it's about damned time they put it in something worth a damn and send it over to this side of the world.

Yea def, it's a lot cheaper to add a simple pivoting shaft with followers than to have a difficult to machine cam lobe that varies across its length, and still provides most of the benefit for a street car, which won't be revving past 8k in general. But it's an interesting thing, and if some manufacturer decided to put it on lower end cars it could become cheaper, while it is currently limited to just Ferrari afaik.

Valvematic is so simple that it's something we can realistically expect to see on possibly all production Toyota engines in the very near future...if they want to. BMW did it with Valvetronic across the line, and it's helping a ton with fuel consumption despite high frictional loss. The BMW N55 for example as I mentioned before gets the same fuel economy as the naturally aspirated engine, although their exhaust system is designed to capture the exhaust gas "pulse" energy better than your typical turbo, so much that despite the turbine and compressor losses and heat rejection at the intercooler AND lower compression ratio, it manages to get the same economy. Toyota will have to do the same (and bring direct injection to more models) if it's going to retain its fuel efficiency crown.

D-4S vs. a VTEC-like System
 

I was going to start a separate thread, but . . . .

Given the gains, is D-4S worth it? It seems complicated to me relative to a system like VTEC.

In other words, if you could get 200 hp with either, would you prefer D-4S or a Toyota version of VTEC (VVT-i is it?)?



:happy0180:

Toyota's version is VVTL-i
Which was Variable Valve Timing and Lift (I forget what the "I" stands for")
As far as I know, it was only on the 2ZZ-GE in the last generation Celicas and a few other cars. While it was fun, it had it's issues. Namely broken lift bolts on the earlier engines.

I'd be all for seeing lift make a come back. Is there any reason why they wouldn't be able to integrate both D-4S and Lift into the same engine?

D4s is for fuel
Vtec/vvti is for camshafts.

They have nothing to do with each other. And you can use both simuntainiously

I stands for "intelligent" i believe


2 different systems like already mentioned

This thing will have some sort of lift tech I would imagine and having ds4 is gonna be either awesome or a nightmare or tuners since its pretty new tech

Using both is the opposite direction I want to go in. I want a solution that would simplify the design of the head, not complicate it.


Honda's VTEC may not be perfect, but they have had zero recorded failures of the VTEC system — a system that has been used in over a million cars. I would hope that reliability would be built into this car that we are already in love with. D-4S sounds like a recipe for all kinds of problems. Maybe is won't turn out that way, but that's how it look on paper.

so you want to go back to carburators and distributers?

I see nothing to be afraid of. The big aftermarket companies will be all over this car so tuning won't really be that big of a problem.

Again, you peeps are not reading what I am saying.



I am not interested in tuning.

I am not interested in HP (sacrilege, I know :bellyroll: ).

I am not interested in fancy, complicated b.s.

I am interested in relability. And, crazy as it may sound, I believe that simplicity, rather than complexity, is a step towards reliability.

I don't want to go back to carburetors, nor do I want to go back to the horse and buggy. My statement above was that, if you could get the same 200 hp from both, which system would make more sense and make you happiest.



@ Mata: The question imbedded inside my question is: Is this D-4S worth a damn, or will it be like Porsche (drive it every week and fix it every weekend)?

^ I think you seem to be forgetting that D4-S is coming from the world leader in car reliabiliy.

Not only that, D4-S combines Direct and Port injection, so you won't have the carbon buildup problem on the intake valves like purely Direct Injection engines have.

You said it yourself - Honda have had NO reported problems with it's VTEC system, and that goes to show that car's are getting more and more reliable as time goes on (as you'd expect - power, fuel consumption, reliability and saftey will all increase with technology). Chances are Toyota (or any high-volum manufacturer) wouldn't add these sorts of things if they knew/expected them to decrease the reliability.

Wrong, dead wrong. VVT like vtec/vvti, all of it, is for MPG/Emissions/low end torque whatever you want to call it. You don't need 4 cams in a DOHC to make high end power either but you do need it if you want good high end HP and the benefits of a low end torque band.

In most cases the high volume brands keep their systems pretty simple to keep costs down and maintain reliability. Direct injection is already used reliably on Diesel engines. It's all in the implementation.

I get you. But to make 100PS per Liter and still have a bottom end, it's going to need VVT and Direct Injection.

This car is going to be DD or street driven more than anything so I would bet against the Porsche example. We'll have to see really. This isn't the first D4S engine though.

Anyone have hands-on/detailed info on how VVT-i operates? I'm looking at ways to install a VVT-i IS300 2JZGE head on a 1JZGTE bottom as cheaply as possible.

My understanding on the VVT-i motors is there is an ECU-controlled electronic valve that varies oil-pressure to the VVT-i pulley and the pressure corresponds to a certain amount of advance/retard on the intake valve.

Options are:

1:) $3300 for an installed Haltech standalone and then tuning on top of that.

2:) Removing the VVT-i and modifying a cam pulley to fit the different cam, disabling VVT-i until $3300 is acquired.

3:) Installing an oil-pressure regulator and valve so that the pulley will remained in a fixed position. Side benefit is that intake cam timing could be tuned while the engine is running, but still wouldn't have the full VVT-i benefit, until $3300 is acquired.

(This is for my old JDM car that I sold back to my buddy. We still want to do the last-gen VVT-i JZ head experiment...)

Thoughts?

Are you sure VVT-i has continuous phasing? Oil pressure switched is a strong indication it's either "on" or "off". I'm pretty sure I read VVT-i is stepped, it has 2 fixed profiles.

Option 1 !

VVT-i is continuous. The valve is an electronically controlled pressure regulator, not just a switch. That's the 'i' (intelligent) part of the system.

Erm, get a VVT-i computer from a late model JDM 1JZ single turbo.

Don't really want to hunt for an ECU, and then go stand-alone a little later. If I can do something with a manual pressure control valve for less that $20, I will be happy enough, until the Haltech goes in.

Continuing with the idea I presented a while ago about a turbine generator directly connected to the crankshaft, I discovered this has been done on aircraft before, it's called turbo compounding, and exists on some diesel trucks...and I dug up some info.

Deere claims 20% increase in power (for free obviously, intake, combustion, expansion are not affected!) on a diesel engine. They used variable geometry turbo and electrical coupling, but Scania has a mechanically coupled one with fluid coupling (to partially isolate turbine from the crankshaft). Now let's examine the Detroid DD15 that has this system...

18.4:1 compression ratio, but max power at under 2000 rpm. Diesel engines injecting fuel as the piston moves reduces the effective compression a bit more than a gasoline engine, but at low speed this effect is less pronounced. Before anyone gets confused, my goal is to approximate the residual pressure at the bottom of the compression stroke. More precisely, finding a very loose lower bound, because these diesel engines are turbocharged already and have even lower exhaust pressure available for recovery. Let's say a comparable gasoline engine would have 17:1 compression ratio at its own power peak (by CR, I am more concerned with the expansion part of this, not the compression part...because gas engines have much higher speeds, the effect of the rate of combustion being relatively slower at high speed is much greater). Now diesel fuel has more specific heat of combustion than gasoline, so the residual pressure in a diesel of the same effective compression is higher. However at a say, 17:1 CR, you would have more than 10% less residual pressure than at say 12:1, so it's safe to say a diesel engine has no more residual pressure than a typical gas engine. But I think we all knew that? Anyways...

Let's assume turbocharging is more power increasing oriented and doesn't do much in the way of collecting exhaust energy (which is what it is most of the time). Now some of these turbo compounding engine building companies are claiming a 20% increase in power just by sticking a turbine into the exhaust...imagine what happens with a gasoline engine.

Reality check: Instead of running say 7psi boost, we just put all that power back into the engine. This means for each liter of air aspirated we get 50J. In a 2L engine running at 8000 rpm, this is 8000L/min (for every 2 revolutions of the crankshaft we get 1 full cycle), or 400kJ/min = 6.7kW, about 10 horsepower.

You might say, this power isn't actually there because there is exhaust backpressure. The thing is that turbochargers typically found on cars are designed to create backpressure! This way they can provide more power to the compressor, at the cost of taking away more power from the engine. In addition, a higher pressure ratio increases the efficiency of the turbine, of course at the cost of extra work the engine has to provide. A portion of the energy does however come from the velocity of the exhaust as the gases speed up coming out of the exhaust valves. A turbine can be designed to create almost no backpressure and instead rely on just the momentum of the exhaust. With a piston engine, the exhaust comes in "pulses", which can be exploited, so theoretically we could have the exhaust designed so that these waves hit turbine blades at the optimal time.

Side comment: turbos in normal cars usually do very little for efficiency alone because all of the energy from the turbine necessarily goes to the compressor, which does not directly do useful work.
Okay anyways, you might also be saying, isn't 10hp not very much? You have to remember, the compressor is only at most 70% efficient, and intercooling removes a great portion of the remaining energy, so in fact a LOT more energy went into this 7psi than I just calculated. At full throttle, a naturally aspirated engine's cylinders are at signficant pressure when the exhaust valves open. In this paper http://www.hcs.harvard.edu/~jus/0303/kuo.pdf, if you look at the graph at the very end, it looks like in their particular example it was about 300kPa, although that engine had relatively low compression ratio. At higher speed, there is less thermal loss though, so 200kPa over atmospheric is not too bad of an assumption. 200kPa means we can theoretically get 30 horsepower out of the exhaust, when the engine is only producing perhaps 210 horsepower in the first place!

Realistically you might say, this is stupid, all this trouble for 30hp? However I think the real benefit is that if the exhaust turbine is sized to produce more power than the compressor consumes, we can actually increase efficiency at all operating conditions, and this would have very predictable behavior due to being coupled to the crankshaft. In addition, this would require no tuning whatsoever. We could add a supercharger to this, to make it like a lag-less, more efficient turbocharger, but if we pick a supercharger that uses less power than the turbo produces, we can see more horsepower for the same amount of boost. Why is this important again? Well we can run a high compression engine on just 4psi boost, and route the extra exhaust energy into the crankshaft. In addition, the supercharger and turbine being separate units would make piping more flexible, and zero lag makes it very suitable for all performance applications.

Just to play around a little bit, we can make 4psi boost with just 10hp from the crankshaft (I'll skip the calculations). If we intercool, this 4psi represents more than just a 28% increase in air density though, so we can most likely get more than 10hp more from the exhaust turbine as well to due a higher pressure ratio. Remember theoretically we can get 30hp out of the exhaust without the boost, now there is perhaps up to 45hp in the exhaust, which say, we can recover 25hp of (a fairly reasonable number...). Then we have a 15hp improvement over just a turbocharger throwing that 15hp away, which is pretty good, considering you get this gain for free in terms of fuel, and without much weight penalty over just a turbo (possibly saving weight due to less piping?)

The main idea is that with just a turbo we are only manipulating gas pressure at intake and exhaust, but not changing what is attached to the crankshaft. There is always more energy in the exhaust than we could possibly use to pump air back into the intake, so we can just route this straight into the crankshaft for useful work! The reason it hasn't been done is because it's more complex and expensive than a single turbocharger unit, and matching turbine speed to the engine might be a little tricky perhaps needing a CVT, although I doubt it would need that. Another possible advantage is since the turbine reduces the energy in the exhaust significantly, a better flowing exhaust muffler can be used, another direct efficiency improvement.

Something to note is this doesn't do very much for part load efficiency, we still need manufacturers to give us those better intake valve control systems! But for people who track their cars, this would give a pretty large fuel consumption decrease, especially people running superchargers.

Sorry this is really long, I'm pretty bored today since I'm procrastinating on homework lol.

EDIT: Oh and I forgot to mention, someone has done this with a Mazda 13b adapted for use on an airplane I think.

Okay after a bit of research and thinking I think this is definitely possible. A turbocharger not attached to the engine usually would run at higher speeds, but mechanically linking it to the engine would change up things a bit. Ideally we'd want CVT connecting the 2, but I believe a 2 speed gearbox is probably good enough to get near peak efficiency most of the time.

A single speed link would probably be okay though. Garrett's compressor maps seem to indicate 200k rpm as the maximum allowable speed. Of course having the turbine spin at close to maximum speed isn't best because losses tend to be the greatest, but a chart I found on the BorgWarner website seemed to indicate peak efficiency at around 160k rpm, slightly lower at 180k, and climbing up consistently from lower speeds. That said, the 80k curve was still in a pretty healthy zone, within 20% of maximum efficiency, but if we extrapolate a bit we can see that the efficiency drops off quite a bit at lower speeds. This is probably why turbo-compounding has appeared in diesel engines first: they have only a small rev range to worry about, so the turbine doesn't need to operate at inefficient conditions.

If our engine has a 8000 rpm redline though, things seem rather inconvenient. With 200000rpm maximum turbine speed, we want a 25:1 gear ratio to make full use of the "useful" operating range of the turbine. At say 750rpm idle though, this is a pathetic 18000 rpm at which the turbine does barely any work, and at 2000 rpm, we are only at 50000rpm at the turbine, at which it can only achieve perhaps 50% of max efficiency. Certainly with higher gear ratios for fuel economy, if we are running 2500rpm on the highway, our turbine does not operate very efficiently. However while cruising and idle, there isn't as much exhaust either, and the pressure ratio across the turbine would be close to 1 anyways. So that brings us to acceleration. But when we get over 3000rpm the turbine can do pretty well. So for city driving, we probably want something more like a 35:1 ratio to make the turbine useful from 2000-4000rpm. But then again, you can stick to one ratio and rev a bit higher in each gear.

As far as turbo sizing goes, the Garrett website does some approximate calculations with a 2L engine that is supposed to make about 400hp. It would need about 24psi boost to do this at 8000 rpm (not intercooled though I think, but just using this for quick computations). In my previous post I used the fact that there is perhaps more than 3atm absolute pressure left in the cylinder when naturally aspirated. Let's say there's about 30% of the energy in the pressure difference that can be captured. (so use 0.75atm gauge pressure to calculate). This is about 15hp from what I said previously, so we want the turbine from a turbo with compressor that uses 15hp under peak power conditions, which would be a turbo that you'd use to generate about 7psi boost. These calculations are super super super rough, but that gives you sorta an idea of the difference between sizing of the turbines between just a turbocharger and a turbo-compound (with supercharger or not). With say 5psi boost we will have something like 30% more exhaust pressure as well, so the turbine should be from a turbo that makes about 10psi boost, and so on. However you'd want to use a smaller aspect ratio turbine housing since you're not using as much air.

Oh and the more boost you add the more useless this turbine will be at part load, of course. On a racing car though this would provide pretty significant benefit in power.

Another side note: I am honestly not too sure if manufacturers would ever consider this as an efficiency increasing measure, when it's possible to add displacement and use late intake valve closure instead, although late intake valve closure is a bit tricky to do valve timing output control with. Of course more displacement has its own issues too...I guess if it came down to cost, 25% more displacement is cheaper to do than a turbo compound setup most likely, but then with more displacement you'd run into the issue of possibly overexpanding the exhaust at part load. Dunno...

I was just reading about that a few weeks ago. Have you seen this?
http://www.rotaryeng.net/why-tc.txt

The problem with turbocompounding a production car is that the turbine won't do jack squat at low engine loads. It needs a lot of pressure, which is only produced when you're letting lots of air/fuel into the cylinders. Look at the places turbocompounding has been applied commercially, aviation and big marine engines are both operated a near full throttle at all times.

Now, putting one on a race car does make sense, especially if you're running in a displacement, restrictor or fuel limited series. If you're only allowed a 2L engine or say, a ~26mm restrictor, free horsepower is a big deal. And if you're in an endurance race, reduction in SFC at WOT is also a big deal.

As for your mention of lag, there won't be any. Once you couple a turbocharger to the crankshaft you have a centrifugal supercharger and the power band that goes with it. On the plus side, you won't have to worry about wastegates.

Wait I did say there was no lag...
So IMO the use for this on a race car is 1. no lag 2. get the most out of what boost you can run, aka get more horsepower without needing to upgrade internals. Point 2 is kinda why anyone would possibly think of doing it to a street car. With a street car I believe you can argue a turbo is equally useless, why not just a supercharger? Good low end torque, poor fuel consumption only when you're really on it (and as I pointed out a turbo doesn't actually save that much energy).

I must have misread.

Perhaps we have different definitions of the term "race car". If you're talking about somebody's modified production car that is no longer street driven, turbocompounding is a very poor investment. The development of such a system will cost a lot more than a set of forged pistons, and probably a set of rods as well. And since you're talking about running a supercharger anyway, it's much, much cheaper/easier to make up the extra power the old fashioned way.

Actual race cars (ie, cars that are raced against other cars under a common set of rules with tech inspections to make sure that everyone is being honest) are limited in the amount of power they can produce so that the racing stays close and exciting (and relatively safe). This is usually done with some combination of intake restrictors, fuel capacity, displacement limits, and boost limits where forced induction is even allowed. This is where turbocompounding actually makes sense.

Take FIA Formula 3 for example. All F3 cars must be fitted with a 26mm intake restrictor, which means that no car has more than ~215 HP regardless of how huge the team's budget is, the laws of physics prevent it. Recovering 15 hp of waste power from the exhaust gasses means that you could show up on the grid with 230 and have a big advantage. Of course, that's not to say that the rules for any given series don't disallow it (either specifically or on a technicality like F1's rule against variable geometry exhausts), or that it wouldn't cause a rules change for the next season or even the next race. But advantages in racing are hard to come by.

Because apples are better than oranges, duh. :)

You can believe anything you want, doesn't make it reality.
See religion. :happyanim:

Sure, currently it's not easy to develop such a system because large capacity aftermarket turbochargers exist at relatively low cost, but there's nothing stopping it from being financially feasible! Essentially all that needs to be done is rethink the way the turbine is sized compared to the compressor, along with housings, and attach a gearbox to the turbo shaft and then couple that to the engine via a belt or chain. Maybe in the future automakers will turn to this sort of idea to improve volumetric efficiency, and we'll have plenty of standalone power turbines sitting in cars for this purpose :)

@above post: I believe meant "you can definitely". With a turbo the only "extra" energy you can get is from the velocity of the exhaust gas, except a single stage turbine doesn't collect very much of this impulse. The efficiency advantage of a turbo comes at higher boost levels and higher altitude, where the difference between cylinder pressure at exhaust valve opening and atmospheric is greater. In addition using a blow off valve is probably worse than the bypass valves built into superchargers as far as efficiency is concerned. I have to say, madfast's turbo complaints got me thinking about the actual advantage of a turbo, and they are slightly more efficiency under some conditions, better for high boost, and easy to create peaky power down low.

You can definitely...what? Were you referring to my "above" post? Or greg's?