Engine technology thread.

[serialk11r]

I'm arguing from a purely philosophical standpoint. "specific torque" means something tangible. "mean effective pressure" means the same thing, but is one step removed and harder to understand. It's also 1 more conversion step. It serves no purpose other than to make things more confusing. Thus it is better to use units of specific torque as they do not need extra translation.

[Dimman]

Originally Posted by Ryephile

Kaizen...I had to look that up That'll be my international vocabulary lesson for today.


Let's look at this engine topic from another angle; what other current production naturally aspirated engines that are sold in the USA [i.e. level emissions playing field] have noteworthy BMEP? I'll omit cars over $100k, as the budget for applying technology is hardly a fair comparison.

Car___________________Engine___Torque____BMEP
Acura TSX_____________144 cuin, 172 LbFt = 180 PSI
Honda Civic SI__________144 cuin, 170 LbFt = 178 PSI
BMW ///M3_____________244 cuin, 295 LbFt = 182 PSI
Corvette Z06___________427 cuin, 470 LbFt = 166 PSI
Ford Mustang GT________302 cuin, 390 LbFt = 195 PSI
Hyundai Genesis R-spec__307 cuin, 376 LbFt = 185 PSI
Infiniti G37 IPL__________225 cuin, 276 LbFt = 185 PSI
Lexus IS350____________210 cuin, 277 LbFt = 199 PSI
Mazda Miata____________122 cuin, 140 LbFt = 173 PSI
MINI Cooper_____________98 cuin, 118 LbFt = 182 PSI
Porsche Cayman R_______207 cuin, 273 LbFt = 199 PSI

FT-86_________________122 cuin, 151 LbFt = 187 PSI

It's right there in 4th place....not crap, just not the best. Just for giggles, it's better than the Lexus LFA's 182 PSI.

Less than the lower-performance 2GRFSE in the IS350.

Less than its spiritual predecessor.

Just friction-wise this motor, by account of its smaller bore/piston circumference, should have less friction than the 2GRFSE from less surface area on the skirts/rings. Then the lighter pistons maybe don't need the same diameter pins, rods, rod bolts or main journals. Friction and inertia benefits there as well. All these little things add up, and will be looked at. Now account for the increased compression (2GRFSE is 11.8:1) and between the increase pressure and decreased friction that should cover a BMEP increase right there. If it's tuned for 4000 rpm vs 4800 rpm in the 2GRFSE, more friction reduction and more BMEP. And the 2GRFSE doesn't even use ACIS to extend its intake tuning range. (However we don't know if this FA20 does either.)

To give an example of how important kaizen is to Toyota, the original slogan for Lexus, 'The relentless pursuit of perfection', is a literal translation of the word.

[Dimman]

Originally Posted by serialk11r

I'm arguing from a purely philosophical standpoint. "specific torque" means something tangible. "mean effective pressure" means the same thing, but is one step removed and harder to understand. It's also 1 more conversion step. It serves no purpose other than to make things more confusing. Thus it is better to use units of specific torque as they do not need extra translation.

The B in BMEP means that is measured in the same way that the torque figures used to derive it are, on an engine brake dyno. BMEP and MEP are not the same.

[Ryephile]

Originally Posted by Dimman

Less than the lower-performance 2GRFSE in the IS350.

Less than its spiritual predecessor.

Apparently the 2GR-FSE is not lower performance.

With all the "benefits" the FA20 has over the 2GR-FSE, there must be unknown negatives dragging down the torque. It could be a sub-optimal intake, strangled exhaust [likely], wimpy cams for fuel economy [probable]. None of this will be figured out until the aftermarket starts seeing how "corked-up" the engine is from the factory.

It's still relevant to say that the engine is based on the Subaru FB20, which means the Kaizen is improving the bore, stroke, and at least cylinder head flow. The results [as far as we know], went from:

148 Hp and 145 LbFt ----> 197 Hp and 151 LbFt

49 Hp and 6 LbFt gain with 10.5:1 to 12.5:1 change in static CR, no change in displacement, and barely revving any higher.

I'd say that's a valid improvement. Sure, it's not as impressive as other/previous efforts, but it's better than them simply throwing in the base FB20 and giving up.

[Dimman]

Originally Posted by Ryephile

Apparently the 2GR-FSE is not lower performance.

With all the "benefits" the FA20 has over the 2GR-FSE, there must be unknown negatives dragging down the torque. It could be a sub-optimal intake, strangled exhaust [likely], wimpy cams for fuel economy [probable]. None of this will be figured out until the aftermarket starts seeing how "corked-up" the engine is from the factory.

It's still relevant to say that the engine is based on the Subaru FB20, which means the Kaizen is improving the bore, stroke, and at least cylinder head flow. The results [as far as we know], went from:

148 Hp and 145 LbFt ----> 197 Hp and 151 LbFt

49 Hp and 6 LbFt gain with 10.5:1 to 12.5:1 change in static CR, no change in displacement, and barely revving any higher.

I'd say that's a valid improvement. Sure, it's not as impressive as other/previous efforts, but it's better than them simply throwing in the base FB20 and giving up.

That still doesn't account for the closeness of the peaks. The variable phasing can eliminate the need for them to be close, like they are on the F20C.

You've mentioned that we don't know the shape of the curve, which is true. I agree that it could have a big flat curve. But I'm firm in my belief that the 151 @ 6600 is one end of a 'range' that will be given to us.

For example: "It makes 90% of peak torque from 3600-6600 rpm."
Or "It makes a minimum of 150 lb-ft from 3600-6600 rpm."

I'm standing by my ~208 psi BMEP for 168 lb-ft peak (151 is 90% of that). I'm not as confident as to where in the rev range, but am leaning now to ~4000-4800 rpm (from my previous 5300) based on what I've learned about inlet speeds.

[serialk11r]

Originally Posted by Dimman

The B in BMEP means that is measured in the same way that the torque figures used to derive it are, on an engine brake dyno. BMEP and MEP are not the same.

Uh that doesn't change anything. I was assuming brake all along.

It is a derived figure from torque and displacement. Because displacement and torque are typically given directly it's better to just use that instead of some contrived pressure figure that doesn't actually mean anything. Again, when I hear "specific torque" in my head that immediately makes sense. When I hear "mean effective pressure" I have to first see that this is a unit of work per rotation of the engine, then work backwards and apply some silly conversion to get torque per unit displacement, all for nothing.

Anyways, you were talking about reduced friction. Again, per unit displacement. The pistons have a smaller circumference but there's also less displacement. The stroke is smaller on the 2GR which is more friction, but the bore is much larger so the piston rings have less friction per unit displacement. With the same stroke, friction (and cooling loss) is greater per unit displacement because the area/volume ratio is higher. So the 2GR actually has an advantage there. Of course the heavier pistons increase friction elsewhere but it can't be directly compared like that.

Also I suspect that inlet speed works a bit differently with a direct injector. I said a long time ago that perhaps D4-S engines don't have variable lift because the highly even distribution of fuel makes it not necessary to achieve satisfactory combustion efficiency. Afterall, the lower the inlet speed, the less pumping loss (granted, it is a relatively small amount of energy in the first place).

[Dimman]

Originally Posted by serialk11r

Uh that doesn't change anything. I was assuming brake all along.

It is a derived figure from torque and displacement. Because displacement and torque are typically given directly it's better to just use that instead of some contrived pressure figure that doesn't actually mean anything.

Anyways, you were talking about reduced friction. Again, per unit displacement. The pistons have a smaller circumference but there's also less displacement. The stroke is smaller on the 2GR which is more friction, but the bore is much larger so the piston rings have less friction per unit displacement.

Think of BMEP as being used for development (the 'why') and the torque as being for the end-user (the 'what'). It gives a better example of what must be done (increase pressure and reduce friction/thermal losses) to get the torque.

The friction was a simple example. Would we be comparing the circumference and piston area to the stroke then? (2GR is 94mm X 83mm)

[serialk11r]

I think for a comparison you'd want to compare the ratio between area over which piston rings slide and volume swept by piston. This is assuming that piston rings have about the same friction per unit "length" around the piston. So the area is proportional to bore*stroke, but the volume is proportional to bore^2*stroke. So it's something like (94/86)^2(83/86) which is about 1.15 says google calculator. But there's a lot of factors that change between going to bigger pistons of course, greater bearing friction being one of them. But less cylinders for the same displacement aka larger cylinders definitely gives lower thermal and frictional loss overall I believe. When you add more cylinders you want greater specific power by making it easier to balance? Running at higher rpm reduces thermal loss but greatly increases bearing friction, although I think bearing friction isn't the main source of friction in an engine.

[Ryephile]

Originally Posted by Dimman

That still doesn't account for the closeness of the peaks. The variable phasing can eliminate the need for them to be close, like they are on the F20C.

It could be as simple as the VE curve for the production components end up with a torque shelf between ~6500 to 7000 RPM. The slope could be gradual enough where they didn't bother trying to make a noticeable peak at a lower RPM. They also could've intentionally mapped the ECU to give the car a progressive feel through most of the RPM band instead of a linear [read: boring] feel.

If its anything like the supercharged application of the 2ZZ-GE in the Lotus Exige S, Lotus really dropped the ball on tuning the inlet cam phasing and left a noticeable amount of torque on the table. None of it is near the peak torque, but the area under the curve changes markedly. MINI did this too with the R53 [W11], where they intentionally backed off the ignition timing at mid RPM at part throttle to create a torque hole. Why both manufacturers did this is both mystifying and seemingly stupid. Nevertheless, it happened, and it took some intelligent investigation by the aftermarket to fill in the OEM's tuning gaps in mapping.

[Dimman]

Originally Posted by Ryephile

It could be as simple as the VE curve for the production components end up with a torque shelf between ~6500 to 7000 RPM. The slope could be gradual enough where they didn't bother trying to make a noticeable peak at a lower RPM. They also could've intentionally mapped the ECU to give the car a progressive feel through most of the RPM band instead of a linear [read: boring] feel.

If its anything like the supercharged application of the 2ZZ-GE in the Lotus Exige S, Lotus really dropped the ball on tuning the inlet cam phasing and left a noticeable amount of torque on the table. None of it is near the peak torque, but the area under the curve changes markedly. MINI did this too with the R53 [W11], where they intentionally backed off the ignition timing at mid RPM at part throttle to create a torque hole. Why both manufacturers did this is both mystifying and seemingly stupid. Nevertheless, it happened, and it took some intelligent investigation by the aftermarket to fill in the OEM's tuning gaps in mapping.

This type of thinking is one of the areas that make me doubt my numbers.

The other is with the emphasis on 'tune-ability' there will probably be a corresponding emphasis on buying 'approved' parts, like how every Scion print ad has a huge disclaimer about warranty voiding from non-approved parts (despite being not exactly legal). Coupled to the talk about reflashing the ECU that has everyone excited makes me think that if the number really is 151 @ 6600, it's deliberate.

But it's hard to judge if a serious engine company would go along with that, and the corresponding hit to their credibility. If they do something like pull way more ignition than they should just so 'tuners' can put it back, and I were back-to-back AMA Superbike champion Yamaha, and had to listen to all these jack-asses crow about how they un-fucked the mighty Yamaha's tuning, I would be pissed beyond words. (but I get pissed easily...)

But I also don't get why everyone is so 'ECU happy' for it to be tuneable in the first place. It's not like a WRX where with your Accessport A) you jack up the boost for 'free' hp, and B) it needs to be retuned for every minor VE-change because it was so close to the edge emissions-wise due to its ancient design. And the A) without the B) is likely a major source of the recent (post Cobb era) reliability issues with the WRX/STI.

What I would do, is boost up the low-end as much as I could (assuming an ECU with some degree of airflow flexibility), because you know 70+% of these tuners are just going for a top-end dyno number. They're going to put on big exhausts, and over-sized headers, that all take way more from the bottom than they give to the top. This would also support my big, low-end theory, but this is getting way too speculative for even me...

[Ryephile]

Originally Posted by Dimman

This type of thinking is one of the areas that make me doubt my numbers...

Indeed. They could be intentionally holding back a little bit so TRD & STI branded parts can show gains and rationalize the asking price. IMO the "credibility hit" you mention isn't really at play. The known BMEP numbers aren't bad, they're the upper end of the average as I showed a few posts ago. It's nothing to tuck your tail about, especially when put in the context of it being a hopped up FB20.

It's true, ECU tuneability on n/a engines isn't as big a deal, as there's less left on the table from the OEM typically. I think most of the ECU tuning fans are likely planning on FI in the future. Of course, ECU tuneability will help the n/a guys that want wild cams, tuned headers and intake manifolds too.

Originally Posted by Dimman

This would also support my big, low-end theory, but this is getting way too speculative for even me...

LOL :happy0180:
Yes, we're just making semi-educated guesses at this point. In two weeks when the car is revealed, we may have more info. After that, we'll have to see how the cards are laid before making a concrete judgement.
.

[Dimman]

Well given we are agreed 100% that I will be either right or wrong, I'm going to be thinking about contingency/taking advantage of the situation.

Ryephile: You mentioned in another thread about Burns' X-design software. I'm familiar with Burns products, but not their software. The question I have is, since a lot of their customers are high-end race teams, do A) they use continuously variable cams in these cars (some I know don't like the C5-R/C6.R and NASCAR, but the ALMS cars I don't know) and B) does the software take that into account.

Reason being is that we can now muck around with overlap on the fly, and that can be used to tune-out reversion flat spots.

Extension question. I've heard that stepped headers help maintain low-end while boosting top-end. I've heard two theories why. One is that the steps sort of replicate a cone and it is better from an inertial velocity/pressure point of view. The other is that the steps act as reversion barriers to pressure waves. Any insight?

[Ryephile]

Originally Posted by Dimman

........The question I have is, since a lot of their customers are high-end race teams, do A) they use continuously variable cams in these cars (some I know don't like the C5-R/C6.R and NASCAR, but the ALMS cars I don't know) and B) does the software take that into account.

Reason being is that we can now muck around with overlap on the fly, and that can be used to tune-out reversion flat spots.

Extension question. I've heard that stepped headers help maintain low-end while boosting top-end. I've heard two theories why. One is that the steps sort of replicate a cone and it is better from an inertial velocity/pressure point of view. The other is that the steps act as reversion barriers to pressure waves. Any insight?

While I have some personal experience with Burns products, nobody beyond Burns' staff has direct access to X-design. As such, they are the only people that can answer the question regarding if they are able to add fudge factor for variable cam phasing and/or lift. To my knowledge, a well designed header has to be designed to specific application [i.e. torque and rpm...and cam angle] to work ideally.

I'd rather not comment on things like stepped primaries and other exotic reversion theories at this point, as I don't have enough research experience to make a qualified statement. I haven't read, seen, or experienced any stepped, coned, or otherwise crazy concepts make a significant change in performance. The most important aspects seem to be the collector volume and primary dimensions.

[Dimman]

Originally Posted by Ryephile

While I have some personal experience with Burns products, nobody beyond Burns' staff has direct access to X-design. As such, they are the only people that can answer the question regarding if they are able to add fudge factor for variable cam phasing and/or lift. To my knowledge, a well designed header has to be designed to specific application [i.e. torque and rpm...and cam angle] to work ideally.

I'd rather not comment on things like stepped primaries and other exotic reversion theories at this point, as I don't have enough research experience to make a qualified statement. I haven't read, seen, or experienced any stepped, coned, or otherwise crazy concepts make a significant change in performance. The most important aspects seem to be the collector volume and primary dimensions.

I've read only that they boost top with little to no negatives on the bottom (same thing with long-primary super-short secondary 4-2-1 venturi-merge collected headers on NASCARs), and seen one dyno result on a 2.0L L4 where they did just that, as well as just seen them applied to Aussie V8 Supercars, F3 and F1 engines.

It's that the explanations for why they do it are different.