[RobbyBeefcake87]

Originally Posted by NW-99SS

It's incredibly difficult to build an NA engine that meets current EPA regs for emissions and is 650+ HP.

Yea I'm just kind of going off of the article from the other day saying the zr1 will be TT dohc and the z06 may be the NA version of that engine. I also find it hard to believe they'll do anything over 500 with a small displacement NA dohc motor.

The rumors change pretty often though, maybe the NA version of the dohc TT going on the zr1 will be an option for the base car along side the lt2 and the z06 will be a lesser version of the zr1 TT dohc.

Or maybe it'll be something totally different lol.

[ST1LE]

Originally Posted by RobbyBeefcake87

Yea I'm just kind of going off of the article from the other day saying the zr1 will be TT dohc and the z06 may be the NA version of that engine. I also find it hard to believe they'll do anything over 500 with a small displacement NA dohc motor.

The rumors change pretty often though, maybe the NA version of the dohc TT going on the zr1 will be an option for the base car along side the lt2 and the z06 will be a lesser version of the zr1 TT dohc.

Or maybe it'll be something totally different lol.

LOL, only time will tell but I like where you're going with this. Maybe the GS gets the NA DOHC. Similar power as the LT2, but different power band better suited to track duty.

Who knows, GM has options with these different engines and variants. They can do some interesting stuff, and mid-engine is brand new so screw tradition at this point haha.

[whiteboyblues2001]

Originally Posted by NW-99SS

A proper twin-turbo setup should easily allow one to add boost at low rpm and one to carry it through the high rpm range. Add to that the variable vane technology, I don't see why a DOHV V8 with a TT setup should suffer and lag at all - unless the setup is all about peak HP and not power under the curve.

By "proper" I am guessing you mean sequential. Most TT's are not sequential, they only use two turbos because of the V-shaped configuration and packaging issues.

Also, it is near impossible to not have turbo-lag at all. In order for a turbo to work, you have to have exhaust pressure. Simply closing the throttle (like when you are in a turn) will put exhaust pressure to such low levels, you are not going to be able to produce boost. But that is a good thing because why would you want boost with the throttle closed? But, once you open the throttle, there is a lag to spin up the turbo, and hence, turbo-lag. Currently, they are using turbos that spin up quickly, and then using a waste-gate to ensure there isn't too much boost at higher RPMs and open throttle. This makes turbo-lag hardly noticable under most normal driving conditions, but it's still there, and you WILL feel it when driving spirited or on a road course exiting the turns. AND, you saccrifice power in the upper RPM range due to the way you have to tune the intake runners, cam shaft profile, and other things (like how much undersquare you design the engine with).

The only way I see it so far, is to use an electric boost assist before the turbo spins up. You can do that if you have a 48volt system, so this technology is coming. The electric turbo can run from the 48volt system and keep boost up while in the turn, then the mechanical boost kicks in as you exit the turn and begin to apply throttle. The handoff can be controlled by computer to keep things linear. That way the engine can be tuned for higher RPM power, and then just force the issue with the electric boost when needed.

But, my original question remains. Can someone point out an engine with a super-flat and early torque curve that still produces peak HP higher in the RPM range? I can only find one or the other right now, but I am not too familiar with the exotics.

[NW-99SS]

Originally Posted by RobbyBeefcake87

Yea I'm just kind of going off of the article from the other day saying the zr1 will be TT dohc and the z06 may be the NA version of that engine. I also find it hard to believe they'll do anything over 500 with a small displacement NA dohc motor.

The rumors change pretty often though, maybe the NA version of the dohc TT going on the zr1 will be an option for the base car along side the lt2 and the z06 will be a lesser version of the zr1 TT dohc.

Or maybe it'll be something totally different lol.

My prediction is TT DOHC Blackwing style V8 for Z06. ~750+ HP

Zora will get the hybrid - Electric front wheel assisted to the Z06 TT DOHC V8 for ~900HP. This is be the way GM brings electric into the Corvette world.

I'm happy to be wrong about either predictions, lol!

Originally Posted by whiteboyblues2001

By "proper" I am guessing you mean sequential. Most TT's are not sequential, they only use two turbos because of the V-shaped configuration and packaging issues.

Also, it is near impossible to not have turbo-lag at all. In order for a turbo to work, you have to have exhaust pressure. Simply closing the throttle (like when you are in a turn) will put exhaust pressure to such low levels, you are not going to be able to produce boost. But that is a good thing because why would you want boost with the throttle closed? But, once you open the throttle, there is a lag to spin up the turbo, and hence, turbo-lag. Currently, they are using turbos that spin up quickly, and then using a waste-gate to ensure there isn't too much boost at higher RPMs and open throttle. This makes turbo-lag hardly noticable under most normal driving conditions, but it's still there, and you WILL feel it when driving spirited or on a road course exiting the turns. AND, you saccrifice power in the upper RPM range due to the way you have to tune the intake runners, cam shaft profile, and other things (like how much undersquare you design the engine with).

The only way I see it so far, is to use an electric boost assist before the turbo spins up. You can do that if you have a 48volt system, so this technology is coming. The electric turbo can run from the 48volt system and keep boost up while in the turn, then the mechanical boost kicks in as you exit the turn and begin to apply throttle. The handoff can be controlled by computer to keep things linear. That way the engine can be tuned for higher RPM power, and then just force the issue with the electric boost when needed.

But, my original question remains. Can someone point out an engine with a super-flat and early torque curve that still produces peak HP higher in the RPM range? I can only find one or the other right now, but I am not too familiar with the exotics.

Sequential turbos work well, and BOVs + Wastegates have come a long way in keeping boost pressures between gears. Even easier with a DCT/computer controlled transmission.

[shaffe]

Originally Posted by BlaqWhole

ZL1 trap speed in testing was 125 so that is a 3-4 MPH difference. My trap speed when I ran 11.8 was 121 and change. My fastest trap speed was 122. So for the C8 to do 11.3 at 121 tells me that it hooks something fierce.

I'm not entirely thrilled that GM is going with a DOHC FPC setup. GT350 issues left a bad taste and I doubt I'd be fully comfortable with an engine like that even if it is built by GM. But I do have faith that GM will build it flawlessly considering as how they were building DOHC engines in the 90 ZR1s. Also the size of DOHC engines vs the relatively smaller physical size of the pushrod engines along with the DOHC engines naturally running hotter and having hotter intake temps is not something I desire. I'm wondering why the switch.

Also since GM is going with a DOHC turbo setup for the higher trims, I wonder why they didn't just use some version of the LT4 for the Base and Z51. I mean, they could have detuned it to easily make 550 HP in the standard Vette. That would have given it sub 11 sec quarter mile times and probably put it way ahead of the GT500. Also it isn't an expensive engine. There obviously isn't an issue with size seeing as how they're gonna fit a DOHC with TTs in that same space. And even if they were unable to keep their <$60K price tag I doubt anyone would have complained to have a 550 HP 10 sec Vette with a MSRP around $65K. It still would have been way cheaper than the competition while destroying them. And it would have only been slightly more than a ZL1. I think that would have been nice to see. And they still could have gone with the planned engine for the Zs while keeping it vastly different. The LT2 could have been reserved for trucks and (potentially) the 7th Gen Camaro (if it does show up). I just think that would have been awesome. But there is always the aftermarket.

Speaking of aftermarket, and moving to another topic, lol...I'm thinking that topping the LT2 with a blower will have these cars in the low 10s and high 9s pretty easily with a good tire.

My guess on why they are going DOHC is this. We see the Blackwing as the new hot performance engine from GM. They say Corvette can't have it. My guess, Corvette/GM engineers developed the DOHC architecture and blackwing is one way to go off of it. Corvette will use another, but will share many components and DOHC will be the future of GM performance engines. Why are they going DOHC? If you really want to compete with the exotcis they all have DOHC engines. They scream in the upper RPMs. Not that GM couldn't beat them if they stuck with OHV but if that's the customer you are going after maybe offering something similar to what the competition has is a better play.

Originally Posted by Martinjlm

Ok, this is gonna be my “we had to walk to school in the snow, uphill both ways” story.

The ‘89 - ‘95 ZR1 engine was not a good example of GM doing a DOHC engine. GM owned Lotus at the time. Lotus engineered the engine with some input from GM engineers. Mercury Marine built the engine in one of its facilities in Stillwater, OK. GM’s Corvette engineers treated the engine and the car like a red-haired stepchild. At the time I was leading our Engine Service Engineering group. One of my more interesting tasks was to put together a plan to take the LT5 out of production and maintain service availability for ZR1 owners. My first professional exposure to a full-on fustercluck.

In that 6 years of production, there were (3) groupings of engines. Three different head designs, two crankshafts, and a number of other significant part changes. We had to engineer retrofit kits to allow dealers to repair older (‘89 - ‘91 cars) using newer (‘94 - ‘95) components because a non-trivial number of the original parts suppliers had already gone bankrupt. Dealers had to have a VIN number in order to confirm that they were ordering the correct kit. Parts were expensive. Cylinder head castings cost 4 digits. Yes, I said castings. Getting them machined and assembled cost extra. A lot extra. You don’t wanna know what a crank forging cost. Or how much to machine it.

We bought the last XXX engines off the Stillwater line before Mercury Marine disassembled the line and had them transported to a very secret location. They were (are?) literally stored in what used to be a meat locker. Dealers needed a VIN to order an engine and were subject to a 5-digit core charge if they did not return a core engine after paying 5-digits for a full engine. At the time I referred to the ZR1 as the best car that should have never been built.

Love Martin truth bombs!

Originally Posted by newmoon

My guess is with the 8th Gen they want to compete with the exotics not only in lap times but also for buyers. An exotic buyer is expecting more than a 6500 rpm power band, DOHC will deliver that.

This exactly ^ If all the competition has high reving screaming DOHC turbos and that's the market GM wants to compete in, then it makes sense. Also if they are going to sell it globally places where they are taxed on displacement could be a factor as well.

Originally Posted by Martinjlm

Yup. Exactly that.

What He said ^

Originally Posted by NW-99SS

Correct, only the Caddy variant - Blackwing - is currently in production.

Good info on the LT5 Martin, appreciate that insider take. I definitely didn't realize how costly the LT5 was to GM...that's just crazy.

I'm a big LS and LT fan, but GM had to go DOHC for the reasons already mentioned. The one not mentioned is smaller displacement to meet IMSA Homologation for GTLM racing. I'm certain the next engine is one GM will want to tie together with the C8.R for development.

That is a good point as well.

Originally Posted by NW-99SS

It's incredibly difficult to build an NA engine that meets current EPA regs for emissions and is 650+ HP.

Yep. That's pretty much why the Z06 has an LT4 if the rumors are true. They could make the power but couldn't pass cold start emissions.

Originally Posted by NW-99SS

My prediction is TT DOHC Blackwing style V8 for Z06. ~750+ HP

Zora will get the hybrid - Electric front wheel assisted to the Z06 TT DOHC V8 for ~900HP. This is be the way GM brings electric into the Corvette world.

I'm happy to be wrong about either predictions, lol!



Sequential turbos work well, and BOVs + Wastegates have come a long way in keeping boost pressures between gears. Even easier with a DCT/computer controlled transmission.

This ^ Like I said earlier I think Blackwing will be a cadillac thing but share many similarities with the Corvette DOHC.

And whatever powers them, I would bet the farm that they are both missiles lol. Those high po C8 variants are going to flat out fly

[NW-99SS]

Originally Posted by shaffe

This ^ Like I said earlier I think Blackwing will be a cadillac thing but share many similarities with the Corvette DOHC.

And whatever powers them, I would bet the farm that they are both missiles lol. Those high po C8 variants are going to flat out fly

Yup - same engine family as Blackwing, but obviously different turbo layout as per the CAD drawing already posted. Block and head architecture will be identical, bore, stroke, cam profiles, valve sizing etc will all be optimized for the C8.

[whiteboyblues2001]

Originally Posted by NW-99SS

Yup - same engine family as Blackwing, but obviously different turbo layout as per the CAD drawing already posted. Block and head architecture will be identical, bore, stroke, cam profiles, valve sizing etc will all be optimized for the C8.

The heads will have to be completely different since the Blackwing is reverse flow and the rumored C8 TT engine will be normal flow.

[NW-99SS]

Originally Posted by whiteboyblues2001

The heads will have to be completely different since the Blackwing is reverse flow and the rumored C8 TT engine will be normal flow.

Will wait and see - I don't see GM building two completely different sets of heads for the same engine family (AKA Blackwing Block)...they may have different flow rates, chamber sizes, valve, etc, but the overall architecture will most likely be the same.

[BlaqWhole]

So what can a DOHC engine do that a pushrod engine can't do...besides rev higher? I have not seen any evidence of DOHC engines being superior. To me, some dude raved about "oh man this thing revs soo high" even as he was getting passed by other cars and everyone drank the Koolaid. Look at it like this, ZL1 top speed 202 (198 "officially"), Hellcat top speed 204 (some have hit 205), GT500 limited at 180. Look at the oil drinking problem the Voodoo engines have. BMW DOHC engines are terrible. All these supercars with DOHC engines constantly have enough issues and high maintenance costs that they would suck as a DD. The Mustang GT is faster than the Camaro SS but only after a mile and on a dried up river bed. So where has there been any evidence that DOHC engines are good? Even with the front engine design the Z06, ZR1, Viper, ZL1, etc have been beating much more expensive supercars with DOHC engines. So where is their advantage? They cost more, have more parts that can possible break, have no torque down low, higher maintenance, run hotter, are more prone to heat soak, are physically bigger and therefore are limited on displacement, the list goes on.

I'm not dishing on DOHC engines BTW. I just don't see how anyone can think they offer some advantage. Ok they rev high...so what advantage does that give when they still can't beat well built cars around a track?

[Idaho2018GTPremium]

Originally Posted by BlaqWhole

So what can a DOHC engine do that a pushrod engine can't do...besides rev higher? I have not seen any evidence of DOHC engines being superior. To me, some dude raved about "oh man this thing revs soo high" even as he was getting passed by other cars and everyone drank the Koolaid. Look at it like this, ZL1 top speed 202 (198 "officially"), Hellcat top speed 204 (some have hit 205), GT500 limited at 180. Look at the oil drinking problem the Voodoo engines have. BMW DOHC engines are terrible. All these supercars with DOHC engines constantly have enough issues and high maintenance costs that they would suck as a DD. The Mustang GT is faster than the Camaro SS but only after a mile and on a dried up river bed. So where has there been any evidence that DOHC engines are good? Even with the front engine design the Z06, ZR1, Viper, ZL1, etc have been beating much more expensive supercars with DOHC engines. So where is their advantage? They cost more, have more parts that can possible break, have no torque down low, higher maintenance, run hotter, are more prone to heat soak, are physically bigger and therefore are limited on displacement, the list goes on.

I'm not dishing on DOHC engines BTW. I just don't see how anyone can think they offer some advantage. Ok they rev high...so what advantage does that give when they still can't beat well built cars around a track?

DOHC engines are more efficient than pushrod engines for a given displacement. They make much more power per liter than a pushrod because of the ability to move more air. Look at the Bullitt 5.0. 480 hp out of 5 liters: 96 hp/liter. Voodoo makes 101 hp/ liter. GT makes 92 hp/liter. The latest Corvette engine LT2 makes 79 hp/ liter (490 hp base engine, 79.8 hp/liter from the Z51 495 hp rating). The LT1 is 73 hp/liter. The LT2 is about as good as it'll get from a factory pushrod engine. Pushrod engines have low end torque due to the higher velocity of the intake air and exhaust at slower engine speeds relative to the DOHC engine, but that hampers the ability to breathe at the top end, hence the lower redlines of pushrod engines.

DOHC engines have less moving parts than a pushrod although they are physically larger.
DOHC engines give the ability for variable valve timing. This is one of the more important factors.
DOHC engines can rev higher allowing for more hp (since hp is a factor of torque and rpms)

This short article highlights some of the pros of each type:
https://www.cjponyparts.com/resources/ohv-vs-ohc

[BlaqWhole]

Originally Posted by Idaho2018GTPremium

DOHC engines are more efficient than pushrod engines for a given displacement. They make much more power per liter than a pushrod because of the ability to move more air. Look at the Bullitt 5.0. 480 hp out of 5 liters: 96 hp/liter. Voodoo makes 101 hp/ liter. GT makes 92 hp/liter. The latest Corvette engine LT2 makes 79 hp/ liter (490 hp base engine, 79.8 hp/liter from the Z51 495 hp rating). The LT1 is 73 hp/liter. The LT2 is about as good as it'll get from a factory pushrod engine. Pushrod engines have low end torque due to the higher velocity of the intake air and exhaust at slower engine speeds relative to the DOHC engine, but that hampers the ability to breathe at the top end, hence the lower redlines of pushrod engines.

DOHC engines have less moving parts than a pushrod although they are physically larger.
DOHC engines give the ability for variable valve timing. This is one of the more important factors.
DOHC engines can rev higher allowing for more hp (since hp is a factor of torque and rpms)

This short article highlights some of the pros of each type:
https://www.cjponyparts.com/resources/ohv-vs-ohc

It was a rhetorical question.

I know the differences between the two engines and the benefits of both. I have multiple times on here outlined those benefits. But I'll bite anyway.

While a DOHC setup can make more HP vs a pushrod engine at the same displacement, the drawback of the DOHC engine is it's physical size. Back in the early 2000s there were 2V engines that dwarfed big block pushrod engines by a lot. Therefore what a pushrod engine lacks when it is at the same displacement can more than be made up for due to the fact that you can shove more cubic inches in a smaller space. Even these days. Plus GM was able to build a 454 small block engine only a few years ago. Therefore the HP to displacement ratio is neutralized by the fact that there is only soo much space available in an engine compartment. Plus the fact that you have to rev the hell out of a DOHC engine the more HP it has means that it is not ideal for performance.

As far as moving parts...well 32 valves vs 16 valves. 5 sprockets vs 2 sprockets. 4 cams vs 1 cam. Ok the pushrod has, well, pushrods. But the DOHC has more cam followers. The list goes on. So which engine has less moving parts? Restriction plates. Valve springs. So that wasn't a true statement at all.

Again, you have to rev the hell out of a DOHC engine. Funny thing tho is that the Demon at 840/808 has more HP than anything Ford has made. The Redeye at 797 has more HP than the GT500. And I'd wager that the basic Hellcat makes more HP to the wheels than the GT500 will. So where is this HP advantage?

VVT...nothing but a gimmick.

End of the day the pushrod engines have been outperforming the DOHC engines by a long shot and pretty easily I might add. EVen if you argue that a DOHC engine makes more power up top, which engine makes more power thru most of it's power band? Ok so a Voodoo can rev to 8250. But it's power doesn't come on until sometime after 4K. A pushrod engine makes power from 2K to over 6K. What's the difference? Both engines have the same amount of power available for the same amount of RPMs. Coming out of a turn and nailing it, which is going to accelerate faster? The only way a DOHC engine would be able to keep up is if you kept the engine screaming at the top of it's lungs the entire time. Guess what that does. Drive train strain, engine strain, fuel consumption, oil consumption, excess heat, increased IATs, etc. And it offers no extra acceleration from what I've seen.

Basically there is nothing to prove the superiority of a DOHC engine vs a pushrod engine. Fuel efficiency? Bullshit. Unless you keep it under 2K RPMs and gutless you ain't saving any gas. In fact I bet my 15 GT got worse MPGs than my ZL1 gets. Both engines has it's pros and cons. What the DOHC excels at (HP per cyl) is also where it sucks (limited space = limited displacement). It's pros are the pushrod's cons and the pushrod's pros are the DOHC's cons. And the fact that we are seeing the pushrod engines pushing way more HP safely and more efficiently than DOHC engines is a testament in itself. The 7.0 LS7 in the Z28 made 505 HP vs the 5.2 Voodoo's 526 HP. But which engine vibrated itself apart and drank oil like an alcoholic at an all inclusive? The 3rd Gen Coyote makes slightly more than the current LT1 but which one has been having issues? There is no evidence to prove that a DOHC engine outperforms pushrod engines when the pros of each engine are exploited.

[Martinjlm]

Originally Posted by Idaho2018GTPremium

DOHC engines are more efficient than pushrod engines for a given displacement. They make much more power per liter than a pushrod because of the ability to move more air. Look at the Bullitt 5.0. 480 hp out of 5 liters: 96 hp/liter. Voodoo makes 101 hp/ liter. GT makes 92 hp/liter. The latest Corvette engine LT2 makes 79 hp/ liter (490 hp base engine, 79.8 hp/liter from the Z51 495 hp rating). The LT1 is 73 hp/liter. The LT2 is about as good as it'll get from a factory pushrod engine. Pushrod engines have low end torque due to the higher velocity of the intake air and exhaust at slower engine speeds relative to the DOHC engine, but that hampers the ability to breathe at the top end, hence the lower redlines of pushrod engines.

DOHC engines have less moving parts than a pushrod although they are physically larger.
DOHC engines give the ability for variable valve timing. This is one of the more important factors.
DOHC engines can rev higher allowing for more hp (since hp is a factor of torque and rpms)

This short article highlights some of the pros of each type:
https://www.cjponyparts.com/resources/ohv-vs-ohc

I agree with everything except the bold parts. For similar designs, DOHCs have more moving parts. Four camshafts to one. Chains and chain tensioner for each pair of cams. Typically 4 valves per cylinder as opposed to two or three (depending on the engine and manufacturer).

It should also be noted that many OHV engines, including GM small block engines, have Variable Valve Timing. Actually, I’m hard pressed to think of any modern engine OHV or OHC that does not have VVT.

[whiteboyblues2001]

Originally Posted by NW-99SS

Will wait and see - I don't see GM building two completely different sets of heads for the same engine family (AKA Blackwing Block)...they may have different flow rates, chamber sizes, valve, etc, but the overall architecture will most likely be the same.

They have to be different. The path the intake and exhaust gasses take is switched. And you can't just make the intake the exhaust and the exhaust the intake because the intake valves are bigger. Plus the bore size will be bigger, location of the direct injection will be different, etc. The only thing that will be the same is the size and bolt pattern. And those might be different as well...

[whiteboyblues2001]

Originally Posted by Idaho2018GTPremium

DOHC engines are more efficient than pushrod engines for a given displacement. They make much more power per liter than a pushrod because of the ability to move more air. Look at the Bullitt 5.0. 480 hp out of 5 liters: 96 hp/liter. Voodoo makes 101 hp/ liter. GT makes 92 hp/liter. The latest Corvette engine LT2 makes 79 hp/ liter (490 hp base engine, 79.8 hp/liter from the Z51 495 hp rating). The LT1 is 73 hp/liter. The LT2 is about as good as it'll get from a factory pushrod engine. Pushrod engines have low end torque due to the higher velocity of the intake air and exhaust at slower engine speeds relative to the DOHC engine, but that hampers the ability to breathe at the top end, hence the lower redlines of pushrod engines.

DOHC engines have less moving parts than a pushrod although they are physically larger.
DOHC engines give the ability for variable valve timing. This is one of the more important factors.
DOHC engines can rev higher allowing for more hp (since hp is a factor of torque and rpms)

This short article highlights some of the pros of each type:
https://www.cjponyparts.com/resources/ohv-vs-ohc

HP per liter should not be used on engines of different designs. Let me try to explain:

There are advantages and disadvantages to both the OHV and DOHC. The simplified equation for this is HP = RPM x Tq(at that RPM). The advantage of DOHC is the ability to rev higher, and therby create more torque by increasing RPMs. The disadvantage is it will be physically larger and heavier allowing for less displacement.

The advantage of an OHV engine is it will be smaller and lighter, so you can have more displacment, which makes more HP through more torque. The disadvantage is that it can't rev as high.

Is it a fair comparison to use HP/L at this point? That metric is pretending that each engine is the same displacement, which ARBITRARILLY takes away the OHV advantage, namely, more displacement. Why? OHV getgs more displacment in the real world. To limit the advantage of one engine over the other will give a biased result every time.

That would be like me saying, hey, lets compare HP/RPM. How much HP per RPM does a DOHC engine make as compared to an OHV engine? It will always be less due to the less displacement. That is taking away the advantage of going to DOHC in the first place. It would be a biased result.

In the real world, a DOHC engine can rev higher, so we shouldn't try to compare while limiting the RPMs. Nor should we compare the two by limiting the displacment advantage of the OHV engine. It doen't make sense (unless you are trying to make a bogus argument on purpose).

Let's take it a step further. Say you are a Ford guy and HP/L is your favorite metric. Well, the 2.3L Ecoboost makes 310HP at 2.3L which = 134.8 HP/L. The Coyote makes 460HP at 5.0L which = 92HP/L. According the favorite Ford fanboi metric, you HAVE to buy the Ecoboost engine. AND you want to tell Ford to make an even smaller engine, like 1L and jack the boost to the moon. That would give you close to 300 HP/L. Would you want to drive that engine? HP/L will always tell you that you should lower displacement, add boost if you don't have it, and jack the boost as high as you can when you do have it. That leads to a shitty engine in terms of driving dynamics. It is a completely stupid metric that will lead you to a worse design every time.

Let's look at it another way. How about if we use the metric the way it was intended: compare two engines of the same design. Chevy (and GM) makes mostly DOHC engines. The Mustang used to come with a 3.7L V6 as an option that made 300 HP. At the same time, Chevy made a 3.6L V6 that put out 315 HP (IIRC) at that time (and now makes 335HP with the same 3.6L). Now this is a valid comparison because the two engines are of the same design, so volumetric efficiency is now an applicalbe metric. Turns out Chevy builds a more efficient engine.

HP/L is a crappy metric that teaches us to all drive 2.0L turbo engines rather than N/A V8. AND, the Ford faithfull MISSUSE this metric in a situation that it's not applicable, and then they can give themselves a pat on the back, even though that metric is clearly telling them that Ford should dump the N/A V8, and go with a TT V6 instead. Or better yet, a 4 cylinder turbo. Hey, want to go exotic? Get a one cylinder and add both turbo and supercharging...