Porsche 904

"JR1" (type35bugatti) 09/13/2014 at 11:28 • Filed to: Porsche 904, Porsche madness

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We live in arguably one of the greatest eras for cars. That being said this era does not have the looks of the 1960s

GhostZ > JR1 09/13/2014 at 11:33

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They said the exact same thing around 2005-2008, which was another era of surprising free car design, as complex aero, high-level computers and hydroforming really kicked off in manufacturing.

And honestly, had we not gotten thrown into the speed war and HP dropped after 2008 or so, we would probably still be looking back at the mid-2000s as the peak.

I'm still on the fence about the 2010s. I feel that every advancement in technology is set back by a tightening of regulations, which wasn't necessarily true back then.

Crest > JR1 09/13/2014 at 11:35

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At least we have variety and stupid crazy designs, thanks to 3D printing and aliens; but back then, almost everything looked the same. That body style for example is just a variation of the Ford GT40, Daytona coupe, Ferrari Dino and so many others. I'm not arguing which came first I'm just saying its not a revolutionary design. This day and age, think of the big 3 Jennifer, Lawe'renotthatgood, and the 9something something and you'll get my point.

StingrayJake > JR1 09/13/2014 at 11:38

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The 60s were fantastic.

Ferrari, Lambo, Porsche, Corvette, Shelby Cobra and Ford GT (which were really just Brits A/C and Lola in disguise).

Awesome stuff

Sweet Trav > GhostZ 09/13/2014 at 11:39

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I think, once the aftermarket kicks in we're going to see a ludicrous amount of horespower and performance from extremely pedestrian cars. It seems everything has a turbo these days, and if the Buick Grand National taught us anything, there IS a replacement for displacement and that is boost.

I cant wait to see a 400hp Chevy Sonic with O-ringed heads and block, ARP studs and 30psi shoved down its bores.

StingrayJake > GhostZ 09/13/2014 at 11:41

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I feel like we're seeing a repeat of the 70s and 80s with the increase in regulations, I just think engineers are handling it better this time around. They're learning the benefits of hybrid tech.

Bad Idea Hat > StingrayJake 09/13/2014 at 11:43

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We're going to look back and wonder why we didn't always have so much torque so much instantly.

GhostZ > Sweet Trav 09/13/2014 at 11:48

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I actually highly doubt it. Unlike the age of the 80s and 90s, most modern turbo cars have much smaller and thinner blocks despite their displacements and are not over-engineered anymore. Not all 2.0l engines were made equal. Then there's engine mounts and transmissions to take into account, which limit the capabilities of engine swaps much more now that overlap and other front crash test standards are in place.

Not to mention but most of them are also long-stroke motors that resist revving, so a cam change isn't enough to get them to open up, and they'll never reach high revs (unlike most 90s 4-cylinders a la Nissan and Honda.)

At a certain point, if you have to buy new subframes, mounts, transmissions, engine blocks, heads, pistons, crank, cam, valves, springs, and more, why would you do that for a Chevy sonic? There are better chassis out there that will be cheaper.

Technologically, I don't think we've really found a way to make more power out of engines, as much as we've been able to do it with less compromises. People have been making 600HP 2 liter 4-cylinders since literally the 40s and 50s. They however, were heavy iron head-in-block engines with extreme cams and superchargers that netted single-digit fuel economy and required an entire block rebuild every 4000 miles.

Sweet Trav > GhostZ 09/13/2014 at 12:02

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This is one of those things that i will never understand, you don't NEED to rev very high if you have adequate gearing. some of the new dual clutch transmissions can shift so fast you'd never know you were breaking the powerband to shift. God forbid they ever build a good high performance CVT. Why would you even want an engine to rev high, it offers much more chance for mechanical failure.

For instance, Take the 500 cid caddy motor. For next to nothing (if you can find one), you can make great torque and horsepower at an obscenely low RPM http://www.hotrod.com/techarticles/e… They did that in '98. Can you imagine if you used a turbo also?

Combine that to an 8l90E and good rear end gear and you'd never have to run the engine at more than 4k.

But yes the 500 Caddy is gigantic, whale sized and weighs almost as much as an Ariel Atom, but the principle still stands.

Conversely, the GM ecotec has been built to over 1400 hp for NOPI drag cars. 600 hp out of two liters it not unfathomable for the street without running more than say 6500rpm.

And if we aren't getting "more" power out of engines, how is the specific output of engines rising so rapidly WITHOUT the increase of RPM. Take the 1l Ecoboost for example or the 2.3t in the new mustang or the CLA turbo 4.

GhostZ > Sweet Trav 09/13/2014 at 12:28

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Increasing power through RPM increases the effective boost through pressure differentials caused by the opening and closing of valves. The faster they open and close, the more dramatic the effect, because the thermodynamics of air stay the same no matter what the engine is revving at. It's also more of an effect on NA engines than boosted ones, but there's still an effect on turbocharged engines too, especially on the exhaust side.

Just because production cars are making more power, doesn't mean that the potential power that an engine makes is going up. I have no doubt in my mind you can get a 600HP ecotec, but are we really going to see them on the street?

Power comes from forcing more air into the cylinder, and constricting it with more force. That comes from boost, RPM, or displacement. Higher RPMs are almost universally better way to increase power, but they do come at the highest cost and the lowest limits.

Increasing power through displacement necessitates larger pistons and crank, which adds rotating weight to the engine, counteracting in some small way the gains you get through increased displacement. Not to mention that adding stroke to an engine increases the mean (and peak) piston acceleration proportional to the increase in stroke. This means that for every extra 100HP you'd gain out of increasing the stroke of an engine, you'd lose 100HP out of reducing the RPM tolerances of the rotating assembly. This only matters if, however, the rotating assembly is the limiting factor in RPM . It isn't, usually, unless you're running a stroke over 4", where conrods and pistons start becoming more likely to crack than valve float or running out of the cam's range.

Conversely, increasing displacement via bore (without reducing cylinder wall, mind you) necessitates exponentially (literally, as it is a function of a radius of a circle inside a square) more engine block to run appropriately. This creates significantly heavier blocks. That's why the Caddy 500 weighs so much more than a Ford 302, because to necessitate the larger bores there is physically more mass added to the engine. A 1" increase in bore spacing could almost double the weight of the block, depending on how large it is.

Increasing power through a higher compression ratio improves the thermal efficiency of the otto cycle, but comes at a very quick limit from knocking, which you probably already know about.

Increasing power through boost has a ton of benefits with slightly less drawbacks. It's a lot more complicated than I can get into, though, but it does improve energy efficiency at the side effect of having lots of thermal and aerodynamic nastiness.

Lastly, increasing power through RPM produces more power without adding any weight to any part except for maybe the valve springs, which can increase more friction. However, having to switch from OHV to OHC does add considerable weight (and even more if you add more cams) but is worth it for the gains in efficiency, fewer moving parts, and heightened speed that the cam can run. Revving to a higher RPM allows two things to happen:

1. Given that the intake and exhaust are designed for it, intake pressure and exhaust vacuum caused by the valves increases in force. Some N/A engines can gain an effect boost of around 2-3 PSI rather easily. BMW was well known for utilizing this type of intake their intakes for the M cars in the 80s and 90s, and I think audi has a "variable length" intake that adjusts to maximize the effect depending on the rev range. The Taurus SHO had something like that too, along with other cars.

2. No added friction if valve springs are maintained. Valve spring and cam friction is a hugeimpact, and that's why most companies use lower-revs with boost. It allows them to run at lower revs far more efficiency since they don't have to press heavy valve springs with aggressive cams with each cycle. This, however, reduces the peak power that the engine can produce significantly. They're just getting it back via adding more boost.

So in other words, if you increase the stroke in the engine, you could always have increased the peak HP rpm proportionally and gained even more power, provided you haven't reached the limitations of the valvetrain, since you have less friction AND an increased intake pressure effect.

If you increase via boost, you have to reduce the peak gains through increased cooling (either water cooling, methanol injection, etc.) to keep intake temperatures low to prevent knocking. Generally, there are fewer peak drawbacks with a turbo and more drawbacks with the effect on the whole powerband, given that turbines tend to only operate best in a certain RPM range. But with variable geometry turbos, that's been mostly solved.

I feel that you probably know most of this already, but I got into it and realized that it was fun to explain all of this so I did it anyway.

Cé hé sin > StingrayJake 09/13/2014 at 12:34

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Reminding people that the only American thing about the GT40 was its engine is not popular in some quarters.

StingrayJake > Cé hé sin 09/13/2014 at 12:40

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One wonders if A/C and Lola would be so noted and cherished for their design if Shelby/Ford hadn't come along. Just another Brit roadster/race car without the American heartbeat.

Sweet Trav > GhostZ 09/13/2014 at 12:49

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While i agree with 99.8% of what you have said, there is one item that throws most of the turbocharging information out the window, Variable Geometry Turbos.

The simplest analogy is this, Remember the pinwheels you'd get at as kid? it either took a lot of volume or pressure to spin it, As you stated the thermodynamics of air (in this case exhaust) stay the same regardless of engine speed. With a properly engineered VG turbo (technology and reliability arent quite there mind you) you could in essence have an engine under boost through vast majority of its rev range, cam phasing helps this quite a bit too.

Lastly, increasing power through RPM produces more power without adding any weight to any part except for maybe the valve springs, which can increase more friction.

I disagree, The durability of the rotating mass also has to be addressed to hit high RPM because of piston travel and speed. Stronger main caps, more main bolts, thicker stronger con-rods also piston weight come into play. You do have to typically have to add stronger, typically heavier components to reliably withstand higher RPM in the rotating mass. I could make a 3 cylinder Geo motor make 800hp for about .15 seconds before it melted down. Though, all that being said metallurgy has come a long way in recent years with titanium components found in engines.

The limits of a specfic engine always come down to two things, the physical mechanical limits of the strength of the components and the fuel's ability to resist detonation.

I can, and would argue that while the fuel has collectively gotten worse, the materials and design of engines, collectively have gotten better. Plus when you look at all the stupid rules and regs in racing we're really stifling engine development, Imagine an unlimited class in NASCAR or F1 and the beautiful tech that it would provide the mainstream car market in future years...

GhostZ > Sweet Trav 09/13/2014 at 12:58

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I mentioned variable geometry turbos, and you're totally right.

As for the RPM increase, that was in reference to doing that holding everything else constant. If you can stroke the motor, holding everything else constant, you can increase the revs too. It's only if you try to go beyond either of their limits that you need to add strength through the mains, rods, or pistons.

There's also the issue of balancing, which I didn't mention but should have. Increasing power through RPM does necessitate more precise balancing of the crank.

In general, RPM has the least drawbacks mechanically, but the most drawbacks financially I think, but goes to show that there are very few 'untapped' areas of engine modifying that I think we'd ever be likely to enter.

I think Ethanol is a saving grace in regards to fuel. Terrible policy, terrible idea, stupid, stupid, stupid, but it did give us cheap (relative to how expensive it is to make) fuel that turbos love. If you're willing to give up some cost and fuel economy, it's like the modern nitromethane (but not quite as extreme as full-on race fuel) before nitromethane got regulated. Then there's always methanol injection.

If racing safety regs hadn't come in, we'd be sitting around the 310mph mark with ~1700-2000 HP motors in 900kg prototype cars. That is the technological limit of what I believe we can do right now. Sure, we can make more power or less weight or higher top speed, but not without compromising something else dramatically, or making the car undriveable.

Sweet Trav > GhostZ 09/13/2014 at 13:04

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Where's my V17 Quad Turbo that runs on diced lions?

Good discussion sir.