I’ve been intrigued with the idea of a small car with V8 sound and performance. In the 70’s, Alfa Romeo built a car named the Montreal with a 2.6 liter V8. I believe the engine produced 170-200 HP. This is about the same as Nissan’s current 2.5 liter I4 used in the Altima and Sentra. Triumph utilized a V8 (3.5 liter) in the TR8. It produced about 160 HP (a poor level compared to today’s V6’s of a similar size).
It seems to me that with today’s technology, a small V8 would give consumers a good alternative to buzzy 4 bangers and greater performance to the V6 crowd. What am I missing? What are the engineering or cost problems associated with a low volume V8?
IIRC, GM marketed a 3.5 Liter V8 through Olds and Buick during the 60s
During the big-block high-horsepower years, the 3.5 was abandoned and the tooling sold to Land Rover, though IIRC todays 3.8 Liter V6 is a direct decendant.
What is it about a V8 you like? One advantage used to be noise and vibration, but with all the balance shafts and active engine mounts and whatnot, four-bangers are pretty quiet. Torque at low revs is a different story.
Mazda used to build a 1.8L V6 for the old MX3. I think that one lasted until about 1995.
The engine size and performance range you ask about is being filled with V6 engines. The great majority of folks are happy with them. There’s no need nor demand for a small V8, so they don’t make them.
What basically affects performance is the displacement of the engine(and forced induction systems, if they are present), not the number of cylinders.
Having 8 cylinders in a small displacement engine would actually be a drawback, because more cylinders equal more friction, engine weight and bigger surfaces which results to heat loss.
I have not delved deep enough into car engine mechanics, but I believe there are optimal combinations of number of cylinders and displacements, and also things such as bore/stroke ratio.
By the way, engine design technology hasn’t changed so much over the years. Modern engines are more efficient and powerful basically due to improvements in materials, fuels and electronic management systems.
Some though of Honda S2000, capable of producing 120hp/liter, as a breakthrough in engine design. It isn’t. Just look at rally cars of the 60’s and 70’s. They were also capable of producing such engines back then. What Honda accomplished, was to make such engines cheaper, reliable, cleaner and less fuel-consuming.
Not quite… the big breakthrough in regards to Honda’s S2000 engine is the ability to deliver a very impressive torque curve throughout the entire rev range from 1,200 to 9,500 rpm. And it’s usable torque too… THAT is the achievement.
So how did they do it? And why were high performance engines delivering 120+hp per liter in the 1960’s so much less usable? The answer lies in the nature of air pressure shock waves - and the knowledge that such shock waves can be ‘tuned’ to overlap so that double waves of pressure hit the inlet valves at ‘opening time’ to ensure that greater amounts of air can get into the cylinders.
As is always the case, getting fuel into an engine isn’t the issue - it’s getting the most amount of air that counts - followed by the most amount of vapourised fuel possible - followed by the least advanced ignition timing possible - followed by the highest compression possible before the onset of pre-detonation.
All of these factors have had incredible technology and intelligence thrown at them over the last 20 years since the advent of micro-chip technology - and it’s quite the disservice to Honda (and other major Formula One engine designers) to imply that they’re not “really” doing anything which hadn’t been done before. Nothing, (in reality) could be further from the truth.
Wonderful concepts such a variable valve timing (both inlet and outlet) allow gases to move at optimal rates right through a remarkably broad rev range. And now we also have variable length inlet tracts as well - which allow the shock waves of inlet air pressure to bounce between the butterfly valve and the inlet valves at just the right times so that they “double up” upon entry into the cylinders. And anti-knock sensors and variable ignition timing all get thrown into the mix to provide stunning horsepower at high revs, and amazing fuel efficiency and usable torque at low revs.
So, in the context of high performace engines of the late 60’s and early 70’s - well, it has to be said that engines from that era which produced 120+hp/liter back then were very, VERY twitchy engines. They had very narrow rev bands, and were characterised by woeful usable torque below anything other than say 6,000 rpm. An example… the 1978 Brian Hart 2 litre Formula Two engine which finally ended BMW’s reign of six straight European Formula Two championships in 1978. It produced just on 300 hp from a 2 liter engine. It IDLED at 4,200 rpm, and it’s usable power was from 8,000 rpm to 11,500 rpm. Anything less than 6,000 rpm and the engine would stall when you let out the clutch.
THAT’s why modern engines shit on older engines from the 1960’s. They are extraordinarily more flexible, usable, efficient and friendly.
In closing, I would have loved to have seen Honda release a 3 liter V8 in their legendary NSX. That would have been a car for the ages I rather think.
One reason not to build a 2.5 litre V8 instead of a 4 is that the V8 will cost a lot more to manufacture. You have to double the number of pistons, valves, camshafts, spark plugs, etc, etc, complicate the intake and exhaust manifolds, and so on and so forth. These parts are all smaller, but will cost much more than half as much as the fewer, larger parts for a 4 cyl of equal displacement. So you build this snappy sports car with a micro V8, but it’s in the same class as a competitor’s 4 cylinder, and it costs substantially more. Sure, it’s torque curve will look a little different, maybe even better, and it will sound really good, but that’s a high price to pay for such minor advantages.
So basically you shouldn’t ever expect to see something like this except in high end cars where prospective buyers won’t care about an extra couple thousand bucks in the price tag.
Actually, what I had in mind from the 70’s era was something along the lines of Ford Escort or Fiat 131. I hadn’t the opportunity to drive one of these cars, but some older folks who have driven them back then(the road versions apparently), tell me that engine response was amazing even by today’s standards.
I don’t follow your point here. They had a firm grasp of those concepts back in the 70’s too. Today engine makers can fine-tune their designs using mathematical modelling software(for predicting air flow), back in the 70’s they had to do it by trial and error.
I didn’t say that 70’s engines are better or even equal to today’s engines. I was refering to design only. After all, all engine parts are still operating on the same principles (pistons, camshafts, valves, crankshafts etc.) The basic engine design hasn’t changed.
What would be the advantage of a 3.0L V8 as opposed to the standard 3.0L V6 engine?
With twice the cylinders, a small V-8 would sound twice as buzzy as a four running at the same RPM. Buzzier actually–most modern engines are slightly undersquare (with a stroke that is slightly smaller than the bore), so the eight would work best with a top end designed to run at much higher RPMs than the four. You would end up with the equivalent of two motorcycle engines sharing a common crankshaft.
Beyond that, I’m sure that most manufacturers already have large cylinders pretty well modeled. They know how to maximize efficiency, reduce emissions and the like for 500-750cc cylinders. A drastically smaller cylinder is off the scale, and they would have to spend time characterizing it from scratch.
Besides, there wouldn’t be much to gain from rebuilding that wheel. As others have said, modern fours run fairly smoothly, buyers seem happy with the current fours and sixes and an eight would cost more to manufacture.
(Dog80, I’m no expert, but I assume that heat can be managed, and a smaller cylinder would be less prone to preignition or detonation.)
By asking for a small displacement V8, you are discounting the balance, feel, flexibility, response and benefits inherent is some brutally smooth, incredibly performing V-6 and I-6 engines. Nissan, Honda and BMW - among others - make some killer engines with 6 cylinders.
Actually, six and twelve seems to be the combo for smooth refined power. It comes in sixes. V-8s and V-10s don’t quite meet the standard set by 6 and 12 cylinder powerplants.
Apparently the above is an oversimplification, because the cylinder walls, the piston and the cylinder head all probably have different rates of heat loss. But I believe that the argument still holds.
MINOR!? Those are the only advantages worth discussing, IMO. Alfa Romeo proved the concept viable with the Montreal. 200 HP out of 2.5 liters in the mid-70’s, no less! I can buy the argument of increased costs due to more parts but consumers might be apt to pay extra $$ seeing a V8 badge on the quarter panel and real dual exhaust.
BTW, most “performance” 4-cylinders I’ve ever driven are no where near as refined feeling or sounding as V6’s or V8’s. Nissan’s SR20DE is among the best. Maybe this is something you’d find in an upscale brand. So what? Consumers are power crazy right now. Look what people are paying for these Super Subaru’s and Mitsu’s these days. A V8 powered Neon might give 'em some competition.
The problem making a small v-8 is it wouldn’t have any torque it would be able to make lots of power but would be reving over 6500rpm to do so,
Engine balace V-6s are some of the worst when it comes to iherent balance of the engine it took a long time before they could be made to run smooth they had to use balance shafts and even fire cranks. Inline 4s are inherently well balaced V-8s a little less than the inline 4 but with even fire cranks are fairly close to the 4 cylinder if not better.
For a street car you want a lot of torque down low for easy off the line starts. A V-6 will likely make more torque down low than a V-8 of the same size because the bore and stroke on the V-6.
A V-8 will be heavier and have more parts than the V-6 the only reason to go with more cylinders is if you like the sound a V-8 makes, from the factory they wont worry with this because most pepole don’t want to hear the engine at all and they can make them fairly quiet. The other reason will be if you want a higher rpm engine, for a street car that is not practicle as it wont have the low end torque.
It sounds like you’re suggesting that Honda and other modern powerplant builders haven’t achieved anything because they haven’t replaced the petrol internal combustion engine…
Besides, the truth about the Alfa Montreal experiment is obvious to anyone who’s driven one. Yes, it was a wonderful motor, with an nice smooth powerband, and it sounded great. Unfortunately, like almost everything Alfa built from about 1964 onward, it fell apart quicker than the model aeroplane I built out of polystyrene and a cannibalized r/c car motor when I was eight.
That engine quite literally shook itself to bits.
The simplest way to answer the OP is this: there is a certain range of volumes at which an individual cylinder operates with a degree of stability. Make your cylinders too big, and you get a washing-machine effect- the engine will shake the car at high revs. Thus, you don’t see four cylinder engines larger than 3 liters (Porsche bored and stroked the inline four from the 944 S2 to produce the 3.0 four used in the 968, which was to the best of my knowledge the largest production four ever. Even that was only practical because they used balancer shafts). Make your cylinders too small, and the engine will only operate efficiently when spinning extremely quickly. Works fine for, say, a Formula One engine, but the characteristics of a 3.0 V8 or V10 are not exactly what you want in a road car.
A 4.6 liter Mustang has a cylinder volume of 575cc. A 2.5 liter 4-cylinder has a larger volume of 625cc per cylinder yet the sound from the respective exhaust systems is completely different. V8’s just sound better.
Even if everything else was the same, I’d take that sound any day. My assumption is that there would be other advantages. It seems a pretty common belief that V8 engines deliver smoother power. Maybe this is due to the usual increase in engine size or maybe more pistons equal smoother rotation.
As far as the RX-8 goes…they need to figure out how to boost the torque and increase mpg. Otherwise, I like those rear doors.
