2.5L with lower revs/more torque, or 2.0L with higher revs?

[Mikem53]

Originally Posted by OrbitalEllipses

I dream of all aluminum V8 swaps into this chassis. Possibly with built internals or a stroker kit.

It would overpower the chassis in this car at stock power levels..
would kill the finesse of the ride.. I like the ability to wind it out
and keep the revs up.. The FA20 tries hard.. which makes it more
fun to drive.. While the LSx motors have the TQ and HP many wish for..
They do require a proper platform to match the other components to the power..
My 08 vette weighed 3210 lbs.. and I had 2LT trim to keep the weight down too.. the new ones are now 3445 lbs..
the lighter sports car is more fun to drive.. power is secondary to handling
for me.. it didnt used to be that way.... but it is now..
The LSx is a great replacement for the I6s used in the BMW's.. thats a great
platform for that engine..

[G_Ride]

Given the two choices, I'd have to go with the 2.0L screamer. However, I'd have to side with @mad_sb: a high revving 2.2L. You could still design a reliable high revving engine and the torque benefit of the larger displacement.

[Ingen]

Originally Posted by diss7

There's a 2 door, lightweight, rear wheel drive, good looking wrx? Kthxbi

2.5RS?

[Genomaxter]

Sorry, I'll pass on displacement. If offered a 4.8L v10 LFA or a 8.0L v10 Viper, i would take the LFA every time.

Any time you increase the liters, you need to increase the flow of the head while keeping the stroke from getting too long other wise the VE (volumetric efficiency) will drop like a rock and so will the rev range.

If they made a 2.5L without making a much larger head, then it will have much lower revs, it WONT hit 250 hp since the VE will drop as well and it still wont have any character in the upper range.

I love high revs for the sound the most and I want the engine power to follow those revs as much as possible. I dont want a truck engine. I dont care about how many cylinders a car has, I just want between .45 to .55 liters per cylinder with revs going 7.5k+. Preferably above 8k.

The problem I see with the current 2.0 running out of power after 7k rev is the intake manifold design. Its very low rev bias. Great for daily driving and all, but long runners and a relatively small intake plenum causes the engine to run out of breath at the top of the range since it just cant pull the air in quick enough. With the length of the runners currently, they managed to try and make up for it by increasing to throttle body size, but that wont fix it since its still a long path from the plenum to the intake valves. Id like to see more of a Porsche style manifold. Throttle body in the middle with a plenum and shorter intake runners on each bank.

[ZDan]

Originally Posted by Genomaxter

Sorry, I'll pass on displacement. If offered a 4.8L v10 LFA or a 8.0L v10 Viper, i would take the LFA every time.

Well, that's kind of a different question...

If they made a 2.5L without making a much larger head,

Larger head?!
The size of the heads are pretty much dictated by the size of the block. Whether you maximize the valve area and go with high lift high duration cam or not won't really affect the heads' SIZE.

I love high revs for the sound the most and I want the engine power to follow those revs as much as possible. I dont want a truck engine.

I don't see how a 2.5 liter revving to 7400rpm and making 250hp would be a "truck engine".

I dont care about how many cylinders a car has, I just want between .45 to .55 liters per cylinder with revs going 7.5k+. Preferably above 8k.

You do know that number of cylinders has a PROFOUND influence on the SOUND. Seems bizarre to me to be fixated on 0.5 liters/cylinder, +/-. For me, diversity = goood...

The problem I see with the current 2.0 running out of power after 7k rev is the intake manifold design..

I can assure you that the intake manifold design is totally consistent with the engine. If they'd wanted to rev to 9000, the biggest changes would be in THE HEADS. The intake manifold would be different to SUPPORT that. It's not like you could make some magical intake manifold that would make the FA20 a 9000rpm screamer with no other changes.

[StormTrooper]

The rumours out of nameless is that with the newest header power peaks at nearly 8k with more low end.

Magic? Idk but I'm interested.

Our cars need 3-4k improved not a 5% jump at 7500 . Daily and track use, the only time a super peaky band is better is drag racing and the 86 sucks at that

[Genomaxter]

Originally Posted by ZDan

Well, that's kind of a different question...

Same question. More or less liters with the same amount of cylinders. Just different rev and power curves.

Originally Posted by ZDan

Larger head?!
The size of the heads are pretty much dictated by the size of the block. Whether you maximize the valve area and go with high lift high duration cam or not won't really affect the heads' SIZE.

Never seen the Toyota ZZ engine family have you? 1zz and 2zz are both 1.8L, 2zz has a much larger head design to go with the 2 stage cam profile and shorter stroke. Tell me how that's dictated by block size when both are 1.8L cause both short blocks are both the same dimension and only the 2zz head is larger by a good margin to support the higher revs.

Originally Posted by ZDan

I don't see how a 2.5 liter revving to 7400rpm and making 250hp would be a "truck engine".

It wont make 250hp. They wont make the head and intake manifold size large enough to support that. At best it might make 235hp with a factory tune if they went 2.5L.

Originally Posted by ZDan

You do know that number of cylinders has a PROFOUND influence on the SOUND. Seems bizarre to me to be fixated on 0.5 liters/cylinder, +/-. For me, diversity = goood...

Like I said previously, number of cylinders doesnt matter to me, only revs. Higher revs on any amount of cylinders always sounds nicer at 8K than anything puttering around below 7K. Better is objective when it comes to sound, so no point in that debate. That's just my pov.

Originally Posted by ZDan

I can assure you that the intake manifold design is totally consistent with the engine. If they'd wanted to rev to 9000, the biggest changes would be in THE HEADS. The intake manifold would be different to SUPPORT that. It's not like you could make some magical intake manifold that would make the FA20 a 9000rpm screamer with no other changes.

I can assure you they arent. Its obvious because everybody knows the car runs out of breath up high. Intake manifold design has just as profound affect on power band as cams and head design. In the head design, they chose to build one that can easily rev past 8k rpms, but they chose not to since they were obviously not happy with the low end during testing. The runner lengths and plenum show this. Why would they overbuild a head design if they never planned to rev that high to begin with? They didnt. They just chose to change the easier of the two to give the car more low end grunt. Head profile and cams are expensive to design and take much longer. Why bother when they can just change the manifold to meet their goal. And if they did build the head for the lower power range, why overbuild it so much. Its an unnecessary cost.

[StormTrooper]

If you read the article, tada talks about a 2.5L as a real possibility.

Rumours that the HP increase would go from 147kw to 190kw
Or 197 HP to 258 ....

[Anaxilus]

1zz comparison to 2zz has nothing to do w/ the FA20 or a potential 25. Toyota was married to VVTLi long before they developed direct injection. The FA20 gets 100hp/L w/o VVTLi and so could a 2.5L. I'm pretty sure you could rework a stock FA20 head along w/ the intake manifold, intake and exhaust to flow enough air to hit 250bhp w/o making the head itself 'bigger'.

While the 4.8 V10 is AMAZING as an engine unto itself. It's actually quite a poor match to a 3500-3600lb car due to the lack of relative torque. This is one reason the 8.0 Viper ACR was able to outdo the LFA Nurburgring using essentially a tractor motor. If only the LFA was lighter. Still, the 4.8 is awesome and the best sounding engine you could have bought recently. Unless you have a thing for cross plane cranks for some reason....

Now, if someone wants to put 5 valves/cylinder on a 2.5L H-6 with ITBs, I'd go for that. Drop another 200lbs and I'll give Toyota a $40K starting bid.

[ZDan]

Originally Posted by Genomaxter

Never seen the Toyota ZZ engine family have you? 1zz and 2zz are both 1.8L, 2zz has a much larger head design to go with the 2 stage cam profile and shorter stroke. Tell me how that's dictated by block size when both are 1.8L cause both short blocks are both the same dimension and only the 2zz head is larger by a good margin to support the higher revs.

I've never heard anyone suggest "it needs BIGGER head(s)!" when they want higher rpm breathing. Typically you go bigger cams with more overlap and hog out the intake/exhaust tracts. If you *meant* it needs to go to a head with multiple cam profiles, why not just say that?
I DD an S2000, so it's not like I'm unfamiliar with the concept. It's not like the F20C/F22C head is ginormous, btw, maybe Toyota needed more volume to accomplish the same thing...
Anyway, it's probably a non-starter for a more budget-oriented car.

It wont make 250hp. They wont make the head and intake manifold size large enough to support that. At best it might make 235hp with a factory tune if they went 2.5L.

If they want to, they can make 250hp with a 2.5 liter as easily as they made 200hp with the 2.0 liter.
If they want to make 250hp with 2.0 liters, that's doable but more difficult.

Again, you're barking up the wrong tree with intake manifold size. Individual runners and NO intake manifold would work best for higher-rpm breathing, anyway.

Like I said previously, number of cylinders doesnt matter to me, only revs. Higher revs on any amount of cylinders always sounds nicer at 8K than anything puttering around below 7K. Better is objective when it comes to sound, so no point in that debate. That's just my pov.

You're talking about engine sound and throwing cylinder count out the window?
No argument from me that 8 or 9000rpm sounds sweet.
If you meant to say it's SUBjective, I agree.

(Regarding my comment about the intake manifold being consistent with the engine design goals)

I can assure you they arent. Its obvious because everybody knows the car runs out of breath up high.

??? Every engine will run out of breath if you rev it high enough. The engine is designed and built to rev to 7400rpm (with the generous margins of safety and design life the factory wants for it). Peak power at 7000 is pretty near what they determined to be the rev limit.

Intake manifold design has just as profound affect on power band as cams and head design.

Obviously the intake manifold shouldn't be restrictive for the revs the engine is designed for.

In the head design, they chose to build one that can easily rev past 8k rpms, but they chose not to since they were obviously not happy with the low end during testing. The runner lengths and plenum show this. Why would they overbuild a head design if they never planned to rev that high to begin with? They didnt. They just chose to change the easier of the two to give the car more low end grunt.

Are you suggesting that the head/cams are built to make power at 8000rpm, and they are using the INTAKE MANIFOLD to cut that to 7000?! That's absurd. The head and cams are designed around 7000rpm, and the intake manifold and exhaust support that. You can open up and derestrict the intake all you want, and you will gain some power/torque, but you'll still be making peak power at ~7000rpm even if you go to ITBs. Because that's the rpm the head and cams were built to maximize breathing at.

Head profile and cams are expensive to design and take much longer. Why bother when they can just change the manifold to meet their goal.

They build engines, they have cam grinders, It's not going to be that big a deal to them to try different grinds. And I'm sure that their cam guys know enough about how to get what they want that they're pretty close with the first prototypes. Same with runner sizes. If they have to modify these by adding or taking away material here and there, it's not rocket science to do this in the prototype stage.

And if they did build the head for the lower power range, why overbuild it so much. Its an unnecessary cost.

Why do you think it's "overbuilt"?

There is NO WAY they designed and built an 8000+rpm screamer, and then plugged it up with the intake manifold. I submit that it's going to be a ~7000rpm peak horsepower engine no matter what you do with the intake. You can gain a few hp and lb-ft, but it's still going to be optimized ~7000rpm until you go in and change the cams, and you might need to open up intake/exhaust runners as well.

[ZDan]

Originally Posted by StormTrooper

The rumours out of nameless is that with the newest header power peaks at nearly 8k with more low end.

With stock cams? No way. Headers and lower-restriction exhaust will not give this engine an 8000rpm power peak. Same as with the intake manifold, you can free it up all you want and peak power is going to remain around 7000 until you go to different cam profiles with greater lift and overlap, and possibly port out intake/exhaust runners to support that.

There is NO magic!

Our cars need 3-4k improved not a 5% jump at 7500 . Daily and track use, the only time a super peaky band is better is drag racing and the 86 sucks at that

You're saying this car needs to rev 3000 to 4000rpm higher? That would be nice but I don't see it happening, not by a long shot! Suffice it to say it would take a LOT more than an intake manifold and a header to get there...

[arghx7]

^ knows what's up. The valve events and intake port characteristic typically have the biggest effect on the powerband for an n/a engine. The other stuff is more like the supporting cast.

Also, whoever was designing the FA20 used a 1D model (GT Power software) to narrow down the valve timing and runner lengths/diameters to achieve the targets. One thing to keep in mind is that the FA20 can dial in a lot of scavenging compared to a 2ZZ, because it has cam phasers on intake and exhaust, and it has direct injection. The FA20 does not have 2-step cam profiles, probably because they didn't want to spend the money on it.

[arghx7]

The FA20 doesn't need more overlap for high rpm operation. Remember, it can already dial in a ton of overlap, which is what it does at low rpm like every other DOHC GDI engine with dual cam phasers. Typically at high rpm you want a longer duration and later closing. When you can phase both intake and exhaust, the baseline overlap on the cam grind has a lot less importance. On a fixed overlap type of engine like a GM smallblock, it's different because you don't have that flexibility. All the cam phasers on GM smallblocks move both intake and exhaust events equally--they can't dial in overlap at will.

Look at BMW n/a Valvetronic engines. They close the intake valve later at high rpm and use more lift and duration. At low rpm they use earlier closing, more overlap, and low lift/duration. That's why continouusly variable valve lift n/a engiens are practically maxed out in their valve events.

[86TruenoFRS]

this is the biggest discussion in the S2k forums w/ the option of a 2.0L(F20 9K redline) and 2.2L(F22 8.2K redline). I've driven both(s2k wise) and I would take more displacement over higher revs. Reason being is that most of us drive our cars on the street and do really have the opportunity to take the car into the high rev range. w/ the 2.5L you will have more low end torque that you will feel every day rather than when you are just doing spirited driving... now I do understand that there are some track junkies and hight revs would benefit them but for the average Joe, 2.5L would suffice. just my .02