[shaffe]

Originally Posted by whiteboyblues2001

Yes, this is where we both are scratching our heads. The theoretical limit to an FPC V8 engine is about 5.0L. Ford went 5.2L and has tons of problems, but let's do some math.

Even though the Voodoo has a redline of 8,250, peak power is at 7,500 for 526 HP. If you kept the same displacment and increased peak power to 8,500 RPM's (assming you can keep the same torque number), it would put out a theoretical 596 HP. Pretty close to the rumored 600 HP. And it's theoretically possible in accordance with the article I linked becasue it says that the redline was limited to 8,600 due to the transmission.

Here's another theoretical example. Suppose they went with peak power at 7,500 like the Voodoo, but used 5.5L. That would put out a theoretical 556 HP. Not enough to make it to 600 HP without reving higher.

So, who knows...

What I do know, is that if this is going to be N/A and 600 or so HP, it will have to rev pretty high, and produce peak power above 8,000 or more RPMs. This will make the engine lack the low end in comparison to the LT2, but for a track car (road course), high RPM N/A makes sense.

But these examples show that they can't really go with a significantly lower displacement than the Voodoo, or it would have to rev higher than the transmisssion can take. It will have to be at least 5.0L, but more than likely a bit more.

I guess 5.5L is still on the table...

It's not the power that has me scratching my head. I believe they can make the power.

What has me scratching my head is how can they do it reliably. It's not like GM has a great history of making DOHC V-8s and they are going to jsut jump right in and make the largest displacement FPC ever made. How are they going to do it without it vibrating itself to pieces.

I am going to say if it does go FPC, it will be a smaller displacement than 5.0L and have a set of hairdryers on it. The only way I see a 5.5L coming is if it is a normal CPC DOHC engine.

[whiteboyblues2001]

Originally Posted by shaffe

It's not the power that has me scratching my head. I believe they can make the power.

What has me scratching my head is how can they do it reliably. It's not like GM has a great history of making DOHC V-8s and they are going to jsut jump right in and make the largest displacement FPC ever made. How are they going to do it without it vibrating itself to pieces.

I am going to say if it does go FPC, it will be a smaller displacement than 5.0L and have a set of hairdryers on it. The only way I see a 5.5L coming is if it is a normal CPC DOHC engine.

Keep in mind that this is a balance issue. And every inline-4 cylinder has that same balance issue (because an FPC V8 is just two inline-4 cyliders strapped to a common crankshaft). And the theoretical limit to a inline-4 cylinder is 2.0L. There are plenty of 4 cylinders larger than 2.0L. They do it by introducing a balance shaft with weights to counterbalance the vibrations.

In an FPC engine, adding a balance shaft may solve the vibration issue, but it will add more mass back into the rotating assembly. Light wight rotating assembly is one of the best features of going FPC in the first place, as it allows the engine to rev up quicker.

So, there are ways to get around the vibration issues, but you have to compromise somewhere, so perhaps they will go with a balance shaft and add a bit more mass to the rotating assembly.

Also keep in mind that the transmission can only take 8,600 RPMs, which isn't crazy high for an FPC engine. Some rev up to 9,000 RPMs.

Also also, Ford had to use a different firing order than a traditional FPC becasue they couldn't use two sperate intakes due to pacakging issues. So, it's a bit of an apples to oranges comparison here, as the firing order has a huge effect on vibrations.

[RobbyBeefcake87]

Originally Posted by whiteboyblues2001

The rumors are swirling the last few days. Here is an article from yesterday saying that the Z06 will be an 5.5L FPC N/A for around 600HP.

https://news.yahoo.com/know-flat-pla...171800233.html

5.5L and FPC will be a challenge for sure. But, the design would allow for the Z06 to return to it's N/A roots.

ALSO, since they extended the life of the 6th gen by two years, that leaves plenty of time for this new Z06 engine to show up in a Z/28 camaro. If it will fit, that is. But since the new C8 has an LT2 and will have a 5.5 DOHC later, then perhaps they are of comperable size...

This is what I was alluding to about the z06 being NA. Less power than the current z06 but I will be a faster car imo.

[RobbyBeefcake87]

Originally Posted by Martinjlm

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.

This. Perhaps more reciprocating mass in the valvetrain, but not more moving parts.

[Idaho2018GTPremium]

Originally Posted by Martinjlm

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.

Yes, you're right. I guess I should have said more moving parts to move a given valve. Cam-lifter-pushrod-rocker arm-valve. But yes because of the sheer amount of valves and cams there are more moving parts overall in the DOHC engine.

If I recall correctly, an OHV VVT can not control the exhaust timing separately from the intake timing like a DOHC since they are controlled by separate cams.

[Craig]

Work bench efficiency vs. real world efficiency. Power, fuel economy, and packaging are all that matters when driving the cars. Compared to the A10 LT1, the A10 Coyote has comparable gas mileage, comparable power, notably less torque, a higher COG, and is physically gigantic in size.

Check out the side by side pics in this article. A blown 376 LSX crate engine takes up less space in the engine bay that a stock Coyote. Who cares how big the pistons are?

https://www.enginelabs.com/news/ford...-hp-per-pound/

[IneedAZ]

More C8 engine rumors
https://www.autoblog.com/2019/08/29/...engine-rumors/

[RobbyBeefcake87]

Originally Posted by Craig

Work bench efficiency vs. real world efficiency. Power, fuel economy, and packaging are all that matters when driving the cars. Compared to the A10 LT1, the A10 Coyote has comparable gas mileage, comparable power, notably less torque, a higher COG, and is physically gigantic in size.

Check out the side by side pics in this article. A blown 376 LSX crate engine takes up less space in the engine bay that a stock Coyote. Who cares how big the pistons are?

https://www.enginelabs.com/news/ford...-hp-per-pound/

Displacement is almost irrelevan at this point as far as comparing engine output for its size.

Still so many people have no clue and just claim and engine is enormous due to large displacement.

[shaffe]

Originally Posted by Craig

Work bench efficiency vs. real world efficiency. Power, fuel economy, and packaging are all that matters when driving the cars. Compared to the A10 LT1, the A10 Coyote has comparable gas mileage, comparable power, notably less torque, a higher COG, and is physically gigantic in size.

Check out the side by side pics in this article. A blown 376 LSX crate engine takes up less space in the engine bay that a stock Coyote. Who cares how big the pistons are?

https://www.enginelabs.com/news/ford...-hp-per-pound/

But the Coyote doesn't need cylinder deactivation lol

Originally Posted by RobbyBeefcake87

Displacement is almost irrelevan at this point as far as comparing engine output for its size.

Still so many people have no clue and just claim and engine is enormous due to large displacement.

True.

[Idaho2018GTPremium]

Originally Posted by IneedAZ

More C8 engine rumors
https://www.autoblog.com/2019/08/29/...engine-rumors/

Those numbers are so far off it doesn't even make sense.

[Martinjlm]

Originally Posted by Idaho2018GTPremium

Those numbers are so far off it doesn't even make sense.

The only numbers that don’t make sense to me are the low rpm estimates for the LT6 / LT7.

[whiteboyblues2001]

Originally Posted by Martinjlm

The only numbers that don’t make sense to me are the low rpm estimates for the LT6 / LT7.

There is no way a 5.5L N/A motor is going to make 620 lbft of torque under any current circumstances. It can only make that much with boost.

[NW-99SS]

Originally Posted by whiteboyblues2001

There is no way a 5.5L N/A motor is going to make 620 lbft of torque under any current circumstances. It can only make that much with boost.

[BlaqWhole]

So basically, aside from "it revs high", a DOHC engine has no advantage.