GT500 vs...

[Erik427]

If both engines made the same power that would be irrelevant.


Zoomies? Seriously?

No, the same power and the FPC would still have the advantage. You can have two motors that are the same size. Same rpm spread. Same hp/tq. Only difference is one is a FPC and the other a CPC. The FPC will rev faster because it breaths easier. Zoomies on a CPC motor fixes the exhaust pulse issue. Just can't run that on the street.

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[Grimace427]

No, the same power and the FPC would still have the advantage. You can have two motors that are the same size. Same rpm spread. Same hp/tq. Only difference is one is a FPC and the other a CPC. The FPC will rev faster because it breaths easier. Zoomies on a CPC motor fixes the exhaust pulse issue. Just can't run that on the street.

FPC revs easier due to the reduction in rotating mass. Has nothing to do with VE.

 

[flaps]

No, the same power and the FPC would still have the advantage. You can have two motors that are the same size. Same rpm spread. Same hp/tq. Only difference is one is a FPC and the other a CPC. The FPC will rev faster because it breaths easier. Zoomies on a CPC motor fixes the exhaust pulse issue. Just can't run that on the street.

If the hp and tq curves are identical on a FPC engine and a CPC engine, the cars will go the same speed. The dyno doesn't care how the engine operates, it only measures the output. If the two cars put out the same numbers, the are accelerating the dyno at the same speed. They will accelerate the same on the street too.

A FPC typically allows an engine to rev higher and faster than a CPC because it is lighter and breathes better, which allows it to make more power. But if two engines have the exact same power/torque curves, the results will be the same.

 

[Erik427]

Let me give you guys a example that is easier to explain but derails this thread for a moment. When nascar started using restricter plates. The Ford camp started to use the 302. That motor made less power than the 351 but not by much. What it would do that the 351 could not was rev faster. The cpc has a exhaust restriction that does not allow it to rev up as fast. The firing order and related exhaust pulse is/are the culprits. This is only a factor when a shared exhaust collector is used per bank. Some say the intake suffers the same deal but not nearly as bad. These are the reasons why Ford chose the FPC over a conventional 5.2 engine. This is something that needs to be seen to understand. The cpc 5.2 would/will make more bottom end tq. One supports topend HP. The other supports bottom end tq.

 

[Erik427]

If the hp and tq curves are identical on a FPC engine and a CPC engine, the cars will go the same speed. The dyno doesn't care how the engine operates, it only measures the output. If the two cars put out the same numbers, the are accelerating the dyno at the same speed. They will accelerate the same on the street too.

A FPC typically allows an engine to rev higher and faster than a CPC because it is lighter and breathes better, which allows it to make more power. But if two engines have the exact same power/torque curves, the results will be the same.

If everything was the same. Valve lift, compression, itake/exhaust cfm and displacement? The two motors will have very different power bands. FPC vs CPC are very different.

 

[Trackaholic]

Let me give you guys a example that is easier to explain but derails this thread for a moment. When nascar started using restricter plates. The Ford camp started to use the 302. That motor made less power than the 351 but not by much. What it would do that the 351 could not was rev faster. The cpc has a exhaust restriction that does not allow it to rev up as fast. The firing order and related exhaust pulse is/are the culprits. This is only a factor when a shared exhaust collector is used per bank. Some say the intake suffers the same deal but not nearly as bad. These are the reasons why Ford chose the FPC over a conventional 5.2 engine. This is something that needs to be seen to understand. The cpc 5.2 would/will make more bottom end tq. One supports topend HP. The other supports bottom end tq.

I think the main reason FPC revs more freely is due to the reduced inertia afforded by smaller counterweights (as Grimace noted).

The effect of the exhaust pulses is that for a given set of parameters (displacement, valve lift, etc), you can have more engine efficiency and therefore more torque and power.

The example with the 351 changing to a 302 is confusing because I thought they were both CPC designs. Therefore, the improvements in performance on the 302 was likely due to the smaller engine having less mass/inertia, rather than due to a breathing advantage.

I guess we are all in agreement that the FPC revs more freely, but maybe we haven't achieved unanimous reason as to why.

-T

 

[Twin Turbo]

Now this is how it should be done. Great discussion, guys. It's nice to see differing opinions being aired on a forum without resorting to name-calling and childish behavior :cheers:

 

[Erik427]

I think the main reason FPC revs more freely is due to the reduced inertia afforded by smaller counterweights (as Grimace noted).

The effect of the exhaust pulses is that for a given set of parameters (displacement, valve lift, etc), you can have more engine efficiency and therefore more torque and power.

The example with the 351 changing to a 302 is confusing because I thought they were both CPC designs. Therefore, the improvements in performance on the 302 was likely due to the smaller engine having less mass/inertia, rather than due to a breathing advantage.

I guess we are all in agreement that the FPC revs more freely, but maybe we haven't achieved unanimous reason as to why.

-T

My point with the 302 vs 351 is that the 302 breaths more freely. Yes they are both cpc motors. I used them as a example on how two motors can produce different results even though the lesser motor made a tad less power. The lesser motor in fact performed so much better that nascar banned it forever. This breathing more freely was what I was try to convey when it comes to a fpc vs cpc comparo. They both have their respected merits.........

 

[Erik427]

Now this is how it should be done. Great discussion, guys. It's nice to see differing opinions being aired on a forum without resorting to name-calling and childish behavior :cheers:

We all agree....

 

[Strokerswild]

The example with the 351 changing to a 302 is confusing because I thought they were both CPC designs. Therefore, the improvements in performance on the 302 was likely due to the smaller engine having less mass/inertia, rather than due to a breathing advantage.

In the Ford 302/351 scenario the 302 has a much shorter stroke, which means less rotating mass, and also less piston speed at a given RPM. Which all makes for a freer-revving engine. Big bore + short stroke = screamer.

If the cylinder heads are equal and move air beyond the airflow requirements of either engine (no restriction), either engine will only use whatever it can pull out of them, which is where camshaft timing becomes critical to maximize volumetric efficiency of the package.

The FPC revs quicker mainly due to less (a lot less) rotating mass. It also contributes to an alternate (bank to bank) firing order, which allows better exhaust scavenging since an adjacent cylinder in the same bank isn't firing and fouling the exhaust tract right before another does.

 

[flaps]

If everything was the same. Valve lift, compression, itake/exhaust cfm and displacement? The two motors will have very different power bands. FPC vs CPC are very different.

I agree with you there, but before it was said if they have the same torque and hp the FPC would be faster, which is not right, unless the FPC has more area under the curve. But if their torque curves are the same, the results will be the same. But I agree that if they both have the same valve lift, compression, itake/exhaust cfm, and displacement, etc., the FPC would probably be faster because of the lower rotating mass and better breathing.

 

[Erik427]

In the Ford 302/351 scenario the 302 has a much shorter stroke, which means less rotating mass, and also less piston speed at a given RPM. Which all makes for a freer-revving engine. Big bore + short stroke = screamer.

If the cylinder heads are equal and move air beyond the airflow requirements of either engine (no restriction), either engine will only use whatever it can pull out of them, which is where camshaft timing becomes critical to maximize volumetric efficiency of the package.

The FPC revs quicker mainly due to less (a lot less) rotating mass. It also contributes to an alternate (bank to bank) firing order, which allows better exhaust scavenging since an adjacent cylinder in the same bank isn't firing and fouling the exhaust tract right before another does.

The 302 was able to spin up more freely because it is not hurt as bad as the 351 by the mandated restrictor plate. Logic suggested at the time that the long stroke 351 would have stole the day. The lesser hp was the clear winner because it was able to get to all of it's power even though it was much less. This is the same theory with the fpc vs cpc. With all things equal....the fpc will win each time. But cost and reliability are factors that favor a cpc and so does bottom end tq. The myth that the fpc always has less mass is just a myth. The rods and rod journals still must be balanced, often requiring the use of "heavy" metal. The most famous is mallory. The cpc's exhaust pulse can be fixed with the runners "headers" running from one bank of cylinders to the other. Thus correcting the firing order as far as the exhaust is concerned. SIDE NOTE.....intakes normally don't swap well unless the intake runners are separate "no shared plenum".......Like I said, it's kinda hard to explain. I need to be able to put parts and pieces in your hands to show you more properly. I Love the Different Opinions.:cheers:

 

[Strokerswild]

I wasn't talking restrictor plates in my scenario, that's another ballgame altogether....and well aware of heavy metal balancing and 'bundle of snakes' headers.

:cheers:

(Been building engines for 30 years in my free time..... ;) )

 

[thePill]

There is no way for Ford to increase the bore over 94mm of the Voodoo. That is as far as they can push it. The bore spacing is only 100mm. Also, I think the stroke is as far as they can push it too. The Coyote/Voodoo have the same deck height (227mm) as the old 4.6L, which only had a stroke of 90mm. The 5.4/5.8L had a higher deck height (256mm) which allowed for its longer stroke of 105.8mm.

Also, there is no way Ford is building a single turbo V8, especially alongside a twin turbo V8. It's just not going to happen. A single turbo would cause the exhaust manifolds to be way too long meaning the catalytic converter would be too far away. No way it could pass emissions. It would also cause more turbo lag and a higher boost threshold, which would not be acceptable in a street car.

Either a twin turbo or a supercharger is the only way they're going. And the engine is not going to be any bigger than 5.2L (and it doesn't need to be, they're already getting ~650hp out of a 3.5L). Hopefully they go with a twin turbo setup to differentiate it from the Camaro and older Mustangs.

I doubt the bore would ever be over 94mm as well, this is all for a hypothetical 5.5 Coyote. If it's forced induction, I'd rather go the Trinity route and use a long stroke. I'd feel better with a 5.0 bore on a Turbo/Twin Turbo application for my dream engine, 5.5 liter V8.

If we do see a "Voodoo Child" 5.0 FPC, we would get a 94mm bore with an 89mm stroke. That's nearly 3mm shorter than the Voodoo... That should see a 9250rpm redline. The 94mm bore had enough to push the 92.7mm stroke to 8250 AND, as they said, it makes 526hp from 7500rpm up to redline. Would you be willing to sacrifice a little peak power to extend your powerband another 1000rpm's?

Just think, once Direct-Port Injection is added, any peak power lost would be regained and then some. It would give them the opportunity to eliminate the gas guzzler tax, increase output and extend its already tremendous powerband.

I mentioned this before but, I would prefer the bore come back down to Coyote levels and have the cooling passage size increased. Maybe a 4.5 or a 4.7 (289) someday...

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