FRPP 3V ported heads plus Comp Cams Stage 3 Cams

[90GT]

Article in the May 5.0 Mustangs and Super Fords magazine. Car made 350 rwhp but had a peak loss of 24 ft lbs of torque. I'll let the dyno graph speak for itself.

 

 

[Alloy Dave]

Article in the May 5.0 Mustangs and Super Fords magazine. Car made 350 rwhp but had a peak loss of 24 ft lbs of torque. I'll let the dyno graph speak for itself.

Ouch, I don't think I'd want that setup.

[Joe G]

Article in the May 5.0 Mustangs and Super Fords magazine. Car made 350 rwhp but had a peak loss of 24 ft lbs of torque. I'll let the dyno graph speak for itself.

No, PEAK torque went from almost 319 @ 4400rpm to almost 328 @ 5100rpm. That's not a loss, it's a gain and a move up the RPM scale to where peak hits. In fact, at 4400rpm, both stock and the head/cam combo make nearly the same torque.

[KobraII]

So the low end torque took a loss, but instead it moved it higher into the RPM range. Gotta remember Mod motors love to be turned

[90GT]

No, PEAK torque went from almost 319 @ 4400rpm to almost 328 @ 5100rpm. That's not a loss, it's a gain and a move up the RPM scale to where peak hits. In fact, at 4400rpm, both stock and the head/cam combo make nearly the same torque.

 

 

At 3000 rpm the baseline set up made 281 ft lbs of torque, at the same rpm the head and cam combo only made 262 ft lbs. That's a 19 ft lb loss that you will definitely feel in the seat of your pants.

[Joe G]

At 3000 rpm the baseline set up made 281 ft lbs of torque, at the same rpm the head and cam combo only made 262 ft lbs. That's a 19 ft lb loss that you will definitely feel in the seat of your pants.

True. But your original post was about "peak" numbers. Stock peak was at 4400rpm - here the stock and mod motor had nearly the same torque numbers.

 

Now HP... that's different. Better cams usually raise HP in the higher rpm range.

 

Personally, I like good low end torque to get me off the line rather than high rpm HP. I'm rarely racing at 6000 rpm, but always want to get off the line with more "umph"!

[ratnacage]

At 3000 rpm the baseline set up made 281 ft lbs of torque, at the same rpm the head and cam combo only made 262 ft lbs. That's a 19 ft lb loss that you will definitely feel in the seat of your pants.

 

That's why you don't run a combo like that with 3.31 gears.

[FordEvangelist]

That's why you don't run a combo like that with 3.31 gears.

 

 

I'd go with a blower.

[90GT]

I'm a torque junky so power loss in the low rpm ranges is not some thing I want. A blower would be the easy way to do it but I want to stay NA. There's just some thing about the sound of a properly tuned cammed V8. :happy feet: :happy feet: :happy feet:

[RUFDRAFT]

4:10's Rock.

[ratnacage]

There's just some thing about the sound of a properly tuned cammed V8. :happy feet: :happy feet: :happy feet:

 

Speaking of which, did I mention my car is going back on the dyno Friday? yum, yum. I'll be making a good quality video too.

[moabman]

Dyno Joe?

[ratnacage]

Dyno Joe?

 

Dyno Nick! :hyper:

[90GT]

Speaking of which, did I mention my car is going back on the dyno Friday? yum, yum. I'll be making a good quality video too.

 

 

 

 

Cool, can't wait to see what kind of numbers you put down!!!

[ratnacage]

I've been doing some homework and research for everyone thinking about a cam, heads, both, or nothing at all. What are the advantages of each? Disadvantages? What's so important about gear selection?

 

90GT correctly points out that the larger cam will decrease low end torque, however, was it just the package featured in June's 5.0 magazine, or is there a cam out there that gives you both higher and lower end increases in torque? To answer that question I cmpiled several dyno's; a stock Mustang GT (all cars are manual), the Sutton High Performance baseline Dyno, and my own car's dyno. The stock dyno is self explainatory. I chose the Sutton baseline because that setup has what many people do to their car (CAI, full exhaust, tune, and maybe a handful of other moderate mods), I also used my car since it has basically everything the Sutton baseline setup has plus cams (I don't have my most recent dyno sheet which posted slightly better numbers, but the one indicated will serve my purpose here). This gives a pretty broad view of results for typical NA mods. One other note: you'll probably be wondering why I graphed these with odd rpm points. The one dyno sheet I had plotted against mph not rpm, so I had to do a little backwards engineering (yeah, I know, wtf?, get over it)

 

But, before going any further I want to explain a few things for those that may not know. Horsepower is a function of Torque, not the other way around. In other words, you can’t have HP without torque, but you can have torque without HP. HP is what you get when you have torque AND motion (RPM). Also, when you look at a torque curve, you also get a pretty good idea of relative volumetric efficiency (VE) of the engine – VE is basically how effectively the engine is using its displacement. In other words, if your engine displaces 4.6L, VE would measure how much actual air is getting in – are you pumping more or less than 4.6L air (at std temp and pressure). For comparison, forced induction will often yield greater than 100% VE because your pushing more than 4.6L at std temp and pressure. A NA motor will typically be much less, say 75%. Where the torque curve peaks is where you are maximizing VE – this is a relative measure; just because the torque curve peaks doesn’t mean you have 100% VE, it just means that’s where VE is highest, whatever the actual value is. At peak VE your engine is theoretically at its peak efficiency. That doesn’t mean that’s where you get the best mpg, but that’s just where you are getting the most from the process.

 

The comparison between the stock and base line Sutton dyno’s gives a good idea of what happens when you do typical mods – not much to explain. The mechanics between both engines are essentially the same, but one is just moving more air, fuel, and with tuning, is getting more combustion. Notice the profile of the respective HP and TQ curves have basically the same shape, just one is higher than the other (you can’t see the stock torque curve very well – sorry, but if you look very close, it’s there. In any case, you should know what it looks like blindfolded by now).

 

Where you can really see a change in engine characteristics is the second set of curves showing my car compared to the Sutton base line. The primary difference is the cams. You’ll notice that changing the cams changes the shape of the torque curve. If you look, you can see where the Sutton torque curve crosses mine, and it looks like you could pivot the two curves around each other at that point. To the left, my torque is lower, but to the right, my torque is higher. So what gives? Why with a big bad cam did I lose torque below about 5000 rpm? It’s all about physics and fluid dynamics. As valves open, air accelerates into the cylinder. The air velocity is part of what helps fill the cylinder. At lower rpm, having a higher air velocity helps to quickly fill the cylinder before the valve shuts. However, the engineering that goes into maintaining a higher velocity at low rpm is exactly what hurts the ability to fill the cylinder at higher rpm. The stock cams open with a profile and lift that keeps velocity up at low rpm, but at higher rpm this higher velocity is not enough to overcome the relatively small lift and shorter time span available to fill the cylinder. So your VE is pretty good down low, but up high you’re simply not making good use of the displacement (relatively speaking), your VE drops which is reflected in the precipitous drop-off in torque (Ruf, I want bonus points for using “precipitous” in a sentence).

 

Change the cams, all else being equal, and you change the torque profile. My cams open the intake valves further than stock (obviously). What this does is lower the velocity of the air filling the cylinders. At a given rpm, the cross-sectional area of flow is larger with the bigger cam, thus the speed of the air decreases (the cam makes a bigger hole in the pipe, thus the air flowing through it slows down). At lower rpm, you don’t get the benefit of the fill effect you get from higher velocities, so VE is relatively lower, thus torque is also lower. However, at higher rpm, the fact that your valves are opening further allows the cylinders to fill better – the lower velocity is overcome by the fact that more air is able to enter the cylinder (because the hole is bigger). So, your VE is much better at the higher rpm than stock, thus your torque curve is much better at the higher rpm.

 

So, if you’re considering changing the cams, you must understand that you will lose torque in the lower rpm range (again, assuming all else is equal). There’s no way around that that I’m aware of.

 

So what about gear selection? The gear selection is, by and large, going to determine what rpm range you spend the most time in. You’ll notice that Comp Cams and others recommend a higher gear ratio with the more aggressive cams. Since you have lower torque in the lower rpm range it stands to reason that you don’t want to spend much time in that range if you’re trying to win a race. By going with a higher ratio you will be spending more time in the higher rpm range where you’re producing more torque. Use a 3.31 axle with a monster cam, and you’ll be very disappointed as with each shift you drop back into the less optimal torque range. I indicated with colored bars next to each chart where each shift lands you in the rpm/torque range. This will vary depending on tire and wheel size and of course the gear ratio (Remember, the wheel/tire size is every bit as important as gear ratio). Notice that while my torque is less in the lower rpm range, this fact is irrelevant because when I’m racing, I spend virtually all my time in the higher range where I’m producing the higher torque.

 

So this is my take on it. As always, if you disagree or I’m wrong about anything, I welcome your opinion/correction.

 

discuss....

 

[jcain]

Some people have way too much time on their hands!

[moabman]

I, for one, am glad that you had the time to do this! Great work Rat. I am also glad that I put the 3.73 gears in. I wonder if you could get a cam design that would trade a little of the ultimate high for an extended pivot point down to say 3500 rpm? Are you staying around 5000 after shifts? That seems like a pretty narrow RPM range. Did you sneak around and put a six speed in?

[RUFDRAFT]

My butt meter tells me that my engine has a four-barrel!

 

At about 4k, it feels like the secondaries open up!

 

Woo Hoo. :hyper:

[90GT]

I, for one, am glad that you had the time to do this! Great work Rat. I am also glad that I put the 3.73 gears in. I wonder if you could get a cam design that would trade a little of the ultimate high for an extended pivot point down to say 3500 rpm? Are you staying around 5000 after shifts? That seems like a pretty narrow RPM range. Did you sneak around and put a six speed in?

 

 

Moab,

 

 

You can get different cam grinds, that's why I'm going with the Crower stage 2 cam. It trades off a little of the high end power for more meat in the mid range. Comp Cams also has three different stages to choose from.

[moabman]

Or I could have just been "evangelized" by fordevangelist

 

Oh Mr. Whipple.......

[ratnacage]

My butt meter tells me that my engine has a four-barrel!

 

At about 4k, it feels like the secondaries open up!

 

Woo Hoo. :hyper:

 

YES!! I've actually been meaning to ask you about that. So it's not just me then.

 

Moab: the shift pattern is actually like the colored bars indicate - if I were truely hard core -super, double-secret hard core, I'd probably be better off with 4.30's given my rear tire/wheel combo. But, I still have to drive it every day, so I have to draw the line somewhere.

[Secondo]

My butt meter tells me that my engine has a four-barrel!

 

At about 4k, it feels like the secondaries open up!

 

Woo Hoo. :hyper:

That's the GT computer 'opening up' the variable valve timing

[C0braFan]

Very informative, thanks 90GT and Rat.

 

I think it's helpful to put these numbers into perspective, to look at the big picture. 350 rwhp is approximately 400 net, the figure that really counts, and 320 rwtq is approximately 370 lb/ft at the flywheel.

 

Compare these numbers with a Dodge 6.1L Hemi, with 425 net and 420 lb/ft, from a 370 cube engine! That hp figure is at 6,200 rpm, while the tq is at 4800. Now that's where you'll really see huge torque gains, due to bigger displacement.

 

But look at this little 281 3V, cranking out numbers that are comparable. The difference is that in the Mustang, you have to run at about 1000 rpm higher than the Charger. (with the Comp xtreme3 cams, etc).

 

I did some research last year and found that there is negligible benefit to the CNC-ported heads. The dyno numbers prove it, but what you don't see in the 5.0 article is a dyno with the new cams without the ported heads...what you'd find is nearly the same increases without the ported heads as with them (only about 10 hp). Considering the cams and hardware only run about $900, and the heads are something like $3000, it makes absolutely no sense to go with the ported heads.... The cost for the cams is about $22/hp, while the heads are $300/hp. The price/performance ratio is a no-brainer.

 

My goal is 400 at the flywheel, or 350 rwhp, N/A. When I install the cams, I'll be into this engine for about $1900, and I will be happy with 370 lb/ft. Contrast that with your average $5000 blower...and you'll see better torque, slightly better hp, but you have tons of heat to deal with too. My point of view is this: at currently about 300 rwhp, acceleration feels great. But I'd like to get it up another 50, and would be satisfied with that.

 

One last point I'd like to make.... Rat, you are running long-tubes. If you want to increase low-end torque, shorty headers w/x-pipe would be better, while achieving roughly the same hp.

[ratnacage]

One last point I'd like to make.... Rat, you are running long-tubes. If you want to increase low-end torque, shorty headers w/x-pipe would be better, while achieving roughly the same hp.

 

The only problem with that is shorties will cause areduction in high-end torque compared to long tubes. With a 4.10 gear and a valve train that likes to rev, I'm better off overall with the long tubes. If I'm racing (which is when the power really counts), my engine basically spends all its time above 4000 rpm, so looking for gains in low end torque won't do much for me. If I didn't have cams and a 4.10 gear, then shorties might be the way to go, although from what I've heard, the stock manifolds are pretty efficient, so I'm not sure the money spent on shorties would be worth while from a bang/buck standpoint.

[moabman]

I've got the shorty headers and I'm looking for low end torque. Don't have cams or heads yet but I might consider them both after the blower. Ported heads are a nice compliment to a supercharger and they do help a little with the heat issues. I am going with the Whipple which is one of the most thermally efficient blower designs and even though I will be restricting the boost to about 7 psi with a larger pulley, I'm going to put the I/C in. I have 3.73s and am going to put a super torque TC in with good lock up characteristics. Not the most cost effective set up, but oh-mama :happy feet:

[C0braFan]

The only problem with that is shorties will cause areduction in high-end torque compared to long tubes. With a 4.10 gear and a valve train that likes to rev, I'm better off overall with the long tubes.

 

What would lead you to that belief? It is not evident in your dyno sheets. All you saw was an increase of 2-4 lb/ft over the baseline. I think that is a result of the long tubes, in which case a loss of backpressure is actually reducing the potential power gains. The 4.6L is not a big block engine; it doesn't benefit from huge exhaust, it needs backpressure.

 

If I'm racing (which is when the power really counts), my engine basically spends all its time above 4000 rpm, so looking for gains in low end torque won't do much for me.

 

Even a stock 4.6L 3V will spend "all it's time above 4000 rpm" because it reaches 300 hp at 6100 rpm, and max torque above 4000 as well. Not a compelling argument.

 

If I didn't have cams and a 4.10 gear, then shorties might be the way to go, although from what I've heard, the stock manifolds are pretty efficient, so I'm not sure the money spent on shorties would be worth while from a bang/buck standpoint.

 

Shorties with equal length tubes will definitely see a power gain over stock, regardless of the ring/pinion. Long tubes aren't necessarily giving you extra power, high or low, but they definitely hurt the torque curve!

 

Ahhh, I need to get a dyno done. As soon as I get the BBK shorties and x-pipe installed, I'll do it and report here on the result. I'm expecting around 320 rwhp without cams.

[ratnacage]

What would lead you to that belief? It is not evident in your dyno sheets. All you saw was an increase of 2-4 lb/ft over the baseline. I think that is a result of the long tubes, in which case a loss of backpressure is actually reducing the potential power gains. The 4.6L is not a big block engine; it doesn't benefit from huge exhaust, it needs backpressure.

Actually, I haven't kept this thread updated like I should have. Since that data (April 07), additional tuning has been done which has increased peak tq to 322. Pk HP increased to 342 from 341 - not much there, but the real story is not in the peak values, but in the shape of the curve.....

 

Even a stock 4.6L 3V will spend "all it's time above 4000 rpm" because it reaches 300 hp at 6100 rpm, and max torque above 4000 as well. Not a compelling argument.

...here is a more compelling argument.... In stock configuration pk TQ arrives at just over 4000 rpm (around 285 lb-ft). For simplicity, lets look at what happens in 3rd gear with a 3.55 axle: upon shifting to 3rd, rpm drops to 4000 rpm with tq around 282. At this point, tq is just below pk, then headed down towards 230 @ 6000. This means that for the virtually all of 3rd gear, a stock Mustang's rate of acceleration is decreasing. Without regard to the axle ratio, at 4000 rpm, my engine still has not reached its peak tq - this comes around 5300 rpm, thus my rate of acceleration is still increasing at the shift. From 5300 rpm, tq drops to 297 at 6000. So between 4000 rpm and 6000 rpm, in stock form there is net change in tq of -52 lb-ft (282@4000 vs 230@6000), while my car experiences a net change of +2 lb-ft (295@4000 vs 297@6000). This is an absolute difference in change of tq of 54 lb-ft bewteen the two configurations. This is huge and is why you can't just focus on pk values. The shape of the curve is what ultimately determines your overall performance in acceleration. Peak values are great for bragging on Saturday nights, but the proof will be in how the cars accelerate and by how much one beats the other.

 

Now, in the real world with my actual configuration (4.10 axle, 295/45/18's), I'll actually shift out of 3rd at 6250 rpm which will land me at 4700 rpm in 4th. I'll then finish the 1/4 mile at about 5500 rpm in 4th (roughly 110 mph). Between 4700 and 5500, my net change in tq is +3 lb-ft (312@4700 vs 315@5500).

 

So the long and short of it is that while the difference between peak values isn't that dramatic, the difference between the shapes of the curves are. While I'm open to your theory that my overall performance would improve with shorties, I am skeptical only because I wonder, with cams, if shorties wouldn't provide too much back pressure given the much greater volume of exhaust that needs to flow. I'm sure you're correct if we take the cams out of the equation, but I would be very surprised if going to shorties gave me better 1/4 mile performance (with cams).

 

This is a facinating debate - let's keep it going!!

[slidemaster]

I, for one, am glad that you had the time to do this! Great work Rat. I am also glad that I put the 3.73 gears in. I wonder if you could get a cam design that would trade a little of the ultimate high for an extended pivot point down to say 3500 rpm? Are you staying around 5000 after shifts? That seems like a pretty narrow RPM range. Did you sneak around and put a six speed in?

 

 

We have a "Street Class" 06 time attack Mustang with a stroker (5.1) and said cam with CNC ported stock heads. After break in and multiple dyno tune runs it ended up with 395rwp and we went out and won the street class in the 1st attempt.

 

For more info

www.barberdrivingexperience.com and go to the media page and pull Modified Mustangs article "winners dont quit" part 1 and 2

 

For our application (road course) we use the 3:55 axle as the 3:73 or 4:10 dont give us enough top end in 4th gear

[ratnacage]

With CMCV delete plates and no additional tuning I'm up to 350 rwhp and 329 tq.

[2006GT500]

I have the stage 4 comp cams and have really enjoyed the added performance they have given my car.