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I'm unsure about where the Vulcan-powered Tauruses are programmed to shift out of 1st gear and what is "safe" for the engine....

I know the Duratecs can get up past 6... but where are Vulcans supposed to shift?

I have a 2002 Sable Vulcan that never goes more than exactly 5k with the pedal to the medal, whereas my 2000 Sable Vulcan does about 5200 in 1st and then almost 5500 in 2nd if you hold it down.

That said, the 2002 has both stock engine and transmission at 160k and the 2002 has a rebuilt engine and transmission at 44k (244k on the car).

Is 5500 too fast for the Vulcan? What is the maximum RPM supposed to be?

Thanks!
 

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that sounds about right, mine does the same. It upshifts at 5k with OD on and 5.5k with normal D (you can actually max out the car in 3rd gear at 5500 that way). 5500 is safe, but people say valvesprings start to go at 5800.

Here is a quote from rogueperfomance.com:
"If you rev over 5,500 RPM's regularly, invest in a quality set of double valvesprings. If you have rev'ed over 5,800 RPM's on factory single springs, replace them now!"

Link to the page:
Vulcan Potential
 

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Yeah, vulcan doesn't like to go much over 5000 RPM. There's no power past that point anyway so not much point of revving it up past that.
 

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Sort of out of topic but I don't want to start a new thread.

What is the lowest RPM to shift in a Duratec? If I let it, it will shift at around 2,100 RPM. Is that too low or ok?
 

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There's no minimum RPM for shifting as long as the engine doesn't bog down too much after the gear change. 2100 RPM is normal if you're accelerating slowly.
 

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OHV/Pushrod motors loose all power above a certain RPM so thats why it shifts down lower than the Duratec. DOHC motors have peak power throughout the curve. Although in my 2000 I felt like when going about 55mph if you floor it and it downshifts to second it revs up 5500-6500rpm and then when it shifts to 3rd gear you feel like you take off! Its like the torque drops out at those higher RPMs and you loose the oomph even though you are hitting peak HP.

The 2008 doesn't do that. It has power through the rev range and usually shifts at 6000, however sometimes will go higher or lower depending on several circumstances. Its the same way with the vulcan. When you go WOT, the PCM takes in a lot of readings and decides exactly when it should shift.
 

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OHV/Pushrod motors loose all power above a certain RPM........

All engines loose power above a certain RPM. That RPM is determined by many factors.... intake design and flow, the cam installed in the engine and many more factors. There are many high performance SBC and SBF pushrod motors out there that are making max HP well over 6000 RPM.

DOHC motors have peak power throughout the curve.....

No. Peak power is peak power, and occurs at a specific RPM for all engines depending on the factors noted above. 4 valve motors typically breathe better than 2 valve motors (in most cases) at higher RPM, and the cam is designed to take advantage of this. It all comes down to volumetric efficiency (VE). Typically pushrod motors have max VE at lower RPM than DOHC motors do. For ALL engines, max VE corresponds to max torque, and also best BSFC.

Remember HP(in HP) = Torque(in lbft)xRPM/5252.
 

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Most dont know its equal @ 5252 all mods do is shape the curve higher or lower of that point

Ive tried explaining that to alot of people they cant wrap there closed mind around the fact that hp is created by torque and the paths [email protected] 5252 thats when you know they know nothing and to not bother with them anymore

Also hp and torque are very close to the same or equal at 5252 another thing people cant understand
 

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^^^^ to add to what you said, the only MEASURED quantity (for that matter the only "real" quantity) for all engines is torque. Horsepower is a calculated quantity. Big horsepower numbers sell cars, big torque wins races.
 

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While the above two posts are entirely true lets not get ahead of ourselves and suggest that OHV and DHOC are different methods to get the same result. While the two different engine architectures are characterized by different peak HP/torque points; they are not equals. DOHC is superior to OHV in terms of power output, and mpg.


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Pay attention
Torque and hp of any enigine cross paths on a dyno sheet at 5252 rpms that is because torque x rpm = hp/5252 clearly you do not understand this or you would not have posted what you just did

it cant be stated more clear then that

The only thing stated of being equal is torgue and hp and 5252 rpms

On some very high output engines mostly boosted engines the ve can get above 100% and the rpm at which point the torque and hp cross on the dyno sheet will be off slightly otherwise its just a math formula just like 2+2=4 it might only be 3.9999 if you put synthertic in

Popcorn shelia?

Power and Torque: Understanding the Relationship Between the Two, by EPI Inc.
 

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I was in no way saying that you said push rods and DOHC are equivalent. But I wanted to prevent other people from being mislead because the way you presented what you and Jeff K said it could be interpreted as saying that OHV and DOHC are equivalent.


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While the above two posts are entirely true lets not get ahead of ourselves and suggest that OHV and DHOC are different methods to get the same result. While the two different engine architectures are characterized by different peak HP/torque points; they are not equals. DOHC is superior to OHV in terms of power output, and mpg.


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I'd like to hear how DOHC is superior in terms of power and MPG.
 

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I'd like to hear how DOHC is superior in terms of power and MPG.
What? It has 50 more HP.

Now MPG wise the Vulcan wins. EPA estimated is the same, but in the real world I personally believe it wins. Think about it.... (this is theoretical) DOHC has 4 valves per cylinder. More air can be sucked in and burned (meaning more gas will be injected into the cylinder to burn the extra O2). That creates more power. However lower MPG. The differences aren't that much though.

Look at the facts. Duratec makes 200hp/200tq, the vulcan does not. Duratec maintains peak power through the rev range to redline (6500rpm), the vulcan does not. What more is there to say?

DOHC is able to make more power than a pushrod motor because its able to suck in more air!
 

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What? It has 50 more HP.

Now MPG wise the Vulcan wins. EPA estimated is the same, but in the real world I personally believe it wins. Think about it.... (this is theoretical) DOHC has 4 valves per cylinder. More air can be sucked in and burned (meaning more gas will be injected into the cylinder to burn the extra O2). That creates more power. However lower MPG. The differences aren't that much though.

Look at the facts. Duratec makes 200hp/200tq, the vulcan does not. Duratec maintains peak power through the rev range to redline (6500rpm), the vulcan does not. What more is there to say?

DOHC is able to make more power than a pushrod motor because its able to suck in more air!
So you're comparing and engine that was already 10 years old to an engine to an engine that was brand new? Look at the RAM 1500 that gets 16/22 or the Silverado that gets the same. The F-150 is 15/21. Both have similar or more power than Ford's 5.0. Or look at the Camaro and Mustang. The Camaro has slightly more power and similar fuel economy to the Mustang.
 

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High output engines in exotics are overhead cam designs. Nascar is pushrod and carb driven due to rules. If they had OHC designs, the cars would be absolutely ridiculous.

Disadvantages of OHV

  • Limited engine speeds or RPM: OHV engines have more valvetrain moving parts, thus more valvetrain inertia and mass, as a result they suffer more easily from valve "float", and may exhibit a tendency for the pushrods, if improperly designed, to flex or snap at high engine speeds. Therefore, OHV engine designs cannot revolve ("rev") at engine speeds as high as OHC[1] Modern OHV engines are usually limited to about 6,000 to 8,000 revolutions per minute (rpm) in production cars, and 9,000 rpm to 10,500 rpm in racing applications. In contrast, many modern DOHC engines may have rev limits from 6,000 rpm to 9,000 rpm in road car engines, and in excess of 20,000 rpm (though now limited to 18,000 rpm) in current Formula One race engines using pneumatic valve springs. High-revving pushrod engines are normally solid (mechanical) lifter designs, flat and roller. In 1969, Chevrolet offered a Corvette and a Camaro model with a solid lifter cam pushrod V8 (the ZL-1) that could rev to 8,000 rpm. The Volvo B18 and B20 engines can rev to more than 7,000 rpm with their solid lifter camshaft. However, the LS7 of the C6 Corvette Z06 is the first production hydraulic roller cam pushrod engine to have a redline of 7,100 rpm. The Honda CX500 motorcycle engine has a 9750rpm redline, well above the usual limits for auto engines, due to the lighter weight of components.
  • Limited cylinder head design flexibility: overhead camshaft (OHC) engines benefit substantially from the ability to use multiple valves per cylinder, as well as much greater freedom of component placement, and intake and exhaust port geometry. Most modern OHV engines have two valves per cylinder, while many OHC engines can have three, four or even five valves per cylinder to achieve greater power. Though multi-valve OHV engines exist, their use is somewhat limited due to their complexity and is mostly restricted to low- and medium-speed diesel engines, with a few notable exceptions such as the four valve per cylinder Honda CX500 motorcycle. In OHV engines, the size and shape of the intake ports as well as the position of the valves are limited by the pushrods and the need to accommodate them in the head casting.
  • Noise and Refinement: OHV engines are generally noisier than their OHC counterparts owing to the increased complexity of the valvetrain and the adoption of chain or gear based camshaft drive.
  • Maintenance: The location of the camshaft in the cylinder block often necessitates removal of the engine whenever camshaft work is required. This is particularly true for front wheel drive applications with a transversely mounted engine. Longditudinally mounted OHV engines suffer less from this problem as the camshaft can be withdrawn from the front of the engine after removal of the radiator.
 

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Peak hp is rated @ 6000 rpm peak torque is rated @ 4850
I bet on a dyno it would be under 6k

It does not maintain it to 6500 it will be less at 6500 then it will be @6k if that is the peak

the rest is just a torque curve
 

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......extra butter, lol.
Yeah load that way up with butter. Goooood stuff. Gonna gain some weight with all this popcorn!

Not sure why mr 1998 is standing so hardcore behind the pushrods, but DOHC is the way of modern motors and there are good reasons for it.
 
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