2V Power Curve / Tradeoffs

[CuddaWuddaShuda]

I was comparing power / torque peaks for some cars, and it occured to me that in many ways the 260HP GT is a real oddball. For example, it makes a much bigger torque number than its power number (302 vs. 260), but at the same time its power curve is at fairly high RPM. I really do not consider it a very responsive motor below 3000 RPM, despite the big torque number. To me, the motor feels like it likes high RPM.

Now I know that the power and torque numbers use different units, and that the RPM peaks are a somewhat different issue from the power/torque tradeoff. Throttle response is its own issue, also. At the same time, though, it seems like there are some general trends that the 260HP / 2V motor defies:

Usually a motor with a power peak at 5250 RPM would not exhibit the bias toward torque that the 260HP motor does. For example, the most common version of the LS1 reaches its torque and power peaks at 4000 RPM and 5200 RPM, respectively, almost exactly like the 260HP motor. But the power peak is 310HP and the torque peak is 340LB/FT. The numbers are closer to each other (30) than the Ford's numbers are (42).

There is another issue I have with the LS1... it seems like a smaller, OHC motor should come closer to the LS1 in power, not torque. That big LS1 should excel at torque and the OHC 4.6L should (to some extent) make it up on the top end. This is the stereotype. But the exact opposite is true... the torque peak of the 260HP motor is really pretty close to the LS1 (302 vs. 340) but the power differential is greater (260 vs. 305). In a race, the GT will do a decent job keeping up off-the-line and up to 60MPH, but the Z28 will absolutely run away on the top end. This seems backwards to me.

Looking at the intake manifold of the 4.6L motor just confuses the issue further. The runners look seriously long and narrow to me... like an effort to boost low-RPM torque and throttle response was made. But the power curve is up at high RPMs... a 4000 RPM torque peak in particular seems high for a V8. In terms of real-world experience, I can feel the motor "wake up" around 4000 RPM. It seems like Ford could have gone all-out with the power / breathing ability of the engine, instead of going for a high-torque approach that no one can really feel in the seat of their pants anyway.

Overall, I think it's pretty cool that Ford can get so much specific torque out of the Modular engines as a whole. Supposedly the new 4V, naturally aspirated motors are excellent in this respect also. It points out the fact that Ford is not blowing smoke when they say that the Modulars are low-friction devices... clearly more of the power of combustion is making its way to the drivetrain than in previous designs.

I guess my questions are:

1) Do you consider the stock GT motor a "revver" or a "torquer?"
2) How do you find the throttle response of the motor?
3) What has been done with short, wide intake runners on these engines?

Also, I will propose a theory. Ford figured they may as well use that serpentine intake, with the long coiled-up runners, since the heads are a bottleneck anyway. Short, wide intake runners would have given a very slight power boost (because of the heads) and would have killed what throttle response the engine does have.

 

[FallenPhoenix]

first of all, the numbers for the LS1 are underrated both in horsepower and in torque so that does make a difference in your comparison. Second, I'm sure Ford tuned the 4.6 in the mustang to make lots of torque because that's what people feel when they're test driving a car and horsepower is really just a mathematical representation of torque.

I think it would be very useful to have software that could easily overlay two dynographs to show the difference in torque and power curves, because that's where it's really at, peak numbers really don't mean much anyway. Very good post and some excellent questions

 

[kirkyg]

I guess my questions are:

1) Do you consider the stock GT motor a "revver" or a "torquer?"
2) How do you find the throttle response of the motor?
3) What has been done with short, wide intake runners on these engines?

Also, I will propose a theory. Ford figured they may as well use that serpentine intake, with the long coiled-up runners, since the heads are a bottleneck anyway. Short, wide intake runners would have given a very slight power boost (because of the heads) and would have killed what throttle response the engine does have.

Well it all depends on what your comparing it to. I consider it fairly healthy on torque. Now below 2000 its kinda doggish but most engines are...after about 2000 like on the freeway you can feel the pedal give you much more response once you get up to about 2000 rpms because hitting the area where you have alot more torque.

I consider the stock GT a moderate motor though in terms of torque compared to top-end. If you want to feel top end power you should drive a 4valve. Its like the your in a whole new car once you hit 3000 rpms. The truth is though the 4valve has as much torque on the bottom and way more top end so its the best of both worlds.

kirkyg

 

[DBMSTNG]

I was comparing power / torque peaks for some cars, and it occured to me that in many ways the 260HP GT is a real oddball. For example, it makes a much bigger torque number than its power number (302 vs. 260), but at the same time its power curve is at fairly high RPM. I really do not consider it a very responsive motor below 3000 RPM, despite the big torque number. To me, the motor feels like it likes high RPM.

hp is tq x rpm / 5252. so obviously your car is going to be more responsive at higher rpms unless you own a car with extremely crappy heads that would choke off power around 4000rpm .like the Dakota R/T for instance.

Usually a motor with a power peak at 5250 RPM would not exhibit the bias toward torque that the 260HP motor does.

you are totally wrong. any car engine in the world will creat equal hp and tq at 5252rpms. every single car in the world creates more tq than horsepower under 5252rpm.

For example, the most common version of the LS1 reaches its torque and power peaks at 4000 RPM and 5200 RPM, respectively, almost exactly like the 260HP motor. But the power peak is 310HP and the torque peak is 340LB/FT. The numbers are closer to each other (30) than the Ford's numbers are (42).

please go check the REAL numbers that the LS1 puts out. then look at the torque curve based on rpm. finally, use the hp equation i wrote above. it will all make sense after that.

That big LS1 should excel at torque and the OHC 4.6L should (to some extent) make it up on the top end. This is the stereotype.

um, no it's not.

But the exact opposite is true... the torque peak of the 260HP motor is really pretty close to the LS1 (302 vs. 340) but the power differential is greater (260 vs. 305). In a race, the GT will do a decent job keeping up off-the-line and up to 60MPH, but the Z28 will absolutely run away on the top end. This seems backwards to me.

not to sound like a jerk, but it's because you have no idea of what you are talking about.

Looking at the intake manifold of the 4.6L motor just confuses the issue further. The runners look seriously long and narrow to me... like an effort to boost low-RPM torque and throttle response was made. But the power curve is up at high RPMs... a 4000 RPM torque peak in particular seems high for a V8.

on a 2V engine, it's harder to make torque across the entire rpm band with a small bore and low compression. so, if you want hp, you'll need to cam the car to make more tq biased at higher rpms.

In terms of real-world experience, I can feel the motor "wake up" around 4000 RPM.

that's because that is your peak torque and it's being multiplied by rpms.

It seems like Ford could have gone all-out with the power / breathing ability of the engine, instead of going for a high-torque approach that no one can really feel in the seat of their pants anyway.

they did, it's called a 4V.

Overall, I think it's pretty cool that Ford can get so much specific torque out of the Modular engines as a whole. Supposedly the new 4V, naturally aspirated motors are excellent in this respect also. It points out the fact that Ford is not blowing smoke when they say that the Modulars are low-friction devices... clearly more of the power of combustion is making its way to the drivetrain than in previous designs.

the reason they make more power than stock 5.0Ls did is because they breathe better.

I guess my questions are:

1) Do you consider the stock GT motor a "revver" or a "torquer?"
2) How do you find the throttle response of the motor?
3) What has been done with short, wide intake runners on these engines?

1. both. it revs qick for a V8 and produces more torque than 90% of the cars on the road.

2. throttle response is great. a blip of the throttle makes my car jump.

3. they've made the 4.6L a race only engine. it causes a big loss of low end torque.

Also, I will propose a theory. Ford figured they may as well use that serpentine intake, with the long coiled-up runners, since the heads are a bottleneck anyway.

this logic is totally bassakwards. it would restrict airflow even more. more restriction = less power.

 

[Joel's98GT]

you are totally wrong. any car engine in the world will creat equal hp and tq at 5252rpms. every single car in the world creates more tq than horsepower under 5252rpm.

I agree with EVERYTHING you said brother, good post.

Highlighted this portion because It made me laugh. Basic Physics Owns him.

 

[GoBabyVroommm]

This is what i found out about any of the 4.6 motors i had 2v and 4v. If your going to race rev the crap out of it an good.

When i race with my 4v i just rev it pass 4000rpm and hit it. If i don't i usually will lose to a car that has better low to mid power range. This is assuming it runs the same times as me.

So basicly the 4.6 response a lot better when you rev the thing.

 

[DBMSTNG]

I agree with EVERYTHING you said brother, good post.

Highlighted this portion because It made me laugh. Basic Physics Owns him.

you should have read his "Lightnings suck because their top speed is 3mph slower than a GT" thread. it was hilarious.

 

[kirkyg]

This is what i found out about any of the 4.6 motors i had 2v and 4v. If your going to race rev the crap out of it an good.

When i race with my 4v i just rev it pass 4000rpm and hit it. If i don't i usually will lose to a car that has better low to mid power range. This is assuming it runs the same times as me.

So basicly the 4.6 response a lot better when you rev the thing.

Yes but your 4valve is hardly running up to par...

kirkyg

 

[CuddaWuddaShuda]

I really hate sweet pickles.

 

[GoBabyVroommm]

Yes but your 4valve is hardly running up to par...

kirkyg

YOU KNOW NOTHING ABOUT THE 4V!!!! lol J/K

 

[CuddaWuddaShuda]

DBMSTNG:

I didn't understand why you would respond to a post that was mostly technical, and did not claim to have all the answers anyway, with such an ad hominem attack. Then I saw your second post about my Lightning thread. Dude, that was months - if not years - ago. Let it go. I don't like the Lightning. I pointed out one of its flaws. Personally, I feel comfortable in my GT up to about 120 MPH. I can hold a conversation, steer with one hand, adjust my stereo, etc. at that speed. I really have to question the wisdom of going that fast in a pickup. That's all I was saying.

I don't want to pick apart everything you said, but...

You make the mistake of equating power with responsiveness. I don't think responsiveness has as much to do with power as it does with torque. Torque is twisting force. Power is energy applied to do work. Now a car with a lot of torque can really slap you in the back from a dead stop to 10 MPH. It hasn't done a lot of work (i.e. made a lot of power or moved the car very far), but it has exerted a great deal of twisting force.

One person made the same argument I am making here by suggesting an experiment: take a car to its power peak, hold it there, and then step on the gas. Then do the same at the torque peak. You will get slapped in the back much more strongly at the torque peak than at the power peak.

Taking this a step further, almost all internal combustion engines have a hill-shaped torque curve, with torque increasing to a peak and then decreasing. So they become more responsive with increasing RPM as the tach needle approaches the torque peak, then they become less responsive with increasing RPM after the peak. The general statement you make - that cars are more responsive at higher engine speed - is not correct.

Joel's98GT, I hope you will read the last three paragraphs as well. Your asinine, boot-licking post is not appreciated. At least DBMSTANG is smart enoug to provide some useful information. You're just a frickin poser.

And please don't post that I don't know what I'm talking about. I have been down the quarter mile over 80 times and I ran 13.990 in my stock 2001 GT, with the spare tire, seats, stock tires, stock filters and oil, etc., in place. I can do most basic mechanic work: brake jobs, timing belts, etc. I even converted a car from TFI to Duraspark. I never took college Physics, but I took Physical Chemistry and Calculus III, and did well in both. None of this is earth-shattering (and I don't claim to be the reincarnation of Smokey Yunick), but it's just unfair to say that I don't know what I'm talking about.

Believe it or not, I knew the horsepower / torque equation and it simply doesn't answer every single question one might raise about every single dynamometer curve that has ever been plotted. My original point was really just that the 4.6L 2V has kind of a strange torque curve. It loses 42 FT/LB over a range of 1250 RPM (between the two peaks). In this day and age, that's not commonplace. It's not that uncommon for a car to lose less than 10 FT/LB between the peaks. The Acura RSX is an example of a car with the same torque number at both peaks.

Losing 42 FT/LB between the peaks tends to indicate an engine that doesn't breathe very well, and is biased to low-end throttle response, but I don't think that's true of the 4.6L 2V. That was really the discrepancy I was trying to point out, and just get some theoretical discussion started. To me, the engine feels like it likes high RPM. I was just trying to see if others felt this way, and to reconcile this general, seat-of-the-pants impression with some hard numbers.

Beyond these technical issues, I am really bewildered by the emotion with which you responded. I know most people do not use this forum in the way I do. I tend to post broad observations and questions, with a theoretical perspective that is not typical of others. I guess you don't like that. I guess you would rather discuss the minute details of the latest chin spoilers, $200 oversized throttle bodies, etc. I apologize if you consider my posts off topic, but cut me a little slack.

 

[Aaron 4.6]

For starters, lets look at a typical 2V dyno. I will use my old sheet from the 99 GT I used to own. The car was near stock with pulleys, T/A, and some weld-in Flows.



Click the thumbnail for a full-size pic...

I don't want to blow anyone's monitor with a huge pic, but this will be useful as a talking point. The first thing that is worth noting is that there is considerable torque available below the torque peak. Although the peak is at 4000 RPM @ 279 rwtq, even as low as 1500 RPM there is about 237-238 rwtq. That means that 85% of peak torque is available at an engine speed that is barely off-idle.

In my world, that makes the engine a torquer. Of course, with only 281 c.i. of displacement to play with, the only trouble is its not 'that' much torque. If we could do a simple ratio to the 5.0 we might say this... 302/281 * 279 lb-ft= 300 rwtq and we might all be pretty impressed with that. I know the real world isn't that simple, but the only difference between being impressed with the 2V torque and being non-plussed is a few c.i. in my book.

The other argument that says this engine is a torquer is the power curve. A 'revver' can't give up at 4500 RPM. Yeah, its better than an E7TE 302 motor, but with the inherently better port geometry of an OHC head it almost has to be better by default. The 2V is absolutely murdered by the intake design, and nowhere is this more evident in the work that Livernois Motorsports is doing in adapting PI intakes to non-PI heads (latest 5.0&SF). Despite the improvements in the later intakes, the airflow still makes an ugly 90* bend after the T/B and still has to snake its way through the long runners. High-revving engines would just be getting started when this motor signs off. You feel it when you drive it.

I don't have a dyno sheet of my 4V to compare, but they are available. The 4V is still a compromise, IMHO. A stock 4V has excellent flowing heads (particularly given the small displacement that must be filled), but mine has this godawful snake's basket of intake runners. The long runner's choke the motor at 6500 RPM, but provide streetable torque below 4k. The short-runner DOHC cars have been in the mid-300 rwhp range for a long time, which is incredible given what the specific output becomes. Unfortunately, this basically makes the 4.6 respond like two S2000 engines welded together. Great power from 5000-7500 RPM and dog slow everywhere else.

I guess my overall point is that Ford has created a versatile engine that can be adapted to a number of applications with great success. The engine performance profiles seem to fall right in line with what I would expect based on fundamental design elements. If you choke the engine with a restrictive intake system you will get great torque at a loss of peak power, and if you free up the intake you must lose some low-end response with the extra power up top.

I don't see anything wild in that.

 

[redlined50]

"If you choke the engine with a restrictive intake system you will get great torque at a loss of peak power" an extreme case of that is my car, it feels like it falls on its face over 4700rpm, its making a lot of noise but nothing is happening and the torque peaks really early.

 

[kirkyg]

YOU KNOW NOTHING ABOUT THE 4V!!!! lol J/K

hahahaha
a little birdie told me

 

[kirkyg]

That simply not true. Try overlapping the two powercurves for the 4valve and 2valve engines. You'll find that the 4valve has just as much low end torque, a higher torque peak with more peak torque and a higher rpm peak with more power also.

Its all the way around better period.

kirkyg

 

[DBMSTNG]

DBMSTNG:

Personally, I feel comfortable in my GT up to about 120 MPH. I can hold a conversation, steer with one hand, adjust my stereo, etc. at that speed. I really have to question the wisdom of going that fast in a pickup. That's all I was saying.

but you don't question the "wisdom" of driving 120 in a mustang with one hand and changing radio stations?

DBMSTNG:

You make the mistake of equating power with responsiveness. I don't think responsiveness has as much to do with power as it does with torque. Torque is twisting force. Power is energy applied to do work. Now a car with a lot of torque can really slap you in the back from a dead stop to 10 MPH. It hasn't done a lot of work (i.e. made a lot of power or moved the car very far), but it has exerted a great deal of twisting force.

put drag slicks on your car, drop the clutch at 2500rpm, then do it again at 4500rpm. then come back and tell me which run slapped you back in the seat more.

One person made the same argument I am making here by suggesting an experiment: take a car to its power peak, hold it there, and then step on the gas. Then do the same at the torque peak. You will get slapped in the back much more strongly at the torque peak than at the power peak.

see above. the experiment you describe isn't an accurate indicator simply because it doesn't take into account momentum.

Taking this a step further, almost all internal combustion engines have a hill-shaped torque curve, with torque increasing to a peak and then decreasing. So they become more responsive with increasing RPM as the tach needle approaches the torque peak, then they become less responsive with increasing RPM after the peak. The general statement you make - that cars are more responsive at higher engine speed - is not correct.

go drive an S2000 and tell me when the car becomes more responsive.

Joel's98GT, I hope you will read the last three paragraphs as well. Your asinine, boot-licking post is not appreciated. At least DBMSTANG is smart enoug to provide some useful information. You're just a frickin poser.

ouch, that is far worse than what Joel typed. he didn't make a personal attack, he stated that physics own you.

And please don't post that I don't know what I'm talking about. I have been down the quarter mile over 80 times and I ran 13.990 in my stock 2001 GT, with the spare tire, seats, stock tires, stock filters and oil, etc., in place. I can do most basic mechanic work: brake jobs, timing belts, etc. I even converted a car from TFI to Duraspark. I never took college Physics, but I took Physical Chemistry and Calculus III, and did well in both. None of this is earth-shattering (and I don't claim to be the reincarnation of Smokey Yunick), but it's just unfair to say that I don't know what I'm talking about.

none of that means you know a thing about how the internal combustion engine works, which is really what this whole thread is about.

Believe it or not, I knew the horsepower / torque equation

if you understood it, you would have realized that all engines make more tq than hp below 5252rpm. information is usless without knowing how to apply it.

My original point was really just that the 4.6L 2V has kind of a strange torque curve. It loses 42 FT/LB over a range of 1250 RPM (between the two peaks).

it isn't strange if you understand flow rates and 2V engines.

In this day and age, that's not commonplace.

how many other SOHC V8's are being produced right now? i can only think of 1 other at the moment. the Dodge 4.7L. it puts out similar numbers to the 4.6L.

The Acura RSX is an example of a car with the same torque number at both peaks.

you do realize that the RSX has a DOHC Vtec engine, right? it has 2 sets of cam profiles. to compare the peak numbers between the two cars would be foolish. apples to oranges. or do you just not know how cams manipulate the torque curve?

Losing 42 FT/LB between the peaks tends to indicate an engine that doesn't breathe very well, and is biased to low-end throttle response, but I don't think that's true of the 4.6L 2V. That was really the discrepancy I was trying to point out, and just get some theoretical discussion started. To me, the engine feels like it likes high RPM. I was just trying to see if others felt this way, and to reconcile this general, seat-of-the-pants impression with some hard numbers.

this contridicts your own statement that torque, not hp, provides more responsiveness. torque peaks at 4000rpm stock. that isn't a very lofty rpm.

Beyond these technical issues, I am really bewildered by the emotion with which you responded. I know most people do not use this forum in the way I do. I tend to post broad observations and questions, with a theoretical perspective that is not typical of others. I guess you don't like that. I guess you would rather discuss the minute details of the latest chin spoilers, $200 oversized throttle bodies, etc. I apologize if you consider my posts off topic, but cut me a little slack.

this is a forum for technical information. not mis-information.

 

[CuddaWuddaShuda]

if you understood it, you would have realized that all engines make more tq than hp below 5252rpm. information is usless without knowing how to apply it.

When did I ever deny that?

 

[DBMSTNG]

When did I ever deny that?

Usually a motor with a power peak at 5250 RPM would not exhibit the bias toward torque that the 260HP motor does.

shall i go into detail why this is wrong? if you understand the equation, you would not have posted that.

 

[Ben99GT]

That simply not true. Try overlapping the two powercurves for the 4valve and 2valve engines. You'll find that the 4valve has just as much low end torque, a higher torque peak with more peak torque and a higher rpm peak with more power also.

Its all the way around better period.

kirkyg

Go ahead, overlap the curves of a '96-'98 4V and a '99+ 2V, same mods or stock for stock. The 2V, on average, will make more peak torque and make more horsepower and torque below 3,000 rpm.

The Mach 1 4V is the only real exception to the 4V being weak down low.

 

[XtorT'r]

Man, this post got kinda nasty.