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Robuilt said:


what mod is this? I already did a forum search but could not find anything. can you please elaborate?
This relates to the IAT sensor. It determines timing by sensing the incoming air temp. Colder air = denser air = advanced timing.
You can unplug this sensor and then stick a 100K ohm resistor into the connector instead of the sensor. This "fools" the computer into thinking the air is colder than it really is. This mod registerd 2hp when I dyno'd the first time.

Do a seach on "Puffin Box" for more details on a permanent hookup.
 

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BLKCobra01 said:
N20 always seems to work great for torque values :) Other then that everything has already been mentioned. These are modulars not pushrod motors they just don't have the same grunt down low like they use to.

Pushrods have nothing to do with it! (in case that's what you meant.)

5.0L have better TQ due to 4" bore and shorter 3" stroke! that's the only reason. The DOHC would have great TQ down low if they didn't kill our displacement. FYI :

4.6L = 3.55" bore x 3.54" stroke. IMHO i'd take the 4x3 anyday! just give me the DOHC as well. Then we have a truly great motor!

Oh yea, and Keep the block Aluminum!!!!:)
 

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lafear01 said:

Pushrods have nothing to do with it! (in case that's what you meant.)

5.0L have better TQ due to 4" bore and shorter 3" stroke! that's the only reason. The DOHC would have great TQ down low if they didn't kill our displacement. FYI :

4.6L = 3.55" bore x 3.54" stroke. IMHO i'd take the 4x3 anyday! just give me the DOHC as well. Then we have a truly great motor!
You're right about the pushrods. A DOHC engine is more reliable, more power efficient, and can operate at higher RPM. But DOHC doesn't itself reduce the available torque.

But you got the stroke / bore exactly backwards. For a given displacement, short stroke / big bore is for high RPM power; and long stroke / small bore is for low end torque.

The longer stroke gives the piston a longer moment arm to spin the crankshaft -- more crankshaft torque. But it makes the piston travel further with each revolution -- limiting high RPM operation, which limits the gearing you can use.

High RPM engines must have a short stroke, in order to reduce the speed of the pistons. They don't necessarily have less torque, but they get their torque at high RPM -- which is A GOOD THING because it lets you use more gearing.

Consider a typical 4-cylinder motorcycle engine -- redline 13,000 RPM, stroke 44 mm, bore 77 mm. High power, low torque.

Now consider a Harley Davidson engine -- redline 5,500 RPM, stroke 107mm, bore 92mm. Low power, high torque.

Of course, the high power low torque engine literally blows away the high torque low power engine in every performance category.
 

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lafear01 said:

Pushrods have nothing to do with it! (in case that's what you meant.)

5.0L have better TQ due to 4" bore and shorter 3" stroke! that's the only reason. The DOHC would have great TQ down low if they didn't kill our displacement. FYI :

4.6L = 3.55" bore x 3.54" stroke. IMHO i'd take the 4x3 anyday! just give me the DOHC as well. Then we have a truly great motor!

Oh yea, and Keep the block Aluminum!!!!:)
Wow, there are still a few smart people around here. I really get tired of everyone saying push rods make better torque. As lafear01 pointed out, it has nothing to do with the push rods. The 4.6L makes no torque because it is castrated in the displacement department. Check out the few guys on here that have stroker kits, or 5.4L engines. Those guys make some serious torque. The OHC setup just allows the engine to naturally rev higher due to its more efficient setup. That does not mean that it sucks at low rpms.

You want more torque, get NO2, roots supercharger, or stroke your motor. Other than that you are pretty much SOL. Long tubes are your best bet for a bolt on item, but don't expect miracles.
 

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Michael Clements said:
Of course, the high power low torque engine literally blows away the high torque low power engine in every performance category.
You said in more words, but design the engine for HP and gear it to the application.
 

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Slider I think you neglected to mention compression and head design. They are as critical as the displacment. Seems the 2v heads ie: GT motors make their torque much earlier then the 4v.
A little more to the equation then just displacment and stroke.

My comment earlier was in regards to comparinig the 4.6 to the old 5.0's. Your not going to get the mod motor to come alive at 1500 rpm like they did. Maybe I should say it stock fashion anyway. On the flipside of that they were out of steam by 5000-5500 as well.

But I'm with ya 100% a roots style blower would give him what he's looking for.
 

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TexasDevilDog said:

You said in more words, but design the engine for HP and gear it to the application.
That's right. The AMOUNT of torque is totally irrelevant. Design the engine to generate as much horsepower as possible and gear it to match whatever RPM range it uses.

Here's a quote from an earlier post:


Here's an extreme example to make the point: A theoretical engine with a mere 1.7 ft. lb. of torque flat from idle to 1 million RPM, using a 467:1 differential ratio will deliver the same 320 horsepower and the same shift points in each gear as the stock Cobra engine. But despite its mere 1.7 ft. lb. torque it would deliver far superior off-the-line low RPM grunt.

That's because with a flat torque curve, its 1.7 ft. lbs. at 1,000 RPM multiplied by the 3.37 first gear and the 467:1 differential is 2,675 ft. lbs. at the wheel of the car. Compare to the stock Cobra engine, which has about 175 ft. lbs. at 1,000 RPM, multiplied by 3.37 first gear and 3.27:1 differential which is only 1,928 ft. lbs. at the wheels of the car.

So it is not how MUCH torque that matters, but instead it's the SHAPE of the torque curve combined with the POWER output of the engine. And if we assume a reasonably flat torque curve, power is all that matters.
 

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BLKCobra01 said:
Slider I think you neglected to mention compression and head design. They are as critical as the displacment. Seems the 2v heads ie: GT motors make their torque much earlier then the 4v.
A little more to the equation then just displacment and stroke.

My comment earlier was in regards to comparinig the 4.6 to the old 5.0's. Your not going to get the mod motor to come alive at 1500 rpm like they did. Maybe I should say it stock fashion anyway. On the flipside of that they were out of steam by 5000-5500 as well.

But I'm with ya 100% a roots style blower would give him what he's looking for.
I did not mean you inparticular. I have been hearing that pushrod quote ever since the modulars came out. I guess it just gets under my skin a little.

Yeah, your right about the head/valve design. Lets not forget about cam profile. I guess the main point is that there are a lot of different ways to get more low end torque, but none of them are cheap or easy. They all require extensive engine modifications compared to what the 4.6L is in its stock form.
 

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SliderGT said:


You want more torque, get NO2, roots supercharger, or stroke your motor. Other than that you are pretty much SOL. Long tubes are your best bet for a bolt on item, but don't expect miracles.
What he said. There is no cheap solution. Maybe you should get a 03 Cobra. That will have lots of low end torque. AED and Saleen make roots s/c for the 2V.
 

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Discussion Starter #32
Ok, let's suppose I do break down and decide to get a roots-style blower. What kind of long-term reliability can I expect? And last time I checked, blowers for the 5.0s were quite a bit cheaper than the ones for the newer 4.6s. Will the prices come down eventually?
 

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BlackDawgGT said:
Ok, let's suppose I do break down and decide to get a roots-style blower. What kind of long-term reliability can I expect? And last time I checked, blowers for the 5.0s were quite a bit cheaper than the ones for the newer 4.6s. Will the prices come down eventually?
Go over and ask Boosted32V on www.svttexas.com or www.dfwstangs.net and he will tell you that he has a 97 Cobra that has a KB1500 roots and 100 shot with 130k miles on a stock engine. He has been blown since 70k. Spraying for I dont know how long.

His sig:
 

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SliderGT said:


I did not mean you inparticular. I have been hearing that pushrod quote ever since the modulars came out. I guess it just gets under my skin a little.

Yeah, your right about the head/valve design. Lets not forget about cam profile. I guess the main point is that there are a lot of different ways to get more low end torque, but none of them are cheap or easy. They all require extensive engine modifications compared to what the 4.6L is in its stock form.
Let's not forget the intake manifold design. The Mustang 5.0 engine has super long intake runners that promote great low-speed cylinder filling velocity. That helps generate great amounts of low end torque.
 

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Nino97CobraVert said:

Let's not forget the intake manifold design. The Mustang 5.0 engine has super long intake runners that promote great low-speed cylinder filling velocity. That helps generate great amounts of low end torque.
Yes. And they restrict airflow at high RPM, limiting the engine's top end power.

It's all a tradeoff. You can get high torque which is easy to launch but not necessarily fast. You can get high power which is fast but not necessarily easy to launch. You can get both, but then you have only two options: a "monster displacement" N/A V8 which is so heavy it will impair the balance of the car -- or forced induction, which will shorten the lifetime of the engine.

Choose your poison!
 

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Nino97CobraVert said:


Let's not forget the intake manifold design. The Mustang 5.0 engine has super long intake runners that promote great low-speed cylinder filling velocity. That helps generate great amounts of low end torque.
If you are talking about a 4v then disregaurd this. The 4.6L GT's have 22" intake runners, and they are definitely longer than the old 5.0 intakes. These long runners help produce more low-end torque. Yes, it does take away from the top end, but that's were freer flowing exhaust comes into play.

BTW, mine feels great low-down. My car on the dyno over a year ago put down 245rwtq at 2200rpm. Not too bad in my book for a 96 GT. She put down a max of 273.6rwtq at around 3750.

This was before I put in a 47K resistor, and the low-end feels a little better. But, I'm not compaining about torque, it feels fine.
 

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I was under the impression that a square bore/stroke was the best combo, ie. 3.5 in X 3.5 in. Am I just mistaken?
 

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00MustangGT said:
I was under the impression that a square bore/stroke was the best combo, ie. 3.5 in X 3.5 in. Am I just mistaken?
No single stroke to bore ratio is best for all engines. Different engines use a wide range of ratios. There is nothing "magic" about a 1:1 ratio.
 

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00MustangGT said:
I was under the impression that a square bore/stroke was the best combo, ie. 3.5 in X 3.5 in. Am I just mistaken?
A square bore stroke is best for an efficient burning engine or a design for emissions. In a combustion process, the engine is trying to oxidize the fuel, burn as fast and completely as possible. An equal bore stroke or square design allows the maximum distance from the center to be the shortest length in all directions. The flame front has less distance to travel. This is why the old 5.0 went away, because they would not meet today's emission requirements with its 4.00x3.00 ratio.
 

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TexasDevilDog said:

A square bore stroke is best for an efficient burning engine or a design for emissions.
Makes sense theoretically, but diesels are more fuel efficient than gasoline engines and they are usually undersquare.
 
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