MSD ignition LEts see some

[Dr. Dyno]

If gearing becomes a variable then you open up a lot of different possibilites. Again, some of you will go crazy after I say this but it's true: A completely stock 4.0 with 4.88 gears will out torque a 4.6 stroker with 3.07 gears assuming the transmission and transfer case ratios are the same.

That's true but only because you're multiplying the lesser torque of a stock 4.0 by a greater amount. The resultant shorter gearing would result in a reduced maximum road speed in each gear and since the 4.0 makes less HP, it would also have a lower top speed.

I've read that you need at least 1 cubic inch for every lb-ft of engine torque you want. And unless you have a big block Chevy or Ford, you will find out rather quickly that you will need forced induction to get the torque you want.

The very best naturally-aspirated street engines make 1.4lbft/cu.in. so to make 450lbft from a naturally-aspirated engine, you need at least 320cu.in. or 5.3L. Now you see why I call BS on Clifford's claims.

 

[BBeach]

That's true but only because you're multiplying the lesser torque of a stock 4.0 by a greater amount. The resultant shorter gearing would result in a reduced maximum road speed in each gear and since the 4.0 makes less HP, it would also have a lower top speed.

Wouldnt that make it accelerate quicker because it would reach maximum power in a shorter time? Also, actual top speed could be increased if you were to gear it correctly. What i mean by this is that with my jeep with the aw4 4.0 3.55 gears, it hits limiter at around 116 or w/e and then its done because of limiter. Without the limiter, i dont think it would make it past 120 on flat ground with no wind merely because there isnt enough power at the 3500 or so rpm in the top gear. However, if you were to reduce the rear end gearing a certain amount, say 4.10 or 4.56, then your top gear (mine being .75:1 in tranny), would be better maximized. Im too lazy to do the math out, but i think if you were to have 4.10 gear, it would be x 4.10/3.55 so around ~4050 rpm at the same road speed in the top gear. But however, limiter exempt, the engine would have THAT much more power to overcome the drag, and all the other resistance against it. Basically, if you change the gearing properly, you would be able to make use of the higher end, while having a lower "theoretical top speed". With the gearing as is, it SHOULD be able to hit somewhere arond 150mph, but with the power available and the resistance against it, its not going to do it. I hope that makes sense/is right. :speepin:

 

[j99xj]

The 4.0 does not make "more torque than a 4.6", ever.

Very true....at the flywheel. But you can multiply torque to any amount you wish using gears.

Still not convinced?? Hook bumper to bumper with a tow strap to some other Jeeper and drive in opposite directions. One vehicle with the transfer case in 4 low, and the other in 4 high. Who do you think will win the tug of war? It has to be the guy in 4 low. Regardless of how many mods the guy in 4 high has done (including a stroker), he will lose. (Unless of course his engine is putting out 2.72 times as much torque at the flywheel, but that comes out to about 650 lb-ft flywheel torque, which is highly unrealistic for any n/a Jeep straight 6.)

Now if the gear ratios were the same for both vehicles in the tug of war, the stroker guy will whoop the other guys butt, thats a given.

Another useful example is that all cars produce faster acceleration in 1st gear than any other gear. Why is that? Because the torque multiplication is higher and the rpms are higher (thus more horsepower).

Take a little while to read this article, its a good read and makes perfect sense to me. http://personal.riverusers.com/~yawpower/tqvshp.html

 

[Beej]

So I read that page, and unless I'm mistaken, he's also proving that torque is still where its at, not horsepower, he's just using funky math and examples to come up with his results. He's factoring in variable rpms instead, the higher rpms are what yield the higher horses due to the fact that horsepower is a function of torque and rpms. His comparison seems a tad specious, but I'm no engineer and my math is still just grade 12, so I can't prove my statements the same way. It just strikes me that he's is comparing apples to oranges as he 'proves' hp is more important than torque...

Granted, you can alter measurable torque through gearing, that's beside the point though, as I was originally talking about flywheel torque...

Can somebody else educate us further here? I'm still not able to entirely wrap my head around this one...

 

[Dr. Dyno]

Let's compare two "engines" in the same vehicle (identical weight). Vehicle A has a 4.0L "revver" engine making 300hp@6000rpm and 300lbft@4500rpm with a 6600rpm redline, while vehicle B has a 6.0L "torquer" engine making 300hp@4000rpm and 450lbft@3000rpm with a 4400rpm redline.
If both were identically geared, vehicle B would have better in-gear acceleration but the maximum speed in each redline-limited gear would be reduced because this engine would have a lower redline rpm. Both should have the same theoretical top speed because they both have 300hp, provided vehicle B could reach that speed without hitting the rev limiter first.
In reality, these two vehicles would NOT be identially geared because their engines have different power delivery characteristics. If vehicle B had 50% taller gearing than vehicle A (let's say 5.13's for A and 3.42's for B), in-gear acceleration would be the same, the maximum speeds in each redline-limited gear would be the same (vehicle A would reach those speeds at 6600rpm whereas vehicle B would only need 4400rpm to reach the same speeds), and the 1/4 mile ET/trap speed would be the same. Both will have the same top speed but vehicle A might reach that speed at 6000rpm in top gear while vehicle B would only need 4000rpm to reach the same speed in top gear.
The low revving "torquer" engine can be built with cheap, cast components but the smaller "revver" engine will need expensive forged components to survive the higher redline rpm required to reach the same performance level of the higher displacement "torquer". Now you can see how that principle can be applied to the Jeep 4.0 and stroker engines.

 

[MudDawg]

That (the article)is an interesting discussion...but in essence it is a discussion about the effects of gear reduction. For all practical purposes torque (and horsepower) are the product of three things (at a given rpm)...Cylinder pressure, stroke lenght, and thermal efficiency...minus frictional losses.

A typical diesel engine produces massive torque because of the extreme cylinder pressure and the long stroke. But it cannot be revved very high...mechanical limitations due to the long stroke and the mass of the reciprocating assembly...

A top fuel engine...500 cu in...makes around 6k (theoretical..no dyno will handle one, and the engine will eat itself long before a stable reading can be taken) horsepower at 8.4k rpm. The cylinder pressures are staggering...the effects of the supercharger and the nitromethane.

Want a more powerful engine?? Make it as efficient volumetrically as possible (but you will need to choose at what rpm you want it to work at), use a fuel with high BTU per Lb..run it as lean as possible without detonation, contain as much heat as possible in the cylinders, and reduce frictional losses.

 

[j99xj]

In reality, these two vehicles would NOT be identially geared because their engines have different power delivery characteristics. If vehicle B had 50% taller gearing than vehicle A (let's say 5.13's for A and 3.42's for B), in-gear acceleration would be the same, the maximum speeds in each redline-limited gear would be the same (vehicle A would reach those speeds at 6600rpm whereas vehicle B would only need 4400rpm to reach the same speeds), and the 1/4 mile ET/trap speed would be the same. Both will have the same top speed but vehicle A might reach that speed at 6000rpm in top gear while vehicle B would only need 4000rpm to reach the same speed in top gear.

Exactly. As long as the engine with less torque is geared lower, (numerically higher) to "regain" the lost low end torque from a hot cam and highly ported cylinder head, performance will virtually be the same because the horsepower output is the same, just at different speeds.

Now I think we can also agree that the torquer engine will be far more reliable, cheaper to build, and cheaper to maintain. That's a given.

I think I'm going to run some simulations and see what happens. Maybe I'll upload some screenshots.

 

[JJacobs]

A typical diesel engine produces massive torque because of the extreme cylinder pressure and the long stroke. But it cannot be revved very high...mechanical limitations due to the long stroke and the mass of the reciprocating assembly...

Supposedly the torque of a diesel is not simply because of the long stroke, but that the power stroke is more of a long steady push rather than a quick bang. The fuel takes longer to burn in the chamber (dish in the piston) and voila, TQ.

I'm not a 4 litre hater by any means folks. I see some BS on here from time to time, like the spewing about Clifford. Also the lemming like mentality that an extra 12 percent displacement yields 70 percent power increases automatically is kind of annoying.

http://www.highperformancepontiac.com/tech/0410pon_most_powerful_pontiac_v8/

But how about that article? Makes you think huh? A friend of mine has a car with an inline 6, it's a chevy trailblazer 4.2, destroked to 4.0. It has two T-78 turbos and a Procharger F-3A, 70psi should get us about 2500 HP and hopefully the title 'quickest EFI car on the planet' at around 5.70's.

I don't see why a Jeep 4.0 couldn't get well over 1000 HP with custom bottom end parts, alcohol EFI and lots of boost- everyone else is doing it! I just don't want to try and pay that bill right now, though someone in here surely has the cash burning a hole in their wallet

 

[j99xj]

I don't see why a Jeep 4.0 couldn't get well over 1000 HP with custom bottom end parts, alcohol EFI and lots of boost- everyone else is doing it! I just don't want to try and pay that bill right now, though someone in here surely has the cash burning a hole in their wallet

Um......... I'm going to call BS. Formula 1 engines can barely make that, and thats at 20,000 rpms.

In order to produce high horsepower, you need high rpms, and that means you need a big bore and a short stroke. If the stroke is too long for the rpms the engine will break apart shooting pistons through your hood possibly hurting some innocent by stander. Not cool.

True high performance engines are engineered from the ground up to make the most horsepower possible. Reliability, fuel economy, and engine longevity are not at the top of the engine builders list.

The Jeep 4.0 was and is an excellent engine. The reasons for its success is the fact that it was/is a very reliable engine, gets decent fuel economy, and provides a wide powerband that is suited for all types of average driving, from off roading to highway passing. Making improvements to improve horsepower/torque are easy and cheap, and an easy route to better performance is as close as your local junkyard. (258 cranks etc)

But 1000 hp of it is just rediculous. Thats 250 horsepower per liter.

 

[Beej]

1000hp is doable in a turbo'd big block no problemo. They do it at under 6500 rpms pretty regularly. Check out http://www.nelsonracingengines.com and click on videos. Mind blowing, however there ain't no inline sixes in their stable...

 

[MudDawg]

Not me...I'm so poor I can't pay attention...I have plenty enough reliable, long lived power...If I get the need for speed...I hitch up the trailer and take my bike to the track and squeeze a few smurfs into those little blue bottles..

 

[MudDawg]

The cost for horsepower is inversely proportional. The first 50 or 60 is cheap..the last 2 cost mega bux..

If you want to see a truly kickass (street) jeep, check out the MJ "parts chaser" truck that Hesco has...

 

[JJacobs]

But 1000 hp of it is just rediculous. Thats 250 horsepower per liter.

Your point?

Get your head out of the sand for a while.. this stuff is out there. Did you even read the link I attached? Figure a 242 is 1/2 the displacement of that Pontiac, so 1000 is theoretically possible while the parts list may be huge. If you don't understand the potential of boost, please stay out of this conversation.

 

[j99xj]

Your point?

Get your head out of the sand for a while.. this stuff is out there. Did you even read the link I attached? Figure a 242 is 1/2 the displacement of that Pontiac, so 1000 is theoretically possible while the parts list may be huge. If you don't understand the potential of boost, please stay out of this conversation.

I thought we were talking n/a applications, geez you don't have to be rude. Boost will make a lot of power, no doubt, but I still believe 1000 hp out of a supercharged Jeep straight 6 is highly optimistic, even if the engine is a stroker.

 

[Beej]

I agree, I don't think you can get 1000hp out of a 4.0 inline six. A heavily blown DOHC inline six, yes, but I just don't see in a pushrod OHV inline six. 70lbs of boost is just campfire talk. Where would a realworld application be?

 

[JJacobs]

Rude's my middle name!
70psi is campfire talk? I have pictures of that car, but it won't be fired for a couple more weeks. On a Jeep 4.0 70 psi is a pipe dream, sure. I'd love to try a 1000hp 4.0/4.6 but only after winning the Lotto.. I bet it could be done.

 

[j99xj]

Rude's my middle name!
70psi is campfire talk? I have pictures of that car, but it won't be fired for a couple more weeks. On a Jeep 4.0 70 psi is a pipe dream, sure. I'd love to try a 1000hp 4.0/4.6 but only after winning the Lotto.. I bet it could be done.

Go for it. But if you won lotto and want absurd amounts of horsepower you need to omit reciprocating engines all together. Go for some gas turbines. http://en.wikipedia.org/wiki/Gas_turbine#Gas_turbine_for_mechanical_drive_applications

 

[Bouncy]

Damn...read the rest of this thread.

All this from a question about WHICH COIL FROM MSD for a Jeep 4.0L

Laughed at the 1000hp is 250 per cylinder...If it had 4 cylinders maybe

Boost is good to work with but the conversation started orginally about coils and wires...The NA motors. Now its about boost.

Each would seem to have the need for a separate thread.

All and all...power can be made and provided you have good equipment and good blancing, you can make power in upper RPMs. Can't say I am going through all the effort to bypass the 5k limit on the computer but if a simple fix comes out, I will most likely chip/change mine to 6k like my other jeep.

 

[dzolcali]

yeah I just quit this thread like four pages back cause it got way off topic LOL...oh well

 

[streetpirate]

in the true spirit of naxja, everything past the third page of the thread is people rambling off topic about ideas brought up by the original question.

and this is where most of the good stuff is