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Discussion Starter #1
I have a bit of a weird question. But I think it may have been done before in racing. So I am going to ask it even if it sounds stupid.




On a completely balanced inline 6 engine;

Cylinder 1 and 6 = pair 1
Cylinder 2 and 5 = pair 2
Cylinder 3 and 4 = pair 3

Each of these "pairs" reach the top of the stroke at the same time.

If you could direct inject gas into say "pair 1" and fire 1&6 at the same time would that yield substantial performance gains?


From a performance and racing standpoint on a push rod, direct injection inline six (jeep 4.0 in my case) it seems like by changing out the cam with a custom one you could open the valves at the correct time and make it happen.


This could apply to any inline six that could have direct injection added to it.

Balance wise, I don't know. In my head it should work in theory. The cylinders being equal as they fire the engine block should not "rock" back and forth like in a 3 cylinder. The "pair" of cylinders firing at the same time may cancel each other out vibration wise. Or it could cause the block to break when 1&6 fire enough times :confused:



Has it been done before?
Would it be worth trying?
or am I asking to just wreck bearings. etc trying it?

Before someone says "just try it" know that it means a custom cam. I would like a bit of advise before I go to a shop with $400 and this crazy idea for a cam if the thing is doomed from the start.
 

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Inline 6 cylinder engines have been around for about 100 years. If there was a performance gain the way you want to go, don't you think engine designers would have done this years ago? When designing an inline six from scratch, the cost would be the same either way. Don't waste your time and money. Read some books on basic engine design and you'll see.
 

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pulse fire

A friend used to write automotive articles and had a few books. He said his father used to race dirt tracks in so Calif years ago and had a V 8 that had the "pulse fire" His theory was that a team of mules could pull better if they both stepped at the same time. His father also ran a reverse rotation marine engine, said that engine torque raised the outside front tire and put more traction on the left front tire.
 

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The flat crank design V8 from Ford that Timothale mentions still fires 1 cylinder per 90 degrees of crank rotation. No two cylinders fire simultaneously. The gains Ford gets with this engine is with big flow improvements with intake charge and exhaust scavenging along with dual overhead cams, 4 valves per cylinder, variable valve timing and a uniquely designed exhaust header. Lots of R and D and cost for sure. Certainly nothing as simple as firing 2 cylinders at the same time. I'm not a Ford guy but in this case my hat is off to Ford with the flat crank V8.
 

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you may want to use a pair of tuning tubes farther back in the exhaust system.. this may lower the pressure in the header collector and that would lower the pressure in the primary tubes making scavenging far better.

a friend did that with his hot N/A honda.. went from 265 to 275 horsepower on the bolt on the wheel flanges dyno with just that one change.

did you see the hot rod garage video last month.. where they beat on the headers with pipes and hammers... denting the primary tubes significantly.. they were blown away when the horsepower and torque went UP..

be amazed...

from hot rod magazine videos.. the bent header bash..

https://youtu.be/azPKIjxmmdU

i can explain why the bashed header tubes worked better..

the bashing made them a venturi... sped up the exhaust flow in that area... caused the pressure to drop farther .
 

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not too crazy if you ask me.. Might not be as smooth but might give more torque for pulling off a corner for a circle tracker running a 6..

Sam
 

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Discussion Starter #8
Easy?
No, what's the fun in that?

But here is how I look at it. If it works my bore just doubled. The engine would still inject the same number and fire the same number of times as a normal inline running next to it.
I believe I can wire it so that the signal for 1 injecting and firing also fires 6. When the pulse for 6 comes around that could be wired to inject and fire 1 etc. Early computer being used.

This would read as a very rich condition and the throttle body would open up fully. I see hitting a wall real fast. Direct injection would help. But I think the heads would be restrictive fast. Still doubling the bore should make power gains. I am running a 4.7 now with stock h.o. head and bigger throttle body. It goes.
Looking for a cheaper way to get more power and think this may work.

The thing may be restrictive or may not. Direct inject the air is there. The second set of valves are just as big as the first set opening pulling in that air. The throttle body would be the bottle neck more then the heads it seems.
 

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I have a bit of a weird question. But I think it may have been done before in racing. So I am going to ask it even if it sounds stupid.




On a completely balanced inline 6 engine;

Cylinder 1 and 6 = pair 1
Cylinder 2 and 5 = pair 2
Cylinder 3 and 4 = pair 3

Each of these "pairs" reach the top of the stroke at the same time.

If you could direct inject gas into say "pair 1" and fire 1&6 at the same time would that yield substantial performance gains?


From a performance and racing standpoint on a push rod, direct injection inline six (jeep 4.0 in my case) it seems like by changing out the cam with a custom one you could open the valves at the correct time and make it happen.


This could apply to any inline six that could have direct injection added to it.

Balance wise, I don't know. In my head it should work in theory. The cylinders being equal as they fire the engine block should not "rock" back and forth like in a 3 cylinder. The "pair" of cylinders firing at the same time may cancel each other out vibration wise. Or it could cause the block to break when 1&6 fire enough times :confused:



Has it been done before?
Would it be worth trying?
or am I asking to just wreck bearings. etc trying it?

Before someone says "just try it" know that it means a custom cam. I would like a bit of advise before I go to a shop with $400 and this crazy idea for a cam if the thing is doomed from the start.
Yes it's been done before, no it doesn't increase power output. Yes it puts really big twist moments in the crank which is a problem to dampen out with long shafts even with conventional firing order inline 6's. Yes it's hard on bearings mostly because of inadequate resolution of the harmonic twists introduced to the shaft.

In lines are always subject to wobble not only of the crank but also the block. The V block is inherently stiffer because of how forces are resolved by the shape, in-lines don't have this structural shape advantage and therefore require more material thickness hence weight to resolve these forces. The problem you soon hit with production inline blocks is that they are made for relatively low power outputs and do not have the additional material required to support much in the way of higher loads. The attempt to fire sets of cylinders in pairs essentially makes the engine into a large 3 cylinder, you can see where the vibratory modes will go with arraignment pretty easily.

Bogie
 

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The high output inline guys tell me that the inline design is stronger since the forces are more or less in one plane, whereas the V8 blocks have to deal with twisting forces. A local guy ran the ADRL races in a Toyota Scion with a L6 using a stock block(and stock head) making about 2300hp on 85 lbs of boost. All his competitors were using V8 with aftermarket blocks.
 

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The high output inline guys tell me that the inline design is stronger since the forces are more or less in one plane, whereas the V8 blocks have to deal with twisting forces. A local guy ran the ADRL races in a Toyota Scion with a L6 using a stock block(and stock head) making about 2300hp on 85 lbs of boost. All his competitors were using V8 with aftermarket blocks.
They would be wrong, all the loads are not straight down there is nothing to resolve them except the beam strength of the block. There are plenty of twisting forces because the primary combustion pressure is applied into the crank between about 20 and 60 degrees after TDC. The rotational inertia wants to make a straight line escape out the side which pulls the crank in that direction which pulls the mains which pulls the block. This is why even modest inline 6s use 7 mains. Where 4 mains have been tried which puts two rods on a common pin like a V8 it either leads to heavy crankshafts and blocks as with the old Chrysler slant six or to high main bearing failure rates as in the lightly built old Ford Falcon/Comet engine of 144/170 inches of 1960-1964-65 when they finally fixed it with 7 mains when the Mustang came out.

Bogie
 

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They would be wrong, all the loads are not straight down there is nothing to resolve them except the beam strength of the block. There are plenty of twisting forces because the primary combustion pressure is applied into the crank between about 20 and 60 degrees after TDC. The rotational inertia wants to make a straight line escape out the side which pulls the crank in that direction which pulls the mains which pulls the block. This is why even modest inline 6s use 7 mains. Where 4 mains have been tried which puts two rods on a common pin like a V8 it either leads to heavy crankshafts and blocks as with the old Chrysler slant six or to high main bearing failure rates as in the lightly built old Ford Falcon/Comet engine of 144/170 inches of 1960-1964-65 when they finally fixed it with 7 mains when the Mustang came out.

Bogie
I dont know Bogie, it made sense to me. If you think of a V8 as two L4 90 degrees apart, the the force on the main bearing web has to be more varied than in the conventional L6.
 

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Discussion Starter #14
Yes it's been done before, no it doesn't increase power output. Yes it puts really big twist moments in the crank which is a problem to dampen out with long shafts even with conventional firing order inline 6's. Yes it's hard on bearings mostly because of inadequate resolution of the harmonic twists introduced to the shaft.

In lines are always subject to wobble not only of the crank but also the block. The V block is inherently stiffer because of how forces are resolved by the shape, in-lines don't have this structural shape advantage and therefore require more material thickness hence weight to resolve these forces. The problem you soon hit with production inline blocks is that they are made for relatively low power outputs and do not have the additional material required to support much in the way of higher loads. The attempt to fire sets of cylinders in pairs essentially makes the engine into a large 3 cylinder, you can see where the vibratory modes will go with arraignment pretty easily.

Bogie
Can you go into this a bit more?
Not criticizing at all. If it wont work then it wont work. Save me the grand it would cost for the custom cam lifters etc to find it out on my own. That's why I am asking.


Basically I want to fire injector 1 and have a piggy back wire off of 1 with a one way diode, lets say half way, to fire 6. There would be a very minimal delay caused by the wiring. In that time number 6 would have reached the top and be heading down. But I am still putting fuel and spark into that otherwise dead cylinder forcing it down producing additional power. Right?


I think if I use a early renix system it will work better. It will allow me to fire the cylinders without being "smart" enough to know that the other cylinder is firing and try to adjust the timing or kill the engine as a result.


I am trying to keep with something that someone could do with a existing good running stock 4.0. Being the millions of them out there.
I want it easy.
Basically pull the engine, head, swap in a cam, new lifters, install the head, install the engine, wire everything up all piggy back style, turn the key and drive the thing.

I could take it a step further and have a interrupt that would kill the piggy back wires so it is running normally to save fuel. Then flip a switch of sorts and have the other cylinders fire. It would be less power then stock with the single cylinder firing and more wear with the cam and valves, moving, doing nothing.
I don't really care about fuel use. It would add even more mess to a already cluttered wiring harness full of the additional wiring and diodes. I am just adding that it could be done some what easily to fire only the single cylinder if someone wanted to save a little bit of fuel and wear to parts behind the engine.


I can see the bearings getting a workout. But how the cylinders fire it seems like they would cancel themselves out. 3 and 4, 2 and 5, etc. The loads on the bearings would be higher of course. But the dead piston is already moving down. I am just helping it move down faster. It will cause additional stress on the block. But I can't see how it would cause additional vibration. You still have the explosion. But the piston is not being forced into another direction so it would seem that the vibration increase would be minimal.


Not criticizing at all here. If it is going to take the engine down to a life span of 30k then I am good with that. I can find another good compression/running engine easily enough and eat the new cam cost. If it takes the life span down to 3k then forget it. I just want to know why it won't make more power and if it has been done what were the results.


Like I said it could be a very crazy idea. But if it makes say 30% more power that gets me into "light" stroker territory for around $1500 and a weekend that's a win in my book.


I like the 4.7 stroker I have under the hood currently. I am just looking for ways to replace it if something does happen and had this crazy idea. Being able to drop the same block in the same spot saving on all the many little things that a engine swap would take is worth a bit of looking foolish with crazy questions.



I am not looking to drop in a v8 guys. If it comes to that I will. I am just looking at all my options before I take that route.
 

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But here is how I look at it. If it works my bore just doubled.
And the number of cylinders was cut in half.

Where do I start?

Torsional harmonics in the crank AND the cam.
Airflow restriction in the intake (twice as much CFM is needed now per "cylinder" intake stroke).
Need for a custom intake design to match the flow pattern.
Very expensive custom balancing.

The list goes on. Suffice to say that if this were both easy and effective, LOTS of people would already be doing it. The fact that they aren't should tell you something.
 

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more imbalance forces.

When the piston moves down to the half way point in the bore the crank is NOT at 90 degrees Diagram it out the rod angle to throw angle . firing 2 cylinders at the same time will add moree imbalance forces and probably increase the amount of harmonics, more noticable at higher rpms.
 

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Discussion Starter #17
Ok, it will be breathing through a straw and be out of balance. Well, it was worth asking about. Thanks for your guys great help and insight.
 
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