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2.4L Discussion by Skrilla

* Intro *

Outline

Theories on Rotational Mass and the Cylinder Head
1. Compression Control
2. Head, block and HP
* Silent (Balance) Shaft Removal
1. Method 1: Severing the chain
2. Method 2: Removing the Driving Silent Shaft Sprocket

I hope you�re ready for some reading because I wrote this to be a guide as well as provide some thought to those who want to squeeze the extra bit of power from the 2.4L. This also provides early prep that is necessary before the swap is performed on your car. We are just fortunate that Chrysler was nice enough to economize and keep a lot of pieces the same for our hybrid engine and high performing chassis. Being that our cars can maintain drivability and controlled chassis dynamics at speeds well over 170mph this is just the sort of HP boost we need to exploit those possibilities.

Theories on Rotational Mass and the Cylinder Head

I feel this is a necessary topic, being that many people just don�t know what the shafts roles are, in engines. Some feel removing them will create too much high rpm vibration, which can be very true. The 2.4L engine has a redline of 6250rpms and a fuel cut at 6500. That�s close to 1K rpms lower than a 2gnt engine from their stock redline to our fuel cut. This all means our piston skirts could become angled at high speed (rpms) and scrape cylinder walls, but this is the extreme and, I suspect, would guess on an unbalanced 2.4L without balance shafts and 8000 rpms that this may be detrimental. Keep in mind I say unbalanced. The balance shafts create a VERY smooth running engine from idle to redline with a very linear power feeling. The 2.4L PT Cruiser, Stratus, Breeze, Cirrus all comes equipped with them. Some people have said they provide decent idle and enjoy it at the expense of HP. Well I am an enthusiast and shaft removal should be thought about carefully for the uninformed, never the less mine are removed, and I think it�s viable for everyday use. Even Tom Stangl (the VFAQ Guy) said this:

"I own 3 DSMs with no balance shafts, and only one has been rebalanced (the "race car" daily driver that's been dead for over a year). There is a noticeable rough idle, and a roughness at 4-6K (varies on different cars, I have also removed the bal shafts from 2 other cars), but it really isn't that bad. You'll freak out the first time you start it up, and it is annoying for a few days, then you don't really notice it much. It doesn't take long to get used to.

If you want a REALLY smooth ride, get the rods/pistons/crank balanced, but that will require pulling the head and tranny, so it is a LOT more work."

While he is not speaking specifically about our project motor he is only talking about a 2L but the concept remains. It just means there is a greater tendency to spin rod bearings because of the size. An engine that is too severely unbalanced causes this. A short stroke 2L can be slightly unbalanced from the factory but a 2.4L with a greater swing and longer rods can become an issue. So I would highly recommend Mobile 1 synthetic and to check your oil at a minimum of every two weeks. The fix would be to just get the entire rotating assembly balanced by a machine shop, if you plan on revving beyond 6500rpms on a regular basis (I do 7200rpms without balance and no problems yet). The shafts can be spun to 7200 but COMPLETE Shaft elimination is necessary if you want to retain your factory "I" beam which the front motor mount connects to. The factory 2.4L oil pan is much larger than the 2L, supporting about an extra 2 quarts of oil without the shafts, various counter rotating gears, shaft carrier and chain removed, but that area interferes with where the oil pan dips into the "I" beam so again the factory 2gnt pan is needed. Judging on how much rotational mass is disposed of with your AFX UDP I would guesstimate the power gain of the removal is somewhere in the 10HP+ range. It has been dyno proven that the Neon AFX UDP laid down 11HP at the wheels which means, based on that test, the 2gnt AFX would provide more power (it�s lighter than the neons), something like 12+. I can safely say that the shaft elimination will make your 2.4L much more raucous and lively and revving just as fast as the 2L, the main reason is due to the power the 2.4L makes (but imagine how slow it is with the shafts). So after observing the complete assembly of the shafts I would think the HP return would be closer 15HP+ (who knows), but I�ve stuck with a round number like 10. Rotational mass is cumulative when gaining HP, but loses its effect with every up-shift of your transmission due to TQ multiplication being spread thin as your gears become taller. So in 3rd gear with these two mods you would be provided in excess of 20HP in all motor form costing only that of the UDP. First and second become very lively gears. With that said you would no longer be messing with 150HP but a 170HP with the stock 2.4L head (not the 2gnt Head we�ll get to that in a minute). Now I�ve chosen to leave out possible power from the increased redline and fuel all the way up to 7200rpms because of the many variables involved with such a 1st time thing.

Compression Control

With this new engine also comes some thought on how power will be made: What about my cylinder head? Builders know a couple of things. One is that HP is made in the cylinder head and reliability, or TQ retention, is built into the block. The 420a head is from an abandoned Lotus 2.2L, racing program that Chrysler picked up for full production. At this time it outflows all B series motors from Honda and even the Mitsubishi 4G-63T motors. That says a lot. The chambers are all pent-roofs, providing help from preignition and helping increased cylinder head pressure (the deciding factor for power). That�s more potential for the builder. Compressions as high as 11.5:1 on pump gas and even 12.5:1 on ignition retard (I too fall into this category) are acceptable. While we are on the subject of compression here are some head mill figures you can run and their outcome (CR is rounded off):

0.020"=9.7:1
0.030"=10.0:1
0.040"=10.2:1
0.050"=10.4:1
0.060"=10.6:1

I gave a map to a 1.2 compression increase. A one point increase will provide your engine with a 4% HP return as a general rule while still low enough to continue using 87octane. Now cylinder heads are milled and blocks are decked, and you may get asked these things so I threw in this quick blurb about it. They both mean the same thing though, it�s all about removing combustion chamber volume and that is what makes compression. Since heads are easier to replace then I�d say mill the head and have some cam gears ready for timing adjustments, and forget about decking the block unless you�re sure about what you�re doing. Other things will affect compression as well such camshafts but most of all porting. Many do not know it but porting drops compression. Being that our 2.4L engine is of good size it�s OK to do serious gutting of the head when the redlines are increased to 1K with such a long stroked motor. The ports are short and provide very quick access to the combustion chamber. With a big engine and deep breathing this will be ok but porting can increase combustion chamber volume and slow intake velocity. Both drop engine efficiency (which means a loss in performance). I�ve smoothed the ports on my cylinder head and raised my compression with milling, which is now a tooth off on my timing belt. This is fine with cam gears, but I wouldn�t recommend more than a .060" mill off your head, the max is .090".

Block, Head and HP

The block is the strength and reliability of the engine while providing the method of horsepower reception. At 2.4L of displacement with a mild head, the 2.4 makes a measly 150HP, just 10 more than our 2L but with nearly 25% more engine. So where did the power go? Into low-end torque, which ranges from 162lbs up to 167lbs on the 2.4L�s. Who needs that when your car doesn�t weigh in the 3100+ pound range like the �cloud� cars from which the engine came. What we do with this power is take the low-end torque and transform it into more upper midrange power. With the 2gnt cylinder head rated to make power in the high midrange with a broad torque curve, HP should be closer to that 70HP/L like that in the 2L. So the 2.4L engine rated with 70hp/L will be close to 170. We�ll just say 165 for arguments sake, since that will be more realistic. The reason being, that on long stroke motors they make power down low. That combined with the high rev head will most likely generate something less the 70HP per liter. Now being that this 2.4L is a factory stroked version of our 2L, its pistons speeds are much slower. This makes so the pistons gain this lingering effect, which creates that midrange power, thus midrange HP. This is good but we want a little more power up high to utilize our gearing, unless you choose taller gears (numerically smaller ratio). So air is needed to feed this motor. This is a moment to be better safe than sorry, so I would recommend an intake manifold port and larger inner diameter throttle body. This is because high stroke motors have trouble breathing at high rpms and you�d hate to get ignition retard or incorrect air/fuel mixture that high in engine speed. If you plan on a turbo, then the extra porting isn�t necessary. In the real world all this maybe a little overkill but this was my 1st time with such a swap and nominal operation is more my concern. To control the extra fuel needs you will need an AFC or equivalent fuel controller. Now the stock fuel pump can handle the extra power, but I wouldn�t trust it for long. You could run into a lean situation. The AFC will need to be increased a minimum 25% across the entire rpms, before the engine is started, then after running adjust from there. So now we have gained power from the UDP and Shaft elimination plus the new cylinder head configuration. This will put you in the 185HP range with no other modifications and All Motor, not bad. To maintain proper tune you will need a real-time digital voltmeter for the O2 sensor and an EGT. The end product of this swap with the O2 readings, EGT, engine, UDP, intake manifold porting, bored or ported TB, and lastly AFC without any other boltons should be a conservative 195HP which makes 80.3HP/L. That�s a good 55 HP all motor extra not including a CAI, headers, exhaust, headwork, or raised compression. The torque increase should be at about 170 or more, although I�m not sure just �cause my main concern is the HP and our engines will make more than enough torque just out of sheer size and the modifications that we�ve just put into it, but if you need some more extras then add some compression, get custom reground cams or billets. A mill of .040" will get you about 6HP. Realistically the engine may be closer to like 200 or 205HP easy and you should be performing 0-60 in the 6-6.5s as well as keeping up with stock GS-T�s or even beating them. I was beating slightly modified GS-T�s with a complete entourage of nothing more than boltons on 87octane ZERO headwork and 40 overbore on the block! With everything I�ve talked about here if you can�t break into a low 15sec quarter mile, then you can�t drive!

Silent (Balance) Shaft Removal

As previously discussed removing these shafts will increase power. This write up is based on the assumption that the engine is removed from the chassis the UDP has been taken off the crank and the cylinder head is removed (it will have to be anyway to fit your 2gnt cylinder head). Now they�re actually called silencer shafts from the purpose they serve, which is to quiet the engine by balancing out mass vibrations in the rotating assembly. So removing them will add some more vibration to the engine and the swap in general will ad a bit more noise. If you are performing this swap then both of these should be minor concerns since you are really out to gain some power. There are some other minor benefits, however. Oil will be more accessible to your engine and power will come easier as the motor revs. There are two methods to remove the shafts. In these examples I refer to the bedplate which is the 2�" thick piece of iron between the block and oil pan.

Method 1: Severing the chain

The "quick" and relatively painless way.

1. Your shopping list: I prefer your basic set of metric 3/8" drive sockets and an offset flex-head ratchet for its length and torque. For cutting the chain you can use a rotary tool or some industrial sheet metal cutters (I would recommend the rotary tool like a Dremel with a heavy duty cutting disc available from Sears). Preferably an engine stand but I did all this with the cylinder head removed with the block bedplate and pan sitting on a small tire on top of a pallet. My stand was in use with another 420a. The picture below shows the block with a shot from the bottom with oil pan removed.

Figure 1

2. Remove the oil pan if not already done and observe the various bolts on the shafts carrier. Look inside the block at the end where the crank sprocket is.

Figure 2

3. You will see a chain running from the crank�s shaft gear into the shaft carrier. Take your Dremel and cut the chain.
4. With the chain removed you will be able to remove the shaft carrier in one complete piece. Just remove the main bolts that connect the carrier to the bedplate.
5. When reinstalling the oil pan use a new gasket and a small drop of RTV sealant where the bedplate meets the oil pump housing, it will be in two spots and is needed for extras protection against an oil leak.
6. Now for the last part is the oil pick up. Use the one from the 2gnt block or modify the one (bend) from the 2.4L to fit the shorter pan but make sure the pick up is very low.
7. Blocking the balance shaft oil passage is something that is very necessary. It lies underneath the shaft carrier and directly below the carrier bolt shown in the picture. You can�t miss it since they are only millimeters apart. I would suggest tapping the hole by a machine shop (unless you have a Tap and Die set) and plugging the hole with a screw and an insert or an iron screw. I recommend the iron screw because the bedplate is iron and two different metals that aren�t prepared and rubbing on each other will eat away eventually, so using an insert will prevent the need of finding a special screw as well. That�s it, happy revvin�.

Method 2: Removing the Driving Silent Shaft Sprocket

I went a little extreme with the money I had left with this last part so I thought I�d share it, and why not since the engine is opened up you can perform some routine maintenance

1. For this part, your shopping list grows a bit unless you already have them. You will need a jaw puller that utilizes bolts NOT arms, specially ordered from craftsman or some sears Stores, to remove the crank sprocket on the oil pump housing (I learned the hard way so you won�t have to). The Sears part number for this tool is 00947626000 and the manufacturer number is 47626. You will need to purchase the correct size screw from a Home Depot or equivelant. I wanted as little parasitic loss as possible so I added this to the "To Do List". You�ll also need an oil pump seal, oil pump discharge port "O" ring, 2-forearm sized sturdy screwdrivers (or pry bars) and lastly a thin screwdriver. Refer to picture below.

Figure 3

Note: This is the

WRONG way

to remove the crank sprocket. It will almost certainly break the sprocket, and it will damage the timing belt even if you do manage to get it off with this method. Use the proper 3-bolt steering wheel puller, NOT the 3-jaw puller pictured.

2. With the puller, take off the crank sprocket (remember bolt type not the arm type in the picture).
3. Take the screwdriver and very carefully remove the oil pump seal (AKA front crank seal) from off the crank. You must be careful not to prick and poke at the crank and prevent yourself from making nicks because this is sensitive equipment that will be reused (except for the seal of coarse) and you don�t want an oil leak. Once the seal is removed you can unscrew the various bolts holding together the oil pump housing. Do not remove the oil pressure relief valve, which is almost vertical and driving into the oil pump housing instead of the block.
4. Underneath the pump you will see the driving shaft sprocket. Take the sturdy screwdrivers and slowly work away the sprocket. Do this gently as to not mess with the crank geometry and create crankshaft-end play. If this happens you will run a greater tendency to spin some rod and main bearing.
5. With the sprocket loose remove the shaft carrier in one complete piece along with shaft driving sprocket altogether. The carrier is removed by unscrewing the main bolts that connect the carrier to the bedplate
6. While the pump is removed you can service it, replace it or just throw it back in (I rebuilt mine myself and cleaned it since the pump was still relatively new with only 60K miles on it) when you put the oil pump back on you will need to apply an anaerobic sealant to the oil pump housing and let it cure. The curing process instructions will be on the sealant you purchase.
7. Install the new discharge O ring with a light coat of clean motor oil and tighten all nuts and bolts
8. When reinstalling the oil pan use a new gasket and a small drop of RTV sealant where the bedplate meets the oil pump housing, it will be in two spots and is needed for extras protection against an oil leak.
9. Now for the last part is the oil pick up. Use the one from the 2gnt block or modify the one (bend) from the 2.4L to fit the shorter pan but make sure the pick up is very low.
10. Blocking the balance shaft oil passage is something that is very necessary. It lies underneath the shaft carrier and directly below the carrier bolt shown in the picture. You can�t miss it since they are only millimeters apart. I would suggest tapping the hole by a machine shop (unless you have a Tap and Die set) and plugging the hole with a screw and an insert or an iron screw. I recommend the iron screw because the bedplate is iron and two different metals that aren�t prepared and rubbing on each other will eat away eventually, so using an insert will prevent the need of finding a special screw as well. That�s it, happy revvin�

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Document statistics: Last modified on 2009-05-13 15:07:09 by thedawg