I am working on rebuilding a chrysler 2.5L tbi engine in my 1994 dodge shadow. Everything has been going fine with the rebuild but the balance shaft unit is also in need of a rebuild. I have taken it to 3 different shops and they want a lot of $$$s to do machne work on the balancer and chrysler wants about $550 for a new one(ouch) and my thoughts were to just leave it off and plug the oil supply hole. What do i do here can i leave this off? I have looked at several sites that say you can and gain 10-14hp but i dont know anyone that has done this. Is there any chrysler 2.5L 4 cylinder experts out there that have done this? Is there any difference in the way it runs without the balance shafts? Please advise! Thanks!
Chrysler 2.5L SOHC balance shafts.
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allpar web site
So it appears to be quite "doable" ...but I couldn't find a procedure for you. Looks like you have more than enough resources for info at allpar.
10-14HP is way high..probably more like 2-3. Your idle will vibrate the car a bit more, but not much else should be affected.
Go to TurboDodge.com
You can ditch the balance shafts no problem. Just plug the hole. Also you will have to add extra oil without the assmbley.
Note the balance shafts do not balance anything, the dampen out 3rd harmonics and you wont notice it.
another good tip, look at the hole where your oil pump bolts up to bottom of the block, the opening on the pump base is oval and the opening on the block is round. Get a dremel tool and grind the hole on the block to match the pump. That is good for 7HP and eliminating the balance shafts is good for 10 HP.
VNT
You can ditch the balance shafts no problem. Just plug the hole. Also you will have to add extra oil without the assmbley.
Note the balance shafts do not balance anything, the dampen out 3rd harmonics and you wont notice it.
another good tip, look at the hole where your oil pump bolts up to bottom of the block, the opening on the pump base is oval and the opening on the block is round. Get a dremel tool and grind the hole on the block to match the pump. That is good for 7HP and eliminating the balance shafts is good for 10 HP.
VNT
I thought the balance shafts conteracted a 2d order imbalance. Yes plug the shaft bearing oil holes as they receive full oil pressure.
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Let's drift
and discuss harmonics. Now I'm somewhat aquainted with electrical harmonics. It's a simple sag in the sine wave. The "order" is always a multiple of the fundamental (in our case 60 htz). Odd harmonics are the offending ones ..hence the 3rd, 5th, 7th, etc. are the ones always sought to be mitigated via a number of modalities. Chokes ..iron cores ..etc.
So how does one determine the "fundamental" in mechanical harmonics? One could assume the crankshaft ..and whatever speed that may be at would establish your fundamental. Can one also assume that "even" harmonics are not as offending as "odd" mechanical harmonics??
So how does one determine the "fundamental" in mechanical harmonics? One could assume the crankshaft ..and whatever speed that may be at would establish your fundamental. Can one also assume that "even" harmonics are not as offending as "odd" mechanical harmonics??
Balance shafts
This was explained to me by one of the Engineers at Chrysler, Ed Peters, note he built many of the SCCA engines in late 80's and Neon motors and I belive he consulted with the super Touring Stratus team which clobbered the Accords in the 95 series. He developed some nice pieces for the Turbo cars and some NA engines.
anyhow the 2.5 (any motor over 2.3 liters) will have a certain resonance set up due to the long stroke. Mistsu developed the counter rotating shaft to dampen out this resonance. To someone younger, you would probably not perceive the resonance in the car, but a 60 year old who was used to driving a big Buick with a V8 would. So Chrysler liscensed the technology and put the system in the 2.5 and also later on the 90 and up common block 2.2. Note the shafts dont balance anything, that was just a marketing term. Most folks who do a serious build up on a 2.5 ditch the shafts, or if you have the pan off, cut the chain and plug the hole for the oil feed. It is best to remove them and save the weight and get rid of the parasitic loss which is 10-14 HP, depending on RPM.
Here is a link to a freinds page, he has a link on how to do it, also check out his 375HP 2.2 RT in a K-car.
http://www.members.aol.com/mopartek/home.html
Also here is another link, go to Turbo Database section 8, Lubrication and Balance shafts.
http://www.thedodgegarage.com/
This site is also a good one to see what you can do with these engines which were probably the stoutest 4 cylinder engines from that time period which produced the most power and with
some basic upgrades can make huge power for little money. If you have a fast modem download and watch gary clobber a high $$ import in the finally at the sport Compact Event at NED in 01 kind of rained on their parade
VNT
This was explained to me by one of the Engineers at Chrysler, Ed Peters, note he built many of the SCCA engines in late 80's and Neon motors and I belive he consulted with the super Touring Stratus team which clobbered the Accords in the 95 series. He developed some nice pieces for the Turbo cars and some NA engines.
anyhow the 2.5 (any motor over 2.3 liters) will have a certain resonance set up due to the long stroke. Mistsu developed the counter rotating shaft to dampen out this resonance. To someone younger, you would probably not perceive the resonance in the car, but a 60 year old who was used to driving a big Buick with a V8 would. So Chrysler liscensed the technology and put the system in the 2.5 and also later on the 90 and up common block 2.2. Note the shafts dont balance anything, that was just a marketing term. Most folks who do a serious build up on a 2.5 ditch the shafts, or if you have the pan off, cut the chain and plug the hole for the oil feed. It is best to remove them and save the weight and get rid of the parasitic loss which is 10-14 HP, depending on RPM.
Here is a link to a freinds page, he has a link on how to do it, also check out his 375HP 2.2 RT in a K-car.
http://www.members.aol.com/mopartek/home.html
Also here is another link, go to Turbo Database section 8, Lubrication and Balance shafts.
http://www.thedodgegarage.com/
This site is also a good one to see what you can do with these engines which were probably the stoutest 4 cylinder engines from that time period which produced the most power and with
some basic upgrades can make huge power for little money. If you have a fast modem download and watch gary clobber a high $$ import in the finally at the sport Compact Event at NED in 01 kind of rained on their parade
VNT
Gary, I don't know much about harmonics, but in engine design where vibration is concerned, you have primary and secondary balance. To get a nice, smooth running motor, you need both. Primary balance is achieved when the counterweights on the crankshaft exactly balance the reprocating mass of the piston, rings and connecting rod. This should be a given in any engine. Secondary balance is achieved when the movement of one piston is balanced by the movement of another, in other words, when one piston is at a certain rotation point on the upstroke, another one is at exactly the same rotation on the downstroke. To accomplish this, you need an inline 6 or a V12. Any other engine would require a balance shaft to approximate the motion of an opposing piston movement and dampen the vibration. You can certainly run an engine without a balancing shaft, but it will vibrate more than one with such a shaft.
There is also tertiary engine balance, but that information is harder to come by and I'm not sure it's all that important.
There is also tertiary engine balance, but that information is harder to come by and I'm not sure it's all that important.
Matt, What the Chrysler engineer allegedly said was a bit strange... Might explan why Chrysler 4 bangers aren't the smoothest engines around
Your explanation was closer,
From:
http://www.thrashercharged.com/tech_htm/adv_engine_design.shtm
"Primary forces are inertia forces created by the acceleration (+ and -) of the piston assembly mass caused by the rotating crankpin’s projected motion along the line of stroke due to the reciprocating motion of the piston assembly.
Secondary forces are those inertia forces caused by the projected motion perpendicular to the line of stroke caused by the rotating motion of the connecting rod. That is, the secondary force is due to the additional piston acceleration (both + and -) produced by the rotating crankpin increasing or decreasing the inclination of the connecting rod to the line of stroke. During the first 90 deg of crank rotation, this secondary movement of the connecting rod is away from the line of stroke, thus adding to the piston movement while during the second 90 deg of crank rotation, this secondary movement of the connecting rod is toward the line of stroke, thus subtracting from the distance the piston moves. Furthermore, secondary forces increase and decrease magnitude at twice the frequency of the primary force, but their maximum values are only about ¼ of the dominating primary force."
Harmonics are normally vibrations at some multiple of the natural frequency of an object. A crankshaft, like every other mechanical part is a spring whether we like it or not. The crank with it's attached masses forms atuned system that will resonate at some frequency. Harmonic balancers are used to damp out vibrations at that frequency.
The reason most crankshafts have harmonic balancers on them is to reduce the harmonic vibration of the crank at it's critical frequency.
Balance shafts effect balance at all speeds and aren't harmonic balancers by normal criteria.
Your explanation was closer,
From:
http://www.thrashercharged.com/tech_htm/adv_engine_design.shtm
"Primary forces are inertia forces created by the acceleration (+ and -) of the piston assembly mass caused by the rotating crankpin’s projected motion along the line of stroke due to the reciprocating motion of the piston assembly.
Secondary forces are those inertia forces caused by the projected motion perpendicular to the line of stroke caused by the rotating motion of the connecting rod. That is, the secondary force is due to the additional piston acceleration (both + and -) produced by the rotating crankpin increasing or decreasing the inclination of the connecting rod to the line of stroke. During the first 90 deg of crank rotation, this secondary movement of the connecting rod is away from the line of stroke, thus adding to the piston movement while during the second 90 deg of crank rotation, this secondary movement of the connecting rod is toward the line of stroke, thus subtracting from the distance the piston moves. Furthermore, secondary forces increase and decrease magnitude at twice the frequency of the primary force, but their maximum values are only about ¼ of the dominating primary force."
Harmonics are normally vibrations at some multiple of the natural frequency of an object. A crankshaft, like every other mechanical part is a spring whether we like it or not. The crank with it's attached masses forms atuned system that will resonate at some frequency. Harmonic balancers are used to damp out vibrations at that frequency.
The reason most crankshafts have harmonic balancers on them is to reduce the harmonic vibration of the crank at it's critical frequency.
Balance shafts effect balance at all speeds and aren't harmonic balancers by normal criteria.
XS, yeah, that wording is a little wierd. It sounds like he was trying to dumb it down. After reading it a few times, though, it sounds accurate enough, but not very technical. If he had mentioned the secondary balance issue and said that the long stroke creates additional vibration, instead of "resonance", it would sound a lot better.
BTW, I should mention that a V8 comes very close to achieving inherent secondary balance, which is why they're so smooth without balancing shafts. They're not quite as smooth as an inline 6, but close enough.
BTW, I should mention that a V8 comes very close to achieving inherent secondary balance, which is why they're so smooth without balancing shafts. They're not quite as smooth as an inline 6, but close enough.
XS650 and Matts
It is resonance, if it(shafts) balanced anything, what do yo think would happen when you remove the shafts? Do you think people would remove the shafts if it created an imbalance? Explain why the Dakota trucks(with the 2.5) never had the shafts??? The engines are balanced with the couterweights. 2.2's had cast and forged cranks, the 2.5 had cast cranks.
Beleive me, if I showed you 2 identical 2.5's, one with shafts and one without, you would not know.
Per the NVH comment, that has a lot to do with the motor mounts, baffling in the engine, accesories etc, not if the engine is balanced. The 2.2/2.5 engines were never noted for their smoothness, but I guess that was the tradeoff for making more HP and tourque with the turbo engines relative to other 4 cylinder engines of their time.
BTW, I am an Electrical Engineer and I did not try to dumb down anything. I was relating what I learned about the balance shafts from a Chrysler Engineer and I would tend to believe him.
Go here and you would understand that the guy knows what he is talking about.
http://www.thedodgegarage.com/friends_ed_peters.html
VNT
It is resonance, if it(shafts) balanced anything, what do yo think would happen when you remove the shafts? Do you think people would remove the shafts if it created an imbalance? Explain why the Dakota trucks(with the 2.5) never had the shafts??? The engines are balanced with the couterweights. 2.2's had cast and forged cranks, the 2.5 had cast cranks.
Beleive me, if I showed you 2 identical 2.5's, one with shafts and one without, you would not know.
Per the NVH comment, that has a lot to do with the motor mounts, baffling in the engine, accesories etc, not if the engine is balanced. The 2.2/2.5 engines were never noted for their smoothness, but I guess that was the tradeoff for making more HP and tourque with the turbo engines relative to other 4 cylinder engines of their time.
BTW, I am an Electrical Engineer and I did not try to dumb down anything. I was relating what I learned about the balance shafts from a Chrysler Engineer and I would tend to believe him.
Go here and you would understand that the guy knows what he is talking about.
http://www.thedodgegarage.com/friends_ed_peters.html
VNT
Sorry, VNT, I didn't mean to strike a nerve, but the explanation in your previous post just doesn't completely (emphasize completely) jive with my understanding of balancing shafts. I'm not the expert, certainly, but the only reason I've ever heard for these shafts is to reduce vibration, not resonance. I understand resonance to be a phenomena that occurs when an object is prompted to vibrate at its natural frequency, which doesn't make sense to me in terms of quieting down an engine. Also, in my post, I made the distinction between primary and secondary balance, the former being essential to engine operation, the latter being desirable, but optional. I stated that all engines should have primary balance, but that shafts are used to give secondary balance to engines that don't naturally have it, usually inline 4's and V6's. As I previously stated, the engine will run just fine without the shaft, but the shaft makes it more quiet and smooth.
I'm not trying to knock Mr. Peters, but I will point out his background is in failure analysis, not vibration and sound analysis. I also implied that I basically agreed with what he said, but it sounded simplified. I was not accusing you of dumbing it down.
I'm not trying to knock Mr. Peters, but I will point out his background is in failure analysis, not vibration and sound analysis. I also implied that I basically agreed with what he said, but it sounded simplified. I was not accusing you of dumbing it down.
If you remove the shafts, the engine gets a bit rougher, they're there to cancel secondary imbalance and aren't critical for engine life or people who don't mind raspy feeling engines. There is alot of material online and in libraries about secondary imbalance if you are interested.
NVH stands for noise, vibration, harshness. It's exactly the reason the bean counters finally allowed balance shafts in some American 4 cylinder engines. Taking care of the mounts, bracketry and other stuff is secondary to eliminating the source of the vibration in the engine.
There is nothing in that website that indicates anything other than he is an accomplished hot rodder and worked in a field unrelated to the topic at hand. He may very well understand the purpose of secondary balance shafts and be an expert in the field of engine balance, but what you quoted doen't indicate so. Using the word "resonance" for "imbalance" is just plan wrong, not a dumbed down explanation.
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Errr ..just to straighten out what I believe is leading some assertions astray here....
The 2.5 in the Dakota is NOT the 2.5 with balance shafts (minus the balance shafts). It is an AMC carry over ..and an adaption of the AMC I6 (258, 4.0) created in 1983 (84 maybe) and was NEVER on a Chrysler draft board before its manufacture. It was never manufactured for, or installed in, a FWD application. It is not a OHC engine.
The 2.5 in the Dakota is NOT the 2.5 with balance shafts (minus the balance shafts). It is an AMC carry over ..and an adaption of the AMC I6 (258, 4.0) created in 1983 (84 maybe) and was NEVER on a Chrysler draft board before its manufacture. It was never manufactured for, or installed in, a FWD application. It is not a OHC engine.
When one piston is at a certain rotation point on the upstroke, another one is at exactly the same rotation on the downstroke. To accomplish this, you need an inline 6 or a V12. Any other engine would require a balance shaft to approximate the motion of an opposing piston movement and dampen the vibration. You can certainly run an engine without a balancing shaft, but it will vibrate more than one with such a shaft.
Beleive me, if I showed you 2 identical 2.5's, one with shafts and one without, you would not know.
With this difference its hard to tell if they really help. I know My SE-R with is very smooth for a 2.5L 165 HP I-4. My wifes car the 2.7 L Hundayi shakes a lot at idle.If the expense of putting them on helped reduce bad vibs I would gladly give up 2hp..
Beleive me, if I showed you 2 identical 2.5's, one with shafts and one without, you would not know.
With this difference its hard to tell if they really help. I know My SE-R with is very smooth for a 2.5L 165 HP I-4. My wifes car the 2.7 L Hundayi shakes a lot at idle.If the expense of putting them on helped reduce bad vibs I would gladly give up 2hp..
I took the balance shafts out of my QR25 Nissan motor in my Spec-V. This car has soft motor mounts to begin with, so the difference is almost impossible to tell. If you look at the engine at idle you still don't see ANY motion. Its still super smooth. All you can really tell is an underlying raspyness to the engine charector. I would love to have one with the balance shafts right next to it to see if anybody else could tell a difference.
For the 8 hp dyno confirmed increase, the increased lube flow to other areas of the engine, the elimination of the weight, the increase by 1 qt. of sump capacity, the loss of oil frothing, the increased oil control windage tray, and finally the reduction of two parts moving at twice the engine speed (dual shafts)...I think it is WELL worth the short amount of time required to yank them out and plug the holes.
They switched from the mopar OHC 2.5 to the AMC 2.5 around 95-96 as the base dakota motor when they stopped making spirits and acclaims with the 1980's K-car motor. The 2.0/2.4 Neon family was born around then for car use. The AMC 2.5 recently, finally (2003ish) disappeared from the base Jeep Wrangler for the 2.4 as its last (US?) application.
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