Mitsubishi Eclipse 3G Club banner

81 - 100 of 106 Posts

·
MINI by proxy
Joined
·
4,408 Posts
Discussion Starter #81 (Edited)
(another) EVO BUILD!

Some of the folks on Evolutionm.com really know their $#!7 when it comes to engine building!
The following thread illustrates one option when pairing our 4g64 block with a evo (or optima) head:
"<a href="http://forums.evolutionm.net/showthread.php?t=194711&page=1">4g64 2.1L Build Up</a>" -Essentially, what he's done is DESTROKE the 4g64 block using the (shorter stroke) crankshaft from a 4g63. The pictures on the first page are of just the block, crank, and pistons... not the head. The discussion, however, touches on a lot of issues with the complete pairing.

I'm currently reading through this 8 page thread (now on <a href="http://forums.evolutionm.net/showthread.php?t=194711&page=5">page 5</a>), and I'm finding quite a bit of food for thought. I invite anybody interested in this to join me in soaking up more knowledge. ...Some will be review for those who've followed my research thus far and have paid attention. ;)
 

·
Registered
Joined
·
1,690 Posts
I hope this doesn't come off as sounding like I'm revisting areas that have already been discussed, but I figured I'd add my two cents since they may help people with deciding things such as whether to use the Optima head or the EVO head. To start out, while I may be newer than some to Club3G, as well as to the Eclipse iteself, I'm not new to the performance side of automobiles. Not to boast (but to explain where some of my knowledge has come from), I graduated 2nd in my class from Universal Technical Institute (UTI) in Phoenix, AZ with the certified auto & diesel course. After that, I worked in the automotive industry for a while (both working on cars and forklifts), followed by 4 years as a mechanic in the Air Force. I'm still in the Air Force but changed jobs a few years back and now pursue this simply as a hobby.

On to the topic. Some have asked what would be better between the higher compression from the EVO head or the lower compression from the Optima head. The answer lies in what you are planning to build your engine (and car) for. With higher compression, the engine becomes more efficient and is able produce more power through a more efficient burn of the fuel. This directly translates into more power to the flywheel. This practice has been used for years with the muscle car crowd, and is down to a science in the arena. With higher compression, you must take both pre-ignition and detonation into consideration. Pre-ignition is when the fuel ignites before spark plug fires, while detonation is an uncontrolled burning (actually a violent explosion) of the fuel. Usually, higher octane fuel is required when the compression gets too high, but many engines today have safely run 10:1 compression with mid-grade, and sometimes low-grade (87 octane) gasoline. In a naturally aspirated context, high compression is a great way to increase the power output of an engine, as well as harness more potential from additional modifications. For forced induction applications, a lower compression is often desireable to reduce the possibility of pre-ignition and detonation...this is where the Optima head would come into play. In a sense, both raising the compression of a naturally aspirated engine, or utilizing forced induction on a low compression engine, are methods used to compress more of a volumetric quantitiy of air within the confines of the engine used...forced induction just does this to a much greater extent.

For those of you running a naturally aspirated engine who may want to switch to forced induction down the road, I have a third alternative for you 9as some of you may have already considered). For the short term, you can utilize the EVO head (if you're willing to pay the extra money) which will increase your static compression, and enjoy the increased power without concern for making improvements to your bottom end. When it comes time to add forced induction, you can rebuild the bottom end with dished pistons, which will increase the volumetric size of the combustion chamber (below the head gasket) and safely and efficiently lower your compression. I have not yet checked into the availability of such pistons for our engine, but from past experience you can simply contact any high-end piston manufacturer (I have had good luck with Arias in the past) and have them make a custom set of pistons with any features you desire. The price really shouldn't be too much more than a typical set (I was quoted about $100 each for 2.4L Stratus pistons about 8 years ago from Arias). This way, you could enjoy the increased compression now (while you're naturally aspirated), and reap the efficiency when you move to forced induction.

As for the question of how Flash was able to achieve increased power with the use of stock (EVO) cams, here's a little more explanation. As Tampa pointed out, the camshafts themselves are not opening and closing, but they directly control the opening and closing of the valves, which in turn allow the unburnt air/fuel mixture to enter the combustion chamber, and burnt exhaust gasses to be expelled. I don't have the camshaft specifications for our stock cam, or the stock EVO cam, but I think I can make an educated assumption. The cams in the EVO setup probably utilize a different duration, lift, and possibly centerline that is tailored more towards producing power in the upper RPM spectrum than the lower. Our engine, on the other hand, probably is designed to produce more power in the lower RPM spectrum since that is where most average drivers spend their time with regards to normal street driving. By increasing the duration (how long the valve is open for) the cam can let a greater quantity of air move in and out of the cylinder. Increasing the lift does much the same thing, but without respect to rotation of the crankshaft. Valve centerline is the relation between the center of the intake lobe and the center of the exhaust lobe (not adjustable on a SOHC, but it is adjustable on a DOHC). By using charachteristics that would allow for an increase in the amount of air/fuel that can physically enter the engine (by increasing the duration and lift), an engine will make more power at the upper RPMs but seem to make less at lower RPMs (which is what Flash reported in his post). This is also the reason that many "race" cams are listed as not being for street use...the intended powerband is above what is required for normal street driving, but great for high-RPM racing. Although many people have utilize high-lift/duration cams on the street, there is usually a loss of what the average person would consider to be "streetability" of the engine.

Another point which I have not yet looked into, but maybe someone can shed some light on, is that I assume that in addition to a smaller combustion chamber, the EVO head might benefit from more efficient intake and exhaust ports. I'm not sure if anyone has compared this aspect of the two heads yet, but if the EVO head has larger and more efficient ports, then an even greater potential for power production could be achieved.

Tampa, sorry if some of this was a little off topic, but I have recently begun reading up on performing this swap and really like the focus you have maintained here...I just wanted to explain a couple thoughts that had been brought up for those who were wondering. Hopefully this was some use to those who take the time to read through it.
 

·
Registered
Joined
·
1,433 Posts
Another point which I have not yet looked into, but maybe someone can shed some light on, is that I assume that in addition to a smaller combustion chamber, the EVO head might benefit from more efficient intake and exhaust ports. I'm not sure if anyone has compared this aspect of the two heads yet, but if the EVO head has larger and more efficient ports, then an even greater potential for power production could be achieved.
Thats one hell of an essay...The valves are exactly the same size as well as the exhuast ports. Also noone has swapped an evo head onto a stock block and the pistons in the stock block do not have valve reliefs so it's hard to say if it wouold even work. The kia head does have a larger combustion chamber it's 56cc the evo head is 43cc.
 

·
Registered
Joined
·
1,690 Posts
Thats one hell of an essay...The valves are exactly the same size as well as the exhuast ports. Also noone has swapped an evo head onto a stock block and the pistons in the stock block do not have valve reliefs so it's hard to say if it wouold even work. The kia head does have a larger combustion chamber it's 56cc the evo head is 43cc.
Yeah, I tend to be long winded...sorry about that. Okay, so the valves and exhaust ports are the same...in that case the Kia head might be the route I take. I plan to P&P the head some myself anyways (including gasket matching at least the intake.) I'm still torn on how I want to build the bottom end, and whether or not I want to use FI or stay N/A...I guess those will come with time. I definitely want to swap to a DOHC setup though.

Just to ask a question though, a Kia head will work on a stock bottom end with no problem (if I understand it correctly), and you say that no one has swapped an EVO head onto a stock bottom end, but they both have the same valves (and I would assume the same valve geometry since you can install EVO cams in a Kia head), then why is it that there might be clearance issues with an EVO head on a stock block? I might be reading too much into it though...maybe its just that no one spends the money on an EVO head if they're running a stock bottom end. I understand we don't have valve reliefs with the stock pistons, but if the only difference would be the size of the combustion chamber, then geometrically speaking it should work...I guess that's where checking your clearances comes in. For those who have the Kia head with EVO cams, have you had any clearance issues with the stock pistons? Same goes for anyone running aftermarket cams...does anyone know what size cams we could get away with on our stock bottom end before we push a valve into the piston (I'm thinking of looking at the 264 or 272 cams that are out there).
 

·
MINI by proxy
Joined
·
4,408 Posts
Discussion Starter #85
I'm no stranger to long-windedness, but I think I may have just been outdone!! :lol:

Seriously, I appreciate your taking the time to add your own take on things to this thread. I haven't the time to read it all at the moment (work doesn;t want me going into overtime), but I'll be reading into the info you've provided in depth. I'm sure you've provided some nuggets. :bigthumb:
 

·
Registered
Joined
·
1,690 Posts
Hey, I just thought of something. Am I correct in assuming that the Kia Optima engine is built by Mitsubishi? I know this seems like a pretty retarded question, but since I'm actually in Korea, the land of the Kia, I'm just wondering if I might be able to pick up some of the parts here. If not, I'm thinking about having the Kia head and intake shipped out here so I can work on the P&P and have things ready to go when I get reunited with my car in a little under a year...fortunately, shipping here is about the same as it is within the 48 states since I have an APO address.
 

·
Engineer/Realist
Joined
·
4,999 Posts
Also noone has swapped an evo head onto a stock block and the pistons in the stock block do not have valve reliefs so it's hard to say if it wouold even work. The kia head does have a larger combustion chamber it's 56cc the evo head is 43cc.
great, so i AM the first one to do this?


This is a pic I took of the stock pistons at the very top of the stroke. I highly doubt there will be valve clearance problems with the EVO head on a stock bottom end.
thank you flash. do you have anymore pics like this?
 

·
Registered
Joined
·
73 Posts
Speaking of the 4G64 Evo in D-sport... why is everyone worried about getting a kia head over the evo 8 head? That car made over 700+awp!

Seems to be a moot point. Only logical thing i could see is that the KIA head is cheaper.
Because lower compression makes it more boost happy

What would most likely be better then placeing an optima head on, is do a 4G63T head converstion. This can be done with minimal internal engine mods. All that really needs to be done is the extra holes to be filled. The 1G head will give you DOHC and more cc's, plus with a 1G or 2G ECU (for turbo knock) you can easliy turbo charge the 4G64 (4g63T stroker). :) Then again...im no expert...
1g and 2g Engines are rotated 180 degrees from the 3g's, Evo 4-8 or 9 (not sure if the 9 works) fit on the 3g's. Evo 1-3 work for 1g and 2g but I dont think its just a direct swap

Yeah, I tend to be long winded...sorry about that. Okay, so the valves and exhaust ports are the same...in that case the Kia head might be the route I take. I plan to P&P the head some myself anyways (including gasket matching at least the intake.) I'm still torn on how I want to build the bottom end, and whether or not I want to use FI or stay N/A...I guess those will come with time. I definitely want to swap to a DOHC setup though.

Just to ask a question though, a Kia head will work on a stock bottom end with no problem (if I understand it correctly), and you say that no one has swapped an EVO head onto a stock bottom end, but they both have the same valves (and I would assume the same valve geometry since you can install EVO cams in a Kia head), then why is it that there might be clearance issues with an EVO head on a stock block? I might be reading too much into it though...maybe its just that no one spends the money on an EVO head if they're running a stock bottom end. I understand we don't have valve reliefs with the stock pistons, but if the only difference would be the size of the combustion chamber, then geometrically speaking it should work...I guess that's where checking your clearances comes in. For those who have the Kia head with EVO cams, have you had any clearance issues with the stock pistons? Same goes for anyone running aftermarket cams...does anyone know what size cams we could get away with on our stock bottom end before we push a valve into the piston (I'm thinking of looking at the 264 or 272 cams that are out there).
The valves are at the top of the cylinder and because the chamber volume is less the valves start out closer to the pistons. Im not sure, but i think that the valves clear the pistons without any issues

I like the way you did this thread, but i wish you could finish it, i see that its been a loooooong time since you posted anything new
 

·
Registered
Joined
·
4 Posts
I have been doing a lot of research on this and I can't seem to answer my biggest question. Will my stock pistons from my 4g64 sohc block hit the valves from the 4g63t dohc cylinder head?
 
81 - 100 of 106 Posts
Top