1. big bore vs long stroke for 2.4l, which one is better? What are the pros n cons of each of them?
2. high compression piston vs hi boost piston? Since I not going to use nitrous which is better? Can I run high boost(1.8bar or 26.1psi) with standard compression ratio(8.8) or 8.7 ratio?
3. is that have higher rod / stroke ratio, the rpm easy rev to high rpm(7k – 8k)? with 1.5 ratio can the engine rev to 7k – 8k?
4.if the engine make 500hp in 98 octane, how many hp the engine run when in 97 octane?
thank q

 

1.) No idea what your talking about. You cannot overbore a 4G63 to 2.4L. You have to stroke it (giggle).

2.) The whole High compression vs. Low compression debate basically narrows down to this: with high compression you will make more power and have a more linear power band, however the room for tuning error is very small and the risk for engine damage is much greater (when using forced induction + high compression pistons) With low compression you will be able to stuff tons of boost + nitrous down your engine's gullet and be able to get away with some tuning mistakes without grenading the engine immediately.

3.) Read this:

The amount of power output generated by a four-stroke engine is ultimately limited by piston speed, due to material strength. Since pistons and connecting rods are accelerated and decelerated very quickly, the materials used must be strong enough to withstand these forces. Both physical breakage and piston ring flutter can occur, resulting in power loss or even engine destruction. Piston ring flutter occurs when the piston rings change direction so quickly that they are forced from their seat on the ring land and the cylinder walls, resulting in a loss of cylinder sealing and power as well as possible breakage of the ring.

One important factor in engine design is the rod/stroke ratio. Rod/stroke ratio is the ratio of the length of the connecting rod to the length of the crankshaft's stroke. An increase in the rod/stroke ratio (a longer rod, shorter stroke, or both,) results in a decrease in piston speed. However, again due to strength and size concerns, there is a limit to how long a rod can be in relation to the stroke. A longer rod (and consequently, higher rod/stroke ratio,) can potentially create more power, due to the fact that with a longer connecting rod, more force from the piston is delivered tangentially to the crankshafts rotation, delivering more torque. A shorter rod/stroke ratio creates higher piston speeds, but this can be beneficial depending on other engine characteristics. Increased piston speeds can create tumble or swirl within the cylinder and reduce detonation. Increased piston speeds can also draw fuel/air mix into the cylinder more quickly through a larger intake runner, promoting good cylinder filling.

An engine where the bore dimension is larger than the stroke is commonly known as an oversquare engine, and such engines have the ability to attain higher RPM. Conversely, an engine with a bore that is smaller than its stroke is an undersquare engine. Respectively, it cannot attain as many RPM, but is liable to make more torque at lower RPM. In addition, an engine with a bore and stroke that are the same is referred to as a square engine."

(taken from wikipedia)

4.) Depends on the engine, depends on the tuner, depends on the temperature outside, depends on what mods you have done.

 

About the same. On the same engine in exact same environment and scenerio the tune between 98 and 97 will be pretty much the same. The higher the octane the more aggressive the tune can be. This is where the power difference is. Going from 97 to 98 it'll be about the same. Going from 97 to 116 there is gonna be quite a difference.

 

maybe question have some problem! sincer our 4G63 have 85mm of bore, when we bore it to 87mm, will the stock 4g63 bore become to thin after that? how many mm metal left between the cylinder?

 

the 2.4 is a 4g64 block, normal piston for that motor and the normal crank (forged) for that motor.

the 2.3 is the 4g63 with a 4g64 crank and special (shorter, lower compression) piston for the longer crank.

the 2.1 is the 4g64 block with a 4g63 crank and normal pistons for the 4g64 (i believe).

now the pros for the 2.4 is it's acutally more displacement. it's running a normal piston which means all the ring lands are in the right place and the wrist pin is in the right place.

the rev limits of BOTH the strokers is the SAME, the crank lenth is the same so therefore the piston speed is the same. the piston momentum is a bit higher in the 2.4 so you might say the 2.4 is LESS rev happy but for all safety intents they're the same as you shouldn't go rev happy in either.

the 2.4 needs to be built with oil squirters added (just like the 4g64 block, the veins are there, they just need to be machined and have the squirters added).

i won't even answer your bogus octane questions cuz those are so unconventional i don' tknow what you're doin' runnin' them.

more boost = more power. more compression = less boost. you figure it out.

 

the displacement of the 4G64 block and 4G63 crank is 2.1liters, the pistons used are not standard 4G64 pistons. The stock 64' pistons have a flat top design with nearly non existent valve reliefs. Wiseco and MagnusMotorsports sell pistons specifically designed for that combo.

You dont NEED oil squirters in the 4G64 block. Oil squirters are a luxury. Not every manufacturer uses them, other motors without them make good power and last a respectable amount of time. Yes, you can add them, but its not mandatory.

As far as rev limitations, I wouldnt rev a 2.3 or a 2.4 past 7500 RPMs, 8,000RPMs max if your feeling really really dangerous. Magnus sells a long rod 2.4 setup which is said to allow you to rev to 8,000 safely.

As far as your compression question..... Too low a compression on the 4G63 is bad for a street car because it makes the motor very very laggy, the trade off is you can run more boost in general and more boost on pump gas safely. On the 2.3 or 2.4 motor, its not a bad idea to go with a lower compression if you have a street/strip car, because even if you went down to lets say 8:1, since you have more displacement, the motor wont have too much lag, it would still be respectable on a daily basis and you could run big boost at the track. I personally just started building a 2.4 with custom designed pistons made by wiseco for RRE. I must say these pistons are high quality and the design is very smart. My machinist took one look at the piston and the first words out of his mouth were "Man these guys really did their homework" He builds alot of 2.0, 2.3 and 2.4 mitsu motors and he has seen certain combo's fail and one of the most common problems is pistons breaking right between the valve relief and the top ring land, because there isnt much material in between, well the RRE piston design takes care of that problem. This is nothing new tho, I have seen pistons by JE and Arias with the same changes, just in the 2.0 liter variety and not for the 2.4 like mine.

 

**** good call on the 2.1, i don't know why i typed that.

the oil squirters are what's in the 4g63 so if you want to maintain the "coolness" of the 4g63 it's prolly better to have them.

 

Wikipedia is wrong

 

thanks for ur info. they are very useful 2 me. May i ask which block you using to build 2.4motor? Can i use 4G63 tming belt when i using adjustable cam in 4G64 block?

 

I am using a block from a 01 Eclipse. As far as the timing belt, I have heard you can use the stock EVO belt, however the "correct" belt to use is the one from a 94 Galant GS, that is the only 4G64 motor that was DOHC. I was told to use that belt by both SBR and Magnus motorsports.

 

How?

 

You could also just overbore a regular 4G63 block (and use regular 4G63 crank) to obtain 2.1L or slightly higher.

 

You can do that. However the objective of the 2.1 is using the 4G64 block with the taller deck and larger bore to achieve a lower piston speed which allows you to rev higher safely. I think its a great concept, however high revving motors are more prone to break then those being spun to a lower redline, thats why I opted for the 2.4. Plus high revs are not drive train friendly.