i had this idea while driving and thinking about the KA with more displacement

but what would happen if you put shorter connecting rods in the KA i figure if you bore out the block that should be about 100 or so cc's (i really have no idea on this technical stuff i just get ideas) then shorter connecting rods and a very small turbo to spool up at like 1300 rpms to compensate for the loss in compresion and a second larger turbo to continue boost when the smaller runs out of pressure (does something like this acctually happen turbos spool too hard and stop making boost?)but if this were possible couldnt you have a KA24DEand turn it into something like a KA30DETT???as long as the timing is the same i figure the valves wont get sucked into the block but i could be wrongand also i figure your not moving more air just the same amount but lower down and with almost no compresion if so i would rather do this then any CA18 or SR20since of course there really is no replacement for displacement

Displacement is the volume from the piston from Top Dead Center to Bottom Dead Center. So if you shorten the rods lenght you do not add to the displacement. Only if you lenghten the crankshaft will you add displacement. You will be increase the overall combustion chamber, but really won't add too much power. I would only change the rod lenght to change compression. IMO the best turbo set up is a single turbo, (well except in a V engine.) On the KA engine you really can't strock or bore, maybe just a mm of bore. I have seen a 2.1L Ca and a 2.2L Sr. But really for how much this stuff would cost IMO I spend it on a Ball-bearing single turbo set up.

but if you have a turbo to compensate for the added volume wouldnt it just be like having more displacement even though the volume isnt displaced (do you understand what im saying cause i dont know if i do) and the boost presure from the turbo would somewhat mechanically act as the head and replace the empty space to bring your compresion up to 8.5 to 1 wouldnt it???

also if you increase the overall compustion chamber arent you hypothetically adding more volume so in a way it would be litterally like haveing a bigger engine

Like s13ka24 says, shortening your rods will not increase displacement since the stroke stays the same. Increasing the bore at the same time would be moving your motor more toward a square configuaration making it more of a high RPM screamer.The displacement increase as well as the cost would not be worth it. Shortening your connecting rod by a very small amount can drasticaly affect your C/R. Also, a short rod increases your rod angle which in a general sense is driving your piston laterally instead of vertically (scrubbing off power) which is not what you want. Long rod motors, again in a genral sense, tend to be better producers of low end torque then short rod motors.For my money, buy a DE and turbo it. it will make more power than you know what to do with (provided you spend the money).

thanks i just had an idea for a 3 litre 4cyl turbo but if the angle of the rods varies too much i can see why that would be a problem i guess i just still dont under stand how it wouldnt increase power if the turbo made up for the loss in compresion

You always want your piston to come as close to the top of your engine as you can, while maintaing the CR you want. if you leave the stroke, and change the rod to a shorter rod, say 3.65" instade of 3.78" you would kill your CR, also not having your piston coming as close to the top of your engine, you would not fully clear the exhaust gas from the engine. the only way to change the rod length, is the get longer/shorter pistons, or to get a difrent crank with a difrent stroke.

The only thing i would do is to have a custom Crank made that would lower the displacment down to 2.2L the try and over bore as much as posable so get the engine as close square as posable, but would must likely only be able to over bore to 2.25L. also here is something just to get an idea of the stroke of a KA engine VS other engines.

...............Bore X Stroke (in.)KA engine - 3.5 X 3.78SR20de(200sx) - 3.23 X 3.68VG30de - 3.43 X 3.27VG30dett - 3.59 X 2.99VQ35de(350z) - 3.66 X 2.89LT1 vette - 3.9 X 3.62

SeSS4oIL wrote:also if you increase the overall compustion chamber arent you hypothetically adding more volume so in a way it would be litterally like haveing a bigger engine

increasing your combustion chamber will drop your compression ratio, but will do nothing for your displacement. an engine's displacement is determined by the engine's bore and stroke.

-demetrius

SeSS4oIL wrote:thanks i just had an idea for a 3 litre 4cyl turbo but if the angle of the rods varies too much i can see why that would be a problem i guess i just still dont under stand how it wouldnt increase power if the turbo made up for the loss in compresion

The rod angle has nothing to do with displacement either. While shortening the rod would effectively reduce the compression ratio, you would lose the quench area at the edge of the combustion chamber. In a Modern motor, the piston comes very close to the top of the combustion chamber. The head is typically designed with quench pads around the outer edge of each combustion chamber. This quench area has such a thin layer of volume it does two things. 1) it pushes the mixture closer to the center of the combustion chamber to promote a more powerful and efficient burn. 2) because it is so thin, any leftover mixture in this area is less prone to detonation as the metal is much cooler then the mixture and there is only a small amount of space there. There is a boundry layer near all the metal surfaces inside a combustion chamber. This boundry layer of air and fuel does not ignite. It actually helps to cushion any detonation as well. At TDC, when the quench area is the smallest, it is very unlikely to see detonation in this area. TDC is the time when a motor would probably see the worst detonation and protecting the ring lands would be a priority since this is one of the weakest points of a piston. Shortening the rod and creating more space between the head and the top of the piston would reduce or eliminate the quench effect and ultimately work against this technology. You could find yourself with a motor that is more prone to detonation as a result.

While lowering compression would allow you to typically boost more(provided fuel requirements are met) and gain more power, but the proper way would be to use lower compression pistons.

Lastly, I'm not convinced you understand what displacement is. Here's a lab experiment from back in high school science. Fill a glass of water to the top. Drop an object in. the water is displaced by the volume of the object you dropped into the water. In the same sense, displacement of a motor is how much air, the piston will push out of the combustion chamber when moved from the bottom of it's stroke to the top. By changing the rod length, all you do is change the position of the piston. The same volume of air would be displaced by the piston. Since the distance from the center of the crank journal at it's lowest point to the distance of the center of the crank journal at it's highest point still remains the same, the piston will always travel the same distance, given the same crankshaft.

and who would cast a block for you? since its impossible

the first idea is impossible i mean

how exactlly do you build an engine to run high boost20lbs??and what would the cost of a chevy 350 be to a built CA20DETcomparable in horsepower and torque?also i think ive heard of jun building a head for you? is this true?

actually scratch that how much can someone tell me if the murano is in japan, will it be, or is it just here in america if it is in japan how much for a the CVT and 3.5 v-6

the murano's engine lays in the engine bay the wroung way

SeSS4oIL wrote:and who would cast a block for you? since its impossible

Perhaps someone you pay a lot of money to. It probably won't be very cost effective though. You should be able to get plenty of HP out of existing motors.

SeSS4oIL wrote:how exactlly do you build an engine to run high boost20lbs??and what would the cost of a chevy 350 be to a built CA20DETcomparable in horsepower and torque?also i think ive heard of jun building a head for you? is this true?

There is not one single recipe to do this and is also dependent on many other things.

Not sure what you mean by your question about the 350 and the CA20DET(does this even exist?). If you are asking how much it would cost to build the CA20DET to have the same HP as a Chevy 350, it depends as well. I would not focus a lot on matching the Torque though. HP is a function of torque and RPM, and higher revs can make up for a lack of peak torque since you will have more leverage in higher RPM's. Cost will depend on how you build it. Again, there is not one way to build a motor.

As far as the heads, I do not know if Jun works on CA motors.

How about just a simpler idea, 8.5:1 custom CR forged pistons. make a custom exhaust manifold that routes cylinder 1,3 to a small T28, and cylinder 2,4 to another T28 avoiding the complicated sequential setup. Both T28 will use one IC, the only one hose connects to the intake manifol. That willseem[?i] to be a easier, more cost effective setup idea.

The duel turbo set up will make your pipeing a mess and will be hard to do. A single turbo is easier, more cost effective, and better IMO. Plus look at other cars, I have seen just as many single turbo RX7 and Supra's than I have seen twin. Single turbo IMO is just better.

what about the denso sard supra that is a four cylinder (twin turbo i think) and a similar head design to the CA18DET with the cam directly above the valves (also am not sure about this but ive read in posts)isnt that why the CA revs so quickly to 8,000 rpm?

also the twin turbo single turbo thing im stuck on it does seem to be cheaper for the output but my question on the turbo itself is still another problem for me i know you can buy turbos in sizes (dont know the model #'s)but a turbo that starts to make boost somewhere below 2,000 rpm would this turbo continue to make boost past 6,000 rpm?? or would a bigger turbo be needed for high rpm boost cutting out the low rpm boost? preferably i want extremly low rpm torque and continual boost to the red line (mabye 9,000 on a well built CA)

with this problem in mind i came up with the twin turbo 4cyl

or would a centrifugal S/C be right i know for a fact S/C create boost right away being turned by the crank but then your losing power to make power and with a turbo extra horse is a freebie

so how do i solve this problem?

also sorry i left out the part about i want jun to make a KA dual cam head with the design of the CA head (cam ontop of the valve) and thanks for all the help

i'm locking this one because you need to do some research on your own as to how things work (engines and forced induction).

-demetrius