| Picking a block - Click HERE for Original Thread |
| autot |
| Not sure how to word this to get the answer I'm looking for, but here goes. Say you have 3 identical engines from everything but the internals. One has say an 86mm stroke and a 95mm bore, one has a 86mm stroke and an 86mm bore, and one has a 95mm stroke, and an 86mm bore. what is going to be the difference in the way these engines run?, now, let's add a turbo and exhaust to these engines. What now?? What does, say, a kenworth run for a bore and stroke? Please only respond if you at least have some idea of what your taking about.:cool: |
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| ChromeDragon |
Well the first engine will be extremely high revving, producing peak hp and torque in the upper RPM range(read Honda B16, B18, etc.). This platform is "oversquare." The second will be a compromise between power and torque. The engine will not create as much peak power as the first engine nor will it rev as high, but it will produce at least somewhat comparable torque if not more. This engine is "square." The third engine would produce high torque numbers and lower hp numbers. It would have a lower redline than the other two engines, but it will produce peak torque and hp at much more usable levels. Most diesel engines operate on this "undersquare" platform because they require massive torque at low rpm's to get the heavy loads they pull moving.
As for putting these engines in a vehicle, it all depends what you intend to use the vehicle for. Once you decide what you're using it for you will figure out how you would like to boost the engine.
Chromey
P.S. Was this a question because you plan on building an engine? Or just for general knowledge? If the former please let us know what you're trying to build and maybe we can give you some insight as to where you may want to look. |
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| autot |
| Thinking of building an engine ,likely a ka24de which has like an 84mm bore to a 91mm stroke. I want to boost it in the future and do some bot on stuff to start. I want to build it to smoke 5 litres and even c06 vettes one day. Looking for more of an acceleration type car than a top speed car, so the under square?? setup seemed to me like a good choice for autocross to me.??????:cool: |
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| autot |
| P.S. That was supposed to say, do some bolt on stuff.:beer: |
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| ChromeDragon |
Seems like you would be better off dropping in an SR20 or a CA18. The KA makes decent torque, but it's nothing spectacular. You'll spend alot more money making a KA fast than just starting with a turbo engine in the first place.
Chromey |
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| DeathBy240 |
| This could become a HUGE debate. If you are going to choose between an SR20 and a KA-T I would recommend going to NICO or freshalloy and searching for the topics where it has been discussed. It has been discussed in great length. NICO if you arent familair also has a section for turboing the KA which I am sure will help you. www.nissaninfiniticlub.net/forums and www.freshalloy.com |
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| ChromeDragon |
You can't honestly think that putting a turbo onto the stock KA block will be faster and more reliable than either the CA or SR. You would have to tear the engine apart and rebuild it with much more robust components and a lower compression. That right there is going to cost a whole lot more money than a stock SR20 or CA18, never mind having to get a turbo kit.
Why am I explaining this to you Dave, I know what engine you have...hehe.
Chromey
P.S. I would recommend checking out those sites though, very informative! |
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| MATRIX MOTORSPORTS |
Actually, the K-series engines are very robust in stock form. There are several shops in the US running 300+whp on stock internals. And I don't mean stock (except for......), I mean completely stock block! Best estimates by a friend of ours out east that does a lot of Honda builds, he figures that with rods, pistons, cams, and some boost, 550+whp is attainable. Hopefully we'll see, as parts availability and time go on, some quick RSXs will be come to light.
Krazy Karl
quote:
Originally posted by ChromeDragon
You can't honestly think that putting a turbo onto the stock KA block will be faster and more reliable than either the CA or SR. You would have to tear the engine apart and rebuild it with much more robust components and a lower compression. That right there is going to cost a whole lot more money than a stock SR20 or CA18, never mind having to get a turbo kit.
Why am I explaining this to you Dave, I know what engine you have...hehe.
Chromey
P.S. I would recommend checking out those sites though, very informative!
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| DeathBy240 |
quote:
Originally posted by ChromeDragon
You can't honestly think that putting a turbo onto the stock KA block will be faster and more reliable than either the CA or SR. You would have to tear the engine apart and rebuild it with much more robust components and a lower compression. That right there is going to cost a whole lot more money than a stock SR20 or CA18, never mind having to get a turbo kit.
Why am I explaining this to you Dave, I know what engine you have...hehe.
Chromey
P.S. I would recommend checking out those sites though, very informative!
Turboing the KA is not the way I would go, that is why I am buying an SR this week! It has been proven though that if you biuld the engine right, its got a lot of potential. But that puts you over the cost of an SR.
Karl, you got confused, we are talking about the 240 engine, the KA24(D)E, not the RSX engine. |
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| autot |
| I know all about the nico forum, and have studied a lot of them. In fact, there are a lot of people on there who have turboed the Ka24de completely stock with great success. Karl knows exactly what he is talking about. :p . This OBVIOUSLY isn't the place to ask questions about nissans, unless it's what is the best wing or seat covers to put in. Yes, the sr20det is an awesome engine, but there is a lot more to the swap $$$ then I think you realize. I would be going Ka24de,add the T later(tourque rocks, displacement on imports rock). It's more of a physics question than a debate topic though. Forget engine names, I want to know why those bore to stroke combinations work the way they do. I agree with you Chromey about the stats on over-bore/under-bore. But it doesn't make sense. It seems that there would be a lot more rotational mass with a longer stroke. You would need longer crank arms(what are they called that holds the connecting rod?) |
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| ChromeDragon |
There is more rotational mass with a longer stroke, therefore the engine is not able to rev as high. I'm not sure what you are referring to with "crank arms".
As for big torque in imports, I love it! I prefer to have the car pull down low!:bthumbup: |
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| DeathBy240 |
quote:
Originally posted by autot
This OBVIOUSLY isn't the place to ask questions about nissans, unless it's what is the best wing or seat covers to put in. Yes, the sr20det is an awesome engine, but there is a lot more to the swap $$$ then I think you realize.
There are a few people here that know a lot about nissans, and not about wings and seat covers.:p As far as the SR swap I know how much it is going to cost me, my brother did the swap last year, and I am very prepared. Don't be quick to assume we dont know anything.:) |
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| mitsuman |
quote:
Originally posted by autot
This OBVIOUSLY isn't the place to ask questions about nissans
You know, the internet is a big place. This topic has been discussed many times and in many different forums. Like others said, do some research.
Further more, cause it seems that you are new to the whole "engine building" thing. I would highly recommend starting out with an already turboed engine. The SR20DET is an formidable engine designed to be boosted, with lots of aftermarket backing. :bthumbup: |
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| autot |
| I have researched on the internet, but I don't only want opinions from people who live in cal. or Fla. I have also got a lot of good answers on this forum. The sr20 is a great drop in solution. I'm not interested in that. I repeat, this wasn't an opinion topic. Anyways. I understand the rev part of the longer rods on an under-bored engine, but is the length from the middle of the crank to the rod bearing.(what the hell is that section called????) the same?? It seems that it would be longer on the under-bored engine, therefore,creating a higher rotational mass, making it harder to create low tourqe. Any idea of a wedbsite to research these theories would be sweet.:cool: |
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| IH8V8S |
:dunno: Ooops! No wonder I was wondering why we were comparing K20s and K24s to SR20s. The rocks in my head have begun to move. :fingersx:
Anyway, here is another rendition on things; what you are refering to is known as the crank "throw", or how far the rod journal is from the main journal. This length has a lot to do with determining the stroke of the engine (the other part being the length of the rod). Now, if you have an engine with a large stroke (over-square), the rod has a higher mechanical advantage over the crank because it is pushing on a longer lever. This creates the "torque" associated with an engine with a large stroke. The fact that the rod journals are farther out from the main journals will add slightly to the rotating mass but only marginally. The biggest reason for the torque is the mechanical advantage.
The down-side to this is that with a large stroke you usually end up with a poor rod ratio. The rod ratio is most easily described as being the angle that the rod is at during the downward movement of the piston during the power stroke. If you have an engine with a large stroke, the rod will be at a poor angle to the crank as the piston moves down the bore. The less vertical this angle is, the less of a mechanical advantage the piston has on the rod. This can result in thrown rods and shifted sleeves in some cases.
Basically, all the angles etc. involved in an oversquare engine help it produce power at lower rpm but also limit the rpm range of the engine due to the rod ratio and crank throw involved.
My thoughts are, if you want to build a great autocross/daily driver type engine, the K24 with a fairly small T3 turbo would be the way to go. If, you are looking for an engine that makes a little more power but at the cost of higher RPM, go with the SR20. Either way you go the costs will be fairly similar. Hopefully this hasn't confused anyone. :confused:
Krazy Karl :beer: |
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| autot |
| It sounds likeyou got the whole mechanical part of the longer stroke and rod angle right on, but as far as the sacrifice of power on the sr20 at higher rpms, you contradicted yourself. Sr20 runs a square configuration where as the ka24 runs an under-square. 92mm stroke to an 84 or 86mm bore. does anyone have any evidence of thrown rods on the ka24???? I am very curious. Come on guys this is an awesome general knowledge topic on blocks!! Lets get some more feedback!!!! My opinion, which is NOT based on evidence, is that with good quality parts,(pistons,rods,and bearings, that the under-square(longer stroke than bore) is going to be better for any kind of racing other than a mile long run. whatcha think?????:cool: |
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| ChromeDragon |
I honestly don't see higher torque being the best for racing. I would prefer a car that makes comparable torque and hp numbers, the torque at a somewhat lower rpm(below 4,000) and peak hp up around 7,000. As far as import engines go that's not overly optimistic for a square, or close to square engine. It all comes down to the type of racing you are doing though. What do you plan on doing with your car?
Chromey |
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| ChromeDragon |
| NM, I just reread your earlier reply. Well with an auto-x car I would want a balance between high rpms and lower rpm torque. Higher RPM's to lessen shift amounts, decent torque so that the car can pull from down low....once again to lessen the amount of shifts. If you can operate the car in second gear with sufficient power for the majority of the track then you should do well. You can concentrate more on keeping traction rather than whether or not you should be downshifting. Then again maybe I'm just talking out my ass....:lol: |
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| autot |
| I see what your saying 100% Chromey. My theory(again this is not based on evidence), is that if your running an efficient lsd, good rubber and suspension, and you are putting the power to the ground, the only way I could see the over-squared engine being more beneficial is once you run out of room in 5th gear. Ya if you don't like to shift, OK. Here's a good question. What is going to be the difference throughout the rpm range???? Is it going to pull harder with the under-squared engine all the way to redline?? I would really like an answer to that WITH an explanation. |
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| ChromeDragon |
Well manufacturers typically place their redline at a point where the car is starting to lose power slower, then set the gearing for that rpm range. I'll state it to you in terms of my car vs the parents Bug(which sadly is alot faster). My car revs to 8000rpm and develops peak hp at 7000-7200, but peak torque at about 5000rpm. So between 5000 and 7000 the car accelerates quite nicely. The Bug on the other hand has a 5500rpm redline and develops peak power at about 5000rpm, with peak torque starting way down low at 1800rpm. Because it is an undersquare engine compared to my oversquare engine it does not rev as high, but develops peak torque at a much lower rpm and thanks to the turbo holds the majority(155lb-ft peak, stays above 150lb-ft to 5000rpm) of the torque in the useful rpm range. My undersquare engine develops less torque than hp and it's at a much less usable rpm for the streets. When you hit the track though it's a whole different story. The Corolla 1.6NA engine just loves to stay above 4500rpms(which is where the TVIS system is working....sort of a prehistoric Vtec). When you wind the bug out in the top end you actually feel power fall off before the fuel cut because the torque drops so quickly. I suppose the only way to really feel the difference is to drive two comparable cars with different engine setups and see which you like better.
So throw on some nice pants and a jacket and shine your shoes up, then hit the dealerships. Decide ahead of time which cars you would like to drive and give them a shot. 180hp in a VW Golf is completely different from 200hp in an RSX-S. You will be genuinely surprised how much faster the Golf feels with that kick in the pants torque, where as the slower onset of power in the RSX really pulls up high.
Chromey
P.S. If anyone else has some cars to recommend he tries, post em up! Preferably oversquare vs undersquare. |
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