fastpace

Hello to all, I was reading the post about the ka and the sr and I read about what cheater240 said about the bore/stroke and how it can affect the performance of the engine by either having a torquey engine like the ka or a high end power engine like the sr. I was wondering if it is possible to make the bore/stroke similiar to the sr bore/stroke even though there is a bigger displacement in the engine.
Thanks,

This is also cheater240 post from ka vs. sr topic.

I don't know what the bore/stroke is for the sr, but the ka is 89/96 mm. This motor is a stroker and that is the basis for its large torque numbers. The fact that my '91 redlines at 6900 rpm is amazing to me. I mean, with a 96 mm stroke, those pistons are really flying!

Generally, an engine with a larger bore to stroke ratio is preferred for high end power. This is because with a larger bore, bigger valves can be installed which promotes breathing. Now, a turbo changes all that. In fact, it almost negates it since you are artificially pushing the air in instead of relying on the atmosphere.
Anyway, I like to look at the total area under the torque curve. Huge numbers do no good if they do not last.

Boostaholic says his engine doesn't do much until ~3500. That leaves 3500-7000 rpm for driving use. That's not bad, but what about leaving the line? What I'm getting to is this, if you don't mind keeping the engine spinning really fast, then high end power is where its at for the race track. If your going to be running around town, then don't forget that low end.

But keep in mind that 3500 rpms is where the car knocks you into your seat and wont let you up. Even leaving the line and doing say 20% throttle, I dont use the turbo at all and still end up 20 feet ahead of every other "normal" driver. The turbo is still spooling below 3500rpms, it just doesnt have the same power as above, but I have a very large turbo. You have to feel it to understand it because it is hard to put into words, but I have no streetability issues with having turbo lag until 3500, and in fact I would like an even bigger turbo. But my 2 liter i-4 has enough juice w/o the turbo to get itself around just fine, and the only times its even an issue is right off the line, and I enjoy actually going slower than I could and "pimping" it around.

kitoro

just a question, i'm not sure if anyone can answer (or even if this question really belongs in this post) :

since the KA's engine is like torquey, and the SR's engine is high-end power crazy, is there any way to increase the SR's torque curve?
i mean, even off the line, the SR isn't bad at all, it still reacts like a KA at first, but power kicks in fast after 2500rpm, so ... any answers?

whateverjames

stroker kit from JUN makes the SR a 2.2L
and from what i remember, it ain't cheap <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>

but by stroking the engine you will loose alot of topend power.

kitoro

losing a BIT of top-end power is okay.. but if it's A LOT... forget it.... i don't like losing power.
i prefer keeping the power.
the high-end torque for the SR doesn't seem too bad. but i haven't been in the SR while we were racing (Nguyen showed me how fast it handled, that's about it) or haven't seen it race something wif high torque.. so i don't really know.
I prefer keeping the power over having torque.
anyone have a pic of the stock dyno curve for the SR? it shouldn't look too bad rite?

---

I checked out Val Lam's car (KA24DET).. very nice overall, but i have yet to see it perform...

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hey boostaholic, how much HP is ur eclipse running at the wheels?

I dont know. I plan on going to an AWD dyno fairly soon, but Id guess around 400. I have cams in my trunk that add 62hp and then my standalone combined with my 750cc injectors should be able to give me at least 50hp from how rich I run right now and get my timing advance up there. Once I get all my engine work done I want to be in the viscinity of 600hp. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>

Just to let you know how much high end you end up loosing, my car on the 2 liter motor will pull hard all the way to 9000 rpms if my valvetrain could handle it. With a 2.4 liter stroker motor, the hp starts dying off around 6500rpms, which to me is a HUGE difference. Ive got all the torque I need as soon as my turbo spools, and Ive found that very low rpm torque is overrated and really isnt that important at least to me. NA engines and turbo engines are completely different feel to them and you have to learn to drive both of them differently, but Ill never go back to an NA car, I cant, Im addicted to BOOST! <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=':D'>

kitoro

i've ridden in 2 boosted vehicles:
1) an 85 celica pushing 300hp+... soo fast (it had 300ZX brakes too! so neat)
2) Nguyen's SR20-S14

i luv boost, i luv the sound of turbo...

fastpace

so what yall are saying is that a smaller displacement engine produces more horsepower than a bigger displacement engine and the bigger the displacement the more torque you will produce? And also, does it really matter what kind of material the engine block is made from to produce a lot of boost?

I believe the KA block is made of iron...Iron doesnt dissapate heat as well as aluminum or other materials which lead to higher engine temps/intake air temps. The higher the engine temp the less effecient the engine runs, the hotter the oil temps become and the less the oil can safely coat the turbos which could lead to premature turbo failure. The higher the intake temps are the less hp the motor can make from the same amount of air and also the les air can be compressed by the turbo. So on a large level, it makes a difference. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>

kitoro

ooh neat neat neat!
i keep luvving the SR more and more...

96SEChick

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from boostaholic on 6:37 pm on July 30, 2001
I believe the KA block is made of iron...Iron doesnt dissapate heat as well as aluminum or other materials which lead to higher engine temps/intake air temps. The higher the engine temp the less effecient the engine runs, the hotter the oil temps become and the less the oil can safely coat the turbos which could lead to premature turbo failure. The higher the intake temps are the less hp the motor can make from the same amount of air and also the les air can be compressed by the turbo. So on a large level, it makes a difference. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>
</td></tr></table><span id='postcolor'>

Josh--I think this is one of the most informative bits of info given about the debate between KA &amp; SR. &nbsp;I don't think many people have thought about this aspect.

Not that it really matters now, but the SR has an 86mm stroke compared to the 96 of the KA

<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>

There are tons of pros and cons for both engines and way too many aspects of both to completely say whether or not 1 is better than the other, all in all it all comes down to your goals for the engine and your budget, plain and simple.

Jay Wood

Budget...I hate that word