newb here - intro and a few ka24de ?'s

[GSR]

First let me clarify that I am not new to the car scene, not new to forums or even this forums site, although I haven't visited in over a year. I am, however new to nissans. I'm a honda guy but due to recent "events" I am forced to reconsider hondas. I'd though about selling my honda and buying a 240sx about a year ago but what I wanted wasn't in my price range at the time (97-98 "shark eye" 240) so I though, i'll keep it until I wreck it or it's stolen. A few weeks ago, it happened. This was my integra 2 weeks before it was stolen:





It was totaled. As soon as the insurance check ($3500 is what they want to pay, which of course i'm not going to agree to ) comes in, I plan to get a s14. If I can afford a 97+ I will try, if not, I will settle for a 95.

Now on to the questions. Originally, following the bandwagon, I wanted to swap a sr20det but after reading your faq and a few other sites I'm leaning towards turboing the ka.

-what makes the sr20 a better high rpm motor? consider rod length to stoke ratio, block strenght and cooling comparisons
-what makes the sr20 a better boosted motor? I know about compression, that doesn't worry me. my gsr was at stock 10:1 compression making 300whp @ 9psi on a 57 trim t3/t03e (271whp on mustang dyno) with, I believe 20 degrees full advance.
-who has the most aftermarket support for ka-t's. cams, I hear they're a big problem if you want to rev

I'm not looking to make of this a ka vs. sr debate. I also don't want to hear "the sr20 is a better road race motor and the ka is a better drag motor." I want to know engine specifics that make the motor suitable for either. numbers would help. BTW, does anyone have flowbench tests of the different heads?

Lastly, I don't appreciate the hate against honda that seems to go around on this board. In my eyes, respect is well deserved. I came across a post earlier that read something like...there isn't a honda that could beat my car... for one that's a very ignorant comment. doesnt matter how fast you are, which i'm sure not very, there will always be someone faster. I know a geo, even a van that will dust a stock viper. I hate comparing numbers because theres always more to the story than what is said, but I remember last year a street trim crx driven to the local track, owned by an individual not a shop, went 9's without a wheelie bar on a relatively mild setup. That's an accomplishment. Give respect where it's deserved.... well, theres my rant.

[D-Bo]

sounds kinda like what my buddy did to his car.. got some friends to steal it, total it, set it on fire and everything.. so he got more than what the car was really worth from his insurance company..
i'm not saying thats what you're doing but i hope you get a ton for a 240.. welcome!

[GSR]

considering i didnt report any upgrades to the insurance what you are suggesting would be a very stupid idea. I'll get 5-6k if im' lucky from the ~10k I could have sold it for.

BTW, your "friend" is the reason why our insurance premiums go up

[AWDSR20]

GSR....... i have to agree with u on that one LOL, D-bo i think he took it the wrong way!!!LOL.

BTW, Sr20 is illegal dude! ? KA-t uhmmm don'tknow but i think it is (not helping am i?) (i have the SR20 but i got hook ups for the smoge)
anyways, READ THE FACT THING THAT IS POSTED ON THE FORUMS!


cool?

[TatII]

there is really no concrete evidence of the KA head flowing better then a SR head. but from what i've read in the past is that someone has spend almost 1000 on a full head and valve on the KA and got minimal gains in return. this is our assumption that the KA head flows damn good even in stock form. now compared to SR's we really have no clue. i'm pretty sure the KA head will flow better then the low port SR heads found in the S14 and S15 SR's. but compared to the high port S13 SR's the flow should be about the same.

what makes the SR a better boosted motor? well the only true reason i can think off is that it comes with lower and forged pistons right off bat. if you change the pistons on the KA to forged units then the strenght difference between them are a toss up.

the SR has a closed deck aluminum block, the KA has a closed deck iron block. the SR has piston cooling oil squirters, the KA has the same thing. both engines have forged cranks, with the KA having a thicker crank by the main bearings. again as mentioned the main weakness is the piston of hte KA. Ivan from performance and sound has taken stock KA's up to 400whp. and at this point is where the ring lands crack on the pistons from just the stress of the pressure, not from detonation.

the SR has a better high rpm motor since it rev's to 7.5 K stock and somes with a pretty small turbo. this gives it a power band thats around 4.5K broad. the KA has a better valve train since it has no rocker arms to fly out, but the KA has waaay more stroke then a SR. the SR's bore and stroke are perfectly even. its a perfectly squared engine.

the KA's piston bore is 89mm and the stroke is 96mm's. that compared to the SR's 86mm x 86mm bore and stroke, and you'll see that hte KA's stroke is a whole 10mm longer!! so therefore the head can support the high rpm's the rotating assembly unfortunatly cannot.

i mean you really can't go wrong with either engines. its just up to how you like to do things. it actually takes alot more skills to turbo a KA and keep it running compared to just swapping a engine thats already turboed from the factory.

[AWDSR20]

yeah get the SR,u will have noting to wory about. need more hp? slap on a bigger tubo. BUT the SR likes to float the lifters, mine are loud as hell. AND DON'T REV the motor PAST 6500! (stock)

[D-Bo]

if he had upgrades like you did then, no it wouldn't be a smart idea, but it was a grand am with no mods.. i never said what you did was the same thing he did. infact, i know it wasn't cause you wouldn't get a penny for you car for even a rim upgrade..
i've got another buddy who had his 94 accord exr actually stolen, with rims, new suspension, full exhaust, intake, headers and all, and he did't get a penny cause he didn't report any of it to his insurance company
i'm not a fan of people doing this intentionally cause it raises MY premiums too. this all happened long before i knew him too.. and long before he was smart.. now he's got a 93 corrado vr6.. sick car too.. this time he has reported everything to his insurance company but doesn't pay very much more cause he knows somebody in the industry..

[GSR]

d-bo, yeah i guess i misunderstood you. I'll be reporting anything i do to the 240 even if insurance is twice as much. auto theft is big everywhere but here in dallas, i know of 5 other friends who've had their cars stolen within a 3 week period not including mine. that shit is ridiculous.

thanks tatII. The stock forged pistons are definitely an advantage. about the ka's under-squared design, how does the bore:stroke ratio affect redline in comparison to rod:stroke ratio. I ask because the ka24 has an advantage on rod:stroke (ka=1.72, sr=1.58; approx 8.6% difference) while the sr20's has the advantage on bore:stroke (ka=0.93, sr=1.00;approx 7.6% difference). I've read about people revving ka's to 7.5k because of this. how do you feel about that? way too high?

Here's some dyno charts i found:

basically stock s13 sr20det


turbo ka24de on decent sized greddy 20g


Ignore the peak numbers and just look at the shape of the lines. I see a 3,000rpm powerband on the sr20 at most. Honestly I dont think the it's turbo is sized for performace; daily driving, yes. it appears to choke at 5k, thats a whole 2.5k before reline. I know many of you prefer low end tq over peak hp but personally, I like my motors to make power to redline.

btw, jesus look at that ka tq curve...or should i say line :o

[TatII]

hahah you should look at my old dyno sheet. that thing was a freaking plateau. it was flat from 4.5K to redline at 232whp and that was the lowest reading i got that night. i was averaging 240+ whp. but i wanted a conservative tune.

anyways most stock KA's do rev to 7K stock. the S13's have a slightly more aggressive cam design. this makes them breathe slightly better up top. thats why it revs to 7K stock rather then the S14's which only revs to 6.5 K. people who do light weight internals with nice aggressive cams can rev their KA to 7.5K since technically that is only going 500 rpm past redline. however making a KA rev to 8 grand ia a big deal. and not alot of people have done it.

the stock SR20DET can rev that 8K with rocker arm stoppers installed. and the reason why the peak power fell off soo much on that stock dyno sheet is because its only making 7 psi. raise to boost to 15 psi and look at the dyno then and the graph will look alot more different. mark here or Mynismo made 250whp on his stock T25. his dyno graph is in is sig! lolz.

anyways about the whole rod ratio thing, basically the engine with the longer requres to piston to travel a longer distance per revolution. lets say the KA has to travel 96mm from top to bottom, as it speeds up to around 7.5K the piston needs to travel a ridiculous speed to keep up with the revs. while the SR's strock is 10mm shorter. so the piston doens't need to travel as fast from top to bottom at 7.5K rpm.

the faster the piston is traveling th emore stress it will put on the rods, and rod bearing and rod bolts. the piston is literally wanting to come flying off the con rod. by reving a long stroke engine too high you will most likely spin a rod bearing and cause the piston to shoot straight thru the block. the engien jsut phyiscally can't be reved that high safely unless its got extremely light internals, and fully balanced, but there is still a limit of how high you can rev it.

my professor races pro stock. his V8's all rev to 8K. and his car hardly breaks. but when they give its freaking bad, he has a shit load of spun rod bearing with con rods ripped into 2 pieces with pistons with bit holes in them from hitting hte valve. his con rods are around 2 inches thick!!( 500 cubic inch engine ) and they still got torn in half.

[nissanfanatic]

Well in basic physics terms, centrifugal force allows the SR to rev higher. If you have a piece of string with a weight attatched to it that is 2ft long and a piece that is 1ft long, its obvious that you can spin the 1ft peice faster. And with a shorter crank, you have lower piston speeds.

Piston speed in Ft/min=(stroke in inches*rpm)/6

http://ka-t.org/ipw-web/bulletin/bb/...pic.php?t=1454

Theres an entire article on rod ratio and piston speed of the KA. Good read.

[GSR]

hahah you should look at my old dyno sheet. that thing was a freaking plateau. it was flat from 4.5K to redline at 232whp

i was actually referring to the torque curve in black ink. a flat hp line means your losing top end

I'm beggining to think that with only a cam upgrade, the motor will give a much better top end with little sacrifice of low end tq

whether boost was 7 or 15, the curve would look similar only in a different hp range. thats why i said, only cosider the curves. the tq would be high down low and decrease as the rpms rise

that link posted above supports my belief that a stock ka can rev much higher than its redline, I would think 8k is safe. remember a 1.75 rod lenght:stroke ratio is optimal for the least side loading on the cylinder walls. like mentioned in the thread above, honda's, lets say for example the b16 block with its 1.74 ratio, revs to 10k easily with supported valvetrain. if i were to build later on a skirt coating would take care of the added drag from the undersquared bore:stroke.

[nissanfanatic]

Originally Posted by GSR

i was actually referring to the torque curve in black ink. a flat hp line means your losing top end

I'm beggining to think that with only a cam upgrade, the motor will give a much better top end with little sacrifice of low end tq

whether boost was 7 or 15, the curve would look similar only in a different hp range. thats why i said, only cosider the curves. the tq would be high down low and decrease as the rpms rise

that link posted above supports my belief that a stock ka can rev much higher than its redline, I would think 8k is safe. remember a 1.75 rod lenght:stroke ratio is optimal for the least side loading on the cylinder walls. like mentioned in the thread above, honda's, lets say for example the b16 block with its 1.74 ratio, revs to 10k easily with supported valvetrain. if i were to build later on a skirt coating would take care of the added drag from the undersquared bore:stroke.

I like the way you think. There is an upgrade you can do that is supposedly very cost effective. You can use two S13 exhaust cams in the KADE. Supposedly it is worth about 15whp but most people say the power band extending is really the advantage to doing the cam swap. I think if the entire rotating assembly is balanced well along with different cams, the KA would have a very decent redline. Most of the power extracing for such a redline is going to be in the valvetrain. There are also secondary butterflies that can be removed. www.240sx.org has a write up on the subject.

[GSR]

Secondary butterflies? ka's have a dual runnder manifold design? I couldnt find it in the link you provided, do you have the exact url of the article? tia

[nissanfanatic]

Its not an exact url. Its under butterfly removal.

[MechManZero]

I am a KA guy so check out these sites as this should help you.

If you check out boostdesigns.com, they are designing a custom intake manifold with shorter runners and a bigger plenum. They specialize in KA turboing. They also offer stage kits.

Check out I-M-Racing.com even though they do have a lot of SR stuff over KA stuff.

A really good KA site is KA24DE.com. They have a decent variety of engine internal upgrades, fuel enjectors and even an Engine Management System which would give your car a chance to show you it's true power.

Hotimportperformance.com is right now fixing up their site but check out http://www.hotimportperformance.com/engineinternals.htm .