Hugh Posted November 16, 2004 Share Posted November 16, 2004 We should not argue about which is better, but let us see how the motor performs once it is built. Then we can make the comparison. BTW, is there a crank that has less stroke that can be swapped? I know a few 1.8L Honda motors that make 600hp@wheels so why is it not possible for a KA? The stock rods may be crap, but who runs stock rods in a 600hp SR? I have already begun work on the intake by chopping off the runners and decking them so I can send it to the machinist. He will port the manifold and then send it back so I can fab the intake. He will let me know the optimal runner length and then finish the wet flow bench testing. Let us see what happens. BTW, they are currently getting 350hp@flywheel N/A on these motors. 350hp NA on what motor? Quote Link to comment Share on other sites More sharing options...
karay240 Posted November 16, 2004 Share Posted November 16, 2004 350 NA HP!? Are you serious!? from the KA? About the Rods on the KA, I'm not talking about weakness of the stockers, I'm talking about how the rod ratio is no good for high RPM. That's why I'm saying a shorter stroke w/ longer rods. And to my knowledge, there are no carry-over crank that'll fit. . . and unfortunately, custom cranks don't come cheap. Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted November 16, 2004 Share Posted November 16, 2004 350hp n/a on the KA motor. Call Rebello and ask them what they are getting. From my understanding they are also getting in the 350hp range. My understanding was the rod:stroke ratio on the KA was 1.72:1. Why is that bad for revs? It is a better ratio than the KA Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 16, 2004 Share Posted November 16, 2004 Yeah, the KA motor likes to make all its power down low. I haven't seen anyone pull usable high-RPM power out of one yet. If they could shift the torque band substantially, the motor would see some ridiculous peak HP numbers. How exactly do they get 350hp NA from these motors? And what are they using them for? I'm not going to call anyone on the phone to ask them... how about a website or something, anything? Quote Link to comment Share on other sites More sharing options...
Guest tejas74260 Posted November 16, 2004 Share Posted November 16, 2004 alrighty, before it gets really off-track...can ya'll help me get a cost estimate of making 275-350HP on either engine while running on pump gas and having great response (turbo lag...boo! at least for street driving) i know theres a few things that i will HAVE to have for both motors converting them to my 260Z. Fuel cell (i want it becuase its just easier, and very easy to find the right one at the right price) EFI fuel pump and lines driveshaft (pretty sure the stocker wouldnt fit) LSD for my 3.90 R200 (the NISMO clutch-types are like $700, which is the lowest ive seen so far) Intercooler and piping: now here's where there will be disagreement as well. i wanna try to run a water-to-air intercooler thats mounted right in front of the motor so i dont have to run 6 extra feet of intercooler piping. i believe that will help significantly with boost response...and if i can get a setup where the temps can be very cold (like almost to ambient maybe)...i think that would be great. does anyone know if you can run a liquid like alcohol through a water-to-air and put dry ice in the tank to cool it? i've also been curious about those CO2 systems from CryO2...theres like a "fuel Bar" that the fuel lines connect to and the CO2 cools the fuel significantly in the line. if that can be adapted to the liquid i run through the intercooler...do ya'll think that would be worth a try? also, one more question...does an aftermarket S30 radiator (i.e. arizonazcar's crossflow aluminum) adapt to the SR or KA motors? thats another one. anyway, let me know what ya'll think about the intercooler setup and my other questions. if ya'll could come up with a setup with EITHER motor that would make up to 350HP thats streetable and include what components are used and the price that'd be awesome. thanks a lot Mark Quote Link to comment Share on other sites More sharing options...
karay240 Posted November 17, 2004 Share Posted November 17, 2004 does an aftermarket S30 radiator (i.e. arizonazcar's crossflow aluminum) adapt to the SR or KA motors? thats another one. it SHOULDN'T be a problem since all of your tubing/piping etc will have to be custom, and you're pretty much going to have to make due w/ what fits. Tha main thing w/ cooling parts (IC, radiator, oil cooler) is whether or not the capacity is enough. . . It doesn't matter if it fits, if it's not going to perform correctly. I'm not that knowledgeable on ArizonaZ products, and I don't know the cooling capacity. Find out up to what horsepower levels it's good for. This should be a good reference in your quest of the right radiator. Kenny http://www.rbmotoring.com Quote Link to comment Share on other sites More sharing options...
MrWOT Posted November 17, 2004 Share Posted November 17, 2004 I would go with the KA every time for a few reasons. 1st and foremost there is simply no replacement for displacement. It gives better drivability at equal hp levels and a MUCH wider torque band. 2nd, any mods you perform will give a greater power benefit due to said larger displacement. 3rd, I have no desire to have to rev an engine high to get big hp, that just shortens the life of the motor and stresses the piston pins and rods. 4th and last, the sr is just too damn common for my tastes The sr is a fine motor for what it is, however unless you're going to have your engine CONSTANTLY where it makes peak power at high rpm, the engine with the widest powerband will be the most enjoyable, hands down Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 17, 2004 Share Posted November 17, 2004 Too common? Every 240sx comes with a KA from the factory Quote Link to comment Share on other sites More sharing options...
karay240 Posted November 17, 2004 Share Posted November 17, 2004 I haven't heard of any 240Zs w/ a KA-t, though. . . It sure would be something different. I'm not sure why you're worried about low-end torque. Granted, on a heavier car, that may be an issue, but we're talking about a car that's probably goint to weigh around 2300 (maybe 2400 w/ assorted niceties in the car). It's going to weigh around the same as a miata!!! I really don't think that the SRs "lack of torque" is really going to be an issue here. . . I actually am warming up to the idea of the KA motor, though. . . it could be real nice Kenny http://www.rbmotoring.com Quote Link to comment Share on other sites More sharing options...
MrWOT Posted November 17, 2004 Share Posted November 17, 2004 It's not that the SR has inadaquate torque, but that the KA-T has an overwhelming potential with proper mods. Yeah, the rod/stroke ratio isn't all that great for circuit use, but unless you operate continuously at high rpm, who gives a hoot? Large rod/stroke ratios are not good in a street motor, the larger the ratio the higher the peak pressure because of piston dwell at TDC, which leads to detonation problems at low-mid rpm under full boost, so consequently you have to use a larger A/R ratio in the turbine, further hampering low rpm performance. Competition engines love big ratios because they spend all their time at the top of their powerbands, but you can run more boost with shorter rods then you can with longer ones. Heck, I've seen people with 2.5L ford SOHC motors, running less then a 1.5:1 rod ratio pushing over 400whp under 6000rpm on pump 93, so I imagine with a bit invested in the motor (rods and headwork), a KA-T could reach that. If you've ever driven a lightweight car with more then 400whp you'd know that it's pretty much suicidal to want more then that on the street without serious mods to the chasis like a roll cage, underbrace, etc... If you're building a circuit car, by all means use the SR, it's lighter and much more stable with less invested at continuous high RPM. But for street duty, displacement is king. Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 17, 2004 Share Posted November 17, 2004 Say what you want about displacement, the fact is, the fastest S-chassis cars are SR20DET powered. I go where the power is.. and the SR is making it. If you're building to 400hp, the amount of work required to make the KA take it is pretty intense. Or, you could just do it with a stock SR20DET. (like I did) Quote Link to comment Share on other sites More sharing options...
MrWOT Posted November 18, 2004 Share Posted November 18, 2004 Say what you want about displacement' date=' the fact is, the fastest S-chassis cars are SR20DET powered. I go where the power is.. and the SR is making it. If you're building to 400hp, the amount of work required to make the KA take it is pretty intense. Or, you could just do it with a stock SR20DET. (like I did)[/quote'] You seem to be missing my point... You are only referring to peak hp, I'm talking about using a motor on the street, not to drag race. The larger your torque curve, the more fun the motor is going to be on the street, period, unless of course you prefer to rev higher before reaching peak acceleration 8) Think about it, at 14.7PSI (1 bar) which is double atmo pressure, a 2.0L motor with 100% VE would act like a 4.0L motor, where as the 2.4L KA-T at 100% VE will act like a 4.8L motor at the same boost pressure, .8L is a BIG difference with equal tuning, consider the fact that if you push 100hp per L, like 200hp with the stock SR, that's 80hp over the SR. So if you compare an SR running 14psi and a KA-T running 14psi, there's no way the SR will have either better torque, or hp. The stock KA internals will take about 13psi safely without needing to change anything so long as you tune it right and avoid detonation. Anything past that would require forged pistons, just because at that kind of pressure, any detonation would have dire conseqences for stock cast pistons, would undoubtedly break the ring lands if it wasnt caught immediately. You are right though, the KA takes a lot of work to make a sucsessful racing engine out of, since it's not designed for high RPM like the SR. But if you're willing to spend about 3k on machine work and parts plus the cost of the motor, it will dominate, hands down. So what I'm saying, is that if you drive in traffic, on winding roads (since it won't be necissary to downshift to maintain acceleration), or don't like to rev high before accelerating hard, the KA is a better choice. If you're only interested in the top of your power band, and you do all your driving at a track, the SR is a better choice unless you want to fully prep the KA. Most people I know drive their cars on the street however, so would probably benefit from the wider torque band. But if racing is your deal, by all means, go with the SR if you can't afford to upgrade the KA. Quote Link to comment Share on other sites More sharing options...
Guest tejas74260 Posted November 18, 2004 Share Posted November 18, 2004 I'm on MrWOT's wagon...i just researched a lot on turbos (endless compressor map searching) and ended up finding a really good match that would be an awesome setup for street. since i would plan to run the AEM EMS on either setup...i think my upgrade plan would be comparable in price. i only plan to run about 14lbs of boost, but i'll plan on replacing the pistons and maybe having the rods shotpeened and fitted with some beefy rodbolts. also...i was thinking of having the crank journals micropolished (not sure if that's worth it) looking at other forums (especially ka-t.com) and they're all in agreement that with good tuning, its not really necessary to swap out the rods if you plan on less than 400HP..so i suppose i dont have to worry about that. i probably will purchase a "stage 2" kit from boostdesigns.com that includes a garrett t3/t04e 50 trim with a .48 a/r turbine housing. i'll tell them to X the intercooler, piping, and downpipe. it'll prob be about 2 grand for that...but anyway i'm babbling so i'll let ya'll say what you think Mark Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 18, 2004 Share Posted November 18, 2004 Well, actually the problem lies here: The KA doesn't like to rev. Sure, in the 300-400hp range, you've got a killer power band. If you take it over 400hp you start seeing a car thats basically fighting your turbo setup. It doesn't want to make massive peaks at high RPM, it spools the turbo fast and the turbo seems to outflow the motor at high RPM and you lose power. The SR20DET, on the other hand, just wants to rev way past its limits if you let it. (and your turbo is big enough to flow in that area) So on 500hp+ KA24DEt's, you see a very peaky power band that can't hold on long enough.. the motor can't wind out with the bigger turbos. Everyone says they'd take the KA over the SR just because of the displacement. If you're a firm believer that displacement is the deciding factor, then why would you take out the L28, or whichever motor your car had in it? Fact is, there's a lot more to the equation than displacement. My argument on the high horsepower build is this: I've seen numerous 700hp+ SR20DET's. Some in person. I've seen many over 500hp in person. I've built a few to 360-400hp myself, with almost completely stock internals. I read about a few 700hp+ in Option 2 magazine, as well as one over 800hp running 9's on drag radials. I've personally seen one KA over 500hp. It was awesome, but rare. I've only seen a handful on the internet... and last I saw they were quoting the record at 543hp at the wheels. I know someone who made 539hp and 540hp on two different stock block SR20DET's. I know another guy who made 550rwhp on a stock block SR20DET in an RX7 FD. A little headwork, cams, and bolt ons.. thats what it takes. As far as the narrow power band for the street discussion goes, how many of you who complain about turbo lag have actually driven a car with a big laggy turbo, and say 400-500hp? I have, a few of them. I owned one at 395rwhp. Lagged til 5000rpm, full boost at 5300. It was an insanely fun car to drive. I loved putting people in the passenger seat that were running their mouths about big turbo lag and this and that... and then watching them squirm to grab ahold of the door handle, holy crap handle, seat, whatever they could get their hands on... then they start laughing hysterically and uncontrollably. They get out of the car with a bewildered look on their face... and they never complain about turbo lag again. I drove two different RX7's with very big turbos on them. They lagged til about 5500-6000rpm, then took off like rockets. The first one I drove is what changed my opinion about turbo lag. I didn't care after that... it was enough proof to me that the car can have a narrow power band and still be insanely fast and fun to drive. Handling turbo lag is all in the driver. Once you learn how to cope with it, you don't even care that its there. For me, it gave me better gas mileage on the street, because I wouldn't drive around boosting everywhere I went. Once I spooled the turbo, I had to make sure I had no traffic in front of me, or I'd be all the way up someone's rear before I knew it! Sure, my power band was only 2000rpm or a little bigger... but I could drive my car dead on within this power band. Need transient response? Downshift, or go get a V8. Every turbo car lags when rolling in a high gear down the street. Once you know the power band, you deal with it by putting the car within that band. Not to mention, my car G-tech'ed several low 11 second 1/4's on completely stock internals, cams and all. Quote Link to comment Share on other sites More sharing options...
Guest 240zJake Posted November 18, 2004 Share Posted November 18, 2004 the car can have a narrow power band and still be insanely fast and fun to drive. Hondas are a great example of this...my Honda only makes around a hundred horespower, must of which occurs afret 5000 rmp... it s slowbut once that vtech engages and the engine howls, you cant help but smile I think I'd crap myself if it was five times as intense Quote Link to comment Share on other sites More sharing options...
johnc Posted November 18, 2004 Share Posted November 18, 2004 the fastest S-chassis cars are SR20DET powered If you're referring to an S30, you're wrong. There isn't a HybridZ (V8, V6, Turbo, SR, CA, etc.) anywhere on the west coast that's beat the L6 powered Rust Old Datsun's lap times at Thunderhill, Willow Springs, Buttonwillow, LVMS, Spring Mountain, or Phoenix. http://www.nsxfiles.com/otc_2004_day5.htm Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 18, 2004 Share Posted November 18, 2004 When I say S-chassis, I'm talking about the S13, S14, and S15. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 18, 2004 Share Posted November 18, 2004 When I say S-chassis, I'm talking about the S13, S14, and S15 Well then... I'm wrong. Quote Link to comment Share on other sites More sharing options...
MrWOT Posted November 18, 2004 Share Posted November 18, 2004 Well if you can deal with a 2000rpm powerband then go for it, but I've been driving around my ST165 for a few monthes now, it's got a 3S-GTE (2.0L turbo), and it's annoying as hell to drive around normally because of the 8.0:1 compression needed to run high boost and it only reaches real power from about 4000-6000rpm, but when it hits 4k, better hold the hell on . That being said, my previous car was an 86 SVO (2.3L SOHC turbo) and while the 3S makes more peak power (260hp currently vs. 2.3L 220hp) the 2.3 was much more enjoyable in the long run (around town and freeway) thanks to the wider powerband. It would reach full boost (18psi) at about 2800rpm (50trim t3 with a .63ar turbine housing), and would power all the way to redline at 6000rpm. It's kind nice to be driving along in 5th, get to a steep hill, and not have to downshift But yeah, the 3S gets along just fine as long as I keep the revs about 3500. Quote Link to comment Share on other sites More sharing options...
Hugh Posted November 18, 2004 Share Posted November 18, 2004 You've only got 2000rpm at 260hp? Maybe it needs tuning? An SR20DET at that power level can run for a few thousand RPM in power. Quote Link to comment Share on other sites More sharing options...
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