SR20sleeper said:
w00t. i will be building an NA KA. im actually pretty set on this, 2.7 stroker kit, GSX-R ITBs, JWT cams, Supertech valves and lifters, port and polish, balance and blue print, Custom Headers, test pipe and blitz nur spec-r. plus other little stuff i can do. it should give me like 250whp and who knows how much torque.
Since I can't drive much with my clutch being down, i've been writing books lately. This feels like my earlier days on this forum where I use to get really dorky with cartalk. :gaylaugh
I was considering doing a n/a irtb setup with the miata, incredibly popular in japan for this car and it's finally catching on in the u.s. at first the numbers seem reasonably close to a turbo kit if not cheaper in cost. . . . . It's still a realistic and practical setup for the car since the power-weight ratio saves it in the end, but actually becomes much more expensive and complex process than forced induction.
Once you're figuring out exactly everything you need for a worthy setup to make full use of those irtb's, in reality. . . it is actually more like a $10k+ engine setup after everything is all said and done and thats a rough estimate for a standard I4(far cheaper for hondaboys,this is an area where they have everyone beat), perhaps more for the ka when dealing with the issue of not being able to rev high and there not being a big hardcore n/a aftermarket. What I find troublesome is finding a person that can locally tune I4 irtb setup. Currently thier's a guy in north cali who has a 240hp street ka which is modded to the guills, there are engines above that power rating but they are usually race only and vague dyno sheet examples of these engines.
You can have an irtb kit that costs something like $2300, or a diy system and use the donor irtb's from gsxr's, honda cbr1000/fireblade, toyota ae101/ae111 but you'll need adapters(jubride is popular for many applications),fuel rail,air horns and devise a throttle linkage system and get a custom intake manifold.
IRTB kit=$1700-3k
Full stand alone customizeable ECU= $2000+
STROKER KIT=$2000-3000?
ARP head and main stud kit $289
Valvesprings and retainers $319
Valves $319
Port+Polish=$600
CAMS=$500
7-8lbs FLYWHEEL+CLUTCH$700
Headers=$500 or more especially if custom which can be upwards of $1k
Full exhaust=$600
Blueprinting=$700?
Injectors $500
Reputable stroking and or bore job=$1k
Custom intake manifold=$1k?
This is just a rough estimate, you'll need maybe more parts or less but the rule of thumb is you take your calculations and add lots on top of that

lol. You never want to be in a tight financial situation, or else you'll find yourself half assing stuff or having lots of downtime and having an end product that wasn't true to your vision.
With the usual I4 IRTB setup you'll usually see them mounted straight on the head with a minimal length and near straight forward intake manifold...with a setup like this, peak power and tq will start at a very high rpm range. A bored/stroked KA(or any ka for that matter) is not going to spin happily to say 10k rpms or whatever rediculously high rpm number the typical or ideal I4 IRTB setup would make peak power at. What you'll want to do is get an intake manifold that could extend the runner length to say something like 15,16 or even 17 inches??, which can help bring your peak torque down to a more feasible rpm range for the type of engine the ka is. The key elements here to making attainable real world power or the type of power that you want for your situation will be irtb horn lengths and throttle body stacks, and the length of the intake manifold runners in addition to the engine mods that will support it all. The end product is an entirely different engine.
I don't know a whole lot about a hardcore n/a ka setup, though according to how a typical I4 irtb goes and knowing the ka's current powerband and stroke you can come up with some good theoretical conclusions.
The main purpose of doing a hardcore n/a irtb I4 setup is to gain a more immediate throttle response in addition to a more usable powerband, motorsports ideal for this application would be auto-x for example where having immediate and fast increasing power at any given moment is much more important than a peak number that takes longer to get to and you will probably never hit on the course. The focus here isn't to make peak hp or tq numbers or even high numbers period. The main reason why most people do a hardcore n/a setup with engines that are usually deemed to have an impractical money to power ratio for many is because they are forced to do so if they want to stay in a certain class of a sanctioned racing association like scca: csp class.
My closing for this book will be another smaller book:
What will
I be doing with my car
What kind of power do
I need and or prefer
How will this fit my spending and what are ways to compromise? this can go as far as changing driving styles and or gaining skill.
Take your sweet ass time and stay with what you want to do, don't let others that rush to get parts on for more or less the purpose of showing off sway your plans. Many people come up to me and ask, well hey man why don't you have more mods or how come your car isn't this or that or you should get this etc. . . in reality the car embarasses many in stock form, power to weight ratio is still greater than many comparable cars that are modified and even to my surprise from doing auto-x i'm still learning how to drive it and last but not least i'm a college student that pays for his own car,insurance and tuition out of his pockets. That's an example of how most people will not know the details or reasoning behind your decision and what you truly want and why you shouldn't change your plans otherwise.
In the end it is your car, so you could just say screw what everyone else thinks i'm doing what I wanna do.