Intake manifold/KA TB discussion

What are the advantages of this.
Larger throttle body, 'front-back' intake(rather than over the top of roker)
Easier/shorter i/c piping... Anything else?

No, popup valve, intake for CA20E is better for high boost I would imagine, since it has a large plenum, and the CA18ET part is basically plenum-less. The CA18ET manifold is designed like it is for two reasons... 1. packaging is simple since there is no intercooler, and 2 it helps low end response and doesnt need a large plenum for top end flow since the turbo boost was never intended to run high on a CA18ET. That's also why the FJ20ET has large plenum intake manifold. They knew it could (and would) take more boost and airflow.

Have you finished the vacuum line connections for that intake mani yet? What year is your car, and what year was the CA20E intake mani from?

Yeah I stuck a KA24 60mm TB on my CA20E intake mani too and could port match it.

But I'm not sure a 60mm TB is good for our cars (listens to horrible gasps).

We discussed this on the Z car list for us L-series six engines, since they use the same TB's, and the KA 60MM is an "upgrade" like it is for us. It basically wont help you unless you are flowing massive amounts of air, otherwise it could even reduce low end response. Again I cite something I always preach on here... smaller port geometry means higher air velocities. You only need to go bigger when you outflow it. None of us, and I mean none of us, are outflowing the stock TB.

Yeah do get me a diag and most especially a list of the various connections and where they go.

HHHEEEEYYY I bet I can pull something here with my old CA20E diags with the numbers on them (remember those?) Only I don't have those as long as they old forum us down. Dan please what can ya do?? :)

i've got the ka and i quite dislike it. low throttle modulation is difficult and jerky and really half throttle is almost like full throttle. at first it's kind of neat because just a little throttle and suddenly you're flying but it's just like going wot on the stocker. and as you said, i doubt there are any power benefits until you're flowing lots of air. the det TB is probably a better match as it's not so large.

one good thing is the tps (which you can pull off and put on the stocker) for safcs.

i'd switch back but i modded my intake for the big TB so i'll have to make a new intake for the stocker. i think a lot of people who go on about the ka TB haven't actually installed one =)

I have a KA TB on mine and yeah it does some of the things you listed above but the thing I like most about it is that it doesn't have the stupid dashpot that the stock TB has. This allows the rpms to drop quicker when you get off the throttle which I like better.

I think too many people just assume a "mod" means "more power" and that's it. They never bother to stop an learn how exactly a mod is going to affect a motor.

They mix and match power mods without any kind of forethought. Anything that introduces MORE air kills velocity. Velocity makes torque. If you go to a larger TB, in all honesty, it shouldn't have much effect at all until the big RPMs, where the stock what, 35mm, can't flow enough. Stuff like boost dropping off, power loss at 5,200 rpm are sure signs of a choking intake.

Running issues, would have nothing to do with it. All a throttle body is is a butterfly. If it feels jerky or weird, odds are you moved the TPS or the KA TPS is sending a different signal. I used the stock CA TPS and have never had a problem with it.

On a relatively stock motor (at the time just MBC and IC) I didn't notice much at all until 3rd gear. If you remember a stock ca18et, 3rd gear is like taking your foot 1/2 way off the gas. And it wasn't a huge difference either ... just seemed to pull cleaner ... sounded better too. It used to sound kind of stuffed up. Coupled with decent exhaust, it made more power up high. It pulled cleanly to ~6,000 and strong.

All a bigger TB is going to do is allow more air. You could put a 4" MAF into your car too ... but it's not going to make you faster. And if you had the appropriate tuning device (like an SAFC) the car wouldn't give up any power, or run any different.

The biggest problem I think lies in the total lack of a plenum to begin with.

i think the size does matter at low throttle positions. the engine is small and cracking the big ka tb even a little allows a lot of air in (or stopping a lot of air flow if you close it) so you can get some jerky response. the tps should work fine if you adjust it correctly. you will definately know if it's not adjusted correctly.

i like the dashpot. it helps smooth out the jerkiness at when you close the throttle. it does slow the rpm drop tho. you know that you can adjust the dashpot right? once i discovered the tps is swappable from the ka to the ca i'm pretty much going to stick to the ca tb. of couse there is the bother of modding my intake for the ca again. bleh.

The biggest problem I think lies in the total lack of a plenum to begin with.
Hence why he, Kaz, and I are/will be using the CA20E intake, Matt. It has PLENTY of plenum ;)

Oh and what is a "dashpot"? SOmething i've yet to hear more on, and what is the difference/deal between the KA TPS and the CA SOHC one? WHich is better? And what is involved in running the best one? I think as far as throttle bodies go, I'm sticking with the CA body for better port velocity until such time as I am pushing 18 PSI.

Not that I will with a CA18ET. But who knows ;)

Oh and what is a "dashpot"?
Very good question...

the ca20e is not a better choice really ... the ca18et has a better runner design. The ca20e is nice because it points where typical FMICs go.

Now, if only I can dig up the picture from wherever it is on this site. I think it was 30PSI that posted it, but it might have been in a suspension post.

But he did exactly what I've been planning to do for a long time.

Take the ca20e runners, and weld the KAs plenum to it. They are similarly shaped, but the KA plenum is huge by comparison, and already has a 60mm TB on it.

Lemme dig it up.

The way I look at it ... the KA TB is designed for a 150hp engine. If a 150hp needs 60mm TB stock, keeping the stocker is not in your best interest.

And if you want velocity don't neck it down at the manifold. With such short runners, and no plenum, it's not going to be very effective. The air needs room to accelerate after a bottle neck.

I'll also try and dig up a really nice article on air velocity intake vs exhaust.

Gotta love when a car makes more power by going to a 2.5" reducer from a 3" exhaust than it did with 3" mandrel bent all the way.

Look into the Sonoramic Commando ... high tech, really amazing runner/exhaust design that pushed VE over 100% on a stock NA motor.

Just to give the nuts and bolts, over 100% VE on an NA engine is almost impossible. Basically it would mean making a naturally aspirated car under WOT actually generate boost over atmosphere.

Did I mention it was in the early '60s on a cast iron headed, cast iron intake, and cast iron exhaust manifolds?

Dashpot is the TPS. Or at least the potentiometer style.

The turbo TPS is just a switch.

Guys are running the KA's for the WOT signal switch to run the SAFC.

i doubt the manifold will much of a difference unless every last hp is important to you. ic choice will more likely influence the im type. i actually like the stock ca18et mani as it's not a log type. flow will be more equal to the cylinders. if your ic has inlet/outlet on the same side it works out to an extra 18" of piping and a 90degree bend. if you want a larger plenum you could always try a tb spacer. very simple to make.

the dashpot is not the tps. it's the small shock absorber on the ca tb. it only actuates when the is throttle almost closed. it helps against the throttle suddenly slamming shut when you lift and smoothes out throttle closure. the ka tb does not have this and transferring it is a lot of work.

the ka tps is a true tps. in addition to the idle/wot switch it has an additional harness that reads throttle %. the s12 does not need this however if tuning a safc it's nice to have as you can have high throttle map and low throttle map. (otherwise you are limited to a single throttle map). i'd highly recommend this for the safc as 3000rpm cruise is a lot different than 3000rpm at 10psi boost.

BUT.....

If you use MAP to control the AFC in place of the TPS, as I was saying in another thread, it eliminates the issue altogether.

At which point I see no reason to go with the pot style TPS of the KA. Oh and Matt, I state again to you that I don't plan to be plenum-less, via the CA20E intake mani (in reference to your comments on port velocities).

This post is getting pointless, and I'm sorry about that Travis.

As for an intake manifold being for every last HP ... that's ridiculous. Especially in a turbo application.

A TB spacer is not a substitution for an actual intake manifold.

Packaging ... it's all about packaging. Why invest all the money to run a big turbo, super exhaust, and then hobble your motor with a STOCK APPLICATION intake manifold and throttle body?

Big plenum means low velocity, but extra flow ...

If you want to run a stock intake, put the stock exhaust back on too. What's the sense in letting a motor breathe out but not in?

Sure, turbo cars needs free flowing exhaust, but without an intake to match, you're unbalanced.

The ca18et manifold is totally a low rise manifold engineered to help make torque over the long stroke of the ca20e.

As soon as you start modifying the ca18et (unless you want to mix and match torque vs flow mods for a slug of a motor) you have to give up torque to make power where it counts - in boost. By the time you're moving enough air to really get the car moving, your IM and small TB is holding you back.

The KA is under 150hp and Nissan decided it needed 60mm. Beyond that, the ca18det runs what, 58mm for 175? Both cars have big plenums too.

K, so then I'll switch to the CA20E intake for the plenum advantage, as well as orientation advantages.

Then, as I turn up the boost, I will swap out for my KA TB. Consider it "stages".

Well I've got it all already on my CA18ET and it works fairly well... unfortunately I do not have any actual information so show how much better... but I can say this...

I have the KA throttle body, and the CA20E intake manifold that is lightly ported at the flangeds and of course is ported to match the throttle body a little (I still need to do more, but got impatient, lol). I did it mostly for lower air resistance (ability to ingest more air through the intake) and orientation since I wanted to run a intercooler and hated the S pipe setups most people had fabricated (I know it works, but it seemed like a royal pita).

Anyway, it works fine on mine... w/ my T25 off a DET, I get FULL 9psi by ~2200rpms. And I'm sure I could go further on the boost, my wastegate just lets go at that point and lets off the excess boost... I've seen 12psi around the same range on a really cold night... torque is enough to completely squat the rear of the car... once I get the ground/spark/richness issues worked out I'll be taking it to a Dyno to get some actual numbers out of it, but its a pretty quick car... I have roasted many a modified Civics/Integras with my little S12... =)

http://members.cox.net/84200sx18t/200sx12.jpg
As she currently runs...

And to think you had the audacity to consider selling it! For shame!

meh... I still have thoughts... I think if I could get the suspension quirks worked out and getting it running well, I'd consider keeping it... I would still sell it if offered the right money for it... but I doubt that would ever happen... lol. I'm thinking about dumping some good money into it, to get it up to spec on things... we'll see...