CA intake manifold 2nd-ary butterfly's

[float_6969]

Ok, so here's the deal. I had to pull my manifold because it was COMPLETELY coated in oil. I'm assuming this motor spent alot of time in the high RPM's or had a bad PCV valve. Regardless, I had to pull it and clean it out. So so here is my question;

For the valves on the secondary manifold, the actuator is run on a vaccum and the valves are normally open. Does the actuator computer controlled, or just manifold pressure based? I think it's manifold based, but I'm not sure. What I really need to know is this;

At what points during the RPM range is the manifold under vaccum or pressure. I would think at the lower RPMS befor the turbo spools, the manifold would be under a vaccum, which is when you would want the valves to close so that you would have better torque. Once the turbo spooled, the manifold would be under pressure and the valves would open. If I'm way off, please let me know. Thanks!

[Oneor1]

i actually believe that the valves are shut at lower RPM's to increase torque and they then open up at 4k rpms. Could be wrong but i think thats how it works

[NeedCAforS13]

I think thats what Ryan was saying Rick;)

I would think at the lower RPMS befor the turbo spools, the manifold would be under a vaccum, which is when you would want the valves to close so that you would have better torque. Once the turbo spooled, the manifold would be under pressure and the valves would open.

Ryan, to the best of my knowledge you are correct with your statements...its based off manifold pressure... nothing computer related! now was there a point to your question or were you just making sure you understood how it worked?;)

Sean

p.s. emailed you about the coilpack man:)

[float_6969]

Just wanted a little backup to make sure I knew what I was talking about. It was late when I wrote that, so it kinda came out like a question. Sorry bout that. Thanks guys!

[Nismo1182]

Im going to remove mine before the motor goes back in.

I had removed them on my KA and got lots top end.

I'll get the torque back with a better turbo and engine management.

[iliketocrash]

you'll get it back with a better turbo? am i the only one who feels that doesn't make much sense? the the idea of the butterfly valve is to retain low end torque. I don't believe any turbo is gonna do anything to get that back if you remove 'em.

[float_6969]

The KA and CA secondary butterfly setups work totally different. Because the CA has a true 8 port intake the butterfly valves essentially turns the car into a 12 valve w/2 exhaust valve system down low. Once the turbo spools up and the torque is no longer needed the valves open and allow the motor to work like a 16v system. The KA simply restricts ALL of the runners and because it uses larger valves, they pose more of a restriction. I JUST got done tearing apart my intake manifold and I know for a fact that the secondaries on the CA aren't any bigger than a quarter, and are probabally closer to nickel size. The secondary's in the KA are closer to half dollar size. I can't seem to find the post, but TMS said that all of the guys in Japan running big HP CA's don't touch them because they don't pose that much of a restriction and they do help with the low end torque. With a motor like the KA with large displacement, and an over stroked setup, the need for the butteryflys isn't great. It's long stroke makes up for them if you take them out. But with the CA's small displacement and 'practically' square bore and stroke, they need them, otherwise it will be worthless down low and make it hard to drive. But thats just me $.02...

[boost_boy]

I took mine out of my newly built engine. I've operated the CA18DE with the butterflies stuck and the car ran like something was holding it back down low. I unstuck the butterflies and the car was moving nicely again. Since Iplan on seeing 25-30+psi of boost on this engine and because of the type of turbo I'm using, it's not going to matter; which brings up a very good point. If you put a true 60-1 turbo on a CA18DET, those butterflies mean nothing anymore. You're gonna lag thorugh the lower rpm range anyway until power comes on. Heck, if you're gonna be sputtering around with a hopeless T25, then you'll enjoy the full effects of the little butterfly valves. I say if you want low down torque, get a KA or an SR. But if you want an engine that makes you feel like you're really handling your business, put up with the fact that the CA is not the torquiest below 3000rpm and build to compensate for the deficiency like "Nismo1182" was trying to say in this quoteQuote »I'll get the torque back with a better turbo and engine management.[/quote] Because with a bigger turbo and better fuel management, you r power outputs will increase dramatically if tuned properly.

[float_6969]

Maybe I'll have to drive both and see how I like it. My only concern is that with autocross I need the broadest power band I can get. I don't know how well I'm going to be able to keep the motor in the boost with autocross. I'm hoping to gear it low enough to keep the boost up, but I don't need a laggy motor either, that would prob actually slow me down.

[quest]

FPbig28 or similiar, will give u that broad powerbandI have the uk version ca18det. No butterfly valves. My head ports are similiar to a 1st gen DSM. Aparently, these were the later production ca18det.... so nissan dropped the flaps. Oddly, these T25s had a 0.64 exhaust a/r. Motor is not as torquey as my dsm for normal driving, but it pins u back in the seat right now, when u step into it.The japanese 4g63 had butterflys too. The 2nd gen 4g63 went to smaller ports instead.

[boost_boy]

Quote »Oddly, these T25s had a 0.64 exhaust a/r.[/quote]That is odd. And they still rated this motor at 175PS? The DSM engines are torquey like the SR because of the longer stroke. My elantra with a high compression 4G63 rides hard out the hole, but seems to be more tame on the top end. My old CA18DE was kinda tame out the hole and really sick for a N/A 1.8l motor.

[Nismo1182]

I will remove the flap valves regardless. The motor is sitting out of the car so might as well do it now.

I hate restrictions anywhere on any motor. I removed everything I possible could on my KA and now its still a torque monster while having a more decent top end.

If I wanted torque I wouldnt have bought a CA. High end-high rpm power is what I likes

The LS1 powered Trans Am im getting later next year will take care of my torque problem.

[float_6969]

to each is their own I always say. And who knows. maybe later down the road I'll take them out on my next CA. But that one will be a rev machine so then I won't care about the low end. Right now I need a working motor. My poor ol KA just isn't gonna make it much longer.