intake manifold change needed for 4-500hp?

[niswiz]

was just wondering if i needed an uprated intake manifold or can i use the standard one and just port it out? any suggestions welcomed.

[float_6969]

There is a big difference between 400 and 500 hp. The UK guys say 350hp is the point where the stock intake manifold setup become restrictive enough to warrant addressing it. With that being said, I'd say that the stock manifold, port matched with the sub-manifold, should be fine for 400hp. 500hp is another story. I'm sure you can make 500hp on the stock manifold, but I'd be willing to be that you'd be giving up a good percentage of power to do it.

[blownhemi]

What is the actual restriction in the stock intake manifold? Plenum volume? Runner cross section? Throttle body flange cross section? The perpendicular throttle body flange?

[themadscientist]

The throttle itself is pretty dinky. The runners seem pretty roomy to me, at least up to the task of feeding the head ports.

[tommey]

You won't have any problems with reaching 550hp with untouched intake and a gt2871 for example. How much you would gain with a "better"intake I can't say.. the ones that's available on eBay isn't worth it anyway.

[float_6969]

I'd have to go back over to their forum and see if I could dig the threads up I read about it. IIRC it had to do with the TB (which is easy to fix) and plenum volume (it is a bit on the small side). There was also a back-to-back comparison of stock vs. CPC. I think they were in the 450hp range, on the stock manifold, and they gained 5% at peak HP, with no loss in bottom end. it's like anything else. If you're only making 200hp, 5% gain in power isn't worth the money. But you take that same 5% and apply it to an engine making 500HP, and it's a different story.

I seriously doubt anyone could find the point where the stock manifold actually completely chokes out and prevents you from making more power at all. It would be a rediculously high number. But if it's costing you 5%, there is a point where it's worth the cost to gain that power.

And to re-iderate, THIS ISN'T FROM PERSONAL EXPERIENCE!!! This is info I got from a few threads I read on another forum. Although the data seemed to be back up (with a dyno), I'm regurgitating this from memory, and my numbers could be off a bit.

[themadscientist]

I'm sticking with the stock manifold. The runners and plenum look more than adequate and setup properly to evenly distribute the air charge to each cylinder. I hogged it out for an SR20DE S14 throttle, though.

[niswiz]

yeah, i too have a sr20de throttle body which is 60mm compared to the ca18 50mm so that isn't a problem. was going to have a manifold built if the stock wasn't up to the task.

[float_6969]

I've considered having the stock intake mani extrude honed, but it's not far off in price from the CPC manifold, and that's a tried manifold with proven results. I know extrude honing the stock manifold will improve it, but by how much? I'm not rolling in enough dough yet to experiment.

[themadscientist]

yeah, i too have a sr20de throttle body which is 60mm compared to the ca18 50mm so that isn't a problem. was going to have a manifold built if the stock wasn't up to the task.

What problem? Your question was framed in the speculative future tense, but now you speak in the past tense about some real problem. Are you actually seeing restrictions on a running 400+ motor or extrapolating a problem from a hunch that may prove to be overstated?

Aftermarket manifolds look great and many probably flow well, but are we convicting the stock manifold of a crime that we have no evidence to corroborate and may have actually not occurred at all? If there is some anecdotal evidence are we trumping up shoplifting to Bernie Madoff status?

[niswiz]

just saying that i am using a sr20 throttle body. haven't begun to tune the car to this output. wanted to make sure the manifold will not be a problem later. trying to be proactive so i wanted to know the views of you guys as some of you have more experience than me. ilive in a country where there are only about 3 ca18det and none to the extent that i am building. will also be using nitrous and water injection on the fully forged motor.

[niswiz]

was just watching youtube and mobnes made 497whp using the stock manifold so i guess this answers myquestion some. so i may just modify my standard manifold. give it a port, may cut it open, port match the 60mm throttle body to the manifold. if i'm adventurous enough i may even add velocity stacks inside the standard manifold. will post pics of what i do.

[themadscientist]

You can match the throttle, but all that other stuff is so involved you might as well get an aftermarket one.

Honestly, you just want something nifty because it's nifty, not because you actually need it. You illustrate an example of a stock manifold that makes the numbers without these things you mention then in the same breath infer you need to do them for the power you just saw an undone manifold make.

Just get an aftermarket manifold and stop trying to justify it to yourself.

[TheMAN]

I'm sticking with the stock manifold. The runners and plenum look more than adequate and setup properly to evenly distribute the air charge to each cylinder. I hogged it out for an SR20DE S14 throttle, though.

how much difference is there from the KA throttle?
are they the same size, just externally different?

[themadscientist]

I would not be surprised if they were the same thing, actually.

[niswiz]

was just looking to see if icould improve the standard manifold. there is always room for improvement but asyou put it, if it canwork leave it alone. will let you guys know how it works

[themadscientist]

Well, I didn't say that. Yes, that is one opinion; "if it ain't broke, don't fix it." I sometimes think that way as I imagine you do as well. I also have been known to fix things that were'nt broke because for whatever reason I thought it looked cool or the price was right etc.

I'm just pointing out the difference and suggesting you recognize what this is, a desire to do something more than is necessary, not a real need to reengineer a functional and adequate part. Nothing wrong with that. If you want to do it I think you should. It's your car, it's your personal expression and obviously more to you than basic transportation, so hell, have fun man!

You think I need eight injectors? No, but I got em!

[ISL33P]

the stock manifold's major flaw is the variance between cylinders....up to 10% between cylinders. Yes it can be tuned out if your ECU has the ability.

Forget about what power you can make with the standard manifold, think about how much more power you can make with an aftermarket one....effeciency is the key, regardless of 200kw or 400kw

[themadscientist]

No, think about how much money you wasted on something you didn't need.

If you have an unlimited budget, by all means go crazy, but 99% of the people, especially the CA18 demographic are working within a budget and with modest power goals. Spending coin on a nifty manifold in that case requires taking funds from something else. The CA18 under 400hp needs, granted IMO, a minimum of new rod bolts, bigger injectors and supporting fuel system and a standalone with a new quality turbo and FMIC. If you have some money left over, forged pistons and a metal head gasket. It's no good being able to flow all that air if you ran out of money to handle it when it gets inside the engine.

[ISL33P]

wasted in your eyes, but a smart move if you want to make the most power you can out of your current combination. Why upgrade turbo or throw another 2-5psi into it when a custom manifold may do just that for you. Just a differen, and some would way, a smarter way of looking at it. Then again, like you said, it does come down to budget as well, nothing with cars is cheap.

An old saying that I will never forget

cheap - fast - reliable............pick two