40 replies to this topic

[kaymo]

OT, I also have a theory about using a small, long bead hone, like used for honing and rebuilding master cylinders, to open up and smooth over the stock intake manifold runners and casting.

zak, a long time ago i discussed porting polishing with a teacher of mine. he's a real knowlegable old fart so i always took him quite seriously. he warned me that polishing or smoothing of the casting of a carb'd intake runner is DANGEROUS. he said this has the habit of allowing the atomized fuel to re-liquify whilst running down the smooth runner and pour liquid fuel into the cyl. he told me the roughness in the casting is what kept the air and fuel bouncing around and staying atomized. he told me unless its fuel injected or turbo'd (both of which would make this a non issue) DONT polish those bumps!

[86rustbox]

thanks for chiming in for me. on your e85 thread, it kinda seems like we're just talking to each other!

let me summarize some info in here to get things organized just in case there is any confusion or whatever...
*ALL SOHC EW'S ARE CALLED 12 VALVES UNLESS NOTED AS 8VALVE (IIRC only hf models)
*ALL non Si USDM cars had CVCC, even the 8 valve engines which were, so to speak, actually 12 valve engines in that they had the 4 cvcc prechamber valves
*Si heads do not have "quench pads" but rather, an uninterrupted, sort of, hemispherical (dodge isn't the only one that can make hemi's) resulting in a much lower compression ratio. This head with the stock DX pistons (cdm and usdm are the same) results in a major drop in compression and isn't recommended.
*USDM DX intake manifolds and carburetors can be used on non cvcc heads successfully as stated above. it is also possible to drill openings holes between the main intake runners and the cvcc ports in order to use the cvcc function of the carburetor and effectively raise the cfm output of the carburetor (slightly but significantly for such a small engine) a gasoline safe epoxy then can help aid the smooth flow by blocking off the opening on the manifold base if so desired though probably not absolutely necessary.


I am currently building an Si engine with brown top integra pistons and, unless I manage to find a cdm carb/manifold, I will rebuild and reuse my usdm set as per the aforementioned plans. OT, I also have a theory about using a small, long bead hone, like used for honing and rebuilding master cylinders, to open up and smooth over the stock intake manifold runners and casting.

man this thread needed a clearing up of the facts about heads!

and kaymo is right, figure out what you want EA HOMIE, especially as a final outcome. i only mentioned the ability to use stock carb/mani because that's probably what i'll end up doing, just so i don't overclass myself for racing. that is, i don't want one thing to put me in class where i'll get my ass handed to me cause i'm not boosted or something.

CVCC isn't optimal for racing, but you can get some decent performance out of it. i still have CVCC and the devac, mechanical secondaries, and filed power valve combined with an intake/header/exhaust got me a relatively good boost in power from stock. i won my class in rallycross against some much faster cars; a focus, golf, and a 1g crx SI. and you DO keep the good gas mileage with the CVCC, if that's a priority.

OH...and if you valves are ticking, have you tried adjusting them? the manual says they need to be adjusted on EW engines like every 25k miles or something. mine were ticking and a little cold-engine adjusting quieted them down nicely. be sure to read up on the gapping, i don't remember what it is, and do it when the car hasn't run for 8 hours or so.

[zakats]

zak, a long time ago i discussed porting polishing with a teacher of mine. he's a real knowlegable old fart so i always took him quite seriously. he warned me that polishing or smoothing of the casting of a carb'd intake runner is DANGEROUS. he said this has the habit of allowing the atomized fuel to re-liquify whilst running down the smooth runner and pour liquid fuel into the cyl. he told me the roughness in the casting is what kept the air and fuel bouncing around and staying atomized. he told me unless its fuel injected or turbo'd (both of which would make this a non issue) DONT polish those bumps!

There will be a lot of crosshatching and I don't see it becoming a potential problem with a warm manifold or even a houston-cold manifold

[zakats]

the only thing anyone has told you is that CVCC is better for economy, and no CVCC is better for power. but, are you opposed to gas mileage? i dont think anyone here is. how much power do you gain from losing the CVCC? this is something i have yet to hear anyone really tell me.

as a matter of fact i am gonna have to challenge the idea that CVCC is "BAD" for making power. my argument being the EW5. the EW5 motor is a JDM variant of the fuel injected SI motor that had 16 valves, 4 of which were cvcc! IIRC the HP rating of the EW5 was 108... which is the same as the 91 SI engine. thats 17 HP over the american EW engines without CVCC. where does this extra 17 hp come from?

back to what you are trying to do with your car. im going to hazard a guess that this is meant to be a daily driver, and not a track machine. you are rebuilding the engine with factory internals, and slightly shaving the head. in this case, you will gain almost nothing by changing carbs. (CDM or weber) with either you lose CVCC and fuel economy, and change the way your engine runs. if you want an explanation of the CVCC let me know and ill find one for you.

another issue that no one really touches on when doing a CDM carb swap is, what if you have to rebuild it? now you must source a CDM carb gasket set! now you are adding more hassle to your car! and talk about hassle, get a webber! now you have a carb that did not come tuned for your engine! i have not heard of a single webber swapped car that didnt have a DRAMATIC decrease in fuel economy. its hard to go fast when you're out of gas!


im not sayin DONT do it, im just saying KNOW waht you're getting into! a webber is GREAT carb! but without engine mods, and the knowhow to tune it.. you are gonna be in a world of regret.


as captain regular said, your stock carb can be easily modified to be as simple AND as powerful as the CDM carb. there are many writeups on the subject. combined with the darkhand manual secondaries mod, this will really change your carb into a new animal (unless your carb was running REALLY good in factory form, which i have NEVER seen)

the rebuild kit for your factory carb is cheap and easy to do, so if you are unsure of its condition at all i recommend it. this was the first carb i ever rebuilt and it was pretty damn easy.


anyway, before you go purchasing all this stuff, PLEASE put your engine back together and devac your stock carb and try it. it will not cost you anything to try the your old one, and if you feel you need more after that by all means. but just try it before you go spend money on carbs that will gain you almost nothing but more hassle

I really don't want to read all that but I'm going to pick a few points out that I want to offer my $.02 on. Honda stopped using cvcc for a good reason- it was very good for its time but became obsolete and discontinued. The EW5 developed a substantial power boost over the USDM Si for a few reasons- higher compression ratio being the biggest one. Why do the newer D series engines make so much more power over the ew3? Think about it, it has 8.7:1 CR compared to, say, the very common D15b7 that had 9.2:1 cr and made 102hp with a very lame, economy tune. The EW5 was sold as the top option for the civic and was probably given a more aggressive tune... not to mention being rated in a less emissions controlled and higher octane rating Japan.

CVCC means more mass and friction without the benifits of the flow of a typical 4valve per cyl setup.
CVCC is helpful in using lean a/f mix and staying efficient but the cvcc head flows terribly and is inefficient for high rpm operation mainly due to the prechamber setup. what it MAINLY comes down to though, I believe, is that the cvcc valves get old and are usually overlooked in rebuilding and don't seal well after age so the head leaks compression or just suffers from whatever byproduct of age that never gets sorted out because it is a pain in the ass and a waste of time. CVCC is cool and worthwhile if it fits your goals.

[kaymo]

ok so sure a 4 valve per cyl would flow better than a cvcc, but we dont really have that option unless you go teg head or whole engine.

how does cvcc change the flow when the prechamber has its own seperate valve? the other valves would still flow the same would they not? or is it the cvcc runners inside the head are taking up space where there would normally be the normal runners? i believe CVCC died because people stopped caring about fuel mileage. CVCC helped produce less emissions and better fuel economy... and thats what supposedly the world is worried about right now. i think CVCC needs a comeback with new age tech...

im not saying i know better or anything, i only argue to understand better... instead of sayin "oh well that just doesnt work that way" KNAWMEAN?

oh and yes there is a rubber O ring that seals the CVCC valve and is cheap to replace and easy to get to, just pop the VC and unscrew the valve. thats waht i was told by a machine shop when i asked them about fixing my honda head.

and yah i would agree that the CVCC head probably aint great for high RPM flow, but then again what 1/3g civic engine is great for high rpm flow? the SI is better but is it phenomenal? i kinda wonder why no one has tried combining a turbo with the lean burn effect of cvcc... i kinda wonder if honda wasnt trying this at some point and just scrapped the turbo part. this is around the time they did the City Turbo innit?

[zakats]

ok so sure a 4 valve per cyl would flow better than a cvcc, but we dont really have that option unless you go teg head or whole engine.

This really isn't as hard as you'd think- just a matter of using different parts when you rebuild.

how does cvcc change the flow when the prechamber has its own seperate valve? the other valves would still flow the same would they not? or is it the cvcc runners inside the head are taking up space where there would normally be the normal runners?

flow is affected in that there is a very limited amount of potential improvement due to the cvcc pocket and flame travel time at high rpm- in theory. either way, when you're making power you really don't want to have anything in the way of your spark nor do you want lean conditions. CVCC helps run lean more compression on lower octane, most which can be done just with the quench pad! The rest can come with better ignition and modern fuel injection... only the end result is more efficient than the cvcc setup. CVCC might have been good for its day in producing low HC emissions but it did just as bad with NOx (iirc it was nox)
The other valves are, I believe, almost as big as the Si/ew5 valves (1mm smaller as I've been told)- I could speculate, though it would be a stretch without accurate comparison, that the dx casting flows less due to the space taken up by the CVCC components.
No, both cvcc and non cvcc manifolds are directly compatible, the CVCC "holes" don't get in the way of anything (but performance)

i believe CVCC died because people stopped caring about fuel mileage. CVCC helped produce less emissions and better fuel economy... and thats what supposedly the world is worried about right now. i think CVCC needs a comeback with new age tech...

I think it died because it became obsolete with more advanced PGMFI but even if that were not the case, it would come back out if it really were that helpful, it would resurface out of necessity- it would save honda a hell of a lot of money in tech development. With direct injection, ivtec, avtec, vtc, and advanced computerized engine management CVCC offers much less and doesn't really offer much in comparison.

im not saying i know better or anything, i only argue to understand better... instead of sayin "oh well that just doesnt work that way" KNAWMEAN?

I agree completely, I find myself digging through threads that I've posted on hoping that somebody has substantiated, hard info on why I am wrong. I love to learn about this stuff!

oh and yes there is a rubber O ring that seals the CVCC valve and is cheap to replace and easy to get to, just pop the VC and unscrew the valve. thats waht i was told by a machine shop when i asked them about fixing my honda head.

meh...

and yah i would agree that the CVCC head probably aint great for high RPM flow, but then again what 1/3g civic engine is great for high rpm flow? the SI is better but is it phenomenal? i kinda wonder why no one has tried combining a turbo with the lean burn effect of cvcc... i kinda wonder if honda wasnt trying this at some point and just scrapped the turbo part. this is around the time they did the City Turbo innit?

With decent, home brew porting, the Si head does well enough unless you're talking about putting down big numbers with turbo... then again Sawchuck proved that it is possible. There are plenty of racers that, with big cams, run their engines over 8krpm all the time using the Si head... I'm sure they've done it with the CVCC head too due to class rules but at a major loss in potential power and would rather be running a non cvcc head if it were legal- I'm sure they had a hell of a time finding valve spring upgrades for the cvcc valve too.

Lean and turbo do not go together period. with the proper amount of fuel, it is thought that cvcc could help lower the possibility of detonation though the costs would likely outweigh the benefits as the cam and flow issues would arise again. I also imagine it would be funky to tune and, due to being over 100% VE, the cvcc effect would be minimized.

I believe you are correct about the city turbo, but then again, that would go with my point that CVCC just gets in the way with a boosted engine when you could, instead, just have better electronics to get the same effect.


Keep in mind that CVCC was developed back in the early 70's and did a good job at being superior tech to the day's tech competition. Honda isn't the only company that use such technology, I know that at least mitsubiti used it in some of their engines including the Starion. Even in the Starion community, their version of CVCC is/was very unpopular for performance and is usually done away with.


PS I don't expect everyone to read all that bs! Cliffs: CVCC- obsolete, good for low tech fuel systems like carburetors, bad for high rpm, its a waste of time for most people especially when the car will make almost the same fuel economy without it

[87civDX]

ok well i dont have anything to add about cvcc or carbs or heads but i did want to point out that EA HOMIE is in cali so he will have to pass the emissions testing so a webber is not an option if you have to pass smog and nither is a cdm carb i think that you can get away with a head swap it you go through a referee but then again i dont know if they really like frankenstine set ups

or he could just not be worring about the emissions test and therefore just disregard everything that i just said

[DarkHand]

CVCC explained as simply as I can manage:

Flamethrower spark plugs.

A CVCC engine runs on a very lean mixture, so lean that a normal spark plug won't ignite it. The 'real' spark plug ignites a tiny bit of rich fuel in its own tiny chamber. That flame shoots out into the real chamber like a flame thrower and ignites the lean mix.

[EA HOMIE]

wowwwwww alot of info on this! i first wanna say thanks to all for it. alright this is an update of the car. 1st got the Weber carb soo there goes the carb. i just sent my stock head to get everything check and also shave. next im sending the block to be bore due to bigger pistons and also check the crankshaft and most likely replace it. soo far that's about it. it is going to be a daily but at the same time i want some power! im actually trying to fine bolt ons (headers, cam, full exhaust system)


Thanks again for anything all ur tips help.
Cris

CVCC explained as simply as I can manage:

Flamethrower spark plugs.

A CVCC engine runs on a very lean mixture, so lean that a normal spark plug won't ignite it. The 'real' spark plug ignites a tiny bit of rich fuel in its own tiny chamber. That flame shoots out into the real chamber like a flame thrower and ignites the lean mix.

[86rustbox]

With decent, home brew porting, the Si head does well enough unless you're talking about putting down big numbers with turbo... then again Sawchuck proved that it is possible. There are plenty of racers that, with big cams, run their engines over 8krpm all the time using the Si head... I'm sure they've done it with the CVCC head too due to class rules but at a major loss in potential power and would rather be running a non cvcc head if it were legal- I'm sure they had a hell of a time finding valve spring upgrades for the cvcc valve too.

as i've heard the CVCC valves don't need an upgrade, and can work the same with the other valves reworked. i emailed colt cams, who will regrind a CVCC cam without touching the CVCC lobes and they say it works fine. also, KMS makes valve springs for the SI head, which will work on the 12 non-cvcc valves. it doesn't list them on their site, but they have them upon request. but all in all it's easier to go with an SI head; might be useful for anyone who has to keep CVCC.

http://www.coltcams.com/
http://www.honda-performance.com/

EAHOMIE, i hope this helps and i'm sure you could find a header on ebay or something. that's a good thing to go ahead and get out of the way...these EW exhaust manifolds suck. as for whole exhaust, good luck. just have a muffler shop make a side exit just past your passenger door. don't know if that's legal in cali, but it is here as long as you have a resonator and cat...and it's great for flow...eliminates like 5 bends from the pipe. other folks on here have done it so there's pics somewhere.

Edited by 86rustbox, 19 August 2009 - 11:44 PM.

[kaymo]

well if you've got a webber now, your out of my realm of knowledge. good luck tuning it and passing emissions and all that


kaymo- who lives in a "left turn signal, ok now right turn signal" inspection county