64 replies to this topic

[C8V6C]

I've never asked about carbs, but I wanna make it clear that I am sure my circumstances are different than yours, but it's not the compression that should be holding you back...maybe other things

[86rustbox]

I've never asked about carbs, but I wanna make it clear that I am sure my circumstances are different than yours, but it's not the compression that should be holding you back...maybe other things

oh, i know...i've seen your build thread! sweet ride. if you do end up trying e85, keep us updated.

like i said, i'm just going to try it along with some easy carb mods and see if i lose too much power. it won't be anything i can't easily change back.

[zakats]

Just for experimental purposes, consider not messing with the jetting- rather keeping the jet ratios (cvcc and etc) the same just to see how it does, and run an electric pump with a FPR to up the pressure to...say... 8psi and save the rest for an Si head and a set of pistons!

[86rustbox]

Just for experimental purposes, consider not messing with the jetting- rather keeping the jet ratios (cvcc and etc) the same just to see how it does, and run an electric pump with a FPR to up the pressure to...say... 8psi and save the rest for an Si head and a set of pistons!

i don't think messing with the cvcc jets will make much difference anyway, it's such a fraction of the total amount of fuel delivered, but i could be wrong. i was just going to do the two bigger jets...the ones labeled "60" and "115" which i assume are for the primary and secondary. for now i'm just trying to make it work on my setup (pistons, head), because i'd have to get a different carb anyway to run an SI head, unless i could figure out how to use the same manifold and route the 3rd barrel port into the mains. do you think i'd be able to stick my manifold on the SI head with a weber on top? i think the weber adapter plate opens the 3rd port to the rest of 'em. maybe block off the 3rd port and have the flow just go into the other two?

what difference would and electric pump and a FPR make?

[zakats]

i don't think messing with the cvcc jets will make much difference anyway, it's such a fraction of the total amount of fuel delivered, but i could be wrong. i was just going to do the two bigger jets...the ones labeled "60" and "115" which i assume are for the primary and secondary. for now i'm just trying to make it work on my setup (pistons, head), because i'd have to get a different carb anyway to run an SI head, unless i could figure out how to use the same manifold and route the 3rd barrel port into the mains. do you think i'd be able to stick my manifold on the SI head with a weber on top? i think the weber adapter plate opens the 3rd port to the rest of 'em. maybe block off the 3rd port and have the flow just go into the other two?

what difference would and electric pump and a FPR make?

You don't need a different intake mani or carb to run the Si head, in fact, the usdm 3bbl carb (as I am told and through observation) flows better than the cdm carb though not better than a weber downdraft- which would also work with both setups.

By using the unmodified carburetor and just playing with your fuel pressure with the FPR, you will be able to easily tune the amount of fuel pressure into the engine- resulting in the same ratio of fuel between the barrels and jets.

It is NOT worth it to spend money on the stock carburetor unless it is significantly cheaper than the alternative- the single downdraft- in your case, rebuilding of the carb for performance is a waste of money. STILL, a much better cost/effective would be to invest in a better flowing head and proper pistons that will, alone, be better for your performance and will lead to a much more capable setup when/if you do go e85... which will still be very much do-able on the stock carb.


supplementary: The cvcc design featured many aspects to the theory (omitting the cvcc aspect since it is just a component in this, I'm just using this as an example bc we're all familiar) but I recall one that states something along the lines of honda using a low compression ratio so that they could run a very lean mixture of low octane a/f without detonation- with the adjustability of a fpr, you could also adjust for leaner mixtures if you drive this car to events or happen to be curious about making fuel economy.
If you should happen to switch to the Si head, you might consider opening the cvcc intake runners to the main runners in order to use the full potential of that carburetor- just a thought.


I'm sure that I am missing from what I meant to say in there... feel free poke holes in my theories so I can figure out what it was

[86rustbox]

You don't need a different intake mani or carb to run the Si head, in fact, the usdm 3bbl carb (as I am told and through observation) flows better than the cdm carb though not better than a weber downdraft- which would also work with both setups.

By using the unmodified carburetor and just playing with your fuel pressure with the FPR, you will be able to easily tune the amount of fuel pressure into the engine- resulting in the same ratio of fuel between the barrels and jets.

It is NOT worth it to spend money on the stock carburetor unless it is significantly cheaper than the alternative- the single downdraft- in your case, rebuilding of the carb for performance is a waste of money. STILL, a much better cost/effective would be to invest in a better flowing head and proper pistons that will, alone, be better for your performance and will lead to a much more capable setup when/if you do go e85... which will still be very much do-able on the stock carb.


supplementary: The cvcc design featured many aspects to the theory (omitting the cvcc aspect since it is just a component in this, I'm just using this as an example bc we're all familiar) but I recall one that states something along the lines of honda using a low compression ratio so that they could run a very lean mixture of low octane a/f without detonation- with the adjustability of a fpr, you could also adjust for leaner mixtures if you drive this car to events or happen to be curious about making fuel economy.
If you should happen to switch to the Si head, you might consider opening the cvcc intake runners to the main runners in order to use the full potential of that carburetor- just a thought.


I'm sure that I am missing from what I meant to say in there... feel free poke holes in my theories so I can figure out what it was

how can i use the same manifold??? i'd imagine the cvcc ports would lead to nowhere...being blocked on the head side of the mani...and fuel from the 3rd bbl would build up...but there must be something i'm missing. i think it IS a good idea to open the cvcc ports to the mains to get 3bbl's of flow into the head...might just be pretty powerful on an SI head. wonder if anyone has tried it.

i know all this wouldn't be worth it unless it stays cheaper, which it has so far. and thanks for the FPR/elec pump education.

[zakats]

I and many others have ran the usdm IM/carb with non cvcc heads. the 3rd bbl doesn't have a (power valve I believe is the name for it) so it adds fuel solely from the venturi affect which requires air moving through the barrel to create high/low pressure to draw fuel to be vaporized- the primary barrel, you will notice a squirt of gasoline shooting in from the firewall driver side corner when you fully open the throttle as well as a small lever that moves with the throttle that actuates this squirting (the power valve) this feature would make the fuel pooling possible but such is not the case.

Honestly, you don't really stand to gain anything in the way of saving money or having anything come 'cheap,' so to speak. With everything you decide to do you will find that there is another expense for 'just a little more' that would make the setup that much better and you will be tempted to spend. Figure out what you want to get out of this engine for sure and go from there... but I will say, you absolutely need more compression no matter what fuel you end up using. oh and again, sinking $200+ on one of these carbs? don't waste your hard earned money when the weber offers so much more.

The next item of concern- flow. Depending on what you decide to do with the head, you will gain from at least a little work done to the intake manifold, I have an idea for using a bead/flex hone to bore out the runners but have yet to locate one long and skinny enough.

[86rustbox]

I and many others have ran the usdm IM/carb with non cvcc heads. the 3rd bbl doesn't have a (power valve I believe is the name for it) so it adds fuel solely from the venturi affect which requires air moving through the barrel to create high/low pressure to draw fuel to be vaporized- the primary barrel, you will notice a squirt of gasoline shooting in from the firewall driver side corner when you fully open the throttle as well as a small lever that moves with the throttle that actuates this squirting (the power valve) this feature would make the fuel pooling possible but such is not the case.

Honestly, you don't really stand to gain anything in the way of saving money or having anything come 'cheap,' so to speak. With everything you decide to do you will find that there is another expense for 'just a little more' that would make the setup that much better and you will be tempted to spend. Figure out what you want to get out of this engine for sure and go from there... but I will say, you absolutely need more compression no matter what fuel you end up using. oh and again, sinking $200+ on one of these carbs? don't waste your hard earned money when the weber offers so much more.

The next item of concern- flow. Depending on what you decide to do with the head, you will gain from at least a little work done to the intake manifold, I have an idea for using a bead/flex hone to bore out the runners but have yet to locate one long and skinny enough.

thanks, didn't know the 3rd bbl doesn't have a power valve.

i'm working on what i for sure want from this engine, that's why i'm glad this forum is here. i'll really work on the compression issue for the fuel change, but i'll stick with the stock carb for now. the only expense from that was a rebuild kit, the rest has been things like filing the power valve down and a mechanical secondary that doesn't cost me anything but time. when rebuild time comes again...weber will probably be the answer.

thinking about classing and fuel and budget, an SI head would be my next goal, along with some high comp pistons (SI too, right?).

Edited by 86rustbox, 08 August 2009 - 08:44 PM.

[zakats]

Si head and pistons will actually result in LOWER compression.. I know it sounds stupid but that is a fact.

The pistons you want are from the 88-89 integra "black top" d16a1/ZC1 aka p29 on stock deck head/block these pistons with the Si head results in 11.3:1 +/- 0.2 and of course the effective cr is lower with the higher elevation, hotter air, etc.

^this is the route I plan to take btw

[86rustbox]

Si head and pistons will actually result in LOWER compression.. I know it sounds stupid but that is a fact.

The pistons you want are from the 88-89 integra "black top" d16a1/ZC1 aka p29 on stock deck head/block these pistons with the Si head results in 11.3:1 +/- 0.2 and of course the effective cr is lower with the higher elevation, hotter air, etc.

^this is the route I plan to take btw

does the block have to be bored over to fit? i know the tegs a 1.6, but i didn't know how much of that was just longer stroke. i found a forged KMS set, but they're $450 w/o rings. i'm thinking used would be more up my alley...

would it be lower comp than i have now to fit an SI head on my block w/stock pistons?

[zakats]

yes, the EW blocks are 74mm bore and the d16a1 (and all "modern" d series) are 75mm so you will need to get the block bore'd to fit. Geez, no need to spend that much on pistons! maybe if you're going for 250+hp turbo.
http://cgi.ebay.com/...7QQcmdZViewItem

http://cgi.ebay.com/...5QQcmdZViewItem

I have a set of PG6's (brown top d16a1) that would also work, brand new, that yield .2 less compression (11.1:1 I believe) that I'd consider parting with if I happen to get my hands on a CDM head.

[86rustbox]

yes, the EW blocks are 74mm bore and the d16a1 (and all "modern" d series) are 75mm so you will need to get the block bore'd to fit. Geez, no need to spend that much on pistons! maybe if you're going for 250+hp turbo.
http://cgi.ebay.com/...7QQcmdZViewItem

http://cgi.ebay.com/...5QQcmdZViewItem

I have a set of PG6's (brown top d16a1) that would also work, brand new, that yield .2 less compression (11.1:1 I believe) that I'd consider parting with if I happen to get my hands on a CDM head.

whoa, that is way cheaper! sometimes i forget to check ebay in my parts searching. i think for $70 i'll just buy the p29's...if i'm gonna tear apart the engine and get it bored i might as well go with the higher comp ones. but thanks for the offer!

got an SI head laying around?

Edited by 86rustbox, 11 August 2009 - 01:00 PM.

[zakats]

I started a thread on compression ratios not long ago, hoping to tap into the experience of some of our builders/racers to no avail- I've always been told that it is important to plastigauge your piston-valve clearance but there are plenty of people running this combo (ew block/si head/p29's) with no problem so I don't see why it would cause any trouble unless they all cut groves in their pistons- which I doubt... AND I'd speculate that almost all of them run aftermarket cams with a lot more lift and duration.

[86rustbox]

I started a thread on compression ratios not long ago, hoping to tap into the experience of some of our builders/racers to no avail- I've always been told that it is important to plastigauge your piston-valve clearance but there are plenty of people running this combo (ew block/si head/p29's) with no problem so I don't see why it would cause any trouble unless they all cut groves in their pistons- which I doubt... AND I'd speculate that almost all of them run aftermarket cams with a lot more lift and duration.

i talked to chris raglin (EPcivic) on here a while back and i'm pretty sure he runs p29's with an SI head on a wagon block. he didn't say anything about grooves in the pistons, but from pics it looks like these pistons already have some grooving after the downslope of the dome. i wouldn't be able run a different cam anyway because of classing, so it sounds like i should be fine with the stock SI valve lift.

now i just have to make a trip to the local machine shop to see how much it is to get my block bored over.

[zakats]

The p29's do come with reliefs already cut (for a dohc 16v head) but who can say how that will fare with a different cam somewhere down the road... just saying for future reference