kentucky accord

been thinking about going carbs for quite some time now and would just like a little feedback on them. im fairly new to the game when dealing w/ carbed import engines. ive had various small block domestic engines w/ carbs but never got into them too much.

the setup would be a sohc F22a non-vtec engine(Accord engine btw) w/ final compression ratio being above 14:1 but below 15.5:1 and bore size between 89-91mm. my main concerns are picking the correct carb size (mm) and jet settings. i would also like to get some pointers on where to get the best deals on weber carbs as those are my brand of choice.

ive come across several CFM calculators to help in choosing the correct size carb. its just rather confusing when i know of 3.0L engines running dual 55mm, a 1.6L running dual 55's, and a 2.0L running 55's. i was thinking of something in the 48-50mm range for myself....

any help would be much appreciated. also, say i was to go w/ twin 50's would that be enough carb if i wanted to run meth down the road?

thanks,
Carbless Clueless Accord

0Bisimoto

Carbs size would be dictated by the venturi requirements of your powerplant. This is dependant on your engine displacement and maximum RPM limit of your engine. The carb venturi size should be between 80-90% of the throat/butterfly size, for ideal atomization (read, power for you!) The smaller the percentage, the better.

Provide me these numbers (displacement and RPM), and I can share with you ideal figures. I have my own sizing algorithms based on my own experience with a variety of sohc and dohc inline four motors.

Jetting is a piece of cake. It takes me a fraction of the time to tune a carb'd engine compared to my fuel injection peers.

As for methanol, I should have data by mid season of '04. I have not had the need to convert yet, hence my knowledge is non-existent. Carb size is not the issue; emulsion tubes and needle valves may be.

Redline weber can help you with parts. http://www.redlineweber.com 1-800-733-2277. Ronnie can help at ext.# 7457.

kentucky accord

i appreciate your reply and was hoping that you would as i know you are very knowledgable concerning carbs.

if my calculations are correct w/ a stock stroke of 95mm and a bore diameter of 91mm, i get 2.47L of displacement or 2471cc's. now, since im not going to destroke(although i probably should to improve the horrible R/S ratio) i dont see myself trying to make much power above 7,000 rpm. i use stock fuel cut as the limit right now w/ a fairly mild off the shelf cam. i do have another cam grind in the works although probably still mild by your standards.

i may be barking up the wrong tree with my plan of not revving past 7k and switching to carbs. from what ive heard, carbs are great for top end high revving screamers. but, i just want to take advantage of what the F22 starts out with, torque. do you think i could gain some decent torque and hp by using carbs in my particular application?

i look forward to your reply and also some information on meth when you get to it. i was thinking of tuning on race gas and then possibly adding some meth to the tank...for starters at least.

danimal

might i humbly suggest that you establish solid goals for the rpm band that you want to run... it sounds like a street car?

remember that higher revs = more air thru the motor = more power.

the real peak power band of a motor is ultimately a function of head flow at the intake valve vs. displacement... do you have measured head flow numbers from a flow bench? i'll dig up the math for you if you do... it's a simple formula, and you might be in a better position to select the camshaft.

fwiw, one thing that may be an advantage with carbs/itb's over a plenum intake/port injection is that the fuel starts atomizing a lot higher up in the gas column... for 7,000 rpm's that probably won't matter, but i've seen pics of 8,000+ rpm motors with an injector above each itb throttle plate, for just that purpose... the time for atomization is real short at ultra high rpms.

getting those sizing numbers from bisi could save you some real headaches!

kentucky accord

no its not a street car and the 7k limit isnt set in stone. just because i dont want to spin to 10k doesnt mean i cant make some good power IMO. the rod/stroke ratio of an F22 is 1.48, hardly ideal for anything in the 7k+ range. the block will of course be sleeved but they will be quite thin @ 91mm and aside from block posting, destroking, or pouring concrete in there, nothing will stop rodney from making a quick exit.

idealy speaking, destroking would be the key move to make, i could improve the r/s ratio and still have a big bore engine. but, this vehicle is my weekend racer that doesnt travel outside of the state to race and im a hobbiest, not a pro. hobbiest meaning i like to have fun w/ the car and im not worried about breaking records or winning money.

in my case, im betting on proper carb selection and using the long stroke to my advantage. the current race weight w/ driver for my Accord is ~2250lbs, no lightweight but roughly 950lbs less than stock and counting. point being, this powerplant isnt going to be in a 1600lb civic and i would like to make as much torque as possible. i think a nice flat torque curve is just as sexy as a HP peak taller than Mt. Fugi.

but to answer your question of power bands, i dont have much of one to work with. i run the h22(prelude vtec) transmission currently and it has a 4.27 FD. couple that w/ 22-23" slicks and im working the gearbox like crazy just through the 1/8 mile. i stage at roughly 5500rpm and shift at an indicated 6800rpm. between shifts the engine never gets below 5000rpm. w/ a maximum rev out of 7k, that only leaves me w/ about 2,000rpm to work with. ARG, someone smack me and just tell me to destroke the engine!

a stock stroke F22 may be safe a little over 7k and i wouldnt have a problem being the test mule.

Jared

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danimal &raquo;</TD></TR><TR><TD CLASS="quote">
remember that higher revs = more air thru the motor = more power.
</TD></TR></TABLE>

Not true, don't spread total misinformation like this. Revving an engine higher doesn't mean its going to make more power. If the powerband is falling off, you can rev the engine to 20k and it won't make more power, it will just damage more parts. Powerband is dicated by manifolding, port design, camshaft, compression, rod to stroke, bore size, valve size, etc.. NOT by rpm.

EG-lowrider

keep this post alive, I love info like this

0Bisimoto

2.471L is correct. I would by leary of the 91mm bore size though. I run 90mm myself.

For the given RPM of 7000, your venturi requirement is 42.7mm.
For 8000rpm (more realistic, especially if I design a cam for you) is 45.6mm.

My recommendation is a 50mm weber with a 46mm venturi. The Weber 50 dco/sp carb comes with that from factory. http://www.redlineweber.com

As for carbs being ideal only for top end? That is pure misinformation. I'll give you a hint: I launch my car at 4800 rpms! Carbs would be ideal for you, and many a racer based on cost and performace advantages.

kentucky accord

great reply and its very, very helpful, thank you.

are you leary of the 91mm bore because of reliability issues? specifically, sleeve strength, head gasket sealing problems, cooling, etc.? if i remember correctly, you run a 2.23? just running the figures through my head, that would mean your engine setup is practically dead on square w/ a tasty rod stroke ratio. Congrats! no wonder your a Scientist.

alas, i dont want to put a small fortune into the engine but, i think a good build would make it dependable to almost 8k. i will be in contact w/ RS Machines sometime next week. did you just offer to design a cam for me? i would be ignorant to not take you up on that offer(just as long as i dont have to sell of a kidney, LOL). if that something we need to talk about through E-Mail or instant messenger, thats fine by me.

ok so you recommend A 50mm weber w/ 46mm venturi. when you say 'A', do you mean a single carb setup or a pair. please excuse the somewhat ignorant question but i just want to be sure as many lights have been shed on me just from your last few posts.

i totally agree about carbs being cost effective and very advantageous. i was weighing the factors of stand alone ECU or carbs and ive leaned toward carbs more and more obviously.

one more question concerning the intake manifold on a carb setup. myself along w/ a close fabrication friend will be tackling the intake. have any pointers concerning them? i/we have our own ideas based on previous setups, and lots of experience on carb'd VW engines. we were both thinking of a more sqaure type w/ a gradual "flare" intake runner setup and steering away from the common round tube type. ive been reading up on dimples on the intake side ports as well....man, this stuff gets more interesting by the minute!

danimal

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jared &raquo;</TD></TR><TR><TD CLASS="quote">Revving an engine higher doesn't mean its going to make more power. If the powerband is falling off</TD></TR></TABLE>

lol... only a total idiot revs beyond the power band... but it is a good thing you pointed that out for the newbies.

everything you said there is true... now tell the forum why bisi said to use an 8,000 rpm camshaft.

hint: if you can't handle that, cut 'n paste everything i just posted, it'll be a lot easier.

kentucky, i think that nissan once made a motor with a 1.43 rod ratio... bad for longevity, but great for torque... i prefer torque on the street, but h.p. is king on the track.

you are building a race engine, but you have no head flow numbers?? here is the math for an h22 head that flows 160cfm@10"@.500 lift:

per fred simpson at performance technology, here are some proven calculations for finding the rpm for maximum power. Note that the variable is 2000 for race engine efficiency, and 2200 for sportsman, sand engines, and serious street/strip cars:

for a 2471cc engine = 150.79 ci, so the CID of one cylinder = 37.7".

RPM = 2000 x (cfm@10" water)/CID of one cylinder

RPM = 2000 x (160)/37.7 = 8488 rpm as the peak power point.

so what does all that mean? you cannot make more power by revving past that rpm point, regardless of what you do with the intake manifold, camshaft, etc... if your camshaft is designed for less than 8488 rpm, you'll be throwing away power.

what does this mean for kentucky? if he did indeed have an h22 head on his motor, he'd be really crippling the power output by putting in a 7,000 rpm camshaft.

there is more math that will tell you roughly how much power you are throwing away by limiting the rpm that much, but offhand i can tell you that it is significant... because power always goes up with rpm... at least if you aren't exceeding that 8488 rpm limit :-) and the rest of the motor is designed around the head, like it's supposed to be.

the head is ALWAYS the ultimate limiting factor of any all-motor configuration.

hope i got the math right here... somebody better check it!

kentucky accord

im not going to argue w/ numbers any day of the week, LOL.

im sorry i dont have head flow numbers for you at this time. but i can tell you that a 2.47L H22 and a 247L F22 will have different peak power points and differnt torque curves.

i also know that you need a good amount of compression to utilize a 8k cam. im sure 14:1-15:1 would be sufficient.

as for longevity on a 1.48 R/S ration F22, i know plenty of 3-400k mile accords. of course, they are limited by RPM and thats what is almost "scary" to me in regards to this build. i dont know the limit of an F22 w/ 95mm stroke, but by god i will find out if i need to....

0Bisimoto

I have relaible information from an H22 racer around gasket sealing with a 91mm bore. At 90mm, I have not had a need to go larger.

I can assist with a camshaft design; I should have nice ones by mid January. If you dont mind providing feedback, I can give it to you at a decent price.

My apologies for the "a" carb. You need dual carbs.

Your intake port should dictate you mainfold shape at the port entrance; your DCO carb will have a circular outlet. A flare, or taper, is desired (gradual/2~3 degree decline towards the head). The Carb should not have more than a 7 degree incline from the plane, at race stance. Length would be determined by the intake pulse harmonic that you desire to take advantage of.

Dan is right! Everything begins and ends with the head!!

I may have said too much. Hurry up and destroy everyone in your wake!

kentucky accord

wow, mucho information! i knew you would have to cut me off sometime, lol. cant let all the secrets out of the bag now can ya? of course, since you are running an F18 in the future, i suppose a peak into your "old" setup doesnt really hurt anyone.

whenever you feel like getting the ball rolling on the camshaft, you just say the word and i will do whatever i can to help. i would be more than willing to give feedback as im always out to help someone who helps me. honestly, i would be a pretty decent candidate as i race several times per month, both 1/8 mile and 1/4 mile.

your information and help is invaluable and its much appreciated.

THANKS!

0Bisimoto

Actually, I ran 10.06 with my F22, and 10.14 at 2600ft elevation with my F18. The F18 has been in my vehicle for the past 3 events.

I will start the season with my F18 as well, in February.

EG-lowrider

I know an f22 is an accord sohc motor, is a f18 an accord also, and what heads could be used on these blocks, ie. b7, z6, a6, b anything, I would love to swap my head onto a 2.2 block, can this be done?

TREVER

Is a f18 a destroked f22?

Wazup

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TREVER &raquo;</TD></TR><TR><TD CLASS="quote">Is a f18 a destroked f22?</TD></TR></TABLE>

i believe its out of an ascot or something like that, if thats the correct name, i could be completely wrong..

Mista Bone

Bisi, what are the Webers rated at cfm wise PER throat?????


I have a weird idea, something only you could understand.

Mista Bone

weld and grind, same routinue as old D15 motor?

how did you cut, about 8 mm off the crank throw for new motor?

F20 crank?


Modified by Mista Bone at 5:49 AM 12/10/2003

kentucky accord

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mista Bone &raquo;</TD></TR><TR><TD CLASS="quote">
I have a weird idea, something only you could understand.</TD></TR></TABLE>

something like this possibly? gutted carbs turned ITB's.....

http://race101.com/images_03/c...4.JPG

Mista Bone

Holley 390 cfm 4 bbl, 1:1 secondarys.

Tune it like it was a set of ITB's.

Need to bounce this idea for a manifold off Billy.

jasonp

Hey can you explain a little more about this way of running this holley carb set up.. I read about the carb and it has four corner adjustment screws but I would like more info.. thanks..

kentucky accord

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mista Bone &raquo;</TD></TR><TR><TD CLASS="quote">Holley 390 cfm 4 bbl, 1:1 secondarys.

Tune it like it was a set of ITB's.

Need to bounce this idea for a manifold off Billy.</TD></TR></TABLE>

i will let the Pros take care of the math and specifics but i can add what i know from personal experience. i have many Jeep(yes i said Jeep) friends that run the Holley and Edlebrock 390 on their 258ci 4.2L inline 6 engines. of course, they dont turn the RPM that you will/would but from the looks of it, 390 is way overkill.

if my math is even in the same ballpark and please dont quote me on this because i dont even know what setup you have in mind. but, based on a 1.6L engine ~8,000 rpm rev limit, and a decent build, im coming up w/ like a absolute max of like 230-245cfm worth of carb. but, like i said, im not a scientist like Bisi', LOL.

please someone correct me before i get in trouble......

SuperTwinz

Keihin 41mm FCR carburetors were the carburetors I had on my car. The kit was made by SS Works in Japan and very popular among the Toyota 4AGE people. There were a few road race cars using these setups making 240 whp in Japan. I made 173 whp on a bone stock B18c5 with these untuned. The drivablility is like stock and idled at 900 rpm with no problems. On highway I can easily get 30 mpg and on street 10 mpg.




Road race prepped EG6:

danimal

390cfm would indeed be overkill if it was mounted on the typical v-8 style plenum intake... compare it to the size of a single factory honda throttle body plate.

but since this is an itb thread, perhaps he meant to somehow construct a custom, equal length, individual runner intake manifold that matched each intake port with it's own barrel on the carb? :-0

in which case the 390 wouldn't be near big enuf, since each barrel should be capable of flowing the total cfm of the engine all by itself.

and what about the fuel distribution? this is giving me a headache, lol!

nice carb pics, btw... check the welding on these manifolds:




Modified by danimal at 9:54 PM 12/11/2003