Is my car worth modding??

My new purchase is a 1990 Civic GL hatch, dual carburrator, everything is stock. Up until this I was driving my Dad's commodore. As you can imagine, the civic is just a little bit less power lol. My friend has suggested a full exhaust upgrade including headers and extractirs, plus a pod filter and going from there with cams etc. Basically I'm a uni student who doesn't do any racing at all, but i do enjoy driving something with a bit more grunt. Is my car worth modding? I won't be installing a turbo due to the $$ plus insurance...

It depends on personal preference. Modding on all cars would give more power :)

Think Headers and Extractors are the same thing BTW :P

exactly its totally up to u...maybe not a full exhaust system but try a cannon muffler HANGIN ON THE ANGEL) looks tough as..and a nice k&n podfilter well not a normal one cuz u have a carby u need a carby pod filter try autobarn...get sum nice chrome ones lol

hmmm... its all up 2 u!!

but from what u have said NO.. but it jst dependz on how much money u have n how long u gona keep your car. If u not gona keep it then i would buy sumfink thtz got a bit more balls!! but up 2 u. lol..

well if your actually serious..............................
canon mufflers a a waste of time with a carby car cause they need more back pressure, secondly you cant put a pod filter on the intake tube on the dual carb you need the d shaped k&n in box filter i bought one for about $80

but by the time you change cams, jet carbies, do the exhaust, etc, your gonna pay nearly as much as a half cut with a b16a mpfi vtec engine, and still have very little power in comparison, so if you want advise id save some green bills and buy a half cut,

my rant over :zip:

asking how much ur car is worth to u is a question no one else can answer...

but if u have a certain goal in mind...then thats when others can give u a hand at making decisions...
the dual carb motor is not built for speed...and as far as modding there are a lot of DIY's u can do to make certain improvements but again, dont expect to get a racer out of this motor...

here are a few "mods" that u can apply to ur car...
http://www.ozhonda.com/forum/showthread.php?t=77138

end of the day, if this car is going to be ur beater car until u get a better one then keep the d15 and put up with it for now...but if u actually plan to keep this car and find that holds personal value to yourself...then save ur money for a b-series transfer...

btw...are u andrew ward's little brother???

not worth it.

not every car needs to be modded.

wait til u get something with more grunt
then mod that for even more grunt i guess.

IMO not worth it.

Personal choice mate. A friend of mine has the same car as you and even modded it doesnt come close to "quick". Id save the money and get a half cut or wait till you have a car that will get results.

waste of money, save it for a better car

don't bother. A--->B car

Modify an engine with potential, don't waste your time with rubbish.

if u love ur existing car and wan it to be fast and not get laughed at by these guys.. put in a b16.. or even a b18.. no point modifying a carby.. i use to have a carby lancer.. i did the exterior up.. all was all show no go.. i got sick and went honda with b16.. it moved up into a new lvl..

go to honda B series.. u get respect and u will nv regret..

NO
your mods to get a bit more grunt will be worth more than your car.

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Originally Posted by 0098

NO
your mods to get a bit more grunt will be worth more than your car.

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not really. baking tray cost me $4 and that made it a little grunty. probably not as torquey as a b16a, but for $4, who's complaining?

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Originally Posted by dupac->

not worth it.

not every car needs to be modded.

wait til u get something with more grunt
then mod that for even more grunt i guess.

IMO not worth it.

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what dupac said is pretty much true.. but yeah it all depends on you man, like i always say.. if ur happy with what ur doing, then no one is stopping ya.

take it easy

... no point at all. Save the money for a better car

there are cheap carby mods - i wouldnt spend much money though on that model

http://www.ozhonda.com/forum/showthr...ght=carby+mods

commodores suck balls. my vs acclaim has like a 3.8litre v6 putting out a full 145kw at the flywheel. as we all know a k20a has around 160kw in a 2litre 4 cylinder. japanese>australian

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Originally Posted by nick_sixx

commodores suck balls. my vs acclaim has like a 3.8litre v6 putting out a full 145kw at the flywheel. as we all know a k20a has around 160kw in a 2litre 4 cylinder. japanese>australian

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I don't see what the k20a has to do with the 1990 Civic? It has a dual carb motor puttin out 70kw - that is what he is comparing the Commodore to.

Misread or Wrong Thread? lol

thank you all a lot for your clear answers. i will not modify it then! saving up for a nissan pulsar gtir..

it's up to u in the end whether its worth it or not....imo, its not a very good car to mod

GTiR better than dropping in a B series...

My mate had a car like urs, only JDM ef2, but ill tell you he didnt really do any mods, he modded the airfilter a bit, sounded good... love the carby backfire tough as nuts! ill let u know when we went up to dande mountains together that guy was unstopable! i couldnt ever keep up with him! even when i got my brothers mr2 turbo out! ahahhaha
just keep in mind, every car has a different purpose, a GL ED civic is a great training car! love the shape to!

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Originally Posted by revilodraw

thank you all a lot for your clear answers. i will not modify it then! saving up for a nissan pulsar gtir..

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Nissan Gti-R, pretty fast car, has small breaks, and very very weak gear box. Well, it has a lot of power but its 4wd, and when too much power is run thru the tranny the gearbox goes. As opposed to a 2wd when too much power is run thru the tranny, the wheels spin

I reckon your car's worth modding if you intend to keep it for a while. Do you like the car for what it is. I reckon they look pretty good and they make a great sleeper. I was on my way home from a mates place in my siR and bunch of retards in a vr commodore with p plates on it started laughing at me (I had my mags on). I know it's frowned upon here but mate if I had the chance to line up with them.........

GTiR...
FOr the price of 1 plus $$ to fix it when it breales down u could get urself a reliable B18c converted EG..
Looks bettter and wont spend as much time off the road..

well the ef chasis is light weight its definetly under 1000kg. think if u put in a b16a or a sohc vtec it should have some decent go. even could put a zc dohc engine in it too. i think they look pretty tuff lowered on some nice 15 inch racing rims. if you plan on keeping it then i think its worth modding it.

replace the shocks and springs. a nice bucket seat or seats from a crx. zc or sohc vtec engine if your're on a budget. b16a or b18c if you have a bit of money to spend. i/h/e and you would have a pretty decent sleeper. also you could strip some of the interior out.

if i wanted to build a budget track car i would choose a ef civic or crx i reckon.

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Originally Posted by locote

GTiR...
FOr the price of 1 plus $$ to fix it when it breales down u could get urself a reliable B18c converted EG..
Looks bettter and wont spend as much time off the road..

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yeah, trust me, i would never recommend a gtir unless you were getting it new, or with a brand new gearbox. one of my mates spends a fortune on filling fluids for the trans/clutch every week it needs a top up.
another one told me his gtir would be fine, because he's just had the gearbox rebuilt..... guess what happened later on that night?

Although it hasn't got the grunt, but if u mod the sussy and get some sway/strut bars, those things can really out handle most stock cars, especially your dad's commodore! And these parts are so easy to source since u have an EG.
If u got the cash then u might wanna chuck in a new engine or wat not.

but until then, concentrate on wat your car can do best, Handling!

do minor mods like air filter, maybe a 2nd hand catback at most. And learn and master how to handle a honda well. Its a gd car to trash about and still have gd reliablity. After that you will be ready for the the GTI-R. Btw why GTI-R.. unqiue but.. a STI wil be better IMO. gd luck.

Save up and get a DC2R, DC5R, S2000, NSX! Real tuned race cars.

Don't bother modify a slow car, you spend too much for too little. Better yet just get a turd-boh car, not that im a turd-boh fan. :thumbdwn:

mm prob not worth it, just save up for a better base engine!

in the meantime! lol buy one of those fake blow off valve sounds!

they will make you give you heaps of (pseudo)hp!

bro don't bother doing your carby up!!! save that money for a engine conversion! and you won't regret when you look back!=D

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Originally Posted by K20aCivic

bro don't bother doing your carby up!!! save that money for a engine conversion! and you won't regret when you look back!=D

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there's nothing wrong with modifying a carby engine. the americans are able to make 170whp with relatively light and cheap mods. you can buy engine kits at from the sponsors at www.onecamonly.com for dirt cheap. the kits make it relatively easy to get the compression ratio in the 13s for less than a grand, as well as improving durability and the ability to cope with up to 10krpm. if you head down this path, you can match the power of a b16a, and it will cost less than doing a conversion to one. plus you get the better atomisation rate of a carby.

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Originally Posted by SeverAMV

there's nothing wrong with modifying a carby engine. the americans are able to make 170whp with relatively light and cheap mods. you can buy engine kits at from the sponsors at www.onecamonly.com for dirt cheap. the kits make it relatively easy to get the compression ratio in the 13s for less than a grand, as well as improving durability and the ability to cope with up to 10krpm. if you head down this path, you can match the power of a b16a, and it will cost less than doing a conversion to one. plus you get the better atomisation rate of a carby.

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Don't listen to what the Americans say. There dynos readings are way out:thumbdwn:

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Originally Posted by SeverAMV

there's nothing wrong with modifying a carby engine. the americans are able to make 170whp with relatively light and cheap mods. you can buy engine kits at from the sponsors at www.onecamonly.com for dirt cheap. the kits make it relatively easy to get the compression ratio in the 13s for less than a grand, as well as improving durability and the ability to cope with up to 10krpm. if you head down this path, you can match the power of a b16a, and it will cost less than doing a conversion to one. plus you get the better atomisation rate of a carby.

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thats soo awesome, yankee's can do 170whp, did they mention that's for a v8? hahaha
ps. i also dont think you can improve reliability by increasing the compression, this increases wear and tear, and this reduces reliability. also, reving to 10k? if this were more reliable, dont you think the dc5R would rev this high?

@IZY-10 - ahh, but the 14.00 second quarter mile timesheet speaks for itself, especially when its run consistently.

@AzKik-R - its not from a v8, its from a d15b4 jdm with a quad 45mm weber conversion, full high compression kit, new valvetrain and new cams running a compression ratio in the 12s.
and theres a difference between factory components and aftermarket components. factory components in a dc5r are tuned in case the owner accidently puts in 91 octane fuel instead of the 98 stuff. once its tuned properly with the right internals, they can go much higher. as an example, one of the spoon sports tuned integras run well into the 11k. and since the parts are more durable, yes, they can handle the higher compression. if it were just shaving the block, then yes, it would be more unreliable, but its replacing almost every component as well as throwing in a block guard. its also still an atmo so it wont be under as much stress as a turbo'd engine.

If a carby motor is so good why aren't car manufacturers still using them? The car probably weighs nothing. If you have the same mods to a EFI motor i wonder witch would make more power???

rushi on www.onecamonly.com has a similar setup except on an efi motor in the same chassis. only makes about 8whp more. but its not so much about the power, its moreso about the response you can obtain from such a setup. and yes, they do it without vtec as well, as vtec is somewhat restrictive after a while on a performance basis in an sohc motor (its only really good on a dohc motor).

only reason why people dont use carby motors in new cars nowadays is because theyre not good at adapting to situations (like temp change), whereas with efi, the computer can adjust accordingly.

and carbs do atomise better. it would take a turbo and approximately 3 feet of intake piping to match the atomisation rate of a weber carburetor. the better the atomisation rate, the better the contact between air and fuel, which leads to better combustion and potentially more power.

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Originally Posted by IZY-10

If a carby motor is so good why aren't car manufacturers still using them? The car probably weighs nothing. If you have the same mods to a EFI motor i wonder witch would make more power???

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Mostly because it's impossible to meet modern emission control requirements with carbies. If it wasn't for the imposition of stricter and stricter emission controls then we'd still mostly be using carburettors, at least on cheaper cars.

And even with more expensive cars, the injection wouldn't be either as good or as reasonably priced as it is now mostly due to the development the manufacturer's have been forced to undertake to meet emissions on their mass market cars.

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Originally Posted by SeverAMV

and carbs do atomise better. it would take a turbo and approximately 3 feet of intake piping to match the atomisation rate of a weber carburetor. the better the atomisation rate, the better the contact between air and fuel, which leads to better combustion and potentially more power.

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Not my understanding. One of the attractions of fuel injection is the superior atomisation compared to even very good carburettors. With injection you have fuel being pumped at fairly high pressure through a tiny orifice, and this creates good atomisation. With carbies you have fuel being 'pushed' through a number of larger orifices only by the pressure differential between atmospheric pressure in the float bowl (higher) and venturi pressure (lower).

This pressure differential with a carby is way less than the pressure in the injection rail, and accompanied with the larger orifices through which the fuel passes results in poor atomisation compared to injection. .

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Originally Posted by sik-vic

well if your actually serious..............................
canon mufflers a a waste of time

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'Cannon' mufflers, or at least the cannon exit from the muffler are a waste of time on anything. You don't need the outlet to be much if any bigger than the muffler inlet.

Those 'cannons' mark you as a bit of a poser to more serious people who know that they are only for show and actually do nothing (you won't see exhaust tips nearly as large as some of those cannon ends on a serious racer, even with a large capacity). Having said that the cannon end doesn't actually hurt, so long as the muffler to which it's attached is basically a good muffler.

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Originally Posted by sik-vic

with a carby car cause they need more back pressure,

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Lack of back pressure (i.e. a non restrictive exhaust) is important to any application where power is important and noise less so. Makes no difference if injected or carburreted

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Originally Posted by JohnL

'Cannon' mufflers, or at least the cannon exit from the muffler are a waste of time on anything. You don't need the outlet to be much if any bigger than the muffler inlet.

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X2
:thumbsup:

i'm currently running 4-2-1 x-force headers, stock cat, custom 2.25" catback...its no cannon but it sounds ok...

when i still had the stock header the sound was a bit more raspy...but with the new headers the sound is more warm and round...




i've just done the baking tray mod (hehehe) and fiddled around with the bracket that holds the throttle cable and got my idle sitting at 1100...
it goes nice with the lower pressure exhaust...

u'll be happy with the difference in response

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Originally Posted by SeverAMV

@IZY-10 - ahh, but the 14.00 second quarter mile timesheet speaks for itself, especially when its run consistently.

@AzKik-R - its not from a v8, its from a d15b4 jdm with a quad 45mm weber conversion, full high compression kit, new valvetrain and new cams running a compression ratio in the 12s.
and theres a difference between factory components and aftermarket components. factory components in a dc5r are tuned in case the owner accidently puts in 91 octane fuel instead of the 98 stuff. once its tuned properly with the right internals, they can go much higher. as an example, one of the spoon sports tuned integras run well into the 11k. and since the parts are more durable, yes, they can handle the higher compression. if it were just shaving the block, then yes, it would be more unreliable, but its replacing almost every component as well as throwing in a block guard. its also still an atmo so it wont be under as much stress as a turbo'd engine.

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hmmm, I'm a little lost here, how many new cams are you putting into the sohc engine? I think off hand if my memory serves me right, you can only put 1 in there? (I may be wrong here)
and the other statement that has me baffled is are these really 'light and cheap mods'?
and what sort of light mods would i need to get my b18cr up to 10k rpm? I think it might need me to open the engine up, and change some parts? I cant really see that as being a cheap or a light mod?
further to this is.... my b18c dc2r does i think mid 14's down the 1/4 mile. thats the 1.8l, and here you have the 1.5l running 14's. I'm almost considering doing an engine swap with my type r engine, and drop in a d15b4, seams to be the superior of the two

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Originally Posted by VT1-R

if u love ur existing car and wan it to be fast and not get laughed at by these guys.. put in a b16.. or even a b18.. no point modifying a carby.. i use to have a carby lancer.. i did the exterior up.. all was all show no go.. i got sick and went honda with b16.. it moved up into a new lvl..

go to honda B series.. u get respect and u will nv regret..

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Ahhh, the CC Lancer GL. That 4G15 made slow look fast.

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Originally Posted by cristian

when i still had the stock header the sound was a bit more raspy...but with the new headers the sound is more warm and round...

i've just done the baking tray mod (hehehe) and fiddled around with the bracket that holds the throttle cable and got my idle sitting at 1100...
it goes nice with the lower pressure exhaust...

u'll be happy with the difference in response

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i bought the megan racing extractors that were listed for $17 on ebay. pretty darn good for $17, altho as expected, theres a limit to how much you can gain on a 1.5L motor. i love how nice the induction sounds with the baking tray mod, it really roars with the extractors and exhaust. and thru experimenting with the same throttle cable that you've started playing around with, i notice you can get the carb throats to open up a little bit more, which made me think they didnt let it open up fully to begin with to keep th power down. on my motor, i removed the choke cable and bumped the idle up to 1100, so my car doesnt stall when cold starting, and so i dont get the added restrictiveness of a choke cable. i noticed on mine when tracking it that if i had the idle set at 1500rpm, the power comes on much more freely, probably because i dont have to go thru any of the lag i would normally have to in the 1-2krpm range.

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Originally Posted by AzKik-R

hmmm, I'm a little lost here, how many new cams are you putting into the sohc engine? I think off hand if my memory serves me right, you can only put 1 in there? (I may be wrong here)
and the other statement that has me baffled is are these really 'light and cheap mods'?
and what sort of light mods would i need to get my b18cr up to 10k rpm? I think it might need me to open the engine up, and change some parts? I cant really see that as being a cheap or a light mod?
further to this is.... my b18c dc2r does i think mid 14's down the 1/4 mile. thats the 1.8l, and here you have the 1.5l running 14's. I'm almost considering doing an engine swap with my type r engine, and drop in a d15b4, seams to be the superior of the two

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1 cam, just sounds better when i say cams. and yeah, its relatively cheap mods since you can get the parts for under 1k, and labour will be under 1k as well, and from most places, it includes dyno tuning (carbs are much easier to dyno tune). compared to around 5k minimum-ish for a b16a conversion, yeah, its pretty cheap and good bang per buck. for a dc2r, its not cheap because everything costs an arm and a leg for a dc2r or dc5r, for a nearly 20 year old civic, parts are dirt cheap, like $10 strut braces and traction bars, $500 coilovers, and the other day, i found someone selling 4-2-1 megan racing extractors (stainless steel), plus stainless steel catback exhaust system for $50. look around on ebay, you'd be suprised how cheap you can get parts for a civic.
and the reason why these cars can run such good quarter mile times is because they weigh around 825kg from the factory, stripped out you can get close to 700kg chassis weight, altho without a stripped chassis, it will probably run mid to high 14s. i've tried to keep weight down in my car by going without a sub, and with soundstream tarantulas, i dont really need a sub.

how bout....
for $7500 why doesn't someone just buy this?
http://www.automarket.com.au/vehicle...hicleNo=254605
hmmm, must be a typo or something!!!

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Originally Posted by AzKik-R

how bout....
for $7500 why doesn't someone just buy this?
http://www.automarket.com.au/vehicle...hicleNo=254605
hmmm, must be a typo or something!!!

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lol, f*** yeah, i'd take that for 7.5, haha

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Originally Posted by AzKik-R

how bout....
for $7500 why doesn't someone just buy this?
http://www.automarket.com.au/vehicle...hicleNo=254605
hmmm, must be a typo or something!!!

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its not worth it! if you want to go fast get a carby;)

yeah, i hear it has better atomization :D

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Originally Posted by JohnL

Mostly because it's impossible to meet modern emission control requirements with carbies. If it wasn't for the imposition of stricter and stricter emission controls then we'd still mostly be using carburettors, at least on cheaper cars.

And even with more expensive cars, the injection wouldn't be either as good or as reasonably priced as it is now mostly due to the development the manufacturer's have been forced to undertake to meet emissions on their mass market cars.

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agreed.

Carbys are great for dumping loads of fuel into the engine ie big v8's, i think top fuel & funnies still use them, injectors are restricted to their rating ie 380/450/550/1000cc

injected engines can also run upside down :D and do not rely on gravity
as technology evolves injected is the cleaner more precise/stoich method

from what i can understand about the physics of it, carbs have better atomisation due to the non-stop intake flow, whereas with efi you gotta wait for the spray. most drag racers tend to use carbs because it has better atomisation, physics of it seems hazy, but they seem to be able to make their cars go faster with carbs, so obviously something is going right.

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Originally Posted by SeverAMV

from what i can understand about the physics of it, carbs have better atomisation due to the non-stop intake flow, whereas with efi you gotta wait for the spray. most drag racers tend to use carbs because it has better atomisation, physics of it seems hazy, but they seem to be able to make their cars go faster with carbs, so obviously something is going right.

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and this has plus points for the speedy delivery of the fuel to the chamber :D
there is one problem, being that the valve's are not always open, sooo while the fuel is still spreying everywhere and the valve is closed, where does the atomized fuel go to?
injectors are part of the EFI electronic fuel injection system
they squirt the fuel at the time that the valve is open, they aim the fuel directly into the engine, and then stop spreying the fuel when the valve is closed.
this is how injectors are a cleaner more precise or stoich method of fuel delivery.
stoich is something like 1:14 fuel:air or 14.3, cant remember off hand, any more fuel then this is running it rich, and less fuel is running it lean, lean leads to pre-ignition. stoich is optimal, and very little benefit is found from runnnig too much higher then stoich.
cars like top fuel's dont run a complete combustion cycle, they're very in-efficient, because they just dump fuel into the engine like you wouldn't believe haha

we are talking 4cyl carbies here though. A V8 carby i must admit you can not beat the sound they make as well as power

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Originally Posted by AzKik-R

and this has plus points for the speedy delivery of the fuel to the chamber :D
there is one problem, being that the valve's are not always open, sooo while the fuel is still spreying everywhere and the valve is closed, where does the atomized fuel go to?
injectors are part of the EFI electronic fuel injection system
they squirt the fuel at the time that the valve is open, they aim the fuel directly into the engine, and then stop spreying the fuel when the valve is closed.
this is how injectors are a cleaner more precise or stoich method of fuel delivery.
stoich is something like 1:14 fuel:air or 14.3, cant remember off hand, any more fuel then this is running it rich, and less fuel is running it lean, lean leads to pre-ignition. stoich is optimal, and very little benefit is found from runnnig too much higher then stoich.
cars like top fuel's dont run a complete combustion cycle, they're very in-efficient, because they just dump fuel into the engine like you wouldn't believe haha

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ideally its 14.7:1 air to fuel, but most motors only get around 12:1 from factory, and thats efi motors included. this is probably due to air being mostly nitrogen, whilst fuel needs pure oxygen to combust ideally.
at the speed motors rotate at, the bottlenecking isnt quite noticeable, and it can be quite useful for instantaneous response spikes, but with vacuum physics, the bottlenecking is minimised as it only sucks in the mixtures when the valves are open, much like injectors only spray when the valves are open.

i'll admit carbs arent quite efficient at producing more power from less fuel like efi motors, but carbs can be pretty good power wise. downside with carbs is you cant have both fuel economy and power, its either one or the other.

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Originally Posted by SeverAMV

from what i can understand about the physics of it, carbs have better atomisation due to the non-stop intake flow, whereas with efi you gotta wait for the spray. most drag racers tend to use carbs because it has better atomisation, physics of it seems hazy, but they seem to be able to make their cars go faster with carbs, so obviously something is going right.

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There's no waiting with an injector, it fires precisely when the cylinder needs it, in the quantity required, already well atomised and then further atomised by turbulence. With a carby the fuel leaves the jets in a fairly un-atomised state, then largely relies upon turbulence to do the rest. The constancy of the carby air flow may help to some very slight degree (doubt it though), but won't make up for the other defecits.

Also, the best carby set ups are generally considered to be those that provide a dedicated venturi per cylinder (e.g. multiple Webers, Dellortos, Amals, Mikunis, Keihins etc), so these venturi and their jets will see just as pulsating an air flow as the injectors on a multi point EFI set up, which tends to upset the constant flow theory...

I know someone will say 'but what about Holleys etc', but IMO this sort of carb generally isn't quite as good as single choke per cylinder set ups, and are largely used because a common plenum chamber is easy to package on 'V' engines, and thus a multiple choke single carb is easier to use with quite good results.

I once saw a GTHO Falcon fitted with four 50mm DCOE Webers on manifolds that criss-crossed above the engine, could barely see the engine for carbs and plumbing! That car was truly ferocious. Ferrari used DCOE Webers on all their carburetted 'V' engines, I once did some work on a 365GTC4 with six of them, and I can tell you the carbs got in the way of doing just about anything on that motor!

I'm not really up on drag racing (not my cup of automotive tea), but I vaguely recall that at least some of the classes use carburettors because it's mandated in the rule book(?).

There's no reason you can't make as much (or nearly as much) power with a carb as with EFI, but it will tend to be over a more restricted rev range and the response to changing conditions won't be as good. It's relatively easy for a carb to give optimum power over a narrow rev range, harder to do it at just above idle all the way to the red line, and harder still to do it with good fuel consumption and emissions.

coincidentally, i managed to get my hands on a pair of dual sidedraught skracing carbs, dcoe40. apparently they integrate the best bits of the mikuni and weber designs so they shouldnt be too bad for my d15b. (i'd have bought genuine dcoe45 webers if they didnt cost half a motor each).

but yeah, these are purely mechanical carbs so they cant adjust to change in conditions as well as the keihin cv carbs already in the civic. but as i recall, one advantage of running carbs is the simplicity of the tuning for high revving applications. with most efi ecu's that are capable of handling high revs (say 10krpm), you need to program in the entire fuel map up to that point in the rev range, whereas with the carbs, you just tune it so it can supply enough fuel at that revs, and it will be able to perform decently at those revs (albeit a little richly until then).

but for street driving and daily driving, its better to tune it for a more narrow but useable rev range as JohnL has stated. why tune a daily driver motor for 10k rpm when you probably wont even hit anywhere near that on the street. imo, for street applications, its best to tune for good bottom end and midrange response, because frankly, how often does anyone stay in the top end before upshifting?

im not too sure about the calculations with regards to the atomisation rate of carburetor over efi, but someone on the d series forums should be able to shed some light on it.

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Originally Posted by AzKik-R

and this has plus points for the speedy delivery of the fuel to the chamber :D
there is one problem, being that the valve's are not always open, sooo while the fuel is still spreying everywhere and the valve is closed, where does the atomized fuel go to?

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You mean the un-atomised fuel? It partially collects on the plenum and manifold walls and then dribbles into the various cylinders in uncontrolled quantities, and in different uncontrolled quantities in different cylinders. The un-atomised (or poorly atomised) fuel is also in relatively heavy droplets that in engines with a single carb are pulled this way and that with changes in air direction as the different valves open and close, but since the droplets have relatively high mass they tend to get 'left behind' by the airflow and end up not being evenly distibuted into all the cylinders.

Old straight six Holden engines were notorious for this, i.e. cylinders 1 and 6 would run rich and the others progressivly nearer the middle run lean and leaner. This happened because the heavy droplets would rush along the manifold but then fail to turn the sharp corners as they passed the openings to the middle cylinders, and more fuel ended up in the end two cylinders. This wasn't helped by the manifold passages for cylinders 3 and 4, whereby the air / fuel had to negotiate a cast-in baffle that meant the mixture had to initially travel toward each end of the manifold but just before the port openings for cylinders 2 and 5 had to make a sharp 180° turn before heading back toward cylinders 3 and 4! Needless to say cylinders 3 and 4 generally ran lean, especially at higher rpm (or what passed for high rpm with these engines), and the fuel that should have gone to cylinders 3 and 4 ended up in 1, 2, 5 and 6 (mostly in 1 and 6).

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Originally Posted by AzKik-R

stoich is something like 1:14 fuel:air or 14.3, cant remember off hand, any more fuel then this is running it rich, and less fuel is running it lean, lean leads to pre-ignition. stoich is optimal, and very little benefit is found from runnnig too much higher then stoich.

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Except under harder acceleration, a richer than stoichiometric mixture (yes, I looked up the spelling!) up to a point produces more power, but at the expense of fuel economy. When cruising you want a perfect stoichiometric ratio as you don't need max power but you do need max economy.

A stoichiometric ratio occurs when all the fuel and all the oxygen is consumed in the reaction (burning) with none left over unused. For petrol and air this ratio is roughly 14.7 X the mass (weight) of air to fuel mass. A ratio less than 14.7 of air to 1 of petrol is rich, and more than 14.7 to 1 is lean (looked those numbers up too, just to be certain you understand!).

I don't know what is considered to be the ideal ratio for a rich mixture for hard acceration, it's substantially richer but there is a point at which power starts to drop away, and I'm pretty sure this is very different for different fuels or blends.

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Originally Posted by AzKik-R

cars like top fuel's dont run a complete combustion cycle, they're very in-efficient, because they just dump fuel into the engine like you wouldn't believe haha

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Way over stoichiometric, so much that drag engines are often in danger of destroying the engine due 'hydraulicing' on fuel if something goes even a little bit wrong. Keep in mind that the brews used in drag racing are usually quite exotic and are obviously intended to be run at very rich ratios.