[Tillson]

Really need to know pro's, con's and rough sorta prices. its for a vauxhall 2.0 8v engine...also twin 40's and twin 45's what is this all about? :lol:

[longeatonlad]

carbs- twin 40's will be the better option for that engine imo, the 45's will be slightly bigger, and more expensive too. carbs are pretty delicate, and need servicing every so often.

throttle bodies- the better pick if you have the cash, more uptodate than the carb set up, although need to be used with aftermarket ecu, and will require mapping to get the best out of them. jenvy are the daddy...

all depends how much money you have to play with tilly, twin 40's can be picked up from 50 quid anywhere upto about 500 brand new.

throttle bodies, ive seen a few set ups around for the 1k mark...

[syrover]

longeatonlad, on 09 March 2010 - 10:37 PM, said:

carbs- twin 40's will be the better option for that engine imo, the 45's will be slightly bigger, and more expensive too. carbs are pretty delicate, and need servicing every so often.

throttle bodies- the better pick if you have the cash, more uptodate than the carb set up, although need to be used with aftermarket ecu, and will require mapping to get the best out of them. jenvy are the daddy...

all depends how much money you have to play with tilly, twin 40's can be picked up from 50 quid anywhere upto about 500 brand new.

throttle bodies, ive seen a few set ups around for the 1k mark...

Ask Mickpm about throttle bodies as he has dabbled.
Twin 40's ... i may know of a set for sale... but feck me they aint cheap these days.

[friendly1_uk]

they breathe easyer, so flat out power is increased. The noise is generally better too. Complex manifold shapes serve to aid torque though. without the assistance of a well designed manifold you will be slower off the mark.

[John]

The difference between 40s and 45s is 5mm per opening.

It's not though. lol

Each opening may be 5mm bigger but in that opening you have a choke,Carbs need chokes to create a slight vacuum over the fuel jet to suck fuel through the carb. Chokes can be anything from 30mm to just a few milimetres smaller than the opening of the carb.

If you pick 45s and put 32mm chokes in then you'll be able to flow as much air as 32mm chokes allow....the same amount as if you had 40s with 32mm chokes. It does affect jetting but unless you need more than 34mm choke, 40's will suffice. You'll hear people say things like '45's are too big for that engine' - it's bollocks as usual.

IIRC 34mm chokes will flow enough for somewhere in the region of 150-160bhp. Don't go by your original carb...if you have 4 32mm chokes (two twin 40s for example) replacing your 32mm single choke standard carb...you're not able to flow 4 times the amount of air through the engine.

Rich is right, having throttle bodies whether carb or injection can reduce low end grunt quite a bit. It slows the intake air quite a lot and as a result you lose torque until that intake stream speeds up at higher RPMs.

The only performance advantage with having throttle bodies is you no longer need chokes. That improves flow.


To tune a carb setup you need to pick the right chokes (about 10-15 quid each but they can be machined out for slightly less)...main jets, idle jets, emulsion tubes and pump jets. They're f*cking easy to work on but a set of jets and chokes could run you to £100.

To tune a throttle body setup you need a laptop, mappable ECU, knowledge of the software and knowledge of mapping.


I actually quite enjoy carbs....whack a wideband lambda gauge in your car, go for a blast, see where the fuelling is out and 'adjust' the jet accordingly. Much more enjoyable than mapping...mapping uses computers.

[friendly1_uk]

for a 34mm choke a 40 beats a 45 because of the trumpets. a wider intake offers less resistance, so to tune to the same resistance they have to be longer. Looking at a 40&45 trumpet used to offer the same resistance you find the shorter thinner one causes the air to move faster which gives peak torque at lower engine speeds, and over a wider area of the map

I read a car mag article on it years ago. 2.0 pinto using 34s in both 40s n 45s. The 40s were better. The 45s are too big. Mathmatically and in some possible cases physically. However in later years we have come to expect more from a carbed 2.0 and so 45s tend to be fitted.

tbh i would avoid carbs. Big money. Regular tunes. Possible emmisions nightmare. Bodys are an injection system and there is no doubt that injection is much better behaved. Still bloody expensive though, and i would avoid that too. People spend turbo money on bodys. Litterally. So you have to really want them for nasp competition reasons or the noise.

If its power you want, from a proven 'spanners only' approach, then a turbo conversion using another car makes good sense. Its all off the shelf and works. No fabrication or mapping work.

This post has been edited by friendly1_uk: 10 March 2010 - 03:32 PM

[syrover]

Holy crap .. I wondered why google packed up earlier ...

[Xploit]

lol^

"Why would anyone go back to carbs" Is what i get out of my Dad on the subject...

[friendly1_uk]

syrover, on 10 March 2010 - 03:56 PM, said:

Holy crap .. I wondered why google packed up earlier ...

dang. do you need google to take a sh*t? :lol:

This post has been edited by friendly1_uk: 10 March 2010 - 05:27 PM

[John]

friendly1_uk, on 10 March 2010 - 03:31 PM, said:

for a 34mm choke a 40 beats a 45 because of the trumpets. a wider intake offers less resistance, so to tune to the same resistance they have to be longer. Looking at a 40&45 trumpet used to offer the same resistance you find the shorter thinner one causes the air to move faster which gives peak torque at lower engine speeds, and over a wider area of the map

I read a car mag article on it years ago. 2.0 pinto using 34s in both 40s n 45s. The 40s were better. The 45s are too big. Mathmatically and in some possible cases physically. However in later years we have come to expect more from a carbed 2.0 and so 45s tend to be fitted.

tbh i would avoid carbs. Big money. Regular tunes. Possible emmisions nightmare. Bodys are an injection system and there is no doubt that injection is much better behaved. Still bloody expensive though, and i would avoid that too. People spend turbo money on bodys. Litterally. So you have to really want them for nasp competition reasons or the noise.

If its power you want, from a proven 'spanners only' approach, then a turbo conversion using another car makes good sense. Its all off the shelf and works. No fabrication or mapping work.

It makes F*ck all difference really though mate. You would never be able to tell the difference between the 2 in reality. I don't care what the car mag says. lol
To give you an idea, the throttle bodies are regularly at least 45mm...and without chokes...nobody says they're too big. It's not about flow speed as such, it's about a stable vacuum over the jets and a nice throttle response....not the out and out ability to flow air.

I don't know what you're on about with resistance. It's about flow speed which has nothing at all to do with resistance. :lol: Trumpet length isn't really about flow either...it's about resonance. I won't bore you all with that sh*t though. :lol:
I do see what you're saying about having slightly longer trumpets on a bigger diameter runner..just to get the same air momentum. if the manifold is profiled correctly though the difference is marginal.

I would avoid the turbo route personally. It's supposed to be a touring car rep...turbo would ruin it. It needs a set of trumpets. Actually, it needs a V6 with 6 carbon fibre trumpets crossing each other. Rude.

This post has been edited by John: 11 March 2010 - 09:43 AM

[John]

friendly1_uk, on 10 March 2010 - 05:24 PM, said:

dang. do you need google to take a sh*t? :lol:

:lol:



Sy, i've done the lot mate...spent half my uni years in the library reading up on it all too - that's why I flunked at electronic engineering. :lol:

No google required.

This post has been edited by John: 10 March 2010 - 07:30 PM