Carbs over K-Jet

[mattnorgrove 0]

What are the pro's and con's of fitting carbs (Dellorto and the like) to a KR?

 

What kind of power gains could be achieved, if any?

 

Thanks in advance peeps!

 

Oh, and has anyone done this to their C (KR or 9A)?

 

Cheers...

[KeithC 0]

If you fit a set of cams aswell as the carbs you should see a nice difference.

I'm will running my 9a on ITB's with 285degree cams plus fully gas flowed head,

should be up in the region of 190, 200 bhp.

[flusted 0]

to a kr... nothing

[mattnorgrove 0]

to a kr... nothing

 

How come nothing on KR, but 190-200, with gas flowing etc on a 9A?

 

Excuse my ignorance... :D

[davidwort 0]

I've still never actually seen a carbed 16v develop that sort of power, whenever they've been at a rolling road day there's always some excuse why they're only delivering half the power they should be.

 

K-jet is:

a) pretty reliable

b) needs little adjustment for a more tuned engine

c) delivers good power and despite what people think good economy

d) is good for 200bhp provided you've got the engine to achieve that

 

carbs are:

a) expensive to buy (and will probably increase your insurance if you declare them)

b) hard to find someone who can set them up (re-jetting for engine work etc.)

c) drink fuel

d) never seem to live up to the promises

e) prone to icing in damp/cold conditions

[vwdeviant 0]

I've still never actually seen a carbed 16v develop that sort of power, whenever they've been at a rolling road day there's always some excuse why they're only delivering half the power they should be.

 

K-jet is:

a) pretty reliable

b) needs little adjustment for a more tuned engine

c) delivers good power and despite what people think good economy

d) is good for 200bhp provided you've got the engine to achieve that

 

carbs are:

a) expensive to buy (and will probably increase your insurance if you declare them)

b) hard to find someone who can set them up (re-jetting for engine work etc.)

c) drink fuel

d) never seem to live up to the promises

e) prone to icing in damp/cold conditions

d) Sound awesome at full chat.. induction roar not something easily reproduced by k-jet

[mattnorgrove 0]

Cheers for the replies gents, appreciated as ever...

[flusted 0]

carbs sound loverly agreed, but think they are sucking in loads of hot air from the rad and zapping power :shock:

[vwdeviant 0]

Matt, there's some one on here doing a bike carb conversion.. Can't remember his username but has a white rado... sure he'll be by soon...

 

I know of a 2.0 Audi 80 running then now and is sweet apparently.....

[Kevin Bacon 5]

Don't confuse carbs with throttle bodies.....

 

Bodies with EFI injection can make the power. Carbs can make the power too if correctly sized and setup properly, but carbs need frequent retunes as they are no where near as good at automatic compensation as modern EFI.

[mrbeige 0]

Friend of mine fitted a set of GXR bike carbs to a standard 9a block with a KR inlet cam and saw 171bhp. I thought that was pretty bloody good. Sounds awesome too.

[Kevin Bacon 5]

Not keen on bike bodies personally. Some of them have a massive change in flow for a small opening, which can be a nuiscance on a road car.... that's a good result though! What was the torque?

[rolex 0]

Friend of mine fitted a set of GXR bike carbs to a standard 9a block with a KR inlet cam and saw 171bhp. I thought that was pretty bloody good. Sounds awesome too.

 

is he on a forum? with a build thread?

do you know what sort of torque he got?

 

Thanks.

[dubcharger 0]

If u have the timing advanced correctly for the fuel you're using, k-jet and ke-Motronic sound and go pretty well too :wink:

[boost monkey 0]

to a kr... nothing

 

I don't believe for one second that the K-jet system and bendy inlet manifold on a stock 9A/KR flows exactly the same as a set of twin carbs. The airflow alone is dramatically increased (whether it is hot or not)due to the fact that there is one inlet per cylinder as opposed to one inlet for all 4 on the stock setup.

 

carbs sound loverly agreed, but think they are sucking in loads of hot air from the rad and zapping power :shock:

 

Agreed that increased intake temps reduce charge density resulting in a loss of power, but it is quite easy to rig up a heat shroud that detours the radiator airflow with fan on down and past the intake for carbs. Literally just a sheet of metal attached to slam panel and angled downwards towards the block.

 

K-jet is:

a) pretty reliable

b) needs little adjustment for a more tuned engine

c) delivers good power and despite what people think good economy

d) is good for 200bhp provided you've got the engine to achieve that

 

very true. There's a few peeps on CGTI who are getting good power out of the K-Jet. Even though it's old and mechanical, it can be tweaked quite well and can def make over 200hp as David says.

 

carbs are:

a) expensive to buy (and will probably increase your insurance if you declare them)

b) hard to find someone who can set them up (re-jetting for engine work etc.)

c) drink fuel

d) never seem to live up to the promises

e) prone to icing in damp/cold conditions

 

I'd say finding people willing to set up carbs is easier than finding those who can! definitely agreed on carb icing though:

 

As petrol is a solvent, it evaporates at room temperature. As external ambient temperatures drop, the solvent part of the petrol evaporates leaving the water to glaze the carbs surfaces and when the temperature is low enough it turns to ice. The petrol keeps evaporating and the ice keeps building up so that the inlet diameter gets smaller and smaller and the engine starts getting choked.

 

That's why, for sake of an example, my 8v carb jetta engine has a heated inlet manifold (coolant flows through it) so that the carb is always running slightly warm to stop this from happening.

 

^^ feel free to corect this anybody.

 

Don't confuse carbs with throttle bodies.....

 

Bodies with EFI injection can make the power. Carbs can make the power too if correctly sized and setup properly, but carbs need frequent retunes as they are no where near as good at automatic compensation as modern EFI.

 

Yeah completely. Carbs are affected way more by ambient temperature (and air density) so ideally need setting up at least every summer (low air density) and winter (high air density) because they are mechanical and as such don't adjust as ITBs with a air flow sensor etc would do.

 

Hope this helps any,

 

Jon :)

[dubcharger 0]

 

I don't believe for one second that the K-jet system and bendy inlet manifold on a stock 9A/KR flows exactly the same as a set of twin carbs. The airflow alone is dramatically increased (whether it is hot or not)due to the fact that there is one inlet per cylinder as opposed to one inlet for all 4 on the stock setup.

it wont flow quite as much but there is only one cylinder sucking air in at a time,unless you have wild cams in there that start opening the valves at all types of angles :lol:

[boost monkey 0]

ha ha yeah!

 

IIRC, the std head doesn't flow well enough to use 45s on it, but 40s fuel quite nicely (obviously with the correct jetting and setup)

 

J