KE20 SU Issues

[disco20]

http://www.toymods.net/forums/showthread.php?t=18560

 

Here is a link to my members ride thread on toymods. Its a ke20 3K with HS4's on the lynx manifold. I'm having a bugger of a time getting it tuned right. I'm no expert with SU's but I have learnt alot over the past few months while I try different things etc. I got this whole setup for $150 so thats why I am persisting with it hoping that one day I will get it right. So far I have replaced needles and seats, jets and jet needles and have ditched the mech fuel pump for a consistant flow rate of an elec pump. This has made a huge difference I have found.

 

The point I am at right now is that from 3000 rpm and up the engine stutters and hesitates alot. This is pointing me in the direction of the jet needle profile, but with over 300 needle profiles available for the SU's its very hard to find the perfect needle. I am guessing that the hesitation means there is not enough fuel being allowed in at that particular rev range as the engine demands more. I thought about it being too much fuel but I think instead of hesitating it would just die as the combustion chamber would get flooded.

 

Jet needles are not expensive but I get mine from wilson carburettors in airport west her in vic and the problem is that they are only open monday to friday and are about an hours drive from me. They also do not send anything in the mail which makes getting parts extremely difficult. Anyway enough of me blabbing on, have a look at my thread and see what u think. They do look very kool in the engine bay though and do give good performance when they are setup right.

Edited August 28, 2007 by Xany
Edited into paragraphs for readability

[philbey]

Have you rebushed the throttle shafts etc? From my musings, it seems that sloppy bushes (err, freudian slip?) are notorious for causing issues.

 

Also, the other common problem they have is dashpot oil, and people using the wrong oils etc. (water, detergent, engine oil). 150 bucks on a manifold, thats a steal!

Edited August 28, 2007 by Xany

[Xany]

Most people don't know a good carby bloke either.....trust me, spend the money and get them tuned PROPERLY, with either a dyno or a in car AFM gauge. You will save yourself alot of time that could be spent elsewhere (like drinking down at the local).....

 

Atm my hot 5K has twin 1.75 HS6's on it, i had them tuned by a good carby bloke i know up here in queensland....it took us nearly 2 Saturdays to get it right (mainly cause he had to get different needles in). Mine run a needle called an OA7, the lightest dashpot spring he could get (red) and no oil at all in the dashpots. After many hours road testing the car with an AFM Gauge in the cabin it was just right :D

 

Here's a little site i found helpful when looking up needles myself.

 

http://www.mintylamb.co.uk/suneedle/

[old corolla bloke]

[

 

suggest you do a plug colour test

 

don't forget to use new plugs

 

cheers brian

[kickn5k]

I have these things on my car i had it so close to perfect "i thought", then i take it to a place with a dyno that know twin carbs, they tuned it and it was a totally different car. it is really really worth getting someone to look at them.

These guys tune my car they are good with su`s but better with webers!!

Mammi motors

PH: (03) 59777973.

sommerville VIC

Gerald is the person you need to speak to.

hope that is some help.

[Felix]

Put a 4 wire O2 sensor in your exhaust and install an A/F meter. Makes carb tuning a breeze, as you can see what is happening in real time as you are driving.

[kickn5k]

I have read the toymods thread and i think i may have a few suggestions for you:

 

fuel pressure may be too high 1 1/2" su`s don't like anymore than 2 psi.

 

The breather on these carbies are a bit dicky any blockage in the breather will create a similar issue. I beat my head against the wall with blocked breathers for months.

 

stu.