Help any one who use weber or turbo expert
Turbo Mini Forums

At the moment I run a weber blow through turbo. The spec is as follow 1.5 roller rocker, Kent turbo cam, timing belt, gt valve.
The problem is that what size of jet, Emulsion tube, air jet, should I use
The engine is not running very smooth when there is boost. It is also very rich. The main jet is at 120, Emul: F9 and air jet is 200. I try to run it leaner but according to the weber spec this is pretty low alreadly. So please anyone can help me I would be very thankful.

http://www.geocities.com/jharkola/1380turbo4.html

Any more questions you are best asking Jukka directly - very knowledgable and helpful!

Which weber ? 40 or 45 ? Which chokes ? What fuel pressure ? What idle jets ?

At what revs is it rich ? If your mains are genuine 120 no way in H*** can it run rich. I would expect to see 120 mains in a std 850 engine. Typically a std 1275 needs mains around 150.

Jukka, the ledgend!

Team Racing

Since when ????

for years jukka.

Team Racing

First of all I would like to thanks very one for helping.
Jukka
First of all I would like to thanks very much for helping. As you ask it is 40 DCOE, the choke is 45. For fuel pressure at idel is around 5-8 psi. For the idel jet I not so sure about but i think it is standard from factory and I did not make any chages to this. The boost come around 3000rpm. This is the IHI turbo that use in the SUBARU Impresa. Cheers

40mm carb with a 45 choke?

i think you may be mistaken... :s

'I swear to use the Boost, The whole Boost'
'And nothing but the Boost..... So help me God'

Oh no I mean 25 so sorry for the wrong info

Dont know if this is of help, but my blow through 45 weber is jetted as follows,
38mm chokes
150 mains
120 air correctors,
f2 emulsion tubes
idle 50f2,

with 10psi produces 150hp

Your fuel pressure sounds a little high 2-3 psi at idle is all a weber dcoe requires. Maybe its over powering the float needle valve and over filling the float chamber, petrol will drain straight through the mains jets etc if this happens, I had this trouble with brass float that collapse under boost pressure.
Feel free to correct me Jukka

Phil

Minster, do you have restrictions at the carb intake like SU does ? Your main jets sound small to me, (especially considering the choke diameter) I´m running 190 at 10 psi and 200 were a touch lean at full throttle at 16 psi.

I agree with the fuel pressure, would set it at 3,5 psi max. As long as the fuel pump is supplying enough stuff there is no need to overload the float needle.

Did you do any tricks to seal your 45 ?

Weber, I am still confused about the choke size, I did not know that you could get the chokes that small... I would opt for 30 or 32 mm choke in 40DCOE and 34-36 mm choke in 45DCOE, depending on the intended use and expected power. For street use I would go to smaller choke for drivability, for silly power the larger. There is actually no need to go to choke sizes of n/a engines.

I wish I had the power figures that you guys quote, I am only seeing 140+ at 16 psi from a 1380.

Thanks for the info minster. What is your engine size? TO get that samll choke, I have it custom made. If i have it larger than this, at full throttle when at idel, the engine tends to choke for a little while then picking up later.

Yes I run 38mm restrictions at the carb mouth, nothing too fancy to seal it, just a rebuild kit, I have lately got a rubber gasket for the top plate, which seems better than the paper one. And one end of the throttle shaft is fully enclosed. So far no leaks.

Its jetted the same as it was when the engine ran naturally aspirated (apart from the air correctors, they are now 110 not 120 as I said previously, oops) Which suprised me.

Its 1293cc engine, 8.5:1 cr, ported head (minisport) tubular exhaust manifold, swiftune sw10 cam, t3, weber 45 on 6 inch inlet.

I have a power graph somewhere showing 127hp @ 6800 rpm with 6.5psi boost (Minisports rolling road)

How do you feel about the SW10 cam? I fitted one in my mate´s engine but since then he has had more interest in dating and mating than Minis... No real hard data how the cam works.

Max power is at quite high revs for the cam.

So far ive tried a Kent 286, a Avonbar turbo Phase 3 and the SW10 in the my turbo engine,

the sw10 is appears to produce more power (in the turbo engine), especially top end, There all of similar duration, but i believe the sw10 has less overlap, hence the improvement in power.

I cant say its any smoother low down (possibly a little) than the other two,

I think the high ish max power rpm is due to the head, the inlet, high lift rockers etc.

At the moment I'm thinking of buying the new cam. The cam that I have use before is Kent turbo cam. Is SW10 much better than the other. At idel what kind of rpm would this be. This because I live in a hot climate and need to put an air condition so too high rpm would not be suitaable.

In my opinion the sw10 is a little better than the 286 and phase 3, I dont as yet have direct power comparisons.

Mine idles at about 1000rpm, I dont run it lower than this so as to not create premature wear to the cam, It will probably idle at 850-900rpm but it will no doubt be rougher.

these sort of cams arent very drivable, my engine seems to come 'on cam' at the same point it comes on boost. around 2800rpm (roughly!)

Cheers for all

My engine is 1380 to begin with which is more tolerant to hotter cams. Also, I still have a chamber that resembles a std chamber with beak which I believe promotes better low end grunt.