what fuel punp do i need for turbo 2.6?

[corty240]

What fuel pump do I need for a draw through turbo setup?

[A112H]

The mechanical pump should be fine, if you want to run an electric pump them a low pressure facet pump will be fine. Most carbs don't like anything over 3 or 4 psi.
This is the exact same one I used for my twin carbs, worked perfectly
http://www.ebay.com.au/itm/Fuel-pump-Un ... 2318054cff

[corty240]

If the mechanical one will do the job for now will stick with that until I inject it, no point buyin 2 pumps unless I have to, thanks mate

[Turbo047]

The mechanical pump should be fine. BUT if you want to run more boost the issue is with the needle and seat in the CD175 carbie. I run a 2.6 on 12psi boost and run out of fuel by the time I hit 3rd gear. I just put in a 2.5mm needle and seat so we'll see how that works.

[corty240]

Hey mate, can you please let me know how the new needle and seat go, do you have a stock bottom end? Cheers ted

[geezer101]

There is an old school tuner trick I learned from a carby master down my way. The modders used to take the carby off and drill out the blank on the opposite side of the fuel inlet and then tap threads for both a new fuel barb and a needle and seat in the bowl. Add an auxillary fuel line to it and it will never starve out...The problem with the CD175's is that they will literally dump fuel on a Sigma turbo engine once they've had the boost would up, and it will ultimately lead to continuous lean outs and then the big bang.

[corty240]

Might have to try find a spare carby so I can try that

[geezer101]

Just a bit more info too. The CD 175 on the Sigma turbo already has a bigger fuel needle and jet on it than the model number indicates (the '175' means 1.75mm jetting but the Sigma turbo stromberg carby is kitted with something more like 2.25mm) and the factory fuel pump is up to the job of supplying fuel even with the boost tweaked. The problem is the single fuel needle and seat in the fuel bowl restricts how quickly fuel can be fed into the bowl and this is where starvation becomes the issue. The CD strombergs' design allows them to be run in parallel with fuel flowing from either side of the carby depending on how they are set up. I may take a few pics to show the wheres and hows of tricking up the CD 175 (I'm in the process of rescusitating one but not going to the next stage of multiple fuel lines)

[corty240]

Hey mate how would you feel about rebuilding my carby with the multiple fuel lines if I posted the carb, an overhaul kit and some cash to you?

[geezer101]

My head would hurt lol. By the time postage and insurance to and from awesome Adelaide was added into the deal you would be no better off than getting a local carby workshop to do it for you. Plus the nylon bushes needed to overhaul the butterfly shaft are shipped out from Melbourne and these require the body to have some machine work to install them. I waited a month for the CD 175 I'm rebuilding to come out of the workshop due to the waiting time on the bushes...

[corty240]

Yeah no worries, I am very restricted in the places I can go due to working 6-6 Monday to Saturday, and also no real carb shops around here, might be time to call my mechanic mate see what we can sort out, cheers mate

[Turbo047]

Problems! The book says the Sigma Turbo runs a 2.5 needle and seat. God knows what I've had fitted for the last 20 years.

I've got the biggest needle and seat, yet still run out of fuel by the time I hit 120km. My fuel pump puts out 3psi.

So time to fit a secondary needle and seat. I've measured the thread at 11mm x 1.5.

So I'll fit the other needle and seat and see how we go.

[corty240]

Please let me know how you go, would be interested to see the results. Cheers ted.

[geezer101]

Problems! The book says the Sigma Turbo runs a 2.5 needle and seat. God knows what I've had fitted for the last 20 years.

I've got the biggest needle and seat, yet still run out of fuel by the time I hit 120km. My fuel pump puts out 3psi.

So time to fit a secondary needle and seat. I've measured the thread at 11mm x 1.5.

So I'll fit the other needle and seat and see how we go.

Your problem wasn't a tuning issue or would've leaned out and grenaded many moons ago. The CD stromberg although an alien looking thing to jam on the side of an Astron engine is actually pretty good for turbo charging. It will pull fuel on demand no problems (until there's nothing left in the bowl ) The auxillary fuel line will solve your delivery issue and will open up the illusive top end you've been looking for.

[corty240]

So how would I ask the mechanic to put this is, do you know the technical terms so I don't sound like a fool and the mechanic will actually understand what I mean? Cheers ted

[geezer101]

This requires some drilling to the carby body to install a second fuel line (something I wouldn't hand over to any mechanic) and some special threads cut into it. I've tried to add highlights to my pics to show but photobucket doesn't want to come to the party...

Next to the choke aperture (the thing with the rounded out phillips head screws) is a hole cast into the carby body - this is where the second fuel line is drilled and tapped into.

The hole opposite the existing location for the fuel needle and seat is where the secondary fuel seat is tapped out and installed (it uses the identical type of the original needle and seat on both sides) You can see where the original fuel barb is installed on the left side of the pic - well, it's not the original as some monkey has done a botch job on it and used a Ryco barb...

[ghuphill]

excellent read on this topic,geezer101 ,don't want to get off track but apart from the cd 175 ,are there any other carbs people used to muck around with? a gh turbo i had years ago had a 45dcoe was a pig at times.

[corty240]

That is perfect, I understand completely now and this will definately make it possible to describe to the person I am going to get to do the work. I am going to get either a carby specialist or the mechanic I know who has been the head tafe teacher for years and years, he is a brilliant mechanic and I am yet to see something that he hasn't been able to do . Thanks for your expertise geezer. Cheers ted

[geezer101]

Well, I'm still fiddling with the factory Mikuni Solex downdraft carbies. With a little encouragement and minor modding you can get more midrange, better response and smoother idle without losing fuel economy. IMO the weber is not a winner. I've seen the 45DCOE on a Sigma turbo and the only reason why anyone would do it is they don't understand the CD stromberg or want to say "look, I've got a weber!" They take lots of experience to get the jetting 'right' (and even this is a compromise) and then need thorough tuning to make the most of it. In the meantime you've lost bottom end and fuel economy which is o.k. if you're a lead foot and have a fat wallet.

[InsaneTD]

Could we convince you to share this tips and tricks? I'm getting my carby done soon and wouldn't mind hearing.

[corty240]

Sounds like you could nearly start up a business doing this geezer, let us know, I will be your first customer

[geezer101]

Someone lock this thread? It is rapidly going off topic and I think we've determined what fuel pump you need for a 2.6 turbo. I might at some point do a comprehensive thread on building a Mikuni but I put a lot of work into them. And I usually choose a carby that is absolutely FUBAR to rebuild -

[InsaneTD]

Could always split the Carby talk off into a new thread.

That is one screwed carby.

[corty240]

Starting a new thread, carby mods, great information that alot of people could use, thanks guys

[Turbo047]

Anyway back to Fuel Pumps.

I've checked my fuel pump for pressure output and my Facet pump is lucky to put out 3psi. In other words it takes a while to get too 3psi.

I have a new'ish spare (of unknown origin) that comes up to 3psi quicker. So I'll take it for a spin tomorrow and see how it goes.

I have a Holley Red Pump in a box but have no clue of where to mount it. The booklet states it has to be lower than the tank. So where the hell on a Sigma is lower than the tank?

[corty240]

Just leave it on the ground haha. I have no idea where you could mount it lower than the tank, alternatively you could buy a surge tank, use one of your facet pumps as a lift pump and mount the Holley lower than the surge tank.

[Turbo047]

OK, Update,

Fitted the largest needle and seat, ditched the old 1 - 3 psi Facet pump and replaced it with a 4 - 5.5 Facet pump and it only improved a little.

So no other recourse, I'll be fitting another needle and seat with duel fuel pumps. I'll have to run down my full tank of fuel so I can do some brazing on the tank. But that will give me an excuse to pull the cover off it