Aircooled VW South Africa

Tony Z wrote:you get pressure regulators that have a turbo manifold pressure connection. They will then keep you fuel at 4psi above whatever pressure they see in the manifold

I've got that - from cbperformance. Problem is at low pressure the pump overwhelms the regulator and it can't seem to get the pressure down low enough. It's already on it's lowest setting. I'm now thinking of putting the pump on a variable speed control - change the voltage to control the pump (even as I write that it seems not a good idea) Maybe I must just hunt around until I find a pump that will work. Max pressure 1.5 bar and enough flow.

FI - I'm starting to look at that option, only problem for me is that will change the whole look of the motor - all flat and modern.

Which carb are you using?

why not go to the turbo guys and get a good quality regulator?

The carbs are both the Weber IDF's and the DCD's. With the Facet pump things work perfect - as you said it will. Problem is in future the Facet will be inadequate.

Tony - that pressure regulator is a Malpassi (spelling?) cost me R2500 to get it from CB - I still think if I can get a high flow, low pressure pump things will work out - I'm just not going to buy anything until I can be sure it will work. So far I wasted ~R3000 on pumps/regulators/filters/pipes without any results.

So do you know of any high flow, low pressure pump? max ~24 psi?

24psi.... I'll look

Don't carbs for turbo applications need special "turbo" seals? I know you can make DRLA's turbo spec.
Like with the parts you get here:
http://www.dellorto.co.uk/merchandise/p ... ctionID=53
Some thread about it here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=212871

Looks like you might have to go for a FI fuel pump and step it down.
Even the holley black only goes up to 14psi

[quote="eben"]Don't carbs for turbo applications need special "turbo" seals? I know you can make DRLA's turbo spec.

You can enclose the carbs totally - no seals needed except for the throttle cable or it's possible to install your own seals on the throttle shafts - counter bored and o-rings are installed, then a washer and then when the throttle assembly is tightened the o-rings are sqeezed to seal the shafts. This is not my idea though - comes from STF.

That's only needed if there is a lot of leakage.

Tony - thanks for the trouble. You're 100 % correct - FI pump will work, but not like the ones I tried - capable of 6 bar pressure. Thats too much for the regulator to handle. Even the 3 bar Golf one was too strong. I'll have to find a .... I was going to say a low pressure FI pump, but that doesn't exist.

what might be worth a try.... use a FI fuel pump and get a regulator at the pump which drops the pressure down to 30 or 35psi. Then in the engine bay, stick on your turbo fuel press regulator and set it as you need it. That way, your turbo regulator is seeing a constant 2 to 2.5 bar at all times. I would say 2.5 bar (35psi), that way you got 11 psi purely for flow restrictions and flow velocity losses when at full boost. That should be enough. If the fuel pipe diameter is big enough, then drop it to 30psi going to the regulator.

Why don't you phone Dave Rowley, he already runs/builds turbos?

I found this - how to roughly calculate how much fuel will be required:

D = displacement in cc
RPM = max rpm
VE = volumetric efficiency

Formula : 4.38 x ( D/32.8 ) X ( RPM/1728 ) X ( VE/100 )
This gives you airflow in lb/hr

Then using the Air/Fuel ratio you want, multiply the airflow in lb/hr calculated above with the required AFR. If AFR is 12.5:1 you would multiply by (1/12.5) or 0.08. That should give a rough indication of lb/hr fuel required.

To get to gallons per hour, divide by 7.5 (weight of one gallon of fuel in lb's).

Ref - Four-Stroke performance tuning.

Thought this might be of interest to members.

The best way to sort out the fuel presure when you turbo charge,, is to fit a fuel regulator connected to your boost pipe (I used one from the Uno turbo) As you boost the presure go up in your fuel lines, that way you can insure if you on top boost that your car won't run lean due to boost pushing back the fuel in the lines and when you idle the presure is reduced for a more even petrol control. (Used a golf fuel pump in my days) Must be honest to presurise the carbs is a good idea but a slep when you have to adjust due to strip of the presure box.. In the end I did a suck through turbo (Positive seal installed on the turbo) with a Holley carb when I raced (Find it horrible to drive in normal traffic) and a SU for normal driving.. Lost a few horses with the SU, but you would swear the car was manufactured with the turbo charger,, very smooth.

This is just my 2 sent worth,, had to learn the hard way back then.. there were no Internet for advise

All the best with your project