legacy twin turbo....the story so far

[jimmypatch]

Still not finished it yet. Just don't get the time or weather.
Things left to do:
1. Exhaust clamps
2. locate header tank.
3. Fix/setup gear linkage.
4. relocate battery to behind rear seat and extend all pos + wires.
5. Connect up fuel pump properly and not just with spare water hose as it is now!!!

[jimmypatch]

Well would you beleave it I,ve finally finished the thing!!!!!
In the last two days I just about got round and finished all the final jobs.
Header tank is fitted
custom exhaust is all fitted and hanging correct (it comes out by the front left wheel)
Gear linkage was emotional but it now works.
All the wireing is in perminant.
Fuel hose is in. it comes from the tank as 8mm and is then stepped up to 12mm and then stepped up again to 16mm. Because the inlet to my massive fuel pump is 16mm.
It runs and goes into gear. Job done,.

[toomanytoys]

Wont running that "massive" fuel pump with a very restricted inlet cause some issues? cavitation at least.. poss heating up of the fuel.. enough flow for the injection?

[silverbullet]

Wont running that "massive" fuel pump with a very restricted inlet cause some issues? cavitation at least.. poss heating up of the fuel.. enough flow for the injection?

Hmm. Unless he's unwittingly swaged it into a perfect venturi...
The engineers in the room say: 8mm bore up to 16mm means a nominal 50sq.mm up to 200 sq.mm not ideal.

[jimmypatch]

well theory and maths are good but this thing does actually run and drive and from the smell of the exhaust it runs rich so its getting enough fuel.
what is cavitation??

[jimmypatch]

Also the pump is able to hold 600 BHP. and im "only" running 250-280. so the big inlet gives it the ability to run 600. but im only using it on less than half of it's capacity.
I only drove the van around the block as its not fully finished but its very very quick

[silverbullet]

Cavitation is when you cause such a large pressure drop in a fluid that gas bubbles start to form, like having a high-volume flow pump running with a restricted inlet... When the bubbles collapse (at supersonic speeds btw) they cause erosion damage to the pump impeller caused by the shockwaves. It's a serious business in the pump/marine impellor business.
Your fuel outlet from the tank, gradually increasing in size toward the pump, is the sort of thing to avoid at all costs.
In less extreme cases, you just aerate the fluid and heat it up. Not what you want in a fuel delivery system! 2wd T3's don't help themselves by having such a shallow fuel tank, so there's no pressure head to feed the pump either.
Glad you're up and running though. Sterling effort

[jimmypatch]

I did notice some bubbles in the fuel filter that is a pre filter to the pump. the filter has a 8mm inlet and outlet. are these the bubbles your talking about?

[jimmypatch]

would running a pre pump help?

[silverbullet]

would running a pre pump help?

If you're running a monster of an injection pump good for 600 bhp, it needs an unrestricted inlet right from the pick-up inside the tank.
Having a low pressure, high volume pre-pump, feeding a swirl pot that then overspills back to the tank would be a better way to get good "clean" fuel delivery. but this primary pump needs to be able to keep up with the injection pump at full chat...
The arrangement for efi always goes: tank, pump, filter, fuel rail. Never filter the pump inlet, always the outlet. There's so little pressure head available to feed the pump (as I said before) that the % restriction caused by the filter will drop the available head to next to nothing (maybe where your bubbles are coming from - that's cavitation you're seeing)
The pump is designed to deliver excess volume/pressure all the time, so this % drop across the filter doesn't matter (that's why the fuel rail has a regulator) as it's already putting out more than enough.
Looking at it another way: the standard bosch inj pump will safely deliver enough fuel for a 300bhp Jaguar V12 (it's the same pump) and when driven hard, a 5.3 H.E. returns about 4 mpg. They all had a gravity-fed swirl pot to prevent fuel surge on hard cornering. The tank outlet / pot feed have nominal 12mm hose connections, just like a DJ, MV or the SA buses.
I've got a good Jag swirl pot knocking about the shed somewhere. But it would still need to be pumped as it has to live below the base of the tank. Not possible on a 2wd T3.
So, either fit all this plumbing and hope that it works out OR get the tank modified with a large bore pickup.
Personally, I'd go this route and if looking to go for more power later, with a fuel pickup of big enough cross-sectional area to feed two bosch pumps and run them in parallel. About 16mm diameter would do it, funnily enough.
Standard parts make life easy in the long run: simple, elegant and lighter.

[jp77]

ah, i see what is being said here, this makes perfect sense now. i can knock up a 16mm inlet for the tank, ill nip out and take a look now!

[jimmypatch]

ok cheers.
I think i'll ditch the pre filter for starters and maybe just sack the big pump and buy one with an 8mm inlet and outlet

[jp77]

think i can rig it some how, if all it needs is a 16mm pick up and inlet. Thats not to hard

[jp77]

any news on charging problem?

[silverbullet]

ok cheers.
I think i'll ditch the pre filter for starters and maybe just sack the big pump and buy one with an 8mm inlet and outlet

You prob. won't find one with an 8mm pump feed. The pump will need a bigger inlet than outlet. A std DJ type will have a nominal 12mm in, 8mm out (which means special VW spec 11mm hose and 7mm to the fuel filter)
Bite the bullet, sort the tank pickup and the rest of it will be easy...ish. Less aggro in the long run.