Variable off boost fueling

[nominous]

Something I saw on a Rover site which may be relevant to the XUD Bosch (Since Rovers use them too) worth a go for spinning up or just coaling:

mod I've made, which may be interest to Landy owners - remove the vent plug for the lower side of the LDA, get a spare delivery valve, and fit your favoured vacuum hose connection to the end of it. Connect upto an N75 valve, and switch vacuum on and off when you like, to increase off-boost fuelling on the fly. Kinda like a "**** me!" switch, for fast takeoffs

I used a brake nipple, and a length of brake pipe to connect mine up with... because I had it lying around

I dunno if the pugs have this port ... ??

[silverzx]

I don't think they do, no reason why you couldn't add one though.

[nominous]

Doe it not sit in teh same place as the one here with teh black cap on it.
Just next to the words "Stop lever"


Anyone wanna give it a go?

[ginge191]

Pretty sure they do...

[Chris_90]

All bosch pumps have them don't they well turbo ones, but going to all that trouble to drop the lda pin why not just screw the screw in on top so it's permanently pushed in job jobbed

[Piggy]

Take spring out. Done.

Pointless otherwise....why would you wana just dump loads of fuel in when not on boost?!

[Ruan]

Lol, yeah, little pointless, as standard the LDA has so little actual increase of the fuel quantity anyway...

I ended up removing the spring in mine and just rolling without any compensation. It's so out of calibration and mostly jams if you try to do anything decent with it!

[nominous]

See it's interesting to hear things like this.
"so little increase in fuel with the LDA pin"

Really ?

I recall from my astra and now on the corsa, pissing with teh LDS pin and white ring and spring holder brings masses of fuel into the equation.
So much that you can now see it on veg even.
And acceleration is notedly increased.

Adding fuel off boost should bring your turbo in sooner.
Reason for making it switchable = economy.

[Ruan]

The idea of LDA is to REDUCE fuel off boost because of smoke, but it's finely calibrated...

If you left the max screw alone, I reckon you'd make about a 5hp gain by only playing with the LDA... If that in honesty. When you then attempt to wind up the max fuel, you'll realise that the LDA yes has a bigger effect, but most of the time is a hindrance and also has the problem of actually starving the engine of fuel in places it needs it - going back to the calibration...

What sort of things are you considering as "massive" - I mean, I'm talking trying to control ~150+HP of fuel on LDA - it won't happen, you'll be jamming the LDA every time you put your foot on the pedal there'll be that much spring tension from the governor, this is half the reason people moan that XUDs sometimes perform amazingly, but other times just "don't go" because the LDA jams - seen it before now on shimmed governors where someone nails their foot to the carpet and bends the governor cradle from the force placed on it because of the increased spring tension!

LDA is designed to work in a very small range - if you go ahead and start playing with the fulcrum points inside the pump, you could get things vastly better, but most of the time people will realise that they can't mat their foot anyway, since if they do, it's a gigantic cloud of coal... Might as well sack off the jamming problems and just do the whole lot with your foot.

Turning off the LDA for economy just doesn't work like that, you'd end up reducing the fuel quantity and make the engine incapable of utilising the torque provided by the increased fuel quantity at lower RPMs when the turbo works... You'd have to rev harder to get the power... Kinda the same reason why when I fitted my 2052V the economy when not being driven hard was a genuine 58mpg... The turbo is there make the engine more efficient.

[Piggy]

See it's interesting to hear things like this.
"so little increase in fuel with the LDA pin"

Really ?

questions Ruan.....waits for huge 'science bitch' back lash!

[nominous]

Where this was coming from is that on a fairly standard engine, using the LDA to add fuel off boost would see an increase in acceleration, increase combustion, revs and wind the turbo up faster.
I don't really think it applies to VNT's and large out of scope changes.
It's using vacuum to suck the LDA down, off boost, where as on boost the LDA pin would be pushed down to add fuel.

It's a way to get into boost faster and increase off boost power (through fuller combustion of available air) on a fairly stock engine/pump.
Akin to changing the max fuel screw on demand, as you can turn the vac off too.

Now I've messed with the LDA pin on the Mrs corsa by rotation which has changed the slope of the pin and has also affected off boost due to where it's sitting without boost as it's now adding fuel off boost.
I can see how this would be of use without going VNT.

But VNT is infinitely better.

[Piggy]

Just remove the spring and drive it like a XUD god

[toseland]

i have variable off boost fueling..


the more i push down with my right foot, the richer it gets!