LPG Discussion Forum

Thanks again for the info

I think you have got the gist of the term 'throttle body' but if you think of the air intake system as a simple tube between the engine and the inlet pipe behind the radiator grill - when the engine turns, the pistons suck air in from the outside of the car. If you were to hold a lit cigarette near the intake, smoke would be drawn in from quite some distance - that's because the air just inside the intake is at a much lower pressure than atmospheric, as it is throughout the whole length of the tube.

Whilst the air is moving through the tube, through the filter, the MAF, throttle body and manifold, there will be a vacuum of varying strength (depending on the diameter of the tube at a given point), but enough to draw the lightweight FlashLube fluid up a tube and into the airflow.

At no time when the engine is running, is there any atmospheric pressure within the entire length of air intake system!

It is important not to get the fluid onto the thin-film MAF's because this will destroy them - but it won't do any harm to get some on the throttle valve - the fluid isn't going to stick to anything and cause it to jam!

All but a few molecules will get sucked straight past it at 300mph, not even touching the sides!

As soon as the engine stops, the pressure inside the whole of the air intake system returns to atmospheric pressure, and any FlashLube fluid near the air intake will run back into the bottle - which again, is why you drill underneath the air intake (i.e. upwards) and position the bottle lower down.

Taught2BeCautious wrote:I think you have got the gist of the term 'throttle body' but if you think of the air intake system as a simple tube between the engine and the inlet pipe behind the radiator grill - when the engine turns, the pistons suck air in from the outside of the car. If you were to hold a lit cigarette near the intake, smoke would be drawn in from quite some distance - that's because the air just inside the intake is at a much lower pressure than atmospheric, as it is throughout the whole length of the tube.

Whilst the air is moving through the tube, through the filter, the MAF, throttle body and manifold, there will be a vacuum of varying strength (depending on the diameter of the tube at a given point), but enough to draw the lightweight FlashLube fluid up a tube and into the airflow.

At no time when the engine is running, is there any atmospheric pressure within the entire length of air intake system!

It is important not to get the fluid onto the thin-film MAF's because this will destroy them - but it won't do any harm to get some on the throttle valve - the fluid isn't going to stick to anything and cause it to jam!

All but a few molecules will get sucked straight past it at 300mph, not even touching the sides!

As soon as the engine stops, the pressure inside the whole of the air intake system returns to atmospheric pressure, and any FlashLube fluid near the air intake will run back into the bottle - which again, is why you drill underneath the air intake (i.e. upwards) and position the bottle lower down.

ok you know a little bit... but completely missing the fact that the throttle body regulates the speed of the air flow and therefore the rev's along with the amount of fuel injected.

You also want the valve lube to be atomised in the air flow, having it hit anything will cause it to turn in to drips and therefore too much of a build up could cause a "diesel" effect where there is too much liquid for the piston to compress and therefore the engine stops dead - not very likely but in a rare case could.

And the fact that after the throttle body at idle there is quite a high vacuum pressure then before it, putting a vacuum feed lube kit before the throttle body will give virtually no feed.

Fact is, using a vacuum system in this would be stupid, the cost of a rebuild on the valves should VSR happen far outweighs saving a few quid between vac and electronic kits. If this was my car, i wouldn't even consider a vacuum kit, it would be a proper electronic as there is no way i would want to take a risk.

Some people think it's good to give advice knowing that it's not there problem should it go wrong...

As Ross has said, and i did, good even lube to ALL cylinders is required, and getting right is an art.

Buy cheap buy twice, or in this case, buy cheap get it wrong and spend thousands putting it right....

sijones wrote: You also want the valve lube to be atomised in the air flow, having it hit anything will cause it to turn in to drips and therefore too much of a build up could cause a "diesel" effect where there is too much liquid for the piston to compress and therefore the engine stops dead - not very likely but in a rare case could.

You are quite right - I hadn't considered that! Those drips from a 300ml bottle could easily build-up on the 'whacking great plate' thingumy and completely jam a 4.5 litre V8 engine.

Best fit a proper electronic kit then.

throttle bodys dont do so well with oil over them. if you have a oil breather before the tb like i do then you have to scrub it out every few thousand miles. the oil coats the tb and the @!## that gets past the filter sticks to it
my cars currently running like @!## and %99 its down to this

Taught2BeCautious wrote:because the air just inside the intake is at a much lower pressure

Have you measured this? Not much lower, just a teensy tiny millibar. Flashlube type kits are designed to work with hundreds of millibars, as found downstream of the throttle.

Taught2BeCautious wrote:but enough to draw the lightweight FlashLube fluid up a tube and into the airflow.

I would say it's time for a new airfilter there, though we musn't discount venturi effect helping it along

The maker's instructions are pretty explicit about all this
http://www.flashlube.com/images/stories ... ochure.pdf
http://www.jlm-baltics.com/galery/_jlmb ... manual.pdf

Taught2BeCautious wrote:All but a few molecules will get sucked straight past it at 300mph, not even touching the sides!

But first they'd have to get picked by the slower-moving air in the big air intake.

Taught2BeCautious wrote:why you drill underneath the air intake (i.e. upwards)

For what it's worth, I do the exact opposite. Being quirky I go downstream of the throttle, as close as practical without fouling the butterfly. Then go in from the top (if there is one), imagining that gravity will help the drops to fall through the airflow and encourage atomisation, where it's turbulent behind the butterfly.
I can see most of the in-below-the-intake just bubbling up into a puddle.

But in the end yes, I would agree the simple systems aren't the best choice for this engine layout.

rossko wrote: But in the end yes, I would agree the simple systems aren't the best choice for this engine layout.

What do you mean by this? As even the Electronic kits ive seen still rely on engine vacuum, they just are 'dripped' by an electronic timing setting, rather than a mecanical dial.

Thanks - ps - this discussion is now way over my head, but very interesting.

Electronic ones have a pump to them to make sure they deliver the right dose, the problem with vacuum one's is they don't deliver maximum lube when full throttle which is when you want it, they deliver maximum at idle.

The electronic one will also save you some money in a way that they deliver the right dose over the rev range and therefore don't use up lube quicker.

From personal experience I have also had to constantly readjust a vacuum lube as it would randomly stop or not give enough then be too much and empty a bottle of lube quickly, if i do need to use one again i'll spend the money on an electronic one.

gerlewis wrote:even the Electronic kits ive seen still rely on engine vacuum, they just are 'dripped' by an electronic timing setting, rather than a mecanical dial.

I can't comment on how e.g. the JLM one works, but am familiar with the Flashlube version. What looks like an injector is really a single-stroke pump, it really does pump the lube and so works well with turbos (which doesn't interest you). The pump drive is derived from fuel injection drive, so is properly proportional to fuelling/load. And as a bonus only delivers when actually running LPG.

The basic electronic kits are better at lube delivery but as it still arrives at a single point, no better at even distribution to cylinders, which will rely on the installers canniness.

The next step up is multi-point distribution, as with Prins or BRC systems, or the adaptors available for the Flashlube style.

Some of the Electronic kits on the market, take a signal from one of the gas injectors to calculate how much fluid to deliver. You have to adjust a variable resistor to determine exactly how much fluid is delivered for each pulse, and due to the nature of the electonic components used, you also need to compensate for changes in ambient temperature.

JLM, FlashLube supply these kits for between £150 and £200.

The only advantages over the simple vacuum-operated systems, is that they don't deliver fluid when you are running on petrol, and that they warn you when the fluid tank is running low.

Others, like the JLM system in the link above, and the updated FlashLube kit, only have a simple float switch and LED that only tells you when the level is running low.

These kits sell for between £60 and £120, whereas the simple vacuum-operated kits sell for between £13.50 (eBay) and £50. Fluid varies between £7.99 and £20 per litre.

Whichever system you use, you will of course have to make adjustments to compensate for the viscosity of the fluid in summer and winter, and I don't think any of the electronic kits do that.

Perhaps I'm being a bit old-fashioned in this respect, but I think simple is best here - less to go wrong, and no unnecessary wiring, labour, gimicry and expense.

I have always gone for the 'drill up and hang low' method so that when the engine stops, all of the fluid in the system runs back into the bottle. I have always fitted the outlet between the TB and the engine - apart from the first one I fitted, to a Citroen BX (because I made a mistake), but it still worked and the car went on to do over 130,000 miles without problem.

If positioning a single outlet is a challenge, you can get a 'manifold' add-on (see this page), so you can place one closer to each cylinder - which I would seriously consider.

I think we all agree that fitting a FlashLube system of some sort is a good idea, but now that you know a bit of what is available, and how the prices vary, I think its time for you go get an opinion from someone who has the skill and experience to advise what would be the best one for your particular make and model of car and LPG kit.

Alan.

Seriously? 2 pages for a flash lube system that costs £100. For someone who can afford to own a 4.5 V8 Porsche?

Taught2BeCautious wrote:Whichever system you use, you will of course have to make adjustments to compensate for the viscosity of the fluid in summer and winter, and I don't think any of the electronic kits do that.

Dat's what the pump is for, it delivers by volume regardless of viscosity.

The primary advantage of the electronic systems is that lube delivery is directly proportional to fuel input, the harder you cane it the more lube goes in - the simple vacuum systems dollop in most at low demands, and least at full power, hoping that's enough to cover it.

Thanks for all the info, I've had an education!

Taught2BeCautious wrote:If the Vacuum line to the LPG system's MAP sensor has been fitted correctly, it will be in the right place to feed the FlashLube into - there's nothing wrong with teeing into it - and no point drilling another hole next to it either!

The Flashlube should ALWAYS be fitted with its OWN dedicated nozzle and NEVER T'd into any existing vaccum line. T'ing into the MAP sensor line is a geat way to kill a MAP sensor as teh diaphram acts like a pump and ends up filling the sensors with oil!