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Posted: Sun Sep 14, 2008 4:52 pm
by fuzzy
Hi All,
I have had my mini converted 7 months ago, can any one advise me on how many drips per minute of flashlube some one told me that the bottle in the engine should last around 1000 miles ? its running great

Re: Flashlube

Posted: Mon Sep 15, 2008 6:46 pm
by runningoldcars
I drip every 6 seconds in the sight glass with the engine running at idle.

The manifold vacuum is highest at idle so the drip will slow down as you run the car, and deliver the right amount for the air/fuel passing into the engine.

Re: Flashlube

Posted: Mon Sep 15, 2008 8:09 pm
by topbanana0
had my car converted and im worried that i dont know what the hell your talking about, fill me in :shock:

Re: Flashlube

Posted: Tue Sep 16, 2008 11:07 pm
by runningoldcars
The flashlube kit (that i'm familiar with) is a bottle of a chemical that replaces the additives in modern petrol that themselves replaced the tetra-ethyl lead that used to be in petrol. This lead compound was used to prevent the valve seat wearing and primarily as an anti-knock solution as it increases the research octane number (RON).

LPG has a high RON but dosn't have this seat coating property, so we need this additive to prevent the valve seats wearing. Without it we will gradually erode the engines valve seats, valves, tappets, rockers and camlobes (eventually). This will cause you to cry.

Now the actual answer:

The mechanism for getting the additive to the valves is via the inlet manifold. A hose is taken from the bottle to the manifold and if done properly should be on the rear of the manifold between cylinders 2 and 3 (assuming a 4 cylinder engine) to try to ensure a reasonable distribution into all cylinders. The delivery of the fluid is driven by the manifold vacuum; when the cylinders are going down they suck in air/fuel and this causes a vacuum condition in the manifold.

The hose in the bottle is at the bottom and the free surface of the fluid (the top of the bottle) is at atmospheric pressure, thus with vacuum (sub-atmospheric) conditions in the hose and atmospheric pressure on the fluid the fluid flows down the hose, and ultimately into the manifold.

When the throttle plate is shut the engine is labouring to get air and the vacuum effect is amplified, going as high as it will get in running conditions. Thus with the vacuum at it's highest (or lowest!) the fluid flow can be set at a reference value that allows the highest majority of cars* to be set with the simple correlation of 1 drip of fluid every 6 seconds in the bottle's sight glass.

As the throttle plate is opened the engine revs up and goes under load, and then the vacuum will decrease and the flow of fluid will decrease.
Thus the longer you idle the engine, the more valve saver you burn! So switch off when you're stopped.

There is more that can be said about fluid entrainment in the air flow in the manifold, big bore engines, big valve engines, multi-bank (v) engines and of course pressure charged engines who's manifolds go into positive pressure when on boost, but for most 4 cylinder engines being driven by normal people the above is true.

Re: Flashlube

Posted: Thu Sep 18, 2008 11:10 am
by topbanana0
dont think i got one of those? should i get one, can i fit it myself? is it expensive?

Re: Flashlube

Posted: Thu Sep 18, 2008 9:55 pm
by runningoldcars
In order of question marks:

I don't know if you have one either.

If your engine has a soft alloy head or soft valve seats then yes you should.

If you can work an electric drill and a tap (of tap and die set fame, Aldi £14.99 for an okay one), then yes.

They can be found for £45 + £3p&p on the well known online auction sites.

Now some pre-emptive answers:

I do not know for sure if 1.2 Clios have soft heads. Assuming it is a 16 valve not related to the old 8 valve engine in early Clios then it may well be soft.

You will be drilling and tapping the manifold to add a little (supplied) nipple onto which the tube form the bottle will be attached.

Re: Flashlube

Posted: Thu Sep 18, 2008 10:59 pm
by mak-uk
Personally, I think your installer should have sorted you out and included it in the price if you need one.

Re: Flashlube

Posted: Fri Sep 19, 2008 4:53 pm
by topbanana0
I don’t need one, spoke to a guy I work with, he has gas conversion experience and it a Renault mechanic.
He said if it runs on unleaded it will be ok. :D

Re: Flashlube

Posted: Sun Sep 21, 2008 9:10 pm
by runningoldcars
The ability to run on unleaded petrol is not the issue.
Softness of valve seat material and its interaction with the air/fuel mixture, combustion mixture and blowdown mixture is the issue.
Oxides from these mixtures form on the seats that can* have a protective effect even in modern unleaded vehicles. So you can still have seats that are softer on some vehicles than others (Hondas are an example).
If the tappets are set correctly on these engines and factory cams are used that have controlled levels of acceleration upon closing to prevent the valves slamming shut then all will be well and the impact welding effect with a soft seat is not a problem.

But put in a different chemical (lpg) and you've added a new variable to the mix that was not in the factory design spec. LPG does not have the same lubricating quality as petrol (leaded or unleaded) either so you then may have an engine that ran fine on petrol, but chemical or tribological compatibility becomes an issue with LPG.

Please believe that i'm not ranting against your man. If he has lpg experience with these engines and says it's fine then i'm sure he's right, but I felt compelled to reply to this just in case some poor soul read "He said if it runs on unleaded it will be ok." and took it as an all-encompassing gospel. That's how we break engines.

*Some seats are just hard and that's that, so don't get anything from the coating.

Re: Flashlube

Posted: Mon Sep 22, 2008 10:49 am
by mak-uk
Some very good points raised.

Ford have released several 'factory fit' LPG conversions. However, on these vehicles they installed hardened/uprated valve seats and / or valves. Whereas, 'regular' Fords need Flashlube.

I was always under the impression that Japanese, 'British' (Ford/Vauxhall) and French cars required Flashlube :?: