Converting open loop to closed

[skattrd]

Ok, I'm thinking about a mini upgrade on the Alfa's rather basic single point system. How difficult/easy is it and any recommendation for what to use?

I was thinking VP-100 from Tinley, http://www.tinleytech.co.uk/acatalog/Sy ... rades.html Second one down on the page £121.44+VAT
Simple diy job or am I missing something?

Any Advice appreciated

[rossko]

Depends on your exhaust removal and welding skills really

What returns are you expecting? Advantages of closed- over open-loop are fairly small if the existing system is properly set up. If it's not properly set up it wouldn't help at all, the basics still have to work right.

[skattrd]

Exhaust removal and welding (for the boss I assume) should be ok, I have a fiend who can do that.

As for returns, the main reason I was thinking about it was for hopefully slightly more fuel/power when needed. I think the current system has been set to run too lean as the car is now having a new head gasket fitted. I'll be checking the mixture once the engines back together.
What I was hoping was that this could adjust the mixture when needed and hopefully save me worrying about blowing another head gasket.

If I do leave the system as it is how often should I check the set up and mixture? I'm doing about 1000 miles a week at the moment.

[tommo2009]

Changing to a closed loop system will have no fuel or power advantages.
The LPG in itself was not to blame for your headgasket, the fact that it was not setup properly may have led to that issue.

As Rossko says, a correctly setup open loop system will run just as well as a closed loop system (and less to go wrong)

[skattrd]

Ok, thanks for the input. It looks like I was misinformed, I was led to believe that closed loop would be more economical/power efficient, adjusting the mixture automatically ... I'll have to try and set the mixture properly ... I'll be back for advice on that when I find out what the system is

[Gilbertd]

Have a look at Simon's page (http://www.diy-lpg.co.uk/articles/files ... -loop.html) for setting up instructions for an open loop system. While I agree with both of the professionals that a properly set up open loop will be just as good as a closed loop system, I would still fit a closed loop controller. An open loop system will go out of tune due to something as simple as the air filter starting to clog up but a closed loop would correct for that. If the system has been on the car for some time, the vaporiser will be starting to age so again will drift out of tune and a closed loop system will correct for that too.

However, when it reaches the stage where it is way out, then the closed loop will not be able to cope so the fault will show up suddenly rather than gradually. As has also been said, you are adding more things that can go wrong too (I've just had to replace the stepper on my P38 as it was starting to stick occasionally). In saying that, the diagnostic capabilities of the AEB Leo, Bigas Pegaso, etc, make it easier to see what the fault is. Whether the VP-100 has the same capabilities though I don't know.

[rossko]

If you want to do it, do it. A closed loop system will always be more accurate.
"more accurate" is relative, if the old system is 98% right then even 100% isn't going to make perceptible differences.

If you are doing to go faster, forget it ; you still have the same old mixer stuck in the engines throat.

If you are doing to save £££s, do your sums. Let's say its 2% more economical (random guess) how long would it take to pay back the extra investment.

If you are doing it to make less emissions, that is a very good reason. Here the last half-percent of accuracy is vitally important, and its why closed loop was invented at all.