[missa91] My 309GR 1.3 '86

[jojoe31]

RPM goes up = too much LPG !
RPM doesnt move or just a little = good mixture
RPM goes down = low LPG

[missa91]

In the last 2-3 months I have been noticing higher consumption on my car. As I drive it very rarely on gasoline and almost always on LPG from start to shutdown, gasoline consumption is not very well known, but because of the general bad shape of my carb it is about 13l/100km, which is too much. But LPG consumption was always about 7-8l/100km. I have about 60/40 ratio on my trips, that is 60% open road, rest city.

In April the consumption started getting higher and higher. I just couldn't find the problem. And the solution was found totally by accident. My muffler made a bad sound at higher rpm so I decided to have it checked out.

The mechanic found that the muffler was cracked right at the joint of the horizontal and vertical axis. We fixed that by welding.

Now the consumption is normal. Also, the air filter was changed.
This might be of some help to someone.

[thefunkyboy]

what is a muffler? do you have a pic?

[amilo123]

it's the final part of the exhaust right? How could a crack there affect consumption?

[thefunkyboy]

It is maybe because of the wrong gas circulation between the engine and the outside.

[amilo123]

It is maybe because of the wrong gas circulation between the engine and the outside.

How could that be, exhaust gas goes only out.

[thefunkyboy]

In french,that is called "contrepression". If there is a chnge in the gas pressure,it changes the consumption

[amilo123]

In french,that is called "contrepression". If there is a chnge in the gas pressure,it changes the consumption

I think I understand. But doesn't this mean that there is also more power? Because the gas escapes more freely? Isn't this the reason some people install custom exhausts?

[thefunkyboy]

I am not well experimented in fluid mechanics but i guess that because of air turbulences, the velocity is reduced. It is like the car's CX, if you put something on the roof, then there are more turbulences and then the car needs more energy to compensate.

[amilo123]

I see. I am asking because my manifold is cracked from top to bottom on cylinder 1, I will replace it next week. So should I expect better mileage?

BTW: I am at 12.18 l/100km now (this is before timing and clutch)

[thefunkyboy]

A broken manifold is even worse! On my GT, I got a consumption of 10L without any excess because of a very bad exhaust system, including a broken manifold. (in the same driving condition but with a good exhaust system, the consumption was 8,5L)

[missa91]

I can say that the muffler is a big deal for the 309 1.3. It has not such a powerful engine, therefore any change in the exhaust is bad. It looses valuable horse power and then you have to push the engine harder to make up for the loss. So the consumption is influenced. If the engine is stock, best practice is to put on a stock exhaust or a custom one made specifically for that car.

[missa91]

I am very sorry to inform you of a little accident I had today.
The guy ignored a STOP sign and was on the phone. He hit me while I was moving. The impact was quite strong.

Here are the pictures:

[thefunkyboy]

Damned !

I have wrong hope for your car

What about the insurance?

[missa91]

What is wrong hope?

I didn't call the police because I know the guy that hit me. He will pay for everything on the car, no problems. I already got another door with windows and mechanism. Mine is totally bent.