Re-bore engine to increase power?

[Sunim]

I know I'm right that reboring will theoretically give a greater capacity thus more power. I also know that it's not likely to make much difference in reality.

What I would like to ask you is......
Does the same apply to a fuel injection modern engines with ECU?

I'm thinking that the amount of petrol injected will remain the same so if you increase the bore are you not going to reduce the power effectively because same amount of petrol in a larger chamber, will give less power output?

Please tell me if I got this right or wrong, would you have to fit bigger injectors to increase the power? This would quickly become very complicated.

I'm just wondering because I will probably have to soon re condition my 1.3 engine.

Only a small engine I know. It's a Mitsubishi Colt 1.3 12v (Year 2000) just incase you were wondering.

And I'm not too bothered about increasing power it's just something which I was thinking about.

[thong]

Sunim said:

I know I'm right that reboring will theoretically give a greater capacity thus more power. I also know that it's not likely to make much difference in reality.

What I would like to ask you is......
Does the same apply to a fuel injection modern engines with ECU?

I'm thinking that the amount of petrol injected will remain the same so if you increase the bore are you not going to reduce the power effectively because same amount of petrol in a larger chamber, will give less power output?

Please tell me if I got this right or wrong, would you have to fit bigger injectors to increase the power? This would quickly become very complicated.

I'm just wondering because I will probably have to soon re condition my 1.3 engine.

Only a small engine I know. It's a Mitsubishi Colt 1.3 12v (Year 2000) just incase you were wondering.

And I'm not too bothered about increasing power it's just something which I was thinking about.

wont make any difference at all the amount your going to bore that out to.

[Sunim]

I knew that, but theoretically, was I right? that on an ECU controlled injection modern engine would the petrol amount remain the same and does this mean that power is reduced?

[Mattt]

Technically, the lambda would pick up the difference (i.e. it would lean slightly) and would increase the fuelling.

[Sunim]

Right ok, that makes sense.

btw I had an MOT fail on Lambda 0.82 (allowed limits 0.97 - 1.03)
What does that 0.82 mean?

It also had HC at 550ppm (max 200)
and
CO 6.85% (max 0.3)

I know the car is burning oil so that explains the HC

Can you explain what is causing the 6.85% and what the cause of the low lambda?

[Mattt]

Have you checked the plugs & leads?

[Sunim]

It has a failed piston(s) (compression is low 6 bar which rises if oil put in cylinder other 3 cylinders were 14,15,& 16bar) I get oiled plugs and have had to change them to new every 8 weeks or so.

I should check the compressions again those figs were 2 years ago.

It always passed it's MOT emissions before but not this time. Just wondering what the Lambda means and what causes such a high CO ?

[stevieturbo]

There are obviously some major issues with the engine.. Time for something new.

Edited by stevieturbo on Saturday 3rd February 16:53

[motorwise]

Sunim said:

Right ok, that makes sense.

btw I had an MOT fail on Lambda 0.82 (allowed limits 0.97 - 1.03)
What does that 0.82 mean?

It also had HC at 550ppm (max 200)
and
CO 6.85% (max 0.3)

I know the car is burning oil so that explains the HC

Can you explain what is causing the 6.85% and what the cause of the low lambda?

sounds like your oxygen sensor has given up - have it scanned to confirm

[sunim]

Can you tell me what a low Lambda reading means?
Does it for example mean the engine is running lean or rich? (I heard this somewhere else)
Why does it mean that? i.e. what is lambda?

In my example if low lambda means it is running lean, the ECU compensates by riching up, hence the high HC and CO yes? But because the sensor is broken it never sends the correct signal so the car always runs rich. Is this correct?

Thanks - I bet it was those idiots who made me a custom stainless exhaust!

[Alpineandy]

Doesn't the ecu also know how much air is entering the engine (via the air meter/ hotwire or whatever) and adjust accordingly. So a +5% rebore should mean a +5% airflow and a +5% fuel increase. Or is my understanding wrong (I don't have any injected cars).

[Munter]

Sunim said:

I'm just wondering because I will probably have to soon re condition my 1.3 engine.

Only a small engine I know. It's a Mitsubishi Colt 1.3 12v (Year 2000) just incase you were wondering.

And I'm not too bothered about increasing power it's just something which I was thinking about.

Would it not be cheaper to throw the engine away and replace with a low miliage import engine?

[BadgerBenji]

Time to drop a lump from an EVO in there

[sunim]

I'm happy to put in a replacement engine as long as the price is right. I'm not going to modify the car to a different size engine. These 1.3 engines don't grow on trees. And you have no way of knowing if the replacement is any good, and it could end up costing a lot more.

What would you rather do?
£300 (assuming you can find one for that price (my maximum) on a used engine which then is of questionable quality
or
£500 reconditioning existing engine and you know it is as good as gold.

I know which one makes sense

I got offered a used engine(58K miles) for £920+VAT +£100 deposit on my old engine +£30 delivery +6 months guarantee. Obviously I didn't even consider the offer!

[sunim]

sunim said:

Can you tell me what a low Lambda reading means?
Does it for example mean the engine is running lean or rich? (I heard this somewhere else)
Why does it mean that? i.e. what is lambda?

In my example if low lambda means it is running lean, the ECU compensates by riching up, hence the high HC and CO yes? But because the sensor is broken it never sends the correct signal so the car always runs rich. Is this correct?

Thanks - I bet it was those idiots who made me a custom stainless exhaust!

Does anyone know if this is correct? i.e. does low Lambda mean running lean? Is there a DIY method of measuring a Lambda sensor?

Edited by sunim on Friday 9th February 18:48

[BadgerBenji]

There is usually a quoted resisance for a lambda probe at a certain temperature, obtain this, and measure.

[GreenV8S]

Lambda is a measure of the amount of air going into the engine, as a proportion of the amount needed to exactly burn all the fuel. Lambda 1.0 means it exactly matches the amount of fuel. Lambda less than one means not enough air for the fuel, or put another way too much fuel for the air i.e. rich. Lambda more than one means you have excess air i.e. lean.

When you look at the reading off a lambda sensor you need to understand how the sensor works in order to work out what the reading means. You need to know what the response curve of the lambda sensor is in order to understand whether a low voltage means rich or lean and how much by.

[Mattt]

You say you had an exhaust made up - it could be possible some damage has occured.

[steve_d]

You say the engine is burning large amounts of oil so the likelihood is that at best the sensor is sooted or oil up and at worst FUBAR. The sensor is chemically testing the amount of oxygen in the exhaust gas so does not take kindly to being contaminated. I think I also heard somewhere that high temp silicon sealant on the exhaust manifold gaskets was a no-no.

Steve

[sunim]

Ok then the low lambda would be expected alongside High HC and CO. As high HC and CO indicate rich running - correct?

I just realised something doh! the MOT Lambda reading is not the same as what my sensor is outputting, so my sensor might be outputting a normal Lambda but the engine is really running too rich. Right, now it all makes sense.

Ok, now I have to consider buying a lambda meter.