Engine Rattle

[whitehawk]

Been running on 50/50 veg oil and ulsd for the last 2k or so. Have now noticed the engine a bit rattly on tickover or when labouring. The noise is similar to a big end rattle but there is no sign of it when running normaly. Oil level/pressure is ok. Assuming the tappets are ok (haven`t checked yet) could it possibly be a blocked injector? By the way, it`s a 2LTE engine.


Cheers, Ken

[brian567]

had the same proplem on mine stopped using veggie noise has now gone

[Guest]

It's basically a heavy diesel knock. Problem is that vegoil has slightly different burn characteristics than dino diesel. The knocking is slight pre-ignition - i.e. the micture starts to burn early. The knock is the mixture exploding not quite in the way the engine was designed for it to work. You may reduce this by backing off the timing belt on the pump one notch.

I remember when Topgear did an experiment running WVO in a Diesel Volvo, it sounded like a bag of old nails but ran fine.

Cheers

[Morr]

had the same proplem on mine stopped using veggie noise has now gone

It's basically a heavy diesel knock. Problem is that vegoil has slightly different burn characteristics than dino diesel. The knocking is slight pre-ignition - i.e. the micture starts to burn early. The knock is the mixture exploding not quite in the way the engine was designed for it to work. You may reduce this by backing off the timing belt on the pump one notch.

I remember when Topgear did an experiment running WVO in a Diesel Volvo, it sounded like a bag of old nails but ran fine.

Cheers

I'm surprised and a little dismayed to hear this, from the many experiences I have read about, veggie has a reputation for reducing, not increasing the traditional Diesel Knock.

Clearly however Brian had this problen and now Ken would appear to too, I wonder if Ken stops using the veggie will his knock dissapear also?

I personally have not found any increase in noise (nor however did I experience any great decrease as many others have claimed), I wonder if this is a noise increase that is tending to go unreported, or is there another factor at play here which in these two examples is causing the increased knock in conjunction with the veggie???
Hmmm questions, questions.....

[whitehawk]

Once again - thx for the comments folks. Ain`t this site just GREAT!!
Will probably try not using the vegoil for a while and see if it makes a difference. If it does, i will try knocking back the timing as Andy suggested. I`ll keep you all posted as to what happens.

Cheers, Ken

[Guest]

I'm surprised and a little dismayed to hear this, from the many experiences I have read about, veggie has a reputation for reducing, not increasing the traditional Diesel Knock.

Clearly however Brian had this problen and now Ken would appear to too, I wonder if Ken stops using the veggie will his knock dissapear also?

I personally have not found any increase in noise (nor however did I experience any great decrease as many others have claimed), I wonder if this is a noise increase that is tending to go unreported, or is there another factor at play here which in these two examples is causing the increased knock in conjunction with the veggie???
Hmmm questions, questions.....

To be honest. I think it is more to do with the individual engine and may have a number of causes.

1. How coked up the engine is - severe coking can cause pre ignition due to it retaining too much heat.
2. How old the timing belt is - it coulld be a little stretched - it only takes a little bit to increasing dieseling.
3. Fuel pump settings - Reset the ECU might have a beneficial effect
4. How good the injectors are - if they are weeping a little that will increase knock as well as smoke.
5. How old the engine is, extra wear will make the knock seem worse as the early firing will stress parts of the engine such as the mains and big ends as well as causing severe piston slap if the small ends, pistons or rings are worn.

I think this is why on some engines it will make them quieter and some it will make them better. Vegoil has a different burn characteristic - not better or worse, just different. An old engine, used to using one type of fuel with the ECU having learnt the engine requirements and the wear having been set in, will behave in different ways depending to be honest on how it wants to.

You can get the same effect is you start to use low sulphur diesel on some engines, just as bad fuel will make a difference sometimes.

I guess to get a really sure fire even run on the engine, you should make sure that everything is 100% before you change over - e.g. injectors, fuel filter, new timing belt with timing set 100% accurately, etc etc..

And in fact as long as the basic structure of the engine is good, diesel knock will not hurt a diesel engine in the same way that it will kill a petrol engine pretty quick.

Cheers

[Morr]

Great gen Andy, diesel technology is the one auto area where I find my knowlege lacking, all info gladly soaked up. All you've pointed out makes perfect sense of course, now that its been explained to me



Everyday's a schoolday

[whitehawk]

Just to keep you all up to date - have stopped using the vegoil and things have quietened down again. I`ll try Lucky`s suggestion of changing the timing at a later date but for the time being i`ll stick to just plain ol` diesel. I only do very low mileage at the moment, so the savings are not that great.

Cheers, Ken.

[chunkymonkey]

Have you thought about using a cetane enhancer with the veg oil mix?

Cetane improvers - which boost the fuel 5-9 cetane numbers - will reduce detonation and assist starting - so hopefully eliminating the need to retard the timing.....

You can get this stuff for just over a tenner from goat industries - it has to be worth a go...

http://www.vegetableoildiesel.co.uk/products.html

[whitehawk]

Someone down my local boozer suggested cetane enhancer. Might give it a try.
Ken.