manoj

iTrader: (4)

Hi,
my understanding of Det on a YB - this is caused by Lack of Fuel (blocked injector\electrical failure\incorrect map\faulty pump and so on).. however I could be wrong.

I admit I don't fully understand Det and would be grateful if someone could shed some light on this..
answers in English please.. so that even I could understand it..lol

what is Det..?
what causes Det to occur..?
when does it occur (under what conditions - when on full boost)..?

thanks,
Manoj

Stu @ M Developments

iTrader: (12)

**Taken from another post where i did a small essay:**


Detonation in any engine can be caused by a number of things Phil.

1) Excessive cylinder pressures:
This is created by having the maximum PCP earlier than 10deg ATDC. This is of course why we have an advance curve in teh first place, to keep our PCP around the 10 - 20 DATDC area under all conditions.

2) Excessive heat:
Cylinder head and combustion chamber temps can give rise to detonation and far more damaging "pre ignition" (Pinking as you know it) This is simply due to reaching what is in effect the fuels flashpoint.

3) Wrong or poor fuel:
As above, we want a fuel that burns slowly otherwise we will again exceed the PCP target area and cause massively excessive cylinder pressures that will blow holes in things. (Yes, optimax will burn SLOWER than say, sainsburys crap)

4) Excessive advance:
This again is a PCP issue and the first clue you will have is she will feel probably her fastest ever... then boom

5) lean mixture:
Lean mixtures = hotter burn, again taking us across and back to the heat problem. Lean mixtures also burn and flash faster so taking us to the pre PCP area problem.

6) Excessive EGT.
Often created by a combination of teh above. This will put excessive heat into the exhaust valves with corresponding heat and pre ignition problems as desribed above.

7) Excessively hot/cold ICT.
Hot and cold air has an effect on ICP and also AFR. We need to richen as the air cools and lean off as it gets hot. Failure to do so will make our advance curve WRONG. Beware.

Detonation in an engine is usually very slight. A very slight problem will only usually kill an engine if it occurs for a sustained period. So if we have say, det at 5500rpm (common for YB).
In 1st gear flat out she spends maybe, what? 1/4 second there?
In 3rd gear flat out she spends maybe, what? 1.5 seconds there?
In 5th gear flat out she spends maybe, what? 5 seconds there?... Boom.

Thats all for now Phil... hope it helps somewhat.

GARETH T

well i cant knock (bad pum) that

Stu @ M Developments

iTrader: (12)

Actually i PMSL at that bad pun

RichardPON

... bad joke and bad spelling

GARETH T

the sad thing is im still laughing about it

manoj

iTrader: (4)

thank you Stu. I was hoping that you would reply and that does help my understand it better.
however this may sound thick.. but what is PCP..?

GARETH T

dyslexia can leed to some funny places sometimes,,

GARETH T

peak cylinder pressure

Stu @ M Developments

iTrader: (12)

Each to their own pal, your only thick if you DONT ask questions about things you dont understand. Well, thats my opinion anyway.

PCP = Peak Cylinder Pressure.
This is the point maximum force is exerted upon the pistons crown.

manoj

iTrader: (4)

thanks you Gareth.. that makes sence.

cheers,
Manoj

RichardPON

Richard retreats into the corner...............

manoj

iTrader: (4)

thank you Stu.
tho, i won't stop asking now..lol

cheers,
Manoj

Kev H

I always thought "Pinking" and DET was the same thing? Take it im wrong then

GARETH T

the easyest way to think about it,,,, is too say you dont want any uncotrolled burn, be it, pinking, det, or preignition

Stu @ M Developments

iTrader: (12)

But remembering that "Pre" Ignition is a mixture ignited by something other than the spark plug

DazC

iTrader: (1)

Det is an uncontrolled burn...an explosion instead of a flame front.....

GARETH T

ive read a couple of books now,, and they all say different meanings for every name of uncontrollable burn, (they do agree on what causes it atleast )