i just did a theory test for the fun of it (yes im bored) one of the questions was where does the injector inject the fuel?
the answer the test wanted was 3 combustion chamber.
if this is correct how come the tips of the injectors dont get burnt up and is there no inlet manifold as such
Yes that is correct, They are made of steel so can withstand the heat, they fit in the cylinder head held in by clamps / bolts, I was involved in recondition injectors and fuel pumps a few years ago? many years ago lol
Combustion chamber aka pistons where the bang happens where the fuel and air are supplied and compressed to go bang.
You have inlet and outlet manifolds on every engine, inlet for air and outlet for exhaust gasses.
Crankcase is the engine block basically.
Diesels never to my knowledge have never had carburetors so that option is a rather stupid option to have put in the questionnaire on the first place.
a lot of the answers are silly… there is usually 2 stupid answers 1 maybe and 1 with a bit of common can be guessed at thats the theory test for you
Diesel is generally direct injection which means the injector injects into the cylinder combustion chamber.
Petrol can be either indirect into the inlet manifold or direct into the cylinder combustion chamber.The latter being a more recent development which is creating a lot of problems.
It’s a bs question obviously made up by those who haven’t got a clue how an engine works.
Ha ha ha bloody ha. Carryfast talking about others talking ■■■■■■■■. Couldn’t make it up!
I do know what you mean, but on this occasion, he seems mostly correct.
His explanation of where fuel injectors are found is right.
The question, as presented here, doesn’t specify petrol, diesel, or jet engines. Being a truck forum and we are told the question is from “a theory test” we are assuming it is a truck diesel.
The question as presented is poor. CF correct again. 
the question was as written but i guess i should of pointed out that it was a lorry theory test
Yeah, I think we all were assuming that.
Diesel injectors do live in the combustion chamber, as do valves and the pistons and spark plugs in petrol engines. Clearly they are made of materials designed to cope with the temperatures and pressures found there.
They will not be common or garden mild steel, but will likely contain chrome, molybdenum, or whatever to cope with the harsh environment. Apart from the problems of combustion the jet itself will be subject to wear from the vey high fuel pressures used in modern common-rail engines.
New designs are dependent on materials technology as much as electronics.
i relaise a spark plug is in the combustion chamber or rather the tip is. however you replace those every 20,000 miles as they are about 10 quid each and replaced every two years or so not too bad. God knows how much an injector for a lorry would be but i suspect many times 10 quid and replacing them every 2 - 3 months would get a tad expensive.was my thinking. plus i have never worked on lorries only diesel cars with indirect injection.
However, after getting the above replies i went and looked it up and from what i can see the diesel is injected into a pre chamber where only a small amount of combustion takes place so the wear done by high temperature and pressure would be minimised
According to adverts online, expect to pay at least £3k for a set of six diesel injectors
As Franglais said, they will be made of suitable materials to withstand their job, but that kind of technical info doesn’t pop straight up on web searches these days (“Come back Web 1.0, we miss you…”)
Your quiz could have had better questions, such as: “What property of flammable liquids allows the diesel ICE to operate without spark plugs?” The answer to that you will have covered on your ADR course.
lower auto ignition temp?
as i said above its the theory test for becoming an lgv driver however i vaguely remember a question about coming across an accident or something and the tanker had a blue diamond sticker with a 4 on it what is it carrying?
I remember thinking at the time that it was a bit of a specialist question for someone that hadnt even driven a lorry
Seems the last BMW indirect injection diesel was the 2.5l M51 which was discontinued in 2000.
CRDi, TDDi, and similar use the “D” for Direct injection. Check labels on Ford, Peugeot Mitsu etc No swirl chambers.
The higher pressures possible with electronic injection means that diesel fuel can be injected in more precise quantities and more precisely timed.
The inherent inefficiencies of using swirl chambers are avoided in these engines.
There are issues involved in spraying the fuel directly into the combustion chamber, rarely is any new thing without downs as well as ups.
Here is a very pretty YT of a Volvo truck engine.
Auto ignition temperature, spot on. The high compression ratios of diesel engines produces friction which allows the fuel vapour to auto-ignite, hence not needing the spark plugs as petrol engines do.
A blue placard can only be referring to Class 4.3 Dangeous When Wet, and would indeed be far too specialist for a learner driver.
IIRC back in the day there were two main injector nozzle designs, Pintax & Pinteau I think
Sorry I meant in general. Franglais.