Lets talk engines

[Harry_manback]

Ok i need to know the difference between and engine which is cold and one that is warm.

i wanna know what changes in the engine to make it switch from the cold limiter to the normal one?

mines limiting early even when my engine is hot. answers on a postcard........


ta.

 

[al]

6500rpm IIRC wasn't it?

 

[Harry_manback]

thats the hot one. and my light is back on again al.


its sticking in 2nd and 3rd, if i keep my toe in it just splutters past it!

 

[stan*]

Well the limit itself will be preset into the ECU depending on operating parameters such as coolant temp.

In terms of "why"...well, for one, bearing oil clearances need to be fully "settled" in order to allow correct circulation and function of oil on the bearing surfaces. Pistons (and rings) need to get up to a temp where their expansion is settled, and so bore/piston are settled.
Also, oil needs to get up to a specific temp (around 80degC) to function properly.

 

[Harry_manback]

Well the limit itself will be preset into the ECU depending on operating parameters such as coolant temp.

In terms of "why"...well, for one, bearing oil clearances need to be fully "settled" in order to allow correct circulation and function of oil on the bearing surfaces. Pistons (and rings) need to get up to a temp where their expansion is settled, and so bore/piston are settled.
Also, oil needs to get up to a specific temp (around 80degC) to function properly.

yeh, so what changes when its happy?

is there something mechanical that moves about to limit the engine. whats happening when i "bounce the limiter"

 

[stan*]

no its an electronic limiter...its cuts spark at a preset figure.

The ecu senses the engine is up to temp via the feedback its recieving from NTC2 (coolant temp), and changes from the lower limiter to the higher one.

 

[nathanH]

i thought it was to do with oil pressure, limit is droped 500rpm when its cold

 

[rory182]

limit varies across the gears too, 6500 cold and 7250 warm in some gears.

it'll go be engine oil temp as stan says, there's no oil pressure sensor, if there was we'd have a nice wee oil temp gauge most likely.

 

[Harry_manback]

so i need a coolant temp sensor is what what we are saying?

 

[GordonD]

mines limiting early even when my engine is hot.

It takes a surprisingly long time to decide it is warm enough.

I was doing A-B tests on fuel consumption (without then with a modification) on successive 4C (40F) nights. The numbers didn't make sense until I realised I had to throw away the first 15-20 minutes of numbers. The temperature gauge showed it was up to temperature long before that, but that's how long the ECU was taking to decide it was.

 

[Has]

so i need a coolant temp sensor is what what we are saying?

More then likely thsi wud be throwing up wrong readings.

Worth changing at such little cost

 

[16v_jon]

the engine limmiter will raise when the coolant is above a certain ammount and the manifold pressure is above a certain ammount of mBar's
sorry i dont know the exact figure