temps & pressure

[dark_knight]

yes Rev, i concur..
will top up and retry..

 

[AdamB]

@ Adam thanks I was not clear enough here. I was talking about the optimum water temperature of 90deg C that helps the cylinder temp reach auto ignition for proper combustion without encouraging preignition. This assists the cylinder temp before ignition but is is different to the temp at TDC , Temp after ignition and the cylinder exhaust temp..

Pretty much every production car will be regulated there or there abouts 90deg C water temp, although this isn't the optimum temp for engine performance, 90deg C is fine in the cold weather when we want warm heaters. The engine will make more power if we regulate the coolant temperature between 70-80deg C. This is so that instead of wasting heat energy into the cooling system we can use that heat energy to give the crankshaft a bit more of a shove without our engine overheating.

 

[dark_knight]

running a cooler engine

now that we are talking about this, other than a lower-rated thermostat, what other ways can you keep your engine within those low running temps..? of course other than running no thermo at all..
& then once that's achieved, how do you deal with the stock ECU over-fueling..? :/

 

[AdamB]

The car should never be ran without a thermostat, other ways in which you can rum the car at a lower temp would be either to have a larger or more efficient radiator, allowing maximum airflow towards it, or to increase the water pump speed. This can be done by changing the size of the pulley and getting a belt to suit although having the water pump run faster will cost in engine performance. You may not see much of a loss, maybe like 1% loss, never the less it's a loss :haha:

 

[Rev]

Pretty much every production car will be regulated there or there abouts 90deg C water temp, although this isn't the optimum temp for engine performance, 90deg C is fine in the cold weather when we want warm heaters. The engine will make more power if we regulate the coolant temperature between 70-80deg C. This is so that instead of wasting heat energy into the cooling system we can use that heat energy to give the crankshaft a bit more of a shove without our engine overheating.

I see where your coming from but I thought if the coolant is cooler ( ie. a low temp thermastat is used ) the engine block/valves are cooler so their is less heat in the combustion chamber and therfore less power achieved for the same boost.
The desire for less heat in the combustion chamber is to avoid preignition when you turn up the boost up to gain a lot more power and to compensate for the fuels auto ignition temperature that will be lower at higher pressure.
I guess we can assume the 90degs C is ok for stock .9bar boost I am spiking boost at 1.4bar and do not have any issues wiith a FMIC it is worth noting the K1 200v turbo is designed to run 1.3 bar max. on the stock engine setup so maybe above this boost level and 200bhp or equivilant lower temp thermostats should be considered?

 

[AdamB]

True, to deter pre-ignition the incoming air charge needs to be below a specific temperature otherwise it will self ignite in the cylinder, this isn't helped if there is still scavneged exhaust gas left over in the cylinder during the overlap period.

As you rightly said the higher the boost, the more inefficient the air charge is, depending on how good your intercooler is at dissipating the heat you won't have much of a problem with pre-ignition.
I personally would just switch to a lower temp thermostat in the summer to reduce the stress on the cooling system, if it is a daily driver that is. If it's a track car you will probably want to switch to a lower temp stat straight away anyway as your after maximum power and efficiency.

 

[Rev]

.....pre-ignition .... isn't helped if there is still scavneged exhaust gas left over in the cylinder during the overlap period.

Scavenging is an interesting point to consider especially when tuning higher boost. At atmospheric pressure fuel min. ignite is around 260degC while exhaust can be 1000degC . As you sensibly point out timing for scavenging is important to avoid preignition. I would add manifold design has a role to play in aiding scavenging.

I read because water boils at 100C if your engine doesn't get hot enough with a low temp stat you can have a build up of condensation in the engine which is not good for a road car.

 

[dark_knight]

Rev, condensation..? where would this build up..? in the cylinder head/combustion chamber..?

 

[Rev]

Rev, condensation..? where would this build up..? in the cylinder head/combustion chamber..?

It starts in the combustion chamber because water is a by product of petrol combustion - Quoting from the Toyota emissions manual " ideal" combustion produces large amounts of Co2 and H2O ( water vapour ). I believe it gets past the pistons and into the engine parts that way I can't remember the time line and how hot vs cold climate effects this but I do know I also get water from the intact air which has high humidity where I live.

 

[dark_knight]

yes, that much i agree with, but i'm sure at the temps the engine runs at at normal operating temps, this water is not a problem at all as it will steam off quick..

 

[Rev]

Some one may have the full Starlet picture on this but generally it is the PCV system's job to get the condensation out of the oil that is created during startup, there is an issue with short trips as the oil doesn't get hot enough for the water to vaporize nor does it allow the moisture to be burned up through the PCV system. I should know more soon as I have just installed an oil catch can.

 

[dark_knight]

max safe oil pressure

what's the absolute maximum oil pressure that is safe to run on the -fte motor (when still cold or not yet up to optimum operating temp)..? on cold starts, i usually see about 5bar of pressure which then gradually reduces to about 1bar at tick-over (1k rpm) and at about 70 deg C of oil temp. as the oil gets hotter, pressure drops drastically, at times at 90C, i have 0bar at tick-over according to my pressure gauge..! hehe
running 15w-40..
ideas..?

 

[AdamB]

5 bar on idle when cold is about right, although when warm 1 bar is a little low, 1.5 bar would be nice to see at idle.
As the oil temp increases the pressure will decrease due to the oil becoming thinner.
Having 0 bar of pressure at idle would be enough to worry me, maybe you should try a thicker oil seeing as your climate is different to ours, maybe a 15w50?
That might be why your seeing no pressure after a spirited drive at 90degC, are you getting any build up of sludge?

 

[dark_knight]

best i have/can get here is 20w-50.. think i'll try that in the next oil change as i only just flushed with fresh oil.. :/

 

[AdamB]

Don't think that will make any different once the engine is upto temp, it might just make it harder to start running a 20w.

 

[dark_knight]

so then what solution can i seek your majesty..?

 

[AdamB]

Surely one of the traders will be able to ship out some 15w50 oil to you?
If the oil doesn't make any difference then maybe your strainer is blocked, or maybe the oil pressure switch could do with a clean? Those would be the next steps I would look at mate

 

[dark_knight]

oil pressure switch?

oil strainer blocked..? nah.. checked that and cleaned it up real good the last time i was at the bottom end.. please explain how the oil pressure switch (which i presume is the one on the front side of the block) could have anything to do with my low pressures..