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Amount of Fuel needed for cooling

606 views 16 replies 7 participants last post by  MWF 
#1 ·
Following on from my Injector thread, when adding fuel for cooling, how do you know how much to add.

Take for example, when EDS where creating the Phase Chips. I assume they took a standard chip and began to increase the boost and watched the exhaust gas tempterature rise and then increased fuel pressure and injector duty to compentsate.

So, is that the best/only way of doing it or is that an (obvious complex) equation you can follow?

:)
 
#2 ·
they will have closed loop mapped the fuelling using a wideband o2 sensor. no matter the cooling properties, they wont have considered them unless they modded the standard wall wetting maps (which i doubt)
i add 60% for rapid acceleration from 750 up to 1500 revs and have left the injectors firing on overrun to put a little fuel in the cylinders which cools things down.
you dont add fuel to cool, you put in the exact amount to get the best power.
 
#4 ·
not in the fuel map no
which is why people who want to get the best from an engine use fully mappable ecus and not 'altered main fuel map and timing' chips which lets be honest, are crap 90% of the time.
heres a pic of how many fuel map types i have...i couldnt fit them all on the screen so most is hidden tbh, but the headers are there


 
#7 ·
Oh no I get that. My question is, how do you know how much?

Now you said they use a Wide Range Lambda sensor which makes sence but what is determined as the optermum value? Ie, at how do you know when the engine has reached the right point between cooling and power?
 
#8 ·
there is no right point for both tho cem
the right point gives max power...its up to you to keep temps sane
if you wanna add more fuel fine, but it will then go past the optimal power point
i know how much i add, but its only for full throttle (and overrun) @ lower revs, the top end is mapped for power and power alone

bigger intercooler/NOS/water injection are the options available to you, not more petrol (assuming you are getting enough to give you peak power AFR)
 
#10 ·
i just read a thing on this in ccc, dave walker did a bit on turbo management, he says

'With a turbo making serious power you have little choice but to use some of the fuel as a coolant. you may need to run a mixture ratio of about 13.3 to 1 in order to make maximum power, but if the engine is going to live it might want to be nearer to 11.9 to 1. The extra fuel cools things down to just the right side of detonation. The way to monitor this is to fit a probe in the exhaust, measuring gas temp - as audi does with its v6 bi turbo. if the exhaust gets too hot the system adds more fuel before backing off the boost'

dunno if that helps?
 
#11 ·
Yes but isn't the object to add fuel until you reach the 'safe point'. The point where the engine will no longer melt a piston when you put your foot down.

I'm asking how you find that point? If you don't put in enough fuel then the engine will melt, which is hardly a great way of testing. If you put in too much then you may not realise that you could make more power from the engine.

In short - How do you find the minimum amount of extra fuel needed to keep the engine safe? I know I don't have a mappable ECU, for the point of the question assume I have.
 
#12 ·
region17rc said:
i just read a thing on this in ccc, dave walker did a bit on turbo management, he says

'With a turbo making serious power you have little choice but to use some of the fuel as a coolant. you may need to run a mixture ratio of about 13.3 to 1 in order to make maximum power, but if the engine is going to live it might want to be nearer to 11.9 to 1. The extra fuel cools things down to just the right side of detonation. The way to monitor this is to fit a probe in the exhaust, measuring gas temp - as audi does with its v6 bi turbo. if the exhaust gets too hot the system adds more fuel before backing off the boost'

dunno if that helps?
Thats it thanks :)
 
#13 ·
same way you measure any fuelling - lambda sensor!!!
you will need a wide band setup with display tho if you are gonna start mapping fuelling on full throttle in a turbo tho IMO
i can more or less get away with the standard sensor cos detonation isnt a problem (he says lol)
 
#16 ·
Cemesis said:
Following on from my Injector thread, when adding fuel for cooling, how do you know how much to add.

....So, is that the best/only way of doing it or is that an (obvious complex) equation you can follow?

:)
You can go as rich as 10:1 under boost if you're running stock CR, high boost and inadequate intercooling. The bores will be fine, how often do you sustain full throttle?
check out my website:beer:
 
#17 ·
Usually the fuel is added as part of the transient fuel mapping, so as you shut the power off it adds a little fuel to absorb some of the heat within the combustion chamber. Hence why some chipped turbocharged cars flame on the overun and as you change gear.

How much you add during load is always going to be a weigh up against overall engine power. If the exhaust gas temps are getting high and adding fuel is going beyond stoich you need to look at cooling your engine better with something like a bigger intercooler or decent charge cooler. Water injection and nitrous are options but of course can run out at inconvienent times.
 
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