How Much?
10-02-2004, 10:34 PM
#1
How Much?
how much power should i be expectin from my car? its gotta RS500 intercooler, full stainless exhaust, K&N induction kit, -31 actuator, samco hoses, standard chip and now 12psi of boost. what kinda power figure should i be expectin from my current spec?
dave
dave
11-02-2004, 08:39 AM
#3
Testing the future
Only standard power on a standard chip - simple as. Why? Not so simple.
The mods that you have will not make any difference to the maximum power. The max. power will only be increased if you get more air (and the right amount of fuel to go with it) into the engine.
This is typically done on a normally aspirated engine (i.e. non turbo) by increasing it's volumetric efficiency, commonly known as making it breath better. That means basically that you make it easier for the engine to suck in the air and blow it out again by porting (enlarging the holes that the air goes in and out of) the cylinder head and the manifolds.
Another way of getting more power, is to increase the maximum speed of the engine, i.e. increase the rev limit. This can cause problems if the bottom end (crankshaft, con rods and pistons) are not up to the job. By increasing the speed, you're also increasing the amount of air going into the engine (in the same time), so you get more power, but only if the engine can flow that much air. Typically, factory rev limits are set with the peak power and reliability in mind.
These breathing mods can also be done on a turbo engine and will bring benefits, for example, by fitting a larger turbo you are effectively doing that by reducing the restriction so that even at the same boost pressure you will be flowing more air. But the easiest and cheapest way to get more power from a forced induction engine like the Cosworth YB (that was basically designed as a race engine and then detuned for road use) is to increase the boost pressure. By doing that, you are increasing the amount of air going into the engine again.
However, you cannot just increase the boost pressure (done by shortening the rod between the actuator and the wastegate) with a standard chip. The chip contains a table of data (called a map, not to be confused with MAP)so that it knows how long to open the injectors at for a given engine speed, temperature (measured by the Air Charge Temperature sensor) and load (measured by throttle position and/or Manifold Atmospheric Pressure). If you just increase the boost pressure, the Engine Management System won't know how much fuel to add, and when to time the injection and ignition for that amount of air. So if you want to increase boost, you have to have a new, or reprogrammed chip for the EMS/ECU.
Now on most Coswoth YB engines, the MAP sensor has a resistance depending on the pressure that it sees. You give it a 5V signal, and depending on what pressure it sees, you get between 0 and 5V out from it that the EMS can covert to a digital number to know how much pressure is in the inlet manifold (vacuum at idle because the engine is sucking against a 'closed' throttle plate, and positive boost pressure). So the MAP sensor has a range of approximately -1 bar which is the vacuum, and + 1 bar (boost pressure) for a standard MAP sensor for 2wd and 4x4 Sierra's (different for the Escort I believe). That is commonly known as a 2 bar MAP sensor because it's got a range of -1 to + 1 bar.
So without changing the MAP sensor, basically the most boost that you can run is 1 bar. This is commonly known as a Stage 1 tune, and involves upping the boost pressure to 1 bar (or 15 psi from a standard of 10 psi I think) by either shortening the actuator rod on a standard actuator, or better still changing to a -31 actuator that has a stiffer spring inside. The EMS chip is changed to allow the proper amount of fuel to be added and injection and ignition to be timed correctly (failure to do this and just upping the boost pressure will lead to weak mixtures that burn much hotter and will result in catastrophic piston failure). The spark plugs may also be upgraded to cope with the extra heat, and that all important rev. limit may be increased (as the YB was designed to be able to cope with a higher than std. limit).
After that, to get more power you need to look at the 2 restriciting components on the factory engine, the injectors (so called 'yellows' on a std. 2wd because of the colour of them) and the MAP sensor.
1) The 'yellow' injectors only have a small nozzle, and so can only supply enough fuel for the amount of air that goes into the engine when running 1 bar boost, even if they are open for the full duration. The amount of fuel injected is controlled by how long the injector is opened for, and obviously at a given engine speed there is only a certain amount of time that the inlet valve is open and the engine is taking in air and fuel. At over 6000 rpm, this time is very short (measured in thousandths of a second). By changing to injectors with a larger nozzle, so called 'dark greens' or 'greys' or whatever, you can inject more fuel in that same time. Again, you need to have new settings programmed into the EMS so that it knows how long to open these larger injectors for. If you don't, you can imagine that at idle when the engine doesn't need much fuel, if the larger injector is open for the same amount of time as the smaller one, too much fuel will be injected. There are some tricks involving the fuel pressure that can be done to increase the amount of fuel flow through a particular injector, but it's too complicated to talk about here.
2) The MAP sensor. To run more than 1 bar boost pressure, you should have a MAP sensor that can sense this so that the ECU knows the required fuel and ignition. A common upgrade is a 3 bar MAP sensor that can sense from -1 bar to + 2 bar.
Now we have the ability to sense how much air is going into the engine with the MAP sensor, and we have enough fuel to go with it through the larger injectors but it's still not that simple to just wind up more boost.
To get more boost, you have to run the inlet wheel of the turbo (the compressor part) faster. The exhaust wheel is directly connected to it, so that must run faster as well. The faster the engine goes, the more air it can take, and the faster the turbo must spin to feed it that air and pressurise it to the boost level. The standard T3 turbo has a speed limit, and running above that speed will destroy it. Generally, running much more than 1 bar boost at maximum engine speed will mean that the turbo is spinning too fast. If we cannot go any faster with the turbo we have to have a bigger compressor to allow the turbo to force more air into the engine, hence we start talking about T34 turbo's which are basically that.
Now you get other factors coming into play. You know that when you pump up your bike tyres with an old fashioned stylee hand pump that it gets hot, and that when you have a 'shower in a can' the deodorant comes out cold? Well that's because the pressure and temperature of a gas are directly related. If you release the deodorant under pressure in the can to the atmosphere, it gets colder. If you increase the pressure of the air in the bike pump, it gets hotter. The same thing is happening in your turbo, by compressing it, you're making it hotter. A hot gas is less dense than a cold gas. That means that for your 2 litre engine capacity, it may hold for example 2 litres of air at 20 deg. C. which has a weight of 1 kg (just an example, these figures are not actual). But that same 2 litres of air at 60 deg. C only has a weight of 1/2 kg. The amount of fuel that we inject, must be a proportion of the weight of the air in the cylinder, not the volume, to get a properly burnable mixture, so you'd get less power at a higher temperature because although the volume of air is the same, the density is lower so the mass of air is lower and the mass of fuel that you can burn is lower and that is where the power comes from. Now with a turbocharger, we are compressing the air into the engine, so we are increasing the temperature of the air. That is why we have an intercooler - to reduce the temperature of the compressed air and make it denser again so that we can add more fuel. Don't forget that the EMS knows this density from the ACT sensor. Now to the important bit - the higher the boost pressure, the higher the temperature of the induction air leaving the compressor. Therefore we need a bigger, or more efficient, intercooler to run higher boost pressures.
So what have you done to make you think that you have more power than standard?
a) RS500 intercooler - the standard 2wd intercooler is perfectly capable of cooling the air up to 1 bar boost under most conditions. Better is a 4x4 that has a larger surface area, and better still is your RS500 jobber, but the bigger the intercooler, the longer it takes to fill it and pressurise it with boost so the worse the 'lag'. Also, if you cool the air charge too much, the fuel does not mix with the air very well and you don't get good power. By putting an RS500 intercooler on a standard engine you will not increase the power at all over a standard one, you will just increase the lag.
b) Full stainless exhaust - the material change itself will not achieve anything. If you have a larger bore exhaust, you may have reduced the restriction so you have made the engine 'breath better' which may make a slight difference to pick up and turbo spool up time, but probably nothing much in terms of maximum power as the standard exhaust would probably flow enough for standard boost pressure at the standard rev limit.
c) K & N induction kit - same as the exhaust.
d) -31 actuator - even if you are using it to increase the peak boost pressure that typically occurs at about 3500 rpm, that will not increase the peak power that occurs at higher engine speed.
e) Samco hoses - no effect whatsoever.
f) Standard chip - you cannot have any more than standard power if you are not injecting any more fuel than the standard chip tells it to do. For a standard chip, run standard boost, otherwise you risk a catastrophic engine failure caused by incorrect air/fuel ratios.
I would suggest you change back to a standard intercooler and standard boost pressure and you will get a more responsive more reliable car. Or get a T34 or T4 turbo, bigger injectors, 3 bar MAP sensor and an appropriate chip to make the most of the RS500 intercooler that you have.
hope that helps
The mods that you have will not make any difference to the maximum power. The max. power will only be increased if you get more air (and the right amount of fuel to go with it) into the engine.
This is typically done on a normally aspirated engine (i.e. non turbo) by increasing it's volumetric efficiency, commonly known as making it breath better. That means basically that you make it easier for the engine to suck in the air and blow it out again by porting (enlarging the holes that the air goes in and out of) the cylinder head and the manifolds.
Another way of getting more power, is to increase the maximum speed of the engine, i.e. increase the rev limit. This can cause problems if the bottom end (crankshaft, con rods and pistons) are not up to the job. By increasing the speed, you're also increasing the amount of air going into the engine (in the same time), so you get more power, but only if the engine can flow that much air. Typically, factory rev limits are set with the peak power and reliability in mind.
These breathing mods can also be done on a turbo engine and will bring benefits, for example, by fitting a larger turbo you are effectively doing that by reducing the restriction so that even at the same boost pressure you will be flowing more air. But the easiest and cheapest way to get more power from a forced induction engine like the Cosworth YB (that was basically designed as a race engine and then detuned for road use) is to increase the boost pressure. By doing that, you are increasing the amount of air going into the engine again.
However, you cannot just increase the boost pressure (done by shortening the rod between the actuator and the wastegate) with a standard chip. The chip contains a table of data (called a map, not to be confused with MAP)so that it knows how long to open the injectors at for a given engine speed, temperature (measured by the Air Charge Temperature sensor) and load (measured by throttle position and/or Manifold Atmospheric Pressure). If you just increase the boost pressure, the Engine Management System won't know how much fuel to add, and when to time the injection and ignition for that amount of air. So if you want to increase boost, you have to have a new, or reprogrammed chip for the EMS/ECU.
Now on most Coswoth YB engines, the MAP sensor has a resistance depending on the pressure that it sees. You give it a 5V signal, and depending on what pressure it sees, you get between 0 and 5V out from it that the EMS can covert to a digital number to know how much pressure is in the inlet manifold (vacuum at idle because the engine is sucking against a 'closed' throttle plate, and positive boost pressure). So the MAP sensor has a range of approximately -1 bar which is the vacuum, and + 1 bar (boost pressure) for a standard MAP sensor for 2wd and 4x4 Sierra's (different for the Escort I believe). That is commonly known as a 2 bar MAP sensor because it's got a range of -1 to + 1 bar.
So without changing the MAP sensor, basically the most boost that you can run is 1 bar. This is commonly known as a Stage 1 tune, and involves upping the boost pressure to 1 bar (or 15 psi from a standard of 10 psi I think) by either shortening the actuator rod on a standard actuator, or better still changing to a -31 actuator that has a stiffer spring inside. The EMS chip is changed to allow the proper amount of fuel to be added and injection and ignition to be timed correctly (failure to do this and just upping the boost pressure will lead to weak mixtures that burn much hotter and will result in catastrophic piston failure). The spark plugs may also be upgraded to cope with the extra heat, and that all important rev. limit may be increased (as the YB was designed to be able to cope with a higher than std. limit).
After that, to get more power you need to look at the 2 restriciting components on the factory engine, the injectors (so called 'yellows' on a std. 2wd because of the colour of them) and the MAP sensor.
1) The 'yellow' injectors only have a small nozzle, and so can only supply enough fuel for the amount of air that goes into the engine when running 1 bar boost, even if they are open for the full duration. The amount of fuel injected is controlled by how long the injector is opened for, and obviously at a given engine speed there is only a certain amount of time that the inlet valve is open and the engine is taking in air and fuel. At over 6000 rpm, this time is very short (measured in thousandths of a second). By changing to injectors with a larger nozzle, so called 'dark greens' or 'greys' or whatever, you can inject more fuel in that same time. Again, you need to have new settings programmed into the EMS so that it knows how long to open these larger injectors for. If you don't, you can imagine that at idle when the engine doesn't need much fuel, if the larger injector is open for the same amount of time as the smaller one, too much fuel will be injected. There are some tricks involving the fuel pressure that can be done to increase the amount of fuel flow through a particular injector, but it's too complicated to talk about here.
2) The MAP sensor. To run more than 1 bar boost pressure, you should have a MAP sensor that can sense this so that the ECU knows the required fuel and ignition. A common upgrade is a 3 bar MAP sensor that can sense from -1 bar to + 2 bar.
Now we have the ability to sense how much air is going into the engine with the MAP sensor, and we have enough fuel to go with it through the larger injectors but it's still not that simple to just wind up more boost.
To get more boost, you have to run the inlet wheel of the turbo (the compressor part) faster. The exhaust wheel is directly connected to it, so that must run faster as well. The faster the engine goes, the more air it can take, and the faster the turbo must spin to feed it that air and pressurise it to the boost level. The standard T3 turbo has a speed limit, and running above that speed will destroy it. Generally, running much more than 1 bar boost at maximum engine speed will mean that the turbo is spinning too fast. If we cannot go any faster with the turbo we have to have a bigger compressor to allow the turbo to force more air into the engine, hence we start talking about T34 turbo's which are basically that.
Now you get other factors coming into play. You know that when you pump up your bike tyres with an old fashioned stylee hand pump that it gets hot, and that when you have a 'shower in a can' the deodorant comes out cold? Well that's because the pressure and temperature of a gas are directly related. If you release the deodorant under pressure in the can to the atmosphere, it gets colder. If you increase the pressure of the air in the bike pump, it gets hotter. The same thing is happening in your turbo, by compressing it, you're making it hotter. A hot gas is less dense than a cold gas. That means that for your 2 litre engine capacity, it may hold for example 2 litres of air at 20 deg. C. which has a weight of 1 kg (just an example, these figures are not actual). But that same 2 litres of air at 60 deg. C only has a weight of 1/2 kg. The amount of fuel that we inject, must be a proportion of the weight of the air in the cylinder, not the volume, to get a properly burnable mixture, so you'd get less power at a higher temperature because although the volume of air is the same, the density is lower so the mass of air is lower and the mass of fuel that you can burn is lower and that is where the power comes from. Now with a turbocharger, we are compressing the air into the engine, so we are increasing the temperature of the air. That is why we have an intercooler - to reduce the temperature of the compressed air and make it denser again so that we can add more fuel. Don't forget that the EMS knows this density from the ACT sensor. Now to the important bit - the higher the boost pressure, the higher the temperature of the induction air leaving the compressor. Therefore we need a bigger, or more efficient, intercooler to run higher boost pressures.
So what have you done to make you think that you have more power than standard?
a) RS500 intercooler - the standard 2wd intercooler is perfectly capable of cooling the air up to 1 bar boost under most conditions. Better is a 4x4 that has a larger surface area, and better still is your RS500 jobber, but the bigger the intercooler, the longer it takes to fill it and pressurise it with boost so the worse the 'lag'. Also, if you cool the air charge too much, the fuel does not mix with the air very well and you don't get good power. By putting an RS500 intercooler on a standard engine you will not increase the power at all over a standard one, you will just increase the lag.
b) Full stainless exhaust - the material change itself will not achieve anything. If you have a larger bore exhaust, you may have reduced the restriction so you have made the engine 'breath better' which may make a slight difference to pick up and turbo spool up time, but probably nothing much in terms of maximum power as the standard exhaust would probably flow enough for standard boost pressure at the standard rev limit.
c) K & N induction kit - same as the exhaust.
d) -31 actuator - even if you are using it to increase the peak boost pressure that typically occurs at about 3500 rpm, that will not increase the peak power that occurs at higher engine speed.
e) Samco hoses - no effect whatsoever.
f) Standard chip - you cannot have any more than standard power if you are not injecting any more fuel than the standard chip tells it to do. For a standard chip, run standard boost, otherwise you risk a catastrophic engine failure caused by incorrect air/fuel ratios.
I would suggest you change back to a standard intercooler and standard boost pressure and you will get a more responsive more reliable car. Or get a T34 or T4 turbo, bigger injectors, 3 bar MAP sensor and an appropriate chip to make the most of the RS500 intercooler that you have.
hope that helps
