Turbo charging MA12
- Thread starter NathanHug
- Start date
gtsnissanb
Official MSC Trader
It's what I'm doing
but currently lost motivation and thinking it's kind of a waste of time, got a T3 stuck in mine at the momentIt isn't hard to turbo charge anything providing your good with a welder
It's the fine tuning of the carb that's the pickle, you'll also be told that you'll need a pressure box or mount the carb differently but I'm sticking with the oe position of the oe carb! If it breaks I'll get another if I blow the engine I'll bin it and stick in an SR
Also so far I've spent very little indeed <£100 and it's basically just needs a selection of pipes and oil feeds to get running
a pressure box encases around the carb to keep the pressure equal inside and out side the carb so the carb doesn't leak.
i think what gtsnissanb means is people usually opt for something like a renault 5 gt turbo carb and modify it to fit the k10 manifold. which is a good idea but imo the standard carb is fine it just needs the jets playing with a bit.
i think what gtsnissanb means is people usually opt for something like a renault 5 gt turbo carb and modify it to fit the k10 manifold. which is a good idea but imo the standard carb is fine it just needs the jets playing with a bit.
gtsnissanb
Official MSC Trader
Pressure box is basically you build an air tight box to fit the carb into to stop the turbo pressure from killing the carb
The mounting differently means draw through or blow though
Draw through turbo suck air and fuel through the carb but for obvious reasons not the safest of methods IMO!
Blow through pretty self explanatory mount the carb after the turbo so turbo blows through carb which is my method with no pressure box! Just to see if it breaks or not
The next issue is securing the pipe onto the carb as the rim of the carb is very small if you can get around that then your laughing
gtsnissanb
Official MSC Trader
Bit of Internet searching
Draw-Through: Generally speaking, there's 2 ways to use a carburetor with a turbo engine...draw-through or blow-through. The draw-through arrangement is where the carb is arranged first and the turbo then sucks air through the carb. This has the benefit that it doesn't require any special carb changes because the carb is just seeing more air flow through it. The main drawbacks are that the fuel-air mix must pass through the turbo. Since fuel is denser than air it will tend to separate in the turbo and puddle up. Don't expect instant off-idle throttle response. The turbo also becomes less efficient because it has to pump this heavier fuel mixture, and it is trying to do it's job after the carb has already caused a pressure drop. You basically have the carb causing a pressure drop and the turbo trying to increase the pressure. The efficiency losses translates into a hotter fuel-air mix in the engine which limits the boost you can run and your power.
Now here's the confusing part to me. The majority of the people with Carbureted Turbos run them in a draw-through arrangement and they say you get more power that way. Personally I don't agree with that thinking and some of my research has led me to believe otherwise. I tend to believe that the power difference they speak of is related to people not using fuel enrichment in a blow-through setup. I have not tried either so you should make your own decision and there are certainly plenty of engine builders who would argue the point.
In addition, In a draw-through system it is possible to create an extreme vacuum if the turbo is at boost and you shut the throttle. This vacuum will have a tendency to suck the oil out of the bearings. You will need to use a turbo with a positive seal on the compressor in a draw-through arrangement. Diesel turbos do not have this seal. I think most gasoline cars do have a positive oil seal but with the popularity of fuel injection on the newer cars I'm not positive.
Blow-Through: In a blow-through arrangement the turbo is going to blow pressurized air through the carb and then into the intake. This presents two problems: First, a carburetor does not understand pressure. Remember, a carburetor supplies fuel by creating a pressure drop across the venturi. If the carb sees a 2 PSI pressure drop across the venturi, it will supply that much fuel whether you are at 0 boost or 15 pounds of boost. This would cause the engine to run very lean at max boost, but it can be fixed with some form of fuel enrichment. The second problem you will encounter is that when you put pressurized air into the carb, it will make the fuel flow in ways that it is not suppose to flow. The pressure will try to crush the fuel float, it's going to want to blow fuel mix out the throttle shaft, or back into the fuel line. Don't be discouraged though these problems have all been overcome with varying degrees of success. The book Turbocharging by Hugh MacInnes covers a lot of the carburetor mods you can implement to have a successful blow-through turbo setup.
Carb Sealing: The entire carb must be sealed so it does not leak the pressurized air-fuel mix. I've heard that Dellorto carbs have ball bearings and mechanical seals so they may not need further sealing. On other carbs the throttle shaft rides inside a brass bushing, the leaking can be "fixed" by running a hose from the top of the carb where there is more pressure to a fitting that will pressurize the area around the shafts with "clean" air. Note: This method will leak clean air, but not leak the much more dangerous air-fuel mix. In a closed engine compartment, leaking fuel vapor is even more dangerous so please be careful. The metal plugs on the carb could blow out under the increased pressure. Use a punch and put several "dings" around the outside of the plugs to hold them in better. Others have used epoxy on the plugs.
Some have also set the entire carb inside an airtight box. You will then need to seal the opening for the throttle cable by using a sealed marine cable or a similar "trick".
Fuel Pressure: You will need to use an electric fuel pump and a boost sensing fuel pressure regulator to increase fuel pressure as boost pressure increases. Remember every pound of boost that comes out of the turbo is another pound of boost that the fuel pump must be able to overcome if it wants to push fuel into the carb. Read the "Fuel System" page for background on a turbo fuel pressure regulator. With a carb, you will not need a high pressure pump and regulator like you do in an EFI application, so a decent quality electric fuel pump and regulator should suffice.
The fuel floats should be filled with foam so they don't crush under the increased pressure. Some manufacturers sell floats designed to withstand the increased pressure.
Carburetor Type and Size: In most cases the same sized carburetor is used on a turbo installation. Many people use a side draft or downdraft Weber 40 or Dellorto.
Fuel Enrichment: Your carburetor does not take into account boost pressure when it supplies fuel to the motor. Because of this you must take certain steps so that it supplies the correct amount of fuel when the turbo is at the maximum boost level.
What most people seem to do is to jet the carb so that at max boost they have enough fuel. The problem with this method is that the engine will run rich at lower than max boost pressures which is also where most of your driving is done. A better method is to use a carb with a power valve and reference the valve to boost pressure. That requires possibly drilling some holes and running some vacuum lines. Some people have used a 4 barrel carb with vacuum operated secondaries. In this case the secondaries are jetted and plumbed so that they open during boost.
The other alternative is to use external means that can overcome the inability of the carb to understand boost pressure. These fall into two categories, a "dumb circuit", and a smart controller.
The first type of circuit uses a pressure sensing switch to open a fuel solenoid. The fuel then sprays into the intake through an orifice. You set the pressure switch at what boost point you want the fuel enrichment to occur. As you can probably guess this system will not properly meter the fuel flow but it is better than nothing.
The smart controller is an advanced electronic box that has the capability to meter the fuel flow depending on how much boost the turbo is giving the engine. With a "smart" controller your fuel curve will more closely match the air requirements of the engine and allow you to jet the carb as you would for a normally aspirated engine. The inexpensive ($150) Tim Systems controller pictured below works much like a mini fuel injection system. You use a regular fuel injection pump, 1 to 4 injectors, a pressure regulator, a MAP sensor and inject the enrichment fuel of your choice.
Draw-Through: Generally speaking, there's 2 ways to use a carburetor with a turbo engine...draw-through or blow-through. The draw-through arrangement is where the carb is arranged first and the turbo then sucks air through the carb. This has the benefit that it doesn't require any special carb changes because the carb is just seeing more air flow through it. The main drawbacks are that the fuel-air mix must pass through the turbo. Since fuel is denser than air it will tend to separate in the turbo and puddle up. Don't expect instant off-idle throttle response. The turbo also becomes less efficient because it has to pump this heavier fuel mixture, and it is trying to do it's job after the carb has already caused a pressure drop. You basically have the carb causing a pressure drop and the turbo trying to increase the pressure. The efficiency losses translates into a hotter fuel-air mix in the engine which limits the boost you can run and your power.
Now here's the confusing part to me. The majority of the people with Carbureted Turbos run them in a draw-through arrangement and they say you get more power that way. Personally I don't agree with that thinking and some of my research has led me to believe otherwise. I tend to believe that the power difference they speak of is related to people not using fuel enrichment in a blow-through setup. I have not tried either so you should make your own decision and there are certainly plenty of engine builders who would argue the point.
In addition, In a draw-through system it is possible to create an extreme vacuum if the turbo is at boost and you shut the throttle. This vacuum will have a tendency to suck the oil out of the bearings. You will need to use a turbo with a positive seal on the compressor in a draw-through arrangement. Diesel turbos do not have this seal. I think most gasoline cars do have a positive oil seal but with the popularity of fuel injection on the newer cars I'm not positive.
Blow-Through: In a blow-through arrangement the turbo is going to blow pressurized air through the carb and then into the intake. This presents two problems: First, a carburetor does not understand pressure. Remember, a carburetor supplies fuel by creating a pressure drop across the venturi. If the carb sees a 2 PSI pressure drop across the venturi, it will supply that much fuel whether you are at 0 boost or 15 pounds of boost. This would cause the engine to run very lean at max boost, but it can be fixed with some form of fuel enrichment. The second problem you will encounter is that when you put pressurized air into the carb, it will make the fuel flow in ways that it is not suppose to flow. The pressure will try to crush the fuel float, it's going to want to blow fuel mix out the throttle shaft, or back into the fuel line. Don't be discouraged though these problems have all been overcome with varying degrees of success. The book Turbocharging by Hugh MacInnes covers a lot of the carburetor mods you can implement to have a successful blow-through turbo setup.
Carb Sealing: The entire carb must be sealed so it does not leak the pressurized air-fuel mix. I've heard that Dellorto carbs have ball bearings and mechanical seals so they may not need further sealing. On other carbs the throttle shaft rides inside a brass bushing, the leaking can be "fixed" by running a hose from the top of the carb where there is more pressure to a fitting that will pressurize the area around the shafts with "clean" air. Note: This method will leak clean air, but not leak the much more dangerous air-fuel mix. In a closed engine compartment, leaking fuel vapor is even more dangerous so please be careful. The metal plugs on the carb could blow out under the increased pressure. Use a punch and put several "dings" around the outside of the plugs to hold them in better. Others have used epoxy on the plugs.
Some have also set the entire carb inside an airtight box. You will then need to seal the opening for the throttle cable by using a sealed marine cable or a similar "trick".
Fuel Pressure: You will need to use an electric fuel pump and a boost sensing fuel pressure regulator to increase fuel pressure as boost pressure increases. Remember every pound of boost that comes out of the turbo is another pound of boost that the fuel pump must be able to overcome if it wants to push fuel into the carb. Read the "Fuel System" page for background on a turbo fuel pressure regulator. With a carb, you will not need a high pressure pump and regulator like you do in an EFI application, so a decent quality electric fuel pump and regulator should suffice.
The fuel floats should be filled with foam so they don't crush under the increased pressure. Some manufacturers sell floats designed to withstand the increased pressure.
Carburetor Type and Size: In most cases the same sized carburetor is used on a turbo installation. Many people use a side draft or downdraft Weber 40 or Dellorto.
Fuel Enrichment: Your carburetor does not take into account boost pressure when it supplies fuel to the motor. Because of this you must take certain steps so that it supplies the correct amount of fuel when the turbo is at the maximum boost level.
What most people seem to do is to jet the carb so that at max boost they have enough fuel. The problem with this method is that the engine will run rich at lower than max boost pressures which is also where most of your driving is done. A better method is to use a carb with a power valve and reference the valve to boost pressure. That requires possibly drilling some holes and running some vacuum lines. Some people have used a 4 barrel carb with vacuum operated secondaries. In this case the secondaries are jetted and plumbed so that they open during boost.
The other alternative is to use external means that can overcome the inability of the carb to understand boost pressure. These fall into two categories, a "dumb circuit", and a smart controller.
The first type of circuit uses a pressure sensing switch to open a fuel solenoid. The fuel then sprays into the intake through an orifice. You set the pressure switch at what boost point you want the fuel enrichment to occur. As you can probably guess this system will not properly meter the fuel flow but it is better than nothing.
The smart controller is an advanced electronic box that has the capability to meter the fuel flow depending on how much boost the turbo is giving the engine. With a "smart" controller your fuel curve will more closely match the air requirements of the engine and allow you to jet the carb as you would for a normally aspirated engine. The inexpensive ($150) Tim Systems controller pictured below works much like a mini fuel injection system. You use a regular fuel injection pump, 1 to 4 injectors, a pressure regulator, a MAP sensor and inject the enrichment fuel of your choice.
easiest method: get a electrical fuel pump, a fuel regulator which depends on boost (boost+ 0,7bar), a k10 super turbo exhaust manifold, a proper turbo, a boost controller etc (what you need to controll the boost), some pipes to connect the turbo to the carb, oil feed (this is what I am concerned of... where to grab the oil feed for the turbo? at the filter?)
get the feed from the pressure switch just get a t-piece adapter so you can still run the switch. thats what i did and worked great. (Y)
gtsnissanb
Official MSC Trader
A proper turbo? T3 is proper enough for me
porkpie700
Buy & Sell Member
The easiest way to do it is to get yourself all the bits from a fig, transfer them onto your ma12 and then have it mapped to work with the bigger engine. It's all do-able it just comes down to weather you've got the money to play with or not. Turbo charging is next level stuff and it costs, you need to think about the cam/head upgrades that would be needed, and can the crank, con-rods & bearings take the extra power etc...
There's a lot of crap involved to do it right and weather or not a 1.2 will take the pressure is open to question. When nissan made the super turbo they strengthened the cylinder walls by reducing the displacment to make them a little thicker. There's a chance that the ma12's cylinder walls might not hold the boost of a turbo.
Personally i'd reccomend buying a complete fig engine with fuel pump and all the electrical bits and drop that in. But that's just my take on things.
There's a lot of crap involved to do it right and weather or not a 1.2 will take the pressure is open to question. When nissan made the super turbo they strengthened the cylinder walls by reducing the displacment to make them a little thicker. There's a chance that the ma12's cylinder walls might not hold the boost of a turbo.
Personally i'd reccomend buying a complete fig engine with fuel pump and all the electrical bits and drop that in. But that's just my take on things.
gtsnissanb
Official MSC Trader
The st runs more boost than an turboed NA would need to.
swapping the fig bits sounds allot harder and more expensive
I thought it had the displacement lowered so it could compete in a lower class?
iv tried to fined a few fig bits to fit to the ma12 and they are few and far between and not very good value for what your getting, im working on a well tight budget so im thinking about getting a new carb that is suitable for a turbo and a turbo,
any suggestions on what carb and what turbo would be cheap and practical to fit ?
also what kind of pressure is safe ?
any suggestions on what carb and what turbo would be cheap and practical to fit ?
also what kind of pressure is safe ?
gtsnissanb
Official MSC Trader
the standard carb will be fine! There is no information about it on the net, but I can guarantee you it will hold the boost properly. I think someone mentioned on here that he ran a t28 with the standard carb. (in my opinion way too big
T28 is too big I'm running a T3 lol
You'd be best off getting a pug derv T15 or KkK equivalent
Or at worst a t2 from a fiesta or R5
frank
Club Member
the standard carb will be fine! There is no information about it on the net, but I can guarantee you it will hold the boost properly. I think someone mentioned on here that he ran a t28 with the standard carb. (in my opinion way too big
i cant believe the stock carb will run under boost fwn it,ll just blow the fuel back up the mainjet and run megga lean.
and one day someone will actually turbo a k10
i must have seen al least 10 wannabe,s/abandoned projects on here
gtsnissanb
Official MSC Trader
i cant believe the stock carb will run under boost fwn it,ll just blow the fuel back up the mainjet and run megga lean.
and one day someone will actually turbo a k10
You don't have to believe it as it's been done
I think nissan may have done it in the past also
lolI've not given up just skint
You don't have to believe it as it's been done
I think nissan may have done it in the past also
I've not given up just skint
(Y) thanks for your backup
frank
Club Member
You don't have to believe it as it's been done
I think nissan may have done it in the past also
yeh, thats why nissan fitted injection to the figs and st,s fwn
gtsnissanb
Official MSC Trader
Ah but you never said a carb k10 just a k10
I think this as economical reasons
and of course it is easier to map this. turboing a carb is always a lot of work to get the air-fuel ratio right in every situation.but I think you now this
gtsnissanb
Official MSC Trader
I think this as economical reasons
but I think you now this
It's not really that difficult off boost it responds like a na engine so no different then when on boost more air is forced in so the carb would bung in more fuel, but I'm not to up on my carbs hence why I'm doing it to get a better understanding! I'm a rx7 tuner/builder so carbs are fairly alien to me
