Want to boost?...read this thread first!

[Winkty]

I wanted to create a thread to provide information to the people who want FI, but don't really have a clear understanding of it. I made some quick descriptions of MAFS and BPV/BOV/DV to start this thread off.

Hopefully this will become a sticky, and will help other people. Please add anything you feel is needed or anything people commonly asked about when choosing to boost their car.

Here we go.....




What’s better: Supercharger or Turbo?


This is a VERY complex question. The better option will depend a lot on your personal opinion. Please refer to the FI “sticky’s” to answer this question. They will have the best descriptions that will help you decide between them.


Should I run a "Blow-Thru" or "Suck-Thru" MAF?


I guess I should explain the MAF sensor a little bit better. The MAFS is a sensor that measures the mass of air that is entering the motor. With this sensors data, the cars computer can calculate how much fuel to inject (A/F ratio), load (VE), etc...

Suck-thru refers to the MAFS being positioned on the INLET side of the turbo/SC. Air will be sucked thru the MAFS to get readings.
Blow-thru refers to the MAF being mounted on the outlet or "boost side" of the turbo. Air will be blown thru the MAF to get readings.

Both setups have been proven to work well. With a blow-thru setup, you will be able to run a "vent to the atmosphere" BOV because the BOV will be placed before the MAFS and it wouldn't have "metered" the air that is released. The MAF will never even see the air that is released from the BOV in this setup, so it WON’T inject more fuel for it. This MAFS setup is sometimes harder to tune, though.

With a suck-thru setup, since the BOV is AFTER the MAFS, the air would already be “metered”. The MAFS already read the amount of air and will inject enough fuel for all of it, whether you release it or not. The MAFS will NOT know if you released air AFTER it. For example – If the MAF reads an intake of 15lbs/min of air, but you “blow off” some of that air to the atmosphere…it will still inject enough fuel for the FULL 15lbs/min because it doesn’t know you lost any air. This is why you get a rich condition between shifts (when you blow off). A bypass valve type of system is pretty much required with this setup. The plumb back hose should enter back into the intake track BEFORE the turbo/SC and AFTER the MAFS.


Should I run a blow off valve or bypass/diverter valve?

Blow off valves and bypass/diverter valves are often passed off as the same thing. Even though they accomplish the same thing, they do not work the same. A BOV typically (some CAN be plumbed back) releases air to the atmosphere instead of back into the intake track. A BOV also will STAY CLOSED under vacuum/idle situations. It will only open when you let off the gas (vacuum line to the BOV will show a vacuum) and there is residual pressure in the intake piping to force the valve open. Turbo setups typically use a BOV, but centrifugal S/C’s can also use them with some tuning/EM/hardware changes.

A bypass/diverter valve is plumbed back into the intake track. Bypass/Diverter valves stay OPEN at vacuum/idle situations. These are mainly used on superchargers because of this feature (open at idle), but can be used on turbo setups with no problem.

The decision between the two is mainly dependent on 2 things. (1) What MAFS setup are you going to run? (2) Do you like the “whoosh” sound of the BOV?

Please read the above few paragraphs to choose a proper MAFS setup.

If you like the “whoosh” sound, you should consider the blow-thru MAF setup only. With a suck-thru setup, plumbing back the BPV or BOV will deaden that sound quite a bit.

[Spatakula]

ooo new stickie time.

-spatakula

[c4uldr0n]

even though there are alot of variables, you should also note which injectors you should use for a given/wanted powerband for a FI car. ZX2RACING had a good formula.

NA = injectors size / 0.45 * cylinders
FI = injector size / 0.55 * cylinders

I used the formula and calulated hp per injector size. note those would be MAX rates, and you should never max your injectors out, 85-90% would start to get scary. If anybody can object, I'll glady remove my results.

19lb injectors 140hp FI / 168hp NA
24lb injectors 175hp FI / 210hp NA
30lb injectors 218hp FI / 265hp NA (unlikely for NA)
42lb injectors 305hp FI / 373hp NA (very unlikely for NA)
60lb injectors 435hp FI / 533hp NA (very very unlikely for NA)
72lb injectors 520hp FI / 640hp NA (very very very unlikely for NA)

[Winkty]

Internal vs External Wastegate


Wastegates work kind of like a relief valve. They provide another path for the exhaust gases to flow.(instead of flowing thru the turbo) A turbo spools because of heat, pressure, and flow created by exhaust gases...so if you divert the exhaust gases to somewhere else besides thru the turbo (back to the exhaust, post turbo or atmosphere)...it will spin the turbo shaft slower and make less boost. Go it?

Now lets talk about how they open. Almost all wastegates use springs to hold the valve shut. There is also a boost reference line (typically run from the compressor housing of the turbo) that is connected to the wastegate which will open the wastegate valve (via a diaphram) at a specific pressure. The pressure that the wastegate opens at is determined by the spring we already talked about. If the spring is stiffer (harder to compress), it will open at a higher PSI....if it is softer (easier to compress), it will open at a lower PSI. That's why they sell springs for wastegates according to PSI. For example - If you buy a wastegate with an 8 psi spring...once the turbo makes 8 PSI...the boost reference line will show 8 psi at the wastegate and open the valve. When it gets below 8 PSI, the valve will close until you make that PSI again. The wastegate will constantly regulate the spooling of the turbo so that you make a solid 8 PSI the whole time.



External Wastegates - Most external wastegates use a piston style valve in them to regulate the flow of exhaust thru them. Typically these are a larger diameter and better flowing design than the internal wastegates. For this reason, external wastegate are better at controlling boost...more so at higher HP levels because of flow. Ext. wastegates are also typically more durable than internals because of the build quality and materials used. Another thing is Ext. wastegates can be vented to the atmosphere (via a dump tube) or back into the exhaust. While venting the wastegate to the atmosphere is a great flowing (and normally easier) solution, most people don't like it because of the "wide open" exhaust sound. When the wastegate opens, it will sound like you don't have much of an exhaust anymore. This is a GREAT addition to a turbo setup if you have the money.


Internal Wastegates - There are a few things that are different about internal WG's. First, they use a "flapper" style valve in them instead of a piston type. The "flapper" valve is typically mounted directly on the exhuast housing of the turbo which makes them ONLY dump/vent into the exhaust. They typically don't flow as well as external style. They also use an externally mounted actuator (which sometimes causes fitment issues in the car) to open the wastegate valve. It still uses a diaphram type of opening mechanism, but probably doesn't use the higher temp materials the external does. (because the external is mounted directly on the manifold normally and takes a lot of heat) Internal wastegates are normally perfect for cheap, reliable boost control. Factory cars have been using them for years. I think they work very well for low-mid boost applications. (my opinion)

[Winkty]

c4uldr0n - Great addition!

Please PM me if you notice I said something wrong or missed something.

Thanx guys.

[c4uldr0n]

about internally gated... if you buy an internally gated turbo from say a factory VW or SUBARU, you will have to clock the turbo compressor and will probably lose the ability to use that internal gate feature unless you fab up a new mount point for the actuator. It will not always be this way, but there is a good chance. You at this point have the option to weld the flapper shut and use external wastegate or create a new mounting bracket which can be a PITA

[orangeZXT]

may need to add NEED TUNE FOR SURE great idea bro

[Darth_Focus]

Advantage to 'blow through MAF".....when you blow a turbo pipe off, you have an NA car with cool spooling sounds...

[orangeZXT]

^^^^^^^the cool spooling sound will KILL a turbo like that u can over spin it

[sprout2287]

Spark/ignition timing...

When someone referrs to "pulling timing" from the motor, what does that mean?

When your motor is in operation, the crank is spinning and the pistons are moving up and down. The angle of the crankshaft determines the height of any individual piston at any given time. If a piston is at the highest point it is at what is called "top dead center" or TDC. At that position, that piston's lobe on the crank is at it's highest point in it's rotation within the motor. This is zero degrees.

The ignition system is set to precisely administer a spark from the spark plug at a given crank angle for each individual piston. The degree at which the spark is ignited, in a focus, is measured in terms of degrees before dead center, or BDC. If the spark is lit sooner, the car can make more power. Since it's degrees before TDC, a higher number means the spark happens earlier, as lower numbers mean later, or closer to zero.

This increase in power is limited by the engine's/ fuel's/ compression ratio's/ pent roof design's/ etc. etc. resistance to knock. If the spark is lit later than the optimal time, there will be a decrease in power production.

There are, of course, limits to how early or late the spark can be administered anyway. You can't just keep adding timing and keep making more power. The spark will be ineffective if the cylinder has not yet properly compressed the fuel/air mixture, or if the spark is so late that not all of the fuel has time to burn.

So, adding timing is making the spark ignite sooner in the cycle than it would otherwise. And decreasing timing is making the spark ignite later.

Why is all of this important for unnaturally aspirated cars???

When more air, and therefore more fuel, are added to each cylinder than is expected by the computer (stock tune), ignition timing must be decreased (retarded) to keep the car from knocking. Cylinder pressure and temperature will be too high if the spark is ignited too early. This can cause the motor to knock and can cause melted pistons and broken connecting rods.

Added note:
The focus computer is designed to modify ignition timing based on many different variables. It can add or subtract various degrees of timing depending on the amount of load it calculates that the engine it experiencing, the position of the throttle, and many other things. It is designed to decrease timing, for instance, when the coolant or air temperature are abnormally high, or when the oxygen sensor is reading a leaner than expected condition.

Keep in mind that the focus stock timing maps are designed for fuel efficient, 105 wheel horsepower, 87 octane gulping, grocery getting machines, with stock everything.

^^^All of this ^^^ is not to be confused with cam timing, which is a whole other thing, having little to do with what I just typed and containing more information than I am willing to explain in tonight's posting...

[Ray]

Thanks Winkty for getting this started, and the others for helping out - adding to the references thread.

[Darth_Focus]

..lol, I didnt mean drive that way (Pipes blown off). You just arent stalling and dumping fuel. Id blow a pipe and just pull off and reconnect it.

One of these days I will sand down around the pipes and use a self drying solvent to clean the pipes....then it'll hold...

[Ray]

if your pipes are blowing off, make sure they're beaded, or at least bead welded. if they are, make sure you are using good couplers, and if they still are, upgrade to T bolt clamps. (or just do all of the above and dont worry about it)

[Dukman]

Yes thank you Winkty, I'm still trying to learn and get a handle on all this FI stuff. (Just ask Demon, Slick and Bela I must bug the crap out of em with my questions)

That write up helps me to understand the whole MAF deal.

[belacyrf]

Ok, here is my contribution.

Here are some tuning details that should help any newb get some basic understanding of what people are talking about when we discuss tuning.

Gloassary of terms or acronyms
MAFS Mass Airflow Sensor: Measures the MASS of air entering into the system (Mass <> Volume, they are different)
ECT Engine Cooling Temperature: Coolant Temps (pretty obvious)
EGT Exhaust Gas Temperature: Exhaust Temps usually taken within 3 to 6 inches from the exhaust ports
IAT Intake Air Temperature: Temperature of the air entering into the intake manifold
A/F Air Fuel Ratio: The measurement of the Mass of Air in relation to the Mass of fuel
Stoichiometric 14.7 Air Fuel Ratio, the "ideal" combusions mixture for gasoline (also referred to as 1 Lambda)
CR Compression Ratio: Normally referring to the Static Mechanical Compression Ratio

VE Volumetric Efficiency: The naturally aspirated efficiency of the engine at a given RPM. 100% Efficiency would be = CID x RPM/3456
- For the SVT Focus 100% Volumetric Efficiency at 4000 RPMS is 121 X 4000/3456 (121 being the CID or displacement for the SVT Focus)
- So basically VE is the Theoretical Displacement at a given RPM compared to the Actual Displacement of that engine at that same RPM.
- Using the previous example, 100% effiency at 4000 RPMs for the SVT is 140 SCFM (Standard Cubic Feet/Minute)
- If the SVT only is flowing 100 SCFM at 4000 RPM's than it is only 71% efficient at 4000 RPMs

Load Load is the same as VE. 100% VE is 100% load. Obviously Forced Induction can push more air through an engine than it can normally breath in NA form, so Load is often over 100%.

Volts to Counts Conversion VOLTS X 204.6 = Counts

The MAFS
When looking at the ECU Calibration, one of the main parameters is the MAF Table
The 2002 Mustang GT MAF Table looks something like this:



The table above shows 4 columns, when in tuning there is only three. Normally the MAF table will show you MAF Counts OR Volts, not both. In tuning you can adjust the Volts and the #/Min fields to get your A/F Adjusted


Almost any tuning parameter will be based on one of the params listed above.
Timing can be based on Load, RPM, ECT, or IAT

Understanding each of these things will help set a decent foundation for learning how to tune your car.

[Ray]

Bela - i'm going to add to your post that timing is not based on ECT or IAT, but rather, can be influenced by it. Timing is based (in my experience) on load and engine speed (RPM). So if your base timing at 80% load at 5k is 17degrees, if your IAT exceeds X (let's say 140degrees) the car will start to pull timing, same for the ECT if it exceeds Y (230?), so while if the car has a low IAT and lower ECT than the timing table says to pull, it will have 17, but could be as low as 10 (example). So when datalogging be sure to be aware that what you demand might not be what you get if you're running hot and / or heatsoaked.

[Winkty]

Now we are getting somewhere with this thread.

Thanx for the additions, guys.

[sc0tty8]

Someone should add the info of how much you mill to get what CR and what gasket to add to get what CR. I am going to need that info

[belacyrf]

Originally Posted by demonfire

Bela - i'm going to add to your post that timing is not based on ECT or IAT, but rather, can be influenced by it. Timing is based (in my experience) on load and engine speed (RPM). So if your base timing at 80% load at 5k is 17degrees, if your IAT exceeds X (let's say 140degrees) the car will start to pull timing, same for the ECT if it exceeds Y (230?), so while if the car has a low IAT and lower ECT than the timing table says to pull, it will have 17, but could be as low as 10 (example). So when datalogging be sure to be aware that what you demand might not be what you get if you're running hot and / or heatsoaked.

Actually that's not 100%

You can alter your timing based on ECT and IAT as well. Granted it's not in the main table but there are other tables that can add or subtract timing based on ECT and IAT's. So yes while ECT and IAT are not the main contributing factors, they are definately a basis for where your timing is.

Originally Posted by sc0tty8

Someone should add the info of how much you mill to get what CR and what gasket to add to get what CR. I am going to need that info

Scotty, that's getting into Car Specifics and will differ per engine. Kind of a different story.

[BUR_ZX3]

To add to Bela's glossary:

ACT: Air Charge Temp... aka IAT.

[Winkty]

Here's another big one:

Do I need to upgrade to a 3" exhaust on my Supercharged or Turbocharged car?


Exhaust sizes are something that have been debated A LOT over the years. I will try to explain this the best I can. This is what I have read and learned over the years...some might not be 100% correct (or my personal opinion)...but it should give you a pretty good idea of what you need. Please correct me if I am wrong on anything.

What about backpressure if i put a 3" exhaust on my car?

This is the question I pretty much hear from everyone. The truth is, backpressure is NOT what you need to worry about. Backpressure is only the measure of restriction in the exhaust. You need to worry about EXHAUST GAS VELOCITY the most. You also need to worry about SCAVENGING, which has a direct relation to the velocity of the exhaust gases. Let me explain a little bit better. While your car is running, there are exhaust gases constantly moving thru the exhaust tubing. These gases moving out of your exhaust tubing can also be used to "pull" exhaust gases out of your cylinders. This situation is called scavenging. Typically, the faster the gases are moving, the more benefits you get from scavenging. Keep in mind that your exhaust header/manifolds affect the scanvenging a lot also, but I will not go into that right now. Heres where it gets a little tricky.

The larger the tubing, the SLOWER the exhaust gases are flowing. This will cause LESS scavenging, but will flow MORE than a smaller tube.

The smaller the tubing, the FASTER the exhaust gases are flowing. This will cause MORE of a scavenging effect, but will flow LESS than the larger tube. If you reduce your tubing size too much, the benefits of scavenging will quickly go away and you will be stuck with tubing that is too small for your motor...period.

People always claim they lose low end TQ because of the "backpressure" they lost with a larger exhaust. What they are really losing is the scavenging effect.


Turbocharged Cars: I personally have NEVER seen a turbo car that did not benefit from a 3" exhaust system. Turboed cars are a different animal all together. You will ALWAYS want a free flowing exhaust after the turbo. You want positive pressure BEFORE the turbo, NOT after it. Any restrictions after the turbo will slow it's spool time. I would say not ALL turbo setups NEED a 3" exhaust, but they would benefit from it. If your not looking for max power...I would say forget about the 3" exhausts, and go with 2.5''. (my opinion again)

Supercharged Cars: Now this ia ALWAYS a question on FJ. Would your S/Ced car benefit from the extra flow of the 3" exhaust. Probably, if you are looking to make the most HP you can. Would your S/Ced car benefit just as much as a turboed car? Plain and simple...no it won't. Mainly because your power adder is dependent on your engine speed and not your exhaust gas flow. For MOST S/Ced cars, 2.5'' exhausts are PLENTY big enough. In my opinion, for a S/Ced car, you should build the exhaust just the same as a nice (free flowing) N/A exhaust. (obviously taking your HP goals into consideration, also)

[orangeZXT]

may be good to add some stuff on the J&S