This thread is being started not as an open discussion but as an informational thread to help people get those questions about different performance aspects answered so they have a better knowledge, not only for themselves, but for others as well. This is NOT a debate thread or I am right you're wrong thread. This is a, ask a question and I will answer your question with either references or reading material to back it up. Any posts that are not a direct Q&A will be deleted.
Let's keep this thread clean and to the point. So with that being said, let's see your questions.
Any cons other than cost to twin charging?
What is the difference between an intercooler and a heat exchanger?
What is the difference between turbocharging and supercharging?
Is it worth putting dual exhaust on a stock 2.2L?
What is the difference between a Wastegate (WG) and a Blow-off Valve (BOV)?
What is the difference between a BOV and a Diverter Valve (DV)?
CO2 FMIC Spray? Any advantages?
Why do some people run Methanol injection?
E85? Good or Bad?
Are there advantages to using the CO2 spray or Meth in NA cars, or are the costs far out weighing the gains?
What is the importance of having Limited Slip Differentials (LSD)?
What are those things that are above the rear windows on some cars? They look like little bumps.
What is the most important things to make sure you have before tuning?
Why are Air/Fuel Ratios (AFR's) so important?
Whats the difference between getting medium length headers and a regular size downpipe, versus getting long tube headers and a short downpipe?
What is the difference between a 4-1 and a 4-2-1 header?
Can any header be modified to be used with a turbo?
What is a 2 Step?
What is NLTS and how does it work?
What is SD, and what is it's advantages/disadvantages?
1. Q;Any cons other than cost to twin charging?
That all depends on the twin charge setup you go with, as you could probably guess, there are turbos that can out flow superchargers. When twin charging you need to look at the flow charts of both components you are looking at to make sure you're not going to restrict more flow from the other component. The only cons I can think of to twin charging is the traction problems, clutch problems (as you would need one that could handle a good amount of torque because of the instant torque), cost (obviously), and space depending on how your engine is setup and whatnot. Twin Charging is not always the best tho, but that all depends on the application the build is going to be used for. If you're going for high numbers or super fast 1/4 mile times, most guys realize that going a much bigger turbo is better than twin charging, thus save the extra money just to go full turbo. If you're looking for auto-x or something like that, a twin charge setup would probably be best as you get the instant power down on the bottom end coming out of the turns and would have the better top end from the turbo. So really the application can vary the cons and pros that you can get out of twin charging. Hope that answers your question.
2. Q;What is the difference between an intercooler and a heat exchanger?
That's actually a pretty good question there. Intercoolers and heat exchangers actually serve the same purpose, but they go about it a different way. Intercoolers use what is called "Air to Air" cooling, as it only uses air to cool off the air flowing through it. Heat exchangers on the other hand use "Air to Water", kind of like a radiator, to cool the air flowing through it. Intercoolers are actually 99% of the time what you would see used in a turbo'd application, however I have seen the VERY rare time where someone has used a heat exchanger for a turbo application. Heat exchangers generally are associated with supercharged cars. However, when some people use prochargers, they tend to just use intercoolers to save on weight and space. That is the difference between an intercooler and a heat exchanger.
3. Q;What is the difference between turbocharging and supercharging?
This is probably the MOST common question when it comes to perfomance, right next to, "how do I increase my boost?" Turbocharging and Supercharging both serve the same purpose, but go about it differently. Superchargers (this is to include prochargers and "blowers") are belt driven that can make instant boost regardless of the RPM's that you're at. Supercharging always comes with it's cost though. Ever hear anyone use the term, "it takes power to make power"?. That's exactly what it means when you run a supercharger. Because the supercharger is belt driven, it puts extra load/lag on your engine. Most superchargers depending on size, will take 1-5hp, just to run it (again all depending on the size and yes, bigger ones can take more). While 5hp may not seem like a lot, especially to FI (forced induction) cars, but that is 5hp you could potentially use while racing. Superchargers are actually always making boost. They have a bypass valve that allows the compressed air (or boosted air) to be bled out when the throttle is closed so you're not "boosting" at an idle causing much unwanted damage to your car. Supercharged cars when they start boosting you can tell because they start whining like a low power steering pump (just listen to the mustang cobras).
Turbochargers are actually load based, exhaust driven power adders. Unlike supercharging, turbos are what you could consider "free power", because you're not loosing any power by spooling your turbo to make your power. HOWEVER, just like supercharging, turbocharging comes with a cost too. LAG. Lag is what we call the time it takes for your foot to hit the floor and have the turbo start boosting to full boost. See, unlike supercharging where the boost has already been built up, and it's waiting to be used once the diverter/bypass valve closes and opens the throttle for instant power, turbos have to build up that exhaust pressure to start spinning the turbine wheel in the turbo to start your boost building process. From there it all depends on how much boost you're running as to how much lag you will have, as well as the size of your turbo. Obviously the smaller the turbo you have the quicker your spool will be, but the less amount of boost you're going to be able to run as well as the less amount of air flow you're going to be able to run. The bigger, the more air you can move and the more boost you can run, but the longer it will take for you to get that power out of it. Because of turbos delayed spool time and the bigger amount of air flow they can produce, turbos are generally best for mid to high range cars (basically "top end" or high horse power, lower torque). Hope this answers your questions guys.
4. Q;Is it worth putting dual exhaust on a stock 2.2L?
No. By putting dual exhaust on any stock motor will dramatically reduce the amount of torque the engine puts out, as it frees up way to much air flow that is used to help create the torque in the engine. Now, if you Y-pipe'd it off in the back and did dual tips, only thing you will gain from that is the looks of dual exhaust and possibly the sound enhancement. That'd be about it lol.
5. Q;What is the difference between a Wastegate (WG), and a Blow-off Valve (BOV)?
There is a lot of people who don't really know what the difference of the two, so I'd like to take this chance to clarify what these are. The Wastegate (referred to as WG from here on out) and the Blow-off Valve (referred to as BOV from here on out) are actually on 2 different sides of the turbo system. On turbos there is what is known as a hot side (exhaust side aka turbine side), and cold side (intake side aka compressor side). The WG is actually located on the turbine side, usually right on the manifold itself or on factory turbo cars, the WG is actually attached to the turbine side of the turbo itself. The WG is the part on the turbo system that actually regulates the amount of boost the turbo is set to put out. Inside the WG there is a spring with a certain amount of spring pressure, to which is what the WG is allowed to open at (ex. If the WG has a 10lb spring, the WG won't start opening until 10psi of boost is hit, thus allowing the car only 10psi of boost or so). However I won't go into a whole lot of detail about WG's functions as of right now (will later) as a lot depends on the amount of boost they allow in, I'm just going over basics right now.
Now BOV's are actually what is used to release the built up pressure in the intake pipes before the Throttle Body (TB). The BOV is the whistle or flutter of air that is usually heard when a turbo'd car shifts or lets off the accelerator. BOV's work off of spring pressure just like the WG's, and actually can be adjustable too (most greddy's are adjustable). I will go into more specifics about BOV's if someone wants to know later though.
6. Q;What is the difference between a BOV and a Diverter Valve (DV)?
Well a BOV and a DV are pretty much the exact same thing, however there is one difference. DV's re-direct the air to where it is needed (ex. the stock LNF turbo has a DV on it and when it opens just like a BOV, it puts the air right back into the compressor wheel to keep the compressor spinning for faster boost response). DV's mainly put the air right back into the intake side of the turbo before the compressor wheel thus recycling air. This is actually the same thing that a recirculating BOV does, HOWEVER, some DV's out there will have dual settings, (as in the case of Audi's and VW's), where the DV can be adjusted to only let 40% of the air it's releasing back into the intake, and the other 60% is Vented to Atmosphere (VTA). BOV's don't have this capability, they either VTA or recirculate, they are not able to do both.
7. Q;CO2 FMIC Spray? Any advantages?
Actually yes, there is quite a bit of an advantage you can gain from a CO2 FMIC spray. The purpose for a Front Mount Intercooler (FMIC), is to cool the air that is sent from the turbo to the engine (cooler air is denser thus compresses better and allows a richer fuel mixture to help add more power to the car). Now, CO2 when it is sprayed is actually freezing cold, thus when sprayed on a FMIC it "freezes" the outside of the FMIC and supercools the air that is flowing through it. Most people will see a 20-40 degree decrease in air temperatures when using a CO2 FMIC spray, thus adding MUCH more power to the car. CO2 is cheaper than most sprayed power adders, and is a lot safer as you aren't spraying it directly into your engine. Remember, colder air, better power.
8. Q;Why do some people run Methanol Injection?
Methanol Injection is a somewhat new concept for most tuners. Methanol is an additive that not only cools the air down dramatically (which is why it is 99% of the time sprayed before the FMIC) (usually cools air by 40-50 degrees), but it also adds an "alchohol" type of additive to the fuel mixture, thus allowing for more boost and more timing to be added and helps prevent detonation prematurely. Methanol injection usually adds about 40-60whp to your Forced Induction (FI) cars when tuned properly. Another thing about methanol is that it is actually VERY cheap to buy (Methanol injection has the same property make up as Windshield washer fluid (which is what many use)), and it has been proven to be VERY safe to use in the engine as by itself is not flammable and gives good power.
9. Q;E85? Good or Bad?
E85, there are pros and cons to running E85. One of the biggest cons to running E85 is the fact that it takes 30% more of E85 to run a car than it does regular fuel. So it may cost less to buy it, but you're also losing 1/3 of your tank in running it. Another con to running it is that your car HAS to be re-tuned to run it properly. Also, when running E85, you can't let the car sit without running for long periods of time (I believe 2 months is the most I've ever heard of not running without an issue), because E85 will actually gum up in your injectors and seize them up if they aren't run all the time, thus making you have to send your injectors out for a rebuild and costing you more money. And the last con to running it is that it isn't available everywhere, thus if you travel away from your area that carries it, it is more likely that you won't find another station with it within your tank mileage. Mostly bigger cities have it and the smaller towns are left high and dry without it.
There are pros to running E85 though. The chemical make up of E85 (85% ethanol obviously), makes it run a lot like alcohol type fuels, and if you were to compare E85 to any other type of fuel's octane rating it would run right about 115 octane (pretty much c16 race gas but at a fraction of the cost). E85 is SEVERELY resistant to predetonation and allows many people to not only add more boost but also add another 8-10 degrees of timing advance on the top end of their tunes (for more top end HP and better high end power). E85 also runs colder than regular fuel thus allowing to add power there just buy running it. Most people have seen 40-60whp gains by just running their same setups with nothing else changed to the setup. So yes, there are pros and cons to running E85
10. Q;Are there advantages to using the CO2 spray or Meth in NA cars, or are the costs far out weighing the gains?
Well as far as CO2 is concerned, no, that would be a very BAD idea to spray CO2 into your engine, as that would take the O2 levels out of the equation thus allowing you not to get any detonation whatsoever. As far as spraying CO2 onto lets say a CAI, you still run the risk of spraying CO2 into your engine so again, I would say no, that is a bad idea. CO2 sprays aren't feasible on NA cars.
Methanol tho, you can spray Methanol into a NA car, most high compression NA cars have this installed, but gains from it will be between 5-20hp depending on setup. So for some people it may be worth it, whereas to others it wouldn't be.
11. Q;What is the importance of having Limited Slip Differentials (LSD)?
Ah, I was waiting for this to come up. Limited Slip Differentials (as referred to as LSD from here on out), actually play a very important role in racing for those who are into road course racing/auto-cross. LSD does just what it stands for, it only allows the vehicle to slip the tires (spin the tires) so much before allowing the other side kick into action. For example, if you're taking a hard left turn, your car will lean to the right thus pulling the left tires off the ground if turned hard enough. Since the left tires are off the ground more, they have less contact area with the track thus not having as much traction and the tires will start to spin freely, as if you were doing a burn out. The LSD will actually see the free spin in the tires and lock in the right side tires to do the propelling for you, basically giving you as much traction as you can possibly get. A car that doesn't have a LSD will do those oh so famous "One Wheelie Peelies" that everyone likes to make fun of. LSD's will try to prevent as much wheel spin as possible, by shifting from your nominal drive side, to the opposite side then back to 1/2 and 1/2 on the power output (which is why cars with LSD's can do 2 wheel burnouts in a straight line). The shifting of power can go from either side to either side, so no matter what way you are turning, your LSD will give as much traction as possible to you.
12. Q;What are those things that are above the rear windows on some cars? They look like little bumps.
The "bumps" above the rear windshields of most 4 door cars especially race ones, are actually called Vortex Generators. Vortex Generators, are used (mainly with 4 doors), to help streamline the airflow across the body of the car and have less baffling (or restriction as some call it), thus allowing less drag on a car at faster speed. This allows for a more stable straight line top speed.
13. Q;What is the most important things to have before tuning?
Well, honestly not to sound like a scrooge, but if you're not doing the tuning yourself, money is the most important thing to have before tuning. However, even if you're tuning your car or not, one of the best things you can have (and this is NOT an option in FI'd cars), is a Wideband 02 Sensor and gauge. Monitoring your AFR's is the single most important thing in tuning FI'd cars. But I'll get into that another time. A few other things that would be good to have is a good check-up. Make sure you don't have any leaks of any kind, make sure your plugs are gapped right, you have enough oil and coolant, a good battery, and all the parts you want tuned for on the car before going for the tune. Also make sure you have a couple of free hours to do the tune. Most rough street tunes will take a good hour just to get the rough tune on there, and it usually takes 2-3 hours for a good clean custom to your wants tune. Now a lot of people that are tuners have self tuned their cars, and have preset tunes from their cars that they will load up on your ECU and just do the fine adjustments needed to make it work on your car and make sure the fuel trims are right where they need to be. But if you start asking for more than just their version of a "canned" tune, it will take much more time. It also helps to have a dyno setup for a later date to get the full potential out of a tune. Street tunes are nice as they can give you the best of what the tuner can give, but the dyno graphs show where there needs to be adjustments to improve the power band at certain RPM's, thus giving the tuner a better scope as to where changes need to be made to get you the most power out of your car. Just know what you want before getting the tune.
14. Q;Why are Air/Fuel Ratios (AFR's) so important?
Air/Fuel Ratios (AFR's) are the most important thing you should be monitoring on a regular basis of any FI car, or any race car. Oil pressure being the next, but back to AFR's. Your AFR's tell you a LOT more than you think about how your engine is running. It will tell you if you're running rich (basically flooding the cylinders with too much fuel which can actually decrease your performance), or running too lean (which can decrease performance). Running both too rich and too lean will actually cause spark knock (aka detonation). Spark knock is when the air/fuel mixture in the cylinder fires too soon or too late in your cylinder, which can ultimately damage your pistons/rings/rods and bearings and do a whole lot of other damage. GM actually runs their cars lean from the factory because they try to get the best MPG out of their cars for the stickers on the windows when they sell them, HOWEVER, you can actually get better MPG if tuned right. There are specific "safe" AFR limits. For the FI'd cars (as this pertains mainly to them), at an idle and cruising when no boost is present, you should be running anywhere from 15.2-15.6 AFR's. Under light boosting, you should be running around 13.3-13.5 AFR's, and under full boost, you should be running around 11.2-11.4 AFR's. Now for those that don't know how to read AFR's, the lower the number of your AFR's, the RICHER you are running, the higher, the leaner. If you are running higher than 11.8 AFR's and you are running over 16psi of boost, you will probably start seeing knock in the engine. When your knock sensor sees knock in the engine, it will actually retard the timing (pull timing) to lessen the amount of power you're trying to push to keep the engine from knocking too much and blowing up. The safe zone with knock is 0-2 degrees of knock. Anything more than that, and you're in the yellow danger zone. Thus why AFR's are so important. Hope this helps!
15. Q;Whats the difference between getting medium length headers and a regular size downpipe, versus getting long tube headers and a short downpipe?
This is actually a really good question. As most people know when they start building the performance aspects of their cars, the exhaust is one of the first things that people upgrade, and there are a TON of options out there. Now, let me just say that, your setup just like anything else should be researched and based on how you're going to be driving your vehicle. Now, with that being said, let me get to the OP's question. The difference between medium length (mid length as a lot of people call them) and long tube headers (or header for 4 cylinders and straight engines), is the actual power losses and gains. Most long tube headers are best used for a FI car (better with supercharged cars than turbo'd), as long tube (L/t from here on out) headers actually drop power at the low end of your power band, but have great top end power increases. On a N/a car, there have been gains seen anywhere from 5-30% power increases in the top end, but came at the cost to 5-10% low end power loss. HOWEVER, on FI cars, there have been anywhere from 10-40% power increases in the top end (depending on setup and additional mods obviously), and only 2-3% power loss at the low end.
Mid length headers don't flow top end as much as the L/t's but also don't sacrifice the low end power that L/t's do. Most mid length header(s) are used on aftermarket turbo manifold applications. As they flow better than the stock manifold, keep the same low end power, but add about 10-15% power on top of what they are already running on the same setup. In N/A cars, most people use Mid length because there really isn't any significant gains to be had by getting L/t's, but they also don't get the low end loss with the mid lengths, so they are still gaining a little bit of power without losing any. Now with mid length there isn't much power increase over stock on N/a cars. Most people with a fully built engine pushing it as best as they can will only see a 15% power increase with mid length headers. Again, most engine power is based off of flow, so mid length headers are a big increase over stock, but as with any N/a car, it is a lot harder for you to get big power gains with bolt ons here and there. Hope this answers your question.
16. Q;What is the difference between a 4-1 and 4-2-1 header?
Well honestly the flow is the difference, as well as how the pipes are collected. A 4-1 header actually flows a lot better than a 4-2-1 header, thus offering better top end power for boosted applications, and high HP applications. The 4-2-1 header takes the 4 cylinders, and collects cylinders 1-2 together, and 3-4 together, and a little further down it collects the two sides together. What this does is cause a little bit of turbulance in the exhaust system giving a little bit of back pressure. This allows for better low end torque, but less flow top end so you will sacrafice a little bit of HP by using it, but you will have better pulling power down low.
17. Q;Can any header be modified to be used with a turbo?
Well this is a grey area here. A lot of factory manifolds "can" be modified for a turbo setup, but it's REALLY hard (have you tried to cut, weld, or tap into cast iron?). As far as aftermarket tubular manifolds, they can be modified to allow turbos, you have to cut off the collector/flange, and reweld another collector/flange on it to fit the turbo flange you need. Yes it's possible, but it's going to require a little bit of modification, and sometimes you're better off just buying a turbo manifold or making your own, as if you try to modify one, you are going to have to do custom welding and possible pipe bending to make it work on the non turbo manifold. Another thing you have to look at is the type of metal that is being used. Obviously with a turbo you are going to need to look at how much back pressure there is going to be in the pipes, and how much more heat you'll be running and you don't want to get a weak metal and try to modify it for the turbo or you will crack your manifold and have major issues down the line. But to answer your question again, yes, they can be modified, but in my opinion, is it worth it? No.
18. Q;What is a 2 Step?
A 2 Step is the exact same thing as a WOT (Wide Open Throttle) box, and Launch Control. What it does is it takes the TPS (throttle position sensor) %, see's how far open the throttle body plate is, and will actually add or subtract fuel to keep your car running at a certain RPM, kind of like hitting the redline on your car, except at a lower RPM. People use 2 steps for the launch controller to help keep them at the ideal launching power and rpm for racing, while keeping their foot at WOT so you're not trying to rev match and concentrate on that instead of watching the lights, this also allows MUCH less, if ANY, wheel spin on take off. Most turbo cars have this ability from the factory (some have to just be adjusted by the tune of the car), and some have it right from the factory and can be used with no tuning upgrading involved (Evo 9's have this, and the Cobalt SS/TC's have this from the factory). It's there to really help for launching, once moving there is no use for the 2 Step.
19. Q;What is NLTS and how does it work?
Ah, the NLTS (No Lift To Shift). Most people consider it "Power Shifting", but when in all actuality it's not just power shifting. The NLTS is actually something that is tuned into the computer of the car for better performance (keep in mind not all cars have this). A lot of NA tuner cars will do the power shifting, which is keeping your foot at WOT when you shift, this allows the engine to speed up between shifts for a somewhat faster (but sometimes more damaging to your car) shift release (basically if gives you a slight jump forward as your clutch re-engages). However with the NLTS tune in the computer (the cobalt SS/TC's have this from the factory and other cars can be tuned to allow for this too (like almost EVERY turbo mitsubishi)), what this does is actually allows for a slight DROP in rpms while shifting when your foot is at WOT. BUT!! The way it is designed is you literally have .3 seconds to shift while in NLTS, because what this does, is when your foot is at WOT, and the computer gets the signal from the Clutch Safety Switch (otherwise known as the neutral safety switch (what is used to start your car on a 5 spd)), it tells the computer to actually reverse ignition to allow a backfire on all cylinders for 1 full firing cycle (which is where the loud POP comes from when used). What this accomplishes is the backfire adds exhaust pressure and allows your turbo to keep the boost it is currently at (with maybe a drop or 2 of boost depending on the size of your turbo) between your shifts so when you re-engage the clutch to the engine, your putting the MAX amount of power to the wheels as soon as you get done shifting. This totally NEGATES turbo lag. So as you can probably understand by reading this, the NLTS is only used on turbo cars. There would be no use for a NA, or Supercharged car to use the NLTS.