Ok , i've seen and heard independent throttle bodies and I think there kinda sweet. But if could be as dumb as a ricks badge if it doesn't do crap.
Sooo , can someone tell me what's the benifits of the ITB , what's the downflaws , how much it costs , and where to get one? Also looks like you loose alot of air lines such as the breather tube to the head anyone has install pictures or anything liek that?
Thanks , noob

 

downflaws=new word

but ya, from my research ITBs aren't worth it until you get a stroker kit, that's when they will reall show their muscle. They are very hard to tune, you'll be buying AEM EMS or something of the sort.

ITBs on stock engine should yield around 20 hp but more with more displacement. It's a whole lot to spend when the same amount of money can get you into a turbocharger.

 

ITBs are for race cars only. You're in the right forum.

The stock throttlebody/manifold design that most engines use (including S2000) lends itself well to speed density fuel injection control. This name comes from the way it calculates (actually infers) air flow from air density and engine speed (RPM).

To properly control air/fuel ratio the stock computer must first know how much air the engine is flowing. Only then can it add the proper amount of fuel flow to the air charge via the injectors.

ECU reads manifold absolute pressure (MAP) and intake air temp (IAT) from sensors on the intake manifold. These two physical properties mathematically define air density. So as air quality (IAT) and engine load (MAP) change, these sensors automatically compensate for the air density change.

The throttle position sensor (TPS) is used to trim the calculations for engine load. You want leaner fuel/air ratio under cruise/coast (low TPS reading) and richer fuel/air ratio at WOT.

Simplified, the ECU basically has a 4 dimensional lookup table with RPM, TPS, IAT, and MAP as its 4 independent axes. Each individual cell in this lookup table has a corresponding fuel injector pulse width value that provides the correct injector duty cycle. Tunable ECUs (like AEM EMS and Hondata) allow you to change these pulsewidth values.

ITBs don't have a common manifold, so there is no good spot to locate the MAP and IAT sensors. Early pure race ITBs did without both these sensors and resorted to n-alpha control. N=rpm alpha=TPS. Kind of like early carbs, easy to tune for full power, harder to tune for drivability.

The newer ITB conversion kits usually have some small chamber connected to each individual throttle via small flex tubing, that allows a spot to connect the MAP and IAT sensors. This makeshift chamber makes it impossible to accurately sense average MAP of 4 cylinders and IAT. Therefore the system's ability to automatically compensate for changes in these properties are greatly compromised. So you still end up relying heavily on RPM and throttle position to tune.

 

I doubt you can get 20 hp out of ITBs.

You must run a standalone engine management (ie. AEM EMS). If you tune a car with a single throttle body and EMS and then do the same car with ITBs, you'll see a very small hp gain and generally that gain is just an issue of tuning the length and diameter of the intake runners... so you could really do the same thing with a single throttle body and a custom intake manifold.

The main advantages of itb's are that you can get faster throttle response (since there's no intake manifold plenum to cause a lag in throttle response) and you can more closely fine tune the flow/response for each cylinder.

Downsides... as I already said, you need to do an aftermarket engine management system to get the car to even run with these and even then it'll take some work. Overall power gain will be small and you will usually get a loss somewhere in your powercurve to offset whatever gain you get in that other part of the curve. Usually, you don't use an air filter with these and that can be really bad for the engine, especially if you go off into dirt (although you can rig up a filter). Expensive... etc. etc.

 

Please don't disrespect Rick's Accessories and use the spell check


ITB's are for race cars.

 

Here's what they can look like if you decide to waste your money with no HP gain

 

Hey where did you get the little filter thingy for the crankcase vent?? And daym you departed with more than a fistful of $$$ on that engine.

On the topic, my understanding is that ITBs are mainly for drag racing engine where you run WOT start to finish and as a result don't need to worry about TPS (always wide open) and where you don't want the sudden pressure drop in the plenum of the intake manifold so you can get maximum air into the cylinder immediately. When you run an engine in binary mode like that the tuning is simpler because you eliminate the variables.

On a track or even street car getting a ITB to be not only efficient but even function reasonably well is a very difficult if not impossible task. The plenum of the intake creates a consistent air chamber which allows for a simple fuel map in the ECU. The ECU doesn't have a lot of computational power and few sensor inputs. A fully optimized ITB setup would require better sensor data and fuel injection data which was calculated on the fly.

Those quad trumpets sure look sweet and get my highest vote on the bling scale. I think that with enough money you could get 20HP out of an ITB setup at some part of the power curve but not across the board. The F20/2C suffers from the problem of being properly designed at the factory for performance. Your average street car is tuned for noise/polution control/fuel economy at the cost of performance and that is why you can make big gains with bolt ons on a B or K series engine. You aren't making power you are just unlocking it by retuning it toward performance.

It's a huge expense for little usable gain IMHO. You are far better off just forcing more air into the engine using a turbine. It's simpler, more idiot proof and ultimately less expensive.

 

That's an insanely beutiful engine. $$$$ I see ITBs, a turbo, and nitrous. Is there a solid rocket booster bolted to the top of the car too?! How much hp does that engine make?!

Cthree - I think you're thinking of carbs... A lot of drag racers ditch the whole fuel injection system and all of its electronics and just use 4 carbs instead for exactly the reasons you pointed out. If the engine always runs between say 8-10k rpms at WOT, there's not really any reason for all the complexity of a fuel injection system and computers. 4 needle valves are much easier to tune.