Toying with the idea of custom ITBs and if you think about it a nice pair of DCOE's seem like they'd in the long run be easier and cheaper to tune / get working on a nonvtec bseries. I've seen some threads mentioning it, but I'm curious why people stay away from them. I'm guessing its primarily because its not very high-tech so people rather pay the $3k min to get ITB's & standalone systems to run on the street, but I don't see why a good set of carbs wouldn't yield as good results.


[Modified by teg92, 4:24 PM 12/13/2002]

 

that can yield very good results. I know many VW's that run that. But carbs are so outdated, most people dont know how to use them, or most importantly, tune them........daily, more annoying then any other thing, is tuning them to perfect results, and then having alot damper hotter air in a week and it runs like ****. EFI is more of a set it and forget it type deal.

 

If you learn how to tune a carb, you can make HP very easily and as you upgrade you engine it is easy to change chokes to keep it breathing. The drawback, you suffer in driveability as you are generally tuning for best power.

I run DCOE 45 Webers on race motors - I find them easy to tune and they deliver great power. On theother hand - I find Mikunis much more finicky...

Kirk

 

I think it's easier to make a few key strokes in your laptop than to change jets, power valves, venturi bodies and accelerator pump cams in a carb that was first designed over a century ago. What do you think?

 

fuel atomization is so much better with carbs though. I would love to run them if it didnt get so cold here. ITB's are cool too, but ya, expensive.

 

for racing situations carbs work well.
but for daily drivability, nothing beats the ability of an ECU to compensate for
environmental conditions

 

Fair enough, while on the topic...

What would be the problems with making a custom ITB setup with big enough TB's off a bike and having a custom manifold made to bolt up to the ITBs? Once everything is bolted up, the only things that you have worry about is the TPS, IAV sensor, kiss your IAC goodbye... what else?

 

If you search there were a few posts where other ht members were looking into trying this with 929rr itb's. All the sensors are supposed to be there and even plug right in since its a honda part.

 

Ease and accuracy of tuning with an ECU outweigh the simplicity of carbs.

 

Oh well, thanks for the tips guys, I will now be building my own custom ITB's... I will keep you posted.

 

I tried searching, couldnt find the thread...can someone guide me in the right direction, im interested in this...

 

I find this one hard to believe. Carbs are notorious for just sending a stream of fuel into the intake rather than a mist. But back to the original question. One of the BIG problems with carbs is that they can only be tuned to supply optimal fuel at a single point in the power curve. At all other points, the fuel ratio will be off. Fuel injection allows the possibility of tuning an engine for the optimal fuel ratio at ALL POINTS. And as the other guy said, it is easier to hook up a laptop and punch keys than to tear down carbs and change jets. Furthermore, alot of the engine management systems out there (Hondata, AEM, etc.) allow for multiple fuel maps. This allows you to run a race program when racing and easily change to a street program for better fuel economy during daily driving.

Another problem with carbs is ignition control. If you use a stock distributer or some other high tech ignition system, you need to use the ECU (or other management system) to control ignition advance. One possibility is to go with an old-school mechanical advance distributer. But like carbs, these cannot be set up for an ideal advance curve over the entire RPM range. Furthremore, I don't even know if they are available for newer D, B, or H-series Honda motors. The other is to use an ECU and have dummy loads for the injectors. But this is plain stupid.

The bottom line: Whether Dr. Atkins really has something going when it comes to avoiding carbs while dieting is still controversial. But if his book was about cars, then he had it all right.


[Modified by StorminMatt, 1:43 AM 12/18/2002]

 

fuel atomization is better with carbs, PERIOD.

The stream you talk about is the accelertor pump squirt. This makes up for the throttle opening low vacuum issue in which the venturi effect will not suck enough fuel. ALL EFI systems will lean out, even if ever so shortly when this happens.

A certain FAST SOHC person stated you need 3 FEET from the injector to the cylinder for fuel to atomize properly.

Carbs can be picky, EFI best for daily driving, not very sensitive to temp/altitude changes like carbs.

OG V8 info.......
Holleys suck for daily driving, RULE for WOT racing.
Carters are best compromise of both worlds.
Quadajets work great, PITA to work on.

Edelbrock bought the rights from Carter.


[Modified by Mista Bone, 6:26 AM 12/18/2002]

 

It was a good thread...https://honda-tech.com/zerothread?id=303926&page=1.

 

Maybe you know something I don't, but everything I know about carburettors and fuel injection is, fuel injection has much better atomisation. (I'm not talking about throttle body injection)

The fuel is injected directly onto the valve, which, when the engine is warm, causes the fuel to evaporate instantly, whereas a carburettor sends a stream of fuel out, which mixes with the air in big droplets. (in comparison)

 

Fuel can be atomized in several ways with fuel injection. Squirting a high-speed stream at the intake valve is one way. The DOHC, 32 valve V8 in the Corvette ZR-1 (LT-5) atomizes fuel in this way. But in most EFI systems (including Hondas), the injector itself atomizes the fuel. A typical Honda injector is of the pintle style. If this type of injector, the pintle valve seals in a taper, blocking the flow unless the injector is opened. When it is, the pintle lifts off its taper and lest fuel flow past. After plowing through the taper, the fuel flows through another reverse taper. The pintle itself has a conical end section that matches this reverse taper. But there is a small gap between this conical section and the reverse taper. As the fuel flows through this gap at high speed from the fuel pressure, it is broken up into fine droplets. The conical gap also establishes the conical spray pattern typical of pintle style injectors.

Carbs, on the other hand, intorduce fuel into the airflow by by means of the Bernoulli effect. Specifically, when air accelerates flowing through the Venturi, its pressure is lowered below atmospheric. This causes fuel to be sucked from the float bowl through the main jet and into the airflow. Since this pressure difference is so much lower that the fuel pressure in an EFI system, te fuel is going to come in MUCH slower. This lower speed does not break up the fuel into droplets as well as the high speed and pressure in an injector. Better fuel atomization (and the resulting better emissions) are one of the BIG reasons why automakers abandoned carbs in favor of fuel injection.


[Modified by StorminMatt, 2:36 AM 12/19/2002]

 

Matt is right, for the general public. Emissions is the main issue.

But for all out WOT, carbs will always win.

 

Emissions be damned, atomization is the way to superior power as well. And in that vein, cosnidering not just a specific throttle angle and small RPM range, EFI is superior to carbeurated setups... end of story. While a very well setup carb system can certainly equal the peak power output of an equally well setup EFI system, the EFI will show a significant advantage across the RPM range, especially at small throttle angles and with low vacuum. Precisely the setup that traditionally generates high amounts of engine power at high RPM (read: large ports, short runners, big cams and low idle vacuum) kills low RPM response and power with a carb setup, but is at least properly managable with EFI. This is the primary reason why engines like the F20C in the S2000 can be mass produced and are fit for passenger car consumption, even though they don't get up on cam untill well north of 6000 RPM. Yet another example would be the new rotary motor, which can now function the way it was originally designed (aka side port exhaust) simply because of the added precision of modern EFI.

And one thing that hasn't been mentioned yet is the added freedom of intake manifold design afforded by dry flow setups. Wet flow intake manifolds present the engineer with quite a challenge if he wishes to tune the resonance of the system, especially at multiple RPM points, since he has to worry about fuel flow through the manifold as well as airflow. Also, let's realize that EFI has yet to reach it's ultimate setup in normal production engines, which is direct chamber injection. Audi has already displayed this superiority over more traditional means in Le Mans racing, where they were able to generate power levels better or on par with any comparable setup while reliably running Lambda readings well above what was possible with any other method of fueling (on the order of up to 1.3 at WOT).

 

but this applies to daily driven cars, EFI ROCKS!

On race cars that don't see "small throttle angles"....... at WOT carbs will always rule.

OK, anyone try to prove Bisi E. wrong? 10.77 @ 124 mph, 1.5L on carbs.

 

Ya Bisi has tried, 30% more power with carbs than ITB's.

To get the same fuel atomization out of FI the injector needs to be mounted 3 feet from the CC, now find a IM that has 3' long runners and you will get as good atomization. It has been proven, dynoed, tested no ifs ands or butts, yes its old, but it works!

for the people who believe in carb power (Mista Bone)