dual throttles

my friend has a 98 civic ex dohc vtec and we wanted to 'add' another throttle to it. now how would i go along doing this? we're gonna put some kind of divider in the intake manifold so one throttle goes to 2 cylinders and the other throttle to the other 2 cylinders. of course the fuel injection will be upgraded and a custom intake manifold. i've seen something like this done before on a ford focus, and i was wondering how i would go through this process of creating it?

my friend has a 98 civic ex dohc vtec and we wanted to 'add' another throttle to it. now how would i go along doing this? we're gonna put some kind of divider in the intake manifold so one throttle goes to 2 cylinders and the other throttle to the other 2 cylinders. of course the fuel injection will be upgraded and a custom intake manifold. i've seen something like this done before on a ford focus, and i was wondering how i would go through this process of creating it?
Why would you do it?

Might as well go for four itb's.

Why would you do it?

put more air in the engine. it's not forced induction. unlike turbos or s/c which need a source of power. 2 air intake into 2 throttles will result in more air.


Might as well go for four itb's.

itb's?

Individual Throttle Bodies.

i've thought of that, making 2 smaller intake manifolds and putting a throttle on each. but what else would i need to do to make it work?

If you think the throttle body is a restriction in the intake (and it probably isn't) why not just get/build a bigger one?

the biggest throttle out there is someting like 80mm, *correct me if i'm wrong*, 2 air intakes each going to a throttle body-has nothing to do w/ resriction, it's just getting more air in there.

Actually, 2 TB's will ease up the restriction (if thats where the air is being restricted) because less air will have to flow through each TB in order to provide the same amount of air as through a single throttle body. But chances are, it wont really matter for a stock motor (by stock i mean more than a K&N and a high flow axle-back system).

Actually, 2 TB's will ease up the restriction (if thats where the air is being restricted) because less air will have to flow through each TB in order to provide the same amount of air as through a single throttle body. But chances are, it wont really matter for a stock motor (by stock i mean more than a K&N and a high flow axle-back system).
I still don't see how his engine isn't getting enough air.

<has nothing to do w/ resriction, it's just getting more air in there.>
How would you get more air than you need? Either you don't have enough air because of a restriction in the intake, or you have enough (excluding cases with really bad intake tuning).

Your absolutely right, if your engine is already getting enough air, making the intake system less restrictive doesn't really matter.

ok, yea you're right, the engine is getting enough air, the normal amount a stock vtec would take in. but what i'm looking for is more air. it's like the forced induction thing-more air mixed w/ the right ratio of fuel will create more power and THAT'S what i'm looking for, more power. having an intake and a throttle will give me a set amount of air. by adding another throttle, air intake will double-theoretically. all the while, the car is technically naturally aspirated.

It doesn't work like that. If the engine is getting all the air it can process then any more air you give it won't do anything. What the dual throttle body system could do, if designed properly, is maybe give better throttle response. Think about it, if this thing worked it would have been done already.

It doesn't work like that. If the engine is getting all the air it can process then any more air you give it won't do anything. What the dual throttle body system could do, if designed properly, is maybe give better throttle response. Think about it, if this thing worked it would have been done already.
Right. The engine only pulls in air because the pressure inside the cylinder is lower than in the runners (then manifold/intake/ambient air), because of the properties of gases. If the pressure inside the cylinder was higher than 1 atm (what boost is), it would want to go back out the intake.

ah alright, icic. well thanx for your explanations.

Think about it, if this thing worked it would have been done already.

this kinda of thing has already been done before on a ford focus.

And what were the results?

well it's the fastest all motor focus, running 13.19 @ 102.2. i read an article about it in 'hot compacts and imports' back in may of '03. they had 2 throttle but only 1 intake (my plan was 2 intakes, but whatever). 207 hp at 8200rpm. i have the article so i'll scan the pics of the intake manifold w/ the throttles. hopefully i'll get it up another day.

OK that's impressive. I'm just wondering how much it would cost to do this thing though. I mean, would it be much cheaper than going for an off-the-shelf ITB setup like TWM or Toda? I guess you probably want to be original and do this thing which is cool...

I am currently building a Dual TB setup on my '98 mitsubishi mirage. There is a company out of Australia that makes a kit for the mirage but it far too expensive for me. So im building my own. Some problems i think one might run into are with the MAP VS MAF/MAS sensors. The MAP simply measures the mainfold pressure from within the manifold to determine the amount of air being taken in. this is how it is in my car and will only require a piggy back fuel computer and possibly a FPR to tune it. While the MAF/MAS actually measures the flow of air on the intake tube. If you were to add another tb on a car equiped with a maf sensor the CPU would be getting no info on the amount of air being taken in by the second TB. Some have said before that this might require a stand alone ecu to tune with the MAF sensor. Im not 100% sure about this. Anyway i hope my ramblings helped add to the topic...or added to the confusion, who knows.

Here is a link to a pic of similar system made by RPW out of australia on a hyundai http://www.rpw.com.au/Photos/Twin%20Throttle%20Body/Hyundaitwinbig.jpg

OK that's impressive. I'm just wondering how much it would cost to do this thing though. I mean, would it be much cheaper than going for an off-the-shelf ITB setup like TWM or Toda? I guess you probably want to be original and do this thing which is cool...

idk, idk which would be cheaper or more effeicent. that's y i'm asking.

drinkthesand, those are all questions that i have too, not sure how it would work w/ the MAF sensor for 2 intakes, where on the focus that i saw had 1 intake. but that setup shown is really nice, and what i'm looking for-just didn't know if it was possible or what problems i would run into if it could be done.

Just a bit o' info. I know of one case off hand of the dual throttle body thing being done. It's on my favorite car, in fact. Check out the mechanics of the 90-96 Nissan 300ZX (VG30DETT). Now...4-cylinder engines are usually either inline or flat 4s. The civic is an inline four. In that case, two trottle bodies is quite pointless...here's why...the engine in the 300ZX is a V-6...2 banks of 3 cylinders. What the designers were going for with the design of this (gloriously brilliant) engine was 2 "individual" banks of 3 cylinders...each bank has it's own intake, throttle body, bank of cylinders, and exhaust, along with each bank's very own turbo and intercooler....only in the turbo model, of course. The result: an engine that is so insanely willing to rev that it almost reads your mind. I've had the opportunity to drive 2 normally aspirated models and play around revving the engine in another normally aspirated one. The first time I stabbed the gas pedal in neutral, I actually said aloud "holy shit". The turbo models have a little turbo lag, of course, but very little...damn thing spools at around 2300 rpm....reeeeeeeeeally low considering the redline of over 6000rpm.

Sorry....kinda felt like rambling. Want more Z info, lemme know. Really cool shit.

Been reading this with interest, and it seems everyone has forgotten something very basic.

There is more to getting more air into an engine that just makeing a bigger intake system.
You also have to have valve size, lift and duration to cope with it, as well as an exhaust system that can let it all out again.

The B16a has a VERY efficant intake and exhaust already, the stock intake (including single TB) and exhaust manifold is quite capable of flowing well over 300hp.
Adding another throttle body will do nothing to increase the hp, it might help with throttle response, but its already a very responsive engine and the added complication wouldn't be worth it.

If you really want more hp, then some new cams and a Hondata ECU will take you anywhere from 200-300hp depending on how much money you have, and how wild you want the engine.

Agree 100%. The ultimate limit to the amount of air an engine can process comes from the flow capability of the cylinder head, the total inlet valve area being the biggest factor to determine an engine's ultimate power potential.

Didn't the '98 EX only come with the 1.6 SOHC VTEC in the US?

the guy he bought the car from dropped a 1.6L dohc vtec in there, so idk what was orginally in there. and i completey understand what you're saying pringles, i'm not arguing it anymore-thanx for your help.

Agree 100%. The ultimate limit to the amount of air an engine can process comes from the flow capability of the cylinder head, the total inlet valve area being the biggest factor to determine an engine's ultimate power potential.

Didn't the '98 EX only come with the 1.6 SOHC VTEC in the US?
The power potential comes from volumetric efficiency, not inlet valve area. Although I agree that the larger the area, the less power is required to suck in air, a well designed intake port can more than overcome that.