Big Bore Throttle Body. A worthy mod? Which one is best?

[BD]

Re: Reality check

So now I ask you, what proof do you have that the stock intake system is not restrictive at all on a motor with all the basic NA mods - or are you just posting pure speculation?

There is not a single Japanese vender out there doesn't have a ECU upgrade when the BTB is offered, does that make and sense to you?

A quote for a SoS does not make the statement valid (not trying to rain on Chris's parade this time) but the study subject is "singular," therefore you will definitely need more than 1 to have a more clear picture.

In Japan, some ITB equipped NSX can get up to 400hp to the crank, but requires at lot more than just installation of ITB, a stroker kit is required. Without the stroker kit, the number appears to be around 320-ish HP to the crank. Even with that, it put the HP rating of the DOHC VTEC engine back to its potential even without ITB - 106-ish HP per liter. Honda has already achieved numbers even greater than that on the S2k.

For example, the TODA 3.5 package allows the RPM to reach 9500, that extra 1500 hundred RPM can easily translate to extra 30 hp. You can't achieve that with a stock NA motor even with just ITB.

Cars with TODA stroker kit with ITB and properly tuned ECU will not give the driver what he needs for daily street use. The application is strictly track purposed, the lower RPM power/torque curve is really really weak.

There is a very simple way to determine if the stock TB & manifold are restrictive - do cars with ITBs make more power? If so, the answer is unequivocally yes; if not, then no. Its that simple.

My understanding, from speaking with Japanese nsx owners with ITBs on their cars, is that they (claim to) pick up anywhere from 15-25 hp on the dyno, depending on the other external modifications. Cams seem to be a big factor. I have not dyno tested a set of ITBs on a street car myself.

That said, I personally have no doubt that the intake system (as a whole) is less than ideal. It is designed based on a set of compromises that are not the same trade-offs desired by someone who's primary goal is more power. That does not make the oem design 'bad,' it is just a reality of production cars.

Regardless, you can compare BTB to ITB, they are completely different. People who have done ITB also have done pertty much every thing else that will benefit from ITB.

Think about it. M3/M5/M6 all use ITB, but they BMW did not offer any better HP output than what Honda can with standard TB.

 

[David]

This is exactly why I don't bother posting here very much. My original post was simple and direct. I made a statement about ITBs as a litmus test regarding the stock intake system; I stand by it. I also stated my beliefs regarding the stock intake system based on my personal experience with it in the context of almost three decades of building motors and making cars go faster. If you want to call that part 'speculation' then go ahead.

I am talking about NA motors with stock internals only.

Good for you. Meanwhile, I am talking about motors built by people who are serious about NA power. Unfortunately, when I post here, I often forget the technical level of this forum and assume a certain level of expertise.

I have no idea why you are discussing ITBs as if they are the only mod someone would put on their motor. That presumption, in and of itself, makes me wonder how much you really understand about the subject. Of course, when you are building a motor, ITBs are one of the last modifications you would make and are only a reasonable option after you have done pretty much everything else to make the motor breath/run better. Talking about using them on a stock or near stock motor is just silly - what is the point, other than to be argumentative?

Without the stroker kit, the number appears to be around 320-ish HP to the crank.

If that is true, they need some help. I know two tuners who have made that power at the wheels on a 3.2L with bolt-ons, management, a mild port and cams.

Regardless, you can (sic) compare BTB to ITB, they are completely different.

Read. I didn't compare them - I said if ITBs increase power, then the stock intake system was a restriction. Its that simple.

It is obvious that you guys do not want to believe that the stock intake is a restriction (in spite of the very obvious design/engineering issues regarding the plenum size and overall height) and nothing I say will change your mind. However, there are a people on here that are open to new information so I will add this before I go:

Put a vacuum gauge on an intake from an NSX with the full compliment of normal NA upgrades:

- full exhaust
- management
- cams

Now, wind it out, look at the vacuum gauge and see for yourself if the intake is a restriction. I know the answer, because I have done it on 3L cars, 3.2L cars and a 3.6L car.

Y'all have a nice day.

 

[BD]

Therefore, back to the topic of this thread.

Dave, do you think BBT by it self is a benefit when it is installed without additional mods?

 

[greenberet]

Put a vacuum gauge on an intake from an NSX with the full compliment of normal NA upgrades:

- full exhaust
- management
- cams

Now, wind it out, look at the vacuum gauge and see for yourself if the intake is a restriction. I know the answer, because I have done it on 3L cars, 3.2L cars and a 3.6L car.

Interesting point - check the pressure in the intake manifold with a vacuum gauge at wide open throttle at various engine speeds. If the manifold pressure drops as the rpm increase, then something in the intake is restricting the amount of air getting into the engine and therefore the amount of horsepower that can be produced. If you can snake the gauge into the passenger compartment, you could do that test on the road.

You could do a before/after for a BBTB, airbox, air filter, etc. and see what, if anything, reduces the amount of vacuum in the intake manifold. Hmm, I wonder how much a vacuum gauge costs...

 

[UnhuZ]

i agree with David... there are things restrictive in the complete OEM intake line...and inside the intake manifold, those little 6 TBs with all their mechanisms are messing with air flow, which should be as smooth as it can.

and when is said that you cannot compare a civic with NSX when you talk about intake gains...i wonder:

- both are NA
- both do 8000rpm maximum (B16A)
- 3000cc engine vs 1600cc engine sucking air
- intake vaves on NSX are bigger than on civic
- both have about the same TB opening size

now...with all this...can someone explain me how a civic can have more gains when we mess with the intake??? i mean...one engine needs a lot more air than the other, and this air have to pass by the same opening...

in a NA motor, it's the engine that sucks air...and with a small opening, the engine may not suck the maximum air it can...OEM it's not the maximum a engine can do...as others said, there are compromises a Maker have to do...

the NSX has a NA motor, and there are rules that apply to all NA engines...the gains may be different...but they still apply.

 

[96cxt]

Uh, ITBs are only necessary or effective when the engine is using enough air (e.g. FI/stroker) to create a bottleneck at the already-bored-out TB or IM. You don't really think slapping ITBs on a stock motor is going to increase power do you?

Obviously you don't understand the fundamentals of car modification nor do you have a grasp on how intake and exhaust systems work. As I said, what works on other cars doesn't always work on NSXs.

Thinking "outside the box" has nothing to do with it. Things like VTEC are not "improvements". They are innovations that are implemented. Your statement that the NSX's horsepower can't be increased because it isn't perfect as Honda updated and upgraded the car or that it requires maintenance is absurd. We are talking about the car that you have sitting in your driveway. That's the palate you have to work with. I'm not clear on what Honda has to do with anything at this point. Honda effectively overbuilt the intake system, underbuilt the NA1 headers and exhaust system and provided a rocking universal tune that can't really be consistently improved upon.

People have been monkeying with NSXs for over 17 years. It's pretty clear by now what works and what doesn't. Headers for an NA1 work. Headers for an NA2 don't, etc. There are ways to get more power from an NA NSX but modifying the intake system is not the way to go about it. I am not making this up out of thin air. Many, many people who have forgotten more about tuning that I will ever know have been screwing around with every possible method of power extraction and have consistently come up short. Again, there are things that work and things that don't.

The only things that one can do to measurably increase power in an NA NA1 NSX are headers, exhaust and cams. The combination of NA2 valves/springs, ECU mods, BBTB, IM porting and more aggressive tuning--all together--might get the average NSX 5-15 hp. All of those mods combined get far less power than headers alone! It's just simply not there.

So do what you want to do. It seems that you have convinced yourself that porting your intake manifold and having a BBTB will unlock the door to NA power (because it may have done so on a Civic, etc.) But please don't irresponsibly state that this will create gains unless you have consistent, repeatable proof that it does. Suckers are born every minute and the truth is that there is no evidence to suggest that the BBTB or IM porting will produce any consistently measurable power gains on NA cars. If you think it's just not possible that the intake system and tuning cannot be improved upon then go spend the thousands to modify them and show us some before and after dynos at each stage. I'll be using those thousands to get one step closer to a supercharger.

First of: How much horse power are you talking about gaining? The BBTB and manifold porting is not going to gain you anything over 10 hp if that. Again the dyno can prove this, but I hope you don't alway rely on dyno number. It's not always about making the dyno numbers. Two car can make the same power yet on the street/track one is faster than the other.
Like I said before you have a chain of mods that go hand in hand and if they work well with each other you will see performance gains.

If you are trying to gain more than 50 hp on the NSX you have to go with nos or FI.

Having this discussion with you is pointless. NSX has an internal combustion engine that is the same as all the cars you'll find on the street. It requires AIR and FUEL to make power. The civic is the same concept.
But since you think the NSX is a perfect car built and is hevenly sent.

I have been working on car since late 80s and have much experience, I don't just pull shit out of my ass or go according to what other say. I have actually done much dyno testing getting different result with the same upgrade on different car. So just cause SOS (sorry SOS) says that you will gain 5- 10whp doesn't mean you will. There are so many different factors involved.

I'm done here.
Have a great day.

Rahim

 

[Mac Attack]

Didn't anybody click on this link Very basic and easy to understand. Same information David is trying to convey (but with pictures). Stop all this hypothetical bench racing and get out and take some measurements. It's certainly more productive than bickering on the internet.

This will determine the bottleneck: I like their articles - good reading.
http://www.autospeed.com/cms/article.html?&A=0629

Who's willing to try?

 

[greenberet]

Didn't anybody click on this link Very basic and easy to understand. Same information David is trying to convey (but with pictures). Stop all this hypothetical bench racing and get out and take some measurements.

Excellent article. Measuring the pressure drop as described would prove whether there is a restriction in an NSXs intake system and would show where and how large it is. Testing like that would very inexpensively show whether the current throttle body is a restriction, answering the question with hard facts, not conjecture.

 

[Daedalus]

Didn't anybody click on this link

Not the first time it has been posted.

If you want to quantify the restriction of the stock TB, the way to do it is to take a vacuum reading immediately before and immediately after the TB at steady state WOT.

 

[AR]

Well I am not convince is worthless on NA so I'll turn it up to 11! :biggrin:

Cheers,

Ary

 

[markc]

Measuring the pressure drop as described would prove whether there is a restriction in an NSXs intake system and would show where and how large it is. Testing like that would very inexpensively show whether the current throttle body is a restriction, answering the question with hard facts, not conjecture.

W.R.T the above, at a recent dyno day in the UK (using Rototest hub dyno equipment) we saw pressure drop during the pulls. Pressure monitors were placed in the inlet grill and another tee'd off the inlet manifold ie either side of the inlet scoop/airbox/TB.

We ran 10 cars (a fairly even split of NA1 and NA2 cars), all were NA, some had I/E/H mods. The pressure drop we measured was consistant across most (I didn't see all of the plots), if not all of the cars.

It was suggested by the workshop that there was therefore a restriction somewhere in the inlet path. As the cars fitted with the Cantrell/Procar Scoop & Airbox showed the same pressure drop the thought was that the TB and/or the VVIS system were to blame.

Attached is my own data from the Rototest hub dyno and alink to the Rototest website for anyone unfamiliar with their system... http://www.rototest.com/rototest-dynamometer.php

The pressure measurement, on my graph, is the blue line that starts 2nd from top on the left of the graph and finishes 2nd from bottom on the right of the graph.

The plan is for one of the attendees to upgrade to a BBTB and return to the same shop for a comparison run.

It would certainly be interesting to understand what causes this pressure drop even if curing it only releases a little more HP.

Cheers

Mark

 

[96cxt]

W.R.T the above, at a recent dyno day in the UK (using Rototest hub dyno equipment) we saw pressure drop during the pulls. Pressure monitors were placed in the inlet grill and another tee'd off the inlet manifold ie either side of the inlet scoop/airbox/TB.

We ran 10 cars (a fairly even split of NA1 and NA2 cars), all were NA, some had I/E/H mods. The pressure drop we measured was consistant across most (I didn't see all of the plots), if not all of the cars.

It was suggested by the workshop that there was therefore a restriction somewhere in the inlet path. As the cars fitted with the Cantrell/Procar Scoop & Airbox showed the same pressure drop the thought was that the TB and/or the VVIS system were to blame.

Attached is my own data from the Rototest hub dyno and alink to the Rototest website for anyone unfamiliar with their system... http://www.rototest.com/rototest-dynamometer.php

The pressure measurement, on my graph, is the blue line that starts 2nd from top on the left of the graph and finishes 2nd from bottom on the right of the graph.

The plan is for one of the attendees to upgrade to a BBTB and return to the same shop for a comparison run.

It would certainly be interesting to understand what causes this pressure drop even if curing it only releases a little more HP.

Cheers

Mark

:smile: awesome test man. Update as when you get the results.
thanks for sharing.

 

[AR]

Mark, still gutted I could not make that one. I wonder what the results would be like without the ribbed rubber connector???

 

[Tanto2]

First, David, don't go away, just ignore the paper mechanics like Vancehu(god knows its hard). I am coming in at the end of this, but taking vacuum accross the body is not useful IMO. As the resistance here goes down, you are already into a territory where you are losing way too much low end as you are changing the VELOCITY significantly after the TB. Intake velocity, especially with our intake could be it's own very long thread. The easy the way to look at this is: larger TB moves the power band up, smaller moves it down. The engine designer strikes a compromise. The HP under the entire curve doesn't change much either way. Peak HP at the highest revs will go up nicely, but low end will go down badly. If we had torque to spare, then we would want to sacrifice a bit for the top end, but we don't. It's not really germain, but bigger TB's often make sucking noises that I can't stand on a street car, although many think it's cool. My bottom line for me is, if you are increasing to 3.5, look hard at a larger TB, but not with an NA 32. BTW Shad at driving ambition has dynod most all this stuff so many times, it really pays to run this stuff by him if you can. I do recall him saying that on the early Realtime cars which were about 345 flywheel, they did take vacuum on the intake TRACK and there was no significant drop. They would have addressed it if there was (Uni-filter of course).

 

[markc]

Hi Tanto,

Are you saying that the pressure drop we measured is 1) normal and 2) not significant?
I had thought that it (this measured effect) might just be due to where they tee'd into the inlet manifold but wasn't sure? Has anyone else measured a similar pressure drop or indeed measured either side of the TB and not recorded a pressure drop?

As I understand it, you want the highest possible air velocity arriving at the inlet ports (of the cylinder head itself) at every point in the rev range? The object of the VVIS system (or any variable induction system) is to maximise this velocity over a wider rev range?
So, in a single TB system like the NSX, does the air velocity through the TB itself, given that it's so far upstream of the inlet ports, really move the torque/power up or down the rev range rather than just allow the engine to, potentially, make more at all points?
I can see how ITB's might move torque/power up or down the rev range, especially if each one had it's tuneable induction system.

I'm just trying to understand if the effect we recorded is a real one or an anomolly of the way we measured it, and if addressing it would release a few more HP.

AR, I don't think the guys with the Procar airbox's fitted had the stock ribbed rubber connector and they saw the same pressure drop so eliminating it wouldn't appear to help.

Mark

 

[AR]

AR, I don't think the guys with the Procar airbox's fitted had the stock ribbed rubber connector and they saw the same pressure drop so eliminating it wouldn't appear to help.

Mark

AFAIK Paul and Luke have the OEM connector.

Cheers,

Ary

 

[Daedalus]

The pressure measurement, on my graph, is the blue line that starts 2nd from top on the left of the graph and finishes 2nd from bottom on the right of the graph.

The line is the difference between the 2 pressure monitors during a WOT run? Maybe I'm confused by the scale, which shows the line starting off at around 1 bar.

 

[BD]

First, David, don't go away, just ignore the paper mechanics like Vancehu(god knows its hard). I am coming in at the end of this, but taking vacuum accross the body is not useful IMO. As the resistance here goes down, you are already into a territory where you are losing way too much low end as you are changing the VELOCITY significantly after the TB. Intake velocity, especially with our intake could be it's own very long thread. The easy the way to look at this is: larger TB moves the power band up, smaller moves it down. The engine designer strikes a compromise. The HP under the entire curve doesn't change much either way. Peak HP at the highest revs will go up nicely, but low end will go down badly. If we had torque to spare, then we would want to sacrifice a bit for the top end, but we don't. It's not really germain, but bigger TB's often make sucking noises that I can't stand on a street car, although many think it's cool. My bottom line for me is, if you are increasing to 3.5, look hard at a larger TB, but not with an NA 32. BTW Shad at driving ambition has dynod most all this stuff so many times, it really pays to run this stuff by him if you can. I do recall him saying that on the early Realtime cars which were about 345 flywheel, they did take vacuum on the intake TRACK and there was no significant drop. They would have addressed it if there was (Uni-filter of course).

So every thing you said basically in accordance with a paper mechanic name Vance Hu? :biggrin: :wink: :wink: :wink:

There is an interesting BTB used commonly in Japan, Infinity Q45's throttle body mounted with special bracket. Even with that, the HP increase is not proven given the fact if the Engine is left completely stock. I don't believe any of the NSX venders in Japan will do that mods without additional engine tuning.. That TB is a lot larger than any NSX BTB offered in the current market and the price is not that much more. Used Q45 TB was easy to find cheap.

I do not know any one who has done the BTB or the Q45 TB without changing the I/H/E, which means the data is mixed in with the final result.

The bottleneck on a efficient high power stock engine system usually comes from the exhaust side, not intake side, unless you do FI or altered the engine such as a stroker kit, there is really no point to just doing the BTB if you keeping every thing in stock (IHE).

The nature of a well designed engine such as the Honda DOHC VTEC, Toyota's VVTi, modern Ferrari and Porsche Engines will likely not having bottle neck problems on the intake side.

Or

How about people who had their ECU tuned and gained additional 10/20 HP with higher fuel and air mixture, wouldn't you think the OEM bottleneck would have prevented that from happening, since it HAS to drawing more air?

There is another "some what" of a good way to find out this through a FI application:
Does any one who has CTSC or other supercharger system had the BTB done to see if there are any dyno date showing before and after BTB? If there aren't any major difference through that application, what makes people think BTB will make any difference under NA application?

I personally don't believe every performance mods offered in the NSX market will achieve any thing, but we all want some thing done to make our car(s) more interesting/personalizing. I have no doubt that my Mugen AIS served almost no additional purpose, but it's also some what of a bragging rights to have by having such a rare product.

Unless you have excess money to spend, spend the money wisely. A lighter parts such as CF hood, wing, exhaust, header, seats etc. will bring higher productivity than products that are still being debated. Wouldn't you agree?

 

[markc]

The line is the difference between the 2 pressure monitors during a WOT run? Maybe I'm confused by the scale, which shows the line starting off at around 1 bar.

There were indeed 2 pressure sensors, one inserted into the inlet grill (in the rear fender) and the other tee'd into the inlet manifold.
The line on the graph is the output of the second of these sensors (the inlet manifold one) during a W.O.T run. The output of the first sensor didn't change, as you'd expect. It is left there for a reference/baseline.

1 bar is standard atmospheric pressure. I have the full raw data file from the pullls and in fact the standard pressure during the run was 1.0116 bar. The pressure in the inlet manifold at idle was 1.0116 and as the graph shows it dropped steadily from about 2400rpm upward during the pull and recorded a minimum 0.978 bar at just over 8000rpm.

This may be insignificant BUT the w/shop, who of course do this all the time, advised that this 1) shouldn't happen 2) wouldn't happen in an ideal inlet setup and 3) doesn't happen with all/other cars.
Their advice was that there is a restriction somewhere on the inlet side. It'd be nice to locate and eliminate it

Here's the vid of my car on the Rototest dyno...

<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/71MpOVODIC0"> </param> <embed src="http://www.youtube.com/v/71MpOVODIC0" type="application/x-shockwave-flash" width="425" height="350"> </embed> </object>

Mark

 

[AR]

There is an interesting BTB used commonly in Japan, Infinity Q45's throttle body mounted with special bracket. Even with that, the HP increase is not proven given the fact if the Engine is left completely stock. I don't believe any of the NSX venders in Japan will do that mods without additional engine tuning.

Like this on GT-Roms website:

BTW a Q45 Throttle body might be cheap but the work to make it fit is not, so it is still a dear mod.

Cheers,

AR

 

[Tanto2]

Hi Tanto,

Are you saying that the pressure drop we measured is 1) normal and 2) not significant?
I had thought that it (this measured effect) might just be due to where they tee'd into the inlet manifold but wasn't sure? Has anyone else measured a similar pressure drop or indeed measured either side of the TB and not recorded a pressure drop?

As I understand it, you want the highest possible air velocity arriving at the inlet ports (of the cylinder head itself) at every point in the rev range? The object of the VVIS system (or any variable induction system) is to maximise this velocity over a wider rev range?
So, in a single TB system like the NSX, does the air velocity through the TB itself, given that it's so far upstream of the inlet ports, really move the torque/power up or down the rev range rather than just allow the engine to, potentially, make more at all points?
I can see how ITB's might move torque/power up or down the rev range, especially if each one had it's tuneable induction system.

I'm just trying to understand if the effect we recorded is a real one or an anomolly of the way we measured it, and if addressing it would release a few more HP.

AR, I don't think the guys with the Procar airbox's fitted had the stock ribbed rubber connector and they saw the same pressure drop so eliminating it wouldn't appear to help.

Again, I'm sorry I haven't read this whole thread so may be offbase. I'm saying separate the intake tract from the TB for your exercise. Generally racers just take a vacuum reading along the intake track at WOT. The lower the better, but there is a point where it's not significant, sorry I have done this(not on an nsx) but it's been to long. Once you get the intake vacuum down (like Honda already did 95%), you can forget about how it affects things after the TB. Like I said, intake velocities deserves it's own thread, it's not simple. The larger TB will only result in more flow(and hence HP) if the rest of the system will allow that flow to occur. The whole thing has to be looked at as a system. And that can only be done on the dyno thru trial and error. Sure the very few engineers that design engines on the computer for a living could calculate a test design and then refine. We and just about every race engine builder there is, is doing this by trial and error, finding what is limiting the velocity at the rpm they want to skew toward, upsize that bottleneck and dyno, etc. Picking cams is a nightmare. I have built several race engines, but the easiest and cheapest way is to talk with builders like Shad and let his experience save us LOTS of money. I would save the enthusiasm for the ITB's that you really want. Then can tinker for a couple of years getting them worked out. I'll be right behind you. Back on the intakes for a second: the only intake (before TB) that hasn't already been vetted is Vancehu's Mugen (it is him I hope). The entrance funnel they use COULD be good for a half HP or more. And it's the little stuff that counts for NA.

 

[ken sampson]

I have sent messages out on this topic and no one is responding.
I wanted to know if this will work with a TBW setup. I need more air for my SC setup.

 

[ken sampson]

Has anyone bought one of these to work with a throttle by wire?
Or will I need to convert to a cable?

 

[nsxsupra]

I just re-scanned the image of the Infiniti Q45 TB on NSX for reference. The old image was deleted.

In my opinion it is pointless to upgrade unless you also bore out the intake manifold opening and to take advantage of BBTB. The opening of intake manifold has to match the opening of intake manifold.

 

[ken sampson]

Now I have two questions so I can do this. One is do I need to convert to a cable drive? Or will the TBW work? Second what is the correct part number for the TBW TB?