Ive got an Edelbrock Performer X intake manifold which comes stock with a 66mm entrance. I was thinking of buying a tapered/bored 70 to 66mm throttle body from Dave at DH-Racing to create a venturi into the intake mani and he offered me one from 70 to 65mm for $199 plus shipping. When I insisted on a 70 to 66mm he told me it would be $50 more:

.020 difference cant be seen with the human eye i can take a machine cut to make it 66 but will have to charge you for it

I know it's better for airflow to go from smaller to larger as in this case 65mm throttle body exit to 66mm intake mani entrance as opposed to the opposite which will create turbulance.

My question is since a 66mm throttle body exit to a 66mm intake mani entrance is optimum, will going from 65 to 66 affect my performance or am I being ****?

Here is my build:

B18b block GE sleeved and bored to 84.5mm
Endyn crank girdle with AEBS main studs
Balanced, chamfered, polished crank
ATI crank damper
Eagle rods with ARP bolts
CP 12.5:1 84.5mm pistons
Alaniz Competition VTEC head with Pro Chambers
Skunk2 Pro Springs, Retainers & Cam Gears
Supertech Flat BNC Valves
Edelbrock Performer X intake port matched to throttle
BPI CAI stack on 3" piping
SMSP B19 Header
2.5" custom mandrel piping into Magnaflow resonator and Vibrant muffler
RC 370cc injectors
Hondata s300
Skunk2 Pro 2's
Del Sol hydro tranny with 4.78 final & ITR LSD
Competition Stage 4 Strip Series Clutch Kit
Meziere Electric Water Pump

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7rrivera7 &raquo;</TD></TR><TR><TD CLASS="quote">I know it's better for airflow to go from smaller to larger.

My question is since a 66mm throttle body exit to a 66mm intake mani entrance is optimum, will going from 65 to 66 affect my performance or am I being ****?</TD></TR></TABLE>

****. The extra 1MM won't make a difference.

Now When you say it's better for airflow to go from smaller to larger are you talking about this specific scenario?

 

im in for more info about the venturi effect

 

This is a reason I dont like tapered TB's. The air should slow down as it enters the plenum. If it doesnt, how does it make the turn into the runners?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lude98SH &raquo;</TD></TR><TR><TD CLASS="quote">im in for more info about the venturi effect </TD></TR></TABLE>

I went looking for the article I read to refresh my mind on it after I replied, but I could not find it. I got the basic principles from wikipedia: http://en.wikipedia.org/wiki/Choked_flow

You can apply the basics to air flow in our engines, but the article went over it more specifically. Anyone have a good read up about the Venturi effect and how it can be applied to our engines?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dark@Powers &raquo;</TD></TR><TR><TD CLASS="quote">

****. The extra 1MM won't make a difference.

Now When you say it's better for airflow to go from smaller to larger are you talking about this specific scenario?</TD></TR></TABLE>

Yes because in this scenario, if you go from a larger TB into a smaller intake mani entrance, the turbulance created from the air hitting against the edge wall will impead flow.

Now CC's comment against tapered TBs is interesting. CC, are you talking from experience?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">This is a reason I dont like tapered TB's. The air should slow down as it enters the plenum. If it doesnt, how does it make the turn into the runners?</TD></TR></TABLE>


So honda got it wrong since all there's are 2mm tapers on every model

 

Did Honda get it wrong with their manifold designs as well since we all replace them with Skunk2/Edelbrock/blox/AEBS/ENDYN/custom ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7rrivera7 &raquo;</TD></TR><TR><TD CLASS="quote">

Yes because in this scenario, if you go from a larger TB into a smaller intake mani entrance, the turbulance created from the air hitting against the edge wall will impead flow.

Now CC's comment against tapered TBs is interesting. CC, are you talking from experience?</TD></TR></TABLE>

That would be the case, if your TB, on the IM inlet side, was sized larger then the IM inlet. But your TB is 1mm smaller then the IM opening.

Now, I have never seen this discussed in depth, but I don't think you would witness a loss of power if you were to Oversize the TB by 1MM, on the IM inlet side, when compared to the IM inlet. Ex: 65MM TB to 64MM IM inlet. Of course there is no reason one would actually want to do this. Although this seems to be a "bottlenecking" situation, which is better related to exhaust side of things, I think it would be fine. This is all what I've taken from what I know tho, as I have never seen this directly discussed. Could someone confirm/dispute that Oversizing the TB by 1MM over the IM inlet would not have a significant effect on flow?


Modified by Dark@Powers at 6:59 PM 6/28/2008

 

The upper picture shows air flowing from a smaller throttle body into a larger intake manifold. It seems logical the air will flow easily at the juncture between them

It also seems logical the air will crash at the juncture between them as shown in the lower picture. Although this only happens at the extreme edge of the air flow, does this or doesn't this negatively affect horsepower potential?

In this specific case, is a 1mm difference neglegable?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">Did Honda get it wrong with their manifold designs as well since we all replace them with Skunk2/Edelbrock/blox/AEBS/ENDYN/custom ?</TD></TR></TABLE>

You should call honda engineers and let them know random no name wannabe head porter says their wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">Did Honda get it wrong with their manifold designs as well since we all replace them with Skunk2/Edelbrock/blox/AEBS/ENDYN/custom ?</TD></TR></TABLE>

Skunk2's original manifold and Blox manifolds are ITR copies. So the ITR manifold is a poor example has well

What about the itr throttle body garbage too


Your funny.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxmanifold &raquo;</TD></TR><TR><TD CLASS="quote">

You should call honda engineers and let them know random no name wannabe head porter says their wrong.</TD></TR></TABLE>

He's asking to start some discussion, since everyone likes to move to aftermarket manifolds without thinking about it. Obviously Honda manifolds aren't designed for anything but Honda factory engines.

 

All b series/h series/k series manifolds are 2mm larger at the manifold inlet then the throttle body plate.

But again Honda doesnt know what there doing according to internet porter

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by downest &raquo;</TD></TR><TR><TD CLASS="quote">

He's asking to start some discussion, since everyone likes to move to aftermarket manifolds without thinking about it. Obviously Honda manifolds aren't designed for anything but Honda factory engines. </TD></TR></TABLE>


So the rbc manifold is a poor example of performance. The ITR manifold is what started skunk2 back in the early days when they were skunkworks since they copied the exact ITR manifold and sold it cheaper than Your Local Acura dealer


ITR manifold ported will make enough power to support 99 percent of b series all motor builds. That applies to the RBC has well

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7rrivera7 &raquo;</TD></TR><TR><TD CLASS="quote">
In this specific case, is a 1mm difference neglegable?</TD></TR></TABLE>

Just to confirm, this is not your original question right? Just making sure..... I say yes, the 1MM is not enough to make a difference, but I have not seen this addressed directly so I really hope someone else can chime in on this.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxmanifold &raquo;</TD></TR><TR><TD CLASS="quote">All b series/h series/k series manifolds are 2mm larger at the manifold inlet then the throttle body plate.

But again Honda doesn't know what there doing according to internet porter</TD></TR></TABLE>

Honda has a great engineering team, but they are not psychic, in the world of tuning, everyone has a different goal. Some people look for midrange power, some for power in the upper RPMs. This is where manifolds will need to be replaced because they were not designed for what we are "tuning" the engine to do. The manifolds on our stock engines are designed for what they wanted for the engine, not what us, the tuner, wants.

The GS-R manifold came stock on the B18C, but if you are looking for more power in the higher RPMs, you are going to look for a manifold with short runners, such as a Type R manifold. Too bad, the Type R manifold does not share the same bolt pattern for the B18C tho hu? That's where the aftermarket companies, who copied the manifold, came in. The fact that we are replacing OEM Honda parts with aftermarket does not mean we are telling Honda they are wrong, but that this piece of equipment is not designed for our build.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxmanifold &raquo;</TD></TR><TR><TD CLASS="quote">You should call honda engineers and let them know random no name wannabe head porter says their wrong.</TD></TR></TABLE>

Sounds to me like you're the internet warrior here. Where did I say Honda was doing it wrong? Doing it wrong for what? Maybe with their nominally sized plenums, a 2mm taper , which is .080" , is OK for good street manners. That is what manufacturer's with a 30k mile warranty are concerned with, right? It probably helps a tiny bit with low speed throttle response. Hmm, but when does air begin to become turbulent? Low air speed/nominal throttle angle? Mid air speed/50% throttle? High air speed/ 100% throttle? A taper isnt necessarily bad DEPENDING on the size of the plenum relative to the displacement of the engine relative to valve timing events.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxmanifold &raquo;</TD></TR><TR><TD CLASS="quote">But again Honda doesnt know what there doing according to internet porter</TD></TR></TABLE>

Again, show me where I said Honda doesnt know what theyre doing. I dislike the fact that you had to make 3 or 4 different posts, with various insults slung in my direction. Again, dipshit, a manifold should be matched to a set of camshafts and throttle body to make the entire induction system tuned. While a 2mm taper might work well on a nominal sized plenum with 8200rpm peak power and low duration camshafts, I think 9500rpm might want a bigger plenum, tapered plenum, shorter runners, tapered runners, longer duration valve timing, and possibly a different valve job and port. Throat size will probably want to be different too.

You can take your "no name head porter" insults and shove them up your ***. Plenty of people are happy with my work and making good power. Just because I havent gotten so big that Im working for a NASCAR/F1/INDY/CHAMP/ALMS team yet, doesnt know I dont know what Im doing. You can ask a few members of this board about my work and I dont think youll find anyone that has been disappointed.

GO ***** YOURSELF.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">GO ***** YOURSELF. </TD></TR></TABLE>

Clean and Simple

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7rrivera7 &raquo;</TD></TR><TR><TD CLASS="quote">

The upper picture shows air flowing from a smaller throttle body into a larger intake manifold. It seems logical the air will flow easily at the juncture between them

It also seems logical the air will crash at the juncture between them as shown in the lower picture. Although this only happens at the extreme edge of the air flow, does this or doesn't this negatively affect horsepower potential?

In this specific case, is a 1mm difference neglegable?</TD></TR></TABLE>

Combustion, what would you say about this issue. ^

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">
You can take your "no name head porter" insults and shove them up your ***. Plenty of people are happy with my work and making good power. Just because I havent gotten so big that Im working for a NASCAR/F1/INDY/CHAMP/ALMS team yet, doesnt know I dont know what Im doing. You can ask a few members of this board about my work and I dont think youll find anyone that has been disappointed.

GO ***** YOURSELF. </TD></TR></TABLE>


the man can port...to CC



Modified by JDM JEFFREY at 2:18 AM 6/29/2008

 

The 0.020" step is the least of your worries. Consider the turbulence created by the throttle plate in the middle of the airstream and further upstream the turbulence created by the intake to TB coupler.

However yes it's better to step into a larger bore. There are anti-reversion effects when doing so.

Pro-tip, when installing your TB make sure you open the TB plate and ensure the TB is centered to the manifold.

 

K series OEM Throttle Bodies have a 3mm taper from inlet to plate so the motor that owns everything for some reason honda added more taper from the older models. Thats odd. Those engineers need to spend more time on here.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxmanifold &raquo;</TD></TR><TR><TD CLASS="quote">K series OEM Throttle Bodies have a 3mm taper from inlet to plate so the motor that owns everything for some reason honda added more taper from the older models. Thats odd. Those engineers need to spend more time on here.</TD></TR></TABLE>

VTC , & the fact that it is larger than the B family, might have something to do with it.

 

Sounds like someone's got it all figured out. More taper = more airflow = mo powa.

There are reasons for tapers and reverse taper airflow wise. But I think most of the taper in TB's is a result of keeping manufacturing flexibility and not so much 99.9999% airflow optimization. 'Member, airflow is easy:

<FONT SIZE="5">"Da bigger da ho, da mo it flo."</FONT>

Canjun Style. U HERE ME BOI!!! LOL.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Master of the Universe &raquo;</TD></TR><TR><TD CLASS="quote">'Member, airflow is easy:

<FONT SIZE="5">"Da bigger da ho, da mo it flo."</FONT>

Canjun Style. U HERE ME BOI!!! LOL.</TD></TR></TABLE>


Dat's why I gots me a Mustang TB