alright......I'd REALLY like to know, just HOW necessary is a port and polish? I find it difficult to discern the power gains between that and a new valvetrain, because most people usually do them at the same time! so, what, in theory, would the differences be between 2 heads with the same valvetrain and cams, one with a port n polish, the other without? I'm very curious, because there is a huuge difference in price! love to know....please post any dyno comparisons, etc here! thanks!

sure, every little bit helps, but if the gains are marginal.......I'd love to know!

Oh, and here's the picture that lured you in!

 

i'd also like to know!

 

bump! i really would like to know!

 

if u want every last ounce of performance get the head P@P. valve job is prolly the most important part of headwork. honda heads flow very well stock but can be made to flow better. u will prolly see better gains in a 2L with a P@P than from a 1.8L due to the amounts of air a 2L can flow that a 1.8L cannot.

 

Sounds like you need to do some reading. First of all understand that P&P can take on INFINITE variations. No two P&P's are the same, even NC P&Ps vary to some degree between each other. That aside P&P increase volumetric effeciency (VE) of the motor. Depending on the degree to which the P&P takes, you can gain VE accross the board, or sacrificie low end VE in exchange for high rpm VE, or kill low end VE for ultimate screaming VE, and the infinite combinations in between. There simply is no answer to your question, because it make no sense to "assign" numbers (ie. power) to a P&P.

And if you are curious what VE is read this right up I did on another site:

Volumetric Effeciency (VE) - This is a term that measure how effeciently your motor injests air through the intake and expells the exhaust gases out the exhaust side. I put this first for a reason. This is a very important term to understand, because most engine modifications effectively change the VE of your motor, and hince why you decreases or increases in torque and power at various rpms. Mathimatically, VE is the percentage of air that the motor injests and expells vs the total volume of air the motor could potentially injest and expell. First the easy part. How much can your motor injest. Lets use the 2.0L FS motor as an example. Its total displacement is 2.0L's, and it has four cylinders, so each cylinder displaces approximately 0.5L's. Now if the motor were 100% effecient at all rpms it would injest 0.5L's of fresh air each cycle then expell it. Unfortunately, a 100% effecient motor is impossible. The VE of your motor actually is not important, what is important is the VE curve, or a chart of VE vs RPM. Your VE curve will have the same trend as your torque curve, as measured on an engine dyno or a wheel dyno. So your peak VE will occur at peak torque. Without changing the displacement of the motor you cannot injest any more air, but you can change the VE of the existing motor. This takes on infinate degrees of modifications, from something as simply as changing the air filter or as complex as reworking the cylinder head with larger valves and ported runners. .....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1 2 NV &raquo;</TD></TR><TR><TD CLASS="quote">valve job is prolly the most important part of headwork. </TD></TR></TABLE>

Sorry to sound like an old lady but, "BINGO".

 

I agree with almost everything you said, but..

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
Unfortunately, a 100% efficient motor is impossible
</TD></TR></TABLE>

I see two reasons where you can have over 100% VE. (Maybe not through the WHOLE rpm band, but at points).

1 - Acoustical supercharging. When the resonant wave bounce off the closed intake valves and IM's, amplify and then enter with more energy, it is possible to go above 100% VE. (IE The AEM hump syndrom)

2- Forced induction. You are easy going beyond 100% VE.

 

I think the term "port and polish" is a misunderstanding in itself... Although there is porting and occasionally some smoothing or polishing involved the term kind of gives people the wrong idea...

A better way to put it would be "headwork"

Alot of flow improvement has to do with a proper valve job, and port manipulation... Reshaping, refinishing and promotion of flow efficiancy is key and IMO not even thought of when you use the term "port and polish"

Any goon with a grinder, a few cartridge rolls and flap wheels can "port and polish" a head... Does that mean its going to perform well on the track or dyno???

 

Quite a few NA motors have a VE of 100% if not more. High-performance honda motors have it or come close, and I think the S2000 actually goes a good deal over 100%

 

in plain english.....

ever tried driving really fast over a rough *** road?
now try it on a smooth paved one...

see the difference? well your car is the air flowing thru your head and the road represents the head surface....
rough road= non P&P
paved smooth= P&P...

hope thats helps


Modified by SnoFlake EG at 11:18 AM 9/20/2004

 

interesting analogy

 

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

thanx homie..just hope it helpos others

 

thanks a ton bryan pendelton and rick solis, your explainations really really helped!!!

 

thought I'd post this up as well, just found it, piqued my interest: https://honda-tech.com/zerothread?id=993338

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SnoFlake EG &raquo;</TD></TR><TR><TD CLASS="quote">
see the difference? well your car is the air flowing thru your head and the road represents the head surface....
rough road= non P&P
paved smooth= P&P...

Modified by SnoFlake EG at 11:18 AM 9/20/2004</TD></TR></TABLE>

Keep in mind, a completely smooth port does not mean the most performance. There are other things in effect like fuel automization and boundry layers.

 

good thing to know, freebie

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StyleTEG &raquo;</TD></TR><TR><TD CLASS="quote">I agree with almost everything you said, but..

I see two reasons where you can have over 100% VE. (Maybe not through the WHOLE rpm band, but at points).

1 - Acoustical supercharging. When the resonant wave bounce off the closed intake valves and IM's, amplify and then enter with more energy, it is possible to go above 100% VE. (IE The AEM hump syndrom)

2- Forced induction. You are easy going beyond 100% VE.

</TD></TR></TABLE>
That statement always ruffles some feathers. Yes yes yes, I am aware that naturally aspirated motors can achieve or exceed 100% VE at various engine speeds and flow rates due to complex fluid behavior, but with existing technology 100% VE over the motors operating range without the aid of forced induction is not possible.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SnoFlake EG &raquo;</TD></TR><TR><TD CLASS="quote">
ever tried driving really fast over a rough *** road?
now try it on a smooth paved one...
</TD></TR></TABLE>

ever seen airflow over a ping-pong ball vs. golf ball?

analogies aren't always accurate

 

Just a little comment. Max VE occurs at Peak torque. Whatever this number is, it has a lot to do with the cams as well as the head work. In general, not many n/a engines can achieve over 80%.

 

interesting arguments..... I'd love to see some dyno comparisons though!

 

oh snap!

head work, VE, rough roads, boundary layer...damn, guys are gettin technical.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StyleTEG &raquo;</TD></TR><TR><TD CLASS="quote">Keep in mind, a completely smooth port does not mean the most performance. There are other things in effect like fuel automization and boundry layers.</TD></TR></TABLE>
now see, for all practical reasons, this is the most accurate statement on the page, IMO. But, if someone were to do an entire p&p job, damn near every arguement on this board would be wrong, with the exception of complete rpm 100% VE.

ie: you get a pr3, weld it up, then start doing port work on a CNC machine. optimum port path is straight, with little to no bend at all. this makes for the fastest, cleanest path to the combustion chamber, and allows a laser injector to be ran which will increase fuel atomization when it shoots the backside of the valve, as well as cool the valve down. (laser injector shoots a smooth, tightly packed spray of fuel) since atomization doesnt occur til the fuel hits the valve, which is already exposed to the combustion chamber, you can run polished/dimpled ports which will reduce your boundary layer/increase velocity. VE will increase now that the same size port can flow air in a much more efficient manner. the last thing a complete p&p deals with would be the valve seats.

this was just an example. for all practical purposes, nearly every peice of advice is correct.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RStoR &raquo;</TD></TR><TR><TD CLASS="quote">ever seen airflow over a ping-pong ball vs. golf ball?

analogies aren't always accurate
</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fox297 &raquo;</TD></TR><TR><TD CLASS="quote">Just a little comment. Max VE occurs at Peak torque. Whatever this number is, it has a lot to do with the cams as well as the head work. In general, not many n/a engines can achieve over 80%.</TD></TR></TABLE>

Just thought I'd get in on this little debate about VE. All of what I am about to say is just stuff I'm repeating from another site. I found all this stuff out a few years ago when I was researching peak VE% for Lude motors.

In general what you are saying is true about max VE occuring at peak torque. However http://www.autospeed.com stated that an S2K had a max VE of 112% ocuring at peak HP RPM (8K-ish RPM). For an H22 the peak VE was 102% which occured also at peak HP RPM which is 7K RPM. Honda R&D co ltd allowed their engineers to write a paper which was published by the SAE on the F20C., and these VE numbers can be found in that SAE paper. Several other personal sites on the net and other info sites also say that VTEC motors are the exception to the rule that max VE only occures at peak torque.

http://www.autospeed.com/cms/article.html?&A=1127

 

peak VE occuring at peak torque is a generality, as it is all dependant on tuning. As VE is based on mechanics and dynamics of the motor, while peak torque is dependant on tuning as well.

with regard to vtec motors, Its possible that peak VE occur on the small lobes, while peak VE occurs on the big lobes. I suspect that peak VE on vtec motors is probably near peak torque on vtec/big lobes.

 

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

Keep in mind, a completely smooth port does not mean the most performance. There are other things in effect like fuel automization and boundry layers.</TD></TR></TABLE>

yes i know that...i just put it in the lamest terms......anyone can get what i was trying to say there.....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BryanPendleton &raquo;</TD></TR><TR><TD CLASS="quote">peak VE occuring at peak torque is a generality, as it is all dependant on tuning. As VE is based on mechanics and dynamics of the motor, while peak torque is dependant on tuning as well.

with regard to vtec motors, Its possible that peak VE occur on the small lobes, while peak VE occurs on the big lobes. I suspect that peak VE on vtec motors is probably near peak torque on vtec/big lobes. </TD></TR></TABLE>

did you click the autospeed link? if you look in the link it says in there that a group of Honda engineers wrote a paper published by the SAE. One of their findings on an F20C was that max VE occured at 8000 RPM (peak HP RPM). You can even order the paper from SAE.org and you can read it for yoursef.