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-   -   Porting and Polishing!!! (https://www.team-bhp.com/forum/technical-stuff/4090-porting-polishing-3.html)

Hi Guys,

I have carried out porting / polishing on almost all the cars I own and will recommend it to anyone who is performance oriented. Like any performance modification to gain something you have to loose something.

FE is affected only when you drive hard. If drivem normally it improves. This will again defer in the manner in which the porting is carried out. Also porting should only be done after a free flow and not before .

Call or pm for any more details/

Viper

Porting and Polishing is us perfectionists who also happen to be petrol heads giving finishing touches to regular assembly line production glitches!!!

It wouldn't be feasible to port and polish standard passenger cars.......... if you've read anything on the subject you'll know that it's the cast irregularities that we're out to smoothen........... assembly line cars are like building blocks put together...... they work fine that way so the manufacturers don't care.......

" polishing ports to a mirror finish. This actually does more harm than good. Remember it is not only air which is flowing but atomised fuel along with it. The problem with fuel is that, since it weighs more, it's difficult to keep it evenly mixed with the air as it follows the contours of the port."

" he next time you drive a car in the rain, notice that when the car is going 60 KMPH, the rain drops go up the hood of the car at walking speed. That's because the smooth surface of the car creates what's known as a boundary layer, and the portion of that layer of air that's nearest to the surface is almost still.
The same thing happens inside an intake port. Except instead of raindrops, it is fuel droplets that will run down the port wall slower than the air.
That causes a serious change in the fuel air mixture by the time it reaches the cylinder, ruining much of the engine's potential power. Polishing the port walls will ensure this happens.
Instead, by making a series of rough 60 grit lines that purposely go against the flow, the ‘boundary layer area’ will be turbulent, and the fuel will stay well mixed and suspended in the air.
Remember: Rough is Good !!"

Source: http://auto.indiatimes.com/articlesh...,prtpage-1.cms

Now many a times i have see that shaving and shining the ports seem to be a std level 1 mod for almost all car entusiasts!

Can someone be kind enough to eliminate the doubt?

Thanks,
Madan

Madan,

Smooth/shiny exhaust ports and relatively rougher intake ports seems to be the way to go.

Please do a search before creating threads. Threads merged.
cya
R

BUMP
i want to know if it is feasable to make my ports smaller.
i know it is a crazy stupid question. can any one help.

Hey,

How do you plan on doing that may I ask and why.

Viper

that was going to be my second question.

seriously speaking, i read something online about smaller ports making more power, and i thought it was bs. just confirming.

i just read up more on it. they are called high velocity ports. they are smaller than stock and make more power. some of the bikes that won the AMA supersport championship have them.
the real question, as viper said, is how to make them.

Ah you've read motoman's article on velocity ports :p
I read that article close to 2years ago and asked a whole bunch of similar questions.
Then realised what a bunch of bull all this velocity porting really is.

Will post up tomo morning about why it doesnt work in detail.Too sleepy rite now

Heres a like to the article for those who havnt read it Think Fast--Intake Porting For Motorcycles and Cars

Weld on material and grind to smooth it.....hahaha..easier said than done.

cya
R

A lot of FSAE teams look to reduce size of the exhaust ports, because within the restrictions they flow too much.

Heat would transfer horribly from the port walls to the water jacket because of the multiple layers of the metal.. causing overheating.

Also all this welding and all doesnt quite work when your working on engines.

Velocity porting will only work on very high revving NA engines and there too they are of limited use. Port angles are way more important to give you the maximum gain. The best way to explain is to say that you ought to be able to design a port that would maximise the air entering the cylinder with the least resistance on the valves.

just the kind of answer i was hoping to get.

yes it was motoman, been reading a couple of things that seemed too good to be true.

@cbr do write why it doesnt work, i'm interested.

All BMW M cars have fully CNC machined intake ports and combustion chambers. Its expensive and labor intensive for the benefit you get and thats why nobody does it. Ford SVT had a special process for smoothing the intake as well.