Technical Advise - E36

[beemer E36]

Hi E36 users,
Need yr advise.
By doing 'POD & POLISH'
- Is it doable by law - due to increase in hp ?
- Would there be vibration on the bonnet during driving ?
- Would there be over heating ?
Pls advise.

Rdgs

 

[iScoupe]

Re: Technical Advise - E36

Hi E36 users,
Need yr advise.
By doing 'POD & POLISH'
- Is it doable by law - due to increase in hp ? NO
- Would there be vibration on the bonnet during driving ? NO
- Would there be over heating ? NO
did it 2yrs ago till now only thing i do is enjoy the power enjoy the fuel saving. but dun anyhow go advance the cams, go buy sport cams

 

[benji ben]

Re: Technical Advise - E36

ok i'm a noob. what is POD and POLISH? hahaha

 

[jeromez]

Re: Technical Advise - E36

i think it's port and polish....

 

[rudees]

Re: Technical Advise - E36

yup thats the word Port and Polish

 

[iScoupe]

Re: Technical Advise - E36

ok i'm a noob. what is POD and POLISH? hahaha

it mean u polish ur valves till u see ur loving face reflecting on it, whole engine bay look like new & smooth with carbon all clear.. after the clean up u most likely get back 99% of horse power the engine can produces, so u feel "wow very powerful!".. but actual facts, u did not get more power but becos u never enjoy it due to carbon build up when u took over the ride kekekeke... u only gain by upgrading sport cams after port & polish

 

[joon]

Re: Technical Advise - E36

All the bro's are right.. listen to them

Just to add.. in automotive engineering terms.. a 'Port and Polish' is used to describe several operations (1) port matching, i.e. you use a headgasket to match/reshape the interfaces between the cylinder head and intake manifold.. (2) typically a 3-angle valve job is cut into the head to reduce the lowest valveface angle and the altering the head's throat cut and seat angle.. when air flows around a valve it spreads out into a cone shape.. you want to change this flow cone shape at the low to mid valve lifts as this will fatten out the torque curve.. I had this done to my Civic VTEC engine and you have to remove the head, dismantle the valves, guides, lost motion assemblies (lifters in BMW engines) and send it to a special machine shop.. there are 2 in Singapore that I know can handle this type of work.. it costs between $1500 to 3000 per job and you need to run very high compression or high lift cams to take advantage of this..

Also I found that alot of workshops cheat their customers.. charging them for a 'port and polish' when all they do is clean up the intake ports abit and the poor owner won't know any better

A full port and polish is completely superfluous and unnecessary on a street car running a street engine.. if you just want to de-carbon your engine, you can use any number of fuel additives and engine flushes.. all of which will help a little

 

[iScoupe]

Re: Technical Advise - E36

yup careful on the workshop, there is different between cleaning carbon v.s. port & polish. I left my car at the workshop for 7 days to do it up, bill @ ~$2000 if i can rem correctly. Took the picture on after & before, huge different. But i made a mistake to advance the original cams, thou the pick up was superb, damn responsive ! but it caused huge "back fire" out from the engine more than 10 times till eventually damage my airflow ! airflow new ~$800 so think twice... BVO put cam back to normal, sui sui liao... enjoying the ride now keke..

 

[benji ben]

Re: Technical Advise - E36

wooo thanks guys for enlightening me. haha but do you guys actually recommend people doing it? like from what joon said, its unnecessary to do a full port and polish on a street car running a street engine. why? too expensive? not worth the money? from what iScoupe quote.

 

[louis]

Re: Technical Advise - E36

in addition to joon's input...

port and polish may be done on the intake and exhaust ports as well. the "port" increases the size of the intake and exhaust ports while the "polish" smoothens the surface - both are attempts to increase airflow and improve volumetric efficiency of the engine.

stock m54 intake port:

stock m54 exhaust port:

bmw engines already have 3 angle cut valves and valve seats from the factory:

you could still change the angles, go for a 5 angle cut or even a full radius cut if you really wanted to, but there's no good way of testing the effectiveness unless you have access to a flow bench, and as far as i know, there's no flow bench in singapore. most workshops will "test" by filling the cylinder heads with a fluid like water/oil and measuring the flow rate of the liquid....

if you're gonna be cracking the engine open anyway for some other repairs and have the cash to spare, then by all means, go ahead, but be prepared that it may only show small gains or worse, a loss in engine output.

 

[phil]

Re: Technical Advise - E36

i doubt there is anyone in singapore that has at least a flow bench and cc measuring capability is there? If this is not done correctly by a VERY trained person, you will ruin the engine output.

Be careful of valve angles as well.

PLUS. if you reco the head and do the polish etc, you WILL need to freshen up the bottom end as well, you will have trouble down the track if you dont. Replace rod and crank bearings and rings at least

Playing with heads is tricky shite

 

[jawzsg]

Re: Technical Advise - E36

Phil advising us to play with the bottom instead... good on ya' mate....kekekekek...

 

[phil]

Re: Technical Advise - E36

Jo, next time i see you, i get someone to port and polish you, can ar?

seriously, head mods are the best for hp gains, basically an engine is an air pump, you pump more air, you get more hp.

 

[Shaun]

Re: Technical Advise - E36

With most modern 4V heads, especially ones by better manufacturers and the sport models which may be hand finished from the factory, there is nothing much to do. On older or lower models, maybe only some casting flash, guide and bowl blending. Louis's M54 photos show the stock mess.

To go beyond basic clean up and get into port and venturi cross sections, port trajectory, major valve angle and size, changes and matching them to bottom end geometry and cam profiles is not practical without a flowbench and an engine dyno. There's a lot of science topped off with lots of iterative testing and it all costs more than a non-race market will support. It's not worth thousands of dollars unless you're very competitive with your car at tracks.

It is possible to port a head without a flow bench or engine dyno, but you must have had some years working with that specific type of head when you had access to flow bench and engine dyno and learnt the nuances of that head. Track testing works good in combination with the two tools, but by itself doesn't allow you to see micro trends in detail and make the big improvements esp under time constraints and then adapt them to ports and chambers of roughly the same kind.

Given lack of equipment and base experience with eqiupment in the region, it is only practical to do a rough clean up of the port, and preferably only when you happen to have the engine apart for other repairs or upgrades anyway. Short block to take advantage of major increases in flow from major development also will need to be serious, and again it doesn't exist in the region. For larger gains you are better off with crate heads and short blocks from proven companies in the US, Japan, UK, etc.

==

Louis, can you describe the liquid test a little more? It sounds more like port or chamber volume measurement rather than a flow test. Flow testing with no controlled pressure drop with an incompressible fluid of different viscosity, where head pressure would be dominate flow rate would be off I think.

==

Phil, CCing is simple... just a burette. Flow testing with a good bench is simple too, just many details that many times even some companies with flowbenches choose to neglect.

 

[phil]

Re: Technical Advise - E36

yes, agree with Shaun.

ccing is simple, only if you know how

I think louis is referring to chamber cc'ing.

if i think in old terms, many off the shelf aluminum heads are really quite good.

 

[louis]

Re: Technical Advise - E36

Louis, can you describe the liquid test a little more? It sounds more like port or chamber volume measurement rather than a flow test. Flow testing with no controlled pressure drop with an incompressible fluid of different viscosity, where head pressure would be dominate flow rate would be off I think.

shaun,

i've only had this test described to me by a malaysian workshop; have never witnessed this test myself but i'm pretty certain that it wasn't chamber cc'ing that they were referring to.

the test was described pretty simply: they just pass water or oil through a port and measure the flow rate across it. then they repeat the test again after the P&P to measure the increase or decrease in flow rate.

how they flow the liquid through, at what pressure/temp and how they measure the flow rate, i didn't enquire... so i'm afraid i can't furnish you with specifics.

i certainly agree that the measurements wouldn't be accurate though... i wasn't too convinced myself. that is however, as far as i know, the closest semblance to flow testing that i've seen offered locally.

cheers

 

[iScoupe]

Re: Technical Advise - E36

the best is not to do anything & change a higher cc ride, solve the problem.. if u going for it..
think i port here polish here only get extra 50cc but is the clean valves & cylinders tat got all the stock hp back...
then throw in a Open Pod bring in more air.. sui sui liao..

 

[phil]

Re: Technical Advise - E36

JAckie, i have a die grinder, lets play with your engine

 

[jawzsg]

Re: Technical Advise - E36

Phil.. jackie prefer you play with his physical anatomy... but like you say..not the head hor.. kekekekek... Kenntona say one.

 

[Shaun]

Re: Technical Advise - E36

Hey thanks Louis

Yah it's cool they're attempting to do something and not go forward completely blind. There're tens more that don't even try anything else I bet.. not for just realizing it isn't close to being representative, but that they just don't care at all about anything except moving product for money.

However, even assuming that there's a rig that keeps start head pressure equal, a reservoir large enough to reduce timing error as a % of whole, flow straighteners in the reservoir to keep vortex from forming (initial fluid movement will set them up in random direction depending on movement at start of flow), and exact bore shroud bolted to head, the main problems are:

- With flow testing with liquids is that with NA engine, the engine is pulling a depression, whereas fluid test is pushing.

- Even if testing a FI head where fluid is pushed in addition to being pulled, liquids do not compress or decompress (stretch) like air, so regardless of head type and whether FI or NA, turbulence in the port will never be seen. The density and viscosity differences between air and the liquid will give very different flows at point of discharge (venturi to seat to chamber).

The other thing is that since modern 4V heads (esp sport model heads) have very good trajectories, and turbulence in port is far less of a problem than in 2V heads, there will be a very strong correlation between plain min. cross section , and flow rate. If those guys just watch the liquid flow rate and follow obsession with a high number, and don't know about or ignore that a live engine is in reality only throughputting a more or less fixed volume dependent on bottom end volumes and speeds, then they'll end up porting to the limits of water jackets and spring pockets, ending up with a port way too big for an engine, killing minimum efficient velocity, and power along with it.