Dan23 Posted May 24, 2011 Report Share Posted May 24, 2011 Ok after watching chop shop this Sunday just gone and the BMW they mangled they ported the 1.8 intake engine to give it around 200bhp, now seeings as the 1.8 is only like 115bhp stock that was pretty impressive, so I was thinking would porting the plenum in the 3s-ge that would free up a few extra ponies would it not? As I understand it the plenum is caste steal and the tunnels on the plenum are probably not as smooth as they could be creating a resistance of air flow, so smoothing them would allow the air to flow freely??? Anyone got any thought on this, i.e is it worth doing? Is there going to be any decent increases in power? Am I thinking about the right part to port? Could a DIY enthusiast do it or could I potentially fuck up the performance if I was to say over smooth the ports? Link to comment Share on other sites More sharing options...
rpsmith79 Posted May 24, 2011 Report Share Posted May 24, 2011 If the inlet manifold is anything like that on the Gen 5, then i can imagine it would be very hard to port due to the depth of the ports and the bend in the 4 runners The BMW inlet must be shocking if they can release that much power just by porting the plenum There is also 2 trains of thought on inlet porting, some same yes do it as it allows the air to move more quickly, other say don't do it as the rough surface of the inlet create a little bit of turbulence that helps the air and fuel mix better, but i suppose before it enters the engine that won't be too much of a problem Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 Well I think they added filter, system and sports cat but they seemed to free up a fair bit of power from doing it. So I guess it would need to be down by someone who has the tools to get into the thing. From what I gather less resistance is better as it allows the air to flow better, but if gain was minimal and cost was high then it's obviously not worth doing Link to comment Share on other sites More sharing options...
sonic Posted May 24, 2011 Report Share Posted May 24, 2011 if you hunt around the interweb there was a wright up on a gen 4 gt4 a few years ago , where the owner was porting and polishing bits , he done the throttle body , plen , altered the tvis and ported the head , in theory you would just need a dremmil to open it out , i cant see much of an improvement , but as tesco's say , every little helps , and you would be going the right way Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 I might invest in a second hand plenum and give it a try, as you never know, it might help, and it might even just clean the thing out, might even to the tb too Link to comment Share on other sites More sharing options...
rpsmith79 Posted May 24, 2011 Report Share Posted May 24, 2011 Again though, it all come down to how well the 3SGE was designed, the BMW engine probably wasn't designed as well as the 3SGE, hence why they can release so much power with simple mods, either that or they used a very shoddy dyno I think it would cost you a fair bit to have it done by a pro, best bet is to get hold of a spare plenum and have a play with a dremel like Sonic said Link to comment Share on other sites More sharing options...
sonic Posted May 24, 2011 Report Share Posted May 24, 2011 i read somewhere , when it comes to polishing , you want to be using something like 80 grit so its smooth but not shiney , as this helps atomise the fuel better , could be wrong , but worth checking Link to comment Share on other sites More sharing options...
cooperman Posted May 24, 2011 Report Share Posted May 24, 2011 i would say that you will not get any thing out of any thing you are doing at home. unless you understand fluid dynamics and thing like venturi effects you will more likely do more harm than good. you have to remember that toyota farmed the job out to yamaha for a good reason. the pro's will use a flow bench test to get it right. but in saying that if there are any major casting fraze, flash or burr's then removing them back to the standard surface will not hurt. i cant see there being may, if any though. working with carbs i have seen some real bodge jobs in the past. people that think they know what there doing and smooth every thing out in the carb and then end up sending it to use saying it doesnt work. there are a few corners/angles in the carbs that are ment to be there and once gone they just end up being expensive paper weights. was it not SJ that had porting and polishing done on his and it returned next to nothing in gains? just my thoughts. andy Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 Well I have the benefit of my old man who used to be a mechanic to help me. My main worry would be doing it and messing the engine up or worse distorting the engine due to it, I know that sounds extreme but you gotta take all things into account when doing stuff to the engine as I would be altering the air flow rate and as you say Andy, most places would probably use some kind of air flow bench, but in the same vain I can't see Toyota/yamaha really spending to much time making sure the plenums are as smooth as can be and being caste unless you port them you will always get imperfections on the tunnels, could explain why some 3s-ge's feel slightly quicker or get slightly better results as the caste was smoother when it came out the machine, again just a theory of course. And on another note, my car has done 152,000 miles so I can imagine the tunnels on the plenum are not as smooth as when it was made, and it wouldn't surprise me if it also had oil in it too Link to comment Share on other sites More sharing options...
rpsmith79 Posted May 24, 2011 Report Share Posted May 24, 2011 Andy, i think doing a DIY job on the inlet manifold is slightly different to porting your head though, i wouldn't recommend doing that yourself, but the inlet manifold is only there to get the air to the head where it then gets mixed with the fuel Link to comment Share on other sites More sharing options...
sonic Posted May 24, 2011 Report Share Posted May 24, 2011 as andy said , burrs etc , when the stuff was originally cast , would make a small difference , personally , would clean out the plen , look for shit bits that can be removed , buy a second hand head and get it properly blueprint ported , and then get a nice custom made exhaust header knocked up , that should make it breath , fennies claim that 200 bhp out of a rev 3 going down this route is easy achievable , and cheaper than a beams swap and as we know andy knows more than me , as his car is still running Link to comment Share on other sites More sharing options...
cooperman Posted May 24, 2011 Report Share Posted May 24, 2011 i wasnt on about porting the head. apart from at the end with the SJ bit. alot of people think that the inlet track is just there to get the air from point A to point B. there is more to it than that, the length and diameters of the tracks and even down to the corner rads make a huge difference. you can tune an engine to perform at different revs by the length of the inlet track for example. thats why you have acis. all im saying is its just as easy to get it wrong as get it right. dan as for getting fraze from the casting, with mass production and pressure die casting and good tool makers you can get an almost perfect finish every time. there is also things like electro deburring that will take out burr's with next to no man hours involved and de-flashing presses that can be automated. so again no man hours involved. im not saying dont do it im just saying dont expect anything from doing it. if you go in expecting nothing and get some thing its a winner. that bmw engine must have been designed by stevie wonder to get an 85bhp or 73.9% gain from doing that. Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 Yep this is true Ian, can't trust you cos your car don't even run with your bodge super chip fitting The plenum is something I'm gonna look into, not to sure on playing about with the head as that's defiantly specialised work and I wanna try and keep costs down on the car and having the head ported and custom exhaust headers made up will probably push into the few hundred quid then the price of fitting and cos you cam belt would have to come off that will bump it up a few hundred quid again as it would be better to put a new belt on, that seems like more effort then it's worth ATM I'm just trying to find cheap way of making the engine better where anyone can do it, like I say even if it just gave better response thats a bonus in itself Link to comment Share on other sites More sharing options...
sonic Posted May 24, 2011 Report Share Posted May 24, 2011 Yep this is true Ian, can't trust you cos your car don't even run with your bodge super chip fitting you forgot the unfitting still it looks the bollox with its carbon window Link to comment Share on other sites More sharing options...
sonic Posted May 24, 2011 Report Share Posted May 24, 2011 (edited) could always blue fin it , apparent 8-10 bhp gain , just a more advanced plug n play version of my icon race advances the ign but 300 rpm over the whole range , but can be tweeked over the whole range ie retarded at 1500 rpm but advance at 6000 rpm to get the most out of the car http://www.superchips.co.uk/search?make=36&fueltype=1&model=231&variant=1455 Edited May 24, 2011 by sonic temple Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 But that's a cost I don't wanna pay mate Link to comment Share on other sites More sharing options...
spotv6 Posted May 24, 2011 Report Share Posted May 24, 2011 (edited) there is an engineer on 2brutal who has done quite a lot of work on porting and polishing called fourveesix being honest most of what he states is simply too technical for me but basicly dan it certainly isnt a job for an enthusiastic amateur he really does know his beans and the kind of gains you are talking about he would probably show you exactly how its simply impossible on a side note chop shop!!!!!!!!! :rolleyes: Edited May 24, 2011 by spotv6 Link to comment Share on other sites More sharing options...
Dan23 Posted May 24, 2011 Author Report Share Posted May 24, 2011 it was sunday and i was bored and i had it on discovery turbo and couldnt be arsed to change the channel lol Link to comment Share on other sites More sharing options...
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