Home away from home
From Melbourne Australia (and likely under the car)
Generally speaking - power is about two intimately connected things - combustion quantity (the amount of air/fuel you get into the cylinder to burn, which is why boost works so bloody well) and combustion quality (how well/completely/consistently it burns so power can be optimally extracted from it)....
If you are running efi, and can locate injectors optimally, then it's mostly about getting as much air in as possible and the injectors will disperse the fuel reasonably. If it's carbed, then every bend, every uphill section, any overly long sections - all of these can cause fuel to drop out of the flow, or for more of the fuel to be in small sections of the airflow, which leads to lean and rich pockets inside the cylinder and inconsistent/poor combustion quality.
So it sucks on that front. Next, our seller has used his wisdom to port "and polish" the intake. Porting is good. polishing, only in certain circumstances (and definitely not on the intakes). Here's the deal - smooth polished surfaces 'look' like more work has gone into them, but they don't flow any better on a flow bench. It's to do with boundary layer formation, but also because the polishing really doesn't increase cross section area. BUT the BIG issue with polishing an intake is that it MASSIVELY encourages fuel to drop out of the flow and condense on the manifold runner walls. A rough surface on hte other hand not only discourages the fuel to condense on the walls, it can actually help the airflow pick the fuel back up into the flow. .
So on the flowbench it might flow the same (certainly not better) but it will definitely cost power on a dyno with a polished intake. It doesn't have to be like the surface of a file, but the sort of finish left from carbide bits or rough stones (on cast iron intakes) is how it should be left.
It's kinda funny when someone tries to boost the value of an item they are selling using science, only to show their lack of actual knowledge on it. Clearly they aren't interested in what works best, they are willing to say practically anything to inflate the price. I just found the add on ebay - $1200? Considering you can pick up twin weber inlets and carbs for less than that it's ridiculous to say the least. For that money you could easily put together a complete sc14 based supercharger setup and make double the power.
EGR has been removed. Not great if you cared about compliance (ok most of us don't) but what they seem to be ignorant is that EGR only ever 'functions' at part throttle, it doesn't open/flow during full throttle, so in and of itself it doesn't affect power. Additionally - believe it or not, EGR actually impoves fuel economy. The reason is simple enough. If you ingest air and fuel at part throttle, the running or effective compression ratio is low - i.e. volumetric efficiency is restricted/throttled back, so less mass to compress at tdc. If you add in inert gases, they can't burn, and don't have enough extra oxygen to affect a/f ratio to the point of NOx emissions going up - but this (mostly) inert gas in there has volume/mass so it adds to teh volume/mass in the cylinder so it increases (for the same amount of fresh air and fuel going in) the amount of effective running compression. net result - slightly more power is made from the same amt of air/fuel being drawn in at part throttle, so better part throttle economy. SO if your pollution era carbed vehicle starts using more fuel, it's possible the egr is seized shut or blocked. you could get the same economy by leaning the mixture (providing the spark is strong enough to fire it). Anyway point being another area where it's implied that it is done for a performance gain but in reality it has no positive effect.
Lastly it mentions a washable hi-flow air filter, but does't picture it, so I'm guessing it is a k&n clone, or worse a ram-flo. The K&N are way over-rated in terms of efficiency, and only work (as far as filtration goes) as well as regular paper element types as long as they are properly oiled (and in my experience that doesn't last long). The paper elements are way cheaper, filter as well (or better if the oil runs out in the K&N). And they absolutely crap over the ramflo- which frankly are good at keeping small rocks out of the intake, but that's about all.
given the issues mentioned with that intake in general, and the modifications done to it (esp teh polishing) - seriously I wouldn't run it if it was given to me for free. At absolute best, if I got it for free, I'd adapt the carb to a 'normal' oval port intake. It'd still need a better air filter. Hmm, top value for $1200. True value - probably $100-150 tops
Posted on: 2010/8/24 10:29