Hmm, well this is fun
Not ashamed to admit that I am rather lost too. But what to do, here I am on the jury.
So what can I consider? Motive and bias. Motive is what you might be selling or otherwise receiving benefit from. Bias could be affected by that as well. Who is the most impartial? I would think Rebello as his opinion( must be verified of course but that would be easy for the reader, er, jury, to do) would result from more experience than just Will's and based on his natural motive which is to do the best for his clients, or customers. So unless he has a promo deal with ITN, I would give his testimony more weight. K&N engineers have a bias, they could emphasize the strong points and downplay the weak points. We would have to put them under oath to find out shock:
So, JT, unless you could get Dale Earnhart Jr, Jimmie Johnson, and Kyle Busch to state the same preference for K&N, I still lean towards Will's position, partly because I have no way to understand or validate what you carefully explained re air flow, intake, outakes, whaaaat?
Lol
Linda
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
Dyno would be a waste of time and money. The ~150 hp U20 will still make ~150 hp with either the ITG or the K&N, because neither will be the limiting factor on the engine. You gonna try to resolve 1 or 2 hp? Nope, you are into the resolution of the measurement system.
Yes a flow testing system would be the way to go. But why?
I'm 500% sure the ITG will flow just great. I'm equally positive a 2" K&N will flow excellent. Any difference is academic.
What does it matter if the K&N can support 265hp and the ITG 275? Zero.
That's the point--- it's totally meaningless on a street U20.
Regarding filtration, K&N has spent $$$$$$ doing the science over 20 years, they will discuss it at length with you. Nothing will convince Will otherwise.
Great unbiased, scientifically tested info. Performed by an impartial engineer with no agenda, company allegence or racer mythology and voodoo.
Agree totally. Paper is the best in terms of filtration, but the worst at flow rates. No question.
"For the record the K&N was the best flowing filter. Of the 3 types of media tested, the cotton gauze type filters flow best"
"That said, both the cotton gauze type (K&N) AND FOAM FILTERS, showed the same levels of filtration. Both performed poorly relative to paper elements"
If you are concerned about it, run the OEM. If you want flow, run the K&N or a Foam element as you prefer.
I'll let you know if I can build a 2" and stock ITG filter for use with the repro and original housing. (Kinda, Pretty much absolutely certain SlowRoadster will have issues with it) J
So I gathered from the somewhat scientific post from the oil dude that there really is no real world difference in flow that would result in ANY hp change, but there is some difference in the level of protection offered (though again, the author admitted that his method was somewhat limited), with paper filtering best. While the ITS was not specifically tested, the foam and KnN filtered the same based on the somewhat questionable testing. Bottom line from this particular test and methodology is that there really is no significant difference in flow that would result in a noticeable hp change, but you might wear the engine slightly faster with a non paper element. That is a reach however and cannot be determined by this ONE test with very questionable methodology and little discussion of other confounding factors (as to be expected: This is not a rigorous scientific study!).
There are other measures of performance that would not reflect just HP ratings though, such as throttle response, which is hard to measure scientifically and consistently. I do know that I was in the car when Ross removed (and then added back) the second element on a stock early Solex filter set up (the one with the built in stacks) and the throttle response was NOTICEABLY different: The engine was much more responsive (but it probably produced the same HP.) However, that could be due to many, unmeasured factors. It is possible there was just a bit more unshrouding of the stack, or maybe slightly cooler air?
Regarding airflow, I do know that air does not like sharp corners, and that can cause problems or reductions in flow. So, the addition of velocity stacks, with fully radiused stacks being marginally THE best, will improve performance. How Much? Only a dyno will tell you, but I do believe that throttle response will improve (that's been my experience and what makes it worth my efforts to create a cold air box that has built in stacks).
So, bottom line, run what ya want and what you can afford! They will all work about the same. Most importantly, use a stack on ANY carb (SU or sidedraft), keep the stack unshrouded and free to gulp air, try to keep hot air away from the carbs, and enjoy the ride!
No doubt. You will notice a difference switching to the K&N or ITG over one stock paper element. ( it may not be huge, but likely you will feel it).
Totally correct on velocity stacks as well. You will notice.
As long as there is an inch of free space in front of the bell, there is plenty of air to supply the carb.
From a practical perspective with the number of miles put on a typical SOLEX roadster in a year, unless you are in a super high dust climate (still may be irrelevant), this whole discussion is of little concern.
Two stock elements works great if you gotta have paper!
The engine is simply an air pump and the only variable that the air filter can affect in regards to performance is intake manifold pressure, all things being equal. More delta P across the filter equals less manifold pressure equals lower performance.
Greg, I wonder if the stock single element Solex filter box is way more restrictive than the .25psi drop in the stock Miata box...therefore doubling the filter area made a much greater gain in manifold pressure than the Oil guy saw in the Miata.
Also I know that louder intake noise always makes my 'seat of the pants' dyno indicate more performance
I hate to discredit this, but the author himself says "Like everything in life, this filter test wasn’t done right the first time" Per the author...
I am not saying there isn't value in the Oil Guy's test, but it doesn't exactly fit our situation. His test filters were all the same surface area whereas the ITG filter has a larger surface area for the intake of air over the K&N alternative. That's likely why why some ITG owners feel they breathe better.
Oil Guy's filters for reference...
Oil Guys Filters.jpg
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Last edited by Solex68 on Wed Apr 26, 2017 4:36 pm, edited 1 time in total.
Greg a.k.a SOLEX68 - http://www.datsunvents.com/
Laguna Hills, CA
68 2000 Always willing to help another Datsun Roadster owner
Pending installs: SS brake lines, Stan Stealth Dizzy
Even though the testing is not perfect, there are still several correct conclusions.
I could've told you paper is the cleanest element, but also flows the worst. The manufactures will tell you the same thing.
The filtration capability between K&N and foam is about the same, which mirrors my experience. He didn't even talk about the foam breaking down.
In terms of absolute flow, perhaps re-read the discussion on surface area that I posted. Either the K&N or the ITG
will breathe beautifully for any street U20. No doubt. They are both overkill and the difference is academic.
Linda wrote:I don't have Solexes, and if I did I would sell them so fast it would be a blur.....
Why?
Solexes ,for me, would be noisy, use more gas, more trouble to set up , and for the money I'd get there are other things I want more for the car. Oh and I don't care about any performance gain enough to bother. Therefore, not worth it.
Linda
Sadly-Linda has passed away 2022. She was the 311's den mother and drove the first Rare-Parts ball joint project. RIP.
