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Since I live in what can be a very hot climate.....I've been wondering if the stock air filter and snorkle would be a better way of taking in air (COOLER) than the carb mounted air filter that came with my car (weber). I see that they sell an adaptor but I'm not sure if the stock filter and housing are too restrictive.

OR... should I just wait till I have time and make a cold air induction like I've seen on here??? Are they a LOT more efficient than the stock set-up? My engine is stock with a 32/36 DGEV and 2 inch exhaust.

Any thoughts appreciated.
 

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Bosco, cooler air going into the carb is always more efficient than hot air. It equates to more dense air, pulling in more fuel, and expanding more when combustion takes place. If you ever noticed that your car runs a little better when it's been raining, it's because of the more dense air charge going into the carb. HTH.

Ron
 

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Weber DD / Original Air Cleaner

There are two Weber carb. to Opel air cleaner adaptors - one is slightly shorter than the other. The tallest one has a wee Weber "W" cast on to its top face. The shorter one is best for GTs.
Also the Opel bit that fits on to it needs slight shortening to fit under the hood.

There is also a K&N air filter available for the original filter housing - though there are two types of housing as well. The earlier one has a fixed steel mesh filter element that requires a bit of "butchery" to remove before the replacible filter element can be fitted while the later type already has a removable paper element. The original element is quite large and suitable for performance use though the K&N replacement is generally considered superior.

RE: cool rainy days - the water droplets in the air also have an effect much like water injection, slowing combustion. While the cooler air is more dense, allowing a greater amount per cylinder full.
 

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I was doing a little thnking last night about this and using my USAF training and a little bit of basic physics, here's a thought. If you're going to use a cold air intake, do not use a symetrical tube, ie., same inside diameter front to rear. Make it 1/2 the diameter of the final diameter at the outlet. Here's why, and you can check it by looking at OEM snorkels, if you rapidly expand air, it will drop in temperature, so a small inlet and a large outlet = cooler air. This system is used in aircraft, both commercial and military to cool the inside of the aircraft. It consists of a "Air-Cycle Machine" or a "Boot Strap Turbine", both work the same way, just different names. High volume air from the engine compressor bleed port is forced through a tube, about 3-4 feet long that is about 1" inlet diameter and 6" outlet, this air drops from about 200 degrees to subzero temps. There is a mixing valve that mixes hot and cold air to the desired temp down stream of the ACM. It really works because there is no freon system on these aircraft. Need more proof? Take the valve core out of a fully serviced tire, if you are in a high humidity area, ice will form on the valve stem as the high pressure air rapidly expands as it leaves the tire. JMTCW.

Ron
 

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Hmm. I would have to go back to the Thermodynamics books from University Engineering days, but it don't work that way. Something about enthalpy and entropy. And PV=nRT. And adiabatic expansion (versus isentropic expansion, but that's a discussion for a turbo-expander group). But in short, air expanding due to a pressure drop might cause some minuscule amount of cooling, but the same pressure drop will ensure that LESS (not more) air is available for combustion. Otherwise, you'd just block off the air intake, save for a nice small hole. Sorry Ron, but a nice, big fat air intake pipe, with a low pressure-drop filter, will provide more air for combustion than a factory, reducing diameter snorkel. I think that design has more to due with intake noise than breathing efficiency.

JM2CW
 

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Actually Keith, the full bonnet type filter can is what quiets the induction noise. Take it out and put in a full circumferential open filter and the induction noise is very pronounced. Or just take the lid off, turn it over and you get the same noise but quieter. Without getting in to a urinary confrontation, here's what I know for fact. On the Blackbird, air conditioning and pressurization is taken off a 6" hole in the side of the intake, if front of the engine compressor. During the flight the intake air temp is about 450 degrees. This air passes through an air to fuel primary heat exchanger where it COOLS the fuel for engine use, if the fuel is still too hot, it is routed back to the fuel tank to be recycled for additional cooling. Then the air goes to the secondary heat exhanger where the Air Cycle Machine is. The exhaust air temp from the ACM is -40 degrees and has to be heated up to be used in equipment cooling and pressurization to the cockpit and flight crew, full pressure moon suits. The same type of system is used on commercial aircraft, but they use compresssor bleed air to heat up the air prior to going into the cabin. The difference between the two types of aircraft is the commercial aircraft operates in -65 degree air temp. The Blackbird creates skin temps of up to 1200 degrees. One thing that may make a difference is I'm referring to very high volume air flow in aircraft. Enough flow to maintain a 6 psid over ambient outside pressure in a cockpit, or to maintain a cabin altimeter reading of 8,000 when the aircraft is at 30,000 feet or more, and have continual air flow through a huge cabin pressure regulator and dump valve that would be as large as man-hole cover.

Ron
 

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Discussion Starter · #9 ·
I was just trying to find out if a weber adaptor for the stock box and snorkle, with a K&N inside, would work sufficiently or if I would be MUCH better off to construct my own cold air intake, similar to Opelenvy.
 

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Has anyone tried these K&N remote adaptors using the original air filter canister and hose? If so does the original accordian hose fit well? I'm looking for more original appearance than performance. Also I'm guessing that having the original filter in-line would protect the engine a bit better than the top mounted filter. I'm running a 32/36 DGV on a block bored 2.0.
 

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Just so you know, I took the Jam Engineering one off my car. It was too restrictive. I didn't run any fancy tests, but I had a stumble with it, and not without it. I currently just have a filter that sits on top of the carb again.
Unfortunately I sold my stock setup with the K&N in it. :(
 

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opelenvy said:
Just so you know, I took the Jam Engineering one off my car. It was too restrictive. I didn't run any fancy tests, but I had a stumble with it, and not without it. I currently just have a filter that sits on top of the carb again.
Unfortunately I sold my stock setup with the K&N in it. :(
I certainly not an expert but could the combined length of the hose and snorkle have caused the restriction? Did you test run with just the adaptor in place?
 

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oldroadiedog said:
Did you test run with just the adaptor in place?
I did test it with every variable. with/without filter, with/without snorkle, just the adapter(which mine has a 1/2" riser). It still did it. I used my die grinder and opened up the opening some and I noticed an improvement, but still a slight stumble. I could open it some more, but I am trying to get something that works better than the stock setup. Right now I am just trying to make it as good as stock. Why reinvent the wheel?? :confused:
Haven't had a lot of time to mess the the Opels lately, so I kind of just dropped the project for now.
Rallye Bob said he was possibly going to be working on one. :cool: :D
I can wait.
 

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Of course the OEM set-up was a much smaller carb and probably designed to work as well as it could with the OEM canister and hose. As I said earlier I'm willing to sacrifice a little performance to get the look. Good grief - mine is an automatic anyway! :p
 

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OEM - Hard to Beat

Back in 1968/69 when GTs were new there was an extensive test of varrious replacement air cleaners (No - "Pod" filters had not been invented then ...).
The testers found that the OEM set-up with the oiled mesh filter gave significantly more and smoother power than anything else ..........
Something to do with Stutgart University doing air flow analysis on the stock setup while they had the GT there in the University wind tunnel for aerodynamic testing. The later paper filter element upgrade to the OEM system is reputed to be even better and a K&N replaceable filter in there is just the icing on the cake! Of course the stock system draws most of its air from infront of the radiator bulkhead in the cooler, higher pressure area inside the nose cone - getting the idea that Opel actually did a bit of testing on this system ??? Anything we can "throw on" is only likely to be WORSE than the factory set up .... ;)
 

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I did some “seat of the pants” testing using a few different air-filtering setups with a Weber 38 DGES carb. My un-scientific results are what I experienced over about a week of trial and error.

Cold air package with unmodified Jam engineering snorkel. - It’s nice looking but very restrictive at mid to high RPM range.

K&N filter on top of carb. - Non-restrictive with good throttle response and power thru out the RPM range until the engine bay heats up, especially in traffic.

Stock setup with Weber carb adapter and paper filter, Less restrictive then the Jam Engineering package, more restrictive then the K&N filter on top of the carb but it’s cold air all the time so no noticeable change due to engine bay heat.

Stock setup with Weber carb adapter and K&N filter. - Basically the same as with a paper filter but a little better at higher RPMs probably due to the less restrictive filter.

Cold air package with modified Jam engineering adapter and snorkel and K&N cone filter. - By far better then any other setup i tried, non-restrictive cold air all the time. The engine breathes as if there was no filter setup.

Bottom line is like GTJIM said the stock setup with a better filter is hard to beat without modifying existing parts or making your own :) .

I don’t have a picture of a before shot but here is an after shot looking thru the modified Jam snorkel.

hth
Brian
 

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So here's what I ended up with. Thanks to OpelEnvy for selling his K&N adaptor to me. The replacement accordian hose came from OGTS and I used the original clamps. I had two problems to solve though. The hose is 3" and the adaptor is 2 1/2". To get a tight seal I cut a lenght of small diameter vacuum hose to wrap around exterior of the intake of the adaptor and act as a spacer. To splice the ends togeather and create a large "O" ring I cut the head off a small bolt that fit tightly inside the each end of the small hose. The other problem is unresolved at this time. The automatic transmission dip stick knob is being squeezed between the adaptor and the hood latch mechanism. I'm hesitant to try and bend the dip stick tube slightly one way or the other but it will be a pain to remove the adaptor to check automatic transmission fluid level.
 

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Looks good oldroadiedog. Now who wants the rest of my setup??
The 3/4" spacer made by JAM, and the rest of the setup are now for sale as well.
PM me if you are interested.
 

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What are you running now?

opelenvy said:
Looks good oldroadiedog. Now who wants the rest of my setup??
The 3/4" spacer made by JAM, and the rest of the setup are now for sale as well.
PM me if you are interested.
Absolutely! Refresh my memory, George, after all the time you spent "getting it right", why'd you sell it? Oh yeah, what are you running on yours now . . . adapter and modified "stock" snorkel and air filter? :confused:
 
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