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Posted (edited)

I put this in the "turbo" section cus I didn't see any other appropriate place, but it probably applies to the turbo somehow.

 

I have a 1978 280z with an '82 L28ET engine. It is stock everything except for an added oil cooler. I currently have a SUPER DIRTY K&N air filter that sits in front of my radiator via some custom piping. I think the previous owner put this on in 2004 and hasn't changed it since, so I decided I would just get a new one rather than try to clean it (see below).

 

c4ox70C.jpg

 

I found the current filter online: https://www.knfilters.com/search/product.aspx?prod=RE-0910

 

RE-0910_Dim.jpg

 

However, I found a very similar but slightly larger filter below it: https://www.knfilters.com/search/product.aspx?prod=RE-0810

 

RE-0810_dim.jpg

 

The second filter is about an inch longer and an inch wider at the base. However, it will definitely fit in the current space, so it would be very easy to swap to this size.

 

Is it worth it to buy the slightly bigger size? Are there performance benefits/downsides, or will I not even notice this small of a difference?

Edited by AlbatrossCafe

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I think bigger is better until a certain point where it is adequately large enough and won't make a difference.  A bigger filter might perform longer before needing cleaned/replaced?

 

The guys on Engine Masters tested all kinds of air filters and what they found in a different scenario (domestic v8 with a carb) is that the turbulence in the filter has more effect on performance than anything. They found that a funnel or bowl shaped (velocity stack type) shape really helped performance.  It is an interesting watch: https://www.youtube.com/watch?v=EkpsydS8JXI 

 

 

 

 

 

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Interestingly NA's actually requite larger filters than force fed motors. I had a table listing what minimum size your filter needed to be for a given hp for both NA and turbo engines, I will post it if I can find it.

 

 

 

If you can fit a filter with a v stack it makes a big difference. 

 

DSCF6966.jpg

 

 

 

 

DSCF6959.jpg

 

 

 

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Posted (edited)
9 hours ago, grannyknot said:

Albatross, I have this one for sale, K&N filter RE 0800, I used it for one season 700 kms, just as you see it in the pic, perfect working condition, 3" ID, 6" wide, 12" long, $50  The pics are here, https://www.kijiji.ca/v-view-details.html?adId=1320806789

 

 

Sorry, it is a bit too long. It wouldn't fit for me. I can fit <6" width filters and <10" length filters with 3" ID flange.

 

I'm looking at this AEM one which is basically the same dimensions as current but a dry filter instead of oiled: https://www.aemintakes.com/search/product.aspx?Prod=21-2038DK#reviews

 

Or this one which has the shape that @EF Ian was talking about but is a bit smaller (5 1/2" height vs 8" height): https://www.aemintakes.com/search/product.aspx?Prod=21-203D-XK

 

Do you guys think #1 or #2 would be better? My only concern about #2 is that it is too small for some reason, but it may let in more airflow than #1 because of the space on top. Or am I just better served getting something else entirely? e.g. like this generic fleaBay filter

Edited by AlbatrossCafe

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Posted (edited)
2 hours ago, grannyknot said:

I was reading up on this new material they are using for some air filters now, EaAU sounds very promising but there is not a lot info that I could find. https://www.amsoil.com/shop/by-product/filters-and-by-pass-systems/air/amsoil-ea-universal-air-induction-filters/

 

Thanks for the link! I'll take that chance. I didn't want to buy K&N (heard they don't filter well) and was still sorta against AEM since they were bought out by K&N around 2010 (I'm sure it is fine, but still hesitant).

 

Don't know why that site lists the Amsoil part # right next to the K&N part # (maybe for comparison?) but as far as I know Amsoil and K&N are still different companies.

 

Decided to go with Amsoil's EaAU3090 filter which competes against K&N RE-0810    . This is just an inch larger than my current one but also has the "V-stack" concept that EF Ian mentioned so it should have more than enough surface area/airflow.

 

Amsoil:AMSOIL Ea Universal Air Induction Filters: AMSOIL Universal Air Induction Filter: 1 FILTER Product ImageK&N:RE-0810_Alt.jpg

 

I figure if it is too big, what is the worse that could happen? Will it run too lean? Just seems like the extra space will make it last longer before cleaning...

Edited by AlbatrossCafe

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21 hours ago, AlbatrossCafe said:

Don't know why that site lists the Amsoil part # right next to the K&N part # (maybe for comparison?) but as far as I know Amsoil and K&N are still different companies.

I think the point is when you finally get tired of having the upper half of your engine sand blasted by K&N you just look up the K&N part # and there is the Amsoil filter.   Amsoil and K&N are very different companies.

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On 4/18/2018 at 1:34 PM, EF Ian said:

Interestingly NA's actually requite larger filters than force fed motors.

 

I'm with TimZ here. Does not compute for me. Care to elaborate or point to your source?

 

Intuitively, the air filter shouldn't care whether it's filtering 600hp worth of NA or forced induction airflow. If the filter were AFTER the turbo, then the volumetric flow would be lower for the forced induction setup.

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Posted (edited)
On 5/8/2018 at 12:20 PM, SleeperZ said:

I'll out on a limb and say that N/A engines seem more sensitive to pressure drops across the filter since the engine only has 1 atmosphere to operate on.

The turbo has the same issue, though.  The lower the inlet pressure is for the turbo, the harder it has to work to supply a given amount of air, and the less efficient it will be, so more heat will be created.

Edited by TimZ

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2 hours ago, TimZ said:

The turbo has the same issue, though.  The lower the inlet pressure is for the turbo, the harder it has to work to supply a given amount of air, and the less efficient it will be, so more heat will be created.

 

Yes, more heat will be generated, but the intercooler will still take most of it out, and the boost pressure is regulated.  Net result should be less effect on a turbocharged engine vs. N/A.

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1 hour ago, SleeperZ said:

 

Yes, more heat will be generated, but the intercooler will still take most of it out, and the boost pressure is regulated.  Net result should be less effect on a turbocharged engine vs. N/A.

Ever noticed the difference on a turbo engine's response on a 70 degree day vs a 90 degree day?  It's the same effect.   Low density air at the compressor inlet causes heat and lag.  This is the same argument that people use to justify spending money an a "cold air" intake that draws hot air from under the hood - it's a poor argument there too.

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Doesn't the heat come from compressing the air?  More air to compress means more heat.  The turbo only "works" on the air it sees.  Less air = less work.

 

Overall though, this is kind of a goofy topic.  The pressure drop will increase with air quantity, flow, right?  Besides that, engines don't really require anything.  Not even sure what "require" means here.  You have to define objectives before you can define requirements.

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Posted (edited)

same output pressure with less air at the inlet = more work/less efficiency.  

 

I'm only making the argument that the issue isn't different for turbo engines.

Edited by TimZ

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15 minutes ago, TimZ said:

same output pressure with less air at the inlet = more work/less efficiency.  

 

I'm only making the argument that the issue isn't different for turbo engines.

 

I totally understand.  I am merely suggesting that there may be a basis for the perceived difference.

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On 4/17/2018 at 8:51 PM, AlbatrossCafe said:

Is it worth it to buy the slightly bigger size? Are there performance benefits/downsides, or will I not even notice this small of a difference?

 

Probably could have just said "no" and "no".  There are most likely much more effective ways to maximize air flow and minimize pressure drop.

 

As far as the K&N effectiveness issue, I just saw this on another forum - do the white glove test on the inlet piping after the K&N.  See what's making it through.  A white paper towel or cloth will probably do.

 

I took off the inlet pipe on a vehicle I recently bought that still had the K&N sticker on the housing.  The PO to me had already replaced the filter with a paper element.  I was shocked at the amount of fine dust I found inside.  It coated everything.  It was so bad I'm not even sure that the filter housing was properly sealed.  It's a Ford truck with the big clamp that often gets cocked or screwed up.  I'll never know for sure.

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Welp, regardless, it's too late now. It barely fit. I had to remove my oil cooler from it's mount to put it on.

 

I'd say "For the next one, I'll go back to the smaller size" but given that this car will be driven ~2000 miles per year, I couldn't tell ya if there will even be a next one...

 

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49 minutes ago, grannyknot said:

@AlbatrossCafe, is that the Amsoil EaAU air filter we were talking about?  Very interested to hear what you have to say about it.

 

Sure is. Got it here: https://www.amsoil.com/shop/by-product/filters-and-by-pass-systems/air/amsoil-ea-universal-air-induction-filters/

 

Though TBH it won't be much of a review... I bought my Z last fall, put about 60 miles on it driving it home, took off all the suspension, and it has been on jackstands ever since waiting for coilover parts to arrive and welding to be done. So I don't really have a benchmark to judge it against haha

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As a rule of thumb the filter flow, in cfm at standard pressure drop, should be ~1.5x the hp it is supporting.  This means for 500hp you want a filter to flow 750cfm.  That doesn't mean you can't make the same hp with a smaller filter, but you will have a higher pressure drop.  Whether turbo or NA, pumps don't like restrictions on the suction side.  K&N doesn't list flow numbers on their site, but if you call they will provide.

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