I’m fairly sure that small filter in the tube is a hydrocarbon trap and more than likely it’s designed with those gaps because the vehicle components are moving and you’re not going to see “that much” escaped air upon constant airflow going into the tube from that front bumper inlet. Removing the foam from the section that goes into the box won’t really benefit it in any way that I see. Even if you tape the area where the foam was the hydraulic area is not any larger. Taping the vents on the tube might be some benefit but probably not noticeable. I do find the opening flap on the bottom very interesting though. I had the whole front end and intake apart this past weekend and it was cool to see everything.

 

I'd guess the hole is gonna make a difference if water tries to get in there.

 

I think I saw this mentioned in some air intake comparisons and discussions. I do have to wonder if there is any zigzag section up front to help remove water before going straight into the filter box (a fairly typical arrangement); if not, the passthrough is probably for water to safely leave rather than entering the engine.

The gap between the scoop up front and the intake tube is almost certainly because the engine and attached airbox will move a bit and if that gap were bridged by something the material would probably fail quickly as it gets pulled and tugged.

The positioning of the light green foam doesn't look to me like it would be for hydrocarbons (at the intake? I sure hope fumes aren't sneaking out the front and I don't see what that little filter could do just on the side there) but maybe it is. I doubt it would hurt to try removing it.

 

OEM intakes are very good. Most aftermarket intakes are poorly designed and will pull in hot air from the engine bay. When you see an intake test being run with the car stationary with the hood open and a fan being aimed at the engine bay, you're not getting accurate results. That's not how aero works in the real world.

You can see how good/bad an intake is by just monitoring the intake air temp sensor and comparing that with the ambient air temp.

 

(I've also read that many gains from aftermarket intakes occur because of fooling the sensors into leaning the air/fuel mix and tend to give a rougher powerband.)

Probably a better intercooler (maybe with a homebrew GR-FOUR stencil haha) would help more.

 

I would always focus on making improvements after the MAF. on a Subaru, this was a turbo inlet, intercooler, intercooler piping.

 

anything you modify on the intake or exhaust side will change the overall airflow. i wouldn't really touch that stuff unless you have access to the ecu to monitor all the critical sensors.

this is especially true when you remove the stock cat on turbo cars. you've now made the turbo more efficient and the ecu may not realize the restriction was removed and automatically adjust how to control the wastegate.

 

absolutely. as time goes we will understand how much the stock ECU can learn with, or without a tune before things get dicey. people will toss a turbo inlet hose, intercooler, or replace the stock intercooler piping on the car, and pull logs to see if the stock tune can cope, then we'll know for sure.

there should be no question though, when you mess with pre MAF stuff you are absolutely changing how a critical sensor (the MAF) in the AFR calculation is going to read data. even if the diameter of the tube for the MAF housing is absolutely the same, if the way the air goes through that housing changes because the flow path ahead of it is altered, it will alter how the hotwire reads the flow.

 

The cage containing the foam looks like it would snap right out, increasing the duct area, but given the other intake it might not matter at all. No rain gutters in the grille scoop, so yes you'd need a bottom exit for liquids somewhere along the way to the airbox.

At the boost this engine is running compressor heat and intercooler efficiency are going to have the greatest effect on MAT, but every degree of IAT that goes in has to have an effect. Just thought it was an interesting setup on a car at a pretty high state of tune.

 

While I was in doing a horn install, I did an aluminum tape job on the OE intake holes and unsnapped the foam insert, to see if it affected anything. I left a slit at the bottom of the rear hole for water egress. I'm guessing I may get a little more noise and not much else other than knowing primary air is coming from outside the engine bay -some of the time-

 

I had another thought: the straight-through duct might also be sending more air in the general direction of the secondary air intake. From what I can tell based on a GR Yaris forum, that car has a scoop that sort of sends air towards the secondary intake underneath the airbox. Not sure if the GRC has that or not. Maybe one of the parts diagram whizzes can chime in.

GRY part:

ITG 'Maxogen' Cold Air Scoop

No affiliation but FYI, ITG have a cold air scoop for use with the factory air box. https://www.stringtheorygarage.com/product-page/itg-air-intake-scoop

www.gr-yaris.co.uk

PS notice any sound or performance differences? (Might need to be a hot day to notice any difference.)

 

Compounding that, the air box has a secondary intake that opens up to just above the transaxle at high rpm.

Is there any data saying this opens at high load or high RPM? I was thinking about this yesterday and we think the "hot air intake" would actually be better than cold air under certain conditions, but it should be during low load situations.

 

I don't know the control logic on the secondary air door. I thought I saw it written somewhere that it opened above 3000 rpm, but that seems low, and with todays ECU's its probably more complex than that.

Someone working on tunes could datalog the solenoid signal and give us an idea.

 

I don't know the control logic on the secondary air door. I thought I saw it written somewhere that it opened above 3000 rpm, but that seems low, and with todays ECU's its probably more complex than that.

Someone working on tunes could datalog the solenoid signal and give us an idea.

I looked in TIS and it opens the flap after 3600rpm. I wonder if we could disconnect the rod to keep it closed so it doesn't pull in hot air. Would be cool to see a dyno/IAT comparison to see if it is worth it.

EDIT: Apparently the flap does help according to Forge when testing their intake. So just going to leave it alone.

 

I did a test using an electronic thermometer placed inside the airbox with the supply tube removed. I was surprised that the temperature never got very high on the 75 degree day.

This was on a standard corolla, so no turbo, but it helped validate my decision to try a short air horn directly on the airbox.

I even let the car idle in the garage for a good while, hood closed, and it never reached a level that made me concerned about “hot air”.

I don’t recall the numbers, and probably won’t be repeating the test…

 

Looking at simple ducting from the lower door to over the radiator support. But there's not much area available next to the OEM snorkel under the radiator support cover, which will need to be cut for the duct to access air outside the engine bay. V3 might look at a combined duct entrance to maximize inlet area for both ducts. Something like the ITG Yaris unit linked in #12 above.

 

Looking at simple ducting from the lower door to over the radiator support. But there's not much area available next to the OEM snorkel under the radiator support cover, which will need to be cut for the duct to access air outside the engine bay. V3 might look at a combined duct entrance to maximize inlet area for both ducts.




View attachment 24464

A one off DIY or are you marketing it to the masses?

 

Just DIY tinkering, playing with the scanner and OnShape.
I've been looking at what's on offer for intakes and thinking about a cheap mod that truly excluded engine bay air to the OEM airbox. A work in progress, at this point I'm thinking a 3D print with an appropriate filament. I guess it would also be possible to print just the duct interior in vase mode and then wrap that core with fiberglass or carbon for a more durable or flashy item. If our cars were a high volume model a vendor could blow-mold them cheap.
TBH, I could of fabbed a working sheet metal duct in 1/4 the time I spent in CAD but it's a tool learning project for me.
My old printer has not been happy with the long prints, as I'm using up some iffy filament with poor layer adhesion.

The mock-up in the engine bay, I'm not cutting the radiator support cover yet:

This car has no datalogging fitted, so the best I'll be able to do is look at a dual channel thermometer, when the snow goes away.

 

My old printer has not been happy with the long prints, as I'm using up some iffy filament with poor layer adhesion.
View attachment 24474

The mock-up in the engine bay, I'm not cutting the radiator support cover yet:

What filament are you using? I've been having good results with PCTG (like PETG but higher impact resistance and less moisture absorption). Prints like PLA which is nice

 

I wonder, if rather than having some tape over the cold air supply (presumably to keep the colder air from outside just exiting into the engine bay), you could route the secondary intake to slot into the space that is taped off?

 

I think the existing primary intake duct/scoop would be too small to feed both ducts.

 

Judging by the folks dropping dollar$ on the Yaris duct, my 25 cent aluminum tape mod to the stock duct must be too low-rent.
The stock primary duct has a weird flow path anyway. So now there's a Primary duct in OnShape that omits the opening to under hood air.

I split it in two sections to fit my print bed with the least support material, but you could Boolean it back together with a few clicks.

 

Hope it doesn’t get sucked in!

 

Right now I'm using PETG, might try them in Nylon or ABS if it fails under the hood. Not a critical part, if they break I'm back to the factory warm air intake. I'll look into PCTG; there are so many materials available now...

 

FYI; The free OnShape online CAD service requires your designs to be Public, so if someone wants to use these (amateur) designs you can just sign up, search for GR Corolla and export them in different formats, or copy them and modify your copy. CawaGR's mini key fob is there also.

 

Im just here to buy one off you when ready lol

 

Sign me up!

 

Test fit of V1 on the car. OnShape file is now V2, which is a bit bigger to better match the scoop outlet and airbox socket.

I like the look of MST's V2 radiator cover/scoop combo for their air box, that maximizes the area from grille to airbox.

 

Thought maybe you put it up on another site but don't think this is the same as your is it? Didn't think yours required trimming.

2023+ Gr Corolla solid intake duct by kyle goerlitz | Download free STL model | Printables.com

 

It's too bad the V2 MST radiator cover isn't independently available nor does it look like the tanabe radiator plate include a ram air scoop towards the airbox.

 

V2 fits the scoop better, and has a larger cross section at the airbox. You can print yourself a red one if you want. I used 1mm foam tape at the airbox for a gasket.