Do custom snorkels cause the engine to run lean?

ALMOSTunseen

ALMOSTunseen

Forum Member
Joined
Jul 17, 2014
Messages
279
Location
Sydney, Australia
Car Year
2010
Car Model
Forester XS
Transmission
5MT
Went looking for a snorkel to fit to the subie today and got chatting with one of the guys at TJM.
He said that with some custom snorkel jobs at freeway speeds the ram air effect is too much and can cause the engine to run lean and also to screw up fuel efficiency.

Is this true and would a custom tune(most probably a dyno baseline tune then a road one so MAF reading can be acquired at freeway speeds) be able to tune out this sort of issue with the increased air flow?
 
Maybe if the engine was carby or running an archaic LPG system, but I cannot see this event happening with modern EFI's.

Subaru uses a MAF sensor . It measures the CFM or mass of air that passes by the sensor and outputs the actual flow of air to the ECU so it calculate and deliver the matched spark, timing advancements and fuel requirements.

Problem is the standard stock Subaru tune is garbage :lildevil:. Worldwide problem, been around since the inception of the wrx, bottom line cause is detonation. There is that word again!!:ebiggrin:

Best mod you will do is getting your stock ECU tune, re-tuned if possible on a dyno but that's my preference.

Goodluck
 
Some people run their snorkels with the intake facing rearwards - I wonder if it's in response to the same problem.
 
Yeah catchya definitely due for a tune.

tweak,
I have read this apparently for some it's a difference in a few l/100km ....
Will try and get to a car graveyard this week and see if I can find a snorkel that fits cheaply.
 
Tweaksta said:
Some people run their snorkels with the intake facing rearwards - I wonder if it's in response to the same problem.
Click to expand...

Rearward facing is usually to minimize dust intake or to stop snow compacting in the snorkel head.
 
I think what a lot of people under estimate with the fitment of a snorkel is how differently they drive. That desire for some induction sound sees the loud pedal being pushed that little bit further for more :ebiggrin: action.

Seriously though, there are many other factors to consider too - you're increasing the intake length before the throttle body. Car manufacturers put in a lot of effort to get the best all round efficiency from the intake tract leading to the throttle body. We're messing with this.

I've often wondered if my snorkel setup would benefit with a 2 or 3 litre box prior to the air filter box similar to the stock setup - but that would almost make my snorkel impossible to work with the space I have.

AlmostUnseen, I don't know what subi you have, but look into the NK NH NG Pajero snorkel. The elbow will need bending but it seems to be the best all round snorkel for the subarus. Mine's on an L series and it fits VERY well!

7NX5OT.jpg


With a little effort you can adapt something to your vehicle. The trick is knowing or finding what that something is and a willingness to have a go. Hardest part is cutting the hole in your guard...

Cheers

Bennie
 
El_Freddo said:
I've often wondered if my snorkel setup would benefit with a 2 or 3 litre box prior to the air filter box similar to the stock setup - but that would almost make my snorkel impossible to work with the space I have.
Click to expand...

the box pre-filter is simply a resonator aka muffler to drown out the intake noise as most mainstream car buyers want a quiet car. It is not there for performance.
 
Thanks for the heads up on what snorkelling to use, I have a SH forester.
I will be modifying the stock airbox so I will essentially have what is called a "hybrid" intake where I use components of the stock box and stock airfilter and then route my snorkel to it.
 
Gas dynamics is a very complex subject!

When using a gas fired ceramics kiln that is going to run off the reticulated gas supply, every single bend and run length needs to be taken into account. A kiln gasfitter licence is quite separate from that required by a normal gasfitter. A kiln gasfitter will usually hold both licences.

Our advice from both our kiln gasfitter and normal plumber/gasfitter was that it was better by far to run our 8 cu.ft. gas kiln off bottled gas because of this complexity. Bottled gas is at a far higher pressure initially, and the pressure to the burner can easily be adjusted. This is a very different kettle of fish with town gas.

Town gas is not unlike our intake flow in a N/A engine. It is at relatively low pressure, so the tuning of the intake manifold is of crucial importance, as Bennie has already mentioned.

IMO, having a tune done once you have finished all the works is as essential as having a wheel alignment after doing suspension work.

Just FWIW :poke:.
 
I've learnt that cars are not new technology! Every dynamic in them traces back to somewhere.
What I will try and do:
1. Baseline Dyno run with Snorkel with no tuning.
2. Dyno tuning with snorkel.
3. Road datalogging and tuning if necessary to see how the ram air affects the AFR at higher speeds.
 
This thread and the links in it would be a good read for you and your snorkel fitment ;)

Cheers

Bennie
 
Thanks, very helpful. At the bottom of my resonator there is a small hole for water drainage, will probably put a one way valve there.
But for now I just need to plan how to get my tubing into the airbox. Currently there is a square hole. I'm thinking of drilling it out, ramming the 3"(or whatever size works best) tubing in, and stuffing it full of sika.

Does anyone have photos of Mr.Turbos install since the photos aren't there anymore.
 
Last edited:
Personally I'd prefer the silicon only as I think it's more durable and resistant to heat damage. It's harder to work with though!

Nachaluva will hopefully chime in with what he used. Mine is a combination of metal elbow and silicone pipe. I need to get back and mod that elbow some day to make it smoother.

That flexi stuff looks alright to me. A snorkel is about a water tight air intake that you don't have to worry about when doing water crossings ;)

Cheers

Bennie
 
Yeah I don't know if there is a specific product for sealing joints but I will probably just pack each joint with sikaflex/silicone sealant and make it semi permanent.
 
You must log in or register to reply here.
Back
Top