FK8 Intake Tube Purge Jet

[elmerzasty]

As for the charge pipe, there is no provision for a hose in mine. Finding a cap that can withstand 20+ psi of boost might be difficult. Most automotive rubber caps are suitable for vacuum.

I am not sure that I follow the idea behind this whole thread, but if you were referring to plugging the EVAP hole in the intake elbow, then that part of the intake is not pressurized, there is not boost there, just vacuum.

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[ineedahonda]

I am not sure that I follow the idea behind this whole thread, but if you were referring to plugging the EVAP hole in the intake elbow, then that part of the intake is not pressurized, there is not boost there, just vacuum.

The goal of the thread was to get some help from another FK8 owner not in the US to see if I could get the part numbers for the different purge valve setup. We are also talking about capping the barb on the stock cold side intercooler piping.

 

[elmerzasty]

The goal of the thread was to get some help from another FK8 owner not in the US to see if I could get the part numbers for the different purge valve setup. We are also talking about capping the barb on the stock cold side intercooler piping.

OK, got it. But what's wrong with the US EVAP system in the first place?

 

[shadow]

OK, got it. But what's wrong with the US EVAP system in the first place?

ineedahonda's reasons are in post #9 of this thread.

 

[Fk8_tuning_development]

The hose connects directly to the cold side charge pipe. The other is a vent with a one way valve that vents excess tank pressure into the intake. The hose coming out of the charge pipe can be blocked off with a cap. The other hose needs to be able to vent tank and evap system positive pressure from temperature changes. I can not currently be 100 percent sure blocking the vacuum line coming off the charge pipe won’t effect fueling because it dumps directly into the Intake hose. The valve on the intake does the actual have an internal valve. It just regulates how much air can travel back through its internal size.

Theoretically you can eliminate it but I’d watch what happens to your fuel trims. The only small benefit might be a tiny bit of extra boost capability from not bleeding off. It is a very small hole.

 

[Fk8_tuning_development]

The one marked in blue is fed boost directly from the charge pipe. Blocking it off could cause delay in response of fueling because under vacuum some of air will be drawn from there instead of all the air going through the turbo intercooler and piping first.
The yellow is an evap dump hose. The intake box can’t draw vacuum pressure so disconnecting this will have no effect but it must be able to remain open or you get an evap code. There is a one way valve further back that prevents boost pressure from going into the evap system.
The one way valve is under the engine cover.
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Forgot to add here’s the one way check valve part. You could put a one way check valve on the boost pipe to allow vacuum but not boost to be leaked but it’s so small I doubt it’s advantageous.
Honda part number.
361455MSH01

 

[ineedahonda]

The hose connects directly to the cold side charge pipe. The other is a vent with a one way valve that vents excess tank pressure into the intake. The hose coming out of the charge pipe can be blocked off with a cap. The other hose needs to be able to vent tank and evap system positive pressure from temperature changes. I can not currently be 100 percent sure blocking the vacuum line coming off the charge pipe won’t effect fueling because it dumps directly into the Intake hose. The valve on the intake does the actual have an internal valve. It just regulates how much air can travel back through its internal size.

Theoretically you can eliminate it but I’d watch what happens to your fuel trims. The only small benefit might be a tiny bit of extra boost capability from not bleeding off. It is a very small hole.

Thank you that is all great information!

 

[turbociv910]

Its called a purge jet.. uses a tiny amount of air using the venturi effect to help pull more evap vapors in. The solenoid has to be open signal from the ecu. If you want to delete it, feel free to delete it. the ecu has no way of knowing if its hooked up or not if you vent to atmosphere. Only bad thing is that every aftermarket mfg makes parts to use it, so you have to be custom like me.

The one marked in blue is fed boost directly from the charge pipe. Blocking it off could cause delay in response of fueling because under vacuum some of air will be drawn from there instead of all the air going through the turbo intercooler and piping first.
The yellow is an evap dump hose. The intake box can’t draw vacuum pressure so disconnecting

delay in fueling? the car is a mas air flow.. the air has already been accounted for. that small little tube of air is in the same atmosphere as the rest of the intercooler piping system the engine is pulling from.. ecu doesent care where it came from..


the intake box DOES draw vacuum when i logged it with a motec pressure sensor. You have to be moving and it is a pressure. Sitting still on a dyno is the worst environment for the cars airbox.. specially with the hood shut.

 

[-JP-]

Thanks for the info. Not necessarily wanting to delete the evap system. But I’ve noticed factory cars with and without the valve and wondering if it can be done on the US cars. I do have Hondata. Recently got the PRL silicone intake pipe and have struggled a bit with the top vac hose on the purge valve rubbing on the hood. Plus it looks cleaner without the valve.

Rotate your tube back a couple of degrees. It will bring the valve down and provide clearance for the hood.

 

[ineedahonda]

Rotate your tube back a couple of degrees. It will bring the valve down and provide clearance for the hood.

Thanks JP. I actually spun the valve around 90 and trimmed the vacuum lines a bit. Works like a champ. I had seen a few other folks do that as well. Looks a bit cleaner IMO.

 

[Fk8_tuning_development]

Its called a purge jet.. uses a tiny amount of air using the venturi effect to help pull more evap vapors in. The solenoid has to be open signal from the ecu. If you want to delete it, feel free to delete it. the ecu has no way of knowing if its hooked up or not if you vent to atmosphere. Only bad thing is that every aftermarket mfg makes parts to use it, so you have to be custom like me.



delay in fueling? the car is a mas air flow.. the air has already been accounted for. that small little tube of air is in the same atmosphere as the rest of the intercooler piping system the engine is pulling from.. ecu doesent care where it came from..


the intake box DOES draw vacuum when i logged it with a motec pressure sensor. You have to be moving and it is a pressure. Sitting still on a dyno is the worst environment for the cars airbox.. specially with the hood shut.

At low rpm there is always a delay with MAF fueling cars when you snap or press throttle rapidly at lower rpm. Datalog below shows how the ctr is effected at different rpm and different set ups It is worse at lower rpm. A Roots style supercharged camaro forces mixed ve and MAF fueling until 4000rpm. At this higher rpm there’s less of a delay if any. Using totally stock blower. Using a bigger intercooler at the low rpm the delay is worse.
Not dangerous normal people cant feel it usually even if it gets lean to drop power. Snap the throttle and watch your stft and afr. Stft go positive trying to compensate.

People who try to tune cars solely off MAF experience an even larger spike. You see a bad 1/2-1 seconds lean spike on cars even though the distance is far less then turbo car. Yes custom tuning shops actually tune fuel MAF only on open loop MAF cars and it’s poor practice.

Typically open loop tuning you can not go full MAF fueling until at least 2500rpm.
On lsa engine even with the MAF housing 10 inches away from the throttle plate it will spike 16-18afr and actually misfire as high as 2500rpm when suddenly opening throttle plate. . It’s tuning the (easy/amateur) way out. Not even half throttle will cause it. Guys throw positive displacement supercharger on chevys and use the MAF scaling only to correct the fuel and call it custom tuning. You ought to see the ridiculous bogging delay.

Volkswagen MQB platform moves the mass air sensor into the cold side charge pipe right before the manifold for this very reason. MAF function is more accurate the closer you get to the throttle plate.

I wish we had throttle enrichment tables, PE tables and or real VE table access. It’s not harmful but this is how anal I am about tuning. The manufacturers don’t care obviously cause a stock tune does it.


Yeah I’m anal about crap being perfect sorry can’t help it. I’ve always covered all basis no matter how stupid or insignificant they seem. I’ll always make it as perfect as possible.

2000rpm full throttle stock turbo car 5 percent trim increase spike 17.17 even threw off commanded value.

5000rpm full throttle no spike trims actually went negative this testing is my current combination. and at this afm v is typical

Garret turbo fk8 2100rpm 4 percent increase 16.44 afr Vs commanded 14.7 see both garret spikes show multiple spikes but it’s actually one longer spike.

Garret turbo 2000 rpm fuel trims jump 10 percent and stop actual afr was 15.64 and commanded 14.7. Both lean spike ls are the ecu trying to compensate. It’s technically one lean spike.

Again not harmful but mine did get worse when I clamped it off but it’s very short lived. If you don’t look no one will ever notice it or feel It. It only took the ecu .700-.900 of a second to recuperate most of the time. Essentially 3/4 of a second. Typical is .700-.900 of a second below 3000 rpm and is corrected by the time greater than 2 psi is achieved. 2000 rpm can take up to 1.5 seconds and 2.7 psi. MAF scale changes don’t change it.

Separate note.
I’d love to do what bmw guys do and move the iat from the MAF horsing into actual flow not getting artificially heated. Wrapping my MAF housing can’t actually create a real 10 degree difference there ls not enough time for the air to absorb that much heat traveling through the MAF housing.

 

[shadow]

If anyone wants to learn how the EVAP system flow, here it is from the FSM.

Non-USDM cars do not have non-return valve A and merge point 2. Wow triple negative in that sentence.

 

[turbociv910]

Yeah I’m anal about crap being perfect sorry can’t help it. I’ve always covered all basis no matter how stupid or insignificant they seem. I’ll always make it as perfect as possible.

But you cant without fuel film. its physically impossible without port injection. With direct injection, There is no film of fuel on the inlet runner to be sucked in with a quick throttle blip.

Wall wetting, fuel film, what ever you want to call it. Throttle cracker if you ever actually tuned hptuners.

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