Subaru Ascent Forum banner
1 - 20 of 34 Posts

·
Registered
Joined
·
180 Posts
Discussion Starter · #1 ·
I wanted to give this stuff a try. Does anyone know if the brake booster vacuum line feeds from 1 cyI or from both sides of the manifold? I.e. If I use the brake booster as my entry point for the valve cleaner, will it only clean 1 set of valves or will it get to all of them?

I understand we'll still have to do walnut blasting at some point but figured this should help a little.
 

·
Registered
Joined
·
1,182 Posts
I'm thinking maybe the brake booster doesn't use vacuum from the intake manifold on a turbocharged engine because at times it would definitely be positive pressure rather than vacuum. I could be wrong on that.
 

·
Registered
2020 CWP Touring
Joined
·
1,284 Posts
I just looked at my 2020 model and it looks like there may be a mechanical vacuum pump driven off the intake camshaft on the right cylinder head (left side as you face the engine). That's very near the end of the cam cover, and there's not a matching "extension" below it (where the exhaust cam would extend), suggesting that this is something bolted to the cam cover running off the intake camshaft.
 

·
Registered
2020 CWP Touring
Joined
·
1,284 Posts
Ahhhh thank you, so if I put the CRC in there.... it'd go into the crankcase. right?
I'm not sure, not without more information about where everything from that vacuum pump goes. It's listed as part of the EGR system on that parts website. EGR-related items are generally not plumbed to the crankcase. And we know the brake booster in this case isn't (it runs straight from the vacuum pump to the brake booster). But I don't know if there are other components attached to that vacuum pump that do go to the crankcase.

In any event, you don't want the CRC in the crankcase, right? You'd want to get it into the intake manifold if you could. I would be surprised if there's not a port somewhere for top end cleaning service. For example, many dealers offer a fuel injection service -- I wonder what they do for that on the Ascent.
 

·
Registered
Joined
·
81 Posts
You should be using the GDI IVD spray cleaner.


Technically, I'm not comfortable spraying through the turbocharger (according to their instructions), then has to work through the intercooler to eventually make past the throttle body into the intake manifold
 

·
Registered
Joined
·
180 Posts
Discussion Starter · #12 ·
I'm not sure, not without more information about where everything from that vacuum pump goes. It's listed as part of the EGR system on that parts website. EGR-related items are generally not plumbed to the crankcase. And we know the brake booster in this case isn't (it runs straight from the vacuum pump to the brake booster). But I don't know if there are other components attached to that vacuum pump that do go to the crankcase.

In any event, you don't want the CRC in the crankcase, right? You'd want to get it into the intake manifold if you could. I would be surprised if there's not a port somewhere for top end cleaning service. For example, many dealers offer a fuel injection service -- I wonder what they do for that on the Ascent.
Yes definitely NOT in the crankcase, it will dilute your oil.

Is it not really that easy to do this. There should be a port in the intercooler or intake manifold directly after the TB where you can spray something like this. It may be that there's some vacuum line you can disconnect to get access, I haven't looked that carefully.

On my other car I have water/methanol injection, I have a 1/8 NPT port directly above the throttle body, but I do not want to risk voiding my warranty on new Ascent.
 

·
Registered
2020 CWP Touring
Joined
·
1,284 Posts
Why not use a fuel additive for intake valve cleaning? I use Sea Foam. I also use Chevron with Techron. Techroline is a good cleaning detergent additive.
Fuel additives are not effective at intake valve cleaning with traditional direct-injected engines because fuel is injected directly into the combustion chamber. Some direct injection systems also have upstream fuel injectors that supplement the primary fuel injector, for the purposes of reducing deposits in the intake system. I don't think the FA24 engine has such a system. Meaning...any cleanser or detergent added to the fuel goes straight into the combustion chamber and does not help keep the intake tract and valve heads clean.

I don't know how much of an issue this is going to be in our engines in practice (intake system deposits), but the direct injection system design is why in-fuel detergents are not effective for this.
 

·
Registered
Joined
·
731 Posts
Why not use a fuel additive for intake valve cleaning? I use Sea Foam. I also use Chevron with Techron. Techroline is a good cleaning detergent additive.
Because that doesn’t do anything on Subaru DIT engines for valve deposits.

Anyway, supposedly our FA24DITs have a “new for the FA24DIT” built-in design for reducing the valve deposits that typically DIT engines. Time will tell until somebody with 40-50K mileage pops their tops and takes pics. I’m personally in the Ill believe it when I see it camp
 

·
Administrator
Joined
·
11,124 Posts
The reason carbon buildup on Direct Injection engines isn't mitigated by intake valve cleaners is because of how the systems are design. A direct injection system such as in our FA24DIT has high pressure injectors that spray directly into the combustion chamber. Because of that, the detergents in gasoline or the cleaners poured into the gas tank never hit the back of the valves or the valve stems.

See this image someone shared in an STI/WRX forum section.
3811


So, in the FA24DIT, Subaru has used a number of different methods to mitigate buildup. I am over the 50,000 mile mark, and may consider having mine checked, but, from what I've seen in groups discussing the WRX and FA20DIT, buildup is considerably less than one would expect.

Here's Subaru's response when I asked. the FA24DIT is supposed to be their pinnacle of this technology, and improved even over the FA20DIT, btw.

"Thank you for contacting Subaru. I appreciate the opportunity to be of assistance.

Older direct injection systems that experienced carbon build up were so called “lean burn” systems. Unfortunately these systems suffered many times from uneven combustion due to variations in the fuel and air mixture throughout the combustion chamber. This created a mix of lean and rich conditions resulting in variations in combustion temperature and uneven burning of the gasoline. This uneven burning lead to the condensing of unburned and partially burned hydrocarbons which over time resulted in carbon buildup.

Subaru engineers understood this when they created our current direct injection system. They developed innovative yet simple systems to manage and control the combustion variations inside the combustion chamber. These include features such as specially shaped piston crowns, multi-patterned injection spray, and tumble generator valves. All of which promote the precise swirling and intermix of fuel and air under the variable conditions required across the full range of power requirements. When combined with very high fuel pressures and extremely short injection duration of the Subaru direct injection system, stoichiometric combustion is maintained across the combustion chamber resulting in very even and complete burning. As a result abnormal residue and carbon deposits are not created and engine performance and fuel economy are maximized.

Please note that our research does show that routine maintenance, per the warranty & maintenance booklet, is another important factor when avoiding any potential carbon buildup concerns."
 

·
Registered
Joined
·
81 Posts
Fuel additives are not effective at intake valve cleaning with traditional direct-injected engines because fuel is injected directly into the combustion chamber. Some direct injection systems also have upstream fuel injectors that supplement the primary fuel injector, for the purposes of reducing deposits in the intake system. I don't think the FA24 engine has such a system. Meaning...any cleanser or detergent added to the fuel goes straight into the combustion chamber and does not help keep the intake tract and valve heads clean.

I don't know how much of an issue this is going to be in our engines in practice (intake system deposits), but the direct injection system design is why in-fuel detergents are not effective for this.
Combination port injection with direct, the main purpose isn't reducing deposits. It's just a side effect. It's mostly emissions.

Keeping the fuel injectors clean is also important in reducing depositions. Clean injectors still produce the optimized spray pattern for the atomization of the fuel, which means more optimized combustion with less carbon byproduct, that would ultimately build up on the back of the intake valves.

Some companies use fuel detergent (Polyether amine) part of the solvent mixture that is sprayed directly into the intake manifold, such as the CRC GDI IVD spray cleaner.


The BRZ doesn't have this issue because, it has Toyota's D4-S injection system
 

·
Administrator
Joined
·
11,124 Posts
The BRZ doesn't have this issue because, it has Toyota's D4-S injection system
Right, but the FA20F D4-S doesn't tune or boost as well. I am pretty sure Subaru couldn't get the desired power numbers out of the FA Series while using the D4-S injection system.

I guess it's also not unexpected thattl there are advantages and disadvantages of either route.
 
1 - 20 of 34 Posts
Top