Pros and cons of the boost return mod

[Alex]

I seem to have started a discussion on Facebook about removing the boost return on a G40, it's quite interesting. I'd be interested to hear your thoughts on it.

My understanding has always been that the boost return doesn't do much more than simply return oil vapours back to the charger for lubrication purposes, and that the benefits of a twin inlet are minimal. So don't bother, basically. I've never had the boost return pipework on my car - the crankcase breather is rotated around towards the passenger side and the inlet is blocked off. I've had it like this for eight and a half years, and I've never had any problems. I'm running a stock airbox, single inlet, with the crankcase breather routed to a catch tank.

The German G40 owners on Facebook reckon it's a bad idea, only suited to those who want to get the noise. I've talked them out of the need to have the vapours diverted back to the charger, but their version of things is that it's better to have the boost return because it's directing boost back into the charger so you get full beans more quickly than you would without it. Is this true?

I only ask because the discussion is timely. I found my boost return pipes in the garage the other week and I've been umming and ahhing about putting them back on, but still routing the breather to a catch can, to see what it's like not having the part-throttle hiss. But, as they've been in a dusty box for ages, I'll have to get all fussy about cleaning them (and the pipe through the rocker cover) before they go anywhere near the charger.

Interested to hear the arguments for and against...

[JoeH]

Do you spray that grease lube in, to compensate for loss of oil varpours?

Not sure about the full beans stuff, any thing after G-charger i.e. all pipe work to intercooler, and then to throttle body is boosted pressure, so that is the instant boost surely...and as long as the charger can suck enough new air in, I can't see any benefit the return pipe work brings...

Have heard return mod increases fuel economy (i.e. better) as always clean cold air coming in...especially on longer part throttle journeys, but I dunno...?

[Ben.lopo]

I get about 350 miles a tank ported charger r1 spec 65mm toothies and boost mod 13inc bbs wheels

[scully]

but their version of things is that it's better to have the boost return because it's directing boost back into the charger so you get full beans more quickly than you would without it. Is this true?

Seems to me, this isn't true, because most of the time you are not driving with pressure, and the moment you put your foot down, the return valve closes, directing all air towards the engine. Basically, a closed return valve is a necessity to build boost, otherwise you would just be circulating air around the engine from and to the supercharger.

[forbes-1234]

One of the cons and the thing that annoys me the most is the amount of oil vapour that gets blown into the engine bay.
Just took my G engine out and the bay is filthy with oil on drivers side bulkhead/turret!

[PeteG40]

One of the cons and the thing that annoys me the most is the amount of oil vapour that gets blown into the engine bay.
Just took my G engine out and the bay is filthy with oil on drivers side bulkhead/turret!

That shouldn't happen unless you have a worn or blown oil seal in your charger. Should be minimal

[forbes-1234]

Ok that must be the issue with mine then, boost pipes always had oil then them too.
It was rebuilt around 3000 miles ago though, previous owner said you did it for him haha (not that i'm questioning your work)

I thought the oil was getting pulled up through the pipe that attaches to the copot boost pipe and chucking it out the return valve, could be that the breather was blocked though.

[PeteG40]

Blocked breather can cause excess pressure and oil leaks.  Could also be residual oil/grease in the pipes

[OCDmatt]

Oil breather return isn't for lubrication really.

If the correct apex strips are used they contain enough PTFE to not require lubricating.

It's just the same as a breather going back into the engine on any other engine, it's to lower emissions, reduce noise and prevent any mess in the bay.

I ran my Golf with standard airbox and a blank, then went to twin intake airbox. Both with standard paper filter. The twin intake did make a noticable difference over a single intake.

But again MPG was pretty good and seemed a little better than standard G60's, not huge amounts that would make it worthwhile but every MPG counts I guess.

It is better for an engine to not have the breather going back through the system but in to a catch can so if you run boost return with a catch can or boost return blanked I think that's the best thing.

[PeteG40]

Some lube does help create a seal and increase boost. U can tell the difference with a charger with and without kluber grease.  It would seem Some lube can also reduce wear  on apex seals 

[scotsjohn]

In years gone by, I used to work with high vacuum pumps which had blades of solid PTFE. Even they required regular replacement due to wear. PTFE isn't some magic material with no wear properties and even if the apex seals contain it, they will wear with use. Additional lubricant is a definite requirement.

[OCDmatt]

Yeah, apex strips do need regular replacement.

The point is that the oil breather isn't there to solely lubricate them

[JoeH]

Yeah, apex strips do need regular replacement.

The point is that the oil breather isn't there to solely lubricate them

Hold on a sec, if oil breather isn't the sole lubricant, does that mean spraying in the ptfe stuff as an addition should be done to all G's whether boost return or not?

[kwijibo_coupe]

When I rebuilt my G40 engine I took out the boost return at first.
After doing about 500 miles like that I put the boost return piping back on. After doing so the engine didn't seem to pull as hard as it did before.
It may be just my imagination as you don't get as many noises.
Or maybe it's something to do with warmer air going through the charger, but surely my FMIC would take care of that?

Has no one tried doing back to back RR runs with and withough the boost return?