Air filters

johnny gtir

johnny gtir

Well-Known Member
PobodY said:
Why would you have back pressure from the turbo; that's the low pressure side? - Is this if you're running without a BOV?
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just what i seen posted somewhere and owen developments mentioned it when i bought my turbo.i will have a look and get back to you (you know the little holes on the inlet side of some turbo's what are they for ? 99% its anti surge i remember something along the lines of them been mentioned in the same phone conversation) i am just putting it up for people to add there thoughts not saying i am right
 
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PobodY

PobodY

Moderators
Staff member
It's an honest question. There are a few things like this that people (not just on this forum) believe that don't really stand-up to scrutiny. - As I'm a scientist, I'm always asking "why" and "how"; if they can show me the evidence and I'll be satisfied. If they can't I'll keep annoying people with questions.

Often it turns-out that there is some truth in it, but not necessarily for this car/engine/set-up.

I always thought that popping MAFs was a problem with people running them (like Spikey) as blow-by because they're not designed to take the extra pressure; on the end of the inlet pipework they're at atmospheric pressure.
 
PobodY

PobodY

Moderators
Staff member
Spikey said:
But a maf reads volume (flow) not pressure so its not really affected.
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True, but it was designed to work with atmospheric pressure (i.e 1 atmosphere); if it's now on the pressured side of the turbo it's in an environment it wasn't designed for (for example +2 bar ~ 3 atmospheres). It's no different to taking something that's supposed to carry 10Kg and putting 30Kg in it; you shouldn't be surprised when it breaks.

That's why there are all those reinforcement mods and steel housings for it if you want to use it that way.
 
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skiddusmarkus

Active Member
I've always been told what Po is saying, but not sure if its mainly to protect the hotwire from oil contamination its subject to coming from the turbo seals.
If you think about it, say you ran 2 bar with the MAF after the turbo pushing the MAF housing out, its still got 1 bar of atmospheric pressure(more or less) of air pressure pushing it in so only really 1 bar acting on the walls, which ain't that much in the scheme of things.Plus its circular which is naturally a very strong shape as it spreads the load around evenly.
 
williams

williams

New Member
The 2 bar turbo pressure is 2 bar above atmo, so its 3 x atmo pressure. So you still have the 2 bar pushing out. Its not just the plastic casing though, there's the seal inside aswell where the wire/sensor comes thriugh.
 
johnny gtir

johnny gtir

Well-Known Member
PobodY said:
It's an honest question. There are a few things like this that people (not just on this forum) believe that don't really stand-up to scrutiny. - As I'm a scientist, I'm always asking "why" and "how"; if they can show me the evidence and I'll be satisfied. If they can't I'll keep annoying people with questions.

Often it turns-out that there is some truth in it, but not necessarily for this car/engine/set-up.

I always thought that popping MAFs was a problem with people running them (like Spikey) as blow-by because they're not designed to take the extra pressure; on the end of the inlet pipework they're at atmospheric pressure.
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po it is beyond me. No mention of running without a bov but all i can find on inlet surge is more than the turbo can flow so it backs up to the easyest way possible ie the inlet side caused mainly by powering on hard then sudden backing off .A bov sorts this issue on the exhaust side but nothing on the inlet side so two 90 degree bends or a anti surge inlet turbo helps stop back pressure which could inturn damage the maf ?
 
red reading

red reading

Active Member
The 2 45 degree bends on the inlet are to stop turbulence from the turbo screwing with the maf readings, they cause the car to run rich at low rpm and the car to stall.... i.e when you rev the car at standstill, anti surge is just that if you try to force to much charge in the engine and it can't flow it it surges back thru the turbo and stall's the turbo leading to turbo failure (if you ever see it or feel it,you are in deep poo poo), BOV just release excess pressure when you lift off the throttle for a split second (inlet side) and wastegates control the flow thru the turbine and set your boost pressure.

If you build a blow thru z32 out of steel it works fine under pressure from the turbo and is better for throttle response.
 
johnny gtir

johnny gtir

Well-Known Member
red reading said:
The 2 45 degree bends on the inlet are to stop turbulence from the turbo screwing with the maf readings, they cause the car to run rich at low rpm and the car to stall.... i.e when you rev the car at standstill, anti surge is just that if you try to force to much charge in the engine and it can't flow it it surges back thru the turbo and stall's the turbo leading to turbo failure (if you ever see it or feel it,you are in deep poo poo), BOV just release excess pressure when you lift off the throttle for a split second (inlet side) and wastegates control the flow thru the turbine and set your boost pressure.

As the man say's :thumbsup:this is what i mean i spend few hours gooling trying to make sense of it all and put it into simple form.Along comes danny puts it into a few simple words and already knew the answer
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johnsy

johnsy

Active Member
so should i change the 45deg pipe to 2x90deg pipe's or is what your all talking about only apply to the standard maf?

Danny i thought that inlet pipe you had was a 45deg with the filter on the end
 
red reading

red reading

Active Member
Its 2 x45degree swan neck on my old set up (new is blow thru maf and 800rpm idle) and i had to have 950rpm idle with that, it was the best compromise for power (less restriction and shortest lenth for flow) and drivability whilst keeping the maf as close as possible to the turbo
 
red reading

red reading

Active Member
on the picture above there is no z32 fitted, sascha uses a blow thru mounted buy his intercooler (which is'nt a z32 either),

if you use a z32 on a single 45 degree bend you will get turbulent airflow and it gets worse the bigger the compressor is on your turbo, as you will find out on the md196. 71mm compressors are bad enough (2871/3071), you can fudge it when mapping but it is'n clever (if done to a power f/c the car will start to hunt at idle)

You need a minimum of 2 x 45degree bends on the compressor inlet to the maf on a draw thru set up (made of alloy or steel as silicon collapses under vacuem and robs you of power)
 
johnsy

johnsy

Active Member
so it'll be fine with 2x 90's then in stainless steel, or does it have to be 45deg bends?

i was about to send the 90's back

if i remember rightly my old silicone setup was 2 x90 and it avoided the bottom rad hose unlike the 45
 
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skiddusmarkus

Active Member
Mine uses 2x76mm 90 degree bends, no problems with the Z32 and also gives you more flexibility with positioning the filter than 45's would.Using 2 45's will mean the piperun will have to be longer and you might run out of space up against the n/s wing with a big filter.
 
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