Blow through setups

campbellju

campbellju

Moderators
Staff member
From my experience, physically the difference is marginal. By logging, the improvement in response is a few ms. It does make the issue of mapping around the BOV issues a lot easier so mine stayed off. Never had a problem with turbo wear from lack of BOV even running 1.9Bar. Running 1.9Bar and turbo wear might be a different issue ;-)
 
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J

Jon Olds

Well-Known Member
Have thought about taking the bov off. Even thought about putting a reducer in series with it (orifice) to lessen its effect. Have watched some vids of the rally car in action and there is a telltale puff of 'too rich' visible at most gearchanges. This must hurt the engines ability to pull cleanly. Tarmac rallying is basically flat out up thro the gears, full brakes down the gears, and repeat...there is not many times you are on steady throttle, couple of secs only on a longer corner only. More opinions on blow thru and bovs please
 
red reading

red reading

Active Member
have tried all setup combinations and found that my preferance was a blowthru maf fitted in a 18" straight stainless pipe before the plenum with the dump valve venting(alot of preload on the dv spring so only dumped at over a bar) to atmo in the standard place on the plenum, it had very good throttle responce and idle and was miles better than a draw thru maf on a nistune ecu.............have since gone map and iat on a syvecs and that is miles better again for drivability.
 
J

Jon Olds

Well-Known Member
BOV in std position , rather than the 'other' side of the AFM. What is your reasoning for leaving it there? (The only benefit I can see if the BOV is venting as close as poss to the biggest air volume :plenum)

Would still like to get rid of the transient richness I think I have at every gearchange.
 
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skiddusmarkus

Active Member
I switched to blow through a couple of days ago and changed the inlet at the same time.It now has 2x 3" 45 degree bends onto a huge k&n.On the intercooler piping I had to replace one of the Froge supplied 45 degree samcos for a hard pipe and used 2x 76mm>63mm silicone reducers to slot the MAF in.I also had to chop the bit of pipe that houses the water injection nozzle down to fit.
The air intake no longer incorporates a recirc adapter for the bov and I might be selling my old 3" inlet once this setup has been mapped.I can't give any opinion in how it drives as as soon as I finished it I went away for the weekend.Plus its not mapped for a blow through and was running lean on tickover.



 
red reading

red reading

Active Member
your maf will fall apart and you will get funny readings from having the reducers so close to each end of the maf, there was a reason why i built a 3" steel one that was 18" long too
 
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skiddusmarkus

Active Member
I don't have the room to make a longer straight run without totally redoing all the pipework post intercooler Danny.I read you need to have 8" of straight pipe before the MAF and it has this, just after a nice smooth 45 degree mandrel bent pipe.I can eek out maybe an extra inch(fnar fnar) but had to stop as ran out of time to adjust any more on the day.
I can probably swap the large 2.5" 45 degree silicone bend at the bottom of the picture for a 3" one and then no need for a reducer into the MAF, that would mean around 18" of 3" pipe including the MAF.

I will be taking the cover off the MAF and filling it with some sealant and maybe a couple of large jubilee clips going around the cover/maf housing with a silicone/rubber sleeve to held hold it in place.
 
red reading

red reading

Active Member
skiddusmarkus said:
I don't have the room to make a longer straight run without totally redoing all the pipework post intercooler Danny.I read you need to have 8" of straight pipe before the MAF and it has this, just after a nice smooth 45 degree mandrel bent pipe.I can eek out maybe an extra inch(fnar fnar) but had to stop as ran out of time to adjust any more on the day.
I can probably swap the large 2.5" 45 degree silicone bend at the bottom of the picture for a 3" one and then no need for a reducer into the MAF, that would mean around 18" of 3" pipe including the MAF.

I will be taking the cover off the MAF and filling it with some sealant and maybe a couple of large jubilee clips going around the cover/maf housing with a silicone/rubber sleeve to held hold it in place.
Click to expand...

simon ,change the reducer before the maf , also its the plastic adapter end of the maf that fails not just the sensor being blowen out and the lid coming off.
 
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skiddusmarkus

Active Member
Yeah , think I will order a 3" 45 stainess 45 degree to replace the stailess 2.5" one I just fitted(can always use that to replace another part on the hot side of intercooler)that will move the reducer nearly a foot down from where it is now.The plastic maf adapter is going too for a metal one.

What about the reducer after the MAF?No tmuch I can do about that one without welding a new flange onto the plenum.
 
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skiddusmarkus

Active Member
Had another mess about today and decided to try and straighten out the pipework into the mAF as much as possible.I had bought a few stainless bends and I had some kicking about in the garage along with some silicone joiners/reducers and came up with this:





I brought it up from the below the radiator with a 3">2.5" reducer then a 3" 90 degree bend into 3" length to the z32 maf so should be much smoother airflow into it.I will sort out sealing the MAF at a later date.

I also bought a new bend to come off the turbo as i wasn't happy with the butchered Forge item and I swapped a silicone 45 degree bend for a stainless one.Most of the Silicone pipes have been swapped for metal ones now.

 
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skiddusmarkus

Active Member
This is where I am up to now.I just had a new z32 maf delivered to swap over the one I cut the mesh off and upon starting up the car was very hesitant to rev at tickover with any throttle.I switched the MAF for a none OE z32 i have and it ran better on that for some reason.Anyway, switched back the genuine z32 in and took it for a gentle test drive.The car wanted to stall once at a junction but didn't as i blipped throttle.It doesn't pull anything like it should and the power comes in what I can only describe as pulses with it pulling better at higher revs than lower.
I didn't give it any stick as the car is obviously in need of a remap to suit the new configuration.When I got back home though and the egine was warmed up, the tickover was sitting nicely at 950rpm whereas in the past its always been 1.1k+.It also reved more freely at tickover once warmed up.
 
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danr

Member
turbulence is causing hesitation (pulses) imho
also im sure i remember reading the elements preferably need to be vertical, ie. the flat cap needs to be level horizontal (try google)
 
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skiddusmarkus

Active Member
It was horizontal before in draw through and no issues.Edit: reread what you put and you meant the element inside not the maf itself.I turned it that way as it close to the side vent in the bonnet and wanted the plug to be as far away from any water getting in as possible.I'll try it with the element vertical as suggested.I might also make a small shield to attach to the underside of the vent which will angle any water away from the maf without blockign the vent.

Could the reducer after the maf also cause turbulance?Its also quite close to the 90 degree bend into the plenum, so should I try and space it further from that at the expense of less straight pipe before the maf?

The BOV is running vta atm and after the maf.I know some say you should put it before the maf in this setup, but I have never had any issues with the hks sqv causinf stalling etc before.Also, I know people say to move it pre-maf as then its venting non metered air, but imo the air post maf is also going to vent through it just as much as pre maf
, so the same amount of metered air would still be released, albeit a lot less than when the maf is in the OE position.
 
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williams

williams

New Member
the mesh is on the front of the maf for a reason, thats probably the cause of your running problems. its something to do with teh way the air flows through it.
 
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