Q45 90mm Afm. Too Close To Turbo = Issues.

[Guilt-Toy]

Hey Guys

I got a top mounted GT3540 which has a 4" inlet with a 4" bend then a 4 to 3.5" silicon reducer plugged into the AFM then the filter so there is a short run to air filter.. Good setup ?? Well it looks good but it drives like SHIT.

When comming off boost to idle it will stall. The car would cough and backfire and jerk all the time and it HUNTS like crazy!! so I heard somewhere that the AFM shouldnt be close to the turbo so i tried a way to move it away.

So what i did was went to the hardware store and purchased some 3.5" PVC piping and a 90deg bend. We hooked it up and had the air flow meter sitting right in the gaurd where air flow runs through.

The results were suprising. it went totally awesome. The car sounded OFF ITS HEAD when comming onto boost and letting off the accelerator (air noise was just awesome) ALL the idle issues were resolved and all the popping and coughing and jerking just completly went away...

So i then decided that PCV plumbing pipe is dodgy and i really did not want my AFM to come off and run over it lol so I purchased some 4" flexible hose and put it on so its now 4" from the turbo straight to the AFM.

I found this setup to not work as well as the PVC 3.5" pipes. It does not sound no where near as good and it coughs a little and it nearly stalls when you come off boost. (still its MUCH better then the AFM close to the turbo but not as good as the PVC setup)

Wouldnt the 4" pipe be better ?? the AFM is 90MM and the pipe is 100mm so does anyone know why the bigger better pipe does not work as well as the $20 PVC plumbing job we did. Normally dodgy is never better but in this case... I am confused.

Is it because the PVC is the same size as the AFM and it runs more stable that way ? if thats the case should you use pipe the same size as the AFM all the way through for best driveablilty.

So yeah anyone know whats the best way to sort this one out. I am thinking of getting a 3.5" pipe made up from the 4" bend to see how it goes but that will cost around $150 so anyone been through this before ?

Edited April 5, 2006 by Guilt-Toy

[RB power]

do u have any pics of ur old and new setup?

[Bl4cK32]

well ive got a shitty pod adaptor on that is for a 80mm r32 afm to a 80mm pod.

Atm its running a 80mm pod to the 90mm q45 afm, then the std r32 rubber inlet hosing to the turbo. I havent had any idle issues with this setup, but it does play with the voltages a little when tuning.

Im going to *insert lazy comment by Cubes here* fit a 5" inlet pod to the 90mm q45 afm when i can be arsed making the adaptor to take out my restriction. When i replace the highflow im running now (on the 3lt) to a gt30/35r? ( havent decided) i'll change the piping to suit.

Always ideal having good flow infront of the turbo i think.

[Craved]

i have similar sort of issues when backing off, but i just think its the non recirc BOV thats causing it.

i have 100mm inlet .. then a 45 bend in 100mm stainles, then to a 80mm reducer to the Z32 afm ..

no room for the recric to really go, i'll try to post some pics, but i dont know how the length of the pipe would affect the idle.

[RB power]

i have similar sort of issues when backing off, but i just think its the non recirc BOV thats causing it.

i have 100mm inlet .. then a 45 bend in 100mm stainles, then to a 80mm reducer to the Z32 afm ..

no room for the recric to really go, i'll try to post some pics, but i dont know how the length of the pipe would affect the idle.

I have the same setup but mine goes to a Q45 afm

Edited April 5, 2006 by RB power

[R31Nismoid]

i have similar sort of issues when backing off, but i just think its the non recirc BOV thats causing it.

i have 100mm inlet .. then a 45 bend in 100mm stainles, then to a 80mm reducer to the Z32 afm ..

no room for the recric to really go, i'll try to post some pics, but i dont know how the length of the pipe would affect the idle.

i dont think it should make a difference as you say.

Mine was pretty close to my GT30 and i never had a problem with anything.

But then, i had a re-circ BOV

You have room im sure

[paulr33]

is it the compressor chuffing problem you think ?

[discopotato03]

I would have thought plumbing stepping up between the 90mm Q45AFM and the turbo inlet would offer no advantage . Since the comp covers are aluminium it would be very easy to have the inlet boss turned down to 90mm , its only 5mm off the radius of the boss and the plumbing can be one size - no expensive silicon reducers required .

Cheers A .

[Guilt-Toy]

is it the compressor chuffing problem you think ?

YES. I think

[Craved]

i dont think it should make a difference as you say.

Mine was pretty close to my GT30 and i never had a problem with anything.

But then, i had a re-circ BOV

You have room im sure

BOV is where the washer bottle used to be with the plazmaman plenum ..

more of a "i cant be arsed making a pipe from one side of the engine bay to the other for the BOV" lol

stop pointing out my lazyness lol

[Craved]

I have the same setup but mine goes to a Q45 afm

yes mines like that picture, only with a reducer for the z32..

[paulr33]

what do we know about the chuffing/shuffling problem on the compressor side so far? what causes it? i think a workaround is to move the airflow meter after the compressor outlet, pre TB.

[paulr33]

does it only occur after u come off boost?

does it happen at idle by itself or in low rpm range?

[Guilt-Toy]

does it only occur after u come off boost?

does it happen at idle by itself or in low rpm range?

No it can even occur after driving in vacume and you slow down to a set of lights.. when you stop the engine will hunt and dump in heaps of fuel (lots of black smoke) and run rich as. With the AFM moved away from the turbo (under the front gaurd) it works perfect with the dodgy pvc setup and works acceptable with the 4" flex hose.

What would be the benifits of moving the AFM onto the boost pipe. would the AFM handle it ??? I am starting to think i should replace the flex hose with a 3.5" mandrell bend + pipe and see how it goes.

[paulr33]

i dont think theres any issues relocating the airflow meter

i wonder if it could be tuned out. any chance you see what map tracer shows?

[Guilt-Toy]

i dont think theres any issues relocating the airflow meter

i wonder if it could be tuned out. any chance you see what map tracer shows?

Yeah map tracer goes off its head... it does a nice circle.. in around the first 5 x 5 box's etc....

It hunts and runs like crap. Move the AFM away from the turbo and its great.

apparently HKS make a little unit called IDS or something that catches the idle and stops this issue but they are worth about $400.

Moving the AFM away from the turbo works great. Just cant work out why the 3.5" pvc pipe works better then the 4" 100mm flex hose!!!

[Sydneykid]

No it can even occur after driving in vacume and you slow down to a set of lights.. when you stop the engine will hunt and dump in heaps of fuel (lots of black smoke) and run rich as. With the AFM moved away from the turbo (under the front gaurd) it works perfect with the dodgy pvc setup and works acceptable with the 4" flex hose.

What would be the benifits of moving the AFM onto the boost pipe. would the AFM handle it ??? I am starting to think i should replace the flex hose with a 3.5" mandrell bend + pipe and see how it goes.

Definitely sounds like air reversion through the AFM. If it is you can see it on the AFM voltage trace you get spikes and troughs as the air bounces between the compressor and the AFM. I found a couple of things help;

1. Run as large a diameter pipework as you can. I use 100 mm alloy, mandrel bent pipe with a 100/90 silicone reducer to fit the Q45 AFM

2. Make the distance between the AFM and the compressor as long as you can.

3. Make the bend angle as large as you can. I noticed in the pictures some of the bend angles in the inlet pipework are around 30 degrees and they start almost straight off the compressor. Mine has a straight length off the compressor, about 300-400 mm long. Then a larger angle bend, maybe 60-70 degrees. A very short, straight length into the 100/90 silicom reducer.

4. Running a heat shield, I found the hot air coming in from the rear of the radiator made the rough idle worse. Particularly when the fan was running. The heat shield on its own made a difference.

Some logic.........the longer/larger diameter is obvious, it simply gives more air buffering space between the compressor and the AFM. The larger angle bend is to stop the air off the compressor hitting the AFM directly, it has to bounce off the walls of the pipework.

That worked OK at around 600 bhp using the T66, I wonder how it is going to go with another 200 bhp and a bigger turbo.

cheers

[paulr33]

without knowing any more about the eids i suspect it just watches for a big drop in AFM voltage and when it see's that clamps it for about 5-6 seconds to try and stabalise it. it could also be done on the AFM voltage ramp in the FC with a fair bit of screwing around

im sure cubes could fix it

[Guilt-Toy]

Definitely sounds like air reversion through the AFM. If it is you can see it on the AFM voltage trace you get spikes and troughs as the air bounces between the compressor and the AFM. I found a couple of things help;

1. Run as large a diameter pipework as you can. I use 100 mm alloy, mandrel bent pipe with a 100/90 silicone reducer to fit the Q45 AFM

2. Make the distance between the AFM and the compressor as long as you can.

3. Make the bend angle as large as you can. I noticed in the pictures some of the bend angles in the inlet pipework are around 30 degrees and they start almost straight off the compressor. Mine has a straight length off the compressor, about 300-400 mm long. Then a larger angle bend, maybe 60-70 degrees. A very short, straight length into the 100/90 silicom reducer.

4. Running a heat shield, I found the hot air coming in from the rear of the radiator made the rough idle worse. Particularly when the fan was running. The heat shield on its own made a difference.

Some logic.........the longer/larger diameter is obvious, it simply gives more air buffering space between the compressor and the AFM. The larger angle bend is to stop the air off the compressor hitting the AFM directly, it has to bounce off the walls of the pipework.

That worked OK at around 600 bhp using the T66, I wonder how it is going to go with another 200 bhp and a bigger turbo.

cheers

Thanks Mr I work in my own workshop and I know everthing LOL

I knew i was on the right track there.. But can you shed some light on why the 3.5" plastic PVC piping works 100 times better then the bigger 4" flex hose the same length oh and the PVC piping sounds heaps better too...

WHY!! *scratches head confused as hell*

[Cubes]

Im going to *insert lazy comment by Cubes here* fit a 5" inlet pod to the 90mm q45 afm when i can be arsed making the adaptor to take out my restriction. When i replace the highflow im running now (on the 3lt) to a gt30/35r? ( havent decided) i'll change the piping to suit.

LMAO....