Jump to content
SAU Community

Recommended Posts

On 07/06/2020 at 9:17 AM, Dose Pipe Sutututu said:

Run a R35 AFM post cooler if you're intending to sick with Nistune. Not to mention, running post cooler gives you the added benefit of actually capturing true mass air flow once it has been chilled. 

pffft.  Bit of faux science there!  There is no change in air mass pre or post cooler unless you have a hose leak.  Post cooler you have lower volume, but higher pressure....same mass.  What you need for a MAF-AFM to work is

- laminar flow (i.e. not in a post-turbo vortex or after a big cooler pipe bend).

- uncontaminated by oil vapour (i.e. not downstream of a PCV pipe or leaky turbo)

if you can meet those criteria, post cooler will be fine, but why mess with the original design?  The most likely place for uncontaminated laminar flow in the intact tract is straight after the factory airbox.

YMMV if you have a pod filter that creates a vortex flow, or an oiled pod filer.

@ob1 you might be entirely correct, however how would you accurately compensate for different charge temps? Those running MAFs on PowerFCs or Nistunes have no ability to compensate anything for different charge temps.

Having it post cooler at least would provide an accurate reading of the air entering the motor once it has been chilled. 

I'm keen to hear @GTSBoy's opinion, he's like Yoda.

1 hour ago, ob1 said:

laminar flow (i.e. not in a post-turbo vortex or after a big cooler pipe bend).

I hate to shoot down your own faux science there, but let me assure you that there is no "laminar flow" in any such environment (automotive intake tract flow).

The definition of laminar flow is the regime where the Reynolds Number is below 2000. With very low density and low viscosity fluids (ie, air) this is almost impossible to have unless the diameter is absolutely tiny, or the velocity is very very low. The Re will be many tens of thousands in any typical automotive intake tract, which is very very far into the turbulent flow regime (which starts at around Re=4000). It is turbulent. It is fully turbulent. There is no way to argue that it is not turbulent.

What you are actually trying to describe is called "well developed flow". The Re is still way too high for the flow to be laminar, it is indeed fully turbulent. But, as you allude to, immediately after a bend or other flow disturbance you have flow which is disturbed in some way. Biased to the outside of a bend, full of swirl or tumble from some flow disturbance like a side port. But after some distance of totally straight pipe, these disturbances will settle out as the energy in the flow is redistributed through internal friction and inertial effects, the flow will resume a nice "fully developed" velocity profile. Which, in turbulent flow is a velocity profile that is fairly flat across most of the duct tapering off to zero only close to the walls. The velocity profile looks more like a cut off bullet, rather than the actual 22 bullet shaped velocity profile you see in true laminar flow.

But here's the stinger. It takes at least 10 diameters of straight pipe for flow to start looking well developed. It really takes at least 20 diameters for it to be getting close to well developed. And aerodynamicists and other engineers working in this area would not consider anything less than about 40 diameters of straight pipe if they wanted an undisturbed flow profile to do work with. (There are ways to cheat this with flow straighteners of various sorts, but we will ignore these as they are not really that practical for automotive applications).

The upshot? There's really not any length of straight pipe in the inlet tract of almost any car's engine that would get you anywhere near close to well developed. You'd be lucky to get 5 straight diameters. (You should place any typical flow meter at least 10D downstream from a disturbance and ideally at least 5D upstream from the next disturbance. If you can't get that many Ds either side, you're best bet is to divide the space in the same ratio, sorta 67/33 %ish, unless you are really short of diameters, then you lean towards biasing the available length to the upstream side, and be aware that your meter's accuracy will have compromises).

Ultimately though, it does not matter a shit. Because we are not using the flow meter in a car to provide us with an actual total mass flow with output in kg/s. All we are using it for is an input signal to the ECU to measure load, and we tune against that load in an essentially dimensionless way. All we care about is the AFR reported in the exhaust. So it almost doesn't matter where the AFM is (unless it is outside its physical limits, like too hot, too much pressure, etc) - so long as the flow "shape" remains the same as it was tuned against, then it is good.

I would still put the AFM in front of the turbo as first preference, because it is cold and clean, which is a big thing for hot wire anemometers. Next preference would be after the cooler, because at least it is "cold". May or may not be clean, as you say about oil sources. But at least it's cooler. And it is absolutely true that automotive AFMs are not intended to operate with really hot air like you will get straight out of a turbo. Neither the temperature sensors in them, the control algorithm of the heated wire, nor the electronics attached are intended to be exposed to ~100°C temps, let alone the >>100°C temps you will see at 20+ psi of boost.

Edited by GTSBoy
  • Like 4
26 minutes ago, Dose Pipe Sutututu said:

Having it post cooler at least would provide an accurate reading of the air entering the motor once it has been chilled.

Sadly, while these AFMs might (they do) measure the air temp of the air going through them (they have to in order to even work), but they do not report it anywhere. It's only used internally to work out what the current used to heat the wire to target temperature actually means in terms of mass flow.

So long as the air temperature does not exceed the capabilities of the temp sensor, etc, as I said in the above post, it will still work post turbo in hot air. But I'd be willing to bet that many such installations are far exceeding what the AFM should be exposed to and are probably actually quite dangerous in terms of tuning, because if things like air temp are being clipped at the max value, the AFM is not measuring properly. That's just like running an AFM up off the top of the 0-5V scale and "tuning" be simply adding more fuel at the top of the table. There's no actual flow measurement. That voltage could be any flow out of a range of possible flows once you go off the top. Same with clipping the max temperature, etc.

I must stress though that I don't know what the max temp these things are able to work in is. A normal RTD is good for ~450°C, but if you don't need to go that high you would not ever calibrate its electronics to read that high. You'd use your available resolution more wisely. I'd expect the automotive guys to do that too, but it's a question of what max they'd choose. For their intended application, you'd not need any more than ~100°C, because you'd never expect the ambient air or even engine bay air to be that hot. They might use that, or they might use 150°C. I dunno. But in the absence of knowledge, a little more caution is better than just blindly charging ahead. So I'd be cautious.

Carrying on from the discussion of where to put the AFM, as I said above, the best place would be before the turbo, but once things start becoming a little more extreme (like big 4" diameter turbo inlets, lack of room for a nice pipe to place the AFM in, etc) people get cornered into having to consider moving it post turbo. In that case, as I said in previous post and for the reasons of caution I said here, post cooler is the smart place.

Edited by GTSBoy
  • Like 3

@GTSBoy very good explanation, always can count on you.

Generally I just leave them where they are however with card style aka R35 MAFs I fine they are horrible when they're installed into intake pipes greater than 3". It's like their ability to meter accurately goes out the window on idle where air velocity is low, and when a car has cams it makes it even worse.

I've added all sorts of idle stabilisations, afm voltage smoothing but they always idle like shit once you've got brappy cams and big intake pipes.

I find they're so much easier to tune post IC, as you're not greatly affected by low velocity air.

Then again, speed density is my pick.

18 minutes ago, Dose Pipe Sutututu said:

It's like their ability to meter accurately goes out the window on idle where air velocity is low,

It's not "like" it at all. It is exactly it. There is a minimum velocity** below which the sensor's accuracy goes to shit. That's the catch 22 in these things. A 500HP engine (that makes 500 HP because of boost) only uses almost exactly the same amount of air at idle as its 200HP unboosted original version does. But you need the AFM to be big enough to measure the 500HP worth of air.

It sucks really, because these AFMs are really only measuring velocity**. The "flow" simply comes from multiplying the measured velocity by the cross-sectional area of the tube that it is in. Bigger tube means the same velocity = more flow.

**Have to be real careful here. They kind of actually measure the "mass velocity" of the air going past the sensing element. The mass of air flowing past steals heat from the wire and the current used to keep the wire at the right temperature is the indicator of that mass flow rate. The mass flow rate is not really at a single point, it is actually obviously in the very small cross-sectional area around the sensing element. But that little cross sectional area is always the same, regardless of how big the rest of the tube the AFM is installed into is. So you can sort of allow the "mass velocity" to condense to "velocity" in your mind when thinking about it. But....that's also only really true when the air is at a reasonably constant density, like it is out the front of the turbo. If you put it after the turbo (cooler), then the density of the air can be way more than double (because of boost), so for the same "mass velocity" you can actually have a much much lower real velocity. Still stealing the same amount of heat from the sensing element.

You could go crazy trying to juggle these parameters in your head when working out whether a given sensor will work better in one spot or another. Superficially, at least, I think we really need turbo inlets to be too large for the AFMs to work so that the pressure losses are absolutely minimised. That's because vacuum in front of a turbo is totally parasitic to turbo capacity. Need them to be big for the turbo, but that's too big for the AFM. Post turbo, we only need the pipes to be large enough to minimise pressure drop from friction, which is a whole different relationship and you're willing to give away a tiny bot more there than you are pre-turbo. So it ends up doing exactly what Dose said - you can get both good full scale capacity and good resolution when you put the AFM car post cooler. Less compromise in one or the other than pre-turbo.

Edited by GTSBoy
  • Like 1
2 hours ago, Gts-t said:

Got anything good for rb20det? Not interested in high flows. Preferably internal gate and 300kw max on 98. Cheers Tao

I can get it to make around 240rwkws reasonably responsive, but 300rwkws internally gated will be a big call for Rb20det. I guess you can run an ATR45SAT in it and see how that would respond, but its won't be anything nice to drive in a Rb20det. 

  • Like 1

This is the final tune with stock cams unless something new come up. Car made a nice and responsive 537rwkws @ 36psi on E85 fuel, making 225rwkws @ 4000RPM, I will be moving into internally gated turbos for the coming weeks and hopefully some of the latest externally gated models can be made into high flows and RB bolt on turbos.  

R34 GTT

Rb25det NEO Stock Cams
Nitto Pistons and Rods. 9:1 CPR
HyperGear ATR45SS-2 Turbocharger
ID 1500cc injectors
Twin Walbro 525L fuel pump
Adaptronic Plugin ECU
Greedy Profect B EBC
600x300x81mm PWR Cooler kit
3inches turbo back exhaust
4inches intake pipe with Pod
Split fire coil packs
Twin pulse manifold and twin 40mm gate. 
Car made 537rwkws @ 36psi, E85 fuel. With 225rwkws @ 4000RPM. Cams are maxed

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/power.jpg

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/boost.jpg

 

  • Like 3
1 hour ago, hypergear said:

This is the final tune with stock cams unless something new come up. Car made a nice and responsive 537rwkws @ 36psi on E85 fuel, making 225rwkws @ 4000RPM, I will be moving into internally gated turbos for the coming weeks and hopefully some of the latest externally gated models can be made into high flows and RB bolt on turbos.  

R34 GTT

Rb25det NEO Stock Cams
Nitto Pistons and Rods. 9:1 CPR
HyperGear ATR45SS-2 Turbocharger
ID 1500cc injectors
Twin Walbro 525L fuel pump
Adaptronic Plugin ECU
Greedy Profect B EBC
600x300x81mm PWR Cooler kit
3inches turbo back exhaust
4inches intake pipe with Pod
Split fire coil packs
Twin pulse manifold and twin 40mm gate. 
Car made 537rwkws @ 36psi, E85 fuel. With 225rwkws @ 4000RPM. Cams are maxed

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/power.jpg

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/boost.jpg

 

Must be one of the most cost effective 500KW+ builds ever!

4 hours ago, tridentt150v said:

What about the drive train?  Still very impressive though.

4th gear is fine, if he tried that stunt in 3rd the car would be going home on a tow truck haha

  • Haha 1
On 24/06/2020 at 8:26 PM, hypergear said:

This is the final tune with stock cams unless something new come up. Car made a nice and responsive 537rwkws @ 36psi on E85 fuel, making 225rwkws @ 4000RPM, I will be moving into internally gated turbos for the coming weeks and hopefully some of the latest externally gated models can be made into high flows and RB bolt on turbos.  

R34 GTT

Rb25det NEO Stock Cams
Nitto Pistons and Rods. 9:1 CPR
HyperGear ATR45SS-2 Turbocharger
ID 1500cc injectors
Twin Walbro 525L fuel pump
Adaptronic Plugin ECU
Greedy Profect B EBC
600x300x81mm PWR Cooler kit
3inches turbo back exhaust
4inches intake pipe with Pod
Split fire coil packs
Twin pulse manifold and twin 40mm gate. 
Car made 537rwkws @ 36psi, E85 fuel. With 225rwkws @ 4000RPM. Cams are maxed

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/power.jpg

https://hypergearturbos.com/images/dynosheets/atr45/atr45ss2537rwkw/boost.jpg

 

Is this turbo comparable to the new GTX3584? Im looking to replace the GT4202R in my compound setup and some of these new 67mm compressors seem to flow just as well or even better than the old 74mm 42R unit.

 

A very good video and result to share from a none VCT (Cams with cam gears) SR20det making 368rwkws powered by a ATR43SS2 BB turbocharger. externally gated on E85 fuel. car makes 200rwkws @ 4000RPM.

enginebay.jpg

power.jpg 

 

  • 2 weeks later...

Hi, Would someone be able to tell me what is the correct size hose and speedflow fittings i would need to make braided water lines to install atr45sat, 

water feed line (block to turbo)

And

water return line (turbo to push fitting on back of block)

Thanks.

For current models

Bush bearing:  

Oil: M10.1.25  Water: M18x1.5, Oil drain pattern: 2 inches.

Ball bearing:

Oil: 7/16 - 24 Water: M14x1.5, Oil drain pattern: 1.5 inches. 

  • 2 weeks later...

Latest result to share testing an Internally gated ATR43SS-2 with Rb25det Bolton assembly. On E85 fuel, car made 360rwkws @ 20psi. I've made an adapter so it fitted to my high mount exhaust manifold.

Rb25det NEO Stock Cams
Nitto Pistons and Rods. 9:1 CPR
HyperGear ATR43SS-2 internally gated Turbocharger
ID 1500cc injectors
Twin Walbro 525L fuel pump
Adaptronic Plugin ECU
Greedy Profect B EBC
600x300x81mm PWR Cooler kit
3inches turbo back exhaust
4inches intake pipe with Pod
Split fire coil packs

 

power.jpg

 

boost.jpg

 

Thanks all for all the help, I have most of the main pieces of the puzzle ready to go now. :D

ATR45SAT-BB (thanks Tao, she's a little cutie), 1000cc injectors, 460l pump, HPX-N1 maf, Nistunes off getting updated to feature pack 2.1 + having the flex fuel gear installed.

Only hard bit now is the intake piping, which I'm hoping I can just get fabricated by whoever installs it to make life nice and easy. Save me doing bits, towing it to a fabricator, then towing it to a tuner etc. if possible.

On that note, Any recommendations for an installer/tuner in QLD?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • This. As for your options - I suggest remote mounting the Nissan sensor further away on a length of steel tube. That tube to have a loop in it to handle vibration, etc etc. You will need to either put a tee and a bleed fitting near the sensor, or crack the fitting at the sensor to bleed it full of oil when you first set it up, otherwise you won't get the line filled. But this is a small problem. Just needs enough access to get it done.
    • The time is always correct. Only the date is wrong. It currently thinks it is January 19. Tomorrow it will say it is January 20. The date and time are ( should be ! ) retrieved from the GPS navigation system.
    • Buy yourself a set of easy outs. See if they will get a good bite in and unthread it.   Very very lucky the whole sender didn't let go while on the track and cost you a motor!
    • Well GTSBoy, prepare yourself further. I did a track day with 1/2 a day prep on Friday, inpromptu. The good news is that I got home, and didn't drive the car into a wall. Everything seemed mostly okay. The car was even a little faster than it was last time. I also got to get some good datalog data too. I also noticed a tiny bit of knock which was (luckily?) recorded. All I know is the knock sensors got recalibrated.... and are notorious for false knock. So I don't know if they are too sensitive, not sensitive enough... or some other third option. But I reduced timing anyway. It wasn't every pull through the session either. Think along the lines of -1 degree of timing for say, three instances while at the top of 4th in a 20 minute all-hot-lap session. Unfortunately at the end of session 2... I noticed a little oil. I borrowed some jack stands and a jack and took a look under there, but as is often the case, messing around with it kinda half cleaned it up, it was not conclusive where it was coming from. I decided to give it another go and see how it was. The amount of oil was maybe one/two small drops. I did another 20 minute session and car went well, and I was just starting to get into it and not be terrified of driving on track. I pulled over and checked in the pits and saw this: This is where I called it, packed up and went home as I live ~20 min from the track with a VERY VERY CLOSE EYE on Oil Pressure on the way home. The volume wasn't much but you never know. I checked it today when I had my own space/tools/time to find out what was going on, wanted to clean it up, run the car and see if any of the fittings from around the oil filter were causing it. I have like.. 5 fittings there, so I suspected one was (hopefully?) the culprit. It became immediately apparent as soon as I looked around more closely. 795d266d-a034-4b8c-89c9-d83860f5d00a.mp4       This is the R34 GTT oil sender connected via an adapter to an oil cooler block I have installed which runs AN lines to my cooler (and back). There's also an oil temp sensor on top.  Just after that video, I attempted to unthread the sensor to see if it's loose/worn and it disintegrated in my hand. So yes. I am glad I noticed that oil because it would appear that complete and utter catastrophic engine failure was about 1 second of engine runtime away. I did try to drill the fitting out, and only succeeded in drilling the middle hole much larger and now there's a... smooth hole in there with what looks like a damn sleeve still incredibly tight in there. Not really sure how to proceed from here. My options: 1) Find someone who can remove the stuck fitting, and use a steel adapter so it won't fatigue? (Female BSPT for the R34 sender to 1/8NPT male - HARD to find). IF it isn't possible to remove - Buy a new block ($320) and have someone tap a new 1/8NPT in the top of it ($????) and hope the steel adapter works better. 2) Buy a new block and give up on the OEM pressure sender for the dash entirely, and use the supplied 1/8 NPT for the oil temp sender. Having the oil pressure read 0 in the dash with the warning lamp will give me a lot of anxiety driving around. I do have the actual GM sensor/sender working, but it needs OBD2 as a gauge. If I'm datalogging I don't actually have a readout of what the gauge is currently displaying. 3) Other? Find a new location for the OEM sender? Though I don't know of anywhere that will work. I also don't know if a steel adapter is actually functionally smart here. It's clearly leveraged itself through vibration of the motor and snapped in half. This doesn't seem like a setup a smart person would replicate given the weight of the OEM sender. Still pretty happy being lucky for once and seeing this at the absolute last moment before bye bye motor in a big way, even if an adapter is apparently 6 weeks+ delivery and I have no way to free the current stuck/potentially destroyed threads in the current oil block.
×
×
  • Create New...