Help with installing an HPX slot style - blow thru maf -RB25

[godzilla_753]

Hello,

I have an rb25det neo s2 that I would like to run a HPX maf in a blow thru setup.
I bought this:

IMG_20140530_160714 by godzilla_753, on Flickr
IMG_20140530_160659 by godzilla_753, on Flickr
IMG_20140530_160640 by godzilla_753, on Flickr
IMG_20140530_160635 by godzilla_753, on Flickr

I would like to run it in a 2.75" straight portion of pipe (the cold side intercooler piping going up to intake manifold), I read through some of Matt's testing using the HPX, R35, and z32 maf. I havent seen any setups with this size tube though. I am planning on making around 400 HP, will this size of tube be adequate?

Also will I need anything else to go to blow thru? Currently Im using the OEM maf that came with the car.

Im not very familiar with the tuning portion unfortunately, I would like to be able to drive it to the tuner if possible (very slowly of course), can anyone kind of point me in the right direction with this? I havent read the nistune tuning how to pdf yet, but plan on going through it tonight. I read on some of the related threads that I would need to adjust the VQ map? I do have all necessary components installed to be able to to tune. My friend will be doing most of it on portion of back roads.

Any help would be greatly appreciated!

[Matt]

Nistune only has maps for the 3" tube size defined at this stage. The end of the MAF sensor needs to be in the centre of the tube.

I've run it up on my R34 but because I had to move K constant from 300 to 1300 it messed up TP and affected all my cold start etc

At this stage I've held off supporting HPX until I sort out the problem with K constant. At this time I've added another adjustment constant to Feature Pack 1 (being released this week) for S14/S14A/S15 SR20DET and will gradually add to other models including R34/WC34

So dont fit it just yet until I get mine sorted in my R34 and then I can release the maps and adjustments needed to get it working

Can you fit it as 3" on the intake side?

[godzilla_753]

I think I can, I was really hoping to run it as a blow through but if your still working things out with nistune I can run it on the intake side. To do this, would I need to still get a 6" tube and put it in front of the turbo?

If I can get it installed on the intake side as a suck through in front of the turbo, Will I be able to use it without any issues?

Also, do you by chance know the limits of the stock r34 maf?

[Matt]

Stock R34 MAF is about 230rwkw. R35 MAF is 300rwkw. Z32 MAF about 360-370rwkw depending on dyno and who you talk to

As mentioned I only have the curve verified for the 3" tubing. Once I get more time then I will experiment with otherwises. You need to have the correct offset mounting to make sure the end of the MAF is in the centre of the intake piping. Refer to the test section on this forum for notes on this

6" is way too big. At most about 4" down to 3". If you want the intake piping you will need a suitable mounting offset adaptor for the slot MAF and then need to put together a VQ map from scratch to support it

[skylinegtrhr]

You need to have the correct offset mounting to make sure the end of the MAF is in the centre of the intake piping. Refer to the test section on this forum for notes on this

so not sensing element in center but MAF it self should be in center of tube?



vs.



and this is image from topic about HPX:
viewtopic.php?f=12&t=1739&start=0

image link is broken but I found it in Google cash

[Matt]

The element itself should be in the center of the tube, otherwise its readings may be off

[godzilla_753]

Ahh I see, so the little plate adapter i bought wont really be suitable. Also I misstyped, meant to say 3" tube. Im going to give a shot, if it doesnt work ill report my findings, maybe help with the testing process. For now Ill shoot to install it blow thru on my intake side charge piping which is 2.75".

[godzilla_753]

Decided I want to get the car running and not mess around with the sensor and blow thru cars been sitting undriven for too long. Im gonna just use a Z32 and call it a day, but will hold onto the sensor and wait for updates. Thanks for the help Matt

[Matt]

No probs. I'll post updates when I get to testing changes on my R34

[supersayianjim]

hey o.p. how much did that sensor/plug cost you?? and no updates matt?

[Matt]

Last update on the dyno last week. I sent this to a customer:

We have been testing the HPX N1 is what we have been using with Nistune during our HPX testing from Nick @ Mass Air Direct. One of the main issues is that with such a massive airflow capacity these sensors can read (talking well over 400rwkw depending on tube size) it throws out the parameters in the Nissan ECU which is normally used for fuel adjustment (the K constant). For example the K constant cannot be increased enough on SR20s to allow usage of the HPX

On vehicles which can be modified, the result modifying K constant significantly subsequently affects all load parameters in the ECU affecting things like cold start, knock sensing, closed loop and throttle response. Matching MAF size against injector size to keep K constant close to the factory value is what we normally recommend to avoid such issues. Unfortunately the MAF range of the HPX (when using the full 64 point scale in the Nissan ECU) is too large

As a result over the last five months, I have been modifying ECU code as part of our Feature Pack to allow changes to the ECU using a new parameter added the Nissan code. I’ve added this for S14A SR20DET which was tested using a HPX last week successfully. The code modifications now need to be rolled out throughout the rest of the vehicle range where feasible (we support a lot of different ECUs)

I will be adding a calculator to the software for the HPX to add a calculator to assist with different tube size (including 4” for example) and adjust the airflow HP measurements based on user selection. Once this is ready I will be confident what we can start selling the HPX sensors for use with Nistune using the new Feature Pack software now that I have a workable solution for these sensors which exceed the 350rwkw when using Z32 MAFs previously

As it says.... You can modify the VQ map calcualtions to make it shorter and keep TP within the normal ranges. I'm adjusting the total injection multiplier instead of K on my S14 which worked well during that dyno session.

I'm putting the calcluations into the software to calculate for you (at the moment I'm using a spreadsheet and copy/pasting cells into the MAF translation (VQ) map

Making the map smaller means that you may be able to get away with adjusting K but not as much as if you used all 64 points in the VQ map