Q45 Maf Pointer

[leeroy_25]

Okay.. despite all the bad press I decided to give my Q45's a go on my RB26/30 build as I had them ready with piping wiring and the lot.

So by some trickery I worked out a way to calculate the required data to put in my RB26 Apexi MAF setup to suit the Q45's!

I must say to my surprise when I put them on a turned the key it fired up and idled beautifully.. Even seemed to rev cleanly. So After my trip to the dyno for a quick map and play we did some testing. I started with the stock MAF's ran it up and got a happy map.. Then I put on the Q45's. All was good other than they globally seemed to shift the fuelling quite a bit and make the entire map hugely rich!

My Tuner then showed me that we could get around this using the % values against the voltages in the MAF setup screen. This seemed to do the trick. Now after all done and running up basically fine. The only slight complaint I have is when we did a pull on the dyno and then lift of the throttle and pop it in neutral the engine revs drop and it stalls! You can catch it with a light rev back up. It's fine on the road as it is rear you rev it and then dip the clutch like that.. but it does get close sometimes! Has anyone got any ideas on how to get around this?? Maybe the voltage % values need adjusting back up in this area only as they are effecting the MAF effectiveness/resolution??

Also I have noticed that if you really jam the throttle quick it can hiccup a bit. but that also is not likely to happen in normal use and may not be related to the MAF's. Alternatively could be the same cause as above?

Any advise would be good as I am so close to having these working just fine it would appear!

Thank you

Lee

_____

[scotty nm35]

It sounds like the reversion I used to get when the bov was plumbed in at 90degrees, some would blow back up the pipe and through the afm causing it to stall. I dont know if its useful to you.

[STATUS]

Okay.. despite all the bad press I decided to give my Q45's a go on my RB26/30 build as I had them ready with piping wiring and the lot.

So by some trickery I worked out a way to calculate the required data to put in my RB26 Apexi MAF setup to suit the Q45's!

I must say to my surprise when I put them on a turned the key it fired up and idled beautifully.. Even seemed to rev cleanly. So After my trip to the dyno for a quick map and play we did some testing. I started with the stock MAF's ran it up and got a happy map.. Then I put on the Q45's. All was good other than they globally seemed to shift the fuelling quite a bit and make the entire map hugely rich!

My Tuner then showed me that we could get around this using the % values against the voltages in the MAF setup screen. This seemed to do the trick. Now after all done and running up basically fine. The only slight complaint I have is when we did a pull on the dyno and then lift of the throttle and pop it in neutral the engine revs drop and it stalls! You can catch it with a light rev back up. It's fine on the road as it is rear you rev it and then dip the clutch like that.. but it does get close sometimes! Has anyone got any ideas on how to get around this?? Maybe the voltage % values need adjusting back up in this area only as they are effecting the MAF effectiveness/resolution??

Also I have noticed that if you really jam the throttle quick it can hiccup a bit. but that also is not likely to happen in normal use and may not be related to the MAF's. Alternatively could be the same cause as above?

Any advise would be good as I am so close to having these working just fine it would appear!

Thank you

Lee

_____

they should not be using that global % change for starters..... there is a precise maf curve for those changes...

Your getting reversion and its generally twice as bad as z32 reversion, you can do a few tricks like change the scale on page 3, run 400rpm, 800rpm and 1200rpm as your bottom 3 scales and pull massive amounts of fuel fro these tables and interpolate them back to the idle position, generally i put the lowest ms i can in the whole 400rpm column as this stops the added fuel when it stumbles.

if you like email me you map and i will set it up.

[rob82]

they should not be using that global % change for starters..... there is a precise maf curve for those changes...

Your getting reversion and its generally twice as bad as z32 reversion, you can do a few tricks like change the scale on page 3, run 400rpm, 800rpm and 1200rpm as your bottom 3 scales and pull massive amounts of fuel fro these tables and interpolate them back to the idle position, generally i put the lowest ms i can in the whole 400rpm column as this stops the added fuel when it stumbles.

if you like email me you map and i will set it up.

The issue is still the reversion and its overfuelling becasue the MAF signal oscillates on the transition to closed throttle. You can reduce the fuel at this rpm/load point but then you will have a hole in the map at normal operation. They really need what the RB20det ECU's have which is a closed throttle fuel map vs rpm.

[leeroy_25]

Thanks for the info guy's.. I will try and get a copy of my MAF for starters. Just to clairfy I am not running a BOV? So I assume this reversion you mention is air trying to blow back out of the MAF when you lift off and the turbo slows? Would fitting a BOV improve the situation?

I am not sure what you mean Status for why not to use the global adjustments? I assumed these just shift the MAF graph up or down accordingly? Are you saying in fact the MAF readings should remain at 100% and the fuel map would need adjusting accordingly? I can see pro's and cons' either way. Assuming the fueling was correct on the Standard MAF's which it was I would imagine the adjustment would be needed on the MAF table to bring it all back into alignment or closer at least. Then fine tune the fuel map? I am not tuner don't get me wrong.. Just would like to learn the exact reasons why not to do something one way for my own knowledge.

Thank you

Lee

[JonnoHR31]

global adjustments is just a rough scaling of the afm. you need to change the afm tables to do it properly. datalogit has the q45 tables for rb25, should be able to just copy them across

[leeroy_25]

You say that but the Q45 on an RB25 is only running 1 MAF. If you look at the values for the other options on the RB25 Like the VG30 you will note that the numbers are different to the ones in the RB26 VG30 option. So to let out my secret! I basically found the common scaling factor between the common MAF's in the RB25 and RB26 datalogit tables and then worked out the Q45 MAF table from that. Maybe my scale is wrong so all my numbers are out an amount? Maybe the scaling is not linear in that way from RB25 to RB26.. It did seem to work on the other checks I made?

Maybe I should post up a screen dump of the MAF table from my datalogit screen for discussion? If I understand you correctly you thin that if for instance I have had to use a % value of 80% in the voltage boxes I need to make that 100% again and then scale every different voltage cell in the MAF table by the appropriate %?

Can you please clarify how this is different to using the global voltage scaling? Does that have an impact on something else?

I must say I drove the car today and it is way smoother than it ever was on the Stock MAF's! I have not managed to stall it driving yet as like I said before you don't tend to just put your foot on the clutch from high rpm! You only really notice something is not quite right when you change gear slow giving the revs a chance to die right down.

Grateful for the advise by the way guy's..

Thank you

Lee

[leeroy_25]

they should not be using that global % change for starters..... there is a precise maf curve for those changes...

Your getting reversion and its generally twice as bad as z32 reversion, you can do a few tricks like change the scale on page 3, run 400rpm, 800rpm and 1200rpm as your bottom 3 scales and pull massive amounts of fuel fro these tables and interpolate them back to the idle position, generally i put the lowest ms i can in the whole 400rpm column as this stops the added fuel when it stumbles.

if you like email me you map and i will set it up.

Hi Status,

I have made a bit of progress tunning.. But not enough!.. Can you send me a pm of your e-mail address so I can drop you a mail.

Thank you

Lee

[STATUS]

Thanks for the info guy's.. I will try and get a copy of my MAF for starters. Just to clairfy I am not running a BOV? So I assume this reversion you mention is air trying to blow back out of the MAF when you lift off and the turbo slows? Would fitting a BOV improve the situation?

I am not sure what you mean Status for why not to use the global adjustments? I assumed these just shift the MAF graph up or down accordingly? Are you saying in fact the MAF readings should remain at 100% and the fuel map would need adjusting accordingly? I can see pro's and cons' either way. Assuming the fueling was correct on the Standard MAF's which it was I would imagine the adjustment would be needed on the MAF table to bring it all back into alignment or closer at least. Then fine tune the fuel map? I am not tuner don't get me wrong.. Just would like to learn the exact reasons why not to do something one way for my own knowledge.

Thank you

Lee

there is a whole precise table about 50mm below the global adjustment that will get your afm curve spot on.

[caaraa]

It sounds like the reversion

[leeroy_25]

Hi There,

This very big table is what I have populated with my calculated numbers in the first place. So if I have say 80% in the global adjustment range for one voltage set do I just take 80% of the value of the figures in the table for that voltage range?

Can you maybe give me a pointer a to what your chart starts at for Q45's and what it ends at just to give me an idea of where I am going? I can try and post a screen shot later.

Thank you

Lee

[leeroy_25]

Okay.. So here is a screen dump of my current MAF table page:

I would really really appreciate some advice on this.. I took me ages to get the table I have and the graph is very nice and smooth! I guess just all pretty much needs shifting down I assume? So I want to be sure I do it correctly and ideally would love some key figures I can plug in to guide me. Status.. really hoping you will be so kind.

Could these MAF setup issues explain the AFR's globally dropping between 2 consecutive runs with no relevant map alteration? I am guessing not but just in case! If you look at my dyno post you will see what I mean! http://www.skylinesaustralia.com/forums/topic/370573-rb3026-final-tune-feedback/page__p__5910636__fromsearch__1#entry5910636

Thank you

Lee

[leeroy_25]

Pretty please!

[rob82]

The problem with percentage changes is that most MAF have a non linear transfer. ie - its expotential.

Have you setup your fuel table to resemble a commanded AFR map?

[JonnoHR31]

you need to set the global adjustments back to 100% and adjust the 32 point table at the bottom. i'd set it up under airflow 5. you can find the figures for a single q45 (vh41 in fc edit) in the sample rb25det map that comes with fc edit. not sure if the 26 pfc needs the singular airflow figures or multiplied figures to allow for 2 afms though.

Edited July 14, 2011 by JonnoHR31

[Cubes]

Just to clairfy I am not running a BOV?

Your never going to get away from the want to stall issue with MAF if your running no BOV. Not in my experience anyway.

Run a quick MAF/load point trace and you will see the reversion when you jump off the throttle. Learn to drive with it its really not difficult to prevent it stalling, a quick blip is all thats required.

The benefits of no bov vs a bov IMO far outweighs the negatives. Unless your missus drives the car.

Even then mine worked it out quickly enough and commented on how much more responsive it was when grabbing that next gear.

I run an Rb26 PFC on my R32 GTST RB30DET with a single Z32 MAF. I simply punch in 50% scaling and then tune. It starts/idles/part throttles and WOTs perfectly with 11l/100km. No popping farting or carrying on. Only issues I experience are due to reversion of no BOV.

[leeroy_25]

Thanks for the replies again.

First off Rob.. I see the graph is an exponential curve and non linear. Not sure why that matters on a percentage change? Surely that just moves the curve up or down generally. Or maybe where the percentages are not the same that gives jumps between each voltage range? Next I am not sure what you mean about the commanded fuel map? My tuner has adjusted the fuelling to suit the current setup using datalogit? Please elaborate and I will try and reply with a useful answer!

Jono, I will set the global adjustment back to 100% and go through altering the 32 table values by the appropriate % for the voltage. Then I can lock the x values and smooth out the curve? Sounds good so far? Would be very nice to know a starting and maybe ending value so I can work out inbetween though. Please can someone give me this info? I chose to put it in Airflow 3 as I know I will never use that. Left the VG30 (Airflow 5) slot in case I ever got Z32's! I assume the line you choose to alter is erelevant? I am pretty sure that you cannot just use the RB25 values as if you look at the other common MAF's between RB26 and RB25 in FC edit you will note they are not the same from one to the other.. This was how I determined a scale factor to work out the Q45 values in the first place.. Clearly the scaling is not a linear factor though and hasn't quite worked out! It definitely needs some kind of multiple but it is not 2 or as I said I don't think it is indeed linear full stop. I guess you would have to work out the difference in airflow volumes and it might be something related to that?

This may or may not be related but I noticed while monitoring injector duty that when you are driving along normally and lift off the throttle to change gear otr stop the duty falls completely to 0.0%? Is that normal as that implies the injectors are not putitng any fuel in? If you are going really slow then it maintains a low %? Just wanted to get that clarified as normal or not!!

Please keep the info coming

Thank you

Lee

[leeroy_25]

Just saw your reply there cubes!

I am not too worried about it as it is pretty hard to stall it to be honest.. Just it would be nice to get over it if possible! if not then so be it.. I could fit a BOV I guess but prefer it without as well!

How did you wire a single MAF with an RB26 Power FC??

Cheers

Lee

[STATUS]

Just saw your reply there cubes!

I am not too worried about it as it is pretty hard to stall it to be honest.. Just it would be nice to get over it if possible! if not then so be it.. I could fit a BOV I guess but prefer it without as well!

How did you wire a single MAF with an RB26 Power FC??

Cheers

Lee

just common the maf wires to the ecu.

[Guilt-Toy]

why don't you try something different?

How close is your AFM to the turbo?

Make a new pipe and put the AFM as far away from the turbo as possible and then re-test.

I found putting it down infront of the front bar gave me good results, but be carefull dont put it in direct air flow that can cause you problems as I found out years ago

Also make sure you TIE it and make it very secure, running over your AFM and air filter sucks.