R32 GT-R Fuel Economy

[BourneToLive]

Hey, as usual, I’ve tried looking for answers on my specific problem, but haven’t found one, yet. 
 

I’ve had my R32 for just over 7 months and it has terrible fuel economy. My tank is nearly empty after only about 170km. When I first got the car, it had misfires; and I did everything I could to fix any issue that would have affected my fuel economy, except for buying new fuel injectors.
 

My car runs rich. I suspected a fuel leak or an exhaust leak somewhere, but my mechanic assured me my car was fine. I even got a new tune for better fuel-to-air ratio and I am still having to fill up everyone 150-175km. Also, my fuel gauge fluctuates. 
 

I’m stumped. 

[Murray_Calavera]

A few things, it's really hard to use KM per 'tank' as a measure of economy. No one runs the tank to completely empty then fills up again so the number is subjective. Please give us the L per 100 KM figure. 

You mention you got your car tuned for a better AFR, what ECU and mods do you have? 

Have you fixed the misfire? 

What do you mean your fuel gauge fluctuates?

[KiwiRS4T]

As above you need to be a bit more scientific. Clearly you can't rely on your fuel gauge so you need to fill your tank to the top, record the km and then next time you fill it calculate the litres per 100km. What are all the things you did to improve economy? New spark plugs and coils? Check brakes for binding? Check timing?  Did the mechanic put an AFR meter on and if so what were the numbers (or do you have a wide band installed)?

[GTSBoy]

No mention of checking the ECU's water temperature sender.

No mention of replacing the oxy sensor.

No mention of checking for a severe blockage at the cat.

No mention of looking for boost leaks.

[niZmO_Man]

14L/100km is the norm, on a good day. If you already had a tune, your tuner should be able to diagnose the poor fuel economy.

[blind_elk]

Worst thing for fuel economy in a GT-R is the enormous lump of lead at the end of your right leg. Lighten it off a bit. No need to be red-lining from every set of traffic lights.

[GTSBoy]

I'm now down to flat 10s in my 25Neo R32.

/humblebrag.

[niZmO_Man]

On 16/02/2020 at 11:16 PM, GTSBoy said:

I'm now down to flat 10s in my 25Neo R32.

/humblebrag.

My R32 GTS-t easily did 9L/100km with just R34 turbo, everything else standard (including exhaust). Damn I miss that car

[joshuaho96]

On 2/16/2020 at 12:23 AM, blind_elk said:

Worst thing for fuel economy in a GT-R is the enormous lump of lead at the end of your right leg. Lighten it off a bit. No need to be red-lining from every set of traffic lights.

Has anyone actually done a BSFC map of the RB26? I'm sure it's going to be ugly but curious to know what the ideal operating points are.

[KiwiRS4T]

My Stagea with an RB30 and GT3540 would do 8-9 L/100km on a trip. Round town it would vary from 12 to 14L /100 depending on where I was going and how I was driving. RBs are not for economy runs!

[BourneToLive]

Sorry for the super late response. A lot of things went wrong with the car all at once and had to make changes/upgrades to it. Since then, I have upgrades to a high-flow Nismo fuel pump, NZEFI 1000cc injectors, GT2860r-5 twins, stock rail and FPR, R35 Coils and Haltech Platinum Pro ECU.

The car has been my daily for the last four months, so I can’t afford to do pulls and risk something breaking. Around the time of this post, I had a Djetro Apexi ECU, and when I installed the R35 coils and 1000cc injectors, I had decently good fuel economy. But when I changed to the Haltech ECU, my fuel economy went downhill. I’ve been tuning the basemap to my application, but no matter what I tinker with, I can’t improve fuel economy. I’ve tuned the injector flow rates, injector dead times, dwell times, target AFR, base fuel map, coolant temp corrections, Idle duty cycle, transient throttle (throttle pump). My wideband reads 14.2 at idle and 13.8-14.1 cruising (2000-3000rpm). I get constant rich bank warnings while idling at 14.2 AFR. It’s probably a timing issue but I don’t understand that kind of stuff enough to be tuning it, so I’m not touching that. 
 

I understand that GTRs are not the most economical cars, but I’m pretty sure mine is way below any of your guys’ cars. That’s why I’m concerned. Everyone here seems to average 14L/100km, but I burn about, what seems like, 14L/25-50km. 

[joshuaho96]

Even 14 L/100km is pretty awful, I get about 11L/100km, 9.5-10 L/100km should be achievable purely doing motorway driving. I'm pretty sure your problem is your ECU tune. You should be able to command lambda 1 and get lambda 1, it's really that simple. If it isn't happening something is wrong with the modeling of your engine in the tune. Feel free to post some logs from idle/cruise.

[BourneToLive]

I attached a datalog from a couple nights ago. If you have the haltech ECU manager and you can view it, let me know what you see. I'm not experienced in the tuning scene. I'm learning as I go. There are a couple of lean spots from rough take-offs at stop lights. You'll probably see that.  

Usual Route Data Log - Haltech Plat Pro - BNR32 GTR.csv

Edited January 1, 2022 by BourneToLive

[joshuaho96]

On 12/31/2021 at 11:19 PM, BourneToLive said:

I attached a datalog from a couple nights ago. If you have the haltech ECU manager and you can view it, let me know what you see. I'm not experienced in the tuning scene. I'm learning as I go. There are a couple of lean spots from rough take-offs at stop lights. You'll probably see that.  

Usual Route Data Log - Haltech Plat Pro - BNR32 GTR.csv 2.59 MB · 1 download

I'm not going to pretend I'm some expert here and without your ECU map in addition to the logs it's hard to figure out exactly what the ECU is "thinking" when certain things occur. At 4:09 in this log I think what I'm seeing is bad transient throttle mapping, there's a sharp lean-out followed by a sudden rush of fuel too late as it enriches. That is purely in the synchronous fuel enrichment tables. The one time you do a bit of a pull to 3500 RPM at 7:53 in the log goes pretty rich, 0.8 lambda when it commands 0.91 lambda. I'm not sure if it should be that rich and it goes very rich too, seemingly just from the 23-26 percent TPS percent change. I'm also not sure why the target AFR is 0.97 lambda almost everywhere. If you want lambda 1 you should be setting that in the target AFR tables. Also I think your after-start enrichment when the coolant temp is warm seems really extreme, you're at like 0.75 lambda at idle which is just a ton of fuel to be dumping for a warm start. I think this picture sums up the issue pretty well, I think:

Also, why is ignition timing -27 degrees at 6:20? Something seems broken there, likely an electrical fault. Your ignition timing maybe looks fine, I have the OEM timing and fuel tables but it's really hard to translate it to a kPa load, I'd need to know the actual cylinder filling based upon that load which is not truly linear. There might be a bit more timing in there but without more testing it's kind of hard to say.

The other thing is that I notice you don't have DFCO enabled. Once you get map development figured out I would start using it so your fuel economy gets a lot better. Honestly speaking your situation is one I'm hoping to avoid in my own tuning, my current plan is to use MAF-based tuning in Haltech's ECU tuning setup to hopefully be able to replicate the OEM maps so the car is driving properly from the start and I can go from there. If you still have the MAF sensors and your setup is mostly OEM then I might be able to help you get going. I'm not a professional tuner though, strong emphasis on this basically being "blind leading the blind". I can only help with getting your base map into a better place, it's no replacement for actually getting a dyno tune to optimize ignition timing/AFR at higher RPMs. The big unknown I need to figure out myself is transients, with MAFs it's much harder compared to the MAP/TPS blend you see in the Haltech base map.

[BourneToLive]

On 1/3/2022 at 7:12 PM, joshuaho96 said:

I'm not going to pretend I'm some expert here and without your ECU map in addition to the logs it's hard to figure out exactly what the ECU is "thinking" when certain things occur. At 4:09 in this log I think what I'm seeing is bad transient throttle mapping, there's a sharp lean-out followed by a sudden rush of fuel too late as it enriches. That is purely in the synchronous fuel enrichment tables. The one time you do a bit of a pull to 3500 RPM at 7:53 in the log goes pretty rich, 0.8 lambda when it commands 0.91 lambda. I'm not sure if it should be that rich and it goes very rich too, seemingly just from the 23-26 percent TPS percent change. I'm also not sure why the target AFR is 0.97 lambda almost everywhere. If you want lambda 1 you should be setting that in the target AFR tables. Also I think your after-start enrichment when the coolant temp is warm seems really extreme, you're at like 0.75 lambda at idle which is just a ton of fuel to be dumping for a warm start. I think this picture sums up the issue pretty well, I think:

Also, why is ignition timing -27 degrees at 6:20? Something seems broken there, likely an electrical fault. Your ignition timing maybe looks fine, I have the OEM timing and fuel tables but it's really hard to translate it to a kPa load, I'd need to know the actual cylinder filling based upon that load which is not truly linear. There might be a bit more timing in there but without more testing it's kind of hard to say.

The other thing is that I notice you don't have DFCO enabled. Once you get map development figured out I would start using it so your fuel economy gets a lot better. Honestly speaking your situation is one I'm hoping to avoid in my own tuning, my current plan is to use MAF-based tuning in Haltech's ECU tuning setup to hopefully be able to replicate the OEM maps so the car is driving properly from the start and I can go from there. If you still have the MAF sensors and your setup is mostly OEM then I might be able to help you get going. I'm not a professional tuner though, strong emphasis on this basically being "blind leading the blind". I can only help with getting your base map into a better place, it's no replacement for actually getting a dyno tune to optimize ignition timing/AFR at higher RPMs. The big unknown I need to figure out myself is transients, with MAFs it's much harder compared to the MAP/TPS blend you see in the Haltech base map.

Thanks for looking at the log. So, if you want, I can send you the map I’m using. It’s a Haltech base map that I’ve been tuning. For the rich post-start when warm, that’s the setting that doesn’t make my AFR go extremely lean. It wasn’t that rich originally, but my AFR was at 20+. Even with the current post start settings, it goes to 15.5 AFR. This is only on warm starts. 
 

For transient throttle, I’m still messing with that. I’ll give DFCO a try. A lot of the settings here I haven’t messed with because I don’t understand them. I deleted the MAFs because they were on the way out and it was cheaper to use a MAP sensor than buy new MAFs. As for the timing, I have no clue. I haven’t touched that part of the map. Lol 

Also, I try keeping my idle AFR at 14.2 and cruise at 14.1. 

 

Edited January 3, 2022 by BourneToLive

[joshuaho96]

On 1/3/2022 at 3:07 AM, BourneToLive said:

Thanks for looking at the log. So, if you want, I can send you the map I’m using. It’s a Haltech base map that I’ve been tuning. For the rich post-start when warm, that’s the setting that doesn’t make my AFR go extremely lean. It wasn’t that rich originally, but my AFR was at 20+. Even with the current post start settings, it goes to 15.5 AFR. This is only on warm starts. 
 

For transient throttle, I’m still messing with that. I’ll give DFCO a try. A lot of the settings here I haven’t messed with because I don’t understand them. I deleted the MAFs because they were on the way out and it was cheaper to use a MAP sensor than buy new MAFs. As for the timing, I have no clue. I haven’t touched that part of the map. Lol 

Also, I try keeping my idle AFR at 14.2 and cruise at 14.1. 

 

If you have a catalytic converter you're going to melt it if you keep running it rich like that. Also you're just wasting fuel for no real reason. The factory ECU idles a touch lean I believe and cruises at lambda 1 until you hit boost.

[Dose Pipe Sutututu]

On 04/01/2022 at 6:30 AM, joshuaho96 said:

If you have a catalytic converter you're going to melt it if you keep running it rich like that

On the contrary, running rich actually cools everything down.

 

[Ben C34]

On 1/4/2022 at 8:58 AM, Dose Pipe Sutututu said:

On the contrary, running rich actually cools everything down.

 

Except a cat!

[BourneToLive]

I don’t use a cat. I have a test pipe with my wideband O2 sensor on it and I disabled my OEM narrowband sensors that are on the turbo outlet pipes. Funny thing that happened recently, I did the same thing with my MAFs in Haltech’s ECU Manager, but I left them plugged it up until three days ago. When I unplugged them, I put about 4000yen worth of high octane gas (65AUD), and it seemed to have been the problem to my fuel economy issue after the new ECU install. After three days, I’ve driven about 60km on it and my fuel gauge moved only about a millimeter or two. I left my OEM sensors plugged in as well after disabling them. I wonder if that’s messing with my AFR readings. 

[joshuaho96]

Your logs indicated some kind of electrical issue visible to the ECU so it’s very possible yes.