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UpRev K multiplier and Data Word MAF values

Practical Reflash Tuning

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I’m currently tuning a built / modified NA Nissan / Infiniti VQ35HR that has the stock dual MAF sensors, a dual CAI with same as stock diameter intake pipes, and ID1050X (1,060cc/min) fuel injectors. Does anyone know a formula for precisely calculating or rescaling the “K Multiplier”? I’ve seen (old injector size / new injector size) * original K Multiplier, but the number I get from doing this is so low (and leaned out) the engine won’t start. It also dies when I approach that calculated value (about 8093). The stock value is 26808 and the stock injectors are approximately 320cc/min. It starts with idle trouble when I use a range between about 13,000 and 16,000, but I haven’t been able to dial it in.

I’m also wondering if there is any direct / applied math that will allow tuning or rescaling the MAF tables, aside from large amounts of logging, looking at AFRs, and reflashing. The MAF tables use voltage on one side of the table related to “Data Word” on the other (I’m seeing values starting from 400 or 700 and ending at 65535).

The Injector Minimum has been set to 0.300ms and the Injector Latency chart is set according to Injector Dynamics’ data sheet.

I’ve been having a bit of trouble getting it to keep a low enough and stable idle.

Any help is appreciated,


General work flow for these situations, unless it is absolutely unavoidable, is to not try and scale MAF and scale injectors at the same time. You'll chase your tail. Put the stock air intake back in, use the stock MAF scaling first as at least it's close enough. Or if you can't do that, put the stock injectors in, scale the MAF, then put the new injectors in.

Were the injectors maxed out? Do you really need to change them out on a naturally aspirated car with bolt ons? Also, 1060cc is HUGE for an n/a injector on a 6 cylinder. That's twice the size of a stock 2JZ Supra injector. Are you running E85? That makes it even more difficult because ethanol vaporizes poorly and is known for bad starting.

You've got to break it down into one thing at a time unless you are very time constrained and must skip steps. Scale the MAF with the new intake first (hell, scale it with the stock MAF first as there is always some room for rescaling). Tune it on stock injectors unless they are totally maxed out. Then swap injectors, and to get it to run on E0/E10 first. Do E85 with the modified MAF scaling last.

"I’m also wondering if there is any direct / applied math that will allow tuning or rescaling the MAF tables, aside from large amounts of logging, looking at AFRs, and reflashing."

Welcome to tuning my friend. Excel formulas are never as good as experimental data.

Thanks for your reply. I’m aware of the workflow involving tuning one before the other, what I’m asking for is specific information related to tuning a Nissan / Infiniti vehicle exclusively using the UpRev reflash platform. Someone experienced in tuning with UpRev (an authorized dealer or tuner) would probably know certain shortcuts to get close enough to start. Unfortunately, I’m a bit pressed for time and a ways away from a dyno (or a good date to rent one) which just makes things worse.

My apologies, I probably should have asked if anyone knows a way of mathematically scaling the K Multiplier and other basic parameters to obtain a set of reasonably accurate ballpark figures that I can begin fine tuning those parameters from. The CAI is very close to the stock setup (it’s the same diameter and runs fine on stock vehicles with no tune at all), so I would like to think it is already close and it wouldn’t require MAF tables to be tuned until later. I’m seeking a way to obtain (relatively) close ballpark figures before approaching the side of fine tuning with experimental data.

I don’t use Excel spreadsheet based calculators because I probably don’t tune enough vehicles to warrant putting one together. I prefer a good set of formulae, hashing them out on paper, then fine tuning, but at the same time I’m not looking to get involved with partial applied differential equations and making attempts at calculating out theoretical data with absolute precision (I know this is usually next to, if not impossible). Once close enough for me, I prefer moving into collecting data and applying it. Do you (or anyone here) know how I can go about this? I want to say that simple and “close enough” (without being thousands of units off) is good enough as opposed to being dead on target to the single digit (which I understand might be extraordinarily difficult if not damn near impossible).

Some more information about the build, without going into a giant amount of detail: We built the engine to squeeze every possible ounce of HP and TQ out of it without using forced induction just yet. It’s not a bolt-on only build. It’s a fully built block with slighty raised compression with a no expense spared ported, dimpled, set of heads with mild cams, springs, Ti retainers, new DLC coated buckets, etc. We maxed out the stock injectors the first time on the dyno. Our approach to this build is to do it in stages and leave overhead / keep options open for later.

We might design and install a custom supercharger system at a later date and we would rather get it out of the way now as opposed to having to buy fuel injectors twice. With that said, it is my experience that some extra overhead (while this is a pinch excessive for the current configuration) won’t hurt anything so long as the injectors can handle that small a pulse width for idling. Injector Dynamics produces this type of injector, and it’s made in a partnership with Bosch. I trust that. They also have 750’s, but they were discontinued for some reason. I generally don’t like purchasing discontinued products (it’s personal preference).

The vehicle is running E10 gasoline. While E85 might or might not be a good idea in the future, we want to steer clear of it for now. A parallel standalone ECU installation may be in order sooner or later, but we’ll cross that road if and when necessary.


The MAF scaling table uses a dimensionless airflow unit that is directly related to mass airflow in kilograms per hour. There's also an rpm vs throttle angle vs correction factor map applied on top of it that corrects the theoretical pulsewidth and charging efficiency calculations used in spark tables etc. I'm not sure if uprev gives access to that correction table. Unless you zero out that table, you don't really know what's going on behind the scenes. You just have to guess and check, brute force datalogging method.

You also have to keep in mind that the engine could be ok when warm and just need a retune of wall wetting and combustion stability enrichment for cold running. As I mentioned before, you have to go in the right order. Cold starting isn't priority right now. Get it to warm up using the 13000 k factor setting and check your short and long term fuel trims with the engine warm. From there use the fuel trims to guide your adjustments. Then you just have to guess whether the fuel orthe MAF scaling needs to be changed to get there, because changing both at the same time puts you in a bind. The cams can mess up stuff because now you've got a different pulsation effect in the intake manifold, and the MBT spark point will have shifted. So now you need more air to make torque, which changes the throttle angle, which puts you into a different cell in the airflow correction map.

Can you post screenshots of all your injector and MAF scaling,ing settings? Also, I'm not clear on the idle. Is it idling too high or too low? Sounds like you have to raise the idle to stabilize it.. Try advancing spark to stabilize the combustion: less air, more spark. The cams introduce more internal EGR and dilute the mixture.

If you put the stock injectors back in you will actually save time in the end. Put them in, scale the MAF and adjust tune throttle and idle/cold start. Just don't rev it all the way out to peak power for now.

Peak power is easy to tune and is low priority. Get the thing running well on stock injectors, then swap them and tune more. You've got intake and exhaust variable valve timing and you changed the cams. It's a complicated enough engine.

Thanks for the info. When you put it in those terms, the idea of “Data Word” was easier to grasp.

I put the stock injectors back in, but I still have a high idle and ticking noise coming from my passenger side exhaust manifold (loud noise in the wheel well area). It’s one of those ghost like problems with no other symptoms than it happening at once warmed up and not going away unless parked for 2+ days. I can cool it down the same day, start it up, and have the noise around while cold and warm. But when I leave it alone for a few days, the noise will go away when cold and come back when warmed up and driven for a short time.

I have to figure this out before tuning the MAF sensors and swapping the ID1050X injectors back in. I’m currently running the old tune.

Is it ok if I come back around and post pictures once I get the MAF sensor tables tuned and the new fuel injectors back in, or should I post the other tables now (from the 1,060cc/min. injectors).

There are a few different tuning softwares out there like Nistune, TunerproRT and Cobb depending on application etc and I don't remember what settings Uprev gives access to for this engine in particular. So if you can post maybe a PDF of the help file that describes tables and recordable parameters it would help.

Screenshots of idle, MAF, and injector tables would help too.

For example, for idle there are feed forward base airflow tables, airflow feedback limits, spark timing feedback, and feed forward idle spark, feed forward airflow accessory compensation... but i need to see what you have available to log and tune.

I was able to find a manual, but some if it seems to be outdated and irrelevant to the new software..


I also found a Nissan tuning guide from a while ago, but it’s geared towards the GTR.


Below is a .PDF file with the pictures of all UpRev accessible maps, tables, settings, etc. I decided to make a .PDF because there are 46-48 pics in total. All available logging options are in the last two pictures.

The data in the .PDF is from when I had the 1,060cc/min injectors installed.

I believe part of the problem I had with the high idle had to do with taking the intake and throttle bodies off without performing the Idle Air Volume Relearn (via Consult or the “pedal dance”) after each time I removed or installed injectors. I’ve learned that Nissan / Infiniti tuners and owners should do this each time the DBW TBs are unplugged and plugged back in and after each tune... especially those of us who don’t unplug the negative battery terminal when doing minor work in the engine bay.

Attached Files

Ok, this is VERY helpful.

Here's some things to keep in mind when datalogging. A/F Correction is short term fuel trim, A/F ADJ is long term fuel trim (or maybe I have that reversed, double check). So you need to keep an eye on both. Ideally you want the long term fuel trims to stay within at least 5%.

The main tables for MAF sensor and airflow are going to be "Map 1 Mass Air flow sensor" (A and B, for each bank). You can adjust them both the same at first. The other table is the Map 1 Fuel Compensation. So the ECU is going to look at the mass air flow sensor look up table first, based on sensor voltage. Then it's going to modify the airflow further (or rather, the base fuel schedule, which is based on the airflow) based on the Map 1 fuel compensation. Fuel Compensation says "Data byte" for X axis, but that is basically throttle position (not accelerator pedal, throttle position). It's proportional to throttle position anyway, but it's not a fully linear relationship between this value and throttle opening angle. I believe "Fuel Compensation X trace" will help you figure out where you are on that table, but also look at Throttle X trace.

The whole point of the scaling and fuel compensation is to get the actual A/F ratio closer to the target A/F ratio in open loop and to reduce the fuel trims in closed loop.

So you want to start by flattening out the Fuel Compensation table (set it all to 100) since you don't have the original air induction system. Optionally, set your Map 1 fuel target to some fixed values in the heavier loads as indicated by the tuning guide. Then adjust your MAF scaling tables for both banks. So for example, adjust between 0 and 3 volts by +3% or something to bring your fuel trims closer to zero. Then adjust by bank if necessary... if one bank is consistently leaner than the other, adjust the MAF scaling for that bank (optionally you can trim cylinders with Map 1 cylinder trim but that makes it more complicated). If you need to zero in on a specific speed and load to reduce fuel trims or reach a target AFR, use the Fuel Compensation table. Keep in mind however that these changes to the fuel compensation table and MAF scaling will change the calculated load and base fuel schedule calculation, which then throws off a lot of stuff such as spark. So you have to get this right first.

The Map 1 torque management estimated torque delivered is going to change a little bit too, since the load axis is the base fuel calculation calculation. Map 1 Torque management estimated torque is going to affect transmission behavior. Map 1 electronic throttle (estimated torque delivered as well) isn't going to affect the transmission, that's used for traction control.

So you want to have the MAF and Fuel compensation tables tuned, and your fuel trims not too far off, and your air fuel ratio targets are being achieved (i'm assuming you have some kind of Bosch sensor based wideband, as the stock widebandish Denso sensor isn't that accurate in the rich range but is ok between maybe 13.0 and 14.7:1). Then I would put in the new injectors and the latency settings you have. Notice that for the new injectors latency, it's actually only two settings: base 14V setting and a slope setting. So it's not a precise thing.

At that point with the new injectors I would play with the K setting a little bit to get in the ball park based on fuel trims and AFR. I would not mess with the MAF scaling tables, only the K factor and if necessary the fuel compensation table. Then you can adjust ignition and VTC and target AFR to get more power out of it. For idle, you're pretty limited. I don't see a lot of tables in there, just idle target.

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