ID1000 Tuning


New member
I've been trying to get a handle on a set of ID1000s I recently installed and I wanted to make sure I'm going about it the right way. Mods are the following:

Perrinn E4 header
Grimspeed catted downpipe
Cobb FPR
AEM drop-in filter

Using the stock maf scaling and the injector data from here fuel trims at idle were lean by 8% or so which decreased as the base pulse width got longer. It is also slightly rich in OL but only by 2%, I'm guessing this is caused by the header and not the injector characterization. To compensate for this I added 7% to the latency values which brought the idle trims back to 0 but it still appears slightly lean in the midrange, 2-4%. This had no effect on the OL fueling which is to be expected.

Has anyone else had a similar experience in having to increase the latency that much? According to the data sheets that's to be expected in the 60psi base pressure range. I'm also wondering how good is the stock maf scaling is. Can I assume it is correct and attempt to minimize AF corrections using the injector settings?

My first attempt at this was the same setup with a ks tech 73mm intake. Based on what a local protuner gave me for maf scaling advice my injector scaler was 7% higher but the recommended latency values worked well. My fuel trims were pretty good but this felt wrong as the calculated load values were way down from where they were with the stock intake.
I have encountered this many a time. Keep in mind that the numbers given in the data sheets are starting point only and the final results may differ. 7% actually does not sound bad at first. To complicate things, the stock MAF is okay if the car is left entirely stock and generally requires no scaling, but change one thing and you can throw that out the window especially if the change occurred just before or just after the MAF. Also if the car is not well maintained it can have a profound effect. Please check for leaks and zip tie every hose, Clean the MAF with some electrical contact cleaner and clean or replace your air filter.

That said, I usually use the latency values given form ID and rarely ever have need to adjust them further. The most I have ever done was 5%. The approach I would take to maintian load values is to make rough adjustments to injector scale to bring most of the fuel trims to float between + and - numbers. Then make the fine adjustments with MAF scaling, even the idle.

What I do is I take a log in each gear with slow and long sweeping runs in each gear up to 4000 rpm or what ever I can reach on the street. I will do this for about 10 minutes of driving time. Then I will filter out all the OL data and all of the other bad data like any fuel trim above or below 14%/-14% and any AFR above or below 16/13. Then I will run it through a special spreadsheet which I will provide a link to. The key is to plot the data and look at the slope of the results to indicate whether you need to add or remove latency or add or remove scaling.

If you see that your average fuel trims are low in the idle region and then climb as the airflow and RPM increase, Then you have to remove latency to bring the idle region in line with the high end of the MAF. If the opposite is true and the trims are high in the idle region and low as RPM and air flow increases, then you need to add latency to bring the idle region in line with the high end of the MAF. Then once you get the over all slope to be fairly straight, then you can bring the trims closer to zero by either making a global adjustment to MAF scale or injector scale. Which ever one will achieve the correct calculated load. If by chance the idle region is significantly lower or higher than the rest, and the entire rest of the fuel trim range is fairly straight, then you need only adjust the idle region of the MAF.

Below is a copy of my spreadsheet. It is a derivation of one that has been floating around on RomRaider for years and has paid me well over the years. I am sure you will have questions and I am here to answer them as needed. Remember to copy and past your current MAF scale into the results screen prior to ever use and make sure the voltages are correct also prior to use. It is fully automatic if you setup your logs properly but it can be fussy if you don't know how to use it, so yeah... I'm sure you will have questions. :tup:


New member
Lots of great info here, thanks! I'll throw the stock filter back in then give the spread sheet a go and report back. I do have another question that is somewhat related to this. I have been chasing a lean spot around 3200 rpm at low load, 14.7 > 16 ish. When I asked Cobb about it they said it was a drop in differential fuel pressure and a known problem with their fpr setup. Their stage 3 OTS maps confirm this as they have some pretty aggressive compensations in the per injector ipw tables. (Frustrated that their fix for the gr stumble just moves the issue further up the rpm band but that's for another time.) I'm guessing there's nothing I can do about this other than ignore it and adjust the per injector ipw values last? At least until they re-release ATR and bring custom features directly to the consumer.
Oh but you can fix it! Method one will have you adjust the load compensation table to compensate for the stumble. Most of the time this eliminates the issue or reduces it till it is hardly noticeable. If that doesn't work then method two is a fuel line and FPR kit that can be used to reconfigure the delivery of fuel to the rails effectively eliminating the differential issue. I believe Cobb sells such a kit and I wonder why they did not mention it.

Just FYI, This is a known problem from the factory and Cobb parts usually fix this. The problem is with the factory FPR and feedline configuration.


New member
I feel there may have been some miscommunication here :) With the factory FPR I was having the known stumbling issue around 2200-2400. I installed Cobbs newer FPR kit with the reference pressure relocation and now have the lean spot around 3200-3400 instead of 2400 but only at low load. In talking with them they basically said that their kit makes the issue much more manageable but does not totally resolve it. Hence the need for per injector pulse width compensations as seen in the OTS maps. This is recommended over load compensation as it does not affect calculated load. The ideal solution is differential fuel pressure compensation but that is not yet available to consumers without going through a pro tuner. I'm just wondering how this known issue will affect my attempts to dial in other things and if I should try tuning it out first or after the fact. Thanks for your input thus far, it's hugely appreciated!


Drinks beer!
Load compensations have worked better for me because the algorithm is well established and easy to implement. Impact to calculated load is negligible because it is compensating for a given condition and the resulting load value is correct for that condition. Furthermore the Load Comp tables are related to Manifold Pressure, which is directly related to both the injectors differential pressure and actual load requirements which is why those tables are there. This is evident with the stock implementation of the comp tables in that compensation is applied in the 2400 to 3000 rpm range. It is likely that the shift in range caused by the kit install is effected because the compensation in that region of the comp table is not ideal for the conditions now being observed. The per-cylinder injector compensation tables do not relate to manifold pressure and they don't compensate well enough for all conditions as the load comp tables do based on manifold pressure. The per-cylinder tables are meant for compensating flow anomalies and dynamic differences in cylinder configuration. These tables should be tuned via exhaust gas temperature only or use of a 4 channel wide band controller. For any configuration, other than stock block, heads and injectors, I will zero these tables out. Other wise I will leave these alone.

I would not worry so much about the resulting load value. Ultimately they are what they are as long as the car runs good and under all conditions. The load comp method works about 85% of the time for me and since you have the kit installed, it would likely eliminate the issue all together. I bet.

I have yet another spread sheet which I will post to that same link as before. It is designed specifically to tune the load comp tables and it does a very good job of it. Again I am here to help you make sense of it. This one is also from the RomRaider community. I will post later tonight when I gate home.

Thank you for this very engaging conversation!!! :tup:


New member
Hmm, I see your point about using the load comp tables because they are directly related to manifold pressure. I'll zero out all the current comps and give that a go as well. My hesitation around that was the amount of compensation needed to correct the issue. From what I can tell it can be as bad as +15-18%. Fwiw I zeroed out all load comp and ipw comp tables when installing this kit, assuming that it would be the magic bullet fix for all my fuel pressure issues. This is when I noticed the massive lean spot around 3200 and found Cobb compensating for it in the per injector pulse width tables tables.


New member
Just came across this tutorial which is a great example of tuning this out using the load compensation tables. Figured I would drop it here for anyone else having the same issue. I didn't think to look at the stock tables, it turns out Subaru goes as far as adding 20% there so my concern with adding 15-18% seems pretty invalid.
That is a good video. The only correction I would make to that is that any adjustments to this table is not an adjustment to % of fuel but an adjustment to % of load.

I uploaded the spreadsheet. It is much more precises than just randomly adding to the load comp table. The way I often do it is I leave the stock load comps as they are and then add the results of the spreadsheet to the existing load comp values. For some reason I always get better results if I log using the AccessPort and not AccessTuner Race. AccessTuner takes to much data. Take a log of about fifteen minutes of normal around town driving and and some highway cruise. Try to recreate the stumble if you can. Before you use the log, filter out all the open loop data first. Then run it through the spreadsheet.

This method will not only compensate for the stumble but it will vastly improve drivability over the entire MAF range. You will notice you fuel trims over all to stabilize and shifting and throttle response will improve.


New member
Right, that thought crossed my mind when he said it. Thanks for the tip. I'm definitely going to trying putting some good data in the spreadsheet this weekend.

So in the interest of understanding exactly how large numbers in the load compensation table work I'm going to attempt to explain it and let someone correct me if I'm wrong. For reference all these numbers are coming from Cobbs OTS stage 3 map for the 2016 STI.

Say you're cruising on the highway at 85. Load is roughly 1g/rev so the closed loop target is 14.5:1. Because of the fuel pressure issue we lean out to 16:1 but the closed loop corrections account for it by adding 10% more fuel. Even adding a 20% load compensation in this scenario will result it a calculated load of 1.2, which in the closed loop table results in the same 14.5 target. What am I missing here? The only way I see this helping is if the load comp is enough to trigger the switch to OL fueling where the target is something in the mid 12s. The other thing worth mentioning here is that assuming a 20% adjustment to the load compensation table will get us the desired 14.5:1 ratio, it will also result in a 7 degree drop in timing which can't be good for efficiency. Thoughts?
I'm not exactly sure how it does it but it has more of an effect on IPW than it does a shift in load cells on the fuel map. This is a MAP/Load component and not a MAF/Load one