IFR Value Limit Workaround - Parameters to scale?

[RWTD]

What all parameters would need to be scaled exactly? i.e. if we want to cut the IFR table in half, then we would need to obviously cut the MAF in half (if MAF is used), as well as the VE tables (if the VE calculators are not purposely disabled). Should there be any other parameters scaled like this, as well? Breakpoint? Engine Displacement?

I feel this is a much better method than attempting to rape the offset table. This is also the proper method that is used on Fords when we need to get around the MAF transfer limitation that is found on most of the newer EEC-V based systems.

Suggestions and thoughts are welcome.

Thanks!

James

[Redline MS]

What all parameters would need to be scaled exactly? i.e. if we want to cut the IFR table in half, then we would need to obviously cut the MAF in half (if MAF is used), as well as the VE tables (if the VE calculators are not purposely disabled). Should there be any other parameters scaled like this, as well? Breakpoint? Engine Displacement?

I feel this is a much better method than attempting to rape the offset table. This is also the proper method that is used on Fords when we need to get around the MAF transfer limitation that is found on most of the newer EEC-V based systems.

Suggestions and thoughts are welcome.

Thanks!

James

James,

I have been thinking about the same thing. We have done quite a few PC ZO6's and use 60# injectors. The Ford thought process should apply as I know where you are going with this. I am still not convinced on what the displacement parameter does if any. The breakpoints are also something that we typically don't have great access to for most injectors so where do we start??

I have a decent offset table which we developed by installing a set on a bone stock car and worked the table until we got trims in line. I also had to max the IFR table and did cut the MAF down. Seems to have worked fine this far.....until we have a better plan.

Since the Ford stuff has no VE table, its a bit easier to rely on the MAF exclusively for fueling.

Howard

[RWTD]

Howard, thanks for your reply. It's very helpful!

FYI, I have disabled VE completely on my '08 Z06. I'm relying solely on the MAF. I'm probably going to just cut the IFR table down, as well as the MAF transfer. It's the only logical way at this point.

I'm with you, I don't think the displacement scalar does much of anything on a GM, save for auto scaling the VE table (HPT added that in years ago), and potentially like Ford in giving the pcm a figure for part of the VE/Load calculations.

BTW, I just sent you a PM on here!

Very Sincerely,

James

[Bluecat]

Lots. Obviously like you said the VE and MAF tables need to scaled. But when those values change, so do a lot of calculated values that are used for table lookup. Basically any table that uses g/cly for an axis, especially the timing tables. Plus its screws up the estimated torque numbers so any automatic trans tables thats uses engine output (like the pressure tables) need to be fixed. I usually do it on a factor of .75 or .50 so that the numbers work well in my head. For example on a big turbo car I would use half numbers (.50) for the Injectors and air flows. That way in a log when it says 400g/sec, I really know the engine is doing double that. Or if its logs 0.80 g/cly I know its really 1.6g/cyl.

Becareful on the table adjustment, when its on a axis you can't just multiply the table by a percentage. You would have to copy the .48g/cly row to the .24 row, and the .80 to the .40, ect...

Sounds like a pain in the ass, but a lot of the results are desirable. For example on a .5 tune, instead of the timing tables ending at 1.2g/cly on a ls1 car, the table effectivly represents 2.4g/cly. Which gives you enough room to keep full control of the timing on a 20psi turbo car without just running in the last row past 12psi.

My rule of thumb for starting out on FI cars is 100% numbers on a <500rwph car. 0.75 for 750hp - .5 for 1000hp - ect...

[Redline MS]

Good points about watching other tables effects. You'll also notice when the MAF gets pegged that your timing table starts going backwards. If you track the timing through the rpm/load cells you'll see load rise and return back before redline.

In a FORD processor the first thing you do is get the MAF dialed in so load is reported properly for just that reason. You start playing with the MAF to get fueling in line and next thing you know is that your timing is all out of whack.

I wish we could get the LS3 MAF tables into the 06-07 PCM It goes to 15000 hrtz and over 1000 grams/cylinder! They are getting ready for the LS9 and some boost! Would be nice to get a MAF patch..........

Howard

[RWTD]

I appreciate all the help! I communicated with Greg Banish (Calibrated Success) on this, as well, and he reiterated most all that was stated in this thread, along with some very good other pointers (the man is a genius), some of which I'll bring up later in other posts. One thing I will mention now, that he said, and Howard and I brought up already within this thread, is that the Engine Displacement scalar will affect the the airflow calculation in SD mode since the VE "percent filling" always references the nominal engine/cylinder volume (this didn't matter in my case, as you will read about in just a moment).

Now on to my day:

I was able to dyno tune an A&A Corvette S/C kit equipped '07 Z06 today. I tuned the car in full MAF mode (disabled VE - remember what I just said in the previous paragraph about the Engine Displacement scalar), and it tuned out to perfection. I found *every* g/cyl reference, at least available to us in HPT, and scaled all the tables appropriately. I used a scale ratio of 0.80, due to the fact that this put me just barely inside the limit of the IFR with the 60# injectors (which flow approx. 73# at 58psi). I considered scaling by 0.50, since this would have made the copy/paste so much easier, but you also lose a ton of table resolution this way. Anyway, thanks to some quick work with Excel, I was able to easily interpolate and match all the values to the proper load points. As mentioned, there's a LOT of stuff that's referenced, such as idle parameters, spark, knock sensors, etc., so it did take a bit of time and work to make sure all the tables and their values were set correctly before I flashed the vehicle.

The MAF hit just over 11k Hz, and I was able to control all fueling through the MAF transfer. The nice thing is that since the MAF transfer was now scaled by 0.80, my new g/s limit was 640 (512/0.80), and I needed every bit of it - I was hitting right at the coded 512 limit when over 11k Hz, so it's basically done! The referenced g/cyl on the spark tables was around 1.2x range at peak boost, so I still had table to work with. On my Dynojet 224xLC, the car made 580+ rwhp, and I could have pushed it closer to 600, but I wanted it to stay in one piece for the customer for the current round of mods (bone stock with just the A&A kit). I had a max of 15 degrees in the car at peak boost (Howard, what are you running?), and this was on 93 octane.

I have an '08 Z06, and the stock knock sensors are stupid sensitive (even on the factory tune), and that held true on this '07 (a bit of false knock I had to deal and work with). I didn't really like the fact that it has the stock manifolds, so with some LTs the boost would drop from the current peak of 6 to around 4.5 to 5.0 (does this sound about right on the boost drop, Howard?), while freeing up about 20 to 30 horsepower. The weather was also a bit crappy today (warm and humid), tho it gets back nice again starting tomorrow (thankfully!).

I wish we could get the LS3 MAF tables into the 06-07 PCM It goes to 15000 hrtz and over 1000 grams/cylinder! They are getting ready for the LS9 and some boost! Would be nice to get a MAF patch..........

I wish it was in the '08 Z06 pcm, too! However, Howard, our wish is coming true very soon. Check it:

http://www.hptuners.com/forum/showthread.php?t=14800 <---click!

We've incorporated a number of powerful new features that brings the HP Tuners solution well ahead of any stock operating system solution. Here's a quick rundown on the features, some of which will be familiar to those that have used our enhancements before.

This E38 enhancement contains the following features:
- 2.5 bar (255 kPa) max MAP sensor support (calibration capability for GM 0-5V linear MAP sensors)
- Rescaled MAF High Freq table supports up to 15400 Hz with 300 Hz resolution, also supports airflow up to 1024 g/sec
- New VE tables with 33 x 33 cell resolution each and configurable MAP and RPM axes (choose your own resolution)
- Charge Temperature based VE multiplier table, configurable axis
- TPS based VE multiplier table, 33 x 17 cells with configurable TPS and RPM axes
- MAP referenced Boost Enrich table
- Boost Enrich MAP threshold and hysteresis value
- Both MAF and Speed Density mode supported
- Boost based fuel cut, selectable MAP threshold cuts fuel to all cylinders when exceeded
- Rescaled fan temperature axis 163-250F (73-121C), stock is 192-250F (89-121C)

The MAF High Freq table has been rescaled to 5800-15400Hz at 300 Hz resolution and the maximum airflow limit for this table has also been adjusted to allow up to 1024 g/sec (instead of the stock 512 g/sec). This is excellent news for boosted applications that want to retain the MAF but reach higher than the stock 12200Hz and 512 g/sec limits.

There's more than this, so be sure to click on the link above. Also, go down to my post #27, and you will see where I asked about the IFR limitation. Chris responded with a nice wink that he was looking into it (which means it's going to happen, hehe).

WOOT! No more scaling!

Regards,

James

[RWTD]

Oh, I meant to add:

As for using the 60# injectors, I copied over what I could from the values we use in Fords, and everything worked out pretty well. I'm going to add to my previous postings about it in a bit on this 60# thread:

http://www.hptuners.com/forum/showthread.php?t=14101 <---click!


Next up is my '08 Z06, which should be within a week or two. We're installing the *exact* same A&A kit, tho I'm going to put some LTs on mine with it. I also think I want to go to a return style fuel system, since this is the only method I know of that will allow me to have a referenced based regulator (correct?) for the GM mechanical system. This will also rectify the tuning issues with larger injectors, since running a referenced regulator will reduce actual fuel pressure (flow) under vacuum/idle, thus allowing for larger pulsewidths at idle (no longer riding the minimum pulsewidth), while keeping more headroom as boost increases.

I'm also considering the new SD 54# (at 58psi) LS2 injector, since they are the same height as the factory LS2 injector, and this will keep me from having to raise up my "purty" red engine covers (oh man, they look pretty fugly up high, due to the taller 60# injectors, lol). I believe that 54# should get me to around 625 to 650 before they are done, tho I don't know if I want to cut it that close. Hell, I could go with the shorty 60s instead. See here for more info on those 54s:

http://www.racetronix.com/M145FM2.html

Regards,

James

[MoFinWiley]

James,

I have been doing a ton of reading to try and learn how to tune my car, and I am now a few your links deep to get to this topic...

Is scaling the best answer for E40 and 60#ers?

It seems daunting, but if done correctly also seems like it will produce the most favoralbe results.

Car is TT GTO. I am going MAF(LPE 100mm I bought before I knew better), have a wideband.

I should be finally starting the car up for the first time on wednesday. I trying to get as much stuff dialed in so that I can check for leaks with all the new fuel/oil/cooloant lines running erverywhere.

I would like the car to at least idle before I move onto actually tuning it.

But if I am going the scale route it seems like there is a lot to change before I can get it to idle, and since I am learning as I go it will be having to scale tables I am not 100% familiar with.

I guess I am just looking for some reassurance that scaling can work...I AM willing to put in the time to make it work, just wondering if you have found anything recently that makes it a bad idea.

Thanks

[RWTD]

Scaling does and will work for you, and is the only real answer at this time! Just scale the necessary parameters, as I mentioned in my previous posts above (thanks to Greg Banish), and you will be fine.

[2006 z51 Vette]

i just got done reading Greg's book for the second time, and its great.
He mentions about scaling also to accomplish the tune..
but my question is to scale the injectors correctly (60#) would i take the true value for the IFR table and scale it down from there or do I scale it down by X% from the table max?

[eficalibrator]

...my question is to scale the injectors correctly (60#) would i take the true value for the IFR table and scale it down from there or do I scale it down by X% from the table max?

You should enter a new value that is X% of the ACTUAL flow rate of the injector, MAF, displacement, etc...

Glad you enjoyed the book.

[2006 z51 Vette]

Greg,
Thanks for the feedback
I have one more question, so how do I handle the timing tables then?
can someone post a example of what to do..
I scaled the entire tune by .80

[eficalibrator]

If you scaled everything by 0.80, you just need to do some cut/paste work on the spark table. Since load is displayed in g/cyl and you now "show" only 80% of the previous grams/sec flow, you need to shift everything down on tables that use g/cyl as the axis. In this case, you would make a copy (in excel, perhaps) of the existing timing map and paste the values back into HPT on a new row that is 80% (0.80 multiplier) of the original location. So the original 1.00 g/cyl values go into the 0.80g/cyl row, the 0.80 becomes the new 0.64 row, and so on...

The side benefit of this is that the range of loads covered by the spark table now gets even bigger, so you can theoretically run more boost before running out of room. However, this also means that you've lost some resolution, so be prepared to make some compromises down low. Just pay attention to the g/cyl (dynamic airflow) while datalogging so you can know exactly where the PCM got the base spark value from.

[Dyno Dan]

Hmm......I wonder if this is going to be a "wash" for me. My turbo TBSS used to have the stock MAF, and then I swapped it out for an LS7 MAF element packaged in a 3" tube. I used to see roughly 10,800 -11,200 hz with the stock MAF, and now I see as high as 11,900 hz on the same boost. When I swapped in the LS7 MAF element, I didn't copy in the LS7 MAF xfer function, I just kept the same values that I developed for the stock MAF. To my surprise, all I need to do was some light trim work, but other than that, I was good to go.

Now I'm trying to gain some "head room" with the LS7 MAF in a 3" tube, because even with low boost (7psi), I'm nearly pegging the MAF. According to my logs, my cylinder airmass seems to be artificially high at 1.28.

I may be shooting myself in the foot, but I'm going to try scaling down the MAF xfer, cylinder volume, IFR, and VE by 25% and leave all else stock. I know my g/cyl reference is going to be off on important tables, such as spark, but I believe that the g/cyl is not accurate to begin with since I'm blowing thru a 3" tube.

Am I way off here?

[eficalibrator]

Dan, if everything was correct before you swapped from the stock MAF to the LS7 slot element, the ONLY thing you should need to chage is the MAF transfer function.

Just force it into MAF-only mode by setting the max threshold for dynamic air to 400rpm and tune MAF curve like you would on a Ford. You will probably see that as you correct the g/s numbers in the curve at each Hz, your g/cyl fall right back in line with where they were before.

The problem you will run into is that this new element in the 3" tube has a transfer function that pegs earlier than your stock meter it seems. If you really want more range, you'll need to put the element in a larger tube and recalibrate the curve accordingly.

You don't need to do any scaling until you're hitting the 512g/s limit (just like the 1739kg/hr limit on a Ford).

[Dyno Dan]

Your statement holds true (as usual), and that makes sense now that I look at the logs. The higher g/cyl was from cooler weather, not from the fact that the MAF element was in a 3" tube. Once I got the xfer function nailed down, the g/cyl seemed to fall back into place. The only reason I'm using a 3" tube is for packaging / aesthetic reasons.

I did play around with the scaling, and everything worked as described above. Just as was mentioned, my Y axis (g/cyl) for the spark table moved down, so I need to correct the values at those lower g/cyl areas.

I'm attempting to deal with 2 different issues, the fact that I was approaching 512 g/s on the MAF, and the fact that my E40 ECM can't process ariflow above 12,200 hz. The only reason I'm scaling things down is in an attempt to have enough range on the MAF to describe airflow properly, and not hit 512 g/s. My "low boost" is set up for 7 psi, and high boost is 12 psi, so I want to be able to let the MAF to it's thing.........like a Ford......the way it should be

Sounds like it's time for a 3.5" tube.......or if HP would just scale the MAF out to 15,000 hz, that would help. It doesn't appear that you can renormalize the MAF xfer X and Y axis...uggh.

[redhardsupra]

you can try this: http://www.powrmax.com/PowrMAF%20100.html people seem to have good results with it

[5_Liter_Eater]

I'm gearing up for my Paxton install and this thread is particularly interesting to me. Scaling down the IFR and MAF get around the 63.5# and 512 g/s limits seems to be straightforward. Having to scale all the g/cyl tables is a little bit of a hassle but I can handle it.

Something else I wanted to address was spark in boost. At first I thought I needed to get a 2 bar MAP but what I just realized after going through this thread a second time was that the gen 4 spark tables are in g/cyl, not MAP, so the scaling should take care of that too!!! I may have to scale by as much as 50% to get the spark tables to read at or below 1.36 g/cyl at ~8 PSI of boost. I guess Just disable the DTC's for the pegged out MAP. I can't think of any tables that would be referencing the MAP.

The only downside is that the fuel and aifflow numbers are not real world. So my MPG's will not be correct on the vette's DIC, but the benefits are bountiful.

[BCM]

The newer FAST LS2 and LS7 injectors are real nice to work with. I am running the 50#ers and they dial in very nicely. They go up to 65#.

>http://www.compperformancegroupstore...ode=FUELINJECT

Howard and I looked at changing the OS in the E38 to the LS3 and discovered it was not easy or maybe even possible. That OS is set up for the LS9 and will play up to 15,000 hz and 1878 g/s. Stay tuned-

[Mobile Chassis Dyno]

Glad to see another ford tuner on here asking these same questions. I posted the same questions awhile back.

Do you need to scale the V/E if you are scaling both the maf and engine displacement in half? It seems to me the v/e would be correct because even though you tricking the pcm you are moving half the the amount of air. You are also telling it is feeding half of the cylinders.