I love to learn....please keep teaching :-)
I love to learn....please keep teaching :-)
Can we talk about those now.Originally Posted by Hemituna
Let me explain the above a little more.........
A stock 6.4L tune has the WOT airflow limit as 353 g/s.
But the TB table goes to 1100 g/s ??
So how does that work??
Now, if you log max airflow on a stock 6.4, the biggest number will be 350-360 g/s.
So 350 g/s makes 475hp it seems....So why is everyone using 1000 - 1500 g/s to make 100-300hp more???
The factory it seems has imbedded an airflow model in the PCM, hence why you must designate an engine capacity.
Now this model only affects P/T operation. Between the TB airflow and what they deem the engine requires at P/T,
the TB will track an airflow target. Now WOT is WOT and the TB will open 100% no matter what the numbers are in the tables.
But P/T between 25 - 75% throttle, you are limited to the numbers in the model. So if the 6.4 is in P/T mode it will never open the TB past 353 g/s whether at 30% pedal or 70%. Most never notice this. If you move WOT threshold lower, you notice it less. BUT, if you make the airflow tables bigger, the gap between P/T and WOT gets even greater.
If you make the numbers bigger, the TB will be opened less until it goes WOT.
If you try and increase the ETC tables, what often happens is the ETC opens the TB, the airflow exceeds what's allowed and the ETC is forced to close the TB. So you get this strange surging effect.
Why the factory has done this is to give the engine the amount of TB that they feel it needs at certain rpm to maintain velocity/airflow/smooth the torque curve or whatever!
However, when modding or adding a blower, this is now not ideal.
So following their lead with TB flow tables often wont get the result you are after.
On a blower engine, 50% pedal, wont give enough TB opening to make much boost so you don't get 50% power. so you keep leaning on the pedal till finally it goes WOT and BAM - full boost and look out! The often talked about light-switch effect! This same response is felt when NA also.
The trick I have found is to lower (a lot!) the 3 TB airflow tables in the .75 -1v and above areas.
This will give a much more linear pedal to the point where the transition to WOT is seamless.
The added benefit is that you no longer hit lots of Airflow/Tq mgmt limits!
Keep in mind the stock airflow max numbers and give it a try.
We can talk more about NOV and Wheel Power tables later.......
You mentioned 3 TB tables. Obviously one is the Throttle Body Airflow table, what are the other two? Is it the small/large range under Desired Throttle?
That's the 3 of them!
I've seen Sonic airflow mentioned in other threads and how other software has the ability to log it. What exactly is that and if we could log that what information would it provide?
Here is the part I don't seem to be getting with everything. Like Hemituna I have found matching the 3 TB tables does not net the results that it seems they should. The bigger thing that I've found though, when running a bigger cam, or anything that generally requires more airflow at idle or higher idle, seems to react best to increasing the airflow values in the Throttle Body Airflow table and only that table. The part I struggle with is in theory this should cause the throttle body to run less throttle position. It does just the opposite in practice, at least in every situation I've encountered. Can anyone explain this?
It is because the idle control is torque- based and not airflow.
You play with the airflow numbers to get the torque correct and then it will control the idle nice.
Actually the whole PCM is torque-based and you are just using airflow etc to get the correct torque numbers.
They idle/drive amazingly well when all is aligned.
Definelty agree, if the time is spent getting the tables figured out it seems like they work great. The problem I have seen is I guess a lack of info. Like was stated earlier in this thread there are things we cannot log. So this turns into an issue of not having the proper data to actually make adjustments that are data backed. Now, experience in making adjustments and knowing how the car will react can be helpful, but I'm one that likes to be able to back up or prove that those changes are doing what I think they are doing, not just hacking or masking an issue.
So this brings up my point or what I guess I would really like to dive into with all of this. NOV and Wheel power tables, TQ management tuning, REQ TQ adjustments, DES Airflow....all of these things are crazy important in tuning these cars and really most any newer car. So specifically with the HEMI's has anyone really figured out what to be logging or how to log all of the proper info to understand exactly what is going on during idle and part throttle to be able to properly setup these areas? I know for me, at this point it is still a bit of an educated guessing game, and personally I hate doing it that way.
For example on a car I have been tuning recently, it shows a commanded tq of 0 until the car is in gear, and without looking back at the logs, possibly until it is actually moving. So that being the case, and this being a tq based idle system, it is not really possible to use that info for making adjustments. At least not any way I can figure. Then when you get into airflow it is, like stated earlier, sonic airflow, which is not able to be logged, so the data we have is basically not valid for making calculated adjustments. At this point it is more we raise and lower until desired and actual airflow values come inline. That is not a big deal, but a much better way would be to know exactly how much movement we need in our tables based on data in the logs. Percentages may be able to be used in some sitations, but I feel like there are too many calculations going on in the background for that to actually work everytime.
Last edited by mxatunerjg; 07-08-2017 at 07:35 AM.
You do realise that these numbers (airflow/tq) are manufactured right??
Its just a way of quantifying things so things can be made to work together.
The original calibration probably would be close to correct however when you make changes to the engine that all goes out the window.
You just have to play with the numbers till everything is happy.....
It can all work sweetly whether you have 500hp or 1000hp, the PCM is none the wiser.
Realize, yes, though I want there to be a better way to tune these idle and part throttle areas for a smooth transition. Everything around the throttle movements is all an educated guess, and to me that just seems like a bad way of doing things. It's not really accurate, and it is horribly inefficient. I just keep researching hoping to find a better way, until then I'll keep doing the same thing you have done, make adjustments, drive, and repeat until I'm happy with the results.
If you cut, say...20% out of everything above .5 volts in the Throttle Body Airflow table like you're saying, do you need to rescale the Desired Throttle (Large/Small) to match the new values? In my factory tune, the values in the Large/Small Desired Throttle tables are the inverse of the Throttle Body Airflow table.
Good info, BTW! Keep it coming... I'm fighting the setup in my signature (the 392 stroker), trying to get it perfect.
2004 Dodge Durango, 5.7L Hemi, 10:1 compression
-SRT8 cam, advanced 6 degrees, 6.1L valve springs
-Manley pushrods
-Scat rods, Speed Pro pistons
2004 Dodge Durango, 392 Stroker, 11:1 compression
-Custom cam grind, 221/230, .575"/.585", 115 LSA, 3 degrees advanced)
-Scat forged 4.05" crank, Scat Ultra Q-Lite H-beams, Mahle forged pistons
-Stock heads with 6.1L valves (2.08", 1.60"), bowl work to match new seat profiles
-PSI LS1511 valve springs
Dam this is great info.
Thanks to all involved!
Now, does anyone have an opinion on how to tweak these numbers for a dual Hellcat TB, progressive linkage setup?
That's what I have on a 6-71 above my 398 6.1 based Hemi.
The second TB is manually operated off of a progressive linkage and the primary is DBW.
The secondary starts opening at about 18% of the primary and is linear to 100%
I'd love to hear some thoughts on this.
IMG_9345.jpg
BAD AZZ!!! I love it! I'd sure love to play with that tune too! I'm betting it'll be fairly easy to dial in. It took a boatload of tunes to get mine right however it was done way back when the tuning was still a big guessing game for Mopar and more "hackware" than anything with DS. With the hat like I have its more like a BIG throttle body so it took some work to get it happy. Only having a little over 8" of vacuum at idle made it exponentially harder. My best friend begged me to go with the Mad Max theme like you have but I liked the bird catcher look better. It's really cool to see someone do it. Started with a BDS 6-71 and then upgraded to a Whipple 8.3 liter.
Are you tuning it yourself? I made a quick video of my setup and you can see how we just used the throttle body to work a bell crank for the hat. Sorry my video skills are lacking to say the least but it wasn't made for the public just figured I'd share https://youtu.be/h8TuZncJH-8
That's one of the builds that inspired me to go ahead with the 6-71 build. Southern Hot Rods I believe.
Thanks for paving the way. I really wanted to make sure to have an air filter though since it was to be my daily driver for a while.
I'll be doing the tuning soon, but Johan (Diablotoona) has done tunes for me for a few years. The TB setup was always a trick.
I first used an electric control by Ozmo Engineering that would mimic the primary TB with the secondary.
The huge rush of air off idle really caused some problems. Changing to this progressive really smoothed everything out as far as drivability.
I'm really curious as to the TB control settings in HPT and if they have "progressive" control built into them, if I'm doubling that up by having my mechanical setup being progressive as well.
More trial & error I suppose.
The trial and error is the fun part lol. Yes Southern Hotrod was instrumental in making it happen. We did it when they said it "couldn't be done" which was very motivating. Makes me happy to have inspired someone and glad to see you pick the torch up and carry it even further.
I've had lots of compliments and criticisms and its definitely a love it or hate it type thing. I've enjoyed every minute of the build and have no regrets other than not using it as a marketing tool because it always got serious attention just because it was different. If you ever need anything just hit me up. And please keep us posted on the progress :-) It'd be really cool to have them together in a photo shoot ;-)
yall arent referring to the shop in kenner are yall?
That would be the one.
Southern Hotrod LLC
Oh no let the bashing begin! lol
I have experimented with these airflow tables alot today in hopes of not having to modify the throttle tables and I cannot find a good solution(car is 2009 challenger with vortech and cam). There seems to be something that is unable to be changed to tuning in the HP software, something in the background possibly.
the desired airflow table did help a laggy throttle feel, but i wish there was some better explanation out there as to why and how it truly works. at the moment what ive read here and have tried is merely just throwing darts at it.
The second thing I have experienced is that even when all torque ESP management (fso, etc, spark) reduction methods are shut off the vehicle can still show signs of the the ignition being retarded and the throttles not being allowed to open, i am curious if there's other strategies that we can't have access to that are there.
its a pity because you can see signs of the car wanting to accelerate and take off like any 600hp car. but its all muddied up by the ecu. feels like mush, when it should be crisp and snappy.
screen shots of the throttle blade being held back. (yes i experimented massively with the voltage threshold hold for WOT pedal) it does nothing but move the stair step ledge to a different spot.
Last edited by Fox95; 11-25-2017 at 10:33 PM.
Roadracing Crew Chief - World Superbike, British Superbike, Moto America.
Airflow is secondary....only used to make the tq calcs because that is what you do when you step on the gas ...you make a tq request..
The pedal tables, and the flywheel table are using the airflow tables to give you x TB opening to make x tq.
If all that exceeds a tq or airflow number, the PCM will limit tq with TB opening and sometimes timing.
Those limiting numbers at P/T are low....really low factory numbers! They only allow the (quite large) TB to open as much as the stock engine needs.
We need to fudge the numbers so we get more TB opening for same airflow/tq numbers to stay under all the limits that we can't see yet (ever?)
So use very small airflow numbers above idle. If you find throttle is being limited at PT, reduce airflows by 20%, if that doesn't fix it try another 20.
I now make my desired airflow and TB max's about the same as the original airflow limits... way, way small, like 350g/s on the 6.4's
Once you are getting closer, you can then play with flywheel power to dial it all in at various rpm.
You can get em responsive and predictable just like a cable when done right, but only if you work with the system and try not to fight it.
Last edited by Hemituna; 11-27-2017 at 09:29 PM.
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