Quote:
Originally Posted by cadillackid
the gauge I suggest only because we are entering unknowns.. even if bill pre-tests all his tunes ahead of time.. we will be the beta testers.. the ones to report back to him on driveability, engine heat, any HPOP defiiciencies or injectors that falter.. all different weights and gear combos and tire sizes and transmissions.. ultimately wit ha diesel engine its pretty easy.. if you give it more fuel its gonna try to burn it.. burning more fuel makes more power.. if your turbo spools up then you get more air so you get more complete combustion.. ie even more power.. fuel burning in cylinders makes heat.. higher RPMs light throttle load, highly spooled turbos you get less heat.. over zealous allison transmissions that like to shift into 6th gear before you have a chance to say boo can result in lugging which results in very high cylinder temps. you want to know this..
I installed my gauge after I tranny swapped.. because i knew that after my trans swap my bus was a one-off there enver was a year 00 running an 04 ECM with a 6 speed allison 1000 running on 3.54 gears with 19.5" tires built.. ever... theres no way the factory couldve tested my combo like they do every other combo that they sell.. now we are going to go into the realm of custom.. curves designed on experience / dyno tests with similar engines / trial and error, and prior knowledge.. our busses are going to be those test units to see if something does in fact go out of bounds.. does running a 300 Horsepower tune with stock AD split shot injectors run the HPOP dry and cause a stall? will the stock allison shift schedule play nice and not cause lugs or high EGTs? how will your MPGs be affected? will you set codes? will the allison set codes (if electronic trans).
theres all kinds of feedback to give them and all kinds of good info to learn.. fortunately for those with T444E, the ford guys have hased out a lot of this on the 7.3 up through the vans and Medium duty F-series (450/550) over the years.. for the DT466E its largely alot of going on how similar engines act.. these guys have been tuning for along time so its not just shots in the dark here.. but for me being able to see how the fuel is burning in the engine is important..
I have a 444E.. it makes me want to go buy a 466E unit just to play with his stuff!
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Just so y'all know, I have talk to cadillackid quite a bit already. He is definitely a sharp cat and I really look forward to his input on our hardware and software.
Now, on with the fun stuff!
The first thing to keep in mind about the application we've developed is that it is not a matter of simply changing the EFRC to the 190/195, 210/215, or 230 HP settings. This application will completely rewrite the calibration in the ECM with tuning we've developed from 24 years of tuning Power Strokes and Navistars. From that point, we can still utilize the EFRC so that the end user can further control the power level that they need for their particular application. This is all easily handled through the software with a simple parameter change, so a power level change takes only a couple seconds.
With the Navistar applications, particularly in heavier base platforms such as a school bus, the major concerns with increased performance would be transmission life and exhaust temps. Here's how this breaks down and why modifying the tuning is so important.
The factory tuning is conservative, to say the least. Much like the Ford tuning (and it's clear that Navistar worked hand in hand with Ford in regards to tuning development from the number of documents I've acquired over the years), there are several gains that can be made just by increasing the efficiency of the combustion process. Minor timing modifications, changes in injection pressure, and restructured fuel curves can all help to not only improve performance, but also increase efficiency and drivability. This is where the modified tuning really shines.
In regards to EGTs, very minor changes to the timing curves can help to control exhaust temps under load. By starting the combustion process a little earlier in the cycle, more of the heat energy is converted into pressure on the piston and less of the hear is wasted as exhaust. This keeps EGTs down while helping both performance and efficiency, and this is even without adding any fuel. 5%-10% gains in power output, 3%-5% gains in fuel economy, and up to 200 Deg. drop in exhaust temps. (pre turbo) can be achieved with only a modest change in the timing curves.
Of course, since we've managed to drop the exhaust temps., we can now look at way to improve power output. Modest changes in injection pressure are the second thing we can look at to not only improve power output, but also efficiency. A 200 PSI change in Injection Control Pressure (ICP) to about a 1500 PSI change at the injector nozzle on the T444e and about 1100 PSI on the DT466. The change in pressure does three things; (1) It slightly advances the timing, (2) it better atomizes the fuel charge, and (3) it slightly increases the fuel volume being delivered. This, again, causes a modest increase in performance and economy without a significant increase in exhaust temps. The gains in temperature drop we achieved with timing adjustments will still be pretty stable.
At this point, with no appreciable increase in fuel volume, we've usually picked up about 20 HP, about 0.8 - 1.0 MPG, and dropped our fully loaded EGTs about 200 Deg. Most people would be pretty happy with this and I wouldn't blame them. However, there is more than can be had out of these engines while still managing EGTs.
Staged changes in the injection pulsewidth tables are where we can see more noticeable power output changes... The kind of changes you can really FEEL. Quicker acceleration and better hill pulling capability are immediately apparent. Of course, with added fuel comes added heat. The more fuel you introduce into the cylinder, the longer it takes to burn and will again come out as heat in the exhaust. We can modify the timing table a little more, but there are limits to that before you start causing other problems with the injection event spraying outside the piston bowl. At this point, it really comes down to being able to monitor the exhaust temps. and understanding when to back off the throttle or when to downshift to keep the RPMs and airflow up, both of which will help to reduce the EGTs.
There are physical modifications to the turbo that can be done to help improve airflow into the engine, which helps reduce EGTs and allows for higher power outputs. These can be accommodated for with tuning as well but is not something most folks on a budget would be interested in, especially if the turbo is working just fine as it is.
Ultimately, our goal is to make the tuning as safe, as reliable, and as efficient as possible without the need for external modifications.
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Moving on, we will take a look at the transmission. In these applications, particularly the earlier applications, the concern is the torque limitations of the transmission. The Allison transmissions are good transmissions, but when looking at the potential of making 150 Ft./Lbs. of torque over stock, there's not a lot of wiggle room.
Power handling of the AT 545 is rated at 235 HP, but only a measly 445 Ft./Lbs. which is barely enough to handle the output of the engine's peak torque output. This is where things get a little tricky, though. Peak torque generally occurs at about 1600 RPM, according to Navistar's documentation.
Code:
Engine Speed RPM 700 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800
Torque Output Ft/Lb 300 345 403 434 442 456 427 407 376 366 366 319
What this means is that as long as we don't significantly increase the power output of the engine at 1600 RPM or below, we can add power without stepping outside of the boundaries of the tranmission's operating capabilities.
Now, keep in mind that this is power at FULL THROTTLE only. Since the tuning incorporates changes throughout the RPM and Load ranges, there are significant gains to be had in regions that aren't anywhere near the maximum capabilities of the transmission. I'd be happy to discuss these in more detail in another post, if there is interest.
Moving on the the MT 643, the torque limits of this transmission are almost 200 Ft./Lbs. higher than that of the AT 545. You'll find that there is considerably more room for improvements before approaching the maximum torque capabilities of the transmission, so the gains we are capable of achieving aren't at any real risk of overpowering the transmission. Unfortunately, Navistar bus applications run many of the AT 545 transmissions. Swapping to the MT 643, while possible, is not feasible for many skoolies on a budget. The differences involved in swapping between SAE 3 and SAE 2 bellhousings make it a daunting project to say the least. However, there are sever good threads regarding this swap, should you want to go digging.
Many of the later versions run an Allison 1000 or 2000 series transmission, rated at 620 Ft./Lbs. Again, not the greatest as far as capacity, but still should be more than enough to handle the proposed torque output generated by the modified tuning.
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Given the injector limitations in the majority of the applications we're likely to encounter, the realistic power gains we achieve are usually in the 65-80 HP range at 2200-2700 RPM, and 90-125 Ft./Lbs. in the 1900-2400 RPM range. This is good for moderate cruising and highway driving, but still provides plenty of get-up-and-go for low speed stop-and-go type driving.
We've been offering this type of tuning on the 1994-1997 T444e and DT466 applications for almost 20 years, and we've got this stuff pretty well nailed down as far as what these engines can handle. It's more along the lines of working with the CEC Single-Box setups, making sure the reflash stuff has no quirks and is reliable, and that the user interface is intuitive and easy to understand.
I hope this helps to answer some questions, and will most likely raise some more questions... which is great. It's much easier to deal with well-informed folks.
Take care.
Linear Mode
