sweet spot for optimal fuel mileage of a 606.962
sweet spot for optimal fuel mileage of a 606.962
50harleyrider
01-14-2021, 02:54 PM #1Where is your optimal sweet spot? Most diesels have one that gives them the best fuel mileage. I have found my conversion in my 1997 F150 with an overdrive E4OD tranny, 350 gears and 31" tires seems to do best at 2000 RPM pulling my 5500 truck at 70 mph. The engine and cab harmonics are smoother in the 2400 RPM range though. Being a 4 valve overhead cam free breathing engine, makes sense it could perform best in the higher RPM range especially having only 3 liters pulling that much weight. I plan to do some tests on the same flat terrain and report them and hope others have or will.
don't have any real back to back data for my setup (606.962, 31s, 3.9s, turning 2575rpm to go 70mph), but I have noticed highway fuel economy is typically worse than in town (where i'm normally ~2000rpm, which leads me to believe the stock turbo setup I've got is likely giving me some higher egps and hurting my efficiency.
gtd2060vz currently being fabbed together so we'll see if that makes an improvement.
X Double Dot
01-16-2021, 11:31 AM #3Efficiency wise it's likely that the lowest rpm that gets you the torque you need to maintain the speed you want will yield the best fuel economy. Engine setups (turbo match included) are almost always "most efficient" where you make peak torque, however spinning an engine at ~3500rpm when you only need 2000 rpm to get the speed you want will yield worse economy (hence one of the reasons why most new cars offer crazy high OD ratios to keep highway rpm to a minimum).
don't have any real back to back data for my setup (606.962, 31s, 3.9s, turning 2575rpm to go 70mph), but I have noticed highway fuel economy is typically worse than in town (where i'm normally ~2000rpm, which leads me to believe the stock turbo setup I've got is likely giving me some higher egps and hurting my efficiency.
gtd2060vz currently being fabbed together so we'll see if that makes an improvement.
50harleyrider
01-16-2021, 07:30 PM #4Both sound high to me although like I said, this is a high revving engine design which I suspect targets performance over economy. MB has never pushed economy as a marketing tool either. I haven't attained my target 20 mpg highway so it's time to do some tests. I'm getting about 15 combined which is a bit disappointing.
You mention having a "stock turbo setup". Is it really stock? Is the ECU running the wastegate? I instrumented the control line for the wastegate and found that most of the time the ECU is wide open on the freeway. Just a hint of extra demand from the accelerator and it gets slammed shut. As a result there is not that much EGP under normal driving conditions. If you are instead holding the wastegate closed until boost hits some limit, that will definitely hurt your freeway efficiency.
@ X Double Dot
You mention having a "stock turbo setup". Is it really stock? Is the ECU running the wastegate? I instrumented the control line for the wastegate and found that most of the time the ECU is wide open on the freeway. Just a hint of extra demand from the accelerator and it gets slammed shut. As a result there is not that much EGP under normal driving conditions. If you are instead holding the wastegate closed until boost hits some limit, that will definitely hurt your freeway efficiency.
(01-17-2021, 02:01 AM)AlanMcR @ X Double DotHey Alan, good point, so it's the factory turbo but a DSL1 controlled (non oem) wastegate actuator setup. I can run as low as 7psi on the highway, which is certainly better than the 11 it would run before when the wastegate was shut (higher spring setting), but i suspect the wastegate is still only cracked and the egps might not have been ideal.
You mention having a "stock turbo setup". Is it really stock? Is the ECU running the wastegate? I instrumented the control line for the wastegate and found that most of the time the ECU is wide open on the freeway. Just a hint of extra demand from the accelerator and it gets slammed shut. As a result there is not that much EGP under normal driving conditions. If you are instead holding the wastegate closed until boost hits some limit, that will definitely hurt your freeway efficiency.
X Double Dot
01-17-2021, 09:00 AM #6(01-17-2021, 02:01 AM)AlanMcR @ X Double DotHey Alan, good point, so it's the factory turbo but a DSL1 controlled (non oem) wastegate actuator setup. I can run as low as 7psi on the highway, which is certainly better than the 11 it would run before when the wastegate was shut (higher spring setting), but i suspect the wastegate is still only cracked and the egps might not have been ideal.
You mention having a "stock turbo setup". Is it really stock? Is the ECU running the wastegate? I instrumented the control line for the wastegate and found that most of the time the ECU is wide open on the freeway. Just a hint of extra demand from the accelerator and it gets slammed shut. As a result there is not that much EGP under normal driving conditions. If you are instead holding the wastegate closed until boost hits some limit, that will definitely hurt your freeway efficiency.
As far as cruising boost pressure, I think 7 PSI is still more than enough. Especially if you have an intercooler. I doubt you need ANY boost to have enough air to burn the required fuel. It would be nice to have an exhaust pressure sensor, so you could dial in the best intake/exhaust pressure ratio. 7PSI boost would be great if exhaust pressure is less than 7psi.
2000rpm is on the low side for cruising RPM. I haven't been able to find BSFC and BMEP graphs for the 606, but even the 617 has peak efficiency around 2250. Though actual driving peak efficiency is usually somewhere between peak torque and peak HP. The better flowing cylinder head on the 606 probably shifts that peak efficiency up a few RPM. If 2400rpm runs smoother, then I'd go with that.
As far as cruising boost pressure, I think 7 PSI is still more than enough. Especially if you have an intercooler. I doubt you need ANY boost to have enough air to burn the required fuel. It would be nice to have an exhaust pressure sensor, so you could dial in the best intake/exhaust pressure ratio. 7PSI boost would be great if exhaust pressure is less than 7psi.
50harleyrider
01-20-2021, 11:40 AM #8I really need to do some tests. I run around 5-10 psi cruising boost but am running a garrett gta 2359 vnt turbo so I'm not "wastegatefully" dumping boost into the exdhaust like wg turbos do. The oe kkk was so anemic. I love low rpm takeoff boost although I went with a high stall Ford V10 TC. 2000 rpm at 70 seems like a nice sweet spot for my setup but I will change it if I need to. My 2015 tdi likes the same 1800-2000 and it's a CR 4 cylinder.
In my 605 economy comes driving @2K no matter the load on the engine, load u can see by boost increase consequently EGP and EGT's.
Modern vehicles all have EGR systems. Thats is why manny decrease boost, actually they do not need it as they are ingesting exaust under pressure... MB 611 series uses 60% when ECU detect cruise conditions.
But again this engines also run on around 2K for best BSFC.
Its a question of fuel injected over time. At least thats how i understand them.
FD,
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Not my topic but.... if u happen to log or watch EGP u soon find out that it setles by itself when u cruise at or close to BSFC.
In my 605 economy comes driving @2K no matter the load on the engine, load u can see by boost increase consequently EGP and EGT's.
Modern vehicles all have EGR systems. Thats is why manny decrease boost, actually they do not need it as they are ingesting exaust under pressure... MB 611 series uses 60% when ECU detect cruise conditions.
But again this engines also run on around 2K for best BSFC.
Its a question of fuel injected over time. At least thats how i understand them.
FD,
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This old style trans eat lot of power to run the oil pump, and the converters slip a lot wich results in power eating ...
FD,
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For those with auto trans without lock up... its advisable to swap to manuals or modern controled autos with lock up.
This old style trans eat lot of power to run the oil pump, and the converters slip a lot wich results in power eating ...
FD,
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50harleyrider
01-21-2021, 12:52 PM #13Looks like you agree with my 2000 RPM sweet spot, Barrote. Fortunately the E4OD ford tranny does feature lockup as well as .7 ratio overdrive 4th. it was innovative way back in 1997. It's basically a C6 so a tough tranny. It would be nice to have a couple more speeds like 6.
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