new hemi mpg in an Abody?
- Thread starter SirDan
- Start date
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Not to hijack this thread but, I would absolutely go with the new hemi swap. The milage would be there, and much more efficient tool
Nice b5 Challenger by the way.........
Great thread.
I have a '05 5.7L in my garage that will go into my '67 dart. I'll be running a 3.73 rear end, ~27" tire, tko 5 speed ( 1-5 gears are 3.27,1.98,1.34,1.00,0.68 ). I wonder how this compares to my 4300lb. '05 Magnum RT with a 2.82 rear end and 28.5" tire? I average 16.5-18 mpg around the suburbs with it. Freeway trips at 75-80 mph are 22-23 mpg.
I have a '05 5.7L in my garage that will go into my '67 dart. I'll be running a 3.73 rear end, ~27" tire, tko 5 speed ( 1-5 gears are 3.27,1.98,1.34,1.00,0.68 ). I wonder how this compares to my 4300lb. '05 Magnum RT with a 2.82 rear end and 28.5" tire? I average 16.5-18 mpg around the suburbs with it. Freeway trips at 75-80 mph are 22-23 mpg.
2367 RPM at 75 in the 67 dart with what you posted.
If I use the same trans ratio of .68-1 The Magnum rt should be turning
1696 RPM
With the lighter car it should be more MPG but the rpm is higher so I don't know? The dart is set up to be a more performance oriented driver. Should still get great fuel mileage but will be alot more fun to drive than the magnum.:toothy10:
72goldduster
Mopar Kid
Mom got high 20's mpg wise. i think she said cruising at around 70 in 6th gear, around 1500 rpms in the challenger.
just for reference, it's an srt-8.
do i have a cool mom or what?8)
just for reference, it's an srt-8.
do i have a cool mom or what?8)
TxSwimDad
Well-Known Member
Dead on w/ my 05 Mag RT's mpg.
392STI (A.K.A. 392Stu) is doing a stroked 6.1 w/ MDS in his 68 cuda that is backed up by the viper 6 spd and I don't recall the rear gears.
On paper we think we can get the MDS to function and if so, he may see upper 20's to 30 mpg. We are anxious to get it going and test the theory of the MDS controls we have in mind.
Even w/o the MDS I think it is only a matter of gearing to get these 3200 lb cars to get better mpg than my 4400lb Magnum.
I figure the 1200lb diet will get an A-body into the low 12's if it hooks up.
I agree, an LX with a decently modded 5.7 can get 25 MPG highway. I've seen similar numbers on 6.1 baised strokers that were settup with MDS. With an A body being over 1000 lbs lighter I think 30 is in range if you build for it. It's really amatter of having a good overdrive ratio and then hooking up MDS in the old school car to get the extra 3-4 MPG thats needed. I think you could do this two ways. First use a factory computer/wiring harness in the install and tune it with CMR and a diablo predator. Second, just run the MDS on a manual arm switch and then use a window switch and pedal operted switch to kick it off if the throttle position exceeds a certain point or the RPM drops below a given level. Far as I can tell you can take the cylinders that are governed by mds and hook the injectors, coils and MDS solenoids up to a relay so it all under manual control with the window and pedal switches making sure you don't forget to disarm and stall it when stopping or try to show off in 4cyl mode. Plus it could be set to hold 4 cyl mode longer which would work with the lighter car so you would probably get more mileage improvement from it this way than the 3 mpg the factory cars are seeing with it.
I've also seen 1-2 MPG improvement with decent ported cylinder heads but usually thats offset with a bigger cam.
My personnel goal for a long time has been to get 30 mpg and 10's quarter miles from my 67 cuda with a 3rd gen hemi. I know it can be done just for me it's a matter of getting the time to finish it.
Trojmn
Well-Known Member
Want better mileage? play with the fuel trim. Specifically lean cruise. You almost never need or want 14.7:1 AFR.
Adjust the fuel trims for part throttle cruise to be closer to 16-16.5:1 AFR. Leave full rich enabled for WOT. You wont notice the difference between 14:7 and high 15's in closed loop. 16.8 is the max for my 2.0 breeze commuter car which i adjust via wideband programed output to skew the entire fuel map... also works well just not as slick.
That is my Stratus/breeze in the following thread.
http://www.srtforums.com/forums/f87/lean-cruise-mpg-testing-lc-1-a-440796/
5.7 w/MDS waiting to go in the cuda....
Adjust the fuel trims for part throttle cruise to be closer to 16-16.5:1 AFR. Leave full rich enabled for WOT. You wont notice the difference between 14:7 and high 15's in closed loop. 16.8 is the max for my 2.0 breeze commuter car which i adjust via wideband programed output to skew the entire fuel map... also works well just not as slick.
That is my Stratus/breeze in the following thread.
http://www.srtforums.com/forums/f87/lean-cruise-mpg-testing-lc-1-a-440796/
5.7 w/MDS waiting to go in the cuda....
In CMR on the Hemi PCM's I've seen it won't let you adjust the closed loop target AFR. If you closed loop it's going to give you 14.7 unless the fuel trims are soo far off it can't. Might be able to make something to fool the linear o2 sensors into thinking it's sub stoic so it will make it lean though. You'd probably want to hook it up to a vacuume switch so you don't get high 15 afr's at near WOT but still closed loop situations.
Trojmn
Well-Known Member
I didnt get into this thinking that most HEMI conversions have a programmable computer which generally allows you to adjust fuel/spark tables to whatever at will... BUT assuming that you cannot do it the nice way, here is what i do on my Breeze and the wife's Town & Country...
Wide band o2 sensors use a completely different technology and output V range. Because of this they "simulate" a narrow-band sensor via electronic controller...which is programmable, has several outputs (run gauge etc), will data log! via serial port, and will actually work at very rich and very lean conditions. So the point is to shift the entire AFR readings and tell the computer that you are running richer than you actually are. i.e. a sensor detected 16.7:1 AFR will output to your PCM 14.7. 15=14 etc...
WOT is open loop, and your narrow band O2 dont work for crap at full rich power AFRs anyways. So max WOT HP is not affected.
Downsides?
slightly less HP at part throttle? if you go to far some drivablity issues. On my 2.0 anything past 16.8 runs like crap and will barely idle in hot weather. Anything <16:1 on both the breeze and caravan and you really cant tell the difference except at the gas pump.
If your down stream (after CAT ) O2 sensor doesn't throw a code when cruising your still burning gas in your CAT and not in the engine where it belongs. You;ll get a code because the computer doesn't detect an AFR difference before and after the CAT e.g. it thinks the CAT is not working.
So 60K+ miles latter, no problems, and verified 3-6 MPG improvement on my 2.0 4speed automatic. I went from 32-33MPG to 36-39MPG and a few better than 40. YMMV! going from 33-36MPG is a lot less gas saved than going from 17 to 19MPG.
I use innovate motorsport's LC1.
BTW you'llneed two for your Hemi ;-)
-Troj
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