nm9stheham
Well-Known Member
Hard to say.... Think of every 4 and 6 cylinder high fuel mileage engine out there, and the intake hanging out in the breeze.
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Smallblock efficiency or How to have your cake and eat it too
- Thread starter RAMM
- Start date
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MopaR&D
Nerd Member
I have my speedo pretty dialed in, it's a cable-drive AutoMeter and I confirmed the speedo drive gear was correct with a GPS speedo app on my phone, mayybe 1-2 mph difference at 75 MPH if that. First MPG check I've been getting 11 while tuning in the carb and driving like a maniac (gotta get those secondaries tuned!), all in-town miles. I agree though too many variables to NOT take MPG claims with a grain of salt.
Also for the fuel not only does alcohol (E-85) contain less heat energy per volume but the stoichiometric AFR is richer than gasoline so you have to use more just to keep the engine "happy."
I agree, I ran one for a while and unless it was about 50*F or warmer outside the manifold would get really cold from the air/fuel flowing through it, obviously that doesn't help fuel vaporization which is critical for part-throttle efficiency. It was easy to ice-up my carb in cold winter temps which was scary when going down the freeway at 75 MPH... My current engine has a non-Air-Gap RPM intake (no exhaust crossover though with the Eddy heads) and the manifold temps are much more stable which shows up as more steady AFR readings from my wideband. IIRC I also read in a couple places that warmer intake manifolds provide better part-throttle efficiency (with a carburetor) because the elevated temp increases the pressure inside the manifold slightly which reduces pumping losses and requires less throttle opening for a given engine speed/load. Manifold heat also improves fuel distribution. Basically you want some heat but nowhere near what an exhaust crossover provides, that's just overkill and was really only needed for cast-iron intakes which take forever to heat up. Without it Mr. Joe Average would have had to sit in his driveway idling for 10+ minutes before being able to head to work on a cold morning in his stock Mopar.
Things change completely with EFI though, the colder the manifold the better when you have an injector for each cylinder that pre-atomizes the fuel @nm9stheham that's why all modern engines have huge long plastic intakes that 'hang in the breeze'.
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mderoy340
Well-Known Member
Airgap is for warm climates or race cars. Open air cleaner under a flat hood is the worst thing you can run. Sealed hood scoop or cold air intake is your friend.
RAMM
Well-Known Member
I'm sorry guys for not following up. I am not nor ever been a hit and run poster.
There have been some incredibly astute comments-especially concerning cam timing and AFR.
Vacuum advance is VERY important and more than one poster has mentioned an AFR gauge.
I bought my first Innovate LM1 around 2005? I could not believe how wrong I was on everything carb related. Once I J.Roblearned to interpret the LM1 AND listen to then engine--WOW--big strides were made. A quality AFR gauge is MANDATORY in the quest for efficiency AND power. The real trick is interpreting what the data tells you. J.Rob
There have been some incredibly astute comments-especially concerning cam timing and AFR.
Vacuum advance is VERY important and more than one poster has mentioned an AFR gauge.
I bought my first Innovate LM1 around 2005? I could not believe how wrong I was on everything carb related. Once I J.Roblearned to interpret the LM1 AND listen to then engine--WOW--big strides were made. A quality AFR gauge is MANDATORY in the quest for efficiency AND power. The real trick is interpreting what the data tells you. J.Rob
That innovative LM dual exhaust set up is on my hit list.
RAMM
Well-Known Member
Never did I say 18-20 mpg in a smallBLOCK OF ANY KIND WAS OUT OF THE QUESTION. I said 500hp in old LA architecture along with---20mpg was not that straightforward.
I'm sorry the world has changed so much that you don't need 500hp---I do. J.Rob
RAMM
Well-Known Member
It is truly a game changer. J.Rob
ir3333
Well-Known Member
I have been using the Inovate MXT-L for a number of years now and transfer it to each new project.
Idle tuning is difficult with larger cams
But cruise and wot are very easy to get spot on...and cruise is your mileage miser.
Idle tuning is difficult with larger cams
But cruise and wot are very easy to get spot on...and cruise is your mileage miser.
MopaR&D
Nerd Member
AFR gauge is a game changer, I'd argue a vacuum gauge is as well, really helps dial in the part-throttle stuff. It's also a good monitor for overall engine health and tuning changes and helps save gas when you can visually tell how much load your right foot is putting on the engine as you drive.
I've had one in my car since 2010 and I'd feel weird driving without it, I watch it a lot while driving... it's fun lol
I've had one in my car since 2010 and I'd feel weird driving without it, I watch it a lot while driving... it's fun lol
Sorry im in Australia,will have to update my profile.
26" tyre
248@50 comp magnum solid ft cam
750 Holley HP
408/360 with 10.5:1 compression
3000rpm.stall
MSD dizzy with no vacuum advance
Wasnt sure if running vacuum advance on this engine would be a good idea or not.
I know this car is never going to get the us30mpg my old ls1 6spd daily driver got but getting the best out of it would be good.
26" tyre
248@50 comp magnum solid ft cam
750 Holley HP
408/360 with 10.5:1 compression
3000rpm.stall
MSD dizzy with no vacuum advance
Wasnt sure if running vacuum advance on this engine would be a good idea or not.
I know this car is never going to get the us30mpg my old ls1 6spd daily driver got but getting the best out of it would be good.
stixx
Well-Known Member
Bloody nice car!
That’s my last build except 750 AFB, 28 inch tire & it’s a manual 4spd. (W/Hooker Super Comps in an E body.)
LJ67barracuda340
Well-Known Member
I've been following this thread from the start,,time to chime in...I've always tried to have my cake and eat it with my cars, what you've got to do when you want to have fun on a budget.
67 cuda, 344, 10.1, Edlebrock closed chamber 63cc, zero deck flat top hyper KB's, .038" quench, hyd roller 222/226 @ .050, 1.6 roller rockers giving .545/.555 lift., Air gap, 3.23 rear (contemplating 3.73), manual 5 speed with .68 OD, 25.5 tires, Dougs and full 2.5 exhaust. FiTech EFI controlling timing and cold air. I didn't go the extra cost for the high precision machining. Just made sure everything was right.
couldn't go the real dyno route so for what it is Desk Top Dyno says 420 hp @5500, 466 tq @4000 with 427 tq @ 2000. Numbers weren't so important just to get the engine in the right range with different parts. The goal was TQ. But the way it drives I believe it's got to be close.
I've recorded a best of 23.8 mpg Imperial or 20.1 mpg US or 8.4 L/100 km hwy @ 120 kph or 74 mph.....I think that covers all the countries....
when I started I said I wanted 400 hp/ 24 mpg. Close enough,,,I'm happy. It can be done with on old technology engine with some modern upgrades and get more fun factor as well. Larry
67 cuda, 344, 10.1, Edlebrock closed chamber 63cc, zero deck flat top hyper KB's, .038" quench, hyd roller 222/226 @ .050, 1.6 roller rockers giving .545/.555 lift., Air gap, 3.23 rear (contemplating 3.73), manual 5 speed with .68 OD, 25.5 tires, Dougs and full 2.5 exhaust. FiTech EFI controlling timing and cold air. I didn't go the extra cost for the high precision machining. Just made sure everything was right.
couldn't go the real dyno route so for what it is Desk Top Dyno says 420 hp @5500, 466 tq @4000 with 427 tq @ 2000. Numbers weren't so important just to get the engine in the right range with different parts. The goal was TQ. But the way it drives I believe it's got to be close.
I've recorded a best of 23.8 mpg Imperial or 20.1 mpg US or 8.4 L/100 km hwy @ 120 kph or 74 mph.....I think that covers all the countries....
when I started I said I wanted 400 hp/ 24 mpg. Close enough,,,I'm happy. It can be done with on old technology engine with some modern upgrades and get more fun factor as well. Larry
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mopowers
Well-Known Member
Just curious- do you have any ethanol in your pump gas up North?
The back of a Barracuda helps in the MPG dept.
driving technique is huge for MPG, (or KPL or ?)
Some of the tips here don't apply, or are a bit extreme, but there are many good ideas & valid points as well.
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
driving technique is huge for MPG, (or KPL or ?)
Some of the tips here don't apply, or are a bit extreme, but there are many good ideas & valid points as well.
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
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LJ67barracuda340
Well-Known Member
Up to 10% in most grades but some premium grade at a few station are ethanol free reportedly...I've been using Canadian Tire fuel which is supposed to be on the E Free list.
Nice! Slightly milder than my wife’s engine.
famous bob
mopar misfit
I agree , I have fuel inj. and its limited to 50 degrees total cruising. I haven`t figured out what it actually does , but the f.i. system controls it .
I agree 100%. I was given my 72 Scamp. It had been neglected, only because the P.O. had to give his wife full time care over the previous 10 years he had it. He loved the car, and took good care of it when he could.
I'm still in the workforce, and have 3 sons, all in school. So I'm super busy. Perhaps many of you are in the same boat. So, unfortunately I don't have so much time that I can tear into the engine. So I'm working with what I've got. When I got the car, it had a rotted out exhaust. All but the manifolds. But I had TTi headers installed and had my guy add bungs to the headers so I could install an AFR. It was a real eye opener. It made all the difference.
Before the AFR gauge, I kept thinking I was flooding the LA 360 (750 cfm Edelbrock) when trying to crank it. After the AFR gauge I realized it just wasn't getting fuel. The AFR made it clear just how much this LA 360 loves gas. Seems like there's no way to flood this engine. It would burn a cylinder full of liquid gas! OK, just kidding. But it seems that way. Now, cranking is a breeze not that I know what's going on. I also changed to a 600 CFM carb.
Tuning for idle, tuning for off idle, cruise and WOT are simple. Unfortunately, I've tuned to the limitations of a carburetor. It is PERFECT at WOT, a bit rich on cruise, and a bit lean on primary acceleration. However, that's because the AFR gives away all the secrets. If I disconnected the AFR gauge and let anyone drive the car, they would say, "it's perfect!" And it does drive well.
I've tuned this car as good as I can tune it on this 1405 Edelbrock. Best case cruise I could probably hit about 18 mpg. A steady interstate cruise at 60 - 65 mph (2,800 - 3,100 rpm) yields about 17 mpg. Not bad.
If I had more time to follow the OP suggestions, I would. Someday (God willing), I will have that time.
Following...
7milesout
LJ67barracuda340
Well-Known Member
so are you saying I have girly engine,,,lol,,,I'm happy with my strong cruiser motor.
As you mentioned sounds like the converter may be an issue. I did a 340 build trw 10-1 pistons, 272/455 purple cam, performer intake, thermoquad, J heads 2.02 valves, and headers, 518 non lock up w/ stock rebuilt high stall 340 converter, 3.55 gears in a Challenger that would knock down 18-20mpg on the highway. I would use more gear or a smaller duration cam if I were to do it over.
No vacuum advance is likely what is killing your mileage. Changing the distributor to a vacuum advance unit would be the first thing I would do in search of mileage.
nm9stheham
Well-Known Member
What AFR are you tuning for at light/moderate cruise? 15-16 is what you want to be under those light load conditions to get to good fuel mileage.
FWIW (and this may not apply to your case) Lean AFR readings at start up is NORMAL for AFR gauges at cold start up. The AFR reads free oxygen in the exhaust, NOT actual AFR, and interprets that free oxygen content as AFR. When the engine is cold, some fuel is not burned and the exhaust's free oxygen content is higher than normal for the actual AFR going into the cylinders; the AFR meter interprets that as lean, despite the actual AFR being correct or close to correct. So don't enrich the mixture when the engine is cold simply based upon a lean AFR reading; it is actually not all that useful for cold start operation. (Which is why engine management systems don't use the O2 sensor when cold...)
RAMM
Well-Known Member
Some posters have a very good understanding of how and why a powerful old school V8 can actually be reasonably efficient. I don't have a lot of time today but tomorrow I would like to re-visit and add a few more points of discussion.
For now though ignition timing is worth spending some time discussing. Getting the timing curve perfect for all driving conditions is not possiblewith just a mechanical advance system. I strongly urge anyone willing to look at a programmable ignition such as:
MSD 6530 MSD Digital Programmable 6AL-2
For those that want more mileage out of their hot small blocks please keep reading and add to the discussion. J.Rob
For now though ignition timing is worth spending some time discussing. Getting the timing curve perfect for all driving conditions is not possiblewith just a mechanical advance system. I strongly urge anyone willing to look at a programmable ignition such as:
MSD 6530 MSD Digital Programmable 6AL-2
For those that want more mileage out of their hot small blocks please keep reading and add to the discussion. J.Rob
BigBlockMopar
BigBlockMember
No real need for overpriced MSD stuff; You can get a programmable ignition box for under $200 ( "Black Box" @ CB-Performance).
CB Performance Black Box Programmable Timing Control Module
The stall convertor currently in the 518-transmission is a late '60s stock 727 unit as found in C-bodies.
A believe 1" larger in diameter than the much newer convertors used in the '90/'00 OD-transmissions, so, besides being heavier, it's probably having more resistance/drag inside too.
I've had a smaller OD+Lockup trans and convertor in the car for a short time once and noticed the engine seemed to rev noticably quicker and wasmuch happier. I'm currently rebuilding that transmission and hope the install it again soon.
CB Performance Black Box Programmable Timing Control Module
The stall convertor currently in the 518-transmission is a late '60s stock 727 unit as found in C-bodies.
A believe 1" larger in diameter than the much newer convertors used in the '90/'00 OD-transmissions, so, besides being heavier, it's probably having more resistance/drag inside too.
I've had a smaller OD+Lockup trans and convertor in the car for a short time once and noticed the engine seemed to rev noticably quicker and wasmuch happier. I'm currently rebuilding that transmission and hope the install it again soon.
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