How to build a muscle car for better fuel economy?

[BLSTIC]

It's only 12:1 I thought? That's conceivably gasoline range

[cRiPpLe_rOoStEr]

Originally Posted by BLSTIC

It's only 12:1 I thought? That's conceivably gasoline range

At first the OP mentioned that compression ratio, but later mentioned that could go higher than that. But anyway, considering that such ratio is more frequently seen either in smaller-displacement engines which combustion chamber volume is inherently less sensitive to pre-ignition or in modern direct-injection engines, water injection is still not a bad idea at all.

[BLSTIC]

Oh I see. Nascar used to run around 15:1 with very large quench pads and cams with basically zero overlap didn't they?

In this age of cnc everything, surely pistons can be machined so that even valves can form part of the squish pad? That would make for the ultimate in turbulence and small combustion volume

[Ecky]

Originally Posted by BLSTIC

Oh I see. Nascar used to run around 15:1 with very large quench pads and cams with basically zero overlap didn't they?

In this age of cnc everything, surely pistons can be machined so that even valves can form part of the squish pad? That would make for the ultimate in turbulence and small combustion volume

Turbulence isn't always desired. Mazda's new gas engines will have something like a 16:1 compression ratio, and get away with this by having a stratified charge.

[BLSTIC]

And direct injection, which allows them to run rich just around the spark plug for excellent detonation resistance, because the majority of the cylinder is really hard to auto-ignite.

[cRiPpLe_rOoStEr]

Originally Posted by BLSTIC

Oh I see. Nascar used to run around 15:1 with very large quench pads and cams with basically zero overlap didn't they?

I'm not aware of Nascar rules, but with such a high compression ratio it would either require a lot of anti-knocking additives or resort to an approach similar to what Toyota does with its hybrids in order to enable them to emulate the Atkinson effect.

[BLSTIC]

I just learned that that was apparently in early restrictor plate days, which makes sense. Vacuum = lower pressure at BDC = lower pressure at TDC, raised CR restores that to normal levels. Doesn't play nice at low RPM though.

But it does beg the question:

Does an increase in CR, with a corresponding decrease in ignition advance because pinging, result in an efficiency improvement? How about a power improvement?

Going from my 9.7:1 Barra 182 pistons & head combo to that of a 12:1 Barra EcoLPI apparently should yield a 5.4% increase in efficiency

The Otto Cycle: Compression Ratio vs. Efficiency

But if it costs power at high loads because of ignition timing being too far from MBT I'm not really interested

[gumby79]

Back in99- 2000'ish the Chowchilla Speedway track Championship car for the street stock division had 14:1 forged domed pistons forged scat rods scat crank world steal heads I2.02" E1.60" Holly 4412 (500cfm).097" jets( two sizes larger to compensate for power valve delete) 600hp (estamated). We could lap 2nd place. 114 octane race fuel . MSD ignition throughout 6A box 32 degrees fixed timing.
Ran the same motor for the full season tore it down to rebuild it at the end of the season the parts that came out had better tolerances than the new parts out of their boxes running Mobil 1 full synthetic changing it every two weeks AKA two races 8 quart oil pan. 2 speed Powerglide replunbed for direct drive no torque converter had a valve that acted like a clutch by reduced line pressure to first gear and slip the clutches real finicky easy to burnout. On our first race taking the green flag we broke the weld on the drive shaft our weld on the rear help factory weld on the front is what broke was our only dnf( next shaft we did all the welding) end was a Ford 9-inch 6.83:1 gear at6800- 7200rpm ( motor was capable of being spun 9000rpm rev limiter was set for 8,000. 2weeks before Race season started we had a mishap when we broke in the Cam there was a hairline crack in the block and number 5 while we let it settle down and cool off after breaking in the cam for 30 minutes water poured into number 5 under pressure 4:1 gear reduction starter didn't even hesitate as a blew the cylinder wall out of number 5 hydrauliced. the Piston was sent off for metallurgical analysis because it's shattered like it was cast. That is the nice thing about blueprinting the motor it is easier to duplicate your results. .
Now add water injection if the track had allowed it and the compression could have been taking much higher. Throw on some aluminum heads that's two full points of compression so are 14:1 compression motor would be happy with aluminum heads at 16:1 all else being equal. The late models that came in from all around the country were running aluminum blocks aluminum heads 18:1 compression most on methanol some on race fuel chromoly chassis 1600 pound car making 800 horsepower those guys were fast. They told me at this level of competition if you're not spending $40,000 on one motor you're not expecting to finish on the lead lap most of these teams had three spare Motors and a complete TurnKey car tuned to the same as the one they were running. The big times came to a small town dirt track

[cRiPpLe_rOoStEr]

Originally Posted by BLSTIC

Does an increase in CR, with a corresponding decrease in ignition advance because pinging, result in an efficiency improvement? How about a power improvement?

Then I don't know, but I remember some dedicated-ethanol and flexfuel cars had an increased ignition advance along the higher CR.

[Ecky]

So, looks like the 2019 Dodge Ram will be a hybrid. Not just that there will be a hybrid model, but it's standard equipment. They've opted for an altermotor.

2019 Ram 1500 eTorque system: What it is and how it works

The 2019 Ram 1500 that was announced during the Detroit auto show hit us with a goodie bag full of improvements: lighter overall weight (by 225 pounds) stronger frame, lower coefficient of drag, better fuel economy, plus more payload and towing capacity. Those last three can be partially attributed to new technology dubbed eTorque. But what exactly is eTorque?

Well, in a literal sense, it’s an alternator (the vehicle's electrical generator) replacement -- the 2019 Ram no longer comes with one because the eTorque tech provides the electricity. But in addition to keeping the 12-volt battery charged, the motor/generator quickly restarts the motor when the automatic stop/start system is used, and it adds assist as a mild-hybrid system. That’s right -- the 2019 Ram is technically a hybrid. And that’s with either of the two gasoline engines offered, V6 or V8.

While most of the Ram 1500's electrical systems still use traditional 12-volt power, eTorque is actually a 48-volt system. It uses the aforementioned motor/generator, an eight-rib belt with two tensioners, a DC inverter to convert 48 volts to 12 (for the traditional electrical systems), and a battery pack about the size of a small suitcase that can store up to 430 watt-hours of energy. The total eTorque system, cables and all, adds about 100 pounds of weight to the truck. The battery pack is located inside the rear wall of the cabin.

What you get in return for the weight penalty is a 90 lb-ft of torque boost with the V6 and a full 130 lb-ft worth of help with the V8. There are two different levels of output because of packaging constraints for the V6 engine, which requires a slightly smaller eTorque unit mounted in front (there’s plenty of room under the Ram’s hood, but the eTorque V6 will also find itself in other models, like the Jeep Wrangler). The V8’s larger system is found exclusively in the Ram right now and mounts exactly where the alternator usually lies.

The 2019 Ram comes either with a 3.6-liter V6 outputting 305 hp and 269 lb-ft of torque or a 5.7-liter V8 with 395 hp and 410 lb-ft. And those peak numbers are unaffected by the eTorque system. The extra oomph comes in when the gas engines are at low speed, like between idle and 1,500 rpm, before they are able to produce bigger torque numbers on their own. The hybrid system broadens the torque band as opposed to adding to peak torque available.

And that’s just fine. Peak torque is useless when you’re trying to pull your 22-foot deck boat out of the water at 0-2 mph. Adding torque down low not only helps get heavy loads moving from a standstill, it takes stress off the powertrain while doing so.