Start a Debate

[ProTouring442]

Ok, I am trying to start a debate... but only because I would like to learn!

Totally theoretical; if you were trying to build a motor, say around 300hp that got good mileage how would you go about it?

For the sake of the argument, I'll make it more specific; we'll put our theoretical engine in a fairly light weight car, say a fox mustang. I think they weigh in around 3,200 lbs. We'll put a manual tranny, a six speed to get the double overdrive.

Now, would you build a 302? Maybe a 221 (smallest 302 style block) Sleave down a roller 302 with a 221 crank for a total of 221 and run a turbo? Maybe an intercooled supercharger?

I figure the 231 supercharged V6 in my Bonneville gets close to 30mpg highway in a heavier car, how would a 221 do in a 3,000 lb car?

Open up guys, get creative and technical, please.

Shiny Side Up!
Bill
'72 442 "Inamorata"

[Vegas69]

My 01 Vette has netted me 30 mpg on road trips doing 85. A small displacement V8 and a six speed tranny is going to net you some fair mileage. fuel injection helps.

[Damn True]

300hp and good mileage?

5.3l LS1, stock.

[ProTouring442]

300hp and good mileage?

5.3l LS1, stock.

What sort of mileage, and, more interestingly, can we improve on it? A friend of mine used to pull down 26-28mpg in his fairly stock 5.0 LX, but it fell a bit short of the 300hp mark.

Shiny Side Up!
Bill
'72 442 "Inamorata"

[andrewb70]

My RX7 is 3150 pounds with me in it. It makes 375RWHP and gets 27-28 MPG with a T56 and 4.10 rear gear. If you were really building for economy, I would do a new DoD Gen IV engine. A stock 5.3L will make 300HP and with the DoD I bet it will knock down 33-34 mpg in a 3200 car.

Andrew

[Damn True]

Depends on the weight of the car, the aero, the gearing and most importantly, the drivers ability to keep his foot off the floor.

As far as what can be done to the engine specificly to improve mileage.....that kinda thing is beyond my knowledge base. I'd guess though that like in a carb'd motor an EFI motor can be tuned to lean more toward efficiency as opposed to maximum power output.

[WS6]

Definetly fuel injected and make sure the person knows how to tune for decel fuel cutoff and if you've got the guts you can do the lean drive thing that the holdens do with their ECMs. That'll get you plenty of gas mileage. Oh and only the aluminum 5.3 has 300hp. The truck 5.3 is still what 265 or 285? It can make much more though.

You'll also need to keep the gearing at or near 3.42. Going with 3.73s or higher will start causing you to loose gas mileage. Only one or two miles per gallon but that may be the difference between making 30 mpg or not.

If you're asking about ford motors only though, I have no idea.

[BRIAN]

SVO turbo 4 will probably get most HP and with those small cu in V8's the TQ wouldn't be that far off. There are tons of parts or at least there were. Add the turbo and fuel injection and you would meet all your criteria in a cheap low weight package that is a bolt in.

[THX 138]

Long rods, high compression, long intake runners (for torque)gearing to take advantage of the torque for low rpm crusing.

[chicane67]

The DOD package definately........

[BA.]

...just thinking out loud here.

To get the mileage part of the equation you're really going to have to have an engine with great Volumetric Efficiency, right?

And, if that's right, you'd want it at those lower RPM's I would geuess.

While that can be done with high compression and a small cam and tuned exhaust using FI,.......I think you can more easily exceed 100% at lower RPM's by using a roots supercharger.

For the parameters you've given, I wonder how a small cid engine (221-302) with FI, smallish cam, 5 or 6 speed tranny and excellent Intake/Exhaust ports would do compared to something like the LS1 or something like the Mitsu Lancer or Subaru STi.

For comparison, my old Lexus has a 4.0liter (243cid) using Variable Valve Timing and it gives about 23-28 at highway speeds.

[Nine Ball]

My C6 (rated 400 hp) used to average 30-31 mpg @ 70 mph on the highway when it was stock. With the supercharger, cam, headers (now approx 635 hp) it still pulls down 26 mpg with a 3.90 gear.

Most stock LS1s with 6-speeds see ~30 mpg, especially with longtube headers and no catalytics to restrict them.

[MarkM66]

Long rods, high compression, long intake runners (for torque)gearing to take advantage of the torque for low rpm crusing.

I like the low rpm torque ideal.

DOD would be great, but to keep things more simple. Try to get the most torque using the smallest amount of cubic inch displacement. Gasp! You could probably even put a decent set of heads on a 305 and get 300hp. 305's are basically free, find a set of cheap L98 heads, etc. budget build type deal.

Put a 6 speed behind it, and idle down the highway at about 1200 rpm.

Could probably get 30 mpg, even with a carb. Spring for a wideband tunner.

[Colvindesign]

the 1993 Lincoln Mark 8 got 30 mpg and had 300 hp.

Put that engine (with the stock ecu, etc) into a fox, lighten it up a bit, and you should be looking at over 30 highwy. Gear it right, and it'd be even better.

[Scott Parkhurst]

I think the insane turbo 4-cyl idea is a better one. Minimal weight, can be spun to 9,000-plus, and the 2.3 is a proven player.

300 peak hp would be easy, and fuel economy with a 4 isn't a question. An adjustable wastegate turbo with an intercooler would offer killer performance on demand.

Why bolt in a V-8 without maximizing the cubic inches? For the street, it's the best option. If you're going to pay the weight penalty a V-8 brings, it might as well bring an assload of cubic inches to the party...

~SP~

[ProTouring442]

Look Scott. just because you are raking in the big bucks with my "Lifetime Memberships" doesn't mean I'm loaded too! Ok, just kidding!

You make a good point, but wouldn't a small displacement V8 be more efficient than a 4? Smoother? I dunno. Hell, I don't even own a Ford, much less a 302 or a Turbo Coupe, I'm just thinking outloud... pretty cool for a guy who can't really think!

Heh... heh... you said assload!

Then again, wouldn't a nice 302 with a supercharger, intercooler, 6-speed, and highway gears pull pretty good mileage?

Shiny Side Up!
Bill
'72 442 "Inamorata"

[MarkM66]

Why bolt in a V-8 without maximizing the cubic inches? For the street, it's the best option. If you're going to pay the weight penalty a V-8 brings, it might as well bring an assload of cubic inches to the party...

~SP~

Because the "assload" of cubic inches needs fuel to feed them.

Weight isn't in question here until we know what type of vehicle it's going in. If it's going in a 3500lb+ vehicle, I don't think a couple extra hundred pounds for the engine is going to make or break it. And the low rpm torque from a V8 will be needed for that type of weight.

When you say, "for the street, it's the best option." I'm not sure what you're refering to, the V8 or the turbo 4.

[Scott Parkhurst]

Because the "assload" of cubic inches needs fuel to feed them.

True, but a longer stroke can make adequate torque at a lower rpm level for highway cruising in O/D, and with proper gearing the larger displacement/longer stroke engine could very well equal the fuel economy of a smaller-displacement variant. e.g.- I bet a 383 SBC could match a 327 SBC with all else equal in a Chevelle-sized car, if the rear gears could be played with. The 327 might have to run at 3,000 rpm to comfortably cruise at speed, but the 383 might be fine at 2,500.

Weight isn't in question here until we know what type of vehicle it's going in. If it's going in a 3500lb+ vehicle, I don't think a couple extra hundred pounds for the engine is going to make or break it.

I'm inclined to agree...but I think a 2.3L four-cyl is more than a couple hundred pounds lighter than a SBF. I could be wrong.

And the low rpm torque from a V8 will be needed for that type of weight.

If the vehicle in question is more than 3,500 lbs., a 4 cyl is not a good call...I agree completely.

When you say, "for the street, it's the best option." I'm not sure what you're refering to, the V8 or the turbo 4.

I was referring to maximizing the cubic inches in a given block. I firmly believe in pushing cubes in street applications, since cubic inches will contribute to power across the scale and any further mods will have more impact on a larger-displacement engine versus a smaller one. I'd never build a 327 if I could build a 383. The only reason not to maximize displacement is if there's a rule limiting you from doing so or if the economics prove impossible. If you can, when you can, always run the bigger displacement engine.

But, that's just my opinion...what do I know?

~SP~

[Turbo T]

My roomate's STS turbo'd LS1 ('99 SS) makes 470hp/489tq at the wheels on a conservative tune (people have gotten 500+rwhp from this kit) and still knocks down 28-30mpg in 6th gear. If I could, I'd put a T-56 in everything I own.

* I should point out, he's running stock intake and exhaust manifolds, stock Y-pipe, stock displacement, stock everything (other than fuel injectors, ecu reflash, and the turbo, of course).