LILS

Most people posting here are looking to optimize power and/or torque from an LS engine. I want to look at a different problem: optimizing fuel economy and reliability. The constraints on the problem are essentially that you must use stock or readily available aftermarket LS parts, and that any power and torque levels between those of a stock LS1 and a stock LS7 are perfectly acceptable -- significantly more or less power or torque might not be acceptable, and closer to LS7 is better than closer to LS1. You can assume a nearly constant load at a nearly constant RPM -- at least 75% of maximum output at something close to the RPM for peak torque.

What engine would you choose to build to get both high fuel economy and high reliability under the given conditions and constraints?

Stroke:bore ratio is an obvious concern, and there is good research indicating that, all else being nearly equal, the best fuel economy is achieved with a relatively small bore -- i.e., stroke:bore between 1.1 and 1.2; however, trying to achieve that kind of ratio in an LS engine will either result in a very small bore (and very likely valve shrouding or even interference problems) or a very long stroke (and small rod:stroke ratio) compared to stock....

Sbertolone

iTrader: (5)

jw is this for a fan boat/propeller boat?

you could probably get away with more timing than usual due to it not being fully loaded. other than that having someone who specializes in marine cams doing up a custom cam would help the most, and eliminating as much internal engine, and accessory drag. an undersized centrifugal or smaller turbo sized to making peak torque at your operating conditions would probably be the best power adder.

being as im just guessing as to the application, lots of gauges and datalogging could help in going a long ways with an engine like this seeing constant duty.

LILS

Close. I was really thinking about a constant-speed aircraft propeller, but these would all be fairly similar usages.

silverz28camaro

iTrader: (20)

First question I have is what are you exactly doing with this ideal engine build?

Second is what type of tranny do you want?

the auto 4l60e is what i have in my camaro, its great for drag racing , but any 6 speed will kill me mpg wise. they have 2 overdrives. Choosing the right tranny and gear ratio will net you better gains rather then worrying about bore and stroke combos, a recent nascar race was won by changing gears and being able to make one less pitstop to win the race,

If you really want to get the best mpg go with a stock ls1 with a free flowing exhaust and intake with little to none accessory lose, no ac, no ps, elec water pump, underdrive pulley,

Or going with a turbo is usually the best way to get mpg out of anything.

Also weight is a big factor, I did a little research on this before and read somewhere that for every 100lbs it is worth 3% or so fuel economy.


Give more info on what you are wanting to do!

LILS

I just did in the post right before yours, but you seem to have ignored it.

As I said, I was really thinking about how to make most effective use of LS-based engines in aircraft with constant-speed propellers -- but that applications is not dissimilar from airboat or more typical marine applications. As such, multi-speed transmissions aren't generally used and thus aren't really an issue. Sustained operation within a narrow RPM band and at a high but not maximum load is the norm, and reliability is a must.

As far as turbos go, in the application I am thinking of, a turbo will already be used, but for normalization not boost in the usual sense -- i.e., the turbo provides essentially zero boost at sea level and enough boost at cruising altitude so that the engine produces the same power that it does at sea level.

silverz28camaro

iTrader: (20)

damn dude sorry,

anyway, with the aircraft idea i would think the ls7 fits best as it has the factory titanium rods, it will love to be revved constantly at 3,500 rpm or whatever it would need.

You know it would be nice if there were titanium rods for the stock ls1, then you could keep the smaller cubic inches for fuel economy and have low drag internally, also look into sodium filled valves that come equipped in the 2002 ls6 heads, they are a little lighter.

silverz28camaro

iTrader: (20)

when my overdrive went out i still drove it to the track wit h3.73 gears.

3,200rpm @ 75 mph for 100 miles,

That was when the car had 125,000 miles on it, now it has the od fixed and 133,000 miles

runs 11.56 @ 117 on stock bottom end, I do have ls6 heads, and a good high flow high pressure oil pump.

Sbertolone

iTrader: (5)

damn, how fast is this airplane going to be? i figured this engine would be too heavy for aviation applications, because, im no expert in the aviation field, but the turbo continental thats like 300hp looks to be a lot lighter. and... well i'd be worried about these engines sustainability in normal overhaul intervals, like a 400hp ls1 running for 2000 hours under boost?

and what kind of FAA certification issues you might run into, cause damn... an LSA with 400hp would be bookin' like probably over 250mph cruise, and its been a while but i thought they had power restrictions. and thats a lot for that airframe of that weight.

LILS

I'm just trying to figure out whether there is a relatively easy way to go a half-step beyond what David Algie is already doing. If you want to see a lengthy talk by David, largely about his LS engine plans, have a look at this video.

Sbertolone

iTrader: (5)

whoa!!!!! that is a wicked wicked airplane. whats this going to cost like 500, 600k? do you plan on using it for air racing?

LILS

Costs are hard to estimate firmly, since Algie is still working on making all the parts to get the first plane flying, but completing a kit should be much less than $500,000. A Lancair Legacy is an obvious competitor, and they run less than about $300,000 to complete the kit (less than $200,000 for a minimalist version.) I'll have no plans for the plane at least until David can actually produce kits, but any such plans almost certainly will not include air racing -- although an appropriately modified LP1 could end up being very competitive! At this point, this is just a very interesting development effort that I am watching closely.

gametech

iTrader: (1)

A little bit off-topic, but I would think a dry sump oiling system might be a good addition. I don't believe the stock oiling arrangement would be very effective in negative G conditions. Seized bearings could be really bad at altitude. Back on topic, I would guess the turbo could use what would be normally considered a large exhaust housing in a constant velocity situation, minimizing backpressure.

Ari G

iTrader: (25)

I would start and change the cam and get the tq down in the rpm get Peak tq close to where you spin the engine when driving

You can allso think of it in this way,the more power you make the more fuel you need to use