I've been noticing lately that ls1's tend to get alot better mileage than lt1s. I would like to start a descussion about the real reasons for this.
example.
There are alot of ls1s over at ls1 tech that are pulling 30-34mpg on the freeway while being over 430whp.
My lt1 when properly tuned should make somewhere around that number, but I have never heard of an lt1 doing anywhere close to that ,after it was cammed.
Do they get better mileage because of head design, faster ecm, or what.
I would just like to know what peoples thoughts are on this.
Thanks,
Kory

The LS1 is a bit lighter than the LT1, but I don't believe anyone who claims to be getting 30-34 MPG in with either motor, less yet a modified 400+hp LS1.

I think we're getting to a price where MPG claims are getting inflated just like HP claims have been for years...

I think head design and port flow has a lot to do with it. But anyone who doesn't have an MDS/DoD system in their ECM and claims 30+ mpg out of something pushing 400 RWHP is out of their mind.
Making more mpg can be a by-product from making an engine more efficient and thereby making more HP, but more likely, making more torque.

The example I'd give is my '94 LT1 is pushing over 400 HP at the crank, and quite a bit of torque down low, I can squeeze 24mpg average out of it doing 70mph with 3.23 gears on a 4L60E in OD going between a place that's 400 ft above sea level and 2,000 ft above sea level on a 500 mile trip.
My friend has an LS1 he makes the exact same trip with, no headers, but a CAI and catback exhaust, and he gets about 27. But then again, he has an M6 as well.

Generally speaking it depends on a lot of limiting factors contributed to good/bad fuel economy:

Temperature/Weather- Headwinds, w/ wind, is it 100 degrees etc.
Elevation
Passengers
Auto/M6?
Driving Habits
RPM's @ speed limit
Does car have problems or not?
Mileage of vehicle..sludge, wore out parts?
Quality of gas used in car
weight of vehicle
modifications

Feel free to add, anyone. That's all I could think of off the top of my head. I'm still getting 15-17 in town and 26-30 on the hwy (averages)

I got 33mpg highway when my Z was stock. I can only get 27mpg highway now.

Even my truck got 26.5mpg highway last week during some testing I was doing - now that was a shocker.

Come on now. OK, first of all, I'll agree that a high-performance engine is a more
efficient engine, which relates to a cleaner and more fuel-efficient engine. But to
pull 30-34 MPG on the freeway (with a legacy V8), you'd have to drive in a very
conservative, deliberate, and very controlled manner.

Personally, I added headers/CAI , a new FLT tranny, 3200 Yank, and realized a 14%
increase in gas mileage. I'm sure a lot has to do with a "tighter" driveline with the
new tranny/converter, and opening up the breathing on both ends. Not to mention
new plugs, cap/rotor, wires, and other simple mods. If I drive conservatively, I can
yank anywhere from 24-26 MPG.

Anyone can increase their MPG by simply changing their driving habits. Other things
you can do are to run more efficient tires, ensuring proper tire air pressure, ensuring
the engine is always tuned properly, using proper gasoline, using a more efficient oil,
ensuring the engine is operating at proper temps, ensuring all the driveline components
are in proper working order, and improving the aerodynamics.

EDIT: my car has 160+ miles - a freshened engine would reveal better MPG.

I got 25mpg with 2.73s and stock with a bad 02. I could easily see more with the 6 speed.

Also you have to take into account the age of the LT1. Older pumps/filters/emissions/plugs/wires/etc. make for worse mileage.

Fuel economy in these cars is all based upon various factors, but usually to max out MPG it comes down to volumetric efficiency within a narrow powerband that allows for the lowest driving RPM for a given MPH coupled with the drag coefficient of the vehicle at that speed...

Now, the LS1 cars have the one advantage to it, and that is the 'advanced' engine design, in that the intake runner length, the rod length, revised bore/stroke combination, the revised firing order and higher ratio rocker arms, all of which improve the engines efficiency, coupled with the temperature stability of an all aluminum block, which allows for a forward cooling system design which keeps combustion temps higher, again aiding efficiency...

LT1s can be designed to produce great MPG along with high HP numbers, but realistically you have to do a 'max-effort' design to pull it off, all of which are pretty much by 'borrowing' the same design criteria the LS1s have (revise the firing order, go with a long-rod 350/355, higher ratio rockers and a properly engineered cam design), which should be able to net over 400rwhp as well as 30+mpg...

It would probabyl be easier to just start with a LS1, as you gain not only the newer computer systems, but also the lighter motor...

LT1s do not really do that bad, as for example, when I picked up my '95 Z28 convertible I drove from Virginia back to Wisconsin and averaged 28-29 mpg over the trip and that was with a Eibach Pro-kit lowered suspension, 245 profile tires, 3.42 rear gears with a M6 tranny averaging about 70-75mph the entire way back... The car has 387rwhp with heads/cam/rockers/intake/TB/headers/exhaust... What really helped was that there were few tolls until you got to Chicago, and I was able to use cruise control for the majority of the 12 hour drive... Oh, and I might as well mention the car had a stock bottom end with 78k miles on it when I picked it up...

Dennis

BTW, how have you been doing, Kory?

Thanks for the replys. Keep them comming good decussion.
Not too bad Dennis how's life been treating you?
Kory

I get about 230 miles to the tank, DD, but I think something's wrong somewhere, I'm mosfiring occasionally. Then again I drive it HARD most of the time.

stock i was getting 28 mph from nd to salt lake city??

with the gears i dont know what i get now.

That trip must have taken a long time

I got 29.7 to myrtle beach and back when the car had nothing but cai. who knows what I'll get now with the cam LTs and everything else!

because LS-1 where made by the hand of god....


or so, I was told

i got 29-31 on the highway with LTs, intake, exhaust and rockers... after the cam i managed 25-27mpg (these are over an 1100 mile trip) running pig rich at partial throttle.. so i think if my AFR was cleaned up i could get ~28-29 with the cam... but i also have 2.73s and an M6