Does anyone know the RPM for maximum efficiency of the LS1 engine?

Tnx

 

I have not seen any actual numbers that would indicate a hard number to answer your question. I would surmise that the single largest factor in determining max efficiency would be the camshaft. My 99 stock cam had it's best hp output as measured on a DynoJet chassis dyno at 5600 rpm. It's best torque output was at 4640rpm. The lines crossed at 5240 rpm but that is the way DynoJet's hp/tq algorithm works. A different cam profile would change the max efficiency rpm points and different year LS1's had slightly different cam profiles.

 

I think I phrased the question poorly. What I am looking for is the RPM for maximum fuel efficiency, not output.

Sorry.

 

im not sure, but something makes me think its the rpm that the engine makes the most torque at, although it would seem silly to rev ur engine up to 4xxx rpm trying to get max fuel efficiency, however the faster your going the more drag there is too, so maybe its at the lowest rpm u can drive at in top gear without stalling or lugging, dont pay any attention to me, im confusing and i don;t actually know what i'm talking about, jsut throwing out some points

 

Based on the 1-4 skip shift feature and the shift points indicated in the owner's manual, I would say that GM's view on that is to use the lowest possible RPM, probably around 1500RPM for cruising, maybe all the way up to 2000RPM when accelerating. Now hold the flames, I have no personal opinion (fuel economy is not my highest goal) but this seems to be GM's opinion, and they have a CAFE to protect

 

I think i have some input for ya.....

I was driving up to Ohio via NC this weekend.....i was doing 90 to 100 mph for most of the trip and averaged 25 mpg....

on the way back to NC i was running slower because it rained most of the way.....i was doing 70 to 80 mph most of the way and averaged over 28 mpg!!!!!!!!!!!!!!!

I have a 2000 C5 vert MN6.....The tall sixth gear definately helps out....



Oh, by the way.....90 mph is about 2000 rpms and 70 mph is about 1500 rpm....

 

A slight correction. It's 5252 RPM's, and it's the same for all dynos. Has nothing to do w/ the manufacturer. Dynos do not measure HP, they only measure torque. HP is a calculated value.

 

Thanks Dan, I phrased my answer poorly. I should have stated torque to horsepower not hp/tp. Maybe the dynosheet was not centered when the printer drew the lines. I was just reading the chart. However, I don't think all dyno's measure tq/hp that way. Doesn't Mustang use a different curve?

 

its 5280 ...the number of feet in a mile
is 25 mpg good?
i drove to columbus from here 110miles
and averaged 33mpg
god forbid i do the speed limit

HP=(torque * rpm) /5280

 

I have a 99 coupe with A4 and 3.15 rear diff I was driving back and forth on a regular basis from Dallas TX to Jackon Mississippi for 3 month project. I got my best mile per gallon at 77 mph and achieved 34 mpg.
I played with different speeds both higher and lower but for my car, set the cruise control at 77 and let her go.

TD

 

Whoa! Mechanical engineer weighing in here:

horsepower = rpm x torque / 5252

 

Thank you!

 

I think you are referring to an eddy current-type (Mustang / Factory) as opposed to an inertia-type (DynoJet) dyno. They still follow the same rules, still measure TQ (not HP); the main difference is the method of measurement. An eddy current-type dyno has the ability to put a load on an engine at a certain RPM for an extended period of time (resistance to the engine TQ coming from an electric motor, for example), where as an inertia dyno relies on spinning a known weight at a particular rate of acceleration to measure TQ, but once the mass stops accelerating, the DynoJet dyno see's "zero" TQ output.

The general consensus is the Mustang / Factory type dynos are superior in both measurement and tuning capabilities. Problem is DynoJet was here first, and they tend to read higher than Mustang dynos, so most shops know that folks don't want to hear that their brand-new tricked-out motor is producing 15% less TQ and HP than their buddies car (dyno'd on a DJ.) As stated before, dynos are really only useful for back-to-back runs to see the differences when tuning / upgrading parts, etc. Any other application is somewhat speculative.

Old One, sorry for the thread hi-jack, and I don't even know the answer to your question!

 

Your owner's manual tells you for maximum fuel economy (with a MN6) shift into gears at following:

2nd at 15 mph
3rd at 25 mph
4th at 40 mph
5th at 45 mph
6th at 50 mph

downshift when rpm gets to 900-1,000 rpm and/or engine bucks

 

You would think by looking at some of the Corvette drivers that there is only 1 RPM for fuel efficiency...WOT or whatever gets you there the fastest !

 

See: http://www.dynapackusa.com/product.htm

 

Try driving with your DIC turned on to the "instantaneous fuel mileage" setting. I noticed that I squeeze out more MPG when I can see the direct correlation between the MPG and the weight of my right foot. . .

 

It's the lowest rpm you can run at for a specific speed without lugging the engine. As the engine rpm increases, volumetric efficiency drops, waste heat increases, and (rotational) resistance increases. There are people who play games with fuel economy, and they try to run as low an rpm (highest gear) and load (slowest accelleration) as possible for maximum engine efficiency.

 

Yes.. This manufacturer's dyno operates on the same principal as the Mustang (i.e. non-inertia, unlike a Dyno Jet); they just came up with a creative way to attach the dyno input to the vehicle (by spinning the dyno input shaft(s) directly from the wheel, not through a tire / drum interface.) My previous statements still apply. But thanks for the link, always interested in new ways to solve old problems!

 

If you're talking Brake Specific Fuel Consumption (BSFC), that always occurs at torque peak. If you talking about best fuel economy, refer to previous posts. You will not get best fuel economy at the best BSFC point.