First Goal: 550hp LS1 Getting 30mpg

[drmiller100]

Originally Posted by bazman

That does make sense on the surface however the goal was great power and throttle response at large throttle openings, and very fuel efficient at small throttle openings. .

You are not being very logical.

and your choice of a 5.7 is, well, limiting you very much.

You'd be better off with a 5.3, change the valve springs, and run some boost. 800 horsepower and better mileage then you are dreaming is entirely possible, but you seem to already have it all figured out.

Best wishes,

Doug

[bazman]

Originally Posted by drmiller100

You are not being very logical.

and your choice of a 5.7 is, well, limiting you very much.

You'd be better off with a 5.3, change the valve springs, and run some boost. 800 horsepower and better mileage then you are dreaming is entirely possible, but you seem to already have it all figured out.

Best wishes,

Doug

I wasn't being a smart ass Doug, I understand the conventional wisdom, and you are not wrong.

However, everyone knows and understands smaller motors are easier to get good mpg out of. Why stop at a 5.3 when I could buy a built Evo, run 800hp and get even better mpg out of a 2.3?

My goals are to show that larger engines can still justify their existence. The 5.7 is simply what I have and as I did not want to spend more money on it yet - high boost was not possible on the stock LS. MOst of us here start with what we have right?

When I do have the spare coin for a built engine it will be bigger, not 5.3. That is not because your idea will not work, but because that is not what I'm trying to prove. i.e. My buddies twin turbo Viper getting 30mpg from 8.2L is a far bigger achievement than me getting 35mpg out of a 5.3.

[smokey442]

I am curious as to what your leak down % is.

[bazman]

Originally Posted by smokey442

I am curious as to what your leak down % is.

Sure. It was tested after it had run over 100,000 miles to see if the motor would take boost given we're also about to tighten quench with a slightly thinner head gaskets and so compression was going to go up a bit too.

The old girl was between 7-8% on all 8 pots and had 155-160psi compression

Several oil changes previously I had added Militec-1 to the engine, trans, and diff and that might have contributed to the engine being in such good condition.... of course that might have been normal anyway

[smokey442]

Good move with the gasket swap. Consider a set of Total Seal rings on your next engine. I'm a big fan of their product. Second position gapless has worked well for me. The worst I've ever tested (Chev SB 400) was 2%. Difficult to keep cylinders round and straight in aluminum block for all operating parameters because of the different expansion rates of aluminum and iron based liners. Keep up the good work.

[bazman]

Originally Posted by smokey442

Good move with the gasket swap. Consider a set of Total Seal rings on your next engine. I'm a big fan of their product. Second position gapless has worked well for me. The worst I've ever tested (Chev SB 400) was 2%. Difficult to keep cylinders round and straight in aluminum block for all operating parameters because of the different expansion rates of aluminum and iron based liners. Keep up the good work.

Yes, you are definitely onto it. A new LS1 apparently was typically around 5% so I figured 2-3% wear over 100,000 miles good. When I build a new engine, I am torn between something like this on a new LS3 or 7 block:

GM LS Superdeck II Short Blocks

or going to an aftermarket LS block and having it hot honed and the rings hand prepped. I know a local race builder that does this and his engines have broken world records and typically are around 1%.

Getting down under 2% will be worth energy by itself. Adding friction and thermal coatings will also salvage some pumping and heat energy losses.

The ultimate for me would be a billet block like LSM make, but I can't justify that in a sedan... we'll keep that one for something worth it like a ZO6 and make some serious power and economy. Can't afford that right now

[brucepick]

Originally Posted by bazman

...
My goals are to show that larger engines can still justify their existence. The 5.7 is simply what I have and as I did not want to spend more money on it yet - high boost was not possible on the stock LS...

I think that's very much a "worthy pursuit". In other words, well worth doing.

Having pushed my admittedly small 1.6 liter engine to nearly 60% above the U.S. EPA's fuel economy estimate, I'm convinced you can considerably increase a large engine's fuel economy if you limit it's revolutions. You burn a LOT of fuel pushing those pistons up and down, and all the other reciprocating action hardware in there too. Valve train components go up and down repeatedly. That's momentum created and destroyed thousands of times per minute.

Anyway, if I were ecomodding a large engine GM car I'd do these things, primarily. Used TOGETHER, I'm convinced they will improve your mpg significantly. And I think this list is the best set of tools you could use for it.

0) Tire pressure. Start with the sidewall max imprint and see if you want to adjust it from there. It's #0 because its basic, in my humble opinion.

1) Manual transmission, with as tall a gear ratio as I could possibly pull together.

2) A kill switch. Kill the injectors so you can coast in neutral with no fuel used. Learning to use it to full advantage might take a while, but well worth it.

3) Aero improvements to reduce the amount of work the engine needs to do in order to make the car move. Having done multiple aero mods on my relatively underpowered car I can now detect the difference in performance.

As for for the manual, with as tall a gear ratio as possible: Give yourself six or seven gears if you can, and a really tall rear end. 5 speeds will work if that's all that's available. With all that power available, if you want to surge forward there will always be a gear that will do it.

A case in point is my little Civic. The HX version has taller gearing than other Civics of the same year, for better fuel economy. If I want it to seriously move out on the highway, I drop it from 5th to 3rd and rev-match at about 4K rpm. That's at about 60 mph or so in my car. Give it fuel and off she goes. If I required big power in 5th at highway speeds, it would have to be geared "shorter" with higher rpms and fuel economy would be worse all around.

Anyway, that's my two cents. I ran on some but hopefully it will be useful.

[bazman]

Thanks for that. Love the kill switch. I think the key to that is a restart button next to it unless my tuner could somehow refire by wire on the throttle. That'd save gas in a commute for sure. I've tried it at lights but my remote is out of sight when ignition is on and the engine immobilizes a few seconds after turn off - creating a hasty panic to get the car re mobilized then restarted by key before the light goes green.... your solution is perfect for that.

[02ws6]

I know that GM has had the technology to kill the fuel on a certain amount of cylinders depending on how much throttle you give it for years... Don't know how well that will play in in your ride since you have a custom tune..

I know alot of guys who mount turbos in their cars and run the stock LS6 cam until they can get a custom profile made.. These cams work very well in boosted cars.. They still have about a .56x lift and either a 113 or 114 LSA.. Don't quote me on the numbers but I know Im close..

For your particular car, since it is a "4 door GTO", weight is your number one killer of mpg.. If you had this setup in a 3000lb. car as opposed to your 4400lb (Im guessing close to the '96 Impala SS numbers) car this wouldnt be so hard to achieve.. That would be my most main concern would be dropping weight..

Aerodynamics could be a big help for you too but please don't go make that car ugly.. Its too pretty of a car to put a nose cone or boat tail on.. Maybe a custom belly pan could help out alot without costing a bunch of money.. Im gonna be using a truck bed liner for my belly pan.. Im sure you can come up with plenty of ideas on this one.

About the only other change I personally would make to this beast would be your personal driving technique.. Its gotta be hard to stay out of the throttle on this thing.. When I owned my Trans Am I know it was hard to keep rear tires on the damn thing. lol

Only other suggestion I would have is to buy a commuter car that can double the mpg of what you are driving now. Thats what Im personally doing.. Building a car that can attain 40-65mpg while Im in school and when I can afford it, then build my street/strip car..

Good luck and happy modding!

Oh and post pics of the car and drivetrain setup!! I wanna see this!

[bazman]

Thankfully the 4 door is no where near 4400lbs even wet with me in it, but it is certainly heavier than a WS6 or Vette.

My turbo cam is 222/226 on 114/115 with .575 lift so more duration than the LS6. I'd like the LS6 intake though because they flow better than the early LS1.

The economy goal is not to save money, I can afford to put gas in it and drive it how I want to. It's about the challenge of getting more from less.