Camaroz18

iTrader: (1)

I have a 2002 Pontiac trans am ws-6 M6. Trying to find a heads cam package that will significantly increase my horsepower while maintaining or increasing my mpg. I was looking at AFR 205CC Heads with a custom grind cam but that doesn't seem like a route I wanna go for mpg And hp.

Mapping it out on a tuner will be the key. I have seen a couple threads posting about running lean maps for when you're cruising and having an alternate map readily available when you really want the hp. Is it possible to have an alternate map that activates at WOT?

(Goal is 38-40mpg) yes, its possible
Current mods are Magnaflow Exhaust, SLP Maf and SLP Air intake
Any other part lists are welcome

Thanks

Camaroking1996

Are you high? expecting 38-40 mpg's out of a heads cam ls1? U'd be lucky to get 25

Camaroz18

iTrader: (1)

38-40 is my ending goal after all my parts are on and all tuning is done.
This thread is just the first step towards that. 450 hp and 40mpg. That's what I really want. If you don't wanna post, then don't. I could care less. I just want someone to post with real knowledge about LS1s

Camaroking1996

450hp is easily obtainable through the ls1. But 40 mpg's with heads and cam is not plausible at all..

badazz81z28

iTrader: (6)

There is no way to get 40mpg out of an LS1 unless you shut down half the cylinders. With power in the 400-500hp range, I would call yourself lucky with 25mpg! If it could be done, more GM and ford performance cars would be sportin it.

crainholio

iTrader: (2)

What info do you have that supports this statement?

I'm getting 26-28mpg on the highway cruising near the speed limit, if there's a way to get more I'm interested.

NW-99SS

iTrader: (6)

I like it! Take the challenge and show the naysayers! Not sure 450rwhp is attainable with the mpg you're after, as you will need to limit injector size for econ. But I would say you should be able to approach 400rwhp with a decent injector and tune (tune for econ) and possibly attain high 30s. Maybe use the imperial gallon to help you get started! Also, limit cam size for a lower end torque curve as you will want to make as much power down low to help with low rpm cruisin down the highway.

Honestly, I have seen some really amazing mpg from stock LS1s here in Canada. Using imperial gallons, one guy hit 38mpg on a road trip during the summer (cool enough not to use a/c). There are a lot of variables here and many will doubt your results, but at least you will know the truth. High tire pressure will help, along with harder compound tires, rather than softer, traction oriented ones. Synthetic fluids for rear, trans, etc. Find a good day without a headwind (tailwind would be perfect!). Things like this can add 1mpg here and there and get you closer to the goal. Underdrive pullies I think would help. Maybe electric water pump (mechanical load vs alternator load - not 100% sure on this one). Take out as much rotational mass as possible. Aluminum flywheel, carbon fibre driveshaft, lighter wheels (use 16s as the smaller the rim, the lighter it is).

Not sure how far you want to go, but there are ways to get really respectable fuel econ from LS1s!

RoidedSS

weight reduction for the car itself will also be key in this. obviously the lighter you can get it the less mass you have to move. i think there will be some mpg's in your drivetrain you select. also, is running a turbo an option? a really small turbo will get you your power goals, maintain great driveability and only come in once it spools (again your rear gear will determine a lot of that for your highway cruising). also, I don't know if i missed it, but is this flywheel horsepower or rwhp? my z06 setup (243 heads and z06 cam) didn't lower my mpg's at all. At least it wasn't noticeable and rated from the factory it was good for 405 horsepower (yes i know this is just a rating). my mpg loss mostly came from my stall speed and getting rid of all the emissions stuff. also there is rumors the next gen small block will have an 8 speed transmission. idk if or how that would work but it would certainly help you mpg...goodluck, i'm intrigued by this now

Camaroz18

iTrader: (1)

No, because GM and Ford build cars for comfort, styling, power, fuel economy, and cheap price. Fully equipped cars. Factor out the price and comfort and you have more room for fuel economy and power.

Mr. Sir

Here's the keys to obtaining your goal:
-weight reduction
-choosing a rear gear that puts the engine at low rpm and medium-high load. The result will be reduced pumping losses (as well as low acceleration power without downshifting).
-EGR. It fills the cylinder with (mostly) incombustible exhaust, thereby keeping cylinder pressure up; it also helps reduce pumping losses. It reduces combustion temperatures as well, allowing you to run a leaner A/F ratio.
-Compression. It increases burn rate, allowing you to capture more power from a given amount of fuel (decreases emissions as well).

There's also a method of increasing the efficiency of the combustion cycle by closing the intake valve significantly later than normal. Today it's known as the Atkinson Cycle (the true Atkinson cycle is notably different). The power loss involved with the late IVC means it's pretty much useless if you want to obtain 450rwhp. (if you still want to know how it works): It allows some of the air in the cylinder to be pushed back into the intake. The resulting loss in air volume decreases dynamic compression. This is why Atkinson Cycle engines generally run 12-13 static compression ratios. The idea behind the Atkinson Cycle; when fuel and air are ignited, it causes a change in pressure. When the exhaust valves on a conventional Otto cycle engine are opened, there's still pressure in the cylinder, and it's bled off (wasted). By allowing less air to be retained in the cylinder, the power stroke (expansion) is fully completed by the time the exhaust valves open (meaning cylinder pressure is equal to atmospheric pressure).

If I were you, my realistic goals would be 420rwhp and 35mpg. You'll have a hard time achieving yours.

Camaroz18

iTrader: (1)

Define Imperial Gallon. And yeah, I have the 16's on there already. Carbon fiber drive shaft, lighter lug nuts. Lighter rims. Nitrogen in the tires. Its possible. It may cost money, but I know I can do it. Thanks a lot for your support

Camaroz18

iTrader: (1)

Turbo is in the future, as in couple years future, but yeah, I am considering anything

inssanity21

iTrader: (16)

im baby cam'd and got 30 in 6th at 60mph behind a truck for around 100 miles. (used 8.2 gallons of fuel and went 250 miles total ) not bad if i do say so myself

99Bluz28

iTrader: (35)

1 Imperial Gallon = 1.2 US Gallon

You'll also want to make you car more aerodynamic (lowering, etc...).

speed_demon24

iTrader: (6)

Nitrogen will hurt your gas millage since it builds up less pressure with heat. Less pressure = more rolling resistance.

RoidedSS

which means the nitrogen will stay more consistent, so just over inflate a bit to get better fuel economy in the city as well

trans_am7935

iTrader: (15)

i got between 26-28 on my heads and cam package, on a trip to SoCal. i would say a bunch of weight reduction, lowered, and run the lighted rims you can find. drag light alunimum rims, skinnys up front and back!

Tony Mamo @ AFR

iTrader: (13)

I think thats good advice.....and even achieving those goals would be an impressive feat.

Its almost the "FAST, RELIABLE, CHEAP" thing.....(you know the ending....pick two because that's all you will ever realistically have). In the OP's scenario I'm suggesting that he may be forced to pick one or slightly compromise both.

Something has to give because a 346 CID engine capable of 450 to the ground (530 ish at the crank) is going to need the proper valve events to get there and if your forced to keep the valve timing light (for MPG reasons) you are going to need an extremely efficient cylinder head.....a ported stocker wont cut it IMO (port gets too large before it becomes reasonably effective at moving air).

And you should be considering an AFR head if your serious in your quest (or a similar clean sheet design with an efficient small runner). In fact when we were going for our CARB number with the AFR 205's back in 2004, the government agency doing the testing noted that with our heads, not only did the engine produce more power than the stock 243 castings, they also reduced hydrocarbons (burned cleaner) and increased the MPG by a coupe of points in their particular testing (they were impressed actually and shared that with the owner of AFR who passed the info along to me....I was very pleased with that news as you might guess and I was confident it was due to the completely different approach I took in designing it (focusing on a smaller port than stock but a much more efficient higher flowing piece). Some of you may not even realize it but the AFR 205 was THE first aftermarket LS Gen III cylinder head to hit the market.

Anyway, getting back on track, my former 346 which I debuted and used as a promotional vehicle of sorts for that new at the time 205 head, gets close to what your looking for but even that combo, as good as it was, falls short of your lofty goals by a decent amount. However it was actually generating 25-30 more ponies than your target so reducing the cam timing some would have increased the MPG (and hurt power of course) but that should be noted here.

I would have to add that duplicating my combo meant you pretty much threw budget out the window and I worked really hard at completely optimizing that particular package (basically my quest was to make as much power as I could with a smallish 224 cam....MPG wasn't much of a concern but either goal still requires a very efficient engine/driveline). It was an extremely detailed / very optimized build and to this day is arguably the strongest 224 cammed car I have seen.

My Vette would get about 28 - 30 MPG on a straight HWY cruise at 75 MPH or so.....but that's a non stop cruise in light traffic (very little braking and accelerating) on flat tarmac. Not very realistic IMO but it was fun for bragging rights. If I drove it in normal type of situations (some Hwy and some around town stop and go stuff) it would get about 22-24 MPG if I didn't flex the throttle much....if I was in the mood to play it would quickly be in the high teens (still very respectable for a car that would trap 124-125 MPH)

And keep in mind my Vette had everything going for it in the MPG department.....it was (is) a very aerodynamic car with a light clutch, carbon fibre prop shaft, light rims and tires, electric water pump.....all the things you would need to do to get closer to your goals. Truthfully, having spent the better part of my life dedicated to this hobby and the last 10 years or so hyper-focused on Gen III LS engines, my opinion is that your goals are bit unrealistic, even if you had cubic dollars to throw at the project but of course that's just my opinion (although my opinion is based on a reasonable amount of real world experience and the mathematics that drive this hobby).

I should mention compression would help your cause but thats a catch 22 because if you took my combination and shrunk the cam sat six degrees or so (to help out the economy side of the equation and thereby reducing my 475 - 480 RWHP to closer to your 450), the dynamic compression would go thru the roof and you would have a harder time getting this combo to run on pump gas because the DCR would be really high. Big cammed cars you can crank the static up getting close to 12 to 1 because the dynamic compression is still workable on pump fuel due to all the cylinder pressure bled off from the cam overlap. You could run some methanol injection of course.....that would help.

Anyway....I could go on and on. Having done something similar and knowing how many small details were hit to get there, I would say you have you work cut out for you.

The suggestion by "Mr. Sir" which I quoted at the very beginning of this post is a really good one IMO and honestly even those targets would be an accomplishment, but I think those figures are closer to the realm of doable if you have the coin and the determination to see it thru.

I will be rooting for you either way.....its always fun to push the envelope some!

Good luck!



Regards,
Tony

Syclone538

Not sure if it will help any, but I'd look into what has been done at A/F leaner then 14.7, some much, much leaner.
http://en.wikipedia.org/wiki/Lean_burn

Displacement on demand also comes to mind.

Extreme weight reduction, especially rotating weight.

M6 with something like a 3.08 or 3.23. Testing would be necessary I would assume. Say you just do the math and choose a gear that puts you at 800 rpm at 65 mph, it might take too high tps % to hold that speed efficiently.

Don't think you can do much about aerodynamics, but lowering, a chin spoiler and a rear diffuser might help.

I really doubt this is a good idea financially, but would be interesting to see what is possible.

Whiteaw57

iTrader: (2)

youll spend as much getting it to 40mpg than you would just paying for the gas youd save. Good luck but I hope this is for nothing more than bragging rights