nuke61

I currently have a C5 Z06 with 402, F.I. with 600/600 rwhp/rwtq, and I'm going to sell it and get a C6 Z06. My car went from 30 mpg at 65 mph when stock to 22 mpg at 65 mph with the F.I. motor.

So, I know it's an oddball question, but what could I expect from a stock C6 Z06 for mpg, to H/C/I (don't want to do F.I. again) for mpg? The range I'm talking about is 550+ rwhp? I've done a lot of lurking here and I'm leaning toward something like a Mamo ported MSD with NW 102, BT Stage 3 cam, AHP ported heads milled .02 -- something like that.

meinersk

Mods wise seems like you read....mileage is 3mpg down from stock numbers or less...driving normal that is.....

KM177122

In my experience an aggressive camshaft is the biggest killer of fuel economy. I was getting 27 MPG on my Vortech Si setup(A&A kit with intake but utilized a stock long block(stock cam) and stock exhaust). The kit came with 80lb injectors and a KB boost a pump and made 601whp on 93 octane. Loved the setup but wanted more. Now that I have further built it(to include fuel system) the fuel economy is much worse(still working out some kinks with the tune and fuel system). With that said, if you care about fuel economy then I would stay away from an aggressive cam(which is where you will get the majority of power you desire in a NA setup). Just my .02

nuke61

Thanks meinersk, I was hoping that a high compression N/A motor should do much better than my car does now, even if it's a 427.

KM177122, with an otherwise stock 346, but with an S-Trim at 6 psi (540 rwhp) my car got 28 mpg, so I know just an S-Trim on an otherwise stock motor doesn't hurt gas mileage much, but I'm just interested in an N/A 427. Seems like the BT Stage 3 does fine at 65 mph cruise, so it doesn't sound too aggressive to me.

The reason I'm interested in mpg, if anyone is interested, is that I make frequent trips from my new home in the Phoenix area to my hometown of Oceanside, Ca, a 600 mile round trip drive. I think at the mid 500 rwhp range, I can have pretty good mpg too.

KM177122

Makes sense. I think a mild cam and a mild tune will net you decent MPGs, probably mid 20s(so you're not pushing it in the fuel department too much). Should be fine at 550whp level. I'm sure you know this but ever since I put LT headers on my C6Z I have a tendency to keep the revs about 2K otherwise the drone is fairly annoying(which impacts MPGs). So I find myself cruising in 5th more than 6th unless I'm going much faster and keeping the revs above 2k.

v8sten

mine i had an agressive cam (BTR Stg 4) and around 12:1 cr (more fuel, less timing) and i was able to manage 16 city/25 hwy, 18 mixed

jayyyw

That's not bad at all.

nuke61

Sweet! I'm looking forward to it.

TheSenator

16mpg average with a cam that has 24 deg of overlap. (HCIE car)
Dash shows 20-23mpg cruising in 5-6th.

Unreal

Its all in the cam. Can be a 2-3mpg hit or a 8-10mph hit.

Fuel system has zero to do with mileage. My car with triple 465s and 140lb injectors get stock mileage, because it still takes same amount of fuel to idle at 650rpm and put around at 900rpm as before, and same stoich ratio.

Big cams need idle bumped up. They need to run richer at lower rpm. They need to be kept at higher cruising rpm to avoid surge/issues. This is what kills mileage. If you pick a very low overlap cam, the changes will be minimal.

7007vette

590 rwhp 14 mpg

AzDave47

K501 cam (17* overlap, I think), MSD, NW102 and the rest, 602/489 rwhp/tq, 12-16 in town, 22-24 highway on 91 octane, idle is set at 950 rpm.

I improved 1/2 mpg after the HCI build running 90 miles at 150 MPH, though. I gained ~9 MPH trap speed in the 1/2 mile over stock.

outhouse

My build with the 116 cam averages 10 mpg which is mostly city driving with hills.


Tuner wanted to play it safe and it might be a hair on the rich side, drivability is outstanding.

ratomicZ06

i have similar build w k501 cam, heads, lt. My hp numbers are only at 580 or so, but i get 28 mpg, indicated, but only at 70 to 75 mph. If im at 70 mph or slower i use 5th to avoid drone as unreal says, then im at 22mpg at 65 mph in 5th.

Hope that makes sense. Only lost a couple mpg with parts/hp addition. BUT..... if i close the m2w switch, no drone anywhere!

Gearpuller

BTR Stage 3, ported intake/throttle body, WCCH ported heads, LG Super Pro headers no cats, Vararam cai, 575 rwhp, 15-16 city/24-25 hwy .

nuke61

Fantastic to hear, because I'm thinking along the same build as yours, and those mpg numbers at that rwhp is terrific.

C6z06man

17 city
27-28 Highway
K501 cam
~575HP

KM177122

Agreed unless you are running a monster injector like I am (ID2000s) which can't be scaled down any further and eat gas like none other(which is why I'm downgrading). But I digress LOL

v8sten

my mpg was actual, not what the dash showed, but the dic was close due to stock injectors just a hair over 600 rwhp

AzDave47

It's all in the tune and I know I am running rich both from A/F numbers fronm the dyno runs and the black tailpipes. I ran the Omega NFZ 1/2 mile roll races this weekend and even with the full throttle half mile passes the tail pipes were black. The tune was done recognizing I do track events down to 600' elevation to high speed event at 3000' DA and 6000' DA. My B&B Fusion III Extremes have light to modest drone at 60-70 and gets very quiet at 75-80 with the flapper valves closed. It screams with them open!

I don't really use the DIC for fuel numbers, but miles?gallons. I don't have any full tank highway driving numbers but run 6th gear at 60 MPH and above.