As I've read many post regarding mild tuning, it seems like that a good start is headers/x-pipe, cam, intake and heads. When you say "heads", does that mean porting of the original cylinder heads, or do you get new ones?

This type of tuning, which I understand could get you to approx 400 hp, what does it do to your fuel consumtion? To be honest, the "friendly" consumtion of the standard LS1 is appealing here in Norway where we pay approx 7 USD for a gallon of fuel....

 

Heads could be eather ported stockers or aftermarket. If you keep the cam to reasonable specs it won't hurt fuel mileage at all. Heck, I have a heads/cam wet sump 430 cubic inch LS7 in my C5 and get 26+ mpg on the highway and 19ish mpg in town.

 

You should be able to get 400 with headers and cam. Easier with heads, but you could opt for used 243 (LS6 for one) heads for quite a reasonable price.
As for mileage it really depends on your right foot. I get 15.9MPG in the city in my Z (stock aside from headers, X and aftermarket air intake).

 

I have headers, Vararam CAI, LS 6 intake,X-pipe with high flow cats and a tune from ECS !!! when stock I was around 28 mpg highway and now it's around 26 to 27 !!! as the previous poster said I think the difference is my right foot !!!( the sound and power is awesome)

 

You might see a slight decrease in MPG depending on the cam and your right foot, but the performance will be noticeable. The only thing that would make me hesitate to do what you propose is the cost of gas you have to pay.

 

in my experience the gas mileage gets worse the more power you try to make... when my car was bone stock it would get a legit 29ish mpg on the highway just cruising without putting my foot into it... now it gets about 13-15 driving normal whether that be in the city or on the highway and worse when driven hard... a lot of high mpg claims are made with extensive mods but I tend to wonder if they are going by what the dic is saying (not the actual mileage), the tune is super conservative, the car is rarely or never driven hard, or a combination of these things... personally I'm more concerned with performance so the gas mileage isn't a big deal to me... longtubes, intake, stock ls6 intake manifold (if you don't already have one), stock 243 heads, and a small cam should easily get you over 400rwhp on a 6 speed car

 

My car has AFR heads, cam, fast intake, headers etc etc.
A4 with a stall.
In town depending on traffic, I can be as low as 12 mpg and as high as 15-16.
Highway is 24-25mpg observed on the DIC.

It's the crawling through traffic that kills the fuel mileage.

 

agree with everyone---My mileage after head/cam headers only went down less than 1 MPG on the freeway---Average mileage was similarly only 1-2 MPG less-
However my car was an automatic which always will have less MPG's than a manual trans--especially after major mods----
If you are looking to get the best of both worlds----Same mileage as before but more HP ( 400 RWHP) then I would be more conscience of your mods----
Being your car is a 98 LS1---I would simply purchase a set of STOCK LS6 heads or heads from early Z06's --- called "243" heads---
You can find Z06 take off heads for like $600 and new ones for under $1000 Going the conservative route there would be no need to buy expensive aftermarket heads costing as much as $2000---- Even STOCK 243 heads are plenty capable of 450 RWHP
2nd mod would be to get the LS6 intake as your car has the old LS1 intake that will become your bottleneck in your combination
3rd the cam----A good choice for an all round cam would be something in the mid to high 220's of duration at .050--Lift doesn't matter much but try to keep it below .575
Now LSA is important on a cam---A sock LS1 cam has a LSA of 117---The lower the LSA the lopier the idle--- A mild cam will have a 114 LSA and a more aggressive one a 112--
I assume there are No smog passing in Norway---Only a cam with a 114 or higher will pass smog in calif----So If you have no smog---then I would get the 112---
4th--- LT headers will kill your mileage---The further aft front 02 bungs will make them read incorrectly and there is no 100% fix--even with tuning---The P/T fueling will become RICH--making it use more fuel----I would buy a set of "shorty headers" OR a set of STOCK Z06 take off headers---
Finally a re-tune after all these mods is absolutely required--With a mild set up you can even get a mail order tune if a full tuning shop is not in your area---OR you can purchase the Diablo tuner--give them all your mods and they can accommodate them and correct the tune----
Mileage with a manual trans is greatly affected by the driver--far less than an automatic that shifts the same every time----Best is to never let the engine "lug" by having in a too high of gear---Going thru the gears try to shift at the same RPM's all the time like maybe 3000-----

 

Thanks for all the informative feedback.
Of course, to get the hp there is "the other way", and thats supercharger.
Lots of Hp with no other mods. As I've understood, the supercharger is nice on the mpg, untill you start to move the right pedal of course.
As for smog- or other approvals, in Norway we have a bi-annual EU-approval - test. The car is there tested for everything from structural things to emmisions and even a visual control if the car is tuned. So if I can't find a "friendly" tester, thing like heads with "racing" printed all over, supercharger etc will have to come off every other year.

What are your views on the supercharger in general?

 

Loved having a supercharger on my LS-based 5.3 truck.

Love having a big cam sound on my naturally aspirated vette.

 

I Like them!

I'm surprised the inspection is so tough there, we have sold a handful of supercharger kits in Norway and never heard of that. I would think you could just remove the head unit and brackets and get away with that for inspection, but you would certainly know better.

 

On my 2006 C6 (LS2), I managed to pickup about 1 mpg in town and almost 2 mpg on the highway with LG 1 3/4 SPro headers, Borla cat back, FAST intake manifold and cold air. Given those mods the car picked up 47 rwhp and almost 60 rwtq over stock so it is very possible picking the right parts and gaining power. Base line 357 rwhp / 348 rwtq, after was 404 / 410.

You could also do heads on the car and add more power.

Doing the camshaft however typically is going to drop in town driving a bit, but highway cruising MPG should not be that much affected.

 

Anthony and his team at LG Motorsports :agree: installed on my car their Long Tube header package in addition to an Batwing air filter, Corsa indy exhaust, factory clutch, etc. Nothing too radical but the key was their teams tuning of these additions aftermarket components. Not only did I gain about 30 to 35 HP, my gas mileage stayed constant at 32mpg on highway cursing. Very happy.

 

There was new added control points to the "EU control" in 2015, where visual inspection for tuning is one of them. But it's an bi-annual test, so it would not be too problematic to remove the kit (or parts of) if necessary....