Capt Fiero

Ok, I don't post here too often as frankly if I don't have something constructive to say I usually just keep my mouth shut. I can find most answers to my questions using the search function, however, this one is kinda out there. Last thread I found was 3 years ago, and 10 years ago with any real input.

I live in BC Canada, fuel prices have skyrocketed. Regular gas is now $6+ premium is now $7+ a gallon. (roughly $5 USD - $6 USD) I am pretty sure you Yankees can dang near, buy race gas at that price. The car I am putting together at the moment is an 87 Pontiac Fiero with a 6.0 LQ4, 78mm Turbo, MS3 Gold Box, 5spd Manual should spin around 2300rpms at 75mph with my 255/40/18 wheels/tires. Car should weigh in around 2900lbs complete.

My goal is to find a way to tune the MS3 Goldbox so that at part throttle cruise say less than 25% throttle to run it on the lean side to increase both throttle response and fuel economy. Then as soon as the TPS reaches WOT have it ramp into a much more aggressive tune. I have a GM 5 wire MAF that I could use, but currently planning to just run on MAP. I have always tuned for performance through efficiency. I could get 32mpg out of my 4.9 V8 5spd Fiero in the past.

I'd love to hear other peoples results with tuning and fuel economy. Hell anyone with a Boosted LS motor what are you getting for fuel economy.

chiaj144

iTrader: (4)

I was getting close to 30mpg imperial with my old turbo mustang 5.3/4l80E with 3.08 gears on the highway. I kept leaning it out until it started to sneeze then just added a touch more fuel.

Capt Fiero

I didn't know any yankee's even knew what an imperial gallon was. Thats what about 25mpg US Gallons. When you leaned it out, did you lean it out over the entire curve or just at low / zero boost levels? What kind of timing were you running. I need to find the balance between lean out vs timing. I know the leaner you go, the less timing you need, and vice versa the richer it is, the more timing you need. At least that has been my experience with fat injectors / small injectors and doing a fuel pressure changes of up to 20psi.

Game ova

3750# f body here (boosted). Gets 15.5 miles per U.S gallon on the freeway with zero spirited driving, and this is with 2:73 rear. Car is on E85.

shiny_lux

Interested in this also, am in NZ and 98 (~93 octane equivalent) is $2.40 NZD per litre that I work out to be similar to what your payin' in BC. I'm building a daily driver (4.8L TT) and I'll be running a standalone computer so keen to get the part throttle cruise as miserly as is safe...

Capt Fiero

If you are getting 15.5 on E85, I should be able to pull off at least 24 on 94 oct pump.

I know that most of you don't daily your Turbo LS cars, but I want to be able to take my kids to school, swing by the Track make a few passes or laps, then go get my kids after school, or use it for a spirited run to the grocery store. Maybe even someday do Drag Week with it. (I live on the wrong coast for drag week, but I can still dream can't I) I can be on the Pacific coast in under an hour. The only real good thing to where I live, I can be at Mission Raceway Park in 8mins. It's roughly 6 miles from my front door. They have a 1/4 mile track and a road course.

Now back to fueling, I bought a new set of Deka 80lb injectors from EFI Source when I bought my MS3 Gold Box. After exchange and taxes, total bill was over $2500 Cdn as I wanted the Fiero specific harness they make for LS swaps.

Capt Fiero

I hear ya, I'm in the same boat, with huge gas prices and the desire to drive fast daily drivers, it takes some tweaking to get it done, but god dang it, I won't drive an econo box that barley gets better gas milage than a tweaked hotrod.

truckdoug

iTrader: (25)

you should be able to hit 20 ('merican units) pretty easy in something small and aero. i'm damn near that with a 70's squarebody pickup

it's probably more about driving habits than anything else.

Game ova

You on E85?

truckdoug

iTrader: (25)

nah thats old fashioned gasoline

chiaj144

iTrader: (4)

I'm in Ontario, lol. I just leaned out a few cells in the cruise area then blended them in with the rest of the map. Can't remember the timing but I never changed it from the normal map.

gametech

iTrader: (1)

The fuel burn rate is on a curve. Too lean or too rich will need more timing, not less. Just make damn sure you only experiment with this at low load/part throttle. I did some lean cruise experimenting with the GTO, but the factory computer reverts back to stoich so often as a sanity check, that the results were not worth bothering with.

LS1-IROC

iTrader: (4)

With my IROC (LS1/T56, TC78 turbo and 3.55 gears) I can manage 30mpg on 93oct. on the highway if I stay out of boost. It gets the best gas mileage out of all my other vehicles..lol

jordoza

My 12 camaro would get 21 mpg on the freeway on gasoline. Around town the 3800 stall killed mpg. I drove it everyday for years with a lsx376 and a s480 set up making 770 or so on low boost settings for the street. 4l80 and 3.45 rear gears. Driver has a ton to do with mpg. If i hit it hard even once that mpg was out the window quick.

Capt Fiero

That is awesome. If I can make high 20s I'll be super happy.

I'll have a manual so I'll probably drive it around town at barley off idle, only get i over 2500rpms when I want o let it rip.

I'll be running an MS3 with the ultimate tunning software. (paid $250 for the software over the price of the MS3 box. P.S. I LOVE THE GTO's.

I have been hearing 12-14 degree's of timing is safe for around 12lbs of boost on 94oct pump gas.

Aero is actually been improved over stock to aid in cooling and high speed stability. I wanted it o cruise stable at 150mph. Being in Canada we do still have some Wide Open Spaces of highway.



Just o add some extra info, when the car is complete, it should weigh in around 2950lbs with full interior, power windows, mirrors, locks. I haven't decided if I am going to re-install the AC Compressor, but I am going to leave the rest of the AC system installed so if I do choose to do it later, it will be easy. The trans I am using is a 5spd It has a .72 Overdrive 5th with a 3.61 rear diff in the transaxle. So effectively a 2.61 5th gear at the rear tire. I'm going to HUGE for a Fiero 18" wheels with 245 or 255 40 series rear tires. IIRC its about a 27" tall tire. Eventually, I'll install the F40 6spd conversion that FieroGuru on this site is doing to his LS4 Turbo Fiero. I know from reading and seeing videos'; 600hp Automatic Fiero's on simple drag radials and pump gas run 10.30's at the track, so that is pretty much my goal.

truckdoug

iTrader: (25)

Sounds awesome. My wife is from Edmonton so I am familiar with those wide open spaces. I would think investing in an egt sensor you could log with the ms3 would aid in tuning for cruise economy.

jasonsnova

i got little over 19mpg with my nova last year with a not so mpg friendly tune. combo was
71 nova , 6.0 s475 , t56 trans and 3.50 rear gear.
im sure i could get it into the low 20's playing with the tune and being a little easier on the right foot

JoeNova

14 city, 24 highway, and I couldn't keep my foot out of it. Something like 18/28 if I drove a little more modestly.

Forcefed86

iTrader: (4)

Don't believe there is much/any advantage to running leaner than stoich? If you go leaner that 14.7 it will be down on power and likely require more throttle/DC/RPM to maintain the same power level at your desired RPM.

You're looking for the most complete burn possible. Too lean and you're lacking power too rich and you're wasting fuel. I've seen many argue this as well. But IMO if there were big advantages to learning out the mixture beyond 14.7... you'd see it in the big car companies. Hunting for the best MPG is always at the top of their engineers lists. Yet every OEM ECU vehicle I'm aware of targets stoich at cruise.

As far as timing goes you want to run the "correct" level of advance that nets max torque at your cruisie RPM. MBT timing will differ for every setup.

High base compression and a short duration cam with a wide LSA helps as well. My 10:1 5.3 was netting 18mpg highway on E85 with my setup at about 55mph. 3.10 gear 29" tire with a glide abound 2900lbs. Pump fuel should have net me around 23. Thats through an unlocked converter and 9". I'm sure a manual setup like yours should be able to hit 30ish+ if done correctly with enough gear.

With the MS3 I auto tune the whole unloaded AFR map to 13.8 or so. When done I smooth the map and setup the closed loop fuel control to shoot for 14.7. The ECU will automatically hunt for 14.7 this way. Regardless of ambient temps loads etc...

truckdoug

iTrader: (25)

you do see it in car companies. just not in the US. leaner than stoich tends to create higher levels of oxides of nitrogen...something we are loathe to do here as it creates smog.

in rural australia...not so much. I have an '04 GTO p59 computer/OS/tune that has the lean cruise tables. it'll go out to 16:1 under low load high manifold depression operation. but give it 2% more throttle and it checks back to 14.68:1

anyways it's really not gonna gain you much mileage. it's all about how you drive. is every stop sign a chance to get into boost? or do you mostly "walk softly and carry a big stick" ?