DOHC 3.5 Fuel

IncorpoRatedX

Explorer
oh it should also be said that any of the black box ECU's can be tuned using evoscan, plug and play through the OBDII port. I'm not sure how compatible the black box ecu is with the older years harness but i know some of the 3000gt guys use the black box ecu's in their cars to tune with evo scan. I was reading up on this a lot before i did the rebuild on my 96 last year, I have a 50 trim I was going to strap onto it but wound up out of vacation so the rebuild stayed NA, then i sold it and moved south. :)
 

Toasty

Looking for that thing i just had in my hand...
Some market (probably Japan) got a 218 horsepower SOHC 3.5 and as far as i can tell it has all the same stuff as ours do minus emissions stuff. I'd like to see if we can tune for the extra power or at least a little extra with emissions components still installed.
 

The Viper

Adventurer
, you need to reset your ECU, the ecu will need to run for a few hundred miles through various throttle, load and gear situations to work out the long term fuel trim, and might die around town for the first few days as you come to a stop, it has to re-learn.

How do you reset your ECU???

Ive always run premium fuel in my DOHC, Ive tried lower octane, and it simply doesnt run as well on it.

To define the terms "run as well", I mean the power seemed down a little and the gas mpg wasnt as good.
 

IncorpoRatedX

Explorer
your truck is an 03, so just to be safe, since i lack experience with that new of the truck, you'll need to check the factory service manual, but on the older generations you simply pull the MPI fuse, or unplug the ECU for a few minutes, then put it back in. Truck should run rough for about 300 miles but it's re-learning. Expect it to die at full stops the first couple of times you take it out as it might idle too low until it gets things sorted, it's best to do this when you can get some drive-time in on low traffic streets.
 

The Viper

Adventurer
your truck is an 03, so just to be safe, since i lack experience with that new of the truck, you'll need to check the factory service manual, but on the older generations you simply pull the MPI fuse, or unplug the ECU for a few minutes, then put it back in. Truck should run rough for about 300 miles but it's re-learning. Expect it to die at full stops the first couple of times you take it out as it might idle too low until it gets things sorted, it's best to do this when you can get some drive-time in on low traffic streets.

haha better late then never...when i posted my question i actually had a 95 SR, since the question i sold it and bought a 03 monty :)
 
Just have such a hard time popping for Super Unleaded when its 20.00 a gallon in California. But I want to try it on a future big trip. Was able to cruise 80MPH on I 40 on the way home, but a little better power and fuel mileage might or might not be worth the added fuel expense. Just an expensive test.
 

jeep-N-montero

Expedition Leader
Just have such a hard time popping for Super Unleaded when its 20.00 a gallon in California. But I want to try it on a future big trip. Was able to cruise 80MPH on I 40 on the way home, but a little better power and fuel mileage might or might not be worth the added fuel expense. Just an expensive test.

Premium is a whopping 10-15 cents more per gallon, that equates to roughly $2-3 more per tank over the cheap gas, most people waste more than that on crap soda or coffee at work everyday. If $2-3 is that big of a deal then maybe you should trade it for a Prius....
 

IncorpoRatedX

Explorer
Just have such a hard time popping for Super Unleaded when its 20.00 a gallon in California. But I want to try it on a future big trip. Was able to cruise 80MPH on I 40 on the way home, but a little better power and fuel mileage might or might not be worth the added fuel expense. Just an expensive test.

Two questions;
Are you really bad at math?
Do you think facts are often myths (things like gravity?)?

If you answered yes to either of these questions, I fully understand why you aren't running premium.
Otherwise... well... I dunno about you lloyd, you worry me. :D
 

off-roader

Expedition Leader
I don't know about you but I didn't notice much of a performance gain (if any at all) or mileage gain w/ 91 premium over 87 regular unleaded that was equivalent to roughly an extra gallon of gasoline that premium cost you in price.

That said, I've been told there is definitely a difference when you have to smog your vehicle though. Premium + fresh oil change was what worked for me.
 

IncorpoRatedX

Explorer
I don't know about you but I didn't notice much of a performance gain (if any at all) or mileage gain w/ 91 premium over 87 regular unleaded that was equivalent to roughly an extra gallon of gasoline that premium cost you in price.

That said, I've been told there is definitely a difference when you have to smog your vehicle though. Premium + fresh oil change was what worked for me.


Can you elaborate on your 91 "test"? I say "test" because without a doubt, this is not a dispute, and I'm having trouble understanding how/why this is treated as such in discussions on this forum. The actual mapping of the ECU lays out in front of anyone that looks at it, the timing will advance as far as it can until pre-ignition is found (among other variables).

Now, I hope you dont mind but let me lay out a few scenarios to better break down what can happen when someone considers written code in an ecu subject to a 'verification test'

Please read these with a sense of humor in mind, but what I'm about to tell you is true and has happened. - Some folks reset or dont reset the ecu and add higher octane to the vehicle, then proceed to drive as normal for a period of time, usually a full tank and record their data. Often then decide it's not enough of a change, scrap the idea and move on with life.

Other folks may reset the ecu, drive the car for a month and only notice a slight increase in MPG and maybe, like folks in the southwest where 91 is the limit most the time, dont see enough to offset the cost.

Others, even more thorough, might reset the ecu, make sure the air filter is new, fuel filter is fresh, spark plugs and oil are changed or at least clean, drive for a full year, record data, see a justifiable increase in MPG and power, decide to keep going or give up because it's a nominal difference.

Now here's the real over achievers, let me preface this with a 'yes folks, this has happened' in regards to the mitsu V6 engines and the ecu discussions over the years; You have to remember, this engine is used in a lot of platforms and in many balls-out high RPM set ups long before someone in smog capital of the US decided to conduct a 'test' with a giant SUV that's fighting to breathe through a snorkel intake and 4 cat's stuffing up it's exhaust... :D people have done all of the previous check list of filters and fluids etc, then gone as far as completely rebuilding the engine to eliminate the years of sludge built up inside from running conventional oils and low octane fuels, then started fresh and recorded their data, and to no ones surprise, these cars typically saw more power and mpg than the run of the mill, daily driven counterparts.

Did you know that excessive lifter tick can cause 'phantom knock' and force the ECU to pull timing on an otherwise healthy running engine?

What I'm getting at here is; there are a lot of variables in the real world that can affect your perception of something, and if you dont want to run premium, dont, in fact, it's no one's business how you treat your engine... but it's not up for debate; higher octane yields more power and more power will provide better fuel economy from an efficient running engine.

If you'd like to conduct a real test, you need to get access to a dyno and a datalogger, until then, you guys are literally blowing smoke up your own backsides. I'm sorry, I know others on here come from an automotive performance background and they are probably struggling with how to explain this politely to everyone else too.
 

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