Tuning! For GM vehicles

[The Atomic Ass]

I know I've ranted about this somewhere, but can't for the life of me find the topic.

Anyway, we're making progress on my father's truck. No aeromods, because he doesn't want "a truck that looks stupid." I think I can get him to start posting his numbers though, and they're better than they've ever been, what with new tires and running at sidewall pressure. (Took a lot of convincing on my part to get him to part with door-sticker numbers, even though he replaced the PASSENGER tires with TRUCK tires).

But one thing I noticed is just how pig-rich it's running. When I go to shift, the engine stays revved for a while, and it can take literally 3 seconds to drop to the RPM required by the next gear. Not good.

Is there ANYTHING out there that programs GM ECMs? Preferably without the licensing garbage, as my father also has a Bravada, and my mother a Blazer... And did I mention cheap?

[LeanBurninating]

Hmm...

So the way the revs fall is your only indication? What kind of truck is it? What motor? Year? How many miles?

Some motors just have so much rotating mass that it just takes them a long time to wind down. Take for example a traditional american v8. Because the way the crankshafts are designed, the crankshafts have very heavy counter weights to keep things balanced.. blah blah stuff like that.

You may be right, but I would bet that it is not running excessively rich. There are other ways to tell. Check the spark plugs for one. Also, the factory "tune" on the truck may just work that way, it may just make the revs float when you back outta the throttle. Or maybe there is another problem.

As far as tuning goes, it sounds like you just need some basic starting point info. If you want all out complete adjustability of everything, then that is called a stand alone system. Its basically ripping out the entire factory computer system and replacing it with an aftermarket one. Race car stuff. Don't do that.

Then there are what they call "piggy backs" where its basically some kind of module that either bolts up to the ecu or plugs into it somehow to reflash it.. etc.. Much cheaper and easier to work with, although in some cases less effective.

I think you may be asking a lot. Car makers dont build computers that you can "customize" ... you gotta find somebody that can crack em. Its tricky business, because if you do it wrong you can really screw stuff up. And it goes without saying, few aftermarket companys would spend time making a tuner for a car or truck that is not popular to modify for performance. And those tuners - which may be your only real option - are usually not specifically designed for fuel economy.

Hats off to you on spreading the ecomodding fever, and best of luck.

[stevey_frac]

Basic standalone systems cost about $3000 to start. If you want one to run a relatively new car your probably going to have emissions problems. They really are designed for racing, and off-roading, and it's generally kinda hard to beat the fuel economy of the stock ECU without breaking things. Running rich has a tendency of causing carbon buildup, so if they can they'll run a hair lean once the car is warmed up. They can't run too lean without causing knock and NOx problems. They only thing you could really do, and make significant headway would be if you physically modified the engine, and needed a tune to match your new engine parameters. Such as if you put atkinson cams on a regular car which would improve fuel economy significantly, or if you upped compressions, or you were going to run ethanol only, or something like that.

[99LeCouch]

Look into HPTuners. It will let you tune a lot of things in the GM ECU's. And works on a lot of domestic vehicles.

I think you're after transmission behavior and quickening the shifts/altering shift points.

[stevey_frac]

Originally Posted by 99LeCouch

Look into HPTuners. It will let you tune a lot of things in the GM ECU's. And works on a lot of domestic vehicles.

I think you're after transmission behavior and quickening the shifts/altering shift points.

Oooooo.... You shouldn't have shown me that... Fancy.... ./giggle

[KidInCandyStore]

[The Atomic Ass]

Originally Posted by LeanBurninating

Hmm...

So the way the revs fall is your only indication? What kind of truck is it? What motor? Year? How many miles?

S-10. 2.2L. 2001. Around 60K.

Originally Posted by LeanBurninating

Some motors just have so much rotating mass that it just takes them a long time to wind down. Take for example a traditional american v8. Because the way the crankshafts are designed, the crankshafts have very heavy counter weights to keep things balanced.. blah blah stuff like that.

Granted there are motors with less inertia, but key off from 3K RPM results in a stopped motor within 1.5 seconds. Return to idle from 3K results in minimum 5 secs.

Originally Posted by LeanBurninating

You may be right, but I would bet that it is not running excessively rich. There are other ways to tell. Check the spark plugs for one. Also, the factory "tune" on the truck may just work that way, it may just make the revs float when you back outta the throttle. Or maybe there is another problem.

I did neglect to mention this isn't a new issue, it's done this since it was purchased 4 years ago. Plugs/wires didn't affect it when replaced some time ago, and the plugs did not appear particularly out of line. I suspect it runs fairly close to proper while at speed, it's this closed throttle crap that really bugs me.

Originally Posted by LeanBurninating

As far as tuning goes, it sounds like you just need some basic starting point info. If you want all out complete adjustability of everything, then that is called a stand alone system. Its basically ripping out the entire factory computer system and replacing it with an aftermarket one. Race car stuff. Don't do that.

Couldn't afford to do that, anyway. The bare minimum I'm looking for in control is complete control over DFCO. I want the engine to PLUMMET as if it had run out of gas when letting off the throttle.

Originally Posted by LeanBurninating

Then there are what they call "piggy backs" where its basically some kind of module that either bolts up to the ecu or plugs into it somehow to reflash it.. etc.. Much cheaper and easier to work with, although in some cases less effective.

I'm hoping for something cheaper than Powertech, that would work for both the 2.2L and 4.3L, and not be restricted to one car per device.

Originally Posted by LeanBurninating

I think you may be asking a lot. Car makers dont build computers that you can "customize" ... you gotta find somebody that can crack em. Its tricky business, because if you do it wrong you can really screw stuff up. And it goes without saying, few aftermarket companys would spend time making a tuner for a car or truck that is not popular to modify for performance. And those tuners - which may be your only real option - are usually not specifically designed for fuel economy.

You'd think they'd see the EcoModder's knocking on their doors by now.

But anyway, have any of the tuning shops with the big expensive hardware seen the light yet that you know of?

[The Atomic Ass]

Originally Posted by 99LeCouch

Look into HPTuners. It will let you tune a lot of things in the GM ECU's. And works on a lot of domestic vehicles.

I think you're after transmission behavior and quickening the shifts/altering shift points.

Is there shift behavior in the computer of a manual vehicle?

Edit: Just noticed it was set as automatic in my profile... Fixed.

[LeanBurninating]

Originally Posted by The Atomic Ass

I want the engine to PLUMMET as if it had run out of gas when letting off the throttle.

you mean.. like this?

http://www.youtube.com/watch?v=IPzGf...eature=related

If you are looking for that, build a really cranked out motor with extremely light weight internals and very high compression, the more unreliable the better.

[Christ]

The engine should rev down as soon as you let off the gas pedal... my dad has the same engine in his S-10, and it doesn't float.

The float is probably attributed to input/output sensors, honestly. You should get a datalogging tool and start seeing what they're reading at... compare those readings to OEM specs, and adjust/fix accordingly.

Start by cleaning your TPS, throttle body, and Mass Airflow sensor. Those are the most common things to be dirty.

Also - take a can of ether (starting fluid) or carb cleaner and spray around all the gaskets which are in the intake path... spray down all the vacuum lines, etc... this will check for vacuum leaks, and if the engine stumbles while you're spraying in a certain area, or idle speed increases dramatically for a second, you have a vacuum leak... this will definitely affect your spin down speed.

Check the Idle Air Control Valve as well. If it's sticking (it's an actuator/solenoid) it will allow too much air to pass the throttle plate...

[theunchosen]

MM. . .

I am doubting its one of the sensors. If it were a sensor it would lag on the front end as well(under acceleration). But I don't think there was any mention of that.

It could just be that the spring for the throttle body is worn out. A quick fix would be to either grease or WD-40 the spring and the hinges for the throttle body. If you want to find out if this is the problem(you are going to have to pop open the hood to look around anyway. . .) just open up your intake tract until you get to the throttle body. Pull back the gas with the clutch in while someone else watches. The plate should snap back shut immediately after you release the gas meanwhile the rpms should cycle downwards rather quickly.

I predict what you will see is the throttle plate slowly drawing backwards. If I also had to guess I would say your engine doesn't quite shut off the GO when you let off the gas, but this might e masked under normal driving by the fact you are applying the brakes and not really paying attention to the revs then. less effective braking would be another sign of this(quick shift from accel to brake and its still throttle open acceling, while you try and brake).