I am thoroughly impressed with GM's 3.1L engine [Archive]

1Kurgan1

09-25-2009, 09:05 AM

Yeah, I know, I just fixed a 95 Grand Am with the 3.1L and a 4 speed. That sucker will MOVE, almost as quick as my old N* cadillac.

The Grand Am's with a 3.1L are the MPFI, the Luminas are the SFI, the MPFI is a much more powerful motor. The SFI motors are truely crap, they blow headgaskets about once a week. My parents went through 5 motors on their 95 lumina before finally sending it to the junkyard.

I'm not sure if they are based on the same block, if they are the whole topend must be diff. But I don't think they are. The 3.1L MPFI is pretty much the improved version of the older 2.8L MPFI that came in Fiero's and some other cars, so it's meant to be a bit sporty, I think it has about 175hp, where as the SFI at least ones before 1999 are 155hp v6. Then they get bumped to 170hp, but really are still pretty doggy. I have a friend with a 20001 Malibu with one and my old 2.2L 5speed 155hp Accord would beat it pretty easily.

JC316

09-25-2009, 07:45 PM

The Grand Am's with a 3.1L are the MPFI, the Luminas are the SFI, the MPFI is a much more powerful motor. The SFI motors are truely crap, they blow headgaskets about once a week. My parents went through 5 motors on their 95 lumina before finally sending it to the junkyard.

I'm not sure if they are based on the same block, if they are the whole topend must be diff. But I don't think they are. The 3.1L MPFI is pretty much the improved version of the older 2.8L MPFI that came in Fiero's and some other cars, so it's meant to be a bit sporty, I think it has about 175hp, where as the SFI at least ones before 1999 are 155hp v6. Then they get bumped to 170hp, but really are still pretty doggy. I have a friend with a 20001 Malibu with one and my old 2.2L 5speed 155hp Accord would beat it pretty easily.

Nope, my Grand Am has the 155HP version. I think you are thinking of the 3.4L that showed up in the 99+ Grand Am's. At any rate, it's probably not the head gasket that blows, it's the intake gasket. They have an insanely high failure rate and are almost as bad to replace as the headgasket.

1Kurgan1

09-25-2009, 10:06 PM

Nope, my Grand Am has the 155HP version. I think you are thinking of the 3.4L that showed up in the 99+ Grand Am's. At any rate, it's probably not the head gasket that blows, it's the intake gasket. They have an insanely high failure rate and are almost as bad to replace as the headgasket.

Yeah those intake gaskets are high failure rate too, I haven't seen any Grand Am's with the 3.1L SFI though, here's a pic of the 3.1L MPFI (looks exactly like the 2.8's did)

http://carphotos.cardomain.com/ride_images/3/2666/4701/31664850006_large.jpg

Those 3.4's that came in Grand Am's later was actually just a bored out 3.1L which started out at like 170hp and eventually made it to around 190hp once they bumped the basic 3.1L power they had to make the power gap follow.

I guess though I could see the basic 3.1L SFI moving ok in a Grand Am being a smaller car, but a guy that I worked with at McD's :( when I was in high school had a 03 Kia Safia and I race him with my moms Lumina from like 30mph and he beat me :( Not badly, but still, when he bought that car it was literally Kia's cheapest car on the lot, and Kia's cheapest car thats not good.

3991v

09-25-2009, 11:22 PM

The Grand Am's with a 3.1L are the MPFI, the Luminas are the SFI, the MPFI is a much more powerful motor. The SFI motors are truely crap, they blow headgaskets about once a week. My parents went through 5 motors on their 95 lumina before finally sending it to the junkyard.

I'm not sure if they are based on the same block, if they are the whole topend must be diff. But I don't think they are. The 3.1L MPFI is pretty much the improved version of the older 2.8L MPFI that came in Fiero's and some other cars, so it's meant to be a bit sporty, I think it has about 175hp, where as the SFI at least ones before 1999 are 155hp v6. Then they get bumped to 170hp, but really are still pretty doggy. I have a friend with a 20001 Malibu with one and my old 2.2L 5speed 155hp Accord would beat it pretty easily.

That was a generation III motor, which would explain all of the problems it's had. My motor is a Generation II. http://en.wikipedia.org/wiki/GM_60-Degree_V6_engine#LH0

And it says the Generation II motor was from 1990 to 1994 on the Lumina's, which would explain all the problems you've have had with it.

JC316

09-25-2009, 11:32 PM

Here is the motor that is in mine and every other Grand Am that I saw in the pick U pull.

http://www.nationsautoelectric.com/images/P1010022_1_.jpg

3991v

09-25-2009, 11:52 PM

I'll get a pic or two of my lumina's motor :)

1Kurgan1

09-26-2009, 01:18 AM

That was a generation III motor, which would explain all of the problems it's had. My motor is a Generation II. http://en.wikipedia.org/wiki/GM_60-Degree_V6_engine#LH0

And it says the Generation II motor was from 1990 to 1994 on the Lumina's, which would explain all the problems you've have had with it.

Yeah I was gonna mention that also, I know yours was't the bad generation, I know a few people with early 90's models that were rock solid, still gutless though :p

And JC your picture makes me jealous, I wish I could walk into a JY and find a bunch of rust free cars :( They don't have pick and pulls up here because it would be almost pointless :/

3991v

09-26-2009, 01:37 AM

JC316

09-26-2009, 01:44 AM

Yeah I was gonna mention that also, I know yours was't the bad generation, I know a few people with early 90's models that were rock solid, still gutless though :p

And JC your picture makes me jealous, I wish I could walk into a JY and find a bunch of rust free cars :( They don't have pick and pulls up here because it would be almost pointless :/

That isn't my picture, mine is cleaner lol. Oh yeah, there are about 15 pick U pulls around me, each being over 75 acres of pure, rust free cars. Dirt cheap too, I can get a long block for $200, not matter if it came out of a Taurus or a Porsche. I just wish I could find one that has a freaking Mustang in it so I can snag some parts for my GT.

Wile E

09-26-2009, 07:50 AM

Yeah, 3.1's are OK. I had a 95 Beretta with a 3100 in it. It was OKish. I'd rather have a 3800 in it tho. lol.

3991v

09-26-2009, 08:17 AM

Yeah, 3.1's are OK. I had a 95 Beretta with a 3100 in it. It was OKish. I'd rather have a 3800 in it tho. lol.

Who wouldn't :p

I mean, for a first car(ish) and a mom's go-to-work and grocery getter, a 3.1 is plenty enough

1Kurgan1

09-26-2009, 09:36 AM

That isn't my picture, mine is cleaner lol. Oh yeah, there are about 15 pick U pulls around me, each being over 75 acres of pure, rust free cars. Dirt cheap too, I can get a long block for $200, not matter if it came out of a Taurus or a Porsche. I just wish I could find one that has a freaking Mustang in it so I can snag some parts for my GT.

Antagonizing me, our JY's are full of rusty crap cars and the old cars get rotated out as they just become too rotted. Can't find 1st gen Taurus's in any JY anymore, even though they were made till 91. :(

Some day I will have to get a trailer and come down to pick and pulls and just pull crap for a whole week.

JC316

09-26-2009, 08:01 PM

Antagonizing me, our JY's are full of rusty crap cars and the old cars get rotated out as they just become too rotted. Can't find 1st gen Taurus's in any JY anymore, even though they were made till 91. :(

Some day I will have to get a trailer and come down to pick and pulls and just pull crap for a whole week.

Damn, that sucks man. I would go crazy and broke without a good junkyard to get my stuff.

Steevo

09-27-2009, 02:06 AM

1Kurgan1

09-27-2009, 08:43 AM

I blow the shit out of every 3.8 I met in my olds. But the cross over intake means you really have to port it good to get your flow without huge turbulance and flow restriction problems, adn the olds is the only one without the stupid air intake heater, and a straight shot intake.

You beat 3800's with a 3100? Are they in reverse?

Steevo

09-27-2009, 04:42 PM

Nope, I just did a good job of porting and some otehr mods to my 3.1

1Kurgan1

09-28-2009, 02:06 AM

Nope, I just did a good job of porting and some otehr mods to my 3.1

Is your 3.1 the SFI or the MPFI? I have never seen a SFI modded as it seems kind of pointless. Still I am curious what you have done or why you modded it.

Wile E

09-28-2009, 05:39 AM

1Kurgan1

09-28-2009, 11:14 AM

Pointless argument. Let me port and mod a 3800, then make a run. Point is, the 3800 is a better platform all around.

Totally agree, but ti's still puzzling, the 3100 has a pretty larger performance gap to cover to match a 3100. Home brewed porting and such just isn't going to cut it, going to take some bolt on goodness, and there really isnt that much out there for the 3100, so I'm just lost on how he would make up that gap.

But I'm wondering if we'll see whats done to it, if I remember right, he's gone 150mphish in a car that would have a very hard time doing it, but never told us the secrets.

newtekie1

09-28-2009, 07:05 PM

I prefer the 3400 in my 2002 Grand Am GT. Or better yet the 3800 in my Monte Carlo.

I blow the shit out of every 3.8 I met in my olds. But the cross over intake means you really have to port it good to get your flow without huge turbulance and flow restriction problems, adn the olds is the only one without the stupid air intake heater, and a straight shot intake.

Hmmm...something tells me you might struggle against one with a SuperCharger...

Steevo

09-28-2009, 07:40 PM

yeah, a supercharger would win. But the ability of a 3.1 with good porting, some resistor mods to lie to the EMU and a less restrictive exhaust is nothign to laugh at. I just wish the slushbox was a bit more workable.

A 3400 is a 3100 with a bit bigger bore, the 3800 was in friends monte and another has a bonneville, by the time I reached 60 they were two car lengths behind and still falling. The porting makes a huge difference on flow at hgier RPM as the crossover intake is made to improve high end power, and still maintain low end torque with long intake tubes, it is just unfortunate the rough casting they left in place and up to 3/8" offsets was so restrictive between the upper and lower plenum and tubes.

I know of a guy who ran 50, 100, 150 and then a open 1/8 tube of NOS into a 3.1 to kill it. And then it only died as the transmission failed and caused the motor to blow apart.

Wile E

09-28-2009, 08:07 PM

That guy was lucky. For every amazing survival story you come up with, someone will come up with a story to show how unreliable they are, and how their 50k mi, perfectly maintained 3.1, blew up for no good reason. Extremes do not account for the majority.

And transmissions dying don't cause engines to blow apart. The only way that's possible is if the engine over-revved by the car going suddenly into what amounts to neutral. That shouldn't happen tho, as the computer would cut it off before it revved to catastrophic rpms. No, the engine was already about gone if that happened.

Resistor mods on the 3.1 do not give it huge hp increases. Maybe a couple, and even then, it's only conditional. The exhaust does help a good bit if you put on headers (or ported manifolds at minimum) on them, and a high flow cat. Cat backs don't give huge increases by themselves, as the rest of the exhaust is the bottleneck, but they certainly help a little.

But still, throw the same mods on a 3.8, and you lose quite easily.

So, comparing your modded 3.1l to a stock 3.8l is just pointless and silly. Not to mention, we don't even know the condition of your friends' cars for the comparison. Comparing a well maintained 3.1 to a beat on 3.8, without even considering your mods is also pointless.

newtekie1

09-28-2009, 10:14 PM

One of the problems is that the Monte Carlo and Bonneville are heavy ass cars, probably a lot heavier than your Oldsmobile with the 3100.

I've got an Impala with a 3400 in it, and it is a completely dog. I hate driving it! My Grand Am GT with the 3400 in it is quick as hell though. Same motor, but drastically different weights.

Saddly, my Monte weights just as much as the Impala, but with a much more powerful engine behind it, it is a lot quicker, especially from a standing start. :D

And I can attest to the 3100's poor headgasket issues. I had a '95 Lumina with the 3100, and the headgasket went after 65,000 miles.

1Kurgan1

09-29-2009, 03:28 AM

Resistor mods really do crap, it's a horrible trick to pull on your motor and will cause it to run rich, could even cause a loss in power like those horrible tornado intakes. I am still really doubting porting of the exhaust is going to make a 3100 run even remotely close to a 3800, with ported manifolds it might pick up 10hp, but thats still putting out very little power.

3100's bone stock are mid 16 second cars (running in good condition) where as a good running 3800 is a mid 15 second capable car, porting exhaust manifolds really shouldn't make up that distance.

Steevo

09-29-2009, 05:48 AM

A resistor mod causes it to run LEAN or closer to stoichiometric as the engien is forced to run rich while at WOT as the only sensors providing feedback are the MAP, and MAF. Addign a few ohms of resistance to each (can't remeber what) causes the engine to think LESS air is coming in, and thus injects less fuel giving a cleaner and hotter burn.

While cruising the MAP and oxygen sensors do the tuning work, the MAF is ignored, and the EGR valve is used to help control combustion temps, that is unless while you were close to the tube a pair of pliers accidentally crushed the tube, thus preventing any vacum from pulling exhaust gas into the intake. Adn during WOT there are no exhaust gasses being pulled in.

So you have a better burn, and a cleaner burn, just a bit more temp, and as far as head gaskets. I have had mine for 130K miles and had no issues other than the occasional hiccup and wear parts. I use high quality products, like a nitrate additive to protect metals from galvanic and cavitation damage, water wetter to help move heat, a lower temp thermostat to prevent the heat from being a problem in the first place, and much else.

That guy was lucky. For every amazing survival story you come up with, someone will come up with a story to show how unreliable they are, and how their 50k mi, perfectly maintained 3.1, blew up for no good reason. Extremes do not account for the majority.

And transmissions dying don't cause engines to blow apart. The only way that's possible is if the engine over-revved by the car going suddenly into what amounts to neutral. That shouldn't happen tho, as the computer would cut it off before it revved to catastrophic rpms. No, the engine was already about gone if that happened.

Resistor mods on the 3.1 do not give it huge hp increases. Maybe a couple, and even then, it's only conditional. The exhaust does help a good bit if you put on headers (or ported manifolds at minimum) on them, and a high flow cat. Cat backs don't give huge increases by themselves, as the rest of the exhaust is the bottleneck, but they certainly help a little.

But still, throw the same mods on a 3.8, and you lose quite easily.

So, comparing your modded 3.1l to a stock 3.8l is just pointless and silly. Not to mention, we don't even know the condition of your friends' cars for the comparison. Comparing a well maintained 3.1 to a beat on 3.8, without even considering your mods is also pointless.

He already had a new firmware flashed to his EMU to overide the rev limiter, he was trying to low the motor as he had a built 3.4 waiting to go in. the transmission sun gear shattered and that was that for the engine, being fed a 1/8" stream of dry NOS at WOT and under full load, it was quick.

The weakest point on all these cars is the sun gear in the transmissino, my ex has hers go out while pulling eisenhower in her pontiac. New transmission was teh fix.

1Kurgan1

09-29-2009, 06:59 AM

Actually the resistor fools the car into thinking it's colder than it actually is which advances the timing which causes it to feed more fuel, making it run rich at all times, not lean. Either way its good for little to no power (maybe 5hp), and porting is good for most likely less than 10, I'm just saying I still don't see a 3.1L walking a 3800, 2 cars to 60 is a pretty hard walk considering that the 3800's has about 50hp more than a 3100 and you've maybe picked up we'll say 20hp (thats giving you the benefit, probably more like 15). Also porting out your exhaust manifolds and not changing out the U-Bend in the exhaust isn't going to accomplish much as that U-Bend is really just a cork, that that would cut back down on the porting gains.

Wile E

09-29-2009, 07:09 AM

Yeah, despite what the resistor mods claim to do, they offer little to no real improvement Steevo, especially under WOT where a race occurs.

It would be the first thing a reputable performance shop does if it actually worked as intended. But they don't, because it doesn't. Only fly-by-night places try to pawn it off as a real mod.

Steevo

09-30-2009, 07:13 PM

JC316

09-30-2009, 07:45 PM

And I can attest to the 3100's poor headgasket issues. I had a '95 Lumina with the 3100, and the headgasket went after 65,000 miles.

Again, were you sure that it was the HG? The intake gasket can directly mimic the head gasket on those motors. You get massive amounts of water in the oil and it if blew just right, water can get on top of the valves and into the cylinders. On top of that, if you weren't looking for it, it's easily missed and is a must replace part when changing the HG.

niko084

09-30-2009, 09:20 PM

BOOST it... 3.1's take quite a bit of boost, just watch the intakes, well known for popping on the 3.0-3.1-3.4-3.8.

I am waiting to find out if I am keeping my '02 Grand Am GT 3.4 right now or if my friend is buying it off me, if not I am going to get the heads ported, intake ported, and drop a super on it.

Wile E

09-30-2009, 10:51 PM

resistor mods don't work on new O2 sensors, yes they heat, but the old valve style they do work on, and by tuning the percent that you lie is the same as a resistor that you put in a pigguback controlelr, or the same as readjusting injector pulse based off a leaner mix.

I can argue this all day as I do wiring, I understand wiring, I like wiring.

Give me a fluke and a assortment of pins, wires and connectors and I feel at home with large bluprints, CAN systems, serial, analog.

last fall I broke a CAN system in two, inserted a dominant controller, hacked some firware with a hex editor to correct some conflicting addresses, and everything works.Yeah, and I modified, hacked, built and generally worked on and diagnosed cars for a living for the better part of my life, and I'm telling you from first hand experience, resistor mods on the 3.1 don't accomplish anything worthwhile at all, and only under very certain circumstances, WOT not being one of them.

You can attempt to argue till you are blue in the face, but dynos and the track don't lie. Resistors mods don't work worth a shit.

Furthermore, I'm am just flat out pulling the BS flag on you claiming to have self-hacked a CAN bus, assuming you are referring to a can bus controlled car. And if you aren't talking about a can bus controlled car, wtf does that have anything to do with the effectiveness of resistor mods on the 3.1?

First you did 150mph in a 7A powered Celi without mention of mods to help your credibility, then you tell me your resistor mods made a big difference in your 3.1, then you tell me you self hacked a CAN bus. Assuming the CAN part is involving a car, I'm sorry Steevo, but you have lost all vehicular credibility with me until you clarify a bunch of stuff. Until then, you are full of it.

Steevo

10-01-2009, 12:08 AM

I work as a Precision Guidance Specialist, I took a CAN bus on Ag equipment, broke it in two, added the second CAN attachment into the harness, added a terminator to the end of the second CAN bus, hacked the displays firmware with a HEX editor to change the arrangement of CAN addresses, re-flashed it, and got everything communicating. Took me 16 hours to get it done. But it saved a $200K+ sale, and impressed the hell out of a customer.

My celi has been tuned by my wife and her ex before we met, CAI, better exhaust, light weight rims, removed all excess weight including trading out seats for corbeau's, and on a cool day on a flat plains road I managed to hit the 147MPH speed limiter, check your figures for the RPM a engine can turn as the tach doesn't lie. It doesn't shut off fuel till 7500 RPM, and yes the top end is weak on it still, it just can't flow enough.

I'm not saying the resistor mods did alot, but the porting and lower restriction exhaust, as well as throwing out the spare and other stuff helped my Olds perform better, the lighter weight rims helped a bunch too. No I haven't dynoed either, and the celi needs to be rebuilt now that my brother in law fucked up the clutch I put in. I plan on tearing it down and putting forced induction, water injection, and a better piggyback engine management on it.

I usually don't feel the need to prove what I say, as I don't lie, don't feel the need to. If you don't believe me it is OK, your approval is not something I need. I have posted pics of the Celi, and have done alot of research. I know wiring, use Deutsch wiring components all the time, have a few thousand dollars of kits for wiring available to and have bastardised harnesses to make what I want to work, work. i understand wiring doesn't make alot of sense to really good mechanics, alot of our mechanics have problems reading harness blueprints for diagnostics, so they usually come get me.

Wile E

10-01-2009, 01:02 AM

I have no problems rewiring an entire car. It makes sense to me just fine. Hex editing, not so much, but schematics aren't generally a problem. I've wired quite a few universal (read: not plug and play) ECU's in my time, and tuned them.

And the Celi still wont do 147 with those mods. Your speedo is way the hell off, you are still sandbagging, grossly miscalculating, or are flat out lying. With those mods, you are looking at 130HP at best. For top speed, weight matters little. All that matters is aero, rolling resistance, gearing and power. The horsepower those mods make on that engine is not enough to pull that car thru the air at 147mph, unless you are on one mean downhill.

To put it into perspective, a bone stock 2000 Celica GTS is more aerodynamic and has a minimum of 50hp more with better gearing than your Celi, and it can't do 147 on the same 3 mile stretch we took the Vette.

Sorry Steevo, it just didn't do 147. It may have indicated it, but it did not do it. And while tachs may not lie, slipping clutches cause less speed per rpm. ;)

As far as porting, I never ported a 3.1, so I don't dispute it makes a power difference. I am claiming that a 3.8 with the same mods will mop the floor with you.

1Kurgan1

10-01-2009, 01:08 AM

CAI, exhaust, tune on that weak of a motor isn't going to be good for much power, also shouldn't even need a tune, the weight cut isn't going to help that much with top end as the car just sin't going to have the power to fight wind resistance. And revving the crap out of a gutless car isn't going to do much good, with those minimal power mods you power will start dropping way way down in the upper RPM's and it would do a lot more good to shift into the next gear and continue back where your power range is. Now you get that FI on there and we'd be talking, but to be realistic, I think that on a stock block hitting even 200 flywheel hp on that motor would be a stretch. 15PSI is atmospheric pressure and should be close to doubling your power. And with that motor that would me between 240 - 270hp with what you have done to it, and I'm doubting that motor can take 15PSI for too long right from the factory.

Also not saying the resistor or the exhaust porting, or even tossing out some weight didn't help. But the the 3800 is a far more powerful motor, the hp mods aren't good for much power, and a spare tire and maybe a bit of sound deadening + trunk liner won't be good for much weight loss, maybe back seat + pass seat then we'd be talking. And even then that I wouldn't see as 2 cars to 60, thats a real good lead. Also not sure if your using an achieva or a cutlass supreme.

I really hate to call out, but neither of those things are really possible. I mean my old accord bone stock should have more power than your celica and I don't feel that any amount of weight reduction would have helped that hit 150mph unless like Wile E said, it was thrown off a cliff.

Steevo

10-01-2009, 01:51 AM

You are both so right.

Wile E

10-01-2009, 02:02 AM

You are both so right.

Thanks, we know.

1Kurgan1

10-01-2009, 05:01 AM

lol

niko084

10-01-2009, 05:43 PM

We talking about resistor mods on the IAT?

All that's going to do is well nothing, there are other checks in your system to be balance your air/fuel mixture, they are called o2 sensors :P

Steevo

10-05-2009, 09:29 PM

We talking about resistor mods on the IAT?

All that's going to do is well nothing, there are other checks in your system to be balance your air/fuel mixture, they are called o2 sensors :P

No, on the mass air flow sensor, the kind with flap valves, and on the manifold absolute pressure sensor, the two used by the ECU to determine correct fueling during WOT as the O2 sensors are narrow band and are only used during partial throttle events.

So far we have collectively decided that using a resistor to either add or subtract voltage to show less air entering the engine during a WOT event will cause nothing to be done, or very little. However using a variable resistor and a laptop to determine to what event you alter the input the ECU sees the story is very different.

I know lots of idiots have tried and failed to use IAT sensor mods, and ues, in the long run the temp, o2 sensor, knock, IAT, MAP, and MAF all play a part in the fuleing, ignition, and many other processes, but during a WOT event the engine relies only on coolant temp, MAP, MAF, IAT, and knock sensor to determine ignition, fueling, and shift. so for a moderate 5% reduction in MAF and MAP pressure decrease the engine will inject a marginal less amount of fuel, in doing so it will check the knock sensor, engine temp, and determine if the engine is running within specs, if it weren't it would throw a fault, since the sensors are manufactured within a certain spec, there will always be variance, so it doesn't "learn" anything besides what set of fuel, ignition, and shift tables to use out of the predetermined sets, and then looks at the sensors to adjust fuel and ignition trim based of calculations that are predefined.

The instructions clearly state that for a OBDII system you should accelerate at WOT from a standing stop and achieve at least 60MPH for the ECU to choose the correct set of management tables for the current climate. That is why some people notice a marginal improvement when they disconnect ehe ECU fuse, the weather might have changed and the barometric pressure has probably changed since the last choice of tables was made. However the rest of the feelings are crap, cruising at 75 down the interstate the engine is relying on the o2 sensors more than anythign else for a proper engine tuining, and also the reason why you can disconnect a o2 sensor and drive around town with no engine faults untill you maintain engine load and speed for a certain length of time.

But hey, what do I know.

Wile E

10-05-2009, 11:41 PM

No, on the mass air flow sensor, the kind with flap valves, and on the manifold absolute pressure sensor, the two used by the ECU to determine correct fueling during WOT as the O2 sensors are narrow band and are only used during partial throttle events.

So far we have collectively decided that using a resistor to either add or subtract voltage to show less air entering the engine during a WOT event will cause nothing to be done, or very little. However using a variable resistor and a laptop to determine to what event you alter the input the ECU sees the story is very different.

I know lots of idiots have tried and failed to use IAT sensor mods, and ues, in the long run the temp, o2 sensor, knock, IAT, MAP, and MAF all play a part in the fuleing, ignition, and many other processes, but during a WOT event the engine relies only on coolant temp, MAP, MAF, IAT, and knock sensor to determine ignition, fueling, and shift. so for a moderate 5% reduction in MAF and MAP pressure decrease the engine will inject a marginal less amount of fuel, in doing so it will check the knock sensor, engine temp, and determine if the engine is running within specs, if it weren't it would throw a fault, since the sensors are manufactured within a certain spec, there will always be variance, so it doesn't "learn" anything besides what set of fuel, ignition, and shift tables to use out of the predetermined sets, and then looks at the sensors to adjust fuel and ignition trim based of calculations that are predefined.

The instructions clearly state that for a OBDII system you should accelerate at WOT from a standing stop and achieve at least 60MPH for the ECU to choose the correct set of management tables for the current climate. That is why some people notice a marginal improvement when they disconnect ehe ECU fuse, the weather might have changed and the barometric pressure has probably changed since the last choice of tables was made. However the rest of the feelings are crap, cruising at 75 down the interstate the engine is relying on the o2 sensors more than anythign else for a proper engine tuining, and also the reason why you can disconnect a o2 sensor and drive around town with no engine faults untill you maintain engine load and speed for a certain length of time.

But hey, what do I know.Yep. You fined tuned the fuel. Great. Still only worth a couple HP on a mostly stock car. It's the same principle as adding a chip or reflashing a stock ecm, only with a lot less control and benefits. Adjusting fuel pressure on a return style car or adjusting the timing have the same effects. Tho porting may have added a little. At best, you are still only equal to a well maintained stock 3.8.

Steevo

10-06-2009, 04:23 AM

Yep. You fined tuned the fuel. Great. Still only worth a couple HP on a mostly stock car. It's the same principle as adding a chip or reflashing a stock ecm, only with a lot less control and benefits. Adjusting fuel pressure on a return style car or adjusting the timing have the same effects. Tho porting may have added a little. At best, you are still only equal to a well maintained stock 3.8.

That was all I wanted, with the laptop hooked up we coudl adjust the timing, fuel, and shifts. These motors really thrive with better timing and high RPM. Don't think the tranny would last too long with a 7000 RPM shift though.