question about lumina Mods

hey guys, I was wondering if any of you have any experience with the common mods for the 3.1 V6 often found on ebay. Like this one?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7964185508

up 15 to 20 horses for rougly 30 bux? Is that just a bunch of bs? What are the risks involved with trying one of these things? any ideas or input would be greatly appreciated, Thanks.

c'mon guys, a little help here?

c'mon guys, a little help here?
check out:
http://www.superchips.com/html/products/gm/other%20GM%20Cars/othergmcars8793.htm
to compare

"The Racing-X Performance Module enhances the performance of your vehicle by receive/modify the signals from the IAT sensor or the MAF sensor"

I'm not convinced. Sounds like what could be achieved by simply putting a resistor of the correct value inline of the sensor harness. That would simply lie to the ECM and cause it to run richer than what it was designed for. Probably wouldn't hurt anything, but I seriously doubt it would have a very noticeable effect on performance.

The real performance dhips are actual reprogramming for the ECM. This sounds like an inline shunt that probably costs them a couple of bucks to make. Have you seen a picture of the actual product?

E-mail them and tell them you want a copy of the install directions, and a picture of the product. I bet they backpedal.

I agree with Jeff. It's a part that costs the company about 50 cents to make. That's all it is is a resistor to fool the ECM like Jeff said - If it sounds too good to be true, then it is.

yeah, thats what I thought. in all actuality, if all that thing is doing is sending more fuel in, it isnt going to do really anything but waste gas. Because it seems as somone told me that these OBDII cars will automatically send more fuel if more air is being sent in, so would it be to my advantage to just buy a better air intake? Any ideas? Thanks. And yes, I did email the seller, and have heard nothing back yet. Who knows. Thanks guys. Any other input?

Because it seems as somone told me that these OBDII cars will automatically send more fuel if more air is being sent in, so would it be to my advantage to just buy a better air intake. Any other input?

Exactly. There is a point where you can have too much flow on one end. Remember, your intake and exhaust flow capabilities have to be more or less matched, or you create an imbalance that's difficult to make use of. At some point exhaust mods, fuel pressure and delivery have to be increased, and programming remapping for the fuel injection and ignition are required. But just opening it up will enhance performance of any motor, long as it is done thoughtfully.

That's why I busted out the holes in my stock airbox with a holesaw. Even with the K+N panel filter, it still sounded like it was gonna turn the box inside out at WOT. I knew it could use more flow. So I put three 1-1/2" holes in it, one out board, one inboard, and one on the bottom, now it breathes better. It's louder too, which is probably part of the reason they make the box so restrictive. Most car owner don't want to hear the motor. They want to not even know it's there.

See, stock engine tuning is always a compromise of four elements. Performance, Economy, Driveability/Idle charactaristics, and Reliability. You can usually figure if you increase one, you will lose some of another. Want a better breathing cam? OK, but you loose some idle smoothness(driveability) and fuel mileage(economy) in trade for better performance. And your other drivetrain parts are gonna go bad sooner with more power put to them (reliability).

Hang a free-breathing exhaust on a stock engine with no intake mods, and you get a motor that is louder, lacking in low-end torque and throttle response (due to loss of backpressure-induced scavenging), and might run slightly better at WOT and high speed, but not worth all the other losses. You need to keep a balance. Open up the intake, gotta open up the exhaust.

I was talking to another guy on a Ford forum, he's having ECM problems cuz he's running a 4" intake with a cone filter on a motor with stock exhaust. Can you say constipation? :rofl: He's probably always out of range on MAF readings and it's driving the computer nuts. The ECM is calibrated with a range of what should be normal flow capability for the size of intake ducting the factory uses. Bigger duct, you can flow more, but velocity and pressure decrease, and the MAF is showing the ECM something it can't make sense of.

wow, yeah, that actully makes sense now. There is a place about 10 miles from where I live that does custom exhaust. I've been toying with the idea to go and get it done to my car. you all laugh because its only a 3.1, I know, but my friend did it to his ford countour, 2.6 V6 I believe, and it sounds awesome, looks sweet, and he says has a noticable amount more power. And the best part is, when everything was done, his total bill was only 150.00. Not bad, huh?

wow, yeah, that actully makes sense now. There is a place about 10 miles from where I live that does custom exhaust. I've been toying with the idea to go and get it done to my car. you all laugh because its only a 3.1, I know, but my friend did it to his ford countour, 2.6 V6 I believe, and it sounds awesome, looks sweet, and he says has a noticable amount more power. And the best part is, when everything was done, his total bill was only 150.00. Not bad, huh?

Yeah, good price for that work. Thing is, most people would rather die than tell you that what they did to their car made it run worse. I don't know about your friend's car, it might run better. I worked with a guy that had a V6 Contour, and he did the same thing, had a custom shop run off the convertors with a larger diameter "collector" pipe, then split to dual 2-1/2" branches with a Dynomax on both sides and 2-3/4" tailpipes.

Sounds great!! Runs like shit. I had driven it before he had this done, and I drove it after. No throttle response, weak until it got over 4500 RPM, and annoying as hell inside the car. Just a deafening drone that seemed to come from everywhere and squeeze your head. On the highway it was almost unbearable. Couldn't even get the stereo loud enough to drown it out. :grinno:

Your friend might not have gone that radical with pipe sizes and muffler choice, that might be why he's happy with it. I'm just saying. The system my boy built for his would be perfect for a motor with a cold air intake, ported manifold and heads, etc. He can't match the flow from the rear with flow up front. Now he's lost all his backpressure and the low end torque and response you get from it. Don't go too radical or you'll be kicking yourself in the ass for years to come. (of course it can be a good way to motivate you to improve the rest of the motor :evillol: )

If all you really want is the look and sound, you can put whatever you want on the BACK of the exhaust system. Put a splitter pipe off the back end of the extension pipe (the one that goes from the cat to the rear) with dual mufflers and resonator tips and it'll sound great and look cool, and run just like it always had. But when you start messing with the point where the two banks of exhaust come together off the motor, you are screwing up exhaust pulse tuning that the manufacturer puts a lot of thought into to make the best use of the way exhaust pulses flow through the pipe.

At lower speed (idle to maybe 2500 RPM) it makes use of the flow velocity to help initiate intake charging. If you increase pipe size, you decrease velocity and pressure. It's called Bernoulli's principle, I think. You can think of it like your garden hose. When the hose is open, you turn the water on and it rolls out lazily. Put a resrictive nozzle on the end, and you get a narrow, high speed jet of water. This is because the same amount of water is going through a smaller point in the hose, so it has to move faster to get it all through. Pressure and velocity increase behind it inside the hose.

Now when one cylinder lets go of an exhaust pulse, the intake valve is just beginning to open. That exhaust is caught up in the high velocity flow from the other cylinders, creating a pressure imbalance (suction) in the cylinder that is just beginning to come on intake stroke. Because of the high velocity flow of the smaller exhaust, the cylinder is evacuated of exhaust very quickly, and there exists an intake-initiating low pressure condition in that cylinder before the intake cycle even begins! This makes the intake flow begin earlier than just the suction action of the piston could achieve, getting the intake charge aligned and beginning to move toward that cylinder as early as possible. Even as the exhaust valve closes, the condition still exists, as air (just like anything else) wants to keep moving once acted upon.

You can visualize this by thinking of a house with the windows at both ends open. If there is a breeze blowing through the house from one end to the other, all the air in the house doesn't stop moving the instant you close the downwind window. It continues moving toward that end, drawing more air in the other window for several seconds until pressure equalizes.

This effect is very important to low-end response and torque characteristics of a motor. If you open the exhaust too large, you loose velocity (the same amount of exhaust now flows through a larger conduit, so it doesn't have to go as fast to do it), and the effect it has on power in the bottom end.

The flip side of this is that most stock exhaust systems are built with noise level at normal street and highway RPMs in mind. So at the other end of the spectrum, WOT, high RPM operation, there is usually a power robbing conditon caused by excessive backpressure in the system. It wasn't designed to flow that much exhaust for any length of time. So the longer you hold the RPMs at this level, the pressure increases in the system until it begins to have a negative effect on intake charging. Power begins to drop off sharply. To the driver, it feels like it has just "hit the wall" and won't give any more.

That point is where the guy who put too big exhaust on his ride will feel a difference. But how much time is spent running at the very top of the RPM range? Unless you race at a track alot, and the last second or two of the race is the critical point where races are won, very little. For a street car it is a hinderance, as most "stop light drags" are decided by quick response and 1/8th mile acceleration rather than top end speed.

Hope this helps clear it up for ya', and helps you make some good decisions about mods.

yes it did. Thank you. My friend didnt mess with the exhaust heads at all. He basically split after the cat, and went to a couple performance mufflers I believe, and then striaght out. It sounds better than stock, but basically is still stock with a little less restrictive airflow.

and yes, that guy emailed me back, and that mod sounds like a bunch of BS. I'm not going to waste my money. Thanks guys for all the useful information.

Jeff "whoa!" - you left my mind partially toasted after your last post. (good info)- how did you figure all that stuff out? You must have a degree in flow dynamics or something. (and I thought I was good with engines...) - you should add "resident genius" to your sig... :thumbsup:

Jeff "whoa!" - you left my mind partially toasted after your last post. (good info)- how did you figure all that stuff out? You must have a degree in flow dynamics or something. (and I thought I was good with engines...) - you should add "resident genius" to your sig... :thumbsup:

Thanks. I wish I'd figured it out myself, but I just read a lot. I've always been interested in how physics plays into engine performance. Don't worry, I'll say something really stupid pretty soon, and things will even out again. :lol:

Thanks. I wish I'd figured it out myself, but I just read a lot. I've always been interested in how physics plays into engine performance. Don't worry, I'll say something really stupid pretty soon, and things will even out again. :lol:

doubtfull