ihatemyxa

ive heard some people speak about how adding H/I/E onto an untuned scion a/b/d/tc will actually slow the car down in some ranges and possibly effect gas mileage because 'the tune from the factory leaves no room for changes without negative effects'

anyone have any input on this? im thinking of doing H/I on my xa...

IH8ONYU

How can you "tune" a Naturally Aspirated 1nzfe? doesn't the vvt-i want to cancel that? I would like to know this as well. w/o turbo or super charger / injectors, what is there to tune?

ihatemyxa

a/f ratio disrupted by adding things like intake and header. you slap on a bigger header, more air flowing, a bigger intake more air flowing in, colder, how does the car make up for it in fuel?

jct

answer is no it doesn't rob you of any power it free's up the power with freer flowing air flow get the right set up and you'll improve your mpg

but for me i also improved my emission and throttle responce

Metro273

The O2 sensors do this job. The ecm monitors what the O2s "see" and make adjustments to compensate for the more air going past the air intake sensor, thus "dumping" more fuel to equal the amount of air coming in.
There is actually a technical term for this process...Stoichiometric ratio!
Here is more info...

http://en.wikipedia.org/wiki/Air-fuel_ratio

evosky

i think you're thinking in terms of good versus bad.
when you do a tune or any modifications to a car, you are doing some sort of compromise, no matter what it is.
OEM tunes a car to fit into a specific range of acceptable performance, mileage, safety, reliability, etc ... Thus, this is usually thought of as the "optimal" tune depending on the rules and regulations of the market and what the company is trying to market the car as.

so, when you do modifications, of course it will have a "negative" effect on the car, but that's in compromise for something. you kick up performance, you'll lose something in another area. it's all a balance.

no worries dude. just mod your car. do what you want. it's not gonna poop out and explode.

mb2008

If certain things are done to the car (none come to mind) it will have a negative effect, but for the most part you do nothing bad. Think about it. Motors are "de tuned" from factories to meet emission standards and whatnot and also to make them less efficient. For example, look at the horrible intake that comes with your car, It curves all over the place restricting airflow then it has that horrible "accordion" shape at the end creating a turbulent airflow instead of a nice smooth flow though an injen, afe, so on and so on, intake.

Take Jeep for example, there was a diesel version of the Liberty that sold in Canada that got great gas mileage but was not offered in the U.S because of this. Another example, the Subaru Imprezza Sti, it actually got around 330 or 350 HP but had to be taken down to about 300 to meet emission standards here.

There's a person that has a shop near where I live, he builds performance cars as his career. His Porsche is around 1000 HP. Guess what his gas mileage is, you'd think it would be bad, but it's actually in the 20's. When asked if he designed them for mileage he said no, only power, but when your going for power you have to make the motor more efficient to get all the power out of it.

Oh, try to explain this one to me. The single cab chevy s-10 weighs over 4000 lbs, so why did they only put a 120 Hp motor in it? Hmmmmmmm. Perhaps to purposely make it have bad gas mileage.

joshsbox

I noticed a 3-4mpg gain after I/H/E...just my .02

cobb

Liked mentioned above is true. 2 reasons you would get poorer fuel economy or performance is that you got the wrong part and it decreases performance vs increase. Second reason is that you drive it harder therefore burn more fuel than before vs using the free-ed up power from your parts.

Second worry would be life of the drivetrain. When I had my 240d benz everyone cautioned me about modding it. They said the 54hp engine would go a million miles in its oem configuration.It was 27 years old and had over 470 thousand miles on it and lacked acceleration for a 4 thousand pound car.

I did the fuel injector mod and kn filter. I got it to smoke like most diesels do, increased the acceleration/power and could squeal tires from a dead stop in first gear only. This car was sooo underpowered it couldnt even squeal tires if you dumped the clutch in first gear. Needless to say a few months later it started to get harder and harder to start. Sure it was old to start with, used and well rusted. Maybe I put it to an early death, but it was difficult to get up to highway speeds in 3 miles with you foot on the floor of the gas petal.

I have the estended warranty on my scion, so no powertrain mod til 2013 or 75 thousand miles, which ever comes first.

cobb

Man, I didnt mean to be a buzz kill, hey whats that cricket sound?

So, what E I H gives more fuel economy? I hear mixed results regarding the kn model and the toy one too.

Thanks

ihatemyxa

thanks for the info!

evosky

i personally have IHE+P, and it works for me. i dont really remember what a completely stock xb drives like since i got mine used with the OEM options already on it.

all i can say is, the pulley will make a big difference.

cobb

No pulley mod here. Ive seen too many big blocks in my shop class that the crank was busted from a broken haromance balancers, not to mention lack of one at all. Yeah, a small pulley with the haromoncic balancer I can see doing since these little cars idle at 500 or so, then cruise at 3 grand.

evosky

the harmonic balancing is not a function of the pulleys in our NFZ's so doing a lightened pulley (not underdrive mind you) is not going to be detrimental at all. it will just act as lightened rotational mass and allow the engine to hit the revs faster. i've had mine for 2 years no problems, and people on here have some for 4+ no problems. all comes down to preference i guess.

cobb

Lightened not smaller? Id want a smaller one. Withthe ac on full blast, lights, fogs and radio it takes a few seconds to break idle speed to get moving. Big difference from driving with just the key on during the day and windows cracked.

evosky

the smaller pulley kits traditionally aren't advised or used for the NFZs unless you go with a stronger battery. again, it's all personal preference, though i have always been warned that underdrive is to be avoided.

mb2008

Why would you want to avoid it?

evosky

when you're underdriving, you're making more revolutions to get to the same speed or whatever your engine will be spinning at, so you need to draw more power. thus you need a bigger battery to compensate for the powertrain and possible power loss that you will experience for your electronics. also, the smaller pulleys have a greater risk of throwing off the balance of the engine since again the rotational circumference is less than the OEM.
In reality, a lot of people still do underdrive kits but don't know the consequences of what it means and don't compensate appropriately for it.

cobb

Most underdrive kits have larger pulleys for the accessories and smaller one for the crank. This way everything spins at the same speed, but the engine has less work to do to spin up from idle speed. Did I get it backwards?

evosky

you might be right. i'm not too familiar with underdrive pulleys. i just know that they require a larger power draw from the electrical system, and thus an upgraded battery is usually recommended with it or else you might damage the engine without proper checks and maintenance.