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Discussion Starter · #1 ·
Do we actually have anyone here that has done any performance mods to their theta? If so lets see what you have done.
 

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Im going to do a DIY CAI but that is about it.

Warranty is too valuable to go screwing around with it anymore than that.
 

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bballr4567 said:
Im going to do a DIY CAI but that is about it.

Warranty is too valuable to go screwing around with it anymore than that.
Yeah, voiding the warranty isn't worth gaining a little better acceleration. I might go with a lower restriction exhaust system before the warranty is up...if I can find one that doesn't make the 4cyl sound like a riceboy racer.
 

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Discussion Starter · #4 ·
I was thinking of making a ram air into the factory air box, with a drop in k&n filter and punching out the MAF. Then crossing my fingers and hoping that it makes a little difference. Then down the road possibly put a magnaflow muffler under her.
 

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kupiheab said:
I was thinking of making a ram air into the factory air box, with a drop in k&n filter and punching out the MAF. Then crossing my fingers and hoping that it makes a little difference. Then down the road possibly put a magnaflow muffler under her.
Intake and exhaust should be done at the same time for performance gains.
That's what we did in the old days and theoretically I don't see how anything's changed.
I mean if you're going to stuff more air into the combustion chamber but can't exhaust it fast enough, you're developing back pressure, which isn't going to accomplish anything except maybe confuse the ECM, right?
 

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Discussion Starter · #6 ·
You will gain a little just opening up the intake but not your full potential. It will just take me a minute to talk the wife into doing the exhaust.
 

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gearhead said:
Intake and exhaust should be done at the same time for performance gains.
That's what we did in the old days and theoretically I don't see how anything's changed.
I mean if you're going to stuff more air into the combustion chamber but can't exhaust it fast enough, you're developing back pressure, which isn't going to accomplish anything except maybe confuse the ECM, right?
the same time!?!? lol....it doesnt matter....modern computer adjust almost instantly.....
 

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I've tuned my I4 a little bit, little stuff like turning off brake torque management when the TCS is off and some delivered torque changes nothing major YET.
 

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gar187er said:
the same time!?!? lol....it doesnt matter....modern computer adjust almost instantly.....
Hmmm, learn something everyday.
Still don't understand how stuffing more air into the intake will increase performance (unless it's cooled a bit...maybe yes).
kupiheab mentions "punching out the MAF", the Mass Air Flow, sensor.

What effect that has on the ECM, I don't know.
All I'm saying is an engine is like an air pump, if you don't have the capacity to exhaust it fast enough, what's the point of trying to stuff more air into it as there's no where for the extra air to accumulate.
You'd simple be compressing it somewhat.

When I was a street rodder, it was common knowledge (proven on the dyno) that you weren't going to gain much power by increasing airflow in unless you open the exhaust at the same time as well.
 

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Discussion Starter · #10 ·
That is correct. You do need to open the flow on both ends but you will gain some power just opening one side just not the peak power. Only reason I am waiting on the exhaust is b/c I have to talk to the wife about it.
 

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kupiheab said:
That is correct. You do need to open the flow on both ends but you will gain some power just opening one side just not the peak power. Only reason I am waiting on the exhaust is b/c I have to talk to the wife about it.[/color]
Tell her you need it so you can drive her to the jewelery store faster!
;D 8)
 

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With my CAI on my G8, I gained .6 and 3 MPH in the 1/4 mile with no change to the exhaust.

Sure, I could of gained more had I put on high flow cats but didnt and still gained a good amount of power.

These days factory exhaust systems arent that bad. The most restrictive part is the cats. IIRC from climbing under the Terrain, the I4 has 2 1/4" exhaust piping. That itself should be pretty good for a lot of power.
 

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gearhead said:
Hmmm, learn something everyday.
Still don't understand how stuffing more air into the intake will increase performance (unless it's cooled a bit...maybe yes).
kupiheab mentions "punching out the MAF", the Mass Air Flow, sensor.

What effect that has on the ECM, I don't know.
All I'm saying is an engine is like an air pump, if you don't have the capacity to exhaust it fast enough, what's the point of trying to stuff more air into it as there's no where for the extra air to accumulate.
You'd simple be compressing it somewhat.

When I was a street rodder, it was common knowledge (proven on the dyno) that you weren't going to gain much power by increasing airflow in unless you open the exhaust at the same time as well.
more air=more fuel too.....thats the reasoning....your not just putting more air in and running lean, the computer compensates for it, by upping the fuel mix...

i removed the honeycomb in the MAF area of the intake....useless restriction...like a piece of metal or wood is gonna go through the air filter and make it to the TB....lol

but most MAF's are fairly thick in the support brackets not to mention the sensor itself....jet makes an upgraded MAF for the 1st gens....



much better design...worth money?!? not untill my maf takes a dumb.... :)

and i get what saying about back in the days doing both at the same time, which would eb easier, cause your not gonna want to retune (timing, mixtures, etc) twice....better to do it all at one time...but now days, all thats computer controlled for the most part (timing you can still change on certain engines), so its doesnt matter what order you do things...

:)
 

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gar187er said:
more air=more fuel too.....thats the reasoning....your not just putting more air in and running lean, the computer compensates for it, by upping the fuel mix...

i removed the honeycomb in the MAF area of the intake....useless restriction...like a piece of metal or wood is gonna go through the air filter and make it to the TB....lol

but most MAF's are fairly thick in the support brackets not to mention the sensor itself....jet makes an upgraded MAF for the 1st gens....



much better design...worth money?!? not untill my maf takes a dumb.... :)

and i get what saying about back in the days doing both at the same time, which would eb easier, cause your not gonna want to retune (timing, mixtures, etc) twice....better to do it all at one time...but now days, all thats computer controlled for the most part (timing you can still change on certain engines), so its doesnt matter what order you do things...

:)
I understand 100% what you're saying...but.
All you're doing is burning more fuel.
The basic principle behind an internal combustion engine hasn't changed in 100 years...to get more power, you have to be able to exhaust the extra air and fuel detonated in the combustion chamber more quickly, e.g. a bigger exhaust port, cat convertor, resonator, muffler, tailpipes etc., etc., etc.
That's my story and I'm sticking to it LOL!
 

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If the thetas are tuned like the g8 they will run better with more air. The g8 tune is so rich the cai leans it out enough to get almost the perfect mixture.
 

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The main gain is the replacement of the air baffles and the air filter box. Those are basically designed to STOP the sound of air, IE; slow it down, so the engine is basically starving for air.

Id like to see someone get them on the dyno and see what they actually run A:F wise.
 
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