Rebel 3" intake = loss of power with a GM stock tune?
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From: Canada, Quebec
Rebel 3" intake = loss of power with a GM stock tune?
Hello people!
You will certainly see my other tread just below this one or not too far, it talks about my car not beeing as much powerfull as I thought vs my friend with a stock car with an INJEN intake. Please look at my post if you want more information: https://www.cobaltss.net/forums/2-0l-lsj-performance-tech-47/cti-race-header-downpipe-installed-but-no-gain-all-178736/
My goal here is to open the eyes of people who want to purchase a 3" intake such as the Rebel Auto Worx one or the Fujita and who want to stay with a GM tune such as "stock" or stage 2.
If you read my other tread, you will know that I just get one car in front of my friend's one which is not normal at all. Briefly, I had GM stage2, 3" intake and my friend, stock with an Injen intake. Tennpenn83 came up with a great thought in that tread and I would like to show that part of the tread for you:
"i'd be willing to bet that most of the problem has to do with the intake. especially with you having the 3" intake, your maf tables are probably so far off that it made you lose enough power to have a stock car hang with you. Put it this way. the redline's K&N typhoon CAI is actually 2.75", while the stock is 3", at least at the maf sensor (i have no idea if this is the same on the cobalts). when you decrease the diameter of the tubing, and you don't change the tune, it ends up flowing more air at higher velocity but the frequency (in Hz) still shows the same airflow as the old tune. so, the computer doesn't think there's that much air flowing so it injects the same amount of fuel. when in actuality, theere is more airflow, and the same amount of fuel, so you'd run leaner, and that's where the power is made. (plus the whole K&Nfilterlessrestrictionetc...)"
What I would like is that if some people have a 3" intake and a stock tune (Gm stock or Gm stage 2), please give your comments about this and if you can prove the above statement wrong, do it. For example if you dynoed your car before and after with the 3" intake and that it gave you a GAIN, please tell it. Or if you did a race against a friend with similar mods to you for example gm stage 2 with an Injen intake and gm stage 2 with a 3" intake tell us the outcome.
If the above statement is true in practice, this would be a great informational tread for any people looking for a 3" intake. Because theoretically, what Tennpenn83 said seems rock solid to me!
Thanx for your comments
You will certainly see my other tread just below this one or not too far, it talks about my car not beeing as much powerfull as I thought vs my friend with a stock car with an INJEN intake. Please look at my post if you want more information: https://www.cobaltss.net/forums/2-0l-lsj-performance-tech-47/cti-race-header-downpipe-installed-but-no-gain-all-178736/
My goal here is to open the eyes of people who want to purchase a 3" intake such as the Rebel Auto Worx one or the Fujita and who want to stay with a GM tune such as "stock" or stage 2.
If you read my other tread, you will know that I just get one car in front of my friend's one which is not normal at all. Briefly, I had GM stage2, 3" intake and my friend, stock with an Injen intake. Tennpenn83 came up with a great thought in that tread and I would like to show that part of the tread for you:
"i'd be willing to bet that most of the problem has to do with the intake. especially with you having the 3" intake, your maf tables are probably so far off that it made you lose enough power to have a stock car hang with you. Put it this way. the redline's K&N typhoon CAI is actually 2.75", while the stock is 3", at least at the maf sensor (i have no idea if this is the same on the cobalts). when you decrease the diameter of the tubing, and you don't change the tune, it ends up flowing more air at higher velocity but the frequency (in Hz) still shows the same airflow as the old tune. so, the computer doesn't think there's that much air flowing so it injects the same amount of fuel. when in actuality, theere is more airflow, and the same amount of fuel, so you'd run leaner, and that's where the power is made. (plus the whole K&Nfilterlessrestrictionetc...)"
What I would like is that if some people have a 3" intake and a stock tune (Gm stock or Gm stage 2), please give your comments about this and if you can prove the above statement wrong, do it. For example if you dynoed your car before and after with the 3" intake and that it gave you a GAIN, please tell it. Or if you did a race against a friend with similar mods to you for example gm stage 2 with an Injen intake and gm stage 2 with a 3" intake tell us the outcome.
If the above statement is true in practice, this would be a great informational tread for any people looking for a 3" intake. Because theoretically, what Tennpenn83 said seems rock solid to me!
Thanx for your comments
Thread Starter
Member
Joined: 08-25-07
Posts: 307
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From: Canada, Quebec
It's certainly not my downpipe because I raced my friend before I used it and I had similar results. So with only the GM Stage 2 and the RAW intake. My car feels great also with the RAW intake, it feels powerfull with that whine when I'm alone but against my friend its another story and I see the truth!!!
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Joined: 08-25-07
Posts: 307
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From: Canada, Quebec
But we know that most people with GM tunes GAIN horsepower with an aftermarket intake. I said most because those with a 3" intake like me, I'm not sure anymore. As soon as you change the diameter of the tube (vs stock), this changes how the air flows through the MAF sensor.
If I'm not mistaken,
Injen intake vs stock one: same diameter with a better filter = better air flow, better air velocity
R.A.W. intake vs stock one: bigger diameter with a better filter = better air flow, worse air velocity than with the Injen, so maybe at some point worse than the stock intake.
Now... does the MAF sensor cares about the velocity of air? This is a "Mass air flow" sensor... wow I'm not even sure anymore about the statement provided by Tennpenn83.
So if the MAF measure air flow, then even if the air velocity is changed it will not matter? I begin to be confused 
If I'm not mistaken,
Injen intake vs stock one: same diameter with a better filter = better air flow, better air velocity
R.A.W. intake vs stock one: bigger diameter with a better filter = better air flow, worse air velocity than with the Injen, so maybe at some point worse than the stock intake.
Now... does the MAF sensor cares about the velocity of air? This is a "Mass air flow" sensor... wow I'm not even sure anymore about the statement provided by Tennpenn83.
i'd be willing to bet that most of the problem has to do with the intake. especially with you having the 3" intake, your maf tables are probably so far off that it made you lose enough power to have a stock car hang with you
put it this way. the redline's K&N typhoon CAI is actually 2.75", while the stock is 3", at least at the maf sensor (i have no idea if this is the same on the cobalts). when you decrease the diameter of the tubing, and you don't change the tune, it ends up flowing more air at higher velocity but the frequency (in Hz) still shows the same airflow as the old tune. so, the computer doesn't think there's that much air flowing so it injects the same amount of fuel. when in actuality, theere is more airflow, and the same amount of fuel, so you'd run leaner, and that's where the power is made. (plus the whole K&Nfilterlessrestrictionetc...)"
put it this way. the redline's K&N typhoon CAI is actually 2.75", while the stock is 3", at least at the maf sensor (i have no idea if this is the same on the cobalts). when you decrease the diameter of the tubing, and you don't change the tune, it ends up flowing more air at higher velocity but the frequency (in Hz) still shows the same airflow as the old tune. so, the computer doesn't think there's that much air flowing so it injects the same amount of fuel. when in actuality, theere is more airflow, and the same amount of fuel, so you'd run leaner, and that's where the power is made. (plus the whole K&Nfilterlessrestrictionetc...)"
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Joined: 08-25-07
Posts: 307
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From: Canada, Quebec
I will get it with the new ottp stage kit Im gonna receive but I'm so STUBBORN I really want to understand why a car with a GM Stage 2 + 3" intake cannot pull better than that against a stock car and Injen intake! 
Normally Im not the kind of guy who wants to understand everything but that situation I live with that car and that lack of performance, I'm really hung to that and I wanna understand why!
Normally Im not the kind of guy who wants to understand everything but that situation I live with that car and that lack of performance, I'm really hung to that and I wanna understand why!
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Joined: 03-07-08
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From: TNARMS
disconnect battery cables for 15 minutes
put them back on, start and let your car run for at least 5 minutes without touching the gas pedal
your car will "re-learn" the proper air/fuel mix for the new amount of air it is now receiving.
put them back on, start and let your car run for at least 5 minutes without touching the gas pedal
your car will "re-learn" the proper air/fuel mix for the new amount of air it is now receiving.
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From: Far from you
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From: NEPA
It's certainly not my downpipe because I raced my friend before I used it and I had similar results. So with only the GM Stage 2 and the RAW intake. My car feels great also with the RAW intake, it feels powerfull with that whine when I'm alone but against my friend its another story and I see the truth!!!
you are confused why a stage 2 car with a 3" intake doesnt pull a stock car with an injen .... well my stage 2+ car pulls very hard and i have raced a few stock ss/sc's with just intakes or exhaust mods and have beat them pretty good. my raw intake works great on my car. i lost no power and gained some mid-upper range power over my aem intake i used to have. maybe your stage 2 tune is f'd up. i kno they revised them many times since they came out in 2006. maybe look into getting flashed again. or do what others have said switch cars and race. maybe its driver mod. keep us posted.
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Joined: 08-25-07
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From: Canada, Quebec
i dont care what you say that cti downpipe is garbage .... terrible design, but if you like it keep it. i lost a lot of low-mid range power with that downpipe.
you are confused why a stage 2 car with a 3" intake doesnt pull a stock car with an injen .... well my stage 2+ car pulls very hard and i have raced a few stock ss/sc's with just intakes or exhaust mods and have beat them pretty good. my raw intake works great on my car. i lost no power and gained some mid-upper range power over my aem intake i used to have. maybe your stage 2 tune is f'd up. i kno they revised them many times since they came out in 2006. maybe look into getting flashed again. or do what others have said switch cars and race. maybe its driver mod. keep us posted.
you are confused why a stage 2 car with a 3" intake doesnt pull a stock car with an injen .... well my stage 2+ car pulls very hard and i have raced a few stock ss/sc's with just intakes or exhaust mods and have beat them pretty good. my raw intake works great on my car. i lost no power and gained some mid-upper range power over my aem intake i used to have. maybe your stage 2 tune is f'd up. i kno they revised them many times since they came out in 2006. maybe look into getting flashed again. or do what others have said switch cars and race. maybe its driver mod. keep us posted.
At the same time, wow, I didn't see often someone disliking CTI products, but yeah, myself when I looked at the quality of the header and the downpipe, I was a bit disapointed...
Last edited by firepinch; Jul 7, 2009 at 05:55 PM. Reason: Automerged Doublepost
For months I ran GM Stage 2 with a Rebel 3" intake and never lost to any other stock-intake stage 2 cars, much less a stock SS with an injen. Racing on the street isn't the best benchmark though.
I believe there are too many factors in play to speculate on the intake being the problem, but ultimately I think putting the stock hardware back on (like damien suggested) would be the only way to find the concrete evidence you're looking for.
I believe there are too many factors in play to speculate on the intake being the problem, but ultimately I think putting the stock hardware back on (like damien suggested) would be the only way to find the concrete evidence you're looking for.
I will get it with the new ottp stage kit Im gonna receive but I'm so STUBBORN I really want to understand why a car with a GM Stage 2 + 3" intake cannot pull better than that against a stock car and Injen intake!
Normally Im not the kind of guy who wants to understand everything but that situation I live with that car and that lack of performance, I'm really hung to that and I wanna understand why!
Normally Im not the kind of guy who wants to understand everything but that situation I live with that car and that lack of performance, I'm really hung to that and I wanna understand why!
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Joined: 08-25-07
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From: Canada, Quebec
I have to add something I TOTALLY forgot! This MAY be a cause of my problem: I have a check engine light since a good 4-5 days that makes me remember that at some occasions, I got some check engine lights with the same error code.
The codes I have NOW are P0017 and P0420. But what is important to note is that I had since one year several occasions where the check engine light would come on with the same code: P0017. And this mean "crankshaft sensor position".
So maybe my crankshaft sensor has something but if it could be borked, wouldn't I have always the check engine light on??? Before the actual check engine light, it was off for a good month then it was on during 2-3 days before that month as an example (P0017 code again).
So another possibility: a defective crankshaft sensor which results in poorer performance?
But yes damien, I'd have to try it out, puting back my stock intake. Its just a pita to re-install the Rebel, fitment is a big issue for the 2007 model.
The codes I have NOW are P0017 and P0420. But what is important to note is that I had since one year several occasions where the check engine light would come on with the same code: P0017. And this mean "crankshaft sensor position".
So maybe my crankshaft sensor has something but if it could be borked, wouldn't I have always the check engine light on??? Before the actual check engine light, it was off for a good month then it was on during 2-3 days before that month as an example (P0017 code again).
So another possibility: a defective crankshaft sensor which results in poorer performance?
But yes damien, I'd have to try it out, puting back my stock intake. Its just a pita to re-install the Rebel, fitment is a big issue for the 2007 model.
The light turns on every time the sensor shorts out. Refer to this post, then replace:
https://www.cobaltss.net/forums/problems-service-maintenance-69/crankshaft-position-sensor-car-died-no-start-54807/
https://www.cobaltss.net/forums/problems-service-maintenance-69/crankshaft-position-sensor-car-died-no-start-54807/
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From: Canada, Quebec
Not a bad idea you had Pyros777! However in that tread, the guy talk about the code for CPS failure which is P0335. Mine is P0017 and the code isnt supposed to mean that the problem is electrical related like the P0335 suggest. Anyway, Im gonna talk to the dealer about that to know what they are thinking...
But if I stay on topic, when I think about it, I dont think that this error code really contribute to the loss of performance of my car. I have to try to swap my intake in order to know if my intake is really the problem...
But if I stay on topic, when I think about it, I dont think that this error code really contribute to the loss of performance of my car. I have to try to swap my intake in order to know if my intake is really the problem...
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From: Richmond
But we know that most people with GM tunes GAIN horsepower with an aftermarket intake. I said most because those with a 3" intake like me, I'm not sure anymore. As soon as you change the diameter of the tube (vs stock), this changes how the air flows through the MAF sensor.
If I'm not mistaken,
Injen intake vs stock one: same diameter with a better filter = better air flow, better air velocity
R.A.W. intake vs stock one: bigger diameter with a better filter = better air flow, worse air velocity than with the Injen, so maybe at some point worse than the stock intake.
Now... does the MAF sensor cares about the velocity of air? This is a "Mass air flow" sensor... wow I'm not even sure anymore about the statement provided by Tennpenn83.
So if the MAF measure air flow, then even if the air velocity is changed it will not matter? I begin to be confused
If I'm not mistaken,
Injen intake vs stock one: same diameter with a better filter = better air flow, better air velocity
R.A.W. intake vs stock one: bigger diameter with a better filter = better air flow, worse air velocity than with the Injen, so maybe at some point worse than the stock intake.
Now... does the MAF sensor cares about the velocity of air? This is a "Mass air flow" sensor... wow I'm not even sure anymore about the statement provided by Tennpenn83.
So if the MAF measure air flow, then even if the air velocity is changed it will not matter? I begin to be confused
Intake velocity doesn't mean much when you have a huge vacuum pump in your intake, it matters at the runners.
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