Why would this lean it out?
Why would this lean it out? Im just curious, why would putting a ported tb possibly lean out the mixture. I just had my car tuned and i just now decided to put a tb and i dont really want to pay for a new tune. I understand that the tb will be letting in more air, but wont the MAF sence this and put in more fuel?
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Originally Posted by PG45
Im just curious, why would putting a ported tb possibly lean out the mixture. I just had my car tuned and i just now decided to put a tb and i dont really want to pay for a new tune. I understand that the tb will be letting in more air, but wont the MAF sence this and put in more fuel?
Expl:A 90mm TB with a restricted air induction system is worthless. To benefit from larger TB you have to match the induction system as well as the intake mouth size to fully benefit. Then of course you would benefit from bigger gains with a tune up.
Because the air slows down accross the sensor wires and makes the computer think less air is entering the engine when in actuality more air is entering. This is my understanding I may be worng and if i am someone will correct me
How do i find out if my car is running rich enough to put a tb on safely. It may be that there are no cats but my car smells real bad, so i may have some room to play around.
odd thing is after i ported my throttle body by lookin at my fuel trims, the car richened up. i understand its not suppose to be that way but hey some cars act different to different things
Trending Topics
Anyone have any suggestions on wheather i should get one or not....i mean 130 bucks for 8 rwhp is nothin. i just cant justify it if i have to get another tune and im not one for doin half *** work. If i need to tune it then its tune and tb or no tb at all.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo do it yourslef like i did mine, it came out real nice and i just noticed better throttle response, i dont think u will see 8 hp out of it. every little bit helps but i say do it yourself if your like me and didnt wanna spend the money. now the guys that do it do a great job and its not bad for the work your getting but i did mine cause it was fun too lol
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
Likes: 3
From: Troy, AL
"Ok then why does a ported tb lean out the mixture?"
It doesn't. If you truly have a change in mixture after a TB change/modification then it's because you've caused a vacume leak somehow (your Ltrims should reflect this.) Otherwise, no, a ported TB absolutely WILL NOT effect your fuel/air mixture in the slightest.
It doesn't. If you truly have a change in mixture after a TB change/modification then it's because you've caused a vacume leak somehow (your Ltrims should reflect this.) Otherwise, no, a ported TB absolutely WILL NOT effect your fuel/air mixture in the slightest.
TECH Enthusiast
Joined: Jul 2002
Posts: 618
Likes: 0
From: Pensacola, FL
Originally Posted by HumpinSS
Because the air slows down accross the sensor wires and makes the computer think less air is entering the engine when in actuality more air is entering. This is my understanding I may be worng and if i am someone will correct me
Porting the MAF housing will change A/F.
Porting the TB will not, as it does not meter the air as the MAF does.
Porting the MAF will cause A/F changes for the above reason - they way the MAF calculates airflow is by monitoring changes in temperature/voltage of the MAF internals as the air passes over them.
An extreme example - think of blowing the same amount of air into a drinking straw vs. through a 3" exhaust tube. The air moves quickly through the straw but the exhaust tube would sense very little air movement. A MAF inside the straw would sense a lot of air moving through and add a lot of fuel. A MAF inside the 3" pipe would sense much less air movement, even though the air going into both the straw and the pipe were the same amount initially.
The TB, on the other hand, is after the metering of the air in the path, so any improvement in airflow there will be previously metered by the MAF.
Happy driving,
Bad30th
Porting the TB will not, as it does not meter the air as the MAF does.
Porting the MAF will cause A/F changes for the above reason - they way the MAF calculates airflow is by monitoring changes in temperature/voltage of the MAF internals as the air passes over them.
An extreme example - think of blowing the same amount of air into a drinking straw vs. through a 3" exhaust tube. The air moves quickly through the straw but the exhaust tube would sense very little air movement. A MAF inside the straw would sense a lot of air moving through and add a lot of fuel. A MAF inside the 3" pipe would sense much less air movement, even though the air going into both the straw and the pipe were the same amount initially.
The TB, on the other hand, is after the metering of the air in the path, so any improvement in airflow there will be previously metered by the MAF.
Happy driving,
Bad30th
Sweet, now im not sure if they drilled out my tb to get it to idle better. Should i just send out my tb to be ported or just buy one. porting my own is out of the question (im bound to screw it up...i dont build them, just drive them 
)
) 
yes it makes sense but why would numbers change? my part throttle fuel trims were definately different. i log them a lot and right after the throttle body and long enough after it so the car could learn what happened, the fuel trims changed. i see what you are saying but if the throttle body creates more restriction than the MAF does, then opening the throttle body up more shoudl cause a change in the velocity of the air going through the maf shound it? i dont know maybe im just thinking too hard about nothing but it just trips me out that it shouldnt make a change and on my car it made a noticeable change in the fuel trims, im not talkin about tenths im talkin about 2 or 3 %. can anyone explain this?
TECH Senior Member
Joined: Nov 2001
Posts: 9,246
Likes: 3
From: Troy, AL
2 or 3%? Awww, there's nothing at all unusual about that. You'll notice changes like that (and more) even when no changes are made. Weather plays a big part in Ltrims. Ltrims are almost constantly changing one way or another. Nothing wrong with that.
What are your Ltrims at idle now? And what are they during steady state cruise?
About the MAF, ANY increase in airflow through the TB (and we're ONLY talking about at WOT where this increase could even take place...this is during open loop where no O2 sensor learning is taking place. Therefore no Ltrim changing is takeing place.) will result in a change in the reported load from the MAF. This will correct the mixture. It will NOT, however, change the Ltrims. Ltrims are changed by the Strims. Strims are changed as a result of O2 readings other than stoichiometric. These O2 readings are only recognized for mixture changes during closed loop operation (which WOT is not.)
What are your Ltrims at idle now? And what are they during steady state cruise?
About the MAF, ANY increase in airflow through the TB (and we're ONLY talking about at WOT where this increase could even take place...this is during open loop where no O2 sensor learning is taking place. Therefore no Ltrim changing is takeing place.) will result in a change in the reported load from the MAF. This will correct the mixture. It will NOT, however, change the Ltrims. Ltrims are changed by the Strims. Strims are changed as a result of O2 readings other than stoichiometric. These O2 readings are only recognized for mixture changes during closed loop operation (which WOT is not.)
yeah i know it could change from day to day but the conditions were the same and the car always stayed consistent before at steady cruise and then they changed. im guessing 3% but may be more. i know its not a huge difference BUT i did see them change. idle trims are -10 at idle and -.78 or 0 at part throttle, i had them adjusted back to where they were