Can you over throttlebody a efi motor
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Joined: Dec 2004
Posts: 2,636
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Originally Posted by ls1408cp
Can you over throttlebody a efi motor? I sometimes hear you cant but wanted to hear what others thought.
Yes, if the TB is bigger than the MAF it will slow air flow down and cause the intake charge velocity to be lower/lose power.
If both MAF and TB are oversized, the velocity may be low enough to cause errant MAF readings.
TECH Addict
Joined: Dec 2004
Posts: 2,178
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From: Florida
Originally Posted by ls1408cp
Can you over throttlebody a efi motor? I sometimes hear you cant but wanted to hear what others thought.
check it: http://www.yellowbullet.com/forum/sh...ad.php?t=16031
TECH Apprentice
Joined: Oct 2004
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Yes its possible.
But the car will still operate.
Too big a carb on a reeally small motor, and the car will not really run at low rpm, possible stumbles and cutting out. It will clear up at high rpm.
And this is an extreme example, say a Dominator on a 260CI motor.
On EFI it is possible to have too large a TB. A TB larger than the entrance to the maniFold will result in less Flow thru the maniFold, so it is possible that a too large TB will result in LESS POWER.
Also too big a TB will make tip in and transition painFul, IE where you need to blip the throttle just For a couple more hundred rpm, you lose your "resolution" over the gas pedal.
The car will still run however, and make good power.
Rules on the TB, enough TB + 20% For your power level, and not bigger than the entrance into the maniFold.
But the car will still operate.
Too big a carb on a reeally small motor, and the car will not really run at low rpm, possible stumbles and cutting out. It will clear up at high rpm.
And this is an extreme example, say a Dominator on a 260CI motor.
On EFI it is possible to have too large a TB. A TB larger than the entrance to the maniFold will result in less Flow thru the maniFold, so it is possible that a too large TB will result in LESS POWER.
Also too big a TB will make tip in and transition painFul, IE where you need to blip the throttle just For a couple more hundred rpm, you lose your "resolution" over the gas pedal.
The car will still run however, and make good power.
Rules on the TB, enough TB + 20% For your power level, and not bigger than the entrance into the maniFold.
I also do not run an IAC and have no problems with it. The reason for me unpluging mine was when staging the idle would try to drop as the IAC closed thinking it was idling to high and also hurt consistency. It has ran that way for 2 years and the only time I had Idle problems is when its cold but all I have to do is hold the gas alittle untill it warms up. This is a track only car though with no AC but does have PS and waterpump.
I thought about this but never did it:
http://modernmusclecars.net/forums/articles.php?do=emic
I thought about this but never did it:
http://modernmusclecars.net/forums/articles.php?do=emic
Where do people get some of this stuff? We are running a 1700 cfm throttlebody (little more than 105mm single blade comparable) wayy "too much" for the motor and it does not hurt power, idles good, with a stock PCM.
No such thing in terms of torque output as too much TB on EFI. Period. Maybe if you had a 10,000 cfm TB but I dont think we have to worry about that
No such thing in terms of torque output as too much TB on EFI. Period. Maybe if you had a 10,000 cfm TB but I dont think we have to worry about that
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Originally Posted by ls1408cp
this is why I am going 2000cfm plus. I cant decide to buy the fast or the accufab
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
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From: Texas
You aren't looking for carb signal, so that isn't an issue like it would be in a carb application. The only issue you will see is drivability issues. Witha TB that flows that much air, even a small incremental opening is a huge ammount of airflow based on the effective area of the throttle plate.
So, without some sort of progressive linkage, the act of cracking the throttle would be "jerky" at best. This is the same issue you see on ITBs with TB's that are too large.
Now, the only other consideration is that too much volume will slow down velocity. Its the same for ports in your cylinder head. Yes, it flows X ammount, but at Y volume does that help or hurt you? You are feeding a shared plenum, so it may not be as big an issue, but may be something to keep in mind.
So, without some sort of progressive linkage, the act of cracking the throttle would be "jerky" at best. This is the same issue you see on ITBs with TB's that are too large.
Now, the only other consideration is that too much volume will slow down velocity. Its the same for ports in your cylinder head. Yes, it flows X ammount, but at Y volume does that help or hurt you? You are feeding a shared plenum, so it may not be as big an issue, but may be something to keep in mind.
TECH Junkie
Joined: Dec 2005
Posts: 3,092
Likes: 11
J-Rod raises and interesting point. That is the velocity of the air from the air filter to the plenum. I have seen it mentioned a couple of times but nothing on the subject.
This may be something the high dollar race car guys do. Are there harmonics involved like the 1st, 2nd, 3rd and 4th waves on tuned intake runners? Can you get a supercharging effect?
My thought has been to try and eleminate any restictions from the air filter to the plenum so that at WOT a 100 KPA or more can be maintained. If you have a 94KPA at WOT you know there is a problem with the air supply such as to small od an air filter.
That is why I run as big an air filter as I can fit, a 3 1/2" intake pipe, 58mm twin throttle body, one 90 degree turn in the pipe and as short as posible to reach the cold air.
By the way when I was on the dyno I did not lose any horsepower with the air filter off. In fact I may have lost a couple with just the open pipe.
This may be something the high dollar race car guys do. Are there harmonics involved like the 1st, 2nd, 3rd and 4th waves on tuned intake runners? Can you get a supercharging effect?
My thought has been to try and eleminate any restictions from the air filter to the plenum so that at WOT a 100 KPA or more can be maintained. If you have a 94KPA at WOT you know there is a problem with the air supply such as to small od an air filter.
That is why I run as big an air filter as I can fit, a 3 1/2" intake pipe, 58mm twin throttle body, one 90 degree turn in the pipe and as short as posible to reach the cold air.
By the way when I was on the dyno I did not lose any horsepower with the air filter off. In fact I may have lost a couple with just the open pipe.
Originally Posted by kickassT/A
anyone have a dominator flanged 4 bbl tb on their car? been concidering this. sry for the hijack
Originally Posted by J-Rod
You aren't looking for carb signal, so that isn't an issue like it would be in a carb application. The only issue you will see is drivability issues. Witha TB that flows that much air, even a small incremental opening is a huge ammount of airflow based on the effective area of the throttle plate.
So, without some sort of progressive linkage, the act of cracking the throttle would be "jerky" at best. This is the same issue you see on ITBs with TB's that are too large.
Now, the only other consideration is that too much volume will slow down velocity. Its the same for ports in your cylinder head. Yes, it flows X ammount, but at Y volume does that help or hurt you? You are feeding a shared plenum, so it may not be as big an issue, but may be something to keep in mind.
So, without some sort of progressive linkage, the act of cracking the throttle would be "jerky" at best. This is the same issue you see on ITBs with TB's that are too large.
Now, the only other consideration is that too much volume will slow down velocity. Its the same for ports in your cylinder head. Yes, it flows X ammount, but at Y volume does that help or hurt you? You are feeding a shared plenum, so it may not be as big an issue, but may be something to keep in mind.
really the hole are not much bigger than an lt1 hole so only opening 2 of them makes it drive pretty good. 