*** Update 90mm TB + 48% Effective table
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From: Port Tobacco, MD
*** Update 90mm TB + 48% Effective table Its been almost 2 weeks now since I changed the effective table by 48% I derived from some calculations and the idle hits and sticks like a carb car. Idle on my 232/238 110 110 is simply amazing.
Phil
Phil
Idle is a much more difficult animal on big cam'd autos. M6s don't idle in gear (generally). 
I haven't touched that table. Why do you think it made a difference? What is the 'effective area' that it's showing.
I haven't touched that table. Why do you think it made a difference? What is the 'effective area' that it's showing.
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From jfpilla's " Idle Thread"
Thread -> http://www.efilive.com/forum/viewtop...t=1169&start=0
For 90 mm TB move the Effective Area table values 6 places towards the
higher values and leave the IAP values stock.
higher values and leave the IAP values stock.
OK,
Let me make sure I got this....
I need to multiply my Effective area table x .48 because the area of the TB is greater?
If this works, I'll kiss you guys. Well... maybe not.
TIA,
Andy
Let me make sure I got this....
I need to multiply my Effective area table x .48 because the area of the TB is greater?
If this works, I'll kiss you guys. Well... maybe not.
TIA,
Andy
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Phil does this matter if you have a Nick Williams 90mm TB or a LG G2 90mm TB?
Sorry if a bunch of us are really slow on this, but you definetely are shining light on a good topic.
So this table is showing the the IAC Steps, and you are multiplying the entire table by 48%. That means your highest value is 149 (on a c5 vette) What is the top numbers reference to, where it goes from 0 to 120. I know the table is Desired Idle Effective Area, but what doe that mean? How much the blade is opening? Im lost on this part as well as probably others are. Dont hate me
Dixit
Sorry if a bunch of us are really slow on this, but you definetely are shining light on a good topic.
So this table is showing the the IAC Steps, and you are multiplying the entire table by 48%. That means your highest value is 149 (on a c5 vette) What is the top numbers reference to, where it goes from 0 to 120. I know the table is Desired Idle Effective Area, but what doe that mean? How much the blade is opening? Im lost on this part as well as probably others are. Dont hate me
Dixit
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Originally Posted by 02sierraz71_5.3
100*.48=48 thats a reduction of 52 percent
multiply by .52 for 48 percent reduction
multiply by .52 for 48 percent reduction
Thread Starter
7 Second Club
iTrader: (11)
Joined: Jul 2002
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From: Port Tobacco, MD
I made a spreadsheet that calculated airflow for the 75mm Throttle Body and 90 Throttle Body. 48% is not related to airflow, it is the percentage of step that the 90mm uses to mimic the 75mm Area. So.....
Hypothetically
IF a 75mm TB @ 40 steps has 1 cu/inch of area
Than
a 90mm TB would need 19.2 steps to have the same 1 cubic inch of area
So you need to....
Multiply the 40 steps by .48 to get 19.2
40 x .48 = 19.2
There is alot more to the calculation but this is the jist. Rather than using steps since the step is going to be linear and equally sized, I used 0 to 90degrees and calculated area based on .25 degree. Calculated area when open - area closed to find total area gained, divided that by my 360 steps(360 - 1/4 or .25 degree increments) to find total area for each 1/4 degree of throttle movement. I used that to make a chart to map area of the 75mm TB as the butterfly opens from 0 to 90 degrees or WOT. I made another chart based on the area as it gained and reversed solved the 90mm TB to find the required step to mimic the exact area that the 75 shows. The steps were 48% less in each calculation. So reguardless of what unit that the ECU uses this calculates the same thing.
__________________________________________________ _____
Actual Data**
Stock **
The effective area table is confusing. If you look at it, the ECU says I need 128 area units I need to open the TB up to 17 steps.
Move 6 step right method **
By moving the table 6 places to the right as suggested with a larger TB it now says...
If I need 40 area units I now need to open the TB up 80 steps.
My Calculated Method***
If I need 40 area units I need to open up the TB 61 steps
Hypothetically
IF a 75mm TB @ 40 steps has 1 cu/inch of area
Than
a 90mm TB would need 19.2 steps to have the same 1 cubic inch of area
So you need to....
Multiply the 40 steps by .48 to get 19.2
40 x .48 = 19.2
There is alot more to the calculation but this is the jist. Rather than using steps since the step is going to be linear and equally sized, I used 0 to 90degrees and calculated area based on .25 degree. Calculated area when open - area closed to find total area gained, divided that by my 360 steps(360 - 1/4 or .25 degree increments) to find total area for each 1/4 degree of throttle movement. I used that to make a chart to map area of the 75mm TB as the butterfly opens from 0 to 90 degrees or WOT. I made another chart based on the area as it gained and reversed solved the 90mm TB to find the required step to mimic the exact area that the 75 shows. The steps were 48% less in each calculation. So reguardless of what unit that the ECU uses this calculates the same thing.
__________________________________________________ _____
Actual Data**
Stock **
The effective area table is confusing. If you look at it, the ECU says I need 128 area units I need to open the TB up to 17 steps.
Move 6 step right method **
By moving the table 6 places to the right as suggested with a larger TB it now says...
If I need 40 area units I now need to open the TB up 80 steps.
My Calculated Method***
If I need 40 area units I need to open up the TB 61 steps
its in efi live also....i just sent him an email from my car...an 01 trans am because i was wondering if i need to change my table. My car is controlled by cable...not the computer...so i was wondering if i even needed to do this.
OKAY.
This is a father and son build and my dad knows far more than me in this case with this stuff. We do need to change my table and i will see how things run after i do what Phillip has said to do..and let yall know. My dad says he is going to sit down and work up a formula because he wants to play around with it now, lol. Anyways, thanks for the info on this Phillip, I know a lot of people are going to be looking at this..Nick W. has more and more TB's that he has to make day after day.
OKAY.
This is a father and son build and my dad knows far more than me in this case with this stuff. We do need to change my table and i will see how things run after i do what Phillip has said to do..and let yall know. My dad says he is going to sit down and work up a formula because he wants to play around with it now, lol. Anyways, thanks for the info on this Phillip, I know a lot of people are going to be looking at this..Nick W. has more and more TB's that he has to make day after day.
Last edited by ZL1Killa; Jun 12, 2005 at 09:49 PM.
Originally Posted by Ragtop 99
Does this table exist in EDIT or just through HPT?
Phil, we just used your calc on my friends C5 w/ AFR 205's 224/228 XER, Fast LSX90, & LS2 TB. We also added 2 degrees of timing at idle in the corresponding base spark tables, and the car idles like stock. We were idling at 850rpm's and took it down to 775rpm. Still like stock. Thank for the good work 
Originally Posted by Phil99vette
I made a spreadsheet that calculated airflow for the 75mm Throttle Body and 90 Throttle Body. 48% is not related to airflow, it is the percentage of step that the 90mm uses to mimic the 75mm Area. So.....
Hypothetically
IF a 75mm TB @ 40 steps has 1 cu/inch of area
Than
a 90mm TB would need 19.2 steps to have the same 1 cubic inch of area
So you need to....
Multiply the 40 steps by .48 to get 19.2
40 x .48 = 19.2
There is alot more to the calculation but this is the jist. Rather than using steps since the step is going to be linear and equally sized, I used 0 to 90degrees and calculated area based on .25 degree. Calculated area when open - area closed to find total area gained, divided that by my 360 steps(360 - 1/4 or .25 degree increments) to find total area for each 1/4 degree of throttle movement. I used that to make a chart to map area of the 75mm TB as the butterfly opens from 0 to 90 degrees or WOT. I made another chart based on the area as it gained and reversed solved the 90mm TB to find the required step to mimic the exact area that the 75 shows. The steps were 48% less in each calculation. So reguardless of what unit that the ECU uses this calculates the same thing.
__________________________________________________ _____
Actual Data**
Stock **
The effective area table is confusing. If you look at it, the ECU says I need 128 area units I need to open the TB up to 17 steps.
Move 6 step right method **
By moving the table 6 places to the right as suggested with a larger TB it now says...
If I need 40 area units I now need to open the TB up 80 steps.
My Calculated Method***
If I need 40 area units I need to open up the TB 61 steps
Hypothetically
IF a 75mm TB @ 40 steps has 1 cu/inch of area
Than
a 90mm TB would need 19.2 steps to have the same 1 cubic inch of area
So you need to....
Multiply the 40 steps by .48 to get 19.2
40 x .48 = 19.2
There is alot more to the calculation but this is the jist. Rather than using steps since the step is going to be linear and equally sized, I used 0 to 90degrees and calculated area based on .25 degree. Calculated area when open - area closed to find total area gained, divided that by my 360 steps(360 - 1/4 or .25 degree increments) to find total area for each 1/4 degree of throttle movement. I used that to make a chart to map area of the 75mm TB as the butterfly opens from 0 to 90 degrees or WOT. I made another chart based on the area as it gained and reversed solved the 90mm TB to find the required step to mimic the exact area that the 75 shows. The steps were 48% less in each calculation. So reguardless of what unit that the ECU uses this calculates the same thing.
__________________________________________________ _____
Actual Data**
Stock **
The effective area table is confusing. If you look at it, the ECU says I need 128 area units I need to open the TB up to 17 steps.
Move 6 step right method **
By moving the table 6 places to the right as suggested with a larger TB it now says...
If I need 40 area units I now need to open the TB up 80 steps.
My Calculated Method***
If I need 40 area units I need to open up the TB 61 steps
I'm confused......Did you multiply your whole table by 48% or did you move the whole table to the right a number of cells but not the 6 stated by someone else?
you have to watch it though, that could help on a hot idle (not saying it wont work anywhere else or that its a bad idea, i think its great) but if you scale it and your tb doesnt have the same flow, or similar to stock (like mine with a ported and epoxied tb) then you will need to rebuild the whole table, not just scale it. i rebuilt mine and it has no stalling, sputtering, cutting otu problems...althoguh im still working on some ve and raf numbers. my MAX area is now set to 62 i believe. anything above that is flat because the small copper tube in the tb. phil was having troubles with my process so i dont know if its a 90mm tb problem or if its a vette tb problem, but ive got a cable tb.
either way its done, this wil really help out the car it idle and cruising, it will help to prevent some surging and hanging up in the rpms, or dipping too low when comming to a stop. glad to hear this worked out for you phil
either way its done, this wil really help out the car it idle and cruising, it will help to prevent some surging and hanging up in the rpms, or dipping too low when comming to a stop. glad to hear this worked out for you phil