would i see any increase from a bigger throttle body yet? according to my mods?

 

I don't think you would if you did it would be small. stock TB flows 650cfm I think some one said its good up to 400hp but I could be wrong

 

From what I've read and learned, data log a wide open throttle run. If you're not getting 95-100 KPa readings at WOT I beleive that means there is still vacuum and a larger TB can be useful. Otherwise, stick with what you've got. Kinda makes sense, but I've not done the testing with different sized TB's to verify this...

 

Basically, what Vern said.

If your getting 95-100kpa readings at WOT u dont have a restriction that is hurting you.

Bigger TB's have more effect than just pure airflow under WOT conditions, there is also more air at all throttle openings and this will have an effect on VE as well as AE.

later
Jeremy

 

thanks

 

A better comparison (more universal) would be WOT 3000 RPM vs WOT 5000 RPM MAP values. a 3 kPa drop there would be acceptable. Might want to compare with and without an air filter there too, just to get some more data.

 

guys not for nothing but i have a hsr and bbk 58mm tb. i had the stock tb on it and the guy who does my tune (yes mail order thru datalogging ) he says that the bigger tb shouldnt have any effect on the tune. is this true.

 

another thing with the bbk 58mm, after i installed it the car is starting to pop thru the intake. is this from running the bigger tb with all the mods that i have done and not changing anything in the bin

 

yes. its true. the ECM is measuring the amount of air going in. it doesnt look it up by TPS

the only thing that MAY be effected is the "pump shot" that is made from a lookup table based on TPS change.. but short of going from stock to a HUGE monoblade or anything of that nature, it probly should not be changed.

if it was running fine beforehand, its more likely that something else besids the bin is to blame

 

Bigger TB's have a direct effect on AE fueling and some on the VE.

A lot more air moves into the TB when the size is increased and this can and does make for needed changes in the bin to accoutn for this, if one wants to do it the right way.

Ask people who switched from a TPI to a Stealthram and do their own tuning, they all needed to add AE. Lot less runner equaled a lot more air sooner.

This is a example of what I mean and it is extreme when comparing different intake setups.

The same premise holds true when just using throttle bodies to do the same thing, just on a smaller scale obvioulsy.

Use a wideband and do some testing and it shows up quite easily.

The 48 to 52 mm swap isnt the one that causes the bigger concerns either(usually a waste of $$ on a asotck motor), its usually when someone goes from 48 to 58 they see more issues.

Twin 48 should be fine thru the 400hp range or so and head for the 52 after that. Serious combos need the dual 58 or mono TB's in my own opinion.

I'm sure someone will argue or start a flame, again, I dont care, just passing on what I have learned and observed firsthand

later
Jeremy

 

 

throttlebodies only have that effect when they become the primary restriction of the intake tract.

normally, the intake and heads are the primary restrictions...

true, if you put a steathram on a high hp car,
tune it for the steathram with the tiny stocker TB

then put a huge one on so theres zero restriction

then, it will effect VE.

but thats because you changed the restriction

 

IAC following issues also are apparent and will need to be adjusted. Some surge, off idle leaning, and stalling could also work into the mix because of the IAC reactions. Its all part of the game
You will most definatly need to tweak the AE to account for the increased air from the old settings. A 52 replacing a 48 may not need much but could be changed to make everything nice, but from 48 to 58 will need some work done.
I'll be knee deep into these issues here shortly. I only went 52mm to keep myself sane while my combo keeps increasing.

 

Someone want to email me what part of the AE to change when going to a HSR and a bigger TB? Make it short and sweet, I should be able to take it from there. Also, is a WB needed to accurately do this?

tcarlson41@comcast.net

Thanks
-Brad

 

From the PROM Burning Guide
https://www.thirdgen.org/techbb2/sho...hreadid=195745