Wades SnS

iTrader: (2)

I asked this same question in another section on this forum and haven't gotten a good answer not saying anything negative towards those who replied but i would like a more technical answer. I would like to know if you were to put an intake/tb setup that flows more cfm then what is required for your engine what are the negative affects that will come by doing this if any. The reason i ask is I have a stock bore lsx 383 that now has a stock ls6 inatke and tb but i have a gmpp carb intake that i am considering installing. While looking at the options for tb's I have noticed that accel makes a square hole carb style tb that flows 1550cfm. If I were to purchase this for room for expansion or possibly to keep me from having to buy another tb in the event that i'd go with a bigger cubed engine would I be shooting myself in the foot for now. My current setup is a hyraulic roller big cam good heads all forged setup with true 3" duals and lt's. How hard is this going to be to tune if it is tuneable at all. I am sure that there isn't going to be any low end vacuum seeing as i will be using a single plane and feel it will be even worse with the oversized tb. How will this affect the upper rpm's? Sorry for the long post and thanks in advance for any info.

..RJ..

ShiznityZ28

iTrader: (11)

The general rule is you can't over TB an EFI setup. I run a 4500 flange top mount TB on a VIc jr and my car made 50 more peak hp than a car with a very similar 90/90 setup. These cars are very close in setups. We also recently switched ATV's car from a fast 90/90 to a sheetmetal/90 and he picked up a buncha hp i want to say it was like 30 and the tq was just about unaffected down low.

So for the small amount of testing we have done. no you can't hurt an EFI car with to much intake or TB.

Oh side note the above is as long as the intake ports are matched to the heads if the intae ports are huge and the head port is small you will make a lip that will mess up air flow.

ewingr

I have a stock LS1 (Crate 2004 Corvette motor) that I"ve put in a '56 Chevy. What's not stock is headers; emissions gone.

I am having a shop put a cold air intake on it. Based on room available, it will be a 90 elbo off the TB, over across in front of the Alternator, 90 elbo out the front bulkhead, and will have S&P MAF and Air cleaner on it.

Here's my question: He is thinking he will need to use 3" diameter material. I'm thinking the TB is 4" (I'm not near it to measure).

Assuming the TB is 4" , I'm wondering if feeding it with 3" when the TB is 4" will hurt the HP.

I don't know that I should be too concerned about HP, as I don't plan to race it or anything. But, of course, a person likes to have all they can get when they decide to get heavy with the foot.

What do ya' think?

Wades SnS

iTrader: (2)

That is basically the same setup i have on my s10 only i run mine through the same size pipe as my tb. My problems seem to be the 90 at the tb. that and around 4500rpms i run out of air. as far as drivability there are no issues but you can not tune your ve table correctly above the rpm that you run out of air. With my setup my ve table gets almost flat in the upper rpms.


Shiznity what problems did you run into tuning your setup? Are you running a iac tb if so how did you determine affective area and how hard was the idle tuning? What other things need to be changed when going to a bigger tb?

Thanks,
..RJ..

ewingr

You say you run out of air at 4500....do you realize that from having a computer hooked up while driving, or just by the seat of the pants recognition? In other words, does it sort of fall flat on it's face, just all of a sudden less acceleration, or what?

It would seem to me that if you run out of air using the same size pipe, that I would suffer more. Seems logical, anyway.

DanO

A throttle body is just a "controlable air restriction" and for maximum power, you want the least pressure drop across your throttle as possible during WOT.

The only downside to very large throttles are the very touchy part throttle. i.e. when you only move the throttle blade a little, alot of airflow change is seen... especially right off idle.

The 90mm TB setups seem to be ok in this department... but going 104+mm you should notice it a bit more..

ewingr

Wades

Something else. What specifically do you mean when you say "My problems seem to be the 90 at the tb"?

Also, as I think about this, if your 'pipe' is teh same size as the TB, it would seem to me that issues you are having would not relate to the cold air intake...unless the air traveling through a couple 90 turns would affect it.

ShiznityZ28

iTrader: (11)

I have the one that uses the 3rd gen IAC and the FORD TPS. It idles good but its at like 1100 because of the cam thats in it. At first we had some issues but it was because the upgrade flash of the Alpha-N tune faield and the car would run for 15 seconds then turn off. after we did a total reflash it fixed it. It took jeff like 30 minutes to get the idle and light throttle stuff down the alpha n helps us add fuel by tps. I have the progressive linkage so the car drives like stock bellow 40% throttle but from 41-100 there is very little differance LOL

ShiznityZ28

iTrader: (11)

Thats trhe advantage of the 4 barrel. you can have progressive linkage so it only opens the 2 small blades bellow 40% or so.

Wades SnS

iTrader: (2)

Thanks for all the info
I am running out of air because i have more engine and cam then what my tb/intake will support. I have came to this conclusion with a data logger not by the feel of the engine. What i mean by the 90 before the intake is on my setup there is about 5 inches of space between the front tb edge and the radiator. This is where i placed a 90* elbow and my method for testing to see if it is a restrition was with the data logger i removed my airbox piece by piece and all of its pipe and saw an improvement in airflow. It wasnt a lot but was enough to determine that there was a restriction with the elbow being that close to the tb. my elbow is a stright 90 it does not have a radius or a very small one on the short side for clearance if you could find one with a larger radius it would probably fix the problem but again i dont have the room for that.

Shiznity thanks for the good info I am not farmiliar with the alpha n tune what exaclty is it and can it be done with efi live or hptuners?

ewingr

Interesting. The radius is the reason my guy doing the work is going with a 3" pipe instead of 4", in order to maintain a radius. I too am close on room.

AshWS6

iTrader: (5)

Tis true, cept ATVs LT1 style plenum did lose about 20-30 ft lbs in curve below and up to peak torque, and was 5-10 or so lower peak-peak

TB you cant overdue except in terms of driveability.. yes you can have the wrong manifold for a intended purpose

Gary Z

An Alpha-N engine controler is very simple. Instead of calculating air mass using a VE table, it looks up the (previously) measured air mass for each throttle angle (alpha) and engine speed (N) operating point from an Alpha-N table. Some race engine controllers use this method because of difficulties using speed-density. Since it is simple and operates open-loop, an Alpha-N controller must be recalibrated for varying conditions. You wouldn't be able to implement Alpha-N control with a stock PCM.

ShiznityZ28

iTrader: (11)

My tuner uses Hp tuners and he purchaced an upgrade for the alpha -n tune and some boosted stuff we are using. I have not used efi live in a long time so i don't know but all it means is theres a table for a fuel multiplyer thats based on TP. Id bet efilive has something though.

ShiznityZ28

iTrader: (11)

Thats what i ment you took less words. LOL but other than a 3" runner sheet metal its hard to kill power and cammed right it wount loose power where we care about.

ShiznityZ28

iTrader: (11)

Yes you can i use it right now. its not a complete controller they use it as a multiplyer to add or subtract from the base tune. it may not be a 100% true alpha-n but thats what hptuners calls it and the idea is the same. its only effecting my tune in a very few places to help with throttle transition and just off idle. everything else is just done under the normall tuning cells.

If anyone would like more info Pm grannyshiffting