an engine is only going to draw in what air it can. The throttle body is either a restriction or its not.

48mm TB/no airfoil on a 500rwhp vehicle = restriction
monoblade on a 260rwhp vehicle = maybe a few horsies but no restrictions in accordance to what the engine intends to do.

 

Thought I'd add to this topic with some realworld experience. Recently tuned a high mileage (135K) 94Z with a very nice heads and cam package (cc306-ish)

I tuned the car with dual widebands to the proper AFR and timing with 48mm (stock) throttlebody.

Then the owner changed to a 58mm TB on the Dyno - much to my suprise the MAF did not take care of the additional air to meter, the car actually ran richer- I tuned the AFR to the same as the 48mm and the gains were 20+ rwtq and Hp.

dynos here:
http://www.carprogrammer.com/Z28/dyn..._AfterTune.gif

http://www.carprogrammer.com/Z28/dyn...CutOutTune.gif

Hope this helps,
-Christian

 

Christain Thanks for more Data on this! I was recently Ridiculed to the end on how much HP can be gained by this mod. As many Know I gained 25(24.8)RWHP with no other mod's. Then every wanna be never touched there car in there life slammed me because it was impossible to get that much HP from JUST a 58mm TB.

As usual you have been invaluable.

As for the TPS and Trans operation? yes a total reprogram is needed. I have base table for anyone who would like to see them. The change as stated is not liniar. the whole table moves to the first 50% of the curve for the most part.

The WOT table may be accessed also for changes. I have not had to do it on my N/A car but HAVE had to do it on Blower cars.

later all

 

Thanks Ellis, good to hear from ya.

You're not crazy. We have all been told a NA engine can't consume much more that 100% of it's potential (if that, in theory.) But none the less on modified engines larger TB's are helping out.

A good way to tell if the TB is too small is to look at the MAP readings at WOT. An intake restriction will usually show up as manifold pressure dropping gradually at WOT at high RPM.

Easy way to test is to put a vacuum gauge on either side of the Throttle body, to test the pressure differential, same can be done for MAF and air filter for that matter. I you're not seeing atomospheric pressure ( 100 Kpa, or 1 atm, 14.7 psi) then you have an intake restriction or vacuum leak and power is being left on the table.

Hope this helps,
-Christian

 

Wow! So looking at the Max #'s, you gained rear wheel:
47 rwhp & 38rwtq just from a 58mm TB and a cut-out?

You also gained another 500 RPM before fell off?

That cut-out doesn't really kick-in until 3800 RPM though...

Based on that, you could get a RPM-activated switch, and have it set to kick open the cut-out at 3800 RPM and get the best of BOTH worlds!

 

Other than TB size how about the MAF and intake restrictions before the MAF. Those can be as bad or hurt performance as much as too small of a TB.

Bret

 

As long as others understand, that until that time, (the weaker link (TB) is addressed) they (other less weak links) should be a non issue. Agree?

 

Not really since a MAF should flow significantly more than a TB to make it non-restrictive at least dyno tests show that.

I know on a LS1 you can get a stock TB to flow 900cfm where a MAF needs a ton of work to flow 1000cfm. (aka 85mm with no screen)

Bret

 

Good point Bret.

I think that'd be easy enough to check for those curious enough. You could measure pre-throttle-body pressure via a gage, or look at the MAP sensor outputs. Then determine the level of restriction from there.

As I see it, the actual airflow isn't that important cause for any orifice to flow larger masses of air, you just need a larger variation in p1 vs p2. The question is always... at what velocity is there a restriction that will limit power?

On a carb, you have that all important issue of fuel atomization. If the carb can't atomize, it'll be soggy and lackluster performance. The car will always go faster with less restriction. The real trick is reducing the level of restriction while maintaning fuel shear and atomization. For a port fuel setup, it's a whole nother ballgame as I see it.

-Mindgame

 

On a Dynapack dyno I gained 8rwhp by ditching my Moroso CAI (ZO6 MAF > 1LE elbow > Stock, ported 51mm TB). I built my own 4" intake for the street - I believe any airfilter is going to be a problem - I will not run a filter at the track anymore. I'll also be sporting a monoblade...

I also gained an addittional 9rwhp by uncapping the Borla plate.

No tuning was made after ditching the CAI and Borla plate...there might be even more to gain thru the tune. However, my A:F stayed within .1 of the original dial in.

A dyno can be a useful tool!
Ryan