Bigger TB, some interesting numbers...

[illSHOyou]

Can a fully built N/A 3.2L SHO utilize a 75mm throttle body? I think the answer is yes.

I have been running some basic numbers on the SHO intake system to see whether there was consistency throughout the system. Does the system grow smaller in volume as the air moves closer to the cylinder, and does it maintain good velocity?

Here are the numbers:

Primary port area: 1.23” sq inches
Secondary port area: 1.48”
Individual Tube to Plenum 3.14”
Y Neck Dual Tubes 6.28”
Stock 65mmTB 4.9”
Stock 55mm MAF 3.7”

From the data above you will notice how the stock system starts small, peaks in size at the Y cross-section area, and then reduces again all the way to the valve. The stock TB does not equal the flow that the Y cross-section area demands, not to mention the MAF. As a result velocity reduces, and over-all peak power reduced. The stock system will have major restriction due to frictional pumping loses and reduced volume.

Most members on this forum when upgrading MAF choose the 80mm MAF. Some members have also upgraded to 69mm TB. The numbers with the new system.

Primary port area: 1.23” sq inches
Secondary port area: 1.48”
Individual Tube to Plenum 3.14”
Y Neck Dual Tubes 6.28”
69mm TB 5.77”
80mm MAF 7.76”
(The Center Bridge maybe worth 1.5” so 6.26” sq inches)

The new system gets very close to maintaining the same volume all the way to the Y area behind the throttle body, but could we do a little better? A 75mm TB would yield 6.819” sq inches and that would make the system nearly perfect all the way to the Y cross-section area.

CAI vs. Stock Filter Box

Many people on the forum believe the stock air box to be sufficient, but what if we could install a large box with bigger better numbers?

Numbers:

Stock Box Volume 141.45” cubic inches
Filter Surface Area 60” sq inches

CAI Box Volume 471.5” cubic inches
Filter Surface Area 170 sq inches
(Cone Filter)

Clearly while the stock system is not bad, it’s certainly not the best system available and best use of engine bay area. The CAI system described should yield less pressure drop, and reduce pumping losses to engine. Don’t know what a dyno will say, but the numbers look pretty good.

Anybody have anything to add or point out? Would larger filter area and bigger box yield more power? Can you ever go to big?

 

[SuperHO]

i think it is possible to go too big...after all, the combustion chamber's only gonna hold so much air, regardless of how much you try to let in without forcing it. try this experiment...take a drinking straw (preferably from mcdonald's cuz of the size) and take several deep breaths through it. now, wrap your lips around a cardboard tube from a roll of toilet paper and do the same. more air in, at it's actually harder to breathe. same concept IMHO.

 

[hawkeye18]

It's like deja vu all over again. It seems about once every year and a half, somebody new comes in and says they can revolutionize the intake system by making the MAF / TB bigger.

Simple fact is, it doesn't. Please believe me when I say it's been tried before. Now, with that having been said, if you come up with a way to make it better that nobody has thought of or done before, then by all means go for it! I don't want to discourage you from trying by any means, but I will warn you that this pool's been peed in a lot before.

I do have to give you credit, though, I haven't seen anybody do such a thorough analysis of intake cross-sections in a long time!

 

[silversho89]

Good stuff Sean. Are you going to redo your air box you already made or are these dimensions on your current one? Cuz that and the intake you've already built made a **** of a difference. I wouldve never thought it would have turned out so good. The ideas and components you've built are certainly alot better than all the other ones out there.

 

[illSHOyou]

Good stuff Sean. Are you going to redo your air box you already made or are these dimensions on your current one? Cuz that and the intake you've already built made a **** of a difference. I wouldve never thought it would have turned out so good. The ideas and components you've built are certainly alot better than all the other ones out there.

The current one does not have the 170" sq inch cone filter and the air box is probably 350" cubic inches. I have the smaller cone filter right now that is 6" long. The 170 is 9.75 inch long, but it will fit, and I will probably make a box change that expands it to 471" cubic inch.

 

[illSHOyou]

It's like deja vu all over again. It seems about once every year and a half, somebody new comes in and says they can revolutionize the intake system by making the MAF / TB bigger.

Simple fact is, it doesn't. Please believe me when I say it's been tried before. Now, with that having been said, if you come up with a way to make it better that nobody has thought of or done before, then by all means go for it! I don't want to discourage you from trying by any means, but I will warn you that this pool's been peed in a lot before.

I do have to give you credit, though, I haven't seen anybody do such a thorough analysis of intake cross-sections in a long time!

There are reasons why I choose to cross these bridges and examine these modifications. While many of these modifications are nothing new; the problem is most of the time there is never much consistency among SHO owners. I am not saying there are not a few really dedicated owners that have all the modifications and tune them thoroughly. I am just saying those owners are usually few and far between, and each one usually takes there own approach. Obviously some of the best are Lance Chaney, RJ-92, Freak SHO, Ernie with extensively modifications to there motor.

Based on the Dyno Archive Lance Chaney has a bone yard 3.2L with cams, intake mods, and a big 3 inch free flow exhaust making 250 hp at the wheels. His exhaust is considered huge among SHO owners, borderline too big, but his setup works. Could you imagine if this same engine had 11:1 compression and extensively worked over head?

Ernie built a cheater 3.0L engine with big compression, big cams, extensively worked over intake with huge cone filter making impressive numbers. I am pretty sure that Ernie flow benched the stock intake manifold and matched flow all the intake ports so that it could hit that big peak number. If anybody is aware of intake restrictions Ernie is probably the only one who has the information from testing. That information would be as good as gold too.

A 69mm TB is not a bad modification, but only gaining 4mm from stock. Imagine what a 75mm might net? A 10mm gain over stock sounds more like it. That is a pretty large change from stock while 69mm not so much. The cross-sectional area behind the TB is 6.28” sq inch. The 75mm TB is 6.819” sq inch, but by time you take the butterfly assembly into account you’re probably close to that 6.28” sq inch number which is perfect! The only driving force for a N/A engine is the 14.7 psi atmosphere air pressure. In order to make maximum velocity and flow into the plenums for max power we need to meet that airflow in the Y area. It’s the same concept as cutting the ends off both plenums and mounting two throttle valves. Any changes in cross section area are going to either increase gas velocity or decrease. The stock setup is all over the place on cross section area until your past the Y area, increasing and decreasing.

 

[HotRodKid]

Primary port area: 1.23” sq inches
Secondary port area: 1.48”
Individual Tube to Plenum 3.14”
Y Neck Dual Tubes 6.28”
Stock 65mmTB 4.9”
Stock 55mm MAF 3.7”

Anybody have anything to add or point out? Would larger filter area and bigger box yield more power? Can you ever go to big?

i would point out that the crossover tube will effectively add cross sectional area to "individual tube to plenum" IF its designed properly

but i also i dont thing that the STOCK crossover does much in this respect due to its rather restrictive design. Hence why removing it completely makes little to no difference

also, these are the sizes i have recorded for the primary and secondary ports, based on the GASKET (ie: port size @ that point if you port the heads and runners to match) these numbers do not reflect actual port size any place else though

primary: 1.370
secondary: 1.742

 

[NovaSS]

Great info. The only problem is these are static numbers. Two different port of the same cross sectional area can have two completely different shapes and flow completely different numbers.

Unless you are using a flow bench or dyno you are guessing, and there is nothing wrong with that.. we all do it and this is how great idea start but thats all it is, a place to stasrt real world testing.

 

[SuperHO]

as i'm far from any sort of engineer, shouldn't air temp be a factor in this as well, seeing as how cold air is denser?

 

[illSHOyou]

The cross over tube main influence is probably intake reversion. It probably does support air flow between the back cylinders, but who knows how much. It does make up the over all plenum volume or at least contributes to it. Anytime I port a manifold I port the cross over big on the ends. I don’t know if it’s for better or worse?


Let’s stop looking at the Y Area for a second. Each tube that feeds the plenum is 3.14 sq inches. If we take the new correct numbers from HotRodKid of the port area is 3.112 together. As you can see each plenum has exact that amount of sq inch flow supporting them. It is in my opinion then that if you have a maximum effort 3.2L SHO you need to match the flow rates in the Y Section to support the plenums at there fullest. The back lash is probably a really touchy gas pedal with very quick tip in response. Lets face it the factory was not going to care, try to get more hp, or upset the consumer like feel of the car. Even if one was to conduct an intake such as describe and not gain anything I don’t believe they would lose anything. Many cars that I have reviewed really never lose any power to a slight TB upgrade. At least the 10+ I have seen. Intake patents from Yamaha have stated that the engine sees a slight vacuum in the plenums before the secondary opening (3,500 RPM), and after secondary opening (5,000+). This vacuum ready has been documented as degraded cylinder filling and avoided throughout the design of the intake manifold.

 

[SeanMc]

Dyno proof please. Kthx.

 

[zblackbeast]

i think it is possible to go too big...after all, the combustion chamber's only gonna hold so much air, regardless of how much you try to let in without forcing it. try this experiment...take a drinking straw (preferably from mcdonald's cuz of the size) and take several deep breaths through it. now, wrap your lips around a cardboard tube from a roll of toilet paper and do the same. more air in, at it's actually harder to breathe. same concept IMHO.

While i agree completely what your saying, that makes sense only if the intake was consistant the whole way through. According to his numbers (and we all know this) the intake goes from small to large up to the Y section. In that aspect i would think its like breathing from a funnel. What is easier breathing from the big section (what the SHO intake does, or breathing from the small side which is what i believe he is trying to achieve here. ALSO, to add to that i would think we would want a double funnel affect which is what the stock system is going from small to big to small agian. I would imagine this changes the flow of the air dramaticly. If we were to make it almost linear (not going to happen) i would imagine that would yeild the most gain.. No?

 

[38SHO]

I'm with seanmc on this one


theory is all great for thinking, but lets see what really happens in the real world

 

[SHOtime2511]

i gave up trying to make decent power in N/A form because of just this.
IMHO its like trying to squeez OJ from the peels.

to quote the toolman;
its like trying to make a windmill as efficient as possible but keeping it locked up in the basement,when you could simply move the windmill outside where the wind is.

 

[SuperHO]

just a shot in the dark...would throwing two stock throttle bodies on the opposite end of the intake in place of the crossover tube negate all this speculation? now i gotta find a pair of throttle bodies and a rod long enough to go between em...

 

[SHOtime2511]

just a shot in the dark...would throwing two stock throttle bodies on the opposite end of the intake in place of the crossover tube negate all this speculation? now i gotta find a pair of throttle bodies and a rod long enough to go between em...

then you have to figure a way to run speed density or 2 MAF's.

 

[K-Dawg]

just a shot in the dark...would throwing two stock throttle bodies on the opposite end of the intake in place of the crossover tube negate all this speculation? now i gotta find a pair of throttle bodies and a rod long enough to go between em...

Three throttle bodies. **** yeah!

then you have to figure a way to run speed density or 2 MAF's.

Could Y from one MAF.

illSHOyou, out of curiosity, what's your occupation?

 

[SHOtime2511]

honestly one thing id love to see is someone getting a speed density setup with a GM 5 bar MAP to work with this car. that could open up a few doors.

 

[SuperchargedSHOguy]

honestly one thing id love to see is someone getting a speed density setup with a GM 5 bar MAP to work with this car. that could open up a few doors.

Do it.

 

[SuperHO]

i'm currently brainstorming how to make the twin throttle bodies work with a flipped intake and a Y off a 73mm MAF and stock airbox...