AFR 225 Ford Flow Numbers

[Jsup]

Originally Posted by JeffMcKC

I have seen Blown Street cars with 2 mufflers under each side, when they take one set off, they loose boost, this would be right in line with what you say.

In the case of what Chris is saying, It could either be Intake, Intake Port or Camshaft depending. The Pressure could be there whatever is restricting it, but are you not more concered with the volume entering the cylinder.

With the wrong camshaft you could build a lot of boost in the intake that will never see the cylinder.

I typed a post earlier this week to say it was in the camshaft but didn't want to look like an idiot. Risking that at this point, the closer LS will "drain" the cyl faster, is this correct?

[revolutionary]

Chris you make a good point about locating specific restrictions and without pulling a reading from different points in the port it is tough to find that. A lot of guys will take a reading before and after the intercooler and compare pressure drop there as an indication of restriction. I would suggest that if you swap to a 'better' head and don't pick up any power that there is a restriction ahead of the cylinder head, maybe an intake with runners the size of peanuts. If you pick up power then you've remove some restriction. Maybe not all. You would really want to take good readings all along the tract from the compressor to the valve and see what's going on.

[SStrokerAce]

I think people are missing the big thing that BOOST = BACKPRESSURE in the intake tract. Compressors will move a set volume of air at a set RPM, so if you aren't changing the RPM level of the blower and boost goes down, YOU JUST MADE MORE POWER!

The restriction can be anything, cam, heads, intake, intercooler, TB, etc....

[coupe]

I rather think of a compressor delivering "potential energy" instead of "boost."

That way the negative connotation "restriction" is thrown out the window.

[68corvette]

Pressure alone does not tell the whole story.
I helped one guy with intercoolers by flow testing them to him.. fest flowing made least back pressure and worst horsepower.
It was just not efficient.
Still I think its good to measure temp and pressure before all relevant points.

Once I ported a head to stock engine, it was a diesel.
Stock turbo could not any more keep the same boost pressure, but MAF increased on whole RPM range.
Similar may happend with exhaust modifications, boost pressure may rise slower, but MAF numbers rise faster.. not a bad trade.

More pressure made creates more temperature, so personally I like to keep mass flow high and pressure low, if doable.

Turbo engines have approximately same pressure on intake and exhaust sides.. well they should =)
So pressure differential engine sees is quite a similar to N/A?
When I build a turbo engine I try to make it as good N/A with less CR and less LSA.
Seems like turbo engines easily have much residue exhaust pressure in cylinder so reversion can be a problem and its hard to get turbo to spool. Or thats how I have tought is the reason I can not use efficiently N/A cams before turbo is "spooled".
It might be also that compressor is not still on the job and exhaust pressure is still more than intake, so gasses travel in wrong direction.
Boosted engines just seem to be more efficient.. like if I try to build 2.2L engine to make 270hp N/A and lower then C/R and add boost it makes 1100+hp with 2.5bar including some added temperature.

My believe is that turbo engine should be made as efficient as possible with reasonable CR for boost and less overlap, then it is almost multipliaple with boost pressure.. though it depends a lot of pressure differential over engine and heat generated to intake.
I also pay extra attention to exchaust side of head to keep size small and efficient. not just to get it flow "enough" like ~60+% or so on N/A engines, depending of shapes.

Mechanical chargers are not sensitive to overlap (they work with lot of it) and they do not suffer about overkill exhaust ports + manifold.

[G-Code]

[QUOTE=Chris Uratchko;3152058]

Some of you are trying to convince me that the intake port is my restriction..... Do you think an intake runner, of any size, 100cc, to 500cc, 8 of them no less.... is going to allow any significant pressure to be built behind them with the valves hanging open?

Lets try it this way. You're building a Turbo 383" you have a choice of two heads. One flows 290 cfm at .700 and another flows 320 cfm at .700 and both have the same in/ex ratio. All else being equal which head do you choose?

On a very well built single carb N/A engine I'd tell you the second head would be worth 60-65 hp. I don't know enough about boost to tell anyone what it would be worth on a 15 psi boosted engine but it would be worth something and I wouldn't be surprised if they wouldn't be worth more than that 65 hp.

Let me ask another question.

How much pressure exists in a manifold of a normally aspirated engine ?

My 565" didn't have any pressure in the manifold, it had 1" of vac at 6,000 and 1.4" vac at 7,000 sucking through a 1,050 Domi.

G-Code

Big Inch Ford Lover

[Chris Uratchko]

[QUOTE=G-Code;3156633]

Originally Posted by Chris Uratchko

Lets try it this way. You're building a Turbo 383" you have a choice of two heads. One flows 290 cfm at .700 and another flows 320 cfm at .700 and both have the same in/ex ratio. All else being equal which head do you choose?

The one that has the best casting, and the best cooling system, and if that means the 290 model, I will run all over the 320 cfm head with lesser casting qualities and thickness with the ability to lean on the 290 cfm model, if I need to. No question.

[Vader Ta]

http://www.hotrod.com/projectbuild/h...ild/index.html It does not appear to be a very trick head on this turbo motor. Looks like the main concern is in strength of the castings. I think I would have to side with Chris in this debate.

[G-Code]

[QUOTE=Chris Uratchko;3156742]

Originally Posted by G-Code

The one that has the best casting, and the best cooling system, and if that means the 290 model, I will run all over the 320 cfm head with lesser casting qualities and thickness with the ability to lean on the 290 cfm model, if I need to. No question.

That makes since.

G-Code

[revolutionary]

[QUOTE=Chris Uratchko;3156742]

Originally Posted by G-Code

The one that has the best casting, and the best cooling system, and if that means the 290 model, I will run all over the 320 cfm head with lesser casting qualities and thickness with the ability to lean on the 290 cfm model, if I need to. No question.

All other things being equal, casting, runner volume, CSA etc which would you pick? That is more the basis of the question.

[Vader Ta]

I think the question is more to the point of if you have a good 23 degree head would you spend the extra money on an 18 degree head for a forced induction application? It seems there is no need for forced induction motor to put on a 18 degree head. Nelson is making over 1700 hp engines with 11 x heads. I would assume if you are looking for more power than that you would build a big block as a cheaper alternative .

[Chris Uratchko]

[QUOTE=revolutionary;3158447]

Originally Posted by Chris Uratchko

All other things being equal, casting, runner volume, CSA etc which would you pick? That is more the basis of the question.

Can't answer that. Depends on why one flows more than the other.... being they are the same volume, and cross section, casting, If one has a 55 deg intake seat, to spice up the flavor with 320 at peak, I'll probably take the 290.

[Chris Uratchko]

you guys really want me to pick the 320 don't ya?


What does the low lift numbers look like on the 290?

[Vader Ta]

It seems that most cams for forced induction never get to .700 lift. So if you can flow 320 @ .700 it does not really matter all that much in a sbc forced induction application.

[SStrokerAce]

Originally Posted by Chris Uratchko

What does the low lift numbers look like on the 290?

Who cares?