fast82z

iTrader: (1)

In attempting to answer a question of a head swap on a supercharged engine, I think I came up with some good info about doing this on a supercharged vs. turbo application.--> http://www.yellowbullet.com/forum/sh...=1#post5057754

daverr

iTrader: (1)

I think you are putting too much faith in compressor maps. there is no engine involved when they make these maps.

a centrifugal supercharger is a pump and also a compressor.So with a given blower rpm the blower will make X CFM of flow . Now insert an engine into the equation which makes Y CFM of flow. The result
X / Y = Z (boost)

if you increase Y u decrese Z. But X stays the same.
Take a F1 procharger spin it to the max on a 500 hp v8 engine and you will make boost. Take the same F1 procharger spin it to the max on a 2000 hp NA 920ci engine and you will make vacuum and less than 2000 hp. Now both engines make the same power (or close to it if you dont count friction).

fast82z

iTrader: (1)

So then why would these maps exist if they mean nothing? If it doesn't relate to how an engine (or any other restriction) flows air, how would these maps even be created?

Lets run with this to the extreme and this logic tells me that if I were to weld a solid metal cap on the outlet of a centrifugal supercharger that this outlet would continue to supply x cfm of flow... um no. When's the last time you put your thumb on the end of a garden hose and noticed no reduction in flow?

This will not hold either, and the 500hp engine will not make anywhere near the power the 2000hp engine will. This is because on the 500hp engine the blower is not only tasked with moving a mass of air, but compressing it to 20psi or so. On the 2000hp engine, the engine will actually be helping the blower spin by pulling air through it and therefore the blower would be tasked to do basically nothing and may not end up being as restrictive as you might think. Even if we assume constant volumetric flow, the extra drive power needed on the 500hp motor would be FAR greater than that of the 2000hp motor.

If you're talking about spinning a procharger to the absolute max on an engine that already make a ton of power, most of your above statements will approximately hold, but only then.

Orr89RocZ

iTrader: (20)

Interesting read... i am in this situation.

I have 2.05" valve 195cc AFRs on a 401 that I want to peak in the 5800-6000 rpm right now but i think its falling short on that. Maybe turbo, may be something else I dont know. havent dyno'd it with the new converter to find peak rpm.

I have considered a 2.08" valve 210-220 cc head. Mamo at AFR thinks i should try the 220 AFR's. Chad Speier who sells/makes the Profiler heads says use the 210cc head he has and I will make more hp than my 195's fully ported using 2.05" valve.

I think the 401" motor wtih 4.125" bore will benefit from both larger CSA of the 210cc port and 2.08" valve..however the advertised flow on the bench is similar until up over .600" lift. I am only running .564" so would I gain anything by switching heads?

Since the flow is about the same, and the valve got bigger in the 210cc head, this would change the discharge coefficients... which generally speaking higher is better for more power..but thats general. This is a ratio of max theoretical flow based on cam lift and valve size (window curtain area). I'm not a head guru and I've been reading into this more and more lately but it seems that going to that larger head would just slow down port speed, slow down discharge coefficient and possibly hurt power.

I have read you size the head for a n/a motor based on desired RPM range to determine cross sectional area needed. Then just add boost and you are good.
195's may be "small" for a 400 but since I only wanted 6000 rpm at the time, I figured they should be more than enough. My 383 could pull mid high 6000 rpm without falling off with peak in the 6250 range. Cam wasnt really huge either so I think I am right on the head being ok for the motor.

After talking to Chad Speier, I'm kinda thinking I could gain a good bit of power. Larger hole to feed air thru...given same PSI from my turbos I should see more mass flow into the cylinder even using same cam. Not 100% sure what to think on this. Changing heads is a big decision to make.

Doom86

Great info

I would listen to Chad that guy is awesome.

Did he consider the Air Wolf series for your 400 Orr? They might be a bit big for the RPM you want but those heads look incredible.

If you don't mind my opinion I think you could pick up some good power with bigger heads.

Orr89RocZ

iTrader: (20)

I inquired about the 210 profilers and 220 air wolfs and he seemed to think the 210's are the fit. Now if I want to get real nasty with the car, the 220's would be the choice...but they are a good 700-800 dollars more

InjectorsPlus

iTrader: (1)

Two things...Chad is a good guy, he'll steer you right.

And the guys at YB really know their stuff. It's a great reference site for technical discussion.

As pointed out above, these maps, flow numbers, dyno numbers, etc... all these things are tools, not law. It's good to have information, but not to be taken as gospel.

daverr

iTrader: (1)

engine is not a restriction it actually moves air. engine=air pump
A throttle is a restriction, a valve is a restriction which is how they make compressor maps. Compressor maps are made using restriction ,no engine is involved. therefore you cant base a 100% of your decision on compressor map. Are they useful?? sure they are get you close but not 100%. Remember not all the work is being done by the compressor because you have an engine (air pump) after it. with a compressor map all the work is being done by the compressor.

heres is a good example of you getting confused between an air pump and a restriction.In my example i use two different air pump not restriction. Lastly city water pressure is regulated ,if it wasnt regulated there would be no reduction of flow. Raise water pressure enough and you could cut steel.

I agree with most of this but i did not say the 500 hp engine will make 2000hp. i used a F1 procharger for both engines.

fast82z

iTrader: (1)

The engine becomes a restriction when more air is trying to be pushed through it than it would otherwise pass on its own, and thus boost is made. If you were to hook only a big pipe on the end of a blower and check the boost in it, there will be about none even though all sorts of air is passing through it. Put a restriction on the end of this pipe (whether it be a valve or an engine that doesn't already flow the amount of air this blower is currently moving) and this pipe will now show boost. I realize the air flow on the compressor map doesn't exactly translate to hp, but in the multiple cases I've used that all had concrete dyno and track information the air flow is definitely the dominating factor.


If city water pressure was regulated similar to that of a wastegate, an open hose would increase in flow until the hose itself became restrictive enough to hold back a pressure (usually 60-80psi in this case). A blower is like the city water in that it is only setup to move so much stuff regardless of the situation. Some amount of restriction will reduce the max flow by some amount until a point is reached of no gain in pressure but a big loss in flow.



I didn't say the 500hp motor would make 2000hp either, but what I read from your earlier post is that both engines would end up making the same power. I could see the 500hp motor making the f-1's max rating of 1050hp, but I certainly don't expect the 2000hp motor to loose 950hp with the f-1 attached.

daverr

iTrader: (1)

The engine is a air pump. A restriction is like a valve in which it restricts FLOW. Next time your at your kitchen sink crack open your faucet and it flows just a little because the faucet restricts the flow. So what you are saying is the engine restricts the flow from the supercharger?? instead of the supercharger moving 2000cfm max it now could only move 1500cfm max because the engine is a restriction.

1989GTATransAm

iTrader: (3)

There have been some changes in the Profiler head organization as of late. Not sure how it effects things. Darin Morgan has left and went back to RM in Texas. Dr J/Bryce now sells the Air Wolf line. Chad is changing his lineup.

Here is a link to the story.

http://www.chevelles.com/forums/showthread.php?t=336130

Orr89RocZ

iTrader: (20)

interesting...they still going to be offering the profiler lineup i hope?

fast82z

iTrader: (1)

An engine contains valves, so if we narrow an engine down to just many valves being pulsated open and closed this follows the kitchen sink example if you were to turn it on and off rapidly. This has also been roughly proven by fuel pumps, although maybe not so great since gases and liquids don't really behave the same. First we consider a mechanical fuel pump (to establish constant pump speed) that would be maxed out on a carb'd engine that only needs 5-10psi at peak volume flow. If we were to convert this engine over to fuel injection, assuming the same power is made, the same volume of fuel will need to be supplied and this fuel pump previously maxed out at 5-10psi is now demanded to sustain max flow at 45+psi which won't happen. At a pressure of 45+psi, instead of 5-10psi, this pump will flow less and be able to properly fuel less power...just the same way as an air pump moving air.

CamaroBeau

This is a good input. Thanks for sharing.

daverr

iTrader: (1)

Flow is measured by weight or volume per time not psi. now lets use your carb vs fuel injection using a mechanical fuel pump for a carb. Take a stock carb fuel pump which is internally regulated to 6 psi and use it to supply fuel to the injectors.The mechanical fuel pump will therefor try to pump the same amount of flow thru the injectors as it did with the carb. As the mechanical pump pushes fuel to the injectors it will will push until the internal regulator opens at 6psi and bypasses the fuel back to the fuel tank. In this case the fuel injectors are a restriction because some of the flow is diverted back to the tank thru the return .Now say i take the return line and pinch it just enough that the flow going to the injectors is the same as the flow going to the carb.In this case the fuel injectors are no longer a restriction (providing the mechanical pump does not break).

fast82z

iTrader: (1)

I said nothing about an internal regulator, but you still don't see the reality on the concept even though you're tip toeing around it. If you take a look at some fuel pumps that have a hp rating for carb. and fuel injection and you'll find that the fuel injection rating is a good bit lower than the carb. rating. This is certainly not because a fuel injected motor needs more fuel, but rather that the pump can't move as much fuel at higher psi...just like a blower.

daverr

iTrader: (1)

I know you did not mention an internal regulator but i used a carb mechanical fuel pump which has an internal regulator. The fuel pumps that you mention that have different rating for carb and fuel injection (magnafuel) are due to the fixed power rating of the electric motor that drives the pump. Belt driven pumps do not have different rating for carb or fuel injection ,no power limitation only pressure limitation controled by an internal regulator (dont want the pump to explode).

fast82z

iTrader: (1)

Thinking of the fuel pump mechanics, I think I have an answer to why daverr and I are correct. A belt drive fuel pump, oil pump, and roots style blower are all made the same way, and after thinking of how these gearator pumps work, I agree that these style of pumps are purely volume movers. What happens is a vain fills up with some volume of air and as this vain/air volume is rotated, it eventually runs into another "meshing" vain that takes the place of the air that was in the void. The only place this air has to go is into the motor. This also shows that the intake side of this kind of blower basically has a valve of sorts that prevents any manifold pressure from effecting the intake side in any way. Therefore, a roots and possibly a screw blower will always move x volume of atmospheric air when spinning at y rpm. Overall power between two combinations spinning this blower at the same rpm will only differ by the extra shaft power the lower n/a hp combination will need to supply for the blower to make higher boost pressure than the higher n/a power combination will have. The limit on boost pressure depends on the clearances in the blower and the fluid being moved by the blower (air/oil/fuel).

The only way a turbo and centrifugal blower flow air and make boost is by way of forces (specifically centrifugal force) applied to the air being moved by these pumps. In this case there is no form of valve, or maybe "virtual valve", that a roots style blower has so there is always a direct air path from the intake to the discharge side of this kind of blower. As air is drawn into the blower, the centrifugal force increases the air pressure. If we consider no restriction, this blower will behave very similar to a roots style of blower. As soon as we induce pressure in the discharge of this blower, the net force on the air being moved through the blower decreases and this is why this blower will begin to flow less air with a pressure rise in the discharge. The lower net force on the air means that it is being pushed out of the impeller with less force, and this leads to less flow.

daverr

iTrader: (1)

At a given centrifugal supercharger rpm it will flow X . The supercharger could only push Flow X so much at the given rpm . If the force (boost) required to move flow x thru a engine exceeds the superchargers force ability than the flow is reduced by air escaping back thru the inlet of the supercharger . This would lead to less flow . On the otherside of the coin if we could throttle the inlet of the supercharger to reduce flow x to the point that there is no air escaping back thru the inlet.than no flow is loss.
This is why there are engine requirements for each different size centrifugal supercharger.

fast82z

iTrader: (1)

I'm not going to bother correcting that since this is obviously a lost cause and I can't make it anymore straight forward.