[Tom Vaught]

Header science for a turbo is an interesting subject. You have all of these Chebby and Ford builds with really swoopy header set-ups into header pipes feeding into say a 106 mm turbo. The people run 190 mph. Then you have people like John Welter, (I really wish I had more pics of his engine compartment) where he has a smaller tube simple shorty header deal going to smallish header pipes and also to a 106mm turbo. John W. only runs 6.80s with his set-up, designed by Travis and Rodney.

I guess the comment would be more than one way to skin a cat.

JMO

Tom Vaught

[jdw_poncho]

Originally Posted by 62fatcat

you must be talking about a turbo setup, correct?

yes

[jdw_poncho]

Originally Posted by Tom Vaught

Header science for a turbo is an interesting subject. You have all of these Chebby and Ford builds with really swoopy header set-ups into header pipes feeding into say a 106 mm turbo. The people run 190 mph. Then you have people like John Welter, (I really wish I had more pics of his engine compartment) where he has a smaller tube simple shorty header deal going to smallish header pipes and also to a 106mm turbo. John W. only runs 6.80s with his set-up, designed by Travis and Rodney.

I guess the comment would be more than one way to skin a cat.

JMO

Tom Vaught

Hope I'm not Hy-jacking this thread but I thought my question somewhat pertained to the orginal post. So after doing a little research I cant really find a good answer on websites unless I dig some more. Building a log style manifold seems to be a pretty common thing for the DIY's. But I have the skills to build something much better. My problem is I dont quite understand how boost can be affected by header sizes. This might be one of those times where testing could be my best route.

[Tom Vaught]

I will try and answer your question by breaking it down into a few parts.

1) Log manifolds are fairly easy to build and can make fair hp but suffer from "interference" where one pulse (from a port downstream) partially blocks flow (from another port farther upstream) from the outlet. This "Interference" issue is one reason whu Hot-Rodders first looked at individual tube "exhaust systems: Zoomies.

After Zoomies came efforts based on firing orders to have the pulse from one cylinder actually help a second cylinder.

If a large valve/port has part of its flow blocked by "interference" in a common Log manifold then the flow in the head means little. Gale Banks designed a "Modified" Log manifold for his 1000 hp SB Chevy Kits that attempts to remove most of the "Interference" in the system. http://www.bankspower.com/products/show/267/85

2) An exhaust tube in a Header System is simply a LONG ORIFICE.

Orifices provide restriction to a system. Sometimes a restriction is beneficial in an engine if designed properly. You have probably heard the term the Cylinder was "over-scavenged" or you were pulling raw fuel that could be used for the combustion process right through the cylinder combustion chamber/ valves.

Here is an article on "Flow thru an Orifice"

http://www.mcnallyinstitute.com/13-html/13-12.htm

Quote: "There are several reasons you might want to install a restrictive device or orifice in a piping system.

* To create a false head for a centrifugal pump, allowing you to run the pump close to its BEP.
* To increase the line pressure.
* To decrease the flow through a line.
* To increase the fluid velocity in a line." Quote

3) A turbo works by using Heat Energy, Pulse Energy, and Mass Flow to drive the matching compressor. I have driven Turbo Turbine wheels/ Compressors on a test bench using a large screw compressor basically at ambient conditions + maybe 100 degrees (heat from screw compressor doing work). I could still make the turbo spin 220,000 rpm on the bench in less than one second. So in my opinion Heat helps but pulse energy and mass flow are more important. The screw compressor did have "pulses" but they were no where near the firing pulses on an engine. So what you have left is mass flow. When a Turbo engine is asked to accelerate quickly and there is a LAG, typically the lag is caused by a shortage of mass flow driving the compressor. This is why people are looking at or building systems like Super/ Turbo systems like the 1.4L Volkswagen Golf.

http://www.worldcarfans.com/10906171...the-year-award

The Supercharger increases the mass flow of the engine until the properly sized turbocharger can perform properly then the supercharger is disconnected from the system.

So to summarize:

1) You want to make 1000 hp, you need a properly sized compressor to move 100 lbs of air mass per minute. You need a Turbine Wheel able to drive a Compressor Wheel at the correct speeds to efficiently move that 100 lbs of air mass per minute through the engine.

2) The Intake system/ exhaust system has to be able to support the 100 lbs/min mass flow

3) Too large of a intake system hurts transient response which may not be an issue on a drag car but is on a street car.

4) Too large of an exhaust system lowers Pulse Energy which assists in driving the turbine wheel.

5) TOO SMALL of an intake system/ exhaust system restricts mass flow and you cannot meet your mass flow target.

6) Large engines (stroked Pontiac Engines) have more mass flow vs a SB Chebby type short stroke engine for any given rpm therefore you can make more power (mass flow) at street rpm conditions. More mass flow means being able to use larger turbos. Larger turbos= more Horsepower/ torque for any given rpm. Travis Q has become a fan of larger stroke engines.

So if you can build a log manifold that has minimal flow interference, has the mass flow you need to support your hp target, is strong enough to support the weight of the turbo without cracking, and made of the correct material to have decent longevity, then go for it.

Tom Vaught

Some people just use the headers to get to a spot where a heavy large turbo is mounted.

[62fatcat]

Tom,
so what are the diferences between an a/w intercooler on an engine with say c-16 fuel versus the same combo with race e-85 fuel(112 octane)?

thanks,
brad.

[Tom Vaught]

Brad,

1) The water to air Inter-cooler is upstream of the carburetor on a Blow-thru carb set-up. There will do no difference in the effect of "the water to air Inter-cooler" between the two fuels based on the inter-cooler alone.

2) C-16 fuel is expensive but pretty consistant in fuel blend. E-85 can be all over the map. Apples to oranges Brad. You get a good sample of E-85 and the engine makes good power try and get more of the same fuel.

3) A Guy named DAVE with a staged twin turbo Ranger posted on the Turbo Forums how to make a cheap Ethanol mixture tester so that you could find the good fuel and buy only the 'good" E-85 fuel.
Look for those posts.

4) Adding a Water to Air Intercooler will obviously increase power as the air charge is more dense.

Tom Vaught

[62fatcat]

Tom,
thanks again.
if i continue to use e85 i will be using the rocket brand product. this way i will have the same blend every time + it is 112octane.
i was just intersted more on the effects that the cooler temps would have.
curently my intake temps under the carb are 130* on a 90* day.
can the fuel get to cold to work properly?
i expect the temps to drop a lot.

[Tom Vaught]

No, the fuel cannot get too cold in normal racing usage. Before it was banned we used to use Ice in cans with aluminum fuel line coiled inside to chill the fuel to the carb.

Tom Vaught

[bad69bird]

Tom,

Can't the intake temp get too cold and the motor won't run right? The reason that I ask, I had a buddy who had a SBC with a YSI A/W I/C. His intake temps were around 40* and he couldn't figure out why the motor was acting up. He removed most of the ice and added water and the motor went back to running correctly (can't remember what the intake temp was).

[Region Warrior]

Makes sense bad69bird.
In firefighting, theres 3 ways to put out a fire.
Remove the fuel.
Remove the oxygen.
Remove the heat.

[BruceWilkie]

Originally Posted by bad69bird

Tom,

Can't the intake temp get too cold and the motor won't run right? The reason that I ask, I had a buddy who had a SBC with a YSI A/W I/C. His intake temps were around 40* and he couldn't figure out why the motor was acting up. He removed most of the ice and added water and the motor went back to running correctly (can't remember what the intake temp was).

Quite likely experiencing icing. Controlling humidity can be an issue as air temps drop below 40 degrees you can start making snow or even heavy frost. My turbo vair would frost the intake below 40 degrees ambient till everything got warmed up.

IMO cold fuel and cold dry air are fine you would have to get pretty cold to not burn. You need a really hot strong spark to get it going though. (Why inductive ignition is sometimes preferred over capacitive discharge)

A manifold warm enough to prevent icing may tranfer little heat to the moving air/fuel at wot conditions. It has little time to do so. Same can be said of the carb. Once air/fuel is moving at a high rate, very little heat will actually transfer to the a/f mix. The heat(if sufficient) will prevent humidity from frosting or freezing over passages, yet have little if any negative effect on power provided you have sufficient spark and cylinder pressure to get ignition started.

Something to think about: Often a car sitting outside doesnt frost up overnight when the wind is blowing yet ambient temp and humidity are suitable for frost to form. The amount of time, velocity of the breeze, quanity of moisture, and actual surface temperature is relavent to frost forming. Meanwhile a car nearby but sheltered from the breeze will be covered in frost. Only thing changed there was the breeze.

WTH does this mean?? A warm carb and manifold will be ok and not likely to hurt power provided the air and fuel remain relatively cold and velocity gives insufficient time to actually add much heat to the mass. The humidity (unless extreme) will not ice up your fuel/air passages. Draw thru turbos or roots, blowing thru an intercooler have the advantage of cooling both air and fuel to approx same temp. Disadvantage is remote possibility of humidity icing the intercooler closed which could happen with a blow-thru as well.

[62fatcat]

Good info,
i would like Tom V's input on this, especialy as far as E85 is concerned.

thanks,
Brad.

[70 bird]

Fuel Composition tester thread.....

http://www.theturboforums.com/smf/in...topic=108727.0

[Tom Vaught]

Dave2 mentioned in the article (with the sequential twin turbo Ranger) is a friend of mine from the Detroit area. 70bird also knows him I believe. I helped dave and one of his buddies with some carb stuff. NICE TRUCK!!!!

The Fuel Composition Tester that Dave came up with worked extremely well with figuring out the real amount of Ethanol in the "E-85" fuel. He gave me a demonstration of the fuel testing process.

He would be a great source for making some additional Fuel Composition Testers.

Tom Vaught

[Lonster]

Isn't the F.A.S.T. EFI systems up to the flex fuel (variable ETOH %) task already? http://www.whiteracing.com/e85.html

[Tom Vaught]

The Fast System is based on work John Meany did on the FEL PRO EFI system years earlier. You put the right "REQUESTED" air fuel ratio into the system and the system will correctly provide the injectors with the appropriate signals based on the EGO sensor.

Having a accurate number for the percentage of Ethanol vs Gasoline is critical for the most accurate calibration, IMO.

Tom Vaught

[62fatcat]

Tom,

great thread and vehicle on ford site.

But, what about the intaKE CHARGE being to cool? i think Brian H. asked it first.
how cold is to cold, and how does that aply to dif fuels, like say c-16 compared to e85.

thanks,
Brad sS.

[Travis Q]

It is, without any doubt, possible to get the air charge too cold for a given fuel. There is no reason to cool the intake charge any colder than the flash point of the fuel.

The key for each fuel is indeed the flash point, which is the point at which a material in liquid phase turns to vapor phase. Remember how we make horsepower is by burning fuel.....if you can't burn the fuel, it doesn't make a hill of beans difference how much 'cool, dense intake charge' you cram into the cylinders. When a fuel is in the liquid phase in the intake runner and combustion chamber, it tend to coalesce into large, hard to burn droplets. When you have enough charge temp to vaporize a portion (notice I said a portion) of the fuel, then it becomes very easy to burn, and therefore make power with. Now, you don't want all the fuel to be a vapor (a different thread altogether), but you don't want it to be 100% iquid, either. I have seen that air temps under 70 or so degrees F will cause issues with C16, while Q16 is designed to utilize colder air temps. Methanol needs at least 140-150 degrees F. I'm not sure on E85 or straight Ethanol, I'll have to look in my reference manual.

[62fatcat]

Travis Q,
Thank you.
Know i just need to se how cold is to cold for the corn mash under the intake.

[cgeise]

Travis - my car will see around 60 degree or less at the start of the run with our intercooler - are you saying that is low enough to cause fuel problems - and are you talking about carbs - or EFI ???