Advanced Engine Theory and Design

[The Swede]

Gang, which size on the header is the best one you know for full ported SII heads? 2 inch? Or does it depend on how big turbos we have?

I have just started to build twin headers for our car and i really don't know exactly how to solve it with the tube size.

ohhh.... maybe there are someone out there that has tried 2 different sizies in the bench?

Thanks all here for this great thread!

 

[Alky V6]

Gang, which size on the header is the best one you know for full ported SII heads? 2 inch? Or does it depend on how big turbos we have?

I have just started to build twin headers for our car and i really don't know exactly how to solve it with the tube size.

ohhh.... maybe there are someone out there that has tried 2 different sizies in the bench?

Thanks all here for this great thread!

What rpm power band are you shooting for? What's your estimated HP level?
Length relates to rpm power band.
Exhaust gas volume dependant on HP level. Inside diameter relates to exhaust gas flow speed (feet per second) per volume. Target average speed is 240 to 300 fps.
For a max effort Stage II I've calculated my exhaust would start at 2 inches ID for 10 inches, increasing to 2.125 for 15 inches and ending in a collector tube size of 3 inches for another 6 inches before the turbo.
I know your target HP is a bit lower so the header dimensions would probably be a little different.

 

[robbyc]

you must also remember when you increase tube diameter you increase volume but you also decrease speed and this decreases heat so you can go with a larger tube but if it is a little big you can fool the exaust to see a higher speed by thermaly covering and keeping the heat in the tube this will benefit in several ways you will have more volume, and keep the speed of of flow this will help turbo spooling and of course the faster the flow out the bigger the void behind it that will have a derpession that will of course fill once again ........if you ever want to learn about the science of exaust look at the lowly 2 stroke and all that goes into the science of design of the pressure wave in the expansion chamber the jet ski guys will sometimes vary the amount of water going into the chamber to change the shape of the wave as well as cool it to change scavenging effect for various rpm levels
robby

 

[robbyc]

here is a link that may help you in your search for a header http://www.burnsstainless.com/TechArticles/Theory/theory.html

 

[Alky V6]

Vout Lambda Petrol LPG Methanol Diesel

1.40 0.686 10.08 10.63 4.39 9.94
1.45 0.696 10.23 10.79 4.45 10.09
1.50 0.706 10.38 10.94 4.52 10.24
1.55 0.716 10.53 11.10 4.58 10.39
1.60 0.727 10.69 11.27 4.65 10.54
1.65 0.739 10.86 11.45 4.73 10.71
1.70 0.750 11.03 11.63 4.80 10.88
1.75 0.762 11.20 11.81 4.88 11.05
1.80 0.774 11.38 12.00 4.95 11.23
1.85 0.787 11.57 12.20 5.04 11.41
1.90 0.800 11.76 12.40 5.12 11.60
1.95 0.814 11.96 12.61 5.21 11.80
2.00 0.828 12.17 12.83 5.30 12.00
2.05 0.842 12.38 13.05 5.39 12.21
2.10 0.857 12.60 13.29 5.49 12.43
2.15 0.873 12.83 13.53 5.59 12.66
2.20 0.889 13.07 13.78 5.69 12.89
2.25 0.905 13.31 14.03 5.79 13.13
2.30 0.923 13.57 14.31 5.91 13.39
2.35 0.941 13.84 14.59 6.03 13.65
2.40 0.960 14.11 14.88 6.14 13.92
2.45 0.980 14.40 15.18 6.27 14.20
2.50 1.000 14.70 15.50 6.40 14.50
2.55 1.037 15.25 16.08 6.64 15.04
2.60 1.078 15.84 16.70 6.90 15.62
2.65 1.121 16.48 17.38 7.17 16.26
2.70 1.169 17.18 18.11 7.48 16.95
2.75 1.220 17.93 18.91 7.81 17.69
2.80 1.276 18.76 19.78 8.17 18.50
2.85 1.337 19.66 20.73 8.56 19.39
2.90 1.405 20.66 21.78 8.99 20.38
. . .
4.00 free-air (can be used for calibration)

Gasoline / Methanol

6.0 / 4.1 - Rich Burn Limit (engine fully warmed)
9.0 / NA - Black Smoke / Low Power
11.5 / 4.5 - Approximate Rich Best Torque @ WOT
12.2 / 5.5 - Safe Best Power @ WOT
13.3 / NA - Approximate Lean Best Torque
14.6 / 6.45 - Stoichiometric AFR (chemically ideal)
15.5 / NA - Lean Cruise
16.5 / NA - Usual Beast Economy
18.0 / NA - Carburetted Lean Burn Limit
22+ / NA - EEC / EFI Lean Burn Limit

It is interesting to note that while burning 100% methanol and using a lambda sensor calibrated to read out for gasoline, my best performance has been at an AFR of 11.4-11.5. Any richer and the engine would get lazy. Compare this to 'The Chart'. Lambda .9 is lean best torque and 1.1 is best economy.

One other interesting thing to note. Look at how small the window is between 'approximate rich best torque @ WOT' and the 'rich burn limit' for methanol. I guess that's why they say you need a mini arc welder to fire very rich mixtures of methanol.

I brought these quotes over from another thread. They are well worth copying down for future reference. One interesting comparison to note. If you study the AFRs between gas and methanol, except for stoich, the AFR numbers don't represent the same lambda number. For instance, approximate rich best torque for gas and methanol are lambda .787 and .706 respectfully. Yet when I am tuning for max power using my lambda sensor that is calibrated for gas readings, I obtain max power at .787 lambda. When I shoot for a 10.3 to one AFR or .706 lambda the engine gets real lazy. Hmmm. This will require more testing and tuning. Remember that one of the variables that can change lambda readings is exhaust gas content .

 

[Alky V6]

you must also remember when you increase tube diameter you increase volume but you also decrease speed and this decreases heat so you can go with a larger tube but if it is a little big you can fool the exaust to see a higher speed by thermaly covering and keeping the heat in the tube this will benefit in several ways you will have more volume, and keep the speed of of flow this will help turbo spooling and of course the faster the flow out the bigger the void behind it that will have a derpession that will of course fill once again ........if you ever want to learn about the science of exaust look at the lowly 2 stroke and all that goes into the science of design of the pressure wave in the expansion chamber the jet ski guys will sometimes vary the amount of water going into the chamber to change the shape of the wave as well as cool it to change scavenging effect for various rpm levels
robby

Keep in mind that as HP increases so does exhaust volume and the need for larger primaries and collector size. I would tend to lean toward the smaller size to keep exhaust speed up, but you don't want to choke the engine either. It's a careful balancing act. I am from the school that teaches turbo engines react to intake and exhaust manifold tuning just as naturally aspirated engines do. Sure, you could argue that a turbo engine makes so much power anyway, why bother with calculating a tuned system? Every little bit adds up.

 

[SPEEDSTAR]

Don, You can still improve your 100% meth fuel by adding gas as an ignitor, acetone as a blender and molecular lube, and top end lube,fuel lube . This is a better fuel than 100% meth, without any drawbacks that I can see. IMO I would run this improved blend meth and never go back to straight meth. On another note , could the exhaust have a vacume on it caused by the cars accellaration that would help ve in some way. Also IMO R+D aimed at increasing power needs an ECM meshed with state of the art knock sensing, exh. monitoring, 02 control etc, to allow foward progress without destroying the engine, . It would be nice to have someone like Bill Gates to finance a program where this could be done properly. To fully take advantage of all the tech availibly , a well designed safety valve needs to be in place first or the next round of engines built will only be small steps forward. It might take a long time to break the 1800 hp barrier.Consider the exh. content of the turbo diesel AUDI lemans cars. The exh. content may be a restriction to better performance that could be improved with a vacume created in the exh.

 

[Alky V6]

Don, You can still improve your 100% meth fuel by adding gas as an ignitor, acetone as a blender and molecular lube, and top end lube,fuel lube . This is a better fuel than 100% meth, without any drawbacks that I can see. IMO I would run this improved blend meth and never go back to straight meth. On another note , could the exhaust have a vacume on it caused by the cars accellaration that would help ve in some way. Also IMO R+D aimed at increasing power needs an ECM meshed with state of the art knock sensing, exh. monitoring, 02 control etc, to allow foward progress without destroying the engine, . It would be nice to have someone like Bill Gates to finance a program where this could be done properly. To fully take advantage of all the tech availibly , a well designed safety valve needs to be in place first or the next round of engines built will only be small steps forward. It might take a long time to break the 1800 hp barrier.Consider the exh. content of the turbo diesel AUDI lemans cars. The exh. content may be a restriction to better performance that could be improved with a vacume created in the exh.

You have brought up an excellent point. Anything that can be done to reduce atmospheric pressure around the exhaust pipe exit will help VE. Dinner calls. I'll give some examples when I get back.

 

[SPEEDSTAR]

Good idea, lets eat
Another idea, this thread could be used to gather a smourgusborg of ideas over,say a six mounth period, [we need more imput from others] and then start a new thread covering the best ideas from the six month run, but now let it grow scatter barrel style, then start fresh. This thread will be phase-one

Also I wuold like to see product developers incorporate a modular parts compatibility paradim so other advances can easily be used and mesh with existing products, and each new product would continue advancing this way.
I believe the evolution of aftermarket performance products will happen much faster, if it goes in the above fashion

 

[robbyc]

i work as a crew cheif for a p2 team in the american and the offical word is the audi uses bio diesel but it smells like something else
robby

 

[Alky V6]

Good idea, lets eat
Another idea, this thread could be used to gather a smourgusborg of ideas over,say a six mounth period, [we need more imput from others] and then start a new thread covering the best ideas from the six month run, but now let it grow scatter barrel style, then start fresh. This thread will be phase-one

Sounds good to me.

Back to VE improvement by atmospheric depression at the exhaust exit.
Those that have seen the routing of my exhaust pipe may get the point of why I routed it the way I did after this discussion.
When I was tuning in Alky Buick V6 ver. 2.0, I had not yet fabricated the exhaust piping past the turbo. I hadn't even figured out the piping size. I had the engine running at that point and was tuning in the idle and low throttle position AFRs. Anyone who burns alcohol knows that very few people build a tolerance to dealing with the exhaust fumes for very long, especially in a shop bay. I rigged up some plumbing and a fan to carry the fumes outdoors. The end of the exhaust fan plumbing was set at the turbine housing to catch exhaust as it exited the turbo. It was not set real well. After tuning in the idle cells and moving on to other cells of the fuel map, I would notice that when I came back to idle sometimes the idle tuneup would need more tweaking. I would also notice more exhaust fumes in the shop and would have to reposition the exhaust fan plumbing because it had moved out of position. After what seemed like countless back and forth with this, I soon realized that when I would reposition the exhaust plumbing, the idle tuneup would have to be tweaked again. I figured out that when the exh plumbing was positioned to pull exhaust from the turbo most efficiently, my idle mixture could be leaner and the engine idled smoother than when the plumbing had moved out of position and the exhaust fan was no longer helping to pull the exhaust from the turbine housing. That experience alone taught me a lot.

Your better off if you can keep exhaust back pressure past the turbo to an absolute minumum. That would mean an exhaust pipe with the largest reasonable diameter, the fewest bends and the shortest length. My exhaust system reflects that thinking. The next item to tackle was how to create a low pressure depression to simulate the exhaust fan that had taught me so much. Continued on next posting.

 

[Alky V6]

i work as a crew cheif for a p2 team in the american and the offical word is the audi uses bio diesel but it smells like something else
robby

French fries?

 

[robbyc]

hey don you may have experienced the benulie effect that blows an sucks all at the same time lol
robby

 

[Alky V6]

hey don you may have experienced the benulie effect that blows an sucks all at the same time lol
robby

Yeah. I guess you could say the experience blew and sucked with a great outcome.

 

[robbyc]

no i have a diesel i run on homemade biodiesel it smells like a bunch of fries but the audi dont but let me tell you its a torque monster!

 

[Alky V6]

I noticed a book at the bookstore that outlines how to make biodiesel. People brewing their own fuel.

 

[robbyc]

very easy to do and you can make it for around 40 cents a gallon and you use wood alcohol and lye to correct the ph and sell off the indrustial grade glycerin or make some of grannys home made soap

 

[SPEEDSTAR]

Don , I finally am now understanding your view on tuning a turbo exh system, and my creative brain cells are justa dancing with ideas, considering , pipe size, direction it goes,anti-reversion , positive/neg waves, vacumes,vortex's, internal manipulation of temperatures, internal control of flow, where positive or neg pressure waves or conditions are needed.....wow...pass the fries

 

[Alky V6]

I'm sure that most have noticed the fancy window hooks used in Pro Stock and elsewhere to help hold the side windows in place. It's done because of the low pressure zone that is created as air is pushed out to the sides by the windshield. With the low pressure zone created on the outside of the side windows and the normal air pressure in the cabin of the car, the air pressures try to equalize by pushing the window out. Many people ignore just how powerful this force is until they get to the end of the track with their side windows hanging out. The same low pressure zones are created around the front end. Especially if the front end has relatively flat zones facing forward. We all know the Regal has its share of flat zones. Find an area past one of these flat zones, point the exhaust piping slightly rearward and angle cut the end of the pipe in such a way that a suction is created on the end of the pipe by the air rushing past it. Low pressure depression. Let the horsepower cometh! :wink:

 

[Alky V6]

Don , I finally am now understanding your view on tuning a turbo exh system, and my creative brain cells are justa dancing with ideas, considering , pipe size, direction it goes,anti-reversion , positive/neg waves, vacumes,vortex's, internal manipulation of temperatures, internal control of flow, where positive or neg pressure waves or conditions are needed.....wow...pass the fries

Praise the mighty piston and rod, brother. Pass the fries this way.

You bring up another interesting device. An anti-reversion device. The perfect place to put one is at the point where the exhaust pipe is stepped up, when using stepped primaries. That brings up another topic of discussion. Continuously tapered exhaust primaries. Yes, I have actually seen them. Very, very expensive. Stepped primaries are nothing more than an inexpensive way to simulate a tapered pipe.