Advanced Engine Theory and Design

[The Swede]

What do you guys think about the exhaust channels shape in the head?

What is the best flow, O-shape, D-shape or square with radius?

Wondering since i started to work on the heads today and they have the square shape but the headers had the O-shape.

And, can we use titan valves with methanol?
Should the exhaust valve have stainless, inconel or do they survive the high temp with titan?

 

[Alky V6]

What do you guys think about the exhaust channels shape in the head?

What is the best flow, O-shape, D-shape or square with radius?

Wondering since i started to work on the heads today and they have the square shape but the headers had the O-shape.

And, can we use titan valves with methanol?
Should the exhaust valve have stainless, inconel or do they survive the high temp with titan?

Hopefully a head porter familiar with Stage II heads will give us some insight on the port shape.

Titanium is OK for the exhaust side with methanol. As long as exhaust temps stay below 1400 F. Methanol exhaust temps are typically 1350 F at the most. It is a borderline situation and some very slight warpage of the valve is possible. I had some warpage on the last engine, but it wasn't bad enough to affect valve seal. The current engine is again using Ti on the exhaust, but the valve is coated this time. Berrilium copper seats or an equivalent material are highly recommended for superior heat transfer from the valve to the head. If you use another valve material, you don't have to get exotic for the sake of heat when burning methanol. Choose the lightest material.

 

[robbyc]

great idea

i would love to be involved in this if allowed just to give some of my back ground i am the crewcheif of an american lemans lmp2 team vandersteur racing http://www.americanlemans.com/drivers_and_teams/Team.aspx?ID=21 i have been involved iin racing since a teen i own a shop in upstate south carolina where i do restoration work, tuning a lot of tubo systems. some of the technology i have seen such as closed loop boost control audi with its direct injection and no starter the computer knows where the crank is so it injects fuel in the cyl and gives spark to push piston and start engine we build stuff out of carbon fiber like you would fab up a bracket not to mention the data systems then we have diesels that are the fastest cars on the planet in the audi r10 so i hope to be a party to this and i hope to be able to add to it as well and from what i read in these post i am indeed in good company on... and the car of my choice is my buick gn that i am trying to find stage 2 stuff to build as this engine is unbelieveable for a basic design that harkens back to the late 50s i have others too but not the porsche i have or countless big block and small block cars make me smile the way it does ok i am going to stop before i wear out my welcome
robby craig

 

[Alky V6]

Glad to have you onboard Robby. I hear you on the basic design of the Buick Stage II V6. Technology ahead of its time that still shows up in new V8 racing head designs today. Shallow valve angles, small combustion chamber, raised ports. Your more than welcome to start a discussion on any tangent you feel like. Post those pictures of the filtered turbo inlets you mentioned. I'm sure others would be interested in anything you have to contribute.

 

[Alky V6]

I've been sitting here watching F1 racing and an idea popped into my head. It's not a new idea, but I thought I'd throw it on here for food for thought.

Active airfoils that change downforce according to traction needs either during heavy acceleration, braking, cornering, etc. It would be a feedback type system tied into a traction control system and engine management system.

 

[SPEEDSTAR]

Thats exactly what I thought Bill A. car needed, when if I remember right, he said he was spinning thru the trap. In drag racing, you wouldnt want traction control only, you need to control all avaible power and convert it to perfect traction. Every moment from launch to trap would need to be perfected , the goal being max accellaration at each moment. All aspects of energy transfer aimed at the goal ,ie; active downforce using wheelspin sensors tied into aero control that is programable in rate of %, and ramp. It may need an accellerometer data recorder.

 

[robbyc]

active airfoils

it is a very easy thing to set up giving the data systems and feed back systems we have nowdaysits a matter of setting up a sensor to detect and a set of instructions to act on the info now of course this sounds simplebut we have all manner of sensors and differnt systems to control it and if you wanted to roll your own you could use a megasquirt open source system they are easy to build have all manner of support from the community that surrounds it and if you are so inclined you can even write software to do whatever you want so you can cheaply develop what you want
robby

 

[SPEEDSTAR]

And just by the nature of the design, it could have an inherent track learn with a range of corrected maps to use , Like you said , now this should be easy to do.

 

[SPEEDSTAR]

A good platform to begin with

The Turbodragster could be equiped with axle sensors,adj rear wing, adj front wing , all tied into a simple controller, .....This could improve et by .75 without compromizing max. engine power. Also if he is able to increase power switching to methenol,[ I have issues with straight meth as the fuel,] the dragster will be even faster. Now is a good time for me to addrese the straight meth issue, without getting off the electronic topic,....Straight meth even with some top end lube is not yet a good fuel. This is what I have learned..
.....
Meth is very dry, so add top end lube, for the upper cyl

it has molecular adhesion and friction,add acetone[helps during injection for atomization and spray pattern] and also helps as a blender for all added ingredients.

Add gasoline as an ignitor,meth is a very wet ratio to air fuel, its hard to light and does not burn fast enough by itself.....

Add nitromethane as a thermal supercharger, when more boost is a problem , this allows more power and actually helps control some combustion problems that come with to much boost,

Add propylene oxide to add heat if needed, it can be added as a % in general or can be 7th or 8th injected at a separately programmed rate as needed ......

Add a fuel lubricant for seals ie: for the fuel system as a whole.

Heres a basic blend ...meth, 10%gas,10%acet,15%to30% nitromethane,top end lube,fuel lube,3% to 10% prop oxide as needed for combustion temp

Theres probably alot more , but thats the basics as I understand it. JEFF

 

[SPEEDSTAR]

The timing will need to be advanced by around 3 degs. to 7 degs over timing for straight meth, depending on the % of nitromethane, because it burns slower and is releasing the extra o2. The mixture needs to be richer also, relative to the nitro%, because of the extra o2 , This makes a longer , more powerful power stroke. Exhaust temps need to be lower also because the combustion last longer and so do cylinder temps. So the richer mixture makes more power and helps keep the cyl, heads, and pistons from heat soaking to the point of meltdown. The difference between a straight meth engine and one on this ROSWEL fuel is like a contact of the 4th kind, It'll make you blush and goosebump all over. JEFF

 

[robbyc]

the thing to remember with fuels and timing detonation and such is two main things ....histeris of knock this is a condition where when tuning with knoock sensors it allows you to tune to the correct knock threshold what happens is knock may start at 36 degrees in a givin design but in order to stop it you have to drop timing to say 28 degrees so the thing to do is to set max timing to the threshold ......so while on the subject of detonation ever wonder why a piston that melts at 1220 f and combustion temp is 4500 f and the piston doesnt melt well the reason is the plasma gas that surrounds the chamber and piston this acts as an insulator and what happens is the cyl pressure spikes so fast that the flame punches through the plasma to put that flame on the piston and burn a hole in it this is where most people also dont understand that low octane fuel burn more abruptly and quickly with high cyl pressure and high octane fuel burns more slowly and smoothly

 

[SPEEDSTAR]

Rob, Let me check if I am understanding this right, There is a plasma gas that acts as a containment for an energy release that otherwise will destroy first, the piston top[ it being the thinest wall of alum] and then other parts of the combustion chamber , cylinder wall could deform, head will melt partially in. So with a fuel like the blend I mentioned , the slow burn characteristics of the meth, and the nitro methane inherently create a low spike burn, whereas nitrous oxide releases it 02 very quickly, this in turn burns the added fuel very quickly , causing a spike that burst thru the plasma gas barrier. Are there any additives to gas to lessen that spike when using ni-ox, I have always heard that a nitrous engine wears out quicker because of the hammering effect of itsfaster release of energy, and just the opposite with a turbo or nitro-alcohol engine. The first causes knock less predictably than the later two.JEFF

Also can nitrous oxide be blended with other gases to improve its nature
and why havent outlaw classes used alcohol- nitro methane blends more?

 

[SPEEDSTAR]

How about a triangulated set of custom knock sensors tuned to block out normal engine sounds, even solid lifters, and using the latest digital technology to sense knock. Like running the engine without any knock so the processor will know what sounds to ignore, and artificially program in different knock wavelengths to be recognized and acted on. JEFF

How bout a solid lifter valve train designed to give off a soundwave that is stealth.

 

[Alky V6]

Also can nitrous oxide be blended with other gases to improve its nature
and why havent outlaw classes used alcohol- nitro methane blends more?

The use of nitro is very controlled in organized racing. The 1/8 mile track that I go to has starters that can sniff out even the smallest percentage of nitro, even if aromatic additives are mixed with the alcohol. If your suspected of nitro, your kicked off the track. The track's insurance won't allow you to run with nitro. From what I have been told, nitro is even harder on the fuel system than alcohol and once you've added nitro to your fuel system it's hard to get the traces out of the system for testing purposes.

 

[robbyc]

from what i understand about nitro is that it is a monopropellent that carrys its own o2 and i also understand that it after the exaust valve is open it burns after cause of slow combustion the good news is the air fuel ratio is around 1.7 to 1 you can burn 8 times the fuel with nitromethene but it only carrys 2.5 times the energy as gasoline not to mention i believe its hard on pistons of at least when you make 6000 to 8000 horsepower those top fuel guys change pistons more than i change underware...........i mean my mind
robby

 

[robbyc]

hey jeff the air cooled porsche used knock sensors designed to block out some mechanical noises cause the air cooled engines have fins that vibrate aw a well as some of the tins that route the air around the cyls. these were used in all the c2 c4 cars up tp the water cooled 996

 

[Alky V6]

How about a triangulated set of custom knock sensors tuned to block out normal engine sounds, even solid lifters, and using the latest digital technology to sense knock. Like running the engine without any knock so the processor will know what sounds to ignore, and artificially program in different knock wavelengths to be recognized and acted on. JEFF

How bout a solid lifter valve train designed to give off a soundwave that is stealth.

We should have a discussion of the current technology of knock sensors. I for one could use a refresher course. I haven't been using the knock sensor, but plan on playing around with one on this engine.

 

[robbyc]

i want to thank you guys for letting me join in to these talks ...i love to share what little i do know and i really love to learn i can see that i am in good company
robby

 

[robbyc]

me too i will see what i can dig up on this as we are using some sort of knock feed back on our race car cause i have seen some info in the data log but the guys from aer wont let me near the info they guard it all like the secret service they wont even let the car owner have a dyno sheet i had to backward engineer the dyno sheet based on all i could gleen from the engine by all the info i could get from the engine (cam portflow ect) and using a computer program very much like desktop dyno but more along the lines of what f1 teams use it uses cyl emptying and filling algorithms to predict what a engine will do
sorry for babbling robby

 

[Alky V6]

The more babbling the better on this thread. Thank you, Robby, for contributing. I'll do a little research also on the knock sensor. The better we understand how it works, the better we can figure out how to put it to good use. The biggest drawback I can see with the knock sensor is the number of knocks that need to be seen by the computer before timing retard is commanded. I'm aware that this number is programmable in most ECUs and I need to revisit that with mine. It's just that with alcohol, when it goes into preignition, after the first few events, the engine is done for. I need a system that can identify only engine knock, not mistake other engine noise for knock and retard quick enough to prevent damage.