Digital Corpus
Top Post Dawg
Which direction would the helix have to be cut? Different direction for 1 & 2 than 3 & 4?
Porting Porn
- Thread starter Franko6
- Start date
SkyRyder55
Veteran Member
- Joined
- Aug 14, 2012
- Location
- Winnipeg, Manitoba, Canada
- TDI
- 1998 Jetta TDI, 1990 Corrado G60 (AHU soon)
and here i thought smooth laminar flow was where it was at.
Digital Corpus
Top Post Dawg
I've not posted this up in my other threads, but if memory serves me well on this topic, the kinematic viscosity or air is nearly same as honey. That is, viscosity proportional to density. Once air is moving faster than about your average jogging/running speed, it is only ever turbulent. However, chocked flow is the actual flow problem that arises with intercooler piping or what have you.
john.jackson9213
Top Post Dawg
As I understand it, engineers want the air swirling and to tumble into the combustion chamber to assure a mixture of air/fuel that burns properly, with minimum emission issues. That is why the TDI has a ridge just below the valve. Eliminate that ridge for better flow, gets you a dirtier engine, more unburned fuel (and less actual power).
Digital Corpus
Top Post Dawg
At low speeds, 1750 RPM or lower though some say 2K and others 1.5K, John I right. For performance at higher RPM, the swirl bump is in the way.
minis2003
Veteran Member
after looking on youtube and web searching i found this
youtube.com/watch?v=WPXeM4EhZnA
and then i started to read
http://www.enginebuildermag.com/2010/04/understanding-port-swirl-in-diesel-engines/
and then my head started to hurt
so i am glad to see smarter people then i, that are working on how to improve the efficiency of our little diesel engines.
youtube.com/watch?v=WPXeM4EhZnA
and then i started to read
http://www.enginebuildermag.com/2010/04/understanding-port-swirl-in-diesel-engines/
and then my head started to hurt
so i am glad to see smarter people then i, that are working on how to improve the efficiency of our little diesel engines.
CNGVW
Vendor , w/Business number
- Joined
- Sep 15, 2009
- TDI
- Many TDI Jettas and a Beetle Race car run 2010 jetta tdi cup car build roadrace
Do you have any dyno or emission testing to back up this claim?
The port design in the ALH is build to produce the swirling in to the port.
The ridge is just the lack of finished machining cost saving.
The port design in the ALH is build to produce the swirling in to the port.
The ridge is just the lack of finished machining cost saving.
john.jackson9213
Top Post Dawg
Bob,
Appreciate the correction of my terminology. "Ridge" was perhaps a poor term. Others understood I was actually refering to the "swirl bump".
Have you noticed any significant buildup? I've got an idea rattling around in my nut that says they keep the ports in the (water cooled aluminum) head small to keep velocity up and keep buildup from occurring, whereas the exhaust manifold is significantly larger, but it runs at a much higher temperature, burning off the soot in the oxidizing atmosphere that diesel exhaust is.
That said, my exhaust ports in the head are now just as big as the ports in the manifold for a smooth transition. Funny how that works once you start up the die grinder.
Franko6
Vendor , w/Business number
Honestly, when I 'stir the pot' by introducing helical cuts, that is not what I will be attempting. A matter of fact, when we were building large volume tanks several years ago, we would put blocking plates against the drain holes to keep a vortex from happening. Fluid dynamics are fundamentally the same. whether it be air or liquid. I do not know if helix should be an interest, as in our experience, keeping the vortice from happening in a large fluid tank made the tank empty substantially faster. Helix's might be a crazy fad.
DJGonzo
Veteran Member
Is the swirl bump still present in PD motors? If so, is it really as necessary as the VE motors?
vanbcguy
Veteran Member
The point is to keep the air moving as much as possible so that the air consumed by the fuel burning is replaced with unburned air around the tip of the injector. Changing the method of injection doesn't alter that.
DJGonzo
Veteran Member
IMO changing the method of injection could very well alter how *effective* the swirling is.
For example, the IDI motors do not have this as the method of injection is different. I'm not even sure if gas direct injected motors even feature this on their head.
The combustion chamber (or rather bowl) in the piston changes between VE and PD motors. So without knowing all the details, I ask how necessary it is for a PD motor. Maybe I should've worded my question differently: Will a reduced /removed swirl bump really make driveability suffer on a PD motor just as much as a VE motor?
vanbcguy
Veteran Member
IDI engines have a very different method of generating swirl, but they rely even more heavily on it than DI engines do. The same principle applies, if the air was static and not moving the burn would be terrible. IDI engines generate swirl in their prechamber based on its shape and the piston forcing air in to it.
Different methods of injection will have different requirements for how the fresh air gets to where the fuel is being burned, but no matter what you need fresh unburned air to burn the fuel.
Different methods of injection will have different requirements for how the fresh air gets to where the fuel is being burned, but no matter what you need fresh unburned air to burn the fuel.
Franko6
Vendor , w/Business number
Sorry for the big delay... I catch flak for being that way...time is precious.
I'll respond inside your quotes:
I'll respond inside your quotes:
Since I was drawn in by the title and entirely satisfied with the shiny things, I'll pitch in with a couple of questions
I always understood (probably from David Vizards book iirc) that the port wall should still be slightly rough in order to promote turbulence and keep the atomised fuel in suspension in the air charge. A polished wall would allow the fuel to condense on the surface and so not work as well. This is obviously carburetted or port-injected gasoline engine theory. Would this be relevant in any way to a diesel engine? Or, would a nice smooth port promote better airflow and the swirl nub sort out the turbulence?The velocity of air is disturbed by any surface. The theory of a roughened surface reduces the size of the vortices. As simply put as possible, a smooth face can create large vortices. The question is the size of the pattern on the walls of the bore. The intent is to cause a very close vortice that is predictably small. The smaller the vortice and closer to the wall, the more air that will flow lanier. Any surface is going to cause air friction. The point would be to reduce that friction by surface design.
Also, Frank - you mentioned taking the swirl nub out for maximum airflow on a race engine. I've been unable to find anything useful on the Googles for what effect this would actually have on the engine, only that its not desirable on a road engine. The 'nub' you describe is actually a 'corner'. At least, when we are porting for best effect swirl, and knowing that the builder's goal are generally creating a lot more power and the related heat, we become sensitive to the manufacturing error built into the intake ports. There is a very right-angle point at the bottom of the intake swirl, close to the intake seat. This is a location for propagating a crack, which is unfortunately close to the water jacketing. Although applying a radius to the internal corner interrupts the air flow for best swirl, it is a compromise that we feel is mandated. Better a bit less flow than a cracked head.As I'm building a race car with a TDI I'm curious to know what characteristics a max-airflow no-swirl head might create if you (or any of the experts) would care to elaborate please?Removing the swirl chamber is not about efficiency. It is about raw volume and anybody that has seen a pulling tractor's injection pump flow, it is like a fire hose going off. There are no rules. How much can you cram into the hole? This is a study of it's own that we will not likely participate in. Our thoughts are as CNGVW states,"Grind and test"
Franko6
Vendor , w/Business number
The 'bump' in the swirl chamber only for the PDs and is all about reducing a cracking hazard and NOTHING to do with improving the swirl chamber. The problem is the unfortunate proximity for the injector bore to the intake seat.
At the closest point, there is about 1/8" of aluminum under the intake seat that separates the injector from the intake port. We have repaired cylinder heads that blew out metal from under the seat, which returns exhaust gasses into the intake port. Not good... The bump in the intake port is there to attempt to arrest any advance of the crack, which can proceed clear to the injector seal area. We have no 'fix' for this problem. It is VAG's 'patch-workaround' for a cylinder head that has an engineering error.
Franko6
Vendor , w/Business number
DJGonzo is referring to the intake port 'bump'. If you look at several castings, you will see that VW does this relatively often. The CBEA and CJAA have the same wall thickening to protect against cracks.
I would not remove the intake port bump in any of these engines, as it is a 'patch' against crack failure. There is already too much of an incident of cracks going up the injector hole.
But I am interested in your thoughts, Rub87. Please elaborate.
I would not remove the intake port bump in any of these engines, as it is a 'patch' against crack failure. There is already too much of an incident of cracks going up the injector hole.
But I am interested in your thoughts, Rub87. Please elaborate.
deejaaa
Veteran Member
I liked the pics and thanks for the pleasure.
Did you ever put a head on flow bench and measured exh flow and then removed bump and measured again?
The fact is that the 90 deg bend is too sharp and the air does not stick to the inner radius. You will see that on the bottom of the port the air is actually flowing back inside. The bump is there to direct the flow in the direction of the runner. You can visualize it easily if you take a piece of thin wire with a short piece of linnen wire on the end.
Same apllies to useless alh and pd style inlets, the 90deg bend is so sharp that it makes the air at the roof from the port stand still. It reduces flow but increases swirl quite a bit. Take a stock port with pd150 ma i and then measure same with sdi or d24 intake. At medium to high lift there is a big difference in swirl/flow tradeoff.
Not ported, but molds of stock ports.
And I took some video of phenomenon what Rub mentioned.
Added some solvent to the mouth of TDI exhaust port when blowing from cylinder side with 28" of water depression:
https://youtu.be/1n6tPUnqg-U
And I took some video of phenomenon what Rub mentioned.
Added some solvent to the mouth of TDI exhaust port when blowing from cylinder side with 28" of water depression:
https://youtu.be/1n6tPUnqg-U
turbovan+tdi
Top Post Dawg
- Joined
- Mar 23, 2014
- Location
- Abbotsford, BC.
- TDI
- 2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
Nice work guys. What is the deal with the PD intake being split? Any harm running an ALH intake?
I have measured more flow with ALH type manifold in flowbench than d24.. but d24 makes better HP =)
Like Rub says, air separates from inner curve and detaches after shortside.
OEM puts restriction upwards to reduce the separation.
Adding pipe when flowing would fix that issue when ported correctly and flow would increase (at least what I have tested) 10+cfm at max lift.
So like Rub said.. using more area of port =)
Like Rub says, air separates from inner curve and detaches after shortside.
OEM puts restriction upwards to reduce the separation.
Adding pipe when flowing would fix that issue when ported correctly and flow would increase (at least what I have tested) 10+cfm at max lift.
So like Rub said.. using more area of port =)
turbobrick240
Top Post Dawg
- Joined
- Nov 18, 2014
- Location
- maine
- TDI
- 2011 vw golf tdi(gone to greener pastures), 2001 ford f250 powerstroke
I happen to have a d24 manifold attached to its 60hp lump in my yard. I find it somewhat amusing that such a good manifold is on that gutless motor. Is the sdi manifold generally considered better/worse for high power applications? Obviously the d24 would need some cutting/welding.
turbovan+tdi
Top Post Dawg
- Joined
- Mar 23, 2014
- Location
- Abbotsford, BC.
- TDI
- 2003 TDI 2.0L ALH, auto, silver wagon, lowered, Colt stage 2 cam, ported head,205 injectors, 1756 turbo, Malone 2.0, 3" exhaust, 18" BBS RC GLI rims. 2004 blue GSW TDI, 5 speed, lowered, GLI BBS wheels painted black, Malone stage 2, Aerotur
What's a D24 manifold?
Lets say stock to stock, PD or ALH? Its a BEW going into a 4 Runner.
Lets say stock to stock, PD or ALH? Its a BEW going into a 4 Runner.