Rick Engman's Exhaust Port Shape - Thoughts
03-02-2005, 04:59 PM
#62
Senior Member
Join Date: Jun 2003
Location: Grand Prairie, TX
Posts: 917
Originally Posted by bill shurvinton' date='Mar 2 2005, 02:38 PM
reminds me. About a year ago I wondered if you might ever consider sending a couple of your inserts over to this side of the pond so I could try them out in one of my engines...:-)
Hi Fred,
I've got about 18 junk rotor housings. Want a couple of 'em to screw around with?
B
03-02-2005, 05:21 PM
#63
Senior Member
Thread Starter
Join Date: Oct 2004
Posts: 110
Originally Posted by BDC' date='Mar 2 2005, 03:58 PM
Hi Fred,
I've got about 18 junk rotor housings. Want a couple of 'em to screw around with?
B
I've got about 18 junk rotor housings. Want a couple of 'em to screw around with?
B
If these don't work I will have some junk ones as well. Just took a few more picks before I packed them up. These ports are big. I tapered the exhaust port out to 2 inches in diameter and will match my primaries to it.
CW
03-02-2005, 05:30 PM
#64
Senior Member
Thread Starter
Join Date: Oct 2004
Posts: 110
Originally Posted by BDC' date='Mar 2 2005, 03:58 PM
Hi Fred,
I've got about 18 junk rotor housings. Want a couple of 'em to screw around with?
B
I've got about 18 junk rotor housings. Want a couple of 'em to screw around with?
B
Brian, if you make it out to CO this spring, how do you feel about tuning an engine with these housings?
03-02-2005, 06:36 PM
#65
Member
Join Date: Nov 2002
Posts: 92
no we don't create a ledge, we open up exh. port exit to the exact shape of the flange. everyone found out a long time ago that you can't disrupt the laminar flow that close to the head or the flow and velocity go to ****, which will happen if you use a ledge right at the port/flange interface. all the pro rwd teams already have their own anti-reversion features built into the exhaust manifold, there's no need for a lege. fwiw i know what a venturi is, the restriction is exh. port inlet, which he can't really port out more unless he really wants to screw up his port timing. since he can't really do anything about that, as a compromise he can use a divergent taper downstream of the restriction to help draw out the exhaust. and why are you bringing up n/a setups, we're talking about a turbo app here. i'm sure your sleeves are great, you should have great success w/ them.
Originally Posted by rotarygod' date='Mar 2 2005, 01:44 PM
Going up from 1 7/8" to 2" isn't a big jump in size and very little loss in velocity. What it did do was to create a slight ledge which helps reduce reversion pulses from entering the engine. Try jumping up to a 2 1/4" and see what happens to the powerband. Luckily for them, a turbo system is very tolerant to flow changes before the turbo and you can still get good power numbers. Try these changes on a nonturbo car that depends on exhaust flow and see what happens. The small size adjustment they made did nothing for venturi effect. FWIW a venturi is a restriction and you are limited with it. Carbs don't use venturis because they flow more. They use them because the pressure change through them is caused by an airspeed change through them and this helps to get the very poorly atomized low pressure fuel flowing and distributed better. If you were to remove the venturi (and obviously the carb) and replaced it with a fuel injection system and tune it properly, it would get more power.
Other things happen in exhausts in regards to pipe size changes but none of this is due to a venturi. Some people used stepped headers. These take advantage of acoustic pulses at certain frequencies. An expanding collector such as a megaphone also benefits as this also strengthens the acoustic effect in the exhaust system. In order for a venturi to work properly, it's shape has to be designed properly. You don't get it done by just changing the area at random spots.
I do have ask this so don't take it personally. I'm not trying to be an ***. Are you quoting theory or have you actually tested and tried any of these different systems for yourself? I've run my sleeves for years. I know how well they work vs the stock ones.
Other things happen in exhausts in regards to pipe size changes but none of this is due to a venturi. Some people used stepped headers. These take advantage of acoustic pulses at certain frequencies. An expanding collector such as a megaphone also benefits as this also strengthens the acoustic effect in the exhaust system. In order for a venturi to work properly, it's shape has to be designed properly. You don't get it done by just changing the area at random spots.
I do have ask this so don't take it personally. I'm not trying to be an ***. Are you quoting theory or have you actually tested and tried any of these different systems for yourself? I've run my sleeves for years. I know how well they work vs the stock ones.
03-02-2005, 06:42 PM
#66
Member
Join Date: Nov 2002
Posts: 92
Originally Posted by z8cw' date='Mar 2 2005, 03:20 PM
If these don't work I will have some junk ones as well. Just took a few more picks before I packed them up. These ports are big. I tapered the exhaust port out to 2 inches in diameter and will match my primaries to it.
CW
CW
that should work great, you gonna use your existing manifold? what size turbo you gonna run?
03-02-2005, 07:29 PM
#67
Senior Member
Thread Starter
Join Date: Oct 2004
Posts: 110
Originally Posted by fdracer' date='Mar 2 2005, 05:42 PM
that should work great, you gonna use your existing manifold? what size turbo you gonna run?
Thanks,
No everything is going to be redesignd. I currently have a HKS knock off. The turbine I will try next will be a to4 1.15 AR with a large center (45) to accomodate the big shaft t series compressors. I haven't decided on the wheels yet.
03-03-2005, 08:33 AM
#68
Senior Member
Join Date: Dec 2003
Posts: 162
Originally Posted by fdracer' date='Mar 2 2005, 04:35 PM
no we don't create a ledge, we open up exh. port exit to the exact shape of the flange. everyone found out a long time ago that you can't disrupt the laminar flow that close to the head or the flow and velocity go to ****, which will happen if you use a ledge right at the port/flange interface. all the pro rwd teams already have their own anti-reversion features built into the exhaust manifold, there's no need for a lege. fwiw i know what a venturi is, the restriction is exh. port inlet, which he can't really port out more unless he really wants to screw up his port timing. since he can't really do anything about that, as a compromise he can use a divergent taper downstream of the restriction to help draw out the exhaust. and why are you bringing up n/a setups, we're talking about a turbo app here. i'm sure your sleeves are great, you should have great success w/ them.
Now I have forgotten an awful lot about flow since university, but ISTR that a rapid expansion (such as in a rotary exhaust port) will tend to make a laminar flow turbulent. Early rotary ports were straight holes after all, but the story I have read ( and have no proof of its truth) is that the divergent design was introduced to add turbulence and reduce noise, more so in NA setups where the splitter is involved.
Certainly not having fast expansion at the head makes sense to me, esp in a turbo setup where you want to keep/get the flow close to supersonic as it exits the nozzle in the turbo, but I need to tap some friends who still remember the detail of high speed flow mechanics
03-05-2005, 05:09 PM
#70
Senior Member
Thread Starter
Join Date: Oct 2004
Posts: 110
Originally Posted by rx7tt95' date='Mar 5 2005, 03:04 PM
Take a look at the exhaust ports on my engine. Not yet finished (obvious). Comments welcome.
Check the earlier pics. It seems that general consensus is that your opening eadge is round versus your closing edge being straight. You have that reversed. The whole threat started with looking at Rick Engmanns ports which are that way.
CW