I don't know much anything about intake plenums, but I wonder why no-one seems to made these two modifications?
1) Connect EGR port to the back of the plenum 2) Remove ridges between two side-by side runners
Reasoning: 1) When you look this picture you can see that the restriction is after EGR port, so if one have already removed EGR, why not drill a hole in the back of the plenum (there even seems to be a ready place that waits for a hole?) and connect that with proper hose to the the EGR tube port, and let the plenum take air from both sides.
2) All dual tb versions, Camarobird 3.4 and many modified Fiero plenums do not (much) upper plenum runners, so why not connect the two runners from both sides that are easy to connect?
Suggested mods 1) tube connecting EGR port to the new hole in the back (black) 2) Cut the ridge between runners, 2 centimeters deep or so (white)
[This message has been edited by Timantt1 (edited 01-12-2012).]
Moving EGR will cause problems... Stock location, all cyl's get same air/fuel/EG mixture. Your location Cyl's 1 & 2 get more EG then others. When ERG is active then cyl's sees unbalance mixture to burn. Not good.
quote
2) Remove ridges between two side-by side runners
Remove/alter the runners can affect Port FI negatively even if flow bench says you alt can move more air. Port FI like equal air path on intake.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Originally posted by theogre: Moving EGR will cause problems... Stock location, all cyl's get same air/fuel/EG mixture. Your location Cyl's 1 & 2 get more EG then others. When ERG is active then cyl's sees unbalance mixture to burn. Not good.
Remove/alter the runners can affect Port FI negatively even if flow bench says you alt can move more air. Port FI like equal air path on intake.
I mean that if the whole EGR system is removed and blocked off, the EGR port is useless, then why not connect it to the back of the plenum to create a secondary route for fresh air to get in.
Obviously, EGR port is so small that this secondary route could only move some 10-20% of the total air flow, even if you drill that hole little wider, but one would imagine it would help to overcome some of that neck restriction.
Removing the wall between two runners just above the middle plenum connection was just an idea to decrease air flow resistance if four of the cylinders could use two upper plenum runners to suck air. Probably not a good idea since no-one has done it.
[This message has been edited by Timantt1 (edited 01-11-2012).]
I think it would be really hard to remove the wall completely. Not sure how you would really even get in there. Best way would be to cut the whole thing open... at that point make the whole upper plenum have no runners, make it one big box. Shorter runners with more volume is more HP. Though TQ will suffer. I have been fighting with that balance b/w tq and hp with my 3.4. I can get enough air in. At the rear wheels HP sits at the 145 mark while tq is in the 260s, but the tq drops off too quick (peaking at 2500)... grr... With a good tune I had hoped the HP would climb. Just waiting & waiting & waiting to get the car back together now...
------------------ Rescued & resuscitated 1984 Indy Fiero SE Pace Car Replica #770 presently reversibly modified! SE: Stormtrooper Edition
I mean that if the whole EGR system is removed and blocked off, the EGR port is useless, then why not connect it to the back of the plenum to create a secondary route for fresh air to get in.
Obviously, EGR port is so small that this secondary route could only move some 10-20% of the total air flow, even if you drill that hole little wider, but one would imagine it would help to overcome some of that neck restriction.
Removing the wall between two runners just above the middle plenum connection was just an idea to decrease air flow resistance if four of the cylinders could use two upper plenum runners to suck air. Probably not a good idea since no-one has done it.
Not really worth the effort, I'm pretty sure it would do more damage to flow then any good.
I mean that if the whole EGR system is removed and blocked off, the EGR port is useless, then why not connect it to the back of the plenum to create a secondary route for fresh air to get in.
Obviously, EGR port is so small that this secondary route could only move some 10-20% of the total air flow, even if you drill that hole little wider, but one would imagine it would help to overcome some of that neck restriction.
Seeing as you're from Finland, I don't know if this is a language issue (your English is good though), but your idea for the EGR makes no sense at all. If the "whole EGR system is removed", what point is there in drilling a hole on the other side of the plenum? You can't have an unmetered "secondary route for fresh air to get in". All that'll accomplish is a high idle speed.
Seeing as you're from Finland, I don't know if this is a language issue (your English is good though), but your idea for the EGR makes no sense at all. If the "whole EGR system is removed", what point is there in drilling a hole on the other side of the plenum? You can't have an unmetered "secondary route for fresh air to get in". All that'll accomplish is a high idle speed.
EGR port in the neck is after the throttle body, so connecting this EGR port to the new hole in the back of the plenum with tube would not increase idle, since all air would still go trough the throttle body. Of course this tube must be sealed so that outside air would not leak from the connecting points, it could be something similar as EGR tube (maybe larger diameter), but going from the neck to the back of the plenum, instead of exhaust. This would create a secondary route for air to enter the plenum, most of the air would go normal way, but 10-20% of air would circulate from EGR port in the neck to the back of the plenum through that secondary route tube.
Removing ridges between runners would be relatively easy if you just cut a couple of centimeters, so that two upper plenum runners would be connected only just above the middle intake.
But, as I said i know nothing about plenums and how they are designed, but just though that these relatively easy mods would increase the air flow.
[This message has been edited by Timantt1 (edited 01-12-2012).]
EGR port in the neck is after the throttle body, so connecting this EGR port to the new hole in the back of the plenum with tube would not increase idle, since all air would still go trough the throttle body. Of course this tube must be sealed so that outside air would not leak from the connecting points, it could be something similar as EGR tube (maybe larger diameter), but going from the neck to the back of the plenum, instead of exhaust. This would create a secondary route for air to enter the plenum, most of the air would go normal way, but 10-20% of air would circulate from EGR port in the neck to the back of the plenum through that secondary route tube.
Okay okay, after looking at your diagram again and reading your last post, I now understand what you're saying. Instead of running a narrow tube to the back of the plenum for the fresh air to then enter a small hole, why not drill out the existing EGR hole in the neck of the manifold and run a larger tube to the center of the underside of the plenum. That would at least help equalize the air flow to all runners somewhat. Or it might not. Could cause some pretty funky flow patterns, especially around the entrance to the original EGR hole in the manifold neck. Interesting concept though. Let's get 'er on a flow bench!
[This message has been edited by Patrick (edited 01-12-2012).]
Ok, confused here on this discussion? Maybe I'm just not following what you are trying to accomplish? The EGR allows exhaust gas to enter the intake, how does fresh air come into play? EG does not re-burn so why would we want more EG?
Removing the current "lug" where the EGR hooks to on the upper plenum would allow a larger area for a better transition piece to be welded in. If I recall the Dawg manifold is like this? The one I tested had the EGR port still there.
My personal feeling on the upper intake is flow distribution within the plenum area along with what I already saw from this testing. I think cylinders are going lean at higher rpm's simply because they are not "seeing air" as other runners are taking it away. Hence a lean condition to those cylinders. Only way you are going to see this is EGT testing on each cylinder.
Sorry to say this project has taken a back seat for me right now as I had back surgery in October and have not had a chance to start playing with a cylinder head. I'm still trying to get caught up on back orders for my business so personal playing on my flowbench is not happening right now. Hope to get some testing done in the next few weeks . . . glad to see a renewed interest in this topic though!
------------------ "There is no more formidable adversary than one who perceives he has nothing to lose." - Gen. George S. Patton http://www.flowbenchtech.com
Ok, confused here on this discussion? Maybe I'm just not following what you are trying to accomplish? The EGR allows exhaust gas to enter the intake, how does fresh air come into play? EG does not re-burn so why would we want more EG?
I was confused initially as well. Ya gotta think out of the box...
Take a look at the following image. There are NO exhaust gases, as there is no EGR assembly. The (black) tube is to (possibly) help bypass the restriction of the intake neck and to allow added air flow (of fresh air) to the back of the plenum. Comprende?
Off the top of my head . . . since both ends of the tube see the same manifold pressure, there is no differential pressure to get the air to move. So no airflow will take place inside the tube the way I see it, might see a little difference at times maybe but nearly not enough to do anything worthwhile. As someone stated earlier not worth the effort the way I see it.
Air flows from areas of high pressure to areas of low pressure you need both to make the NA intake system work.
------------------ "There is no more formidable adversary than one who perceives he has nothing to lose." - Gen. George S. Patton http://www.flowbenchtech.com
. . . since both ends of the tube see the same manifold pressure...
But do they? One end of the tube is just before the restriction in the neck of the manifold (where air flow is being impeded), and the other end is at the back of the manifold where there is the full unimpeded "suck" from the cylinders.
I have some doubts as well with this idea, but it would still make for an interesting physics experiment.
I think it would be really hard to remove the wall completely. Not sure how you would really even get in there. Best way would be to cut the whole thing open... at that point make the whole upper plenum have no runners, make it one big box. Shorter runners with more volume is more HP. Though TQ will suffer. I have been fighting with that balance b/w tq and hp with my 3.4. I can get enough air in. At the rear wheels HP sits at the 145 mark while tq is in the 260s, but the tq drops off too quick (peaking at 2500)... grr... With a good tune I had hoped the HP would climb. Just waiting & waiting & waiting to get the car back together now...
This is exactly what the intake of the PPG cars do and it produces 40 more hp.
I don't know much anything about intake plenums, but I wonder why no-one seems to made these two modifications?
1) Connect EGR port to the back of the plenum 2) Remove ridges between two side-by side runners
Reasoning: 1) When you look this picture you can see that the restriction is after EGR port, so if one have already removed EGR, why not drill a hole in the back of the plenum (there even seems to be a ready place that waits for a hole?) and connect that with proper hose to the the EGR tube port, and let the plenum take air from both sides.
2) All dual tb versions, Camarobird 3.4 and many modified Fiero plenums do not (much) upper plenum runners, so why not connect the two runners from both sides that are easy to connect?
Suggested mods 1) tube connecting EGR port to the new hole in the back (black) 2) Cut the ridge between runners, 2 centimeters deep or so (white)
In my shaved down intake, you can see how much bigger I made the ports. The only thing I didn't touch was the neck restriction and I was able to maximize the thru-put of my motor to make ~180 HP thru the stock neck. I believe the lower friction of the roller cam block also helped with getting the hp that high as did my full-roller rockers. The curved area of the ports was bowled more to help turn the 135 degree corner that some know-it-alls predicted would kill my performance.
I'm looking forward to the day my stock Formula's 2.8 blows up so I can do another roller cam engine with this old intake again...this time with the DAWG mod. The motor this intake was on now has a Trueleo and twin 48mm L98 V8 throttle body.
[This message has been edited by lou_dias (edited 03-12-2013).]
I got some time today to get a 3.4L stock upper intake on the flowbench for testing. This was just the intake and no throttle body.
It flowed 445@28"
------------------ "There is no more formidable adversary than one who perceives he has nothing to lose." - Gen. George S. Patton http://www.flowbenchtech.com
[This message has been edited by Brucepts (edited 11-27-2013).]
