Single vs Dual Plane vs Stealth Ram
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From: Nashville
Single vs Dual Plane vs Stealth Ram
I know the basics from what i have found on the net...
Stealth Ram is all around good but is listed to only make power to 6k.
Dual Planes are better for torque, street cars, and making power lower in the rpm range.
And single planes are more race oriented making more HP, makes its power higher in the rpm range.
Anyone care to further indulge on these intake designs? Thanks
Stealth Ram is all around good but is listed to only make power to 6k.
Dual Planes are better for torque, street cars, and making power lower in the rpm range.
And single planes are more race oriented making more HP, makes its power higher in the rpm range.
Anyone care to further indulge on these intake designs? Thanks
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Joined: Oct 2002
Posts: 6,518
Ken,
The stealth ram is a basically a tunnel ram turned into a EFI maifold. The man advantages of a tunnel ram are the big pleanums, straight shot from the carb to the head port and usually long runners.
A dual plane manifold for a carburated engine has better throttle response and better low rpm capabilities due to the split pleanum. It doesn't make any sense on a EFI setup.
A single plane is normally labeled as a race manifold, but it can be very effective on street cars with carbs and EFI. The larger pleanum helps at high rpm and they usually have better flowing runners to help HP production. The runner lengths can be short like a Vic Jr or long like a Super Vic. Also the cross sectional area is going to be bigger on most single plane setups.
Bret
The stealth ram is a basically a tunnel ram turned into a EFI maifold. The man advantages of a tunnel ram are the big pleanums, straight shot from the carb to the head port and usually long runners.
A dual plane manifold for a carburated engine has better throttle response and better low rpm capabilities due to the split pleanum. It doesn't make any sense on a EFI setup.
A single plane is normally labeled as a race manifold, but it can be very effective on street cars with carbs and EFI. The larger pleanum helps at high rpm and they usually have better flowing runners to help HP production. The runner lengths can be short like a Vic Jr or long like a Super Vic. Also the cross sectional area is going to be bigger on most single plane setups.
Bret
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by got_hp?
kind of along the same topic..........how effective would a custom manifold like this be?
kind of along the same topic..........how effective would a custom manifold like this be?
It's basically a "log" plenum with short runners to the head which are just welded onto the plenum. (I turned the picure upside down to look
) IMO, the transition from the log to the runners should be smooth or a radius, not sharp, even for boost. I'd probably connect the plenums at the rear. It does look cool however, which might be the rationale for this engine. Separate plenums for each bank on an NA engine have different characteristics from single plenum (LT1, LS1, etc.) manifolds. It's something like dual plane vs. single plane manifolds.
I don't like to generalize on what a certain type manifold will do. Dual planes (DP) generally have smaller, and longer and bent runners vs. single planes (SP), so they tune at lower rpm (torque). But this isn't always the case. Some DPs have some very short runners vs. short-runner SP (V-Jr. , and some have runners about the same length as a S-Vic, as Bret said. The smaller runner area of many DPs keeps the velocity up both for throttle response and good VE around torque peak, but some of the latest DPs have runners similar in length and area to SPs. RPM Air Gaps come to mind.
In most cases, DPs have quite a diference in runner lengths in the same manifold. Many folks think this is a tuning negative, but if you think of it as two or three tuning lengths, with different cylinders peaking at different rpms, you can broaden the torque (and hp) curves at the possible expense of "peak" numbers. Of course, you could size (area) each length runner for it's particular rpm, but I don't think there is too much of that in the normal aftermarket DP.
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Joined: Jun 2003
Posts: 584
I like single planes on street/strip cars because generally they push the torque curve up in the RPM range.
Many people would say "you want low end torque on the street". In theory if your street tires are ET streets that would make sense (or if its a daily driver), but on a true street strip car you will have less traction problems on street tires with the torque curve further up in the RPM band (and we all know traction decides the majority of street races). On the same note, most people run such a loose converter in their street/strip cars that they wont even see the RPM ranges where a dual plane would benefit them.
I run an 82 Camaro on 275/50/15 BFG Radial T/A tires and run 12.4's @ 110+ with a super victor on a fairly mild 350.
Many people would say "you want low end torque on the street". In theory if your street tires are ET streets that would make sense (or if its a daily driver), but on a true street strip car you will have less traction problems on street tires with the torque curve further up in the RPM band (and we all know traction decides the majority of street races). On the same note, most people run such a loose converter in their street/strip cars that they wont even see the RPM ranges where a dual plane would benefit them.
I run an 82 Camaro on 275/50/15 BFG Radial T/A tires and run 12.4's @ 110+ with a super victor on a fairly mild 350.
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Joined: Oct 2003
Posts: 93
Originally posted by SStrokerAce
Ken,
A dual plane manifold for a carburated engine has better throttle response and better low rpm capabilities due to the split pleanum. It doesn't make any sense on a EFI setup.
Bret
Ken,
A dual plane manifold for a carburated engine has better throttle response and better low rpm capabilities due to the split pleanum. It doesn't make any sense on a EFI setup.
Bret
Btw: Accel, Holley and Edelbrock (and maybe others) all make multi-port DP EFI manifolds, and from what I've seen they all make comparable power and response to their carb'ed relatives. However, if you're building from scratch, the EFI system (and all it's components) will cost you many times what it would cost to slap on a carb and call it done. If both setups are making comparable power, it might be hard to justify EFI's benefits at moderate power levels.
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Joined: Jul 2000
Posts: 520
From: MD
Huh… I didn’t realize that the SuperVictor had longer runners.
WRT to the DP/180* manifold, it’s not the firing order… to accomplish that you’d have to have one runner from each side cross over to the opposite side. As far as I’ve seen, no DP manifolds do that.
As far as I know, the reason for the divided plenum is for better responsiveness and better signal to the carb by decreasing the plenum volume that each cylinder has to act on.
I’m still not following why converting an DP to work with FI is a problem… if the runner dimensions are what you’re looking for then why not? It’s not overly hard to cut out the plenum divider if that’s what you decide is what you want, but at the same time, you can just extend the plenum size buy building an appropriately dimentioned TB adaptor.
WRT to the DP/180* manifold, it’s not the firing order… to accomplish that you’d have to have one runner from each side cross over to the opposite side. As far as I’ve seen, no DP manifolds do that.
As far as I know, the reason for the divided plenum is for better responsiveness and better signal to the carb by decreasing the plenum volume that each cylinder has to act on.
I’m still not following why converting an DP to work with FI is a problem… if the runner dimensions are what you’re looking for then why not? It’s not overly hard to cut out the plenum divider if that’s what you decide is what you want, but at the same time, you can just extend the plenum size buy building an appropriately dimentioned TB adaptor.
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by WS6 TA
Huh… I didn’t realize that the SuperVictor had longer runners.
WRT to the DP/180* manifold, it’s not the firing order… to accomplish that you’d have to have one runner from each side cross over to the opposite side. As far as I’ve seen, no DP manifolds do that.
Right. DP's usually pair SBC cylinders 2-3-5-8 on the upper plenum and 1-4-6-7 on the lower. That makes the firing pulses on the odd bank 270* (1-3), 180* (3-5) and 90* (5-7) apart.
On the even bank it's 450* (2-4), 180* (4-6), and 270* (6-8) apart.
As far as I know, the reason for the divided plenum is for better responsiveness and better signal to the carb by decreasing the plenum volume that each cylinder has to act on.
And maybe trying to get more equal runner lengths. Shortest on the ZZ4 DP is about 3.5 inches, and longest about 5.3 inches. All the runners on a 2925 Super Vic are about 5.5 in at center of runner.
I’m still not following why converting an DP to work with FI is a problem… if the runner dimensions are what you’re looking for then why not? It’s not overly hard to cut out the plenum divider if that’s what you decide is what you want, but at the same time, you can just extend the plenum size buy building an appropriately dimentioned TB adaptor.
Huh… I didn’t realize that the SuperVictor had longer runners.
WRT to the DP/180* manifold, it’s not the firing order… to accomplish that you’d have to have one runner from each side cross over to the opposite side. As far as I’ve seen, no DP manifolds do that.
Right. DP's usually pair SBC cylinders 2-3-5-8 on the upper plenum and 1-4-6-7 on the lower. That makes the firing pulses on the odd bank 270* (1-3), 180* (3-5) and 90* (5-7) apart.
On the even bank it's 450* (2-4), 180* (4-6), and 270* (6-8) apart.
As far as I know, the reason for the divided plenum is for better responsiveness and better signal to the carb by decreasing the plenum volume that each cylinder has to act on.
And maybe trying to get more equal runner lengths. Shortest on the ZZ4 DP is about 3.5 inches, and longest about 5.3 inches. All the runners on a 2925 Super Vic are about 5.5 in at center of runner.
I’m still not following why converting an DP to work with FI is a problem… if the runner dimensions are what you’re looking for then why not? It’s not overly hard to cut out the plenum divider if that’s what you decide is what you want, but at the same time, you can just extend the plenum size buy building an appropriately dimentioned TB adaptor.
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Joined: Jul 2000
Posts: 520
From: MD
Originally posted by OldSStroker
And maybe trying to get more equal runner lengths. Shortest on the ZZ4 DP is about 3.5 inches, and longest about 5.3 inches.
And maybe trying to get more equal runner lengths. Shortest on the ZZ4 DP is about 3.5 inches, and longest about 5.3 inches.
All the runners on a 2925 Super Vic are about 5.5 in at center of runner.
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Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Originally posted by WS6 TA
If that’s what they were shooting for I would expect them to run the outside runners from the near side of the plenum and then center 2 runners from the opposite side… I bet that would give you nearly even runner lengths.
That's exactly how they are made. I have a GM10185063 and a 2925 SuperVic sitting here. The shortest DP runners are from the lower plenum, even the outboard ones (1 & 7).
They’re that close? I would have expected the center runners to be significantly shorter then the end runners…. Huh, I wish I had one of each sitting here, this is actually very interesting. I’d love to know what the average runner volume was on each, since sounds like the DP averages about 4.4” runner length vs5.5 on the SP, suggesting that the SP should actually be tuned to a lower frequency (rpm) then the DP assuming the same size average runner cross section. Since testing doesn’t usually show that, I would guess that the SP runner is significantly larger. If not, then it would suggest a much stronger relationship between power band and plenum volume then most people care to entertain.
At the plenum the SP (2925) has about 3.2-3.3 sq in area with a height near 3 inches and a width slightly over 1 inch. The DP has more rectangular openings with areas closer to 2.8 sq in.
If well-ported heads have approx. 2.6 sq in area at the manifold flange, you have a runner taper of perhaps 2 degrees with the 2925.
With stock ports of approx 2.0-2.1 sq in at the flange, there is some taper in the stock DP, but if you match it to ported heads, you lose the taper. I don't have a Performer RPM air gap here, but I suspect the ports are a tad larger, and a little straighter because it's taller, but the multiple turns are still there.
IMO, the nearly straight shot from the plenum to the head is a big advantage of the SP. The maximum turn is about 45 degrees horizontally. Vertically it's almost a continuous smooth large radius curve. Looking down the runner from the plenum, you can see 50-80% of the port opening. On the DP, only on 3 & 5 (upper inner runners) can you see any of the port. The lower runners make approx 90 degree horizontal and 45 degree vertical turns with a centerline radius as tight as 2 inches horizontally and tighter vertically. If you think like a slug of air, those tight turns eat up a lot of evergy, IMO.
So taper, and a much straighter runner and equal lenght and similar shaped runners appear to me to be the SP's main advantages. A lot of those same things apply to modern OEM EFI manifolds (LS1, Northstar, etc.). IMO, the DP's advantages are with carbs and part-throttle low rpm (<1000-2500) driving, which is what they were originally designed for. Even with bug sprayer FI, I like SPs.
If that’s what they were shooting for I would expect them to run the outside runners from the near side of the plenum and then center 2 runners from the opposite side… I bet that would give you nearly even runner lengths.
That's exactly how they are made. I have a GM10185063 and a 2925 SuperVic sitting here. The shortest DP runners are from the lower plenum, even the outboard ones (1 & 7).
They’re that close? I would have expected the center runners to be significantly shorter then the end runners…. Huh, I wish I had one of each sitting here, this is actually very interesting. I’d love to know what the average runner volume was on each, since sounds like the DP averages about 4.4” runner length vs5.5 on the SP, suggesting that the SP should actually be tuned to a lower frequency (rpm) then the DP assuming the same size average runner cross section. Since testing doesn’t usually show that, I would guess that the SP runner is significantly larger. If not, then it would suggest a much stronger relationship between power band and plenum volume then most people care to entertain.
At the plenum the SP (2925) has about 3.2-3.3 sq in area with a height near 3 inches and a width slightly over 1 inch. The DP has more rectangular openings with areas closer to 2.8 sq in.
If well-ported heads have approx. 2.6 sq in area at the manifold flange, you have a runner taper of perhaps 2 degrees with the 2925.
With stock ports of approx 2.0-2.1 sq in at the flange, there is some taper in the stock DP, but if you match it to ported heads, you lose the taper. I don't have a Performer RPM air gap here, but I suspect the ports are a tad larger, and a little straighter because it's taller, but the multiple turns are still there.
IMO, the nearly straight shot from the plenum to the head is a big advantage of the SP. The maximum turn is about 45 degrees horizontally. Vertically it's almost a continuous smooth large radius curve. Looking down the runner from the plenum, you can see 50-80% of the port opening. On the DP, only on 3 & 5 (upper inner runners) can you see any of the port. The lower runners make approx 90 degree horizontal and 45 degree vertical turns with a centerline radius as tight as 2 inches horizontally and tighter vertically. If you think like a slug of air, those tight turns eat up a lot of evergy, IMO.
So taper, and a much straighter runner and equal lenght and similar shaped runners appear to me to be the SP's main advantages. A lot of those same things apply to modern OEM EFI manifolds (LS1, Northstar, etc.). IMO, the DP's advantages are with carbs and part-throttle low rpm (<1000-2500) driving, which is what they were originally designed for. Even with bug sprayer FI, I like SPs.
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