Tanya;934967 said:
Yup, love those big valves. Plus the port design is a lot less anemic. I wouldn't be surprised.
Header/Exhaust System Design
- Thread starter DEFIANT 7M
- Start date
Yup, love those big valves. Plus the port design is a lot less anemic. I wouldn't be surprised.
I was talking to cuel about header vs exhaust manifold not too long ago, and these are the values of the OBX header.
Ports(at head, individual s.s. tubes)) o.d.: 1.513"
Collectors: 2.003"
Pipe from collector to cat.: 2.003"
Those were his measurements. IIRC, pacesetter/OBX are pretty much the same.
Ports(at head, individual s.s. tubes)) o.d.: 1.513"
Collectors: 2.003"
Pipe from collector to cat.: 2.003"
Those were his measurements. IIRC, pacesetter/OBX are pretty much the same.
Ma70.Ent;934980 said:
That being the case then any 5/6M header 1 5/8" primary will cover the needs of 99.9% of the 7M world even me. The hard part is done, no pipe fabing (DARN:biglaugh
DEFIANT 7M;935000 said:That being the case then any 5/6M header 1 5/8" primary will cover the needs of 99.9% of the 7M world even me. The hard part is done, no pipe fabing (DARN:biglaugh
Haha. How about the collectors and other crap after that?
EDIT: Forgot to mention, guys with OBX/pacesetters always have to mess with the o2 sensor location IIRC.
Thank you Tonya for the Trust header information. You have given us a great missing link. A great two into one collector would looks like a wonderfull adition to the Trust header.
http://www.burnsstainless.com/MergeCollectors/2into1base/2into1base.html
Now lets get the collector length right to bring our torque up. Any pics and specs on the DTs
http://www.burnsstainless.com/MergeCollectors/2into1base/2into1base.html
Now lets get the collector length right to bring our torque up. Any pics and specs on the DTs
BF made my merge collector
Should be interesting to see the hp/tq numbers when I finally get the car dyno'd (even though I won't have any comparision dyno #s )
Should be interesting to see the hp/tq numbers when I finally get the car dyno'd (even though I won't have any comparision dyno #s
)
This is why I asked:
"As for the secondary length-that is from about the middle of the collector to the end of the secondary (or the first large change in cross-sectional area), we find a great deal more sensitivity than is seen with the primary. Ironically, few racers pay heed to collector length even though it is easy to adjust. In practice, collector length and diameter can have more effect on the power curve than the primary length. A basic rule on collectors is that shorter, larger diameters favor top end while longer, smaller diameters favor the low end. Except for the most highly developed engines, many collectors I see at the track are too large in diameter and either too short, or of excessive length. For a motor peaking at around 6,000-8,500 rpm, a collector length of 10-20 inches is effective."
"As for the secondary length-that is from about the middle of the collector to the end of the secondary (or the first large change in cross-sectional area), we find a great deal more sensitivity than is seen with the primary. Ironically, few racers pay heed to collector length even though it is easy to adjust. In practice, collector length and diameter can have more effect on the power curve than the primary length. A basic rule on collectors is that shorter, larger diameters favor top end while longer, smaller diameters favor the low end. Except for the most highly developed engines, many collectors I see at the track are too large in diameter and either too short, or of excessive length. For a motor peaking at around 6,000-8,500 rpm, a collector length of 10-20 inches is effective."
Okay my math sucks tonight 1.75 x 1 5/8"...some place over 2.5"?
Reason:
"A good starting point for the collector/secondary pipe size of a simple 4-into-1 header is to multiple the primary diameter by 1.75. Fortunately, the collector can be changed relatively easily and it is often best optimized at the track rather than the dyno."
Reason:
"A good starting point for the collector/secondary pipe size of a simple 4-into-1 header is to multiple the primary diameter by 1.75. Fortunately, the collector can be changed relatively easily and it is often best optimized at the track rather than the dyno."
Ma70.Ent;935113 said:
Nice header! Wish it were bigger:3d_frown:
http://www.dougthorleyheaders.com/products/sfID1/9/sfID2/35/sfID3/39/productID/935
Thanks man:icon_bigg So if we are going to use a Trust header the collector needs to be a 3" one.::hah:: Looks like all those N/A guys running 3" exhaust are on to something! Okay... so far
Stock to mild upgrades: Pacesetter, OBX, DT (1 1/2 primary) with a 2.5" diameter collector.
Cams, Headwork, Comp, Stroke plus stage one upgrades: Thrust (1 5/8 primary) with a 3" diameter collector.
I had about 8" cut off the collector of my Pacesetter, and relocated the O-2 bung closer to the split from 1 to 2. The Pacesetter I installed had the 0-2 bung about 4" from the end of a very long collector and was angled downward. It was the lowest thing protruding from the bottom of the car. Could have easily gotten ripped off if I had run off the road. Not to mention with the angle downward moisture could collect and run into the 0-2 sensor. Dumbest thing I'd seen .
How long should the collector pipe be? Well track or dyno time. Since most of us have to have cats. Lets stay legal the modified way:biglaugh: A good cat can act as a "pressure wave termination box" I'm using a small flow master. The length between the collector and the "pwtb" is your tune on the dyno or track mod! After the "pwtb" your exhaust is somewhat invisible to the engine.
Pressure Waves
With muffler flow requirements out of the way we can move on to methods of applying suitable capacity mufflers to the "system" without needless disruption of length-induced pressure wave tuning. Probably the best way to ease into this somewhat complex subject is to consider some of the published muffler test results done in recent years. These tests appeared to have shown that, sometimes, lower flow mufflers inducing at least some backpressure were required to make best power. In all such tests that I have studied, the conclusions (as apposed to the tests) were invalid. There turns out to be several reasons for this and all are relevant to building a near zero-loss exhaust system.
The first point canceling the supposed validity of back-to-back test results is due to the varied internal designs seen amongst the test pieces Fig. 8. Many mufflers are made up of a number of inter-connected chambers having varying degrees of access ease by the exhaust. Others are of the "glass pack" variety. These types represent opposite ends of a spectrum and have a substantially differing response to arriving pressure waves.
When we dealt with collector length it was emphasized that it was, in most cases, more critical than the primary pipe lengths. Adding a muffler (even one with zero backpressure) to a system with already optimized lengths can alter the pressure wave response such that the tuning is now out of phase with what is required and as a result, power drops. The trick here is to install mufflers such that they don't alter the tuned lengths of the system. Let us assume that the test muffler is attached directly to the end of the collector. A pressure wave is reflected either at the end of the exhaust pipe or when a sizable increase in cross-sectional area occurs. Open chambered mufflers such as Flowmasters often appear to the pressure wave much the same as the end of the pipe. This means the pressure waves see no change in length and reflection occurs largely as it did prior to the fitment of the muffler.
A glass pack muffler can act significantly different. It does not appear as a pipe end but as a substantial increase in collector length. Result: a reduction of power even though there is no measurable backpressure involved. From this we can see that many comparative muffler tests were in fact "pseudo pipe-length" tests. Although many invalid conclusions were drawn, these tests still demonstrated some important facts. The most important is that the engine's needs in terms of flow and pressure wave length tuning must be isolated, one from the other. This is easy to do by means of the pressure wave termination box (resonator box) mentioned earlier. Incorporating a resonator box into a system produces a layout along the lines seen in Fig. 9. With enough volume, the resonator box makes everything down stream appear invisible to the header's primary- and secondary-tuned lengths. With a flow capability of 2.2 cfm or more, the muffler appears virtually invisible from a flow standpoint. As a result, we have a muffled system that produces virtually the same power as an open exhaust.
Pressure Waves
With muffler flow requirements out of the way we can move on to methods of applying suitable capacity mufflers to the "system" without needless disruption of length-induced pressure wave tuning. Probably the best way to ease into this somewhat complex subject is to consider some of the published muffler test results done in recent years. These tests appeared to have shown that, sometimes, lower flow mufflers inducing at least some backpressure were required to make best power. In all such tests that I have studied, the conclusions (as apposed to the tests) were invalid. There turns out to be several reasons for this and all are relevant to building a near zero-loss exhaust system.
The first point canceling the supposed validity of back-to-back test results is due to the varied internal designs seen amongst the test pieces Fig. 8. Many mufflers are made up of a number of inter-connected chambers having varying degrees of access ease by the exhaust. Others are of the "glass pack" variety. These types represent opposite ends of a spectrum and have a substantially differing response to arriving pressure waves.
When we dealt with collector length it was emphasized that it was, in most cases, more critical than the primary pipe lengths. Adding a muffler (even one with zero backpressure) to a system with already optimized lengths can alter the pressure wave response such that the tuning is now out of phase with what is required and as a result, power drops. The trick here is to install mufflers such that they don't alter the tuned lengths of the system. Let us assume that the test muffler is attached directly to the end of the collector. A pressure wave is reflected either at the end of the exhaust pipe or when a sizable increase in cross-sectional area occurs. Open chambered mufflers such as Flowmasters often appear to the pressure wave much the same as the end of the pipe. This means the pressure waves see no change in length and reflection occurs largely as it did prior to the fitment of the muffler.
A glass pack muffler can act significantly different. It does not appear as a pipe end but as a substantial increase in collector length. Result: a reduction of power even though there is no measurable backpressure involved. From this we can see that many comparative muffler tests were in fact "pseudo pipe-length" tests. Although many invalid conclusions were drawn, these tests still demonstrated some important facts. The most important is that the engine's needs in terms of flow and pressure wave length tuning must be isolated, one from the other. This is easy to do by means of the pressure wave termination box (resonator box) mentioned earlier. Incorporating a resonator box into a system produces a layout along the lines seen in Fig. 9. With enough volume, the resonator box makes everything down stream appear invisible to the header's primary- and secondary-tuned lengths. With a flow capability of 2.2 cfm or more, the muffler appears virtually invisible from a flow standpoint. As a result, we have a muffled system that produces virtually the same power as an open exhaust.
AJ'S 88NA;935195 said:
So you shortened your collector. From this stuff looks like you hurt yourself, I know the design sucks. I always thought two O2s might work better plumbed into the upper Y section.
DEFIANT 7M;935216 said:
Well it goes into 2 1/2" pipe, no cat, all the way back to a hollow muffer, so I guess I have no collector. Yeah it's loud, too loud for just crusing.
Putting the 0-2 closer to the head with tube headers might get a little too hot wouldn't it? Why 2 0-2's BTW?
DEFIANT 7M;935230 said:
Well, eventually, rabidchimp & i were going to test a few different headers on a dyno, but the 1st couple dynos I do will be just for me and my own records. The collector length idea is good though, i may use that in the header comparison dynos.
The TRUST header came on a 6MGE that was dropped off here to be built and sent out to a customer. AFAIK TRUST still sells them. I talked to Greddy USA last year about buying one.
There is also another JDM header that, very unfortunately, is not made/sold anymore. I've only seen it on one engine, and it was a 7M in Australia. owner is on the forum.
It's a Fujitsubo/FGK header
from time to time, I see these sold on rinkya.com.
It's a Fujitsubo/FGK header
from time to time, I see these sold on rinkya.com.
I've been following this thread since it was made and I wanted to make sure I understand what you guys have come up with. It will be good to recap anyways, correct me if I don't have it right.
So far, the best thing for DD GE's would be to use a header with 1 5/8" primary pipes and a minimum collector size of 2.5"? I said DD because people usually dont make GE's track cars. For most people, they would probably went more low end for day to day driving. As stated before, a longer, smaller diameter collector would be beneficiary.
From what I read before, going larger than 2.5" for a GE's exhaust doesn't give enough backpressure for the engine and results in a loss of power. I guess 2.5" would be ideal considering it's almost the optimal size and backpressure needs to be retained. Even if it was possible to go larger, I guess it would be better to keep the diameter smaller for the collector to keep that bottom end power.
Am I wrong anywhere or am I following this correctly?
So far, the best thing for DD GE's would be to use a header with 1 5/8" primary pipes and a minimum collector size of 2.5"? I said DD because people usually dont make GE's track cars. For most people, they would probably went more low end for day to day driving. As stated before, a longer, smaller diameter collector would be beneficiary.
From what I read before, going larger than 2.5" for a GE's exhaust doesn't give enough backpressure for the engine and results in a loss of power. I guess 2.5" would be ideal considering it's almost the optimal size and backpressure needs to be retained. Even if it was possible to go larger, I guess it would be better to keep the diameter smaller for the collector to keep that bottom end power.
Am I wrong anywhere or am I following this correctly?
Guyana00;935383 said:
Close:icon_bigg. For the DD 1 1/2 primary and 2.5 collector is what your looking for: Stock to mild build up.(intake, exhaust some ignition upgrades) Headers: Pacesetter, OBX, Doug Thorley
1 5/8 primary and a 3" collector: All of the above plus head work, cams, compression. Header: Trust/Greddy
A correctly designed large exhaust will not result in lost hp. But yes a smaller diameter exhaust will give a DD more usable torque or bottom end power.
