279whp with just intake / exh on The Roadster
10-19-2009, 06:32 PM
#261
i think he is going to make two slightly different models one for the rev-up and one for regular DE's.
The flow characteristics seems to be different since he made 30whp on a rev-up and 4whp on a DE...
look three posts up something about the collector leaking though.
i dunno but mine made 250whp and 240ft/lb's with strup 2.5's and borla TD, i know this guy is more knowledgeable than I am , but maybe try out a good TD set-up and see what you make?
The flow characteristics seems to be different since he made 30whp on a rev-up and 4whp on a DE...
look three posts up something about the collector leaking though.
i dunno but mine made 250whp and 240ft/lb's with strup 2.5's and borla TD, i know this guy is more knowledgeable than I am , but maybe try out a good TD set-up and see what you make?
From what i read the longtube design is not the problem in regards to rev/non-rev. It's the cams and lack of variable exhaust cam timing on the non-revs. I dont believe changing the design to anything would fix the lack of adequate cams and exhaust cam timing.
from what i gather from his post, the design is optimal for both engines, yet the non-rev needs some complimenting parts to bring exhaust flow to optimal conditions for the longtubes to go to work.
Why would he make 2 designs if problem can (possibly) be fixed with upgraded cams on the non-rev?
Correct me if i am misunderstanding these findings.
Last edited by GeauxLadyZ; 10-19-2009 at 06:34 PM.
10-19-2009, 08:13 PM
#263
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I think something is up with that specific G. I haven't done any simulation or analyzed it myself, but I have seen many 4 cylinders make that much power or more going from the stock exhaust manifold to a quality header. Did you have a wideband on it? Is the ECU throwing any codes that could affect that? I wonder what the spark timing looks like?
On your race car you have nismo cams right?
On your race car you have nismo cams right?
10-20-2009, 07:31 AM
#264
I think something is up with that specific G. I haven't done any simulation or analyzed it myself, but I have seen many 4 cylinders make that much power or more going from the stock exhaust manifold to a quality header. Did you have a wideband on it? Is the ECU throwing any codes that could affect that? I wonder what the spark timing looks like?
On your race car you have nismo cams right?
On your race car you have nismo cams right?
Your knowledge of 4 cyl tuning does not translate to this car whatsoever and anecdotal evidence does not hold up to the reality of what this market has seen. it's like saying 'I have seen other 6 cyl engines make 50whp from a Y pipe, so the Z should as well'
it doesn't happen.
10-20-2009, 10:02 AM
#265
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have you looked around to see realized gains on the FM platform? I suggest you maybe read up a little, and you will be surprised.
Your knowledge of 4 cyl tuning does not translate to this car whatsoever and anecdotal evidence does not hold up to the reality of what this market has seen. it's like saying 'I have seen other 6 cyl engines make 50whp from a Y pipe, so the Z should as well' it doesn't happen.
Your knowledge of 4 cyl tuning does not translate to this car whatsoever and anecdotal evidence does not hold up to the reality of what this market has seen. it's like saying 'I have seen other 6 cyl engines make 50whp from a Y pipe, so the Z should as well'
it doesn't happen.Will do. The results ARE just surprising to me.
Have other FM platforms run a proper longtube header and had similar results?
Last edited by copec; 10-20-2009 at 10:05 AM.
10-20-2009, 11:29 AM
#266
everything gains-wise on this car surprises people
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
Last edited by Motormouth; 10-20-2009 at 11:32 AM.
10-20-2009, 11:31 AM
#267
Unless a G person tried it, results would not apply to us.
10-20-2009, 12:37 PM
#268
The FM platform is not shared with any trucks (just the FX SUV), or the maxima.
I specifically did not say 'VQ' as the confusion this can bring since the VQ designation is used for a few different engines not at all related to the Z/G implementation of it.
I specifically did not say 'VQ' as the confusion this can bring since the VQ designation is used for a few different engines not at all related to the Z/G implementation of it.
10-20-2009, 08:11 PM
#269
everything gains-wise on this car surprises people
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
where the crawfords gained Nothing. Nada. Zero.Overpriced garbage.
10-21-2009, 05:42 AM
#270
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everything gains-wise on this car surprises people
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
there were only two other long-tubes I know of:
Xerd - never saw a dyno for them, but they also never were popular so methinks they didn't do much
Crawford - pseudo longtubes, saw gains of 10-15 IIRC.
most non-long tube headers see anywhere from nothing, to 6whp on stock cams. people are usually very disappointed with the gains on this car NA. intakes do less than 5whp, exhausts only net 10-20 at the most usually. gains don't necessarily stack well either.
this car requires (as SG is doing) it seems very careful matching of parts when building it. cams to headers, to exhaust to plenum... everything needs to be considered, otherwise the gains are just not impressive.
10-21-2009, 06:31 AM
#271
I have to say thank you guys for the never tiring support! My gut is telling me that the cam's are the restriction and I'd like to throw stock cats and exhaust manifolds on my racecar just to see HOW much power I lose. Would be very interesting, no doubt about that.
Now looking at Jim Wolf's VQ cam card it becomes quite clear that the non-revup factory cam is quite the little guy:
exhaust is 240deg duration (only 205 degrees at 0.050" valve lift) and the intake spends even less time doing productive work, at 238 degrees.
The lift is almost nothing as well at only 9.57mm.
Compare that to the revup and I'm a little bit more confident in my feeling that the revup cams have more potential, they are 248/248 with 10.59mm lift.
(To see how much of a difference that is just look at the head flow results from any VQ head porter and see the difference in flow between 1mm of lift. It's HUGE when the lift is so small to begin with!)
Of course the headers are designed for a more aggressive cam of a 260/260 - 270/270 / 12mm nature.
A quick explanation of why for the curious:
If an engine is tuned for a restrictive exhaust, it will by nature have an exhaust cam that opens late and closes early. Cylinder pressure must build before opening the valve, to push through the restrictive manifolds, cats and tubing. Since the exhaust flow isn't free to pickup momentum (because it is so restricted) backpressure just keeps increasing as the piston travels up the exhaust stroke, and the exhaust valve is forced to close prematurely, as you will get to a point where exhaust flow stops going out of the engine and comes back IN from the exhaust. Once the cam is tuned for this situation, removing the restrictive exhaust leaves you in very much the same place, because the cam is essentially now the restriction!
A larger cam and tuned header will work together by opening early to blow down the cylinder right away, and the header will use wave tuning (at specific rpm) and gas velocity (momentum in a sense) to help suck the cylinder dry. Little overlap is needed at high RPM because the header scavenged the cylinder so well that excessive overlap will just waste intake charge and lower volumetric efficiency.
From the testing we've done, the primary size and lengths are tuned for 4500-8000rpm on an N/A engine. Any longtube header that is correctly tuned WILL require a cam to work with it, but cam selection relies on much more than just header sizing. Compression, valve size and head flow are extremely important as well, as you can go too big with a cam and essentially have the engine fall flat on it's face (lazy low torque everywhere, low response, just blah - i'd rather have a restrictive engine trying its best than a lazy engine!)
This is my understanding of the engine phenomena and if somewhere along the line my understanding has been incorrect please do share, having an entirely correct vision of the gas dynamics inside an engine is very difficult!
Now that all this has been said I'm sure a lot of you are going to look into the labour to swap cams. And for that, I'm sorry!
Now looking at Jim Wolf's VQ cam card it becomes quite clear that the non-revup factory cam is quite the little guy:
exhaust is 240deg duration (only 205 degrees at 0.050" valve lift) and the intake spends even less time doing productive work, at 238 degrees.
The lift is almost nothing as well at only 9.57mm.
Compare that to the revup and I'm a little bit more confident in my feeling that the revup cams have more potential, they are 248/248 with 10.59mm lift.
(To see how much of a difference that is just look at the head flow results from any VQ head porter and see the difference in flow between 1mm of lift. It's HUGE when the lift is so small to begin with!)
Of course the headers are designed for a more aggressive cam of a 260/260 - 270/270 / 12mm nature.
A quick explanation of why for the curious:
If an engine is tuned for a restrictive exhaust, it will by nature have an exhaust cam that opens late and closes early. Cylinder pressure must build before opening the valve, to push through the restrictive manifolds, cats and tubing. Since the exhaust flow isn't free to pickup momentum (because it is so restricted) backpressure just keeps increasing as the piston travels up the exhaust stroke, and the exhaust valve is forced to close prematurely, as you will get to a point where exhaust flow stops going out of the engine and comes back IN from the exhaust. Once the cam is tuned for this situation, removing the restrictive exhaust leaves you in very much the same place, because the cam is essentially now the restriction!
A larger cam and tuned header will work together by opening early to blow down the cylinder right away, and the header will use wave tuning (at specific rpm) and gas velocity (momentum in a sense) to help suck the cylinder dry. Little overlap is needed at high RPM because the header scavenged the cylinder so well that excessive overlap will just waste intake charge and lower volumetric efficiency.
From the testing we've done, the primary size and lengths are tuned for 4500-8000rpm on an N/A engine. Any longtube header that is correctly tuned WILL require a cam to work with it, but cam selection relies on much more than just header sizing. Compression, valve size and head flow are extremely important as well, as you can go too big with a cam and essentially have the engine fall flat on it's face (lazy low torque everywhere, low response, just blah - i'd rather have a restrictive engine trying its best than a lazy engine!)
This is my understanding of the engine phenomena and if somewhere along the line my understanding has been incorrect please do share, having an entirely correct vision of the gas dynamics inside an engine is very difficult!
Now that all this has been said I'm sure a lot of you are going to look into the labour to swap cams. And for that, I'm sorry!
10-21-2009, 02:19 PM
#275
This is funny. I went and took a whole lot of time to educate myself on headers. I still probably don't know .01% there is to know. On a stock cam nonrevup the numbers I got were 1.625 primaries about 30" long. For builds like mine and other cammed cars 1.75"-1.88" primaries about 30" long. The use of tapered collectors and venturi style collectors allows the use of slightly shorter and larger primaries. Nobody put it together that a stock nonrevup makes about 233whp on a dynojet and the revup makes about 15whp more with the same exhaust and intake except for the little venturi in the airbox. Then swap lower collectors so the dyno looks the same but the curve is just moved up 10-15hp. I think the findings of this research is due to the fact that most of the time people put the same small headers on cammed builds like mine and most of the others but few people have gone the other way with big headers and stock cams due to lack of availability of true long tube big diameter primary headers. This is probably a wonderful product if tested on built N/A motors. Who knows maybe these headers can somehow make the cosworth intake manifold achieve its full N/A potential. Sorry for the long post but if they work on stock cams or not who cares they are beautiful keep up the good work.
10-21-2009, 02:43 PM
#276
again, anyone willing to drop 1500-2000 on headers should probably be doing more work to the car.
the only important test, that shows anything is testing this set up on the build it was meant for. that means more aggressive cams and such modifications.
it's true of any modification, even forced induction... turning up the boost on a stock block with stock exhaust won't result in nearly the same gains as a built motor, and it's all to do with totality of the build.
as i was discussing with someone else, the results here don't really prove anything besides maybe that putting these on a stock car won't result in a big benefit.
the only important test, that shows anything is testing this set up on the build it was meant for. that means more aggressive cams and such modifications.
it's true of any modification, even forced induction... turning up the boost on a stock block with stock exhaust won't result in nearly the same gains as a built motor, and it's all to do with totality of the build.
as i was discussing with someone else, the results here don't really prove anything besides maybe that putting these on a stock car won't result in a big benefit.
11-18-2009, 10:27 AM
#279
Just like everything else on an engine, everything is a fine balancing act. Change one thing and need to change 10 others to make that one work correctly.
No suprise that cams are needed for these headers to be effective. Everything is so damn finely tuned on the VQ for its stock setup...
No suprise that cams are needed for these headers to be effective. Everything is so damn finely tuned on the VQ for its stock setup...
