Intake Manifold Spacer - Dyno Mule Needed
12-25-2008, 06:09 PM
#61
Developer
Thread Starter
GregBBrd - thank you very much. I am already commited to paying for 4 before-and-after dynos for chrissakes - there just isnt that much profit in these things to pay for all of that. Thank you for dynoning them without furthering my costs. I will give you a set of spacers at cost.
I am looking into trailering my SC car down to the Dyno in Madison - I just hate to do that in the winter...
Ryan P - sorry, but milling a recess into the side of the plate would about double the cost. We looked at milling them to begin with and the cost was twice what water-jet cutting was. In addition, you would need to pay to have a fixture made (a way to clamp them securely and accurately to the tooling table so they can be cut), then pay for the CNC cycle time as well.
All for absolutely no gain whatsoever. We are sealing the spacer to the manifold with non-hardening form-a-gasket 2 (supplied), and using the stock o-ring to seal the covers onto the spacer (just like OEM).
A second o-ring would raise the cost of the kit above $200, plus require buying 2 more o-rings; sales would go down, and there is no benefit.
I am looking into trailering my SC car down to the Dyno in Madison - I just hate to do that in the winter...
Ryan P - sorry, but milling a recess into the side of the plate would about double the cost. We looked at milling them to begin with and the cost was twice what water-jet cutting was. In addition, you would need to pay to have a fixture made (a way to clamp them securely and accurately to the tooling table so they can be cut), then pay for the CNC cycle time as well.
All for absolutely no gain whatsoever. We are sealing the spacer to the manifold with non-hardening form-a-gasket 2 (supplied), and using the stock o-ring to seal the covers onto the spacer (just like OEM).
A second o-ring would raise the cost of the kit above $200, plus require buying 2 more o-rings; sales would go down, and there is no benefit.
Last edited by Carl Fausett; 12-25-2008 at 06:24 PM.
12-25-2008, 06:33 PM
#62
Rennlist Member
Great product Carl thank you ,
I am willing to do a before & after if you want , as I have my own dyno ,however it is in NZ at the moment for repair , & do not expect it back until mid late january , I am sure that I can find a volunteer for the test , I havent finished my project engine yet, 32v gt , I can do a before & after on that as I am sure that the bell mouths at each end of the manifold are restrictive.
On that note has anyone tested the early 32 v manifold on the later s4 engine as it does have later plenums ?
Oh by the way I am in OZ
Merry Christmas all
JG
I am willing to do a before & after if you want , as I have my own dyno ,however it is in NZ at the moment for repair , & do not expect it back until mid late january , I am sure that I can find a volunteer for the test , I havent finished my project engine yet, 32v gt , I can do a before & after on that as I am sure that the bell mouths at each end of the manifold are restrictive.
On that note has anyone tested the early 32 v manifold on the later s4 engine as it does have later plenums ?
Oh by the way I am in OZ
Merry Christmas all
JG
12-25-2008, 06:47 PM
#63
Race Director
GregBBrd
We are sealing the spacer to the manifold with non-hardening form-a-gasket 2 (supplied), and using the stock o-ring to seal the covers onto the spacer (just like OEM).
A second o-ring would raise the cost of the kit above $200, plus require buying 2 more o-rings; sales would go down, and there is no benefit.
We are sealing the spacer to the manifold with non-hardening form-a-gasket 2 (supplied), and using the stock o-ring to seal the covers onto the spacer (just like OEM).
A second o-ring would raise the cost of the kit above $200, plus require buying 2 more o-rings; sales would go down, and there is no benefit.
12-26-2008, 01:09 AM
#64
Rennlist Member
ive already done some exhausting testing of this for other reasons. as expected when the vents are to the radiator area and / or the base of the windshield the pressure starts to rise measureably at 30-40mph. Remember, I'm using a very sensitive pressure/vacuum gauge. on the hood, where this hole is cut, the pressure is not there, its vacuum. The vacuum goes up with speed. There is very good reasons for this. Ive provided the windtunnel values done by porsche, and have verified them in 10% of the places on the chart with a sensor. No surprises there. the hood is a vacuum area, as predicted and is some of the reason for front lift. a hood vent to VENT the high pressure air in the engine compartment fed from the nose and ambient under the car, all vent out the hole to help reduce air flow under the car and relieve some of this vacuum. Maybe one of the reasons my car is faster than it seems due to the HP measured from the dyno, vs the other cars i run against, might be due to my intake venting system at the base of the windshield. Dont know, but what i do know, ive vented the hood for more downforce up front and have verified the tufts pointing upward vs a sealed hole so that should tell you something. Also, a pressure reading confirms the vacuum values in the hood area vs the nose /radiator area.
mk
mk
mk
mk
V8 Man - screw the wool tufts. They are good for air flow evaluation, but the wrong instrument to test this. You want to know if the ducting is working? Buy a cheap vacuum gauge and plumb into your air filter box and go for a drive. Tell us at what speed the pressure starts to rise. My guess would be about 70 MPH.
12-26-2008, 01:11 AM
#65
Rennlist Member
Ive done this, and thought i took a picture of the yarn (tufts) pointing upward.
I can do it again and show you. Its no mystery.
Mk
I can do it again and show you. Its no mystery.
Mk
As to the hood hole - Tape some yarn tufts on the edge of the hole and take it for a drive and let us know which way they point. In theory, if you put a hole in a negative pressure zone, air is not going to flow inward, unless the other side was more negative, which would be very unlikely.
12-26-2008, 01:18 AM
#66
Rennlist Member
absolutely. in fact, if you think of the front of the car as the smooth and more radiused part of a wing. (wing bottom being the bottom of the car) , you can see if you cut holes in the hood, (disrupt laminar flow ), you can reduce the vacuum at the cost of additional drag. best you could hope for would be no vacuum, in certain areas, whereas in the radiator inlet area and all over the nose, you can see the vacuum gauge rise imediately , rising to near .11 psi at over 100mph. so, we are not talking huge differences in gains or losses, but certainly, the smart thing to do would be to turn the flap around to help vent the air that travels before the radiator , out to the hood, BUT, that will decrease flow through the radiator. Best thing would be to patch the hole, and make one after the radiator like the one i made but put a reverse flap on it like you see on the Brittish Noble for example.
You have the "inlet" at the absolute highest, LOW pressure zone on the hood. the engine will be getting cold air, but under vacuum. The stock system gets cold air that momentarily runs over the top of the radiator, under pressure at speeds over 40mph.
I see some rear hood vents. It would be better to tap into those for the intake air source, and leave the front vent open for downforce.
mk
You have the "inlet" at the absolute highest, LOW pressure zone on the hood. the engine will be getting cold air, but under vacuum. The stock system gets cold air that momentarily runs over the top of the radiator, under pressure at speeds over 40mph.
I see some rear hood vents. It would be better to tap into those for the intake air source, and leave the front vent open for downforce.
mk
12-26-2008, 04:38 PM
#68
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Quite right, although it is interesting..
Anyway, when you eventually get the dyno runs completed, will you be posting the results up here PDQ ?!
With a rough idea of total price shipped to the UK, for I have a suspicion that these might make a big difference.
Anyway, when you eventually get the dyno runs completed, will you be posting the results up here PDQ ?!
With a rough idea of total price shipped to the UK, for I have a suspicion that these might make a big difference.
12-26-2008, 09:01 PM
#69
Rennlist Member
12-30-2008, 11:44 AM
#70
Developer
Thread Starter
The installation instructions for this kit is now finished and available on-line.
It is in the "Engine Products" section of this page:
http://www.928motorsports.com/install.html
It is in the "Engine Products" section of this page:
http://www.928motorsports.com/install.html
01-28-2009, 12:50 PM
#72
Nordschleife Master
The reason for my asking this question about the dyno results is that my intuition is completely at odds with the consensus. I think that adding the spacer will hurt the top power.
Here's my rookie logic. Please shoot the argument down before it does any damage! ;-)
The S4 intake manifold acts as a Helmsholtz resonator when the flappy is closed and as an open pipe when the flappy is open and the pulses offset each others in the plenum. For low rpm, the flappy is closed, for medium rpm the flappy is open, and for high rpm the flappy is closed again.
Suppose that the Helmholtz resonator is tuned to work at multiples of 3000 rpm and the open pipes at 4500 rpm. This would give a tri-modal torque curve, by the way. I suspect that Porsche intentionally made the intake runners unequal length to smooth the middle peak to fill the valleys.
The frequency f of a Helmholtz resonator is
f = [c/(2pi)] * sqrt[s/(v*l)],
where c is the speed of sound, s is the intake runner's cross-sectional area, l is the length of the intake runner, and v is the plenum volume.
Suppose that we install a spacer. This expands the plenum volume, which in turn lowers the Helmholtz resonator's frequency. Say we go from multiples of 3000 rpm to multiples of 2500 rpm. What does this mean for the torque curve? First, the torque is stronger earlier. Second, a torque valley is created at around 3400 rpm (a guess) because the first Helmholtz peak is moved to the left and flappy opening point stays at about 3500 rpm. Near 4500 rpm, the torque is as before. As we approach 5500 rpm, the flappy closes again and we're back in the Helmholtz territory. But now, the Helmholtz peak is never used as it's at 5000 rpm and the flappy only opens at 5500 rpm. Instead, the only effect is that the top end will simply fall off about 1000 rpm earlier.
Here's an experiment to test this. Run two dyno runs per each of the two configurations, one configuration with and another without the spacer that extends the plenum volume. The first run is with the flappy overriden open and the second is with the flappy overriden close. If my theory is correct, when the flappy is closed, the spacer does not hurt and nothing changes. When the flappy is closed, one should see twin torque peaks moving to the left to lower rpm levels.
Has someone run this? You are welcome to publicly ridicule me based on these very precise predictions, which should provide an additional incentive to experiment! ;-)
Here's my rookie logic. Please shoot the argument down before it does any damage! ;-)
The S4 intake manifold acts as a Helmsholtz resonator when the flappy is closed and as an open pipe when the flappy is open and the pulses offset each others in the plenum. For low rpm, the flappy is closed, for medium rpm the flappy is open, and for high rpm the flappy is closed again.
Suppose that the Helmholtz resonator is tuned to work at multiples of 3000 rpm and the open pipes at 4500 rpm. This would give a tri-modal torque curve, by the way. I suspect that Porsche intentionally made the intake runners unequal length to smooth the middle peak to fill the valleys.
The frequency f of a Helmholtz resonator is
f = [c/(2pi)] * sqrt[s/(v*l)],
where c is the speed of sound, s is the intake runner's cross-sectional area, l is the length of the intake runner, and v is the plenum volume.
Suppose that we install a spacer. This expands the plenum volume, which in turn lowers the Helmholtz resonator's frequency. Say we go from multiples of 3000 rpm to multiples of 2500 rpm. What does this mean for the torque curve? First, the torque is stronger earlier. Second, a torque valley is created at around 3400 rpm (a guess) because the first Helmholtz peak is moved to the left and flappy opening point stays at about 3500 rpm. Near 4500 rpm, the torque is as before. As we approach 5500 rpm, the flappy closes again and we're back in the Helmholtz territory. But now, the Helmholtz peak is never used as it's at 5000 rpm and the flappy only opens at 5500 rpm. Instead, the only effect is that the top end will simply fall off about 1000 rpm earlier.
Here's an experiment to test this. Run two dyno runs per each of the two configurations, one configuration with and another without the spacer that extends the plenum volume. The first run is with the flappy overriden open and the second is with the flappy overriden close. If my theory is correct, when the flappy is closed, the spacer does not hurt and nothing changes. When the flappy is closed, one should see twin torque peaks moving to the left to lower rpm levels.
Has someone run this? You are welcome to publicly ridicule me based on these very precise predictions, which should provide an additional incentive to experiment! ;-)
01-28-2009, 12:57 PM
#73
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I believe my car may be used by Greg to dyno with/without spacers on a 6.5L motor. That should happen sometime around mid-Feb as part of the tuning being done post-break-in.
01-28-2009, 01:03 PM
#74
Rennlist Member
Ive done back to back runs of the flappy open and close full rpm ranges. there is no gains what so ever past 4500rpm. (ill have to check the exact dyno run.)
01-28-2009, 01:08 PM
#75
Nordschleife Master
Mark -- I didn't understand completely. Are you saying that you've run the car with vs without the spacer both with the flappy overriden open and separately closed? If my theory is correct, without the spacer completely stock, flappy closed should give a better top end power than flappy closed (and much worse middle range).