New Camshaft Grind and Dyno
07-19-2012, 06:43 PM
#16
Former Vendor
No problem, Greg. Let me see if I can help you understand.
The R3 camshafts have more mid-range on my supercharged motor, as shown. But, also as shown, the HP peaked and started to fall off at 6000 rpm. They would be a better choice for a road racer with gearing to concentrate in the 4500 to 6000 rpm band. I certainly have enjoyed road racing with them this season!
However, for my upcoming Bonneville event, I need the peak HP to be at peak RPM. The most important power band for me at this event is 5800 rpm and up. So, the R4 camshafts are a better fit for the application.
Now lets look at the Torque curve. The R3 cams present their peak torque from 4200 to 5400 rpm, and that's pretty good. But the torque curve of the R4 cams is even broader and more linear from 4200 to 6200 rpm. Because you don't race, you might not understand the value of a near constant power band.
Race engines with peaky power bands are harder to drive, because the power will come in suddenly when the engine hits its peak, and should that happen in a corner, it can cause a spin and a shunt. But engines with a long, constant power curve are easier to drive - you can throttle-on through a corner and know that the rise in torque is constant with the increase in RPM - there are no surprises.
Anybody who has raced a turbo can tell you how challenging it can be if the turbo happens to come in mid corner! Not fun. So, for the average driver (read ME) a flatter torque band is more predictable and easier to drive.
In conclusion - its not that one camshaft is "better" than another. It depends on the application, and one camshaft may be more appropriate for the task at hand than another.
By creating a new camshaft grind all I have done is increased the choices available to the 928 owner.
The R3 camshafts have more mid-range on my supercharged motor, as shown. But, also as shown, the HP peaked and started to fall off at 6000 rpm. They would be a better choice for a road racer with gearing to concentrate in the 4500 to 6000 rpm band. I certainly have enjoyed road racing with them this season!
However, for my upcoming Bonneville event, I need the peak HP to be at peak RPM. The most important power band for me at this event is 5800 rpm and up. So, the R4 camshafts are a better fit for the application.
Now lets look at the Torque curve. The R3 cams present their peak torque from 4200 to 5400 rpm, and that's pretty good. But the torque curve of the R4 cams is even broader and more linear from 4200 to 6200 rpm. Because you don't race, you might not understand the value of a near constant power band.
Race engines with peaky power bands are harder to drive, because the power will come in suddenly when the engine hits its peak, and should that happen in a corner, it can cause a spin and a shunt. But engines with a long, constant power curve are easier to drive - you can throttle-on through a corner and know that the rise in torque is constant with the increase in RPM - there are no surprises.
Anybody who has raced a turbo can tell you how challenging it can be if the turbo happens to come in mid corner! Not fun. So, for the average driver (read ME) a flatter torque band is more predictable and easier to drive.
In conclusion - its not that one camshaft is "better" than another. It depends on the application, and one camshaft may be more appropriate for the task at hand than another.
By creating a new camshaft grind all I have done is increased the choices available to the 928 owner.
Fortunately, I spent the first 30 years of my career as a Porsche racer and then later ran a few professioal race teams, so I've got an exceptional handle of what is needed. While I still get a couple of calls, every year, from someone wanting me to come and manage their race team, I've pretty much "moved on" and am happy just staying here developing pieces for 928s. However, I certainly would not nearly be as good as I am at doing this, without that extensive road racing background.
Easy to understand that with your current effort to go fast at Bonneville, the only thing that really matters is how much horsepower you can make at the higher rpms. As long as you can generate enough midrange power to make the car get into the higher rpm range, everything in the midrange is a moot point.
Great that you created a cam that makes more high rpm horsepower, even though it effectively "killed" the midrange, from what you had before.
Interesting to try and imagine a "customer" that would benefit from this same camshaft, however. I guess that that customer would have to be doing the exact same thing you are doing, with the exact same engine set-up.
Any road racer would certainly not be happy trading all that midrange torque for more high end power. Ceertainly not going to make any car faster, around any track.
07-20-2012, 10:44 AM
#17
Developer
Thread Starter
Ceertainly not going to make any car faster, around any track
Any road racer would certainly not be happy trading all that midrange torque for more high end power
I already have a follow-up cam grind in the works from what I have learned from this last grind. A cam grind that features the best of both the R3 and the R4. I'll let you know when I have it.
07-20-2012, 11:51 AM
#19
Administrator - "Tyson"
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Doesn't anyone have the before / after dyno charts from Mark Andersons car showing a huge loss of torque in exchange for top end power with the carbon fiber intake?
I have them on a hard drive somewhere.........
I have them on a hard drive somewhere.........
07-20-2012, 04:04 PM
#20
Race Car
Yeah but Mark had a redline way higher than stock. That was my original point, these R4 cams would be great on a 928 that revs to 7000RPM+. On a 928 with a stock ~6,500RPM redline, the R4 cams will make the car slower than with R3 cams assuming it has dyno charts following the ones in this thread.
Dan
'91 928GT S/C
475hp/460lb.ft
Dan
'91 928GT S/C
475hp/460lb.ft
07-20-2012, 04:14 PM
#21
Former Vendor
I wouldn't be so fast to judge. The results from a NA motor may be significantly different in the mid-range and top end between these two cams. I wont comment on that until I have the dyno charts to show my work. You can guess, I wont.
Not true. You know how many racers want a rev motor rather than a bottom end motor. Thiose guys who want to live between 6000 and 7500 rpm. This shows promise for them, and at least gives them another option/choice.
I already have a follow-up cam grind in the works from what I have learned from this last grind. A cam grind that features the best of both the R3 and the R4. I'll let you know when I have it.
Not true. You know how many racers want a rev motor rather than a bottom end motor. Thiose guys who want to live between 6000 and 7500 rpm. This shows promise for them, and at least gives them another option/choice.
I already have a follow-up cam grind in the works from what I have learned from this last grind. A cam grind that features the best of both the R3 and the R4. I'll let you know when I have it.
I personally hope that you install these cams in every engine that you touch.
Last edited by GregBBRD; 07-20-2012 at 04:57 PM.
07-20-2012, 06:56 PM
#22
Racer
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Carl:
Just when I think I've got a pretty good "handle" on what makes engines work, something like this comes along and I get completely lost. How can cams that make 100 less horsepower and less torque, everywhere below 5,200 rpms have "very linear power curve making for non-stop push-you-back-in-your-seat acceleration" over the cams that have higher torque and horsepower?
To me, this is like saying: "I had two inches removed from my ***** and now it is longer."
Help me understand.
Just when I think I've got a pretty good "handle" on what makes engines work, something like this comes along and I get completely lost. How can cams that make 100 less horsepower and less torque, everywhere below 5,200 rpms have "very linear power curve making for non-stop push-you-back-in-your-seat acceleration" over the cams that have higher torque and horsepower?
To me, this is like saying: "I had two inches removed from my ***** and now it is longer."
Help me understand.
11-16-2013, 10:42 AM
#23
Nordschleife Master
Searching for random camshaft info, came across this thread. One point worth noting:
---
http://www.928motorsports.com/parts/camshafts.php
32v Porsche® 928 Cams:
Name Intake lift/duration Exhaust lift/duration Comments
928MS 32vR3 .442" / 222 deg .398" / 216 deg (d)
928MS 32vR4 .412" / 217 deg .398" / 216 deg (e)
(d) Best race cam for NA motors, more bottom and mid-range than cam R4.
(e) Best race cam for Boosted motors, pulls hard from 3800 to 6800 rpm
---
Both d and e use Webcam #264 profile for exhaust. The intake cam is different: d uses Webcam #279 for intake, and for e there's no camshaft in the Webcam catalog that will match that lift and duration. The dyno graphs in this thread tell me that the intake duration number in R4 must be wrong.
I am guessing that profile is really (0.412" lift / 252 advertised / 232 @ 0.05") or (0.412" lift / 266 advertised / 242 @ 0.05"). If you'd put a gun to my head and force me to guess, I'd say the former based on the dyno graph.
I would correct that intake duration on the web site so there will not be any surprises.
---
http://www.928motorsports.com/parts/camshafts.php
32v Porsche® 928 Cams:
Name Intake lift/duration Exhaust lift/duration Comments
928MS 32vR3 .442" / 222 deg .398" / 216 deg (d)
928MS 32vR4 .412" / 217 deg .398" / 216 deg (e)
(d) Best race cam for NA motors, more bottom and mid-range than cam R4.
(e) Best race cam for Boosted motors, pulls hard from 3800 to 6800 rpm
---
Both d and e use Webcam #264 profile for exhaust. The intake cam is different: d uses Webcam #279 for intake, and for e there's no camshaft in the Webcam catalog that will match that lift and duration. The dyno graphs in this thread tell me that the intake duration number in R4 must be wrong.
I am guessing that profile is really (0.412" lift / 252 advertised / 232 @ 0.05") or (0.412" lift / 266 advertised / 242 @ 0.05"). If you'd put a gun to my head and force me to guess, I'd say the former based on the dyno graph.
I would correct that intake duration on the web site so there will not be any surprises.
11-19-2013, 01:36 PM
#24
Developer
Thread Starter
I pulled the camshaft cards for both our 32vR3 cams and our 32vR4 cams and re-checked the site.
The web page is correct.
What isn't obvious on the page is the change in the base circle of the R4 model camshafts. That may be what confused you. We used a different master cam and brought it down to get this custom camshaft.
Duration published is at .050"
You are correct, the exhaust cam lobes are identical on the R3 and R4 models.
Please let me know if you have any other questions.
The web page is correct.
What isn't obvious on the page is the change in the base circle of the R4 model camshafts. That may be what confused you. We used a different master cam and brought it down to get this custom camshaft.
Duration published is at .050"
You are correct, the exhaust cam lobes are identical on the R3 and R4 models.
Please let me know if you have any other questions.
11-19-2013, 01:47 PM
#25
Rennlist Member
acceleration = power/ (mass x velocity)
I just had to toss that in there , because it has been so long!
anyway, anderson's engine got 520rwhp and it was a pretty broad HP range from 5500rpm to 7000rpm. yes, peak torque went down with the intake, as we normally see when changing out cams, but it wasnt that dramatic vs his old intake at 440rwhp.
