Rennlist Top 10 HP/TQ
08-05-2005, 02:46 AM
#136
Originally Posted by Under Pressure Performance
...Collectively, it is *our* experience that in virtually all cases the RWHP & TQ numbers are *lower* on a load type *Mustang* dyno in a normally aspirated application versus a *Dynojet*, however, I stand firm on my findings that the results read *higher* on a *Mustang* load type dyno versus a *DynoJet* in *turbocharged* applications....
08-05-2005, 03:05 AM
#137
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Dfastest,
There are a couple of possible scenarios that may have happened, but before I get into each one it is worth mentioning that the DynoJet's drum weighs right around 4,000 pounds and that is what *most* DynoJets use to impose the load, just the drum itself. DynoJet's software then calculates the rate of acceleration of the drum and calculates what it takes to spin the drum at that rate of acceleration, which is why you have to be constantly accelerating, full throttle, in a high load gear on a DynoJet to get the most accurate figures. Now, that said, DYnoJet has developed a load method for the DynoJet that uses the air brakes to impose a short duration load, but this load is not as consistent, or as controllable as an eddie current, or water brake (engine) dyno.
So, it is possible that David's dyno has been outfit with the air brake load option, but before we get into the subject too deep it may be worth determining if, in fact, his dyno is equipped with the load setup.
There is a real long explanation for the load discrepancy on the DynoJet, but the short, for now answer will be - It is all in the software. We were going to add the load feature to our dyno, but after extensive talks with a DynoJet engineer we determined that it was not really what we were looking for. The feature is an add on to an existing technology, versus a load type dyno designed as a load type right from the get go. Like I said, there is a long version of my post just waiting to be typed, but for now I have to get some sleep. Perhaps tomorrow?
In the meantime, give David a call and ask if he does have the load feature on his dyno, and if so, I am sure he can email you the run that you are talking about. With that, I can go on to demonstrate where the discrepancy comes from. We can use it as a visual aid of sorts.
Tell David I said hello.
There are a couple of possible scenarios that may have happened, but before I get into each one it is worth mentioning that the DynoJet's drum weighs right around 4,000 pounds and that is what *most* DynoJets use to impose the load, just the drum itself. DynoJet's software then calculates the rate of acceleration of the drum and calculates what it takes to spin the drum at that rate of acceleration, which is why you have to be constantly accelerating, full throttle, in a high load gear on a DynoJet to get the most accurate figures. Now, that said, DYnoJet has developed a load method for the DynoJet that uses the air brakes to impose a short duration load, but this load is not as consistent, or as controllable as an eddie current, or water brake (engine) dyno.
So, it is possible that David's dyno has been outfit with the air brake load option, but before we get into the subject too deep it may be worth determining if, in fact, his dyno is equipped with the load setup.
There is a real long explanation for the load discrepancy on the DynoJet, but the short, for now answer will be - It is all in the software. We were going to add the load feature to our dyno, but after extensive talks with a DynoJet engineer we determined that it was not really what we were looking for. The feature is an add on to an existing technology, versus a load type dyno designed as a load type right from the get go. Like I said, there is a long version of my post just waiting to be typed, but for now I have to get some sleep. Perhaps tomorrow?
In the meantime, give David a call and ask if he does have the load feature on his dyno, and if so, I am sure he can email you the run that you are talking about. With that, I can go on to demonstrate where the discrepancy comes from. We can use it as a visual aid of sorts.
Tell David I said hello.
08-05-2005, 08:05 AM
#139
Defastest - yes, your runs without load and with load are typical of ALL professional tuners - and guys who OWN BOTH types of dynos - except Scott 
Mustang dynos read 8-12% lower than dynojets - you can explain it away as eloquently and cutely as you like, but those are the facts.
What do I know, I just install them? Despite those screwy architects conspiring against me putting easy-out stuff on the plans like, "verify in field" and
"+/-"
A dynojet (248C) does NOT read load - it is a simple accelerometer. There are various types of load dynos. The Mustang dyno uses eddy current, other types use a hydraulic brake. Both of these types use load AND accelerometer. Dynapack is unique in that it only uses load. So, to sum up the facts:
-Dynapack= load, no inertia
-Dynojet = inertia, no load
-Mustand= inertia and load
-Land and sea= inertia and load
Please note - there was absolutely no Googling done during the production of this post. Experience, not bull****.
Mustang dynos read 8-12% lower than dynojets - you can explain it away as eloquently and cutely as you like, but those are the facts.
What do I know, I just install them? Despite those screwy architects conspiring against me putting easy-out stuff on the plans like, "verify in field" and
"+/-"
A dynojet (248C) does NOT read load - it is a simple accelerometer. There are various types of load dynos. The Mustang dyno uses eddy current, other types use a hydraulic brake. Both of these types use load AND accelerometer. Dynapack is unique in that it only uses load. So, to sum up the facts:
-Dynapack= load, no inertia
-Dynojet = inertia, no load
-Mustand= inertia and load
-Land and sea= inertia and load
Please note - there was absolutely no Googling done during the production of this post. Experience, not bull****.
08-05-2005, 08:11 AM
#140
Rennlist Member
I went back and did some research. The car was run on a Dyno Dynamics chassis dyno at Dyno-Comp in Scottsdale, Arizona. My fault. It wasn't a Dynojet. Are you familiar with this dynomometer Scott? Same question as before. Thanks for the insight.
08-05-2005, 08:31 AM
#144
Yes - if you have a sheet that says 500 - post it. ALL of these dynojet figures posted here are sans load, my man. That makes your 500 perfectly legit, in my humble opinion. 
08-05-2005, 10:37 AM
#145
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Lots of good info here. One simple item that I'm yet to see mentioned (maybe I missed it) is the outside temperature. If you go dyno your car in a 100F weather, heat soak it by doing many runs back to back, the same car, the same day, the same dyno will not make the same HP/TQ. Now change the outside temperature to 70F, do a good first pull and more than likely the same car will make more HP than it did at 100F. Once the Intercooler and intake get heat soaked, as most do after few pulls on the dyno the results (in my opinion) are no longer accurate.
On the dyno, unless you have a super nice setup with huge fans keeping everything cool, the car will get heat soaked. Most dynos I have seen do not have ideal setup for the 951.
Also on the DynoJet, anyone tried running 16" wheels vs. 18" wheels with different overall diameter (on the same car)??? Yet another interesting result.
Comparing HP alone is useless on the 951. 99.9% of the 951s stay (or should stay) below 6700rpm. Once you go over you will need to address the lifters/valve springs/... as well as go dry sump (especially if you want to stay at over 7000 rpm for extended periods "track use").
I think for 99% of the 951 owners, torque is what matters. Torque is what gets you up to speed fast. Since the 951 is not a high revving engine (remember the 6700rpm), torque plays a much more important role. On a dedicated race car high RPM with mods to support it, RPM/HP comes into play.
HP is closely related to RPM. The more revs yor engine turns, the more HP you can make. So for all of us with 951, our RPM is limited (unless you want to spend lots of $$$$$), look for the setup that gives you the most torque and the largest area under the curve.
NZ951, have you considered another list where the ranking is based on the SUM of HP+TQ??
On the dyno, unless you have a super nice setup with huge fans keeping everything cool, the car will get heat soaked. Most dynos I have seen do not have ideal setup for the 951.
Also on the DynoJet, anyone tried running 16" wheels vs. 18" wheels with different overall diameter (on the same car)??? Yet another interesting result.
Comparing HP alone is useless on the 951. 99.9% of the 951s stay (or should stay) below 6700rpm. Once you go over you will need to address the lifters/valve springs/... as well as go dry sump (especially if you want to stay at over 7000 rpm for extended periods "track use").
I think for 99% of the 951 owners, torque is what matters. Torque is what gets you up to speed fast. Since the 951 is not a high revving engine (remember the 6700rpm), torque plays a much more important role. On a dedicated race car high RPM with mods to support it, RPM/HP comes into play.
HP is closely related to RPM. The more revs yor engine turns, the more HP you can make. So for all of us with 951, our RPM is limited (unless you want to spend lots of $$$$$), look for the setup that gives you the most torque and the largest area under the curve.
NZ951, have you considered another list where the ranking is based on the SUM of HP+TQ??
08-05-2005, 12:23 PM
#148
Three Wheelin'
I've wondered why "torque integral" was never adopted. Everyone agrees area under the curve is the real measure of an engine's grunt. So just integrate the torque plot and get yer number. There has to be some logical reason why this doesn't make sense, but I can't think of one off the top of my head.
08-05-2005, 12:32 PM
#149
Rennlist Member
Originally Posted by DanG
I've wondered why "torque integral" was never adopted. Everyone agrees area under the curve is the real measure of an engine's grunt. So just integrate the torque plot and get yer number. There has to be some logical reason why this doesn't make sense, but I can't think of one off the top of my head.
08-05-2005, 02:21 PM
#150
Three Wheelin'
Right on Tom. Avg tq over 4 points in the rev range does accomplish roughly the same goal.
I was just curious why that wasn't a more common way of describing an engine's output. I guess peak numbers are more glamorous.
I was just curious why that wasn't a more common way of describing an engine's output. I guess peak numbers are more glamorous.
