WOuldn't be much good if they COULDN'T measure torque/HP while in constant load, eh!
Well, they don't! But I suppose others have pointed out where and when the DJ dyno is useful.OldBaldy said:WOuldn't be much good if they COULDN'T measure torque/HP while in constant load, eh!
I think the point of the article is that a DynoJet isn't very useful at all. It looks like DynoJet did a classic engineering tradeoff. At the time it was created the existing dynos were expensive because they had to have something to absorb all the torque and measure it accurately (such as a large electric motor).mbohn said:Well, they don't! But I suppose others have pointed out where and when the DJ dyno is useful.
MarcP said:Since the dyno can't measure steady rpm power then tuning is limited to only full throttle applications.
I'm with you on everything except the quotes above. You can tune to a/f at any rpm/tps setting you like. I think that is pretty useful.MarcP said:...For everything else it's worthless.
This is interesting. Is this confirmed? The DJ250 with absorption cannot actually measure the torque at the steady state? I was not aware of this.mbohn said:Well, they don't! But I suppose others have pointed out where and when the DJ dyno is useful.
Yes, that is correct from my experience with DJ.but not actually measure if the resulting mixture provides the best HP at that matrix point?
As I said by running rpm/tps points in the map and adjusting a/f to the "desired" value. This value is supposedly the one that gives best torque. In my case the operator recommended a value, 13.2 I recall, and we went for that. Except for wot, there is no confirmation unless you want to do pulls at part throttle. So maybe what we are saying is that trusting that the operator knows that a/f to use for max torque is the weak link in this method, or you have to start iterating between pulls and the a/f adjustment.So how do they actually create a map at less than 100% TPS - they go through each TPS % at a time in inertia mode, and plot the approximate torque/HP through the individual acceleration runs that that TPS %?
If you are talking about accel/decel enrichment, this method doesn't do that at all. I suppose there are two choices: (i) identify poor accel/decel points on the road and adjust from there, or (ii) see how the bike responds in the fixed rpm mode on the dyno when the tps is opened up. In my case I used (i) because with the system I was using it was easy to adjust a bad accel/decel point using an on-board Palm or when I got home with the main software running on a PC.How does one then ignore any acceleration factors in the ECU dwell calculations - use only a 4th or 5th gear run, and hope that the acceleration rate does not invoke an ECU acceleration enrichment algorythm?
I'm not sure about piggyback computers, but on standalone computers there is often a 2D graph for each of several variables used to multiply the base pulse width. You can temporarily turn most of them to a straight line at 1X, tune for A/F and MTBT, then change the graphs back to original settings and have a fairly good start on complete mapping. Slightly off topic. Carry on.OldBaldy said:How does one then ignore any acceleration factors in the ECU dwell calculations - use only a 4th or 5th gear run, and hope that the acceleration rate does not invoke an ECU acceleration enrichment algorythm?
Good info. What software would that be on?markmakeitso said:I'm not sure about piggyback computers, but on standalone computers there is often a 2D graph for each of several variables used to multiply the base pulse width. You can temporarily turn most of them to a straight line at 1X, tune for A/F and MTBT, then change the graphs back to original settings and have a fairly good start on complete mapping. Slightly off topic. Carry on.
It seems the article makes the point that all dynos don't have the same amount of inaccuracy. DynoJet way overstates the numbers. Whatever Dyno Yamaha uses overstates them even more. Look at the Factory Pro website. There is a listing for their tests on various bikes. Look at a number for say, an R6, and compare the Factory Pro number to the DJ number to the factory number.Matter-Of-Fact said:The way I figure is this... if ALL machines are Dyno-tested, then ALL machines are the same amount of inaccuracy, so everyone is blissfully wrong together...
I can live with that.
That's mostly from my limited experience on the MBE controllers used in Formula SCCA cars. My school spent some time attempting to fix some half-assed mapping (not done by SCCA Enterprises). It's been awhile, but I think there were graphs for coolant temp, time running, air temp, and acceleration enrichment. Probably a cranking modifier too. It's an open loop system, so there weren't any long or short term feedback maps to worry about, making them pretty similar to lots of injected bike computers. I believe they're fairly cheap also, perhaps easier to get into than a MegaSquirt or other similar controller.OldBaldy said:Good info. What software would that be on?
Not sure if this is available on the DJ software, but it's not in the PCiii app, and regardless, having to run an inertia run for HP points across the RPM range means that even if you turn off the enrichment for acceleration, you still have the impact of the effect of the actual acceleration on mixture requirement - so you miss the enrichment that occurs when running normally during acceleration, and thus your numbers are off - all this because the DJ seemingly cannot measure TQ/HP in the steady state. hmmmm..
Wake up, you sleeping thread!Related to the original post, Superflow dynos are one of the best around. They measure SAE horsepower, the accepted and most accurate standard, which reads considerably lower than a DJ. For instance, an R1 will put out around 110-120 hp in SAE numbers. Some 1000s can crack 130. Nowhere near the 140-160hp numbers touted on most dynos for litrebikes.
But the nice thing about the Superflow is it will give you DJ numbers as well - so you get a curve showing SAE hp and DJ hp, so you don't have to do any conversion for the less accurate but more common DJ figure. So my old SV650 made 64.5 SAE hp and 75 DJ hp on the same dyno, on the same run.
Yes, Superflow dynos are expensive. They incorporate sniffer units, ram-air systems, an engine brake roller, and meteorological stations to correct for atmospheric conditions. Hence why they aren't common or accepted.