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OK, don't freak yet. Here's the deal: Ultimate Lurker just opened his new shop (Church Automotive in Torrance, 310-787-7123) and bought a new Dynapack dyno, as described here: https://www.s2ki.com/forums/showthread.php?...&threadid=68716. He's been "christening" it by tuning a few S2000s (so far, just his car, Hybrid's turbo, and my VAFC).
I must say, by the way, the Dynapack is a beautiful setup. It bolts directly to the wheel hubs rather than having the car sit car atop rollers, and can place an arbitrary load on the car for a variety of diagnostic/tuning purposes.
Anyhoo, on to "the 227". My car has the following mods (plus V-AFC of course):
- JR filter (stock airbox)
- Spoon clutch/flywheel
- Hondata intake gasket
- re-routed throttle-body coolant
- xviper-style radmat
- Mugen tstat/rad cap
So, they are basically cooling mods, plus the filter and flywheel, which I've never thought of as significant -- hence the "stock" assertion in the thread title. Certainly, it doesn't seem to add up to 227, right? But here's the dyno plot:
There are a few quirks to the plot (mainly due to the fact that UL's still getting used to manipulating the software): the min and max axis values are set to the the min and max data values, and the horizontal gridlines are then set to "even" increments of 2 lb-ft; so, the lines do not correspond to any kind of even increment on the HP axis. Also, the note about "flywheel torque" is just a placeholder; it is, of course, rear wheel torque. The dashed lines are the baseline, and the solid lines are with the tuning.
So, the plot shows a baseline peak of 221, and a tuned peak of 227, for a 6 hp peak gain. As usual, the gains increased off-peak, especially near redline where the stock ECU runs very rich. So, the V-AFC gains in and of themselves, are "typical", if not kinda modest. For reference, I'll post the settings in the archive thread of this forum.
So, how to rationalize the baseline 221 number? Well, first and foremost, because the Dynapack measures torque slightly differently than a Dynojet, UL estimates that, "stock vs. stock", the Dynapack readings will be 5-10 hp higher than what a Dynojet would read. So, call it 211-216. Now, this board has documented bone stock S2Ks (e.g. Sev's I think) that Dynojet at 210, and assuming that my car's motor is on the strong side, that leaves just 1-6 hp to "account for". To do that, I'll appeal to the Dynapack again, which, unlike the Dynojet (correct me if I'm wrong here, UL) will not be affected by the lightened flywheel's lowered inertia. That is, a Dynojet WOULD show an improvement, perhaps as much as a few HP, so our hypothetical "strong" F20C would dyno to, say, 215 rather than 210.
That gets us within a few HP, more or less, of some figures that this board has previously seen, so you can keep your flame-throwers in your pockets.
First, you can only compare readings on the samy dyno (whatever one, whatever kind.) Add the two variables of a different car and a different dyno (to weather variables) and the readings are useless for comparison. Of course a wheels off reading is going to be higher, you've eliminated two flywheels from the equation as well as grip losses, but you've also introduced another element that is not "real world."
I'd guess your readings are accurate for this dyno on this day. They are not comparable to other cars, dynos, days.
In any event, you now have a nice bragging number that will probably sell a couple of V-AFCs.
The dyno you see is a dynapack. Completely different than a dynojet (much more versatile). And yes, you cannot make direct comparisons if you haven't run your car on the dynojet prior. I did do a back to back on my S2K and it showed 6-7 hp higher on the dynapak. Team Hybrid's turbo S2K also read 6 hp higher than his previous runs on a dynojet (273 vs. 267).
The dynapack works through hydraulic loading and is gauranteed repeateable to 0.3%. It allows us to simulate inertia runs like a dynojet by ramping rpm between two set points over a specificed time period (which is how you get the numbers posted), or you can step through a variety of rpm points in discrete time periods (like many engine dynos). The ramp period can be set to accurately simulate the real world. Just figure out how long it takes you to go from x rpm to y rpm in a particular gear on the road and we'll enter in those rpm points and time period. What I find most useful though (and hardest on my hearing) is the ability to hold the rpm steady under load at any point. We really didn't use this on John's car, but I did show him the effect as we held the rpm steady and watched power and A/F change as I tweaked the VAFC (interestingly, 1% on the VAFC was worth 0.1 points of A/F ratio at 6000 rpm). The real benefit of this dyno is the ability to tune ECU (and piggybacks) in this manner - and is the reason I purchased it over the dynojet. It also avoids problems with wheelspin, tire inflation and strap tension/tire loading.
On to twohoo's runs. First, his car seemed abnormally strong before we ever began the VAFC tuning. My S2K (JR, Mugen header, radmat, conventional oil), the day before, put down 213 hp peak, but was averaging closer to 210. John's car put down a consistent 220 on three straight runs. The first run I thought something was wrong! After confirming that we had consistent coolant temps (run starting temps in the 185 F range), we decided to start tuning. The overall gains with the VAFC were 6-7 hp peak, which is about what you'd normally see (I've seen as high as 9-10). Max gains near the redline were about 10-11 hp. The A/F ratios after the cat were in the low/mid 13's so we didn't want to go any higher.
Twohoos didn't tell me he had a flywheel. This will affect readings during the inertia ramp displayed here becasue we are still ramping the rpm. It would not affect the steady state rpm testing we did. Also, in testing my car, I was able to show that removing the rad mat reduced power by 2-3 hp consistently using the hood open, fan blowing style of test. I have to believe that the Hondata gasket is having an effect as well. I'd like to do back to back tests while on two similar cars, one with and one without the gasket. Maybe if Prolene or twohoos stop by the dyno day next Saturday we can check it out. As for the rest of it, I'd like to know why twohoos car is so much stronger than mine. Above 7000 rpm his car was just much better. He has my best graph on one of his sheets for comparison. I'm jealous.
Anyways, we'll be assembling a database of numbers as more people come in (we've got an S2K dyno day next Saturday). The dynojet is the current standard for dynos and is fine for measuring bolt on parts differences. But for tuning its just not up to the dynapack's capabilities. Even after I bought the dynapack I was questioning just how much better it was. After tuning a few cars on it, I'm simply amazed at how versatile it is (just wish the displays were a little more user friendly :-).
[QUOTE]Originally posted by jschmidt
[B]First, you can only compare readings on the samy dyno (whatever one, whatever kind.) Add the two variables of a different car and a different dyno (to weather variables) and the readings are useless for comparison. Of course a wheels off reading is going to be higher, you've eliminated two flywheels from the equation as well as grip losses, but you've also introduced another element that is not "real world."
Originally posted by ultimate lurker Twohoos didn't tell me he had a flywheel.
Yeah - total brainfade. One of my first mods -- I honestly don't think about it anymore.
This will affect readings during the inertia ramp displayed here becasue we are still ramping the rpm.
Could you elaborate on this? I thought the Dynapack ramped the engine at a given (programmable) rate, so there'd be no observable difference? Would a Dynojet show a difference?
Maybe if Prolene or twohoos stop by the dyno day next Saturday we can check it out.
I'm kinda in hot water right now but I'd like to drop by. I'll see what I can do.
-John
Sure, the dyno does indeed control the acceleration rate of the car. However, under the ramp mode, the engine is still accelerating. There are two things that affect the amount of torque/power required to accelerate a rotating mass. The moment of inertia (MoI) and the acceleration rate. The slower the acceleration rate, the smaller the losses to accelerating the rotating mass. So, if I slowed down the ramp rate from 10 seconds to 20 seconds, we could probably read more power, if the car didn't get too hot. That's why I pick a standard accel rate for the ramp testing if I want to compare cars (like yours and mine).
Of course, as jim pointed out, dynos are still most useful for gauging improvement on one car. Same day testing on the same dyno isn't a bad way to compare either. But after that, comparisons between cars become les meaningful, even with correction factors.
Hey UL, I think you should try an experiment where you tune a car using a VAFC on a Dynojet, then try tuning it on the Dynapak, then take it back and do a final dyno on the dynojet.
That should give a good idea how much more you can get out of tuning on the Dynapak.
First, I would like to congradulate UL on his new shop. I wish you all the success possible with your new venture.
Second, I would like to indicate how jealous I am of you Cali guys who are close enough to his shop to use his services. He is by far the most knowledgable and respected member of the internet that I know of. You guys are lucky to be able to put his knowledge and experience to use directly on your cars.
Damn, maybe I should move down to Cali, don't like the snow here anyways.
Here's the deal: Ultimate Lurker just opened his new shop (Church Automotive in Torrance, 310-787-7123) and bought a new Dynapack dyno, as described here:
Also, the note about "flywheel torque" is just a placeholder; it is, of course, rear wheel torque. The dashed lines are the baseline, and the solid lines are with the tuning.
of you Cali guys who are close enough to his shop to use his services. He is by far the most knowledgable and respected member of the internet that I know of. You guys are lucky to be able to put his knowledge and experience to use directly on your cars.
