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At the risk of being slaughtered here on a controversial topic, the power number that dynos make at the wheel is varied and not necessarily based on anything scientific or realistic. Dynojet's dyno calibration is based off a 1970s yamaha - they adjusted the value the dyno output to suit the brochure HP figure. I **** you not.
In the late 90s, early naughties, there was a guy by the name of Todd Wilkes in Australia who had a pretty cool car, a twin turbo V8 mid engine alfa based thing called a Giocattolo. Anyways, he unfortunately met his demise in that thing when he hit a concrete wall at Eastern Creek. Before he died, he did some testing.
Basically, depending on what dyno you ran on, the numbers can mean anything. Looks like you ran a Vtech, which is more common in Europe that the US or Australia, so not sure how that will ultimately compare, But assuming the Crank value is accurate, the wheel figure may be variable, or vice versa.
Yeah, but mine is a NB1 with squaretop matched to 64mm TB, RacingBeat Header, HJS High Flow Cat, 2.5" catback which in theory should have made 140-150 rwhp (I/H/E recipe).
~250crank hp is great @11psi. Timing looks alright. You used 98 ron?
If you put it on a dynojet, you might see 210-220whp (about 35hp loss). The hp loss is pretty static, not like some 20% bs...
Do VD and 100-200kph runs and we can confirm, if there really is sth wrong, but dynos are SO different across the world, it's hard to compare.
VD on the other hand is very comparable (it's just software), when using the real weight/tire diameter and 1:1 gear.
Weather is awesome in GER this week, need to take my car for a spin! I think my turbo car makes ~250crank hp on low boost, will update here with times, so you can compare
That is some legit power. You even corrected the runs with real ambient pressure and temps.
So, something is off with the real dynos whp calibration or it was strapped down like crazy, I don't know.
Peak boost seems to be more like 180kpa on the street with low temps, is that right? Nonetheless, there is no indication, that your engine has a problem, just enjoy it as it is.
Last question out of interest: 100-200kph in 5th? 3000-7000rpm shoud have covered that, you can even time it pretty good in MLV with the VSS or from RPM
I have the short 4.1 axle so in 5th gear I can give you 100 kph - 186 kph time: 9.3s.
Also really wanna know whats up with the real dyno. @der_vierte: As you are from Germany, maybe you know that this dyno from Halle77 Marco Degenhardt has good reputation and is known as a heartbreaker.
So even the lowest VD run 253 whp is higher than the best real dyno run with 251 crank hp. So whats wrong?
a) IAT delta to ambient
The VD run had around 15 K delta, the real one around 25 K. The 10 K difference is approx. worth 3% more air mass.
251.4 PS x 1.03 = 259 PS
b) MAP
There is 100mbar pressure difference between the VD pull and the real dyno. Maybe because of the higher load on the road. One solution could be measuring in 6th gear or increase the load on the real dyno.
259 PS / 1.73 Bar * 1.83 Bar = 274 PS
c) metric PS / kW to HP
274 PS * 0.98632 = 270 HP
So I'm 17 optimistic crank HP over my pessimistic VD WHP. I'm totally willing to do more dyno pulls at the real dyno next week to validate the findings but it still seems not right.
Please guide me if you have more ideas.
Want to understand this. For science
Most shops buy dynos so that they can offer tuning (or do tuning for in-house products). For that kind of work absolute precision is not necessary, so long as the dyno is consistent with itself run-to-run so that the tuner can see the results of the changes he has made. Achieving absolute precision is certainly possible, but it usually requires regular calibration of the dyno which is expensive. Since that calibration isn't needed for tuning the shops don't bother to pay for it.
The exception to this is inertial dynos, such as the classic dynojet. Those dynos work by measuring the rotational speed of a drum of known weight, which is a very simple sensor that can be very accurate without requiring calibration unlike things like load cells or eddy brakes.
So what does this all mean? If your tuner is tuning the car on a non-dynojet then you can admire the shape of the curve and look at the difference between your starting and ending numbers, but you should otherwise ignore the values on the Y axis because they don't mean anything. If you want a dyno sheet that can be usefully compared to other ones out on the Internet, find someone with a dynojet and go there for a 3-pulls-for-$75 day to see if you've got a glory sheet.
Note that even the dynojets are not as consistent as we'd like them to be. In particular they do a lousy job of compensating for altitude in boosted cars, and even for sea level NA cars the numbers can vary by 5-10% between dynos. power/weight race series like NASA Super Touring use dynojet numbers because they're the best around, but it's not unusual to see someone come in 5-10 hp above or below what they were expecting the car to make.
Virtual dyno is an inertial dyno (using the mass of the car itself as the inertial sink), but it has a lot of other variables you need to control (road slope, precise weight, tire slip, aero drag, etc)
9.3 isnt bad at all for a supercharged car without shifting.
I don't know that dyno, but it's only an hour away, maybe I should book a run and find me chasing numbers again
It's good to have a goal in mind, but we have to stay away from that numbers game.
I'm on the home stretch of an E36 m50 with 67mm-turbo build and at first I've set a goal of 800-850 crank hp, but in reality it's just stupid and I would be very happy, if it makes 700. It's simply enough for a street car.
Same with my Miata, I backed it down from like allofit 330whp to 280-300whp and I'm going to leave it there. Engine and wife are also happier.
What I'm trying to say: If you are cool with HOW IT FEELS, just enjoy your car. That's a nice powerband and you can always put the 270whp sheet in your glove box, if it makes you feel better . Theres also always someone faster around the corner.
On the other hand: GP Power in Sulzbach have a Dynojet 224 xLC, which also shows whp and estimated crank hp and I know for certain, that it is pretty spot on.
Here's my take on this. First, the numbers from the real dyno just don't make sense, there's no way 185 whp adds up to 240 to 250 crank hp on a miata, so right off the bat those numbers are under a lot of suspicion.
Second, chassis dynos are going to be measuring wheel hp, and if you want you can do things like coast downs and some math to get an estimate of crank hp, normally I pretty much disregard those crank numbers and focus on the whp because there are just fewer variables and places for shenanigans.
Third, I'm definitely not saying virtual dyno is a useless tool, but you have to be a little bit realistic and understand that it's extremely difficult to control all the variables and get all the inputs perfectly accurate.
So, I think your virtual dyno numbers vs the calculated crank numbers from the real dyno are within the margin of error, given that both of those numbers are fairly error prone, and they sort of match up with what you feel when you actually drive the car, and did a timed acceleration run. You said that dyno was a little bit of a heartbreaker so maybe it's 15hp low, and it wouldn't be hard for the virtual dyno to be 15hp high, so suddenly those numbers are 265 crank, and 235 whp, which is believable. That leaves the 185 whp number from the real dyno, as the outlier. So, what I think is going on is that it's a little bit like Codrus was saying, this dynos calibration is WAY off, it costs real money to get it actually calibrated, my understanding is that in europe it's much more common for shops and enthusiasts to talk about the calculated crank hp number rather than the measured whp number, so I think that shop has just tweaked that crank hp calculation so that it's in the neighborhood of what people are expecting, and that's what they tell them, and don't usually mention the whp number.
I can only speak to my own setup, but when our C30-94 got on dyno/tuned we made 295WHP/230 ft-lb. This was with E85 on a stock NB2 motor, VICS manifold, RB header and exhaust.
Not sure what it made on pump gap. But 180 does seem pretty low. :-/
04-03-2023, 11:02 AM
Rotrex C30-94 Dyno, only 185 WHP?
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. Theres also always someone faster around the corner.
