tertius said:
Well, I certainly admire you for putting the effort in but I guess I have to declare myself a sceptic. Whilst I don't doubt that there is potentially some gain from ram effect I find it very hard to believe it is that significant at normal road speeds.
Some simple comparisons make your data difficult to accept, for example using the BMEP figure I calculated earlier (15.5 bar), means that your engine is doing a better job than a 2006 Formula One V8 at peak power (2.4L, 750 bhp at 18500 rpm) with a BMEP of 15.1 Bar.
A few things occur to me:
1. first on the DashDyno and using it to derive horsepower will mean that air resistance figures are crucial - how have you arrived at the figures you used? E.g. drag coefficient and frontal area. Moreover, what allowance is made for rolling resistance, wheel spin etc? I'm sure there are other variables that are also significant and may be worth checking.
2. on your power comparison graph why do the standard and first modded graphs finish at around 7,000 rpm - well below peak power?
3. have you tried charting power vs road speed? If the ram effect is significant this should show it.
4. can the S54 engine actually use more air? By which I mean if it is possible to significantly increase the density of the air entering the engine, then the engine will need more fuel to burn efficiently, and the ECU will need to be able to support this.
Have you done any side by side runs against another Z4M coupe? An event like VMax will allow two cars to run side by side in a straightline. Achieving high speed is basically a function of power vs aero, so running against a similar car will eliminate the aero variable; and if something like a VBox were used it would give absolute performance data.
Tertius,
This is LONG, but you did ask. :wink:
<EDIT>
Which formula have you used to calculate the BMEP of the Formula 1 car and mine, and what numbers did you use? What BMEP figure did you calculate for mine?
<EDIT>
Firstly, I’d like to say that I do understand the skepticism that may surround this subject and my figures. I’ve read LOTS of discussions on a host of different forums, and ram-effect and the use of dynamometers seem to be the two subjects that really polarize opinion! Postings like that of SweetRide are not unusual, but I much prefer postings like yours, which are in the spirit of serious and polite discussion.
As I’ve said earlier, I originally got into datalogging in order to find out for myself what really goes on in the air intake and the effect on performance because there’s very little factual information so discussion without the information doesn’t really lead anywhere. From my research it seems that ram-effect for car intakes was pursued in the 1950s, particularly by Chrysler for its commercial products, but also by various independent engineers for race applications. There were several problems though back in those days: electronic fuel injection (EFI) wasn’t available and cars were not equipped with a host of electronic devices working in conjunction with an ECU which could be observed and datalogged so understanding the principle of ram-effect in real world driving conditions was hard to asses. In those days, fuelling was with carburetors, which required balancing fuel flow with the airflow passing into the engine and if you’ve ever done any carburetor tuning, you’ll know that you have to find a sweet spot as the “best compromise” adjustment, whereas with EFI, fuelling is optimized under all airflow conditions.
The problem with an air-intake which harnesses the ram-effect in conjunction with carburetors, is that the flow of air is variable and consequently, this means that the carburetor will perform differently at different speeds and in different gears/engine rpms. As such, ram–intakes caused unsolvable problems and so ram intakes fell out of favour. As such, there’s very little information about the use of ram-effect for road cars using EFI in the public domain. Any information, with actual data is very hard to come by, and despite searching incredibly hard, I’ve yet to find the sort of data that I have produced, although there may be others treading the same or similar path to me. Consequently, I consider that the study of ram-effect and its possible usefulness is a puzzle for which I need to piece together the clues as and when I find them. I've had to follow my hunches and intuition, based on my findings, throughout.
Whilst a static dynamometer can be a useful tool, it is in fact a “one-trick pony” in that it provides information about torque and power, only. The accuracy of them, the repeatability of their measurements and comparability from individual dynamometers and those of different manufacture, seems is still open to debate and will always cause argument. In comparison, the DashDyno and other datalogging equipment connected to a car’s ECU via the OBDII socket simply reads and records whatever information the ECU will yield. The same information of Intake air temperature (IAT) air-flow through the MAF, engine rpm, and a host of other PIDs (Parameter Identities) are used by the ECU in controlling fuelling using the engine mapping system provided by the manufacturer, or from aftermarket remapping. I therefore consider that the raw data recorded by a DashDyno is 100% accurate and that the DashDyno is an advanced hi-tech piece of equipment and certainly not a toy.
So, when it comes to using the DashDyno as a real-world dynamometer to record “at the wheels” figures for torque and hp, the device uses the data from the car’s ECU coupled with a car specific “profile” which is entered by the user (i.e. me) and this is used by the DashDynos software to compute its dyno results. For all my dyno runs in any car I always use 3rd gear and so I set up the profile for each car with the published weight (allowing for my weight and fuel), 3rd gear ratios, Cd, frontal areas, tyre diameter, geographic elevation, ambient air temperature, pressure and humidity. I always do my dyno runs on the same private road and when it’s not very windy and I use a couple of local weather stations with websites to get the environmental conditions at the time of my runs. When performing the runs, I cruise in 3rd gear at low revs until the green light comes on the DashDyno and then I give it WOT and hang on! When I stop the car the DashDyno produces the saved data as a plot of torque and hp. I’ve been using the same methodology throughout my datalogging of all different cars and with various different modifications under test so that I can ensure repeatability and accuracy to show me whether a modification has any significant effect on performance. I have absolutely no interest in attempting to produce bogus figures to fool anyone, because I’m looking for enlightenment and knowledge of what actually happens to performance with mods.
To answer your specific questions:
1. The figures are produced by the DashDyno after a run using the profile loaded for the car, as described above. There’s no wheel spin in 3rd gear. The dyno results that I obtained from the Dashdyno for my Z3MC are very comparable to those obtained on the dynamometers of Evolve and Powerstaion (as I’ve posted earlier in this thread). Likewise, the dyno results I’ve obtained with other cars in OEM state are very comparable to the manufacturers published figures and with modding of their intakes, I’ve seen significant improvements in torque/hp. I therefore consider the DashDyno to be accurate and to be reliable. Since the DashDyno produces “at the wheels” figures, only, there is absolutely no estimation of “at the flywheel” figures as used by static dynamometers, and so what you see is what you actually get, at the wheels. I therefore consider this to be a better way of measuring a car’s performance, because there is no favourable guesswork of adding “losses” into the results.
In any event, even if my DashDyno were not 100% accurate and is over-reading the dyno results, any increases seen from my modding are "relatively" greater than OEM, so gains are still being produced "relative" to OEM, so the gains are still significant and real, although the quantum may be in dispute. However, I don't see anyone challenging the OEM figures my DashDyno produces.
2. Because I lifted off before getting to the redline. As I’ve stated in a previous posting, in my ramcharger mod run, I lifted off slightly to go over a slight crest in the road and then went back on WOT. If you lift off too much the DashDyno considers the run has been terminated and so only calculates for the duration of WOT in that run.
3. Yes, the data recorded by the DashDyno can be exported into .csv format, which can be used in Excel. I’ve made an Excel template, which calculates a “rolling” Volumetric Efficiency (VE) from specific data that I log. I’ve found that by observing the graphical performance of VE has been most helpful in helping me to understand exactly how the air-intake “works” and how ram-effect can be improved with specific mods to increase dynamic pressure (i.e. ram effect).
4. So far, I’ve found that the S54 engines in both my Z3MC and Z4MC have been able to use all the air that I can give them, without any need for a remap. The S54 has a published VE of 105% but in 1st gear it only achieves up to 70%, in 2nd gear up to 90%, but in 3rd gear and above the VE can go above 100%: this difference occurs due to the OEM intake harnessing the ram effect. In the case of the Honda S2000, the published VE is 115%, yet if you read the S2000 forums, owners seem to want to ditch the OEM air-intake, which makes a VE of 115% possible in favour of some aftermarket kit. I find this laughable! Most people just don’t believe or understand how all this works.
As previously said I’ve done a similar ramcharger mod for my Z3MC and I gave a link to a video of me chasing another Z3MC. I know the owner of that car very well and have driven with him a lot. He is hugely experienced and has instructed many others at The Ring, and he taught me the lines on my first trip there. Both our cars have the same aero mods and I’ve followed that car around The Ring before and we were very evenly matched on previous trips. On my visit shown in the video, I’d recently manufactured my ramcharger and I was astonished at the way my car could catch him up on the straight sections (where driving ability is not a factor – that’s why I showed that section). Here's another one:
http://www.youtube.com/watch?v=ICLoOSJEkpY
I’m going to The Ring in April and will have the opportunity to run with several other guys I’ve driven with at The Ring before. I shall record my runs with my DashDyno up and running and I will then have lots of data to see how the car performs at all speeds.
FYI, my Z3MC in OEM condition, will maintain the pressure, at ambient pressure or above, within the air-filter box at WOT, in all gears and at all speeds above 90mph, but with a series of different mods, including a ramcharger mod, I’ve managed to get the same car to now maintain the pressure, at ambient pressure or above, within the air-filter box and perform at WOT in all gears at speeds above 60mph, and my ramcharger reduced this from 80mph with all previous mods. My experience of developing my air-intake mods for my Z3MC was part of the reason why I bought my Z4MC, because I wanted to see if I could do the same/better with a S54 engine with a slightly different OEM intake.
Throughout my experimentation with modifying air intakes, I've never made any predictions of what performance increases that I expect to see. I merely make a change that I think might work and then datalog in a "suck and see" approach, just like all the inventors of the past have done.
Are you still awake?
olice: