TR6

Agree. The debate about power added is meaningless until someone posts some factual dyno data that includes a controlled 'before and after' test which only changes the one variable (MAF setup) between the before and after. Preferably tested on the same day. If someone posts only the 'after' dyno, it proves nothing since we won't know what power that specific car made on the same dyno before the MAF mod. Before and after dynos. Period.

deoxford

Ok,
I am back from alot of traveling with work , from the coast to Canada .

I am going to call Aurther today and get a dyno slot set up... I will keep you posted

Marc Shaw

This sounds like an excellent and very fair offer.

Hopefully somebody local will accept the offer and we can answer some questions once and for all.

Marc
....and if the results are in favour of the MAF, I will have to modify my Christmas wish list.

springer3

Derek and I are in contact about meeting up at the dyno. There are still some myths on this thread that I would welcome some comments on:

Myth 1: The "barn door" causes turbulence, and therefore the MAF makes more power. Of course the major restriction except at WOT is the throttle plate. Why else is it called the "throttle"? At WOT, the "barn door" is completely flat and out of the way. The MAF hot wire must be in the center of the air flow. It and its supporting structures are still in the air flow, and therefore cause more turbulence than the barn door. As Loren states, any effect is minor and possibly even trivial. Porsche pioneered the application of computational fluid dynamics to engine performance. Porsche secretly or openly designed heads and induction systems for many famous manufacturers. I am quite sure that on their flagship model they took care of any performance loss due to the "barn door". The reason the MAF is better is that it senses mass air flow at all barometric pressures, and therefore is a better signal for combustion settings.

Myth 2: My car somehow makes 50 HP more than stock. If every car is so different, why is anyone interested in making any modification? I am fanatical when I set spark plug gaps and valve clearances because I know there are, for free, horsepower gains from getting it right. Derek's dyno runs are off the chart, and his car runs like a scalded dog. I believe his mechanic got it all just right as well. I can easily believe that manufacturing variation makes a difference of one or two HP, but more likely that is also a fraction of a horsepower.

Myth 3: Acceleration runs are meaningless for assessing power. Power can be expressed with complete scientific rigor by the rate at which the speed of an object changes. Acceleration rate is a direct measure of power. We were careful to run across the entire engine speed range. The main error in our test was that weight was not known for certain. One of us could have dragging brakes or excessive driveline friction, but I doubt it.

Myth 4: Before and after dyno runs are the only way to measure performance change. See myth 3. Weight is not relevant on the dyno, but driveline friction is. Dyno calibration drifts with temperature, and non-turbo engines change output with air temperature and pressure. There are uncertainties in back-to-back dyno runs. Controls are needed before the dyno result can be considered meaningful. I have yet to see temperature or humidity on a dyno chart. I have yet to see a calibration date either.

I want to try my car on the dyno and will pay for the time. Derek will be there with his car, and hopefully we can swap on and off the dyno to control for the changes that occur in the cars and the dyno. John Vittesse or others are welcome to watch. I don't plan to fix my air flow meter until after it is broken.

tonytaylor

I'm not sure you'll ever find a satifactory proof.

My car had a MAF kit fitted by AMD, run by Geoff who posts as red rooster on Rennlist. I posted the before and after dyno graphs showing an improvement from IIRC 250 to 288bhp, which wasn't acceptable since the dyno operator could have fiddled the results.
Even so I pointed out that the car was faster being able to reach a higher terminal speed between two fixed points which apparently wasn't scientific.
Using the G-tech accelerometer passed around UK listers the car recorded 4.9x 0-60 and high 12s for the 1/4 mile but the G-tech wasn't really considered accurate.
I've had plenty of track time in the company of other 911s, notably 964RS and it's only those on Motec that are faster.
The car has since recorded between 298 ond 304 on various other independant dynos.
At one point the MAF kit failed and the stock AFM was refitted and the car went slower.
I guess some people will never accept such a simple mod will give such big gains. More fool them; if they want to drive around with 50hp less that's their affair.
The engine has been stripped and apart from looking like it's been driven to the moon as far as component wear is concerned all the evidence suggests it's been running/fueling perfectly the last 6 years.

Christer

Hi Tony

Good to see you are still alive - bearing in mind the number of posts you haven't contributed in the last several months!

Sorry for the hijack everyone - and Merry Christmas to all!

TR6

This isn't a complicated concept. Before and after dynos on the same car on the same day (preferrably with the same hour). Change only the one mod between runs. Don't compare dyno runs between two different cars because then the conversation opens back up to debating the other variables between the two cars.

The absolute hp/torque numbers will have some margin of error due to the dyno itself, the temp, humidity, etc. But the relative difference between the before and after is the number that is meaningful. Then if people still want to dispute those results, then that's their problem because they'll never be convinced no matter what. But I'll have faith in the results if the above process is followed.

MitchB

Springer - did you drive Derek's car at all during your side by side testing?

springer3

We traded cars for one run. His is a nice ride - suspension mods, racing seat, and LWF make a noticeable difference. Driving his car, I was up by half a car length at the redline - the biggest difference we saw all day.

Regarding dyno evaluation of mods, let's agree on a plan. I will have my car available when Derek does his testing. I propose my car as the unmodified control reference - and run it each time a mod is ready for a test. Running a second car in-between each modification keeps the dyno warmed up and detects if a weather front comes through or the shop temperature is changing. The dyno operator should be happy because it keeps his meter running. If the output on the unmodified car remains stable or changes less than the output of the modified car, we have an answer. Will anybody argue with those results?

dfinnegan

That's funny!

springer3

Touche!

Ritter v4.0

When are where you guys doing this- if after Jan 5th I will be in town and come and join. If my car is ready and there is time, I will do some pulls as well.

dougn

those roll on tests are eliquently simple and extremely accurate for comparing power ....provided the gearing is the same....which it is

fast951

As I stated earlier, in order to get a base chart for a stock setup, both cars must run the: AFM, same factory chip & DME, same coding plugs settings. Best to run the same fuel, however this must be a bit difficult to accomplish.
Based on claims from previous posts, both cars should make the same power! As people claimed earlier, if the MAF does not yield any performance gain and based on the race results and conclusions both cars should not register more than 5hp difference... If the power graph and peak output differ between both "stock" cars, then more questions are to be answered. If the charts are identical, then we can safely conclude that both cars are stock and we can use this as the base to measure any future modifications.

springer3

I don't agree. What any experiment needs for validation is a control reference - a stable known artifact that can be measured at the same time the main experiments are run. It the stable artifact changes for no apparent reason, that is a warning that something is amiss in the test.

The second car is tested only to determine drift in the dyno calibration and changes in motor HP due to change in weather conditions. If we change both cars, we lose the stable reference and results will be "meaningless", to quote a word over-used in this thread.

I make my living designing experiments. We admitted our last experiment was less than scientific, but variables were under control enough to say the engines are different by less than 5 HP. I was for real when I said going in that I wanted and expected to see some improvement. I will pay for my dyno runs should this go through. I plan to order the MAF kit if the claim of reliable power increase can be proven.

Merry Christmas everyone, and many thanks for being great sports and companions all year long.