Russ, could you detail your test procedures again? As in how do you get your weather measurements, do you note humidity and barometric pressure, etc. Also how do you measure the acceleration times?

UL

 

just wondering what other setups can one use with the PRM, other than the one shown by gearhead. What type of pipe is used, etc. I am looking into an intake, but am leary of the Injen (hydrolock) and the AEM. The above setup looked very promising, but I don't know what kind of conduit to use from the PRM to the air horn hole.....or where else I could plug in...preferably a place that wouyld not put me at risk of locking my engine. any adivice from those with the PRM, especially pics, would be GREATLY appreciated.

 

I use an accelerometer and note the weather conditions (weather.com)
before going out. In order for me to do a series of runs where I'm comparing to a baseline, I'll need same-temp conditions with a variance of no more than 10-degrees either direction (from baseline temps) with winds no greater than 7 mph. If the temps are more than that, I'll do a series of runs but create another baseline based on the current temps and level of mods. I won't do ANY runs with winds above 7 mph.
When I get to my marked section of road, I'll do a minimum of eight runs with 6500 rpm launches (feathered out, which after three decades of practice, I'm pretty darn good at). I don't get any tire smoke, spinning, etc. Launching at that low of rpm's I've found provides the best level of consistency which negates any tire spinning. Put it this way, on the baseline set of runs, the difference between the best pass and worst passes is very close. I still throw out the worst and best passes and average the rest. Just to be sure.
The times tested are the 1/4-mile since I don't believe 0-60 runs provide enough time for me to ascertain the benefits (if any) of non forced induction modification changes and besides....such a short sprint in reality, happens very little in real life.
My last set of 1/4 mile times averaged .18 slower with the PRM modification however, as noted, I think it would be quicker if I cut out the faux brake duct. For whatever it's worth, my best 1/4-mile time to date (bear in mind this is my best AVERAGE time after eight runs) for my S2K is 13.78 (done in April when temps where in the 50's). I'm not saying I could run this at the track, but I'm consistently in the 13.8's even now when temps are in the 70's. I didn't VTEC my '02 until nearly 800 miles and have broken in my car very carefully. I test drove (before buying my showroom suzuka) a well broken in '01 and feel my '02, for whatever reason, felt noticeably quicker from say, 30-70 mph. Bone stock, my 1/4-mile times (accelerometer) averaged 14.07 so with the Tanabe, PRM and 50-lbs of weight loss (catback, removed tool kit, tire, etc) I've managed to chart a consistent .29 drop in my 1320 (comparing 14.07 stock average to current 13.78 average) which equates to about 13.2hp worth of gain over OEM #'s which seems reasonable.
Probably 7-8 with the PRM (at speed) and 4-6 with the Tanabe plus 2 or 3 hp (worth) from the weight savings.
Regardless, I'd like to get to the track this fall and see if I can duplicate my 13.78 1/4-mile average I seem to be stuck on right now. Maybe I can, maybe I won't. I'm not too concerned about it since I didn't sell my 12.67 (and that time is a legit dragstrip run) Camaro SS for a four-cylinder drag car.
Even if I did a mid 14-sec pass, I'm happy I made the switch. The S2000 is much happier slicing thru the paved Vermont woods as opposed to being timed by a tree.

 

Russ,

I highly suggest that you use proper correction factors on your numbers. Even a 10 deg variation in temperature will cause a change in ET of 0.7% assuming all other conditions remain the same. On a 14 second pass, that's equivalent to 0.1 seconds. If you add in other factors like humidity, barometric pressure, etc. the results can vary even more.

If you include standard deviation of your averages, plus the correction factor variation, you might find that the statistical significance of your tests varies greatly.

Here are some links for your use:

http://wahiduddin.net/calc/calc_hp_dp.htm

http://www.gnttype.org/techarea/misc/altitude.html

UL

 

Actually, every increase of 10 degrees in intake temperature costs almost one percent in power output. This
observation has been written and repeated ad naseum in many tuning circles and from my own experience in accelerometer
testing, actually proves to be quite accurate in its theory.
You quote a .7% difference in ET with cooler temps by 10 degrees. Let's discuss this for a second.
If I average a 1/4 mile run in 14.18 in temps of 80F, you claim I would reduce that ET by .1 seconds (.7% of 14.18)
if I made the run with temps 10-degrees cooler (other conditions same).
If wheel horsepower of an '02 S2000 is say, 204 (85% of 240), then according to the theory that I repeated above,
10-degrees of temperature difference would amount to 1% of the 204 power output or 2.04 horsepower.
There is no way (if we assume the theory above is correct) 2.04 additional horsepower to the S2000 is going to knock
.1 seconds (a car's length) off its 1/4-mile time. In actuality, 2.04 horsepower (according to my own calculations)
is akin to .045 seconds difference in the 1320. I reach this conclusion based on my own theory that with the power/weight
ratio of the S2000 being what it is, one additional horsepower equates to .022 seconds difference in the 1/4-mile if all
conditions (driver, launch, etc) remain constant. Bear in mind, this theory works only if launches remain constant. In
the case of adding large amounts of forced induction horsepower where excessive wheel spin becomes almost a guarantee,
inputting the #'s would be an exercise in futility.
So, where do we go from here?
You claim 10-degrees cooler means .7% off ET. If ET is 14.18, then .7% equals .99 seconds
I claim 10-degrees cooler means 1% off power, not ET, thus 10-degrees cooler means I'm running with 2.04 additional hp, again...
certainly nowhere near enough to drop .1 off my 1/4. Using your info, if Road and Track's 13.8 was done in temps of
80-degrees, it would be assumed if the runs had been done in temps of 50-degrees, they'd have run a bone stock time of 13.5. That ain't happening...we both know that. I know of no 13.5 stock S2000. According to my theory, if they had tested in 50-degree weather, they would have run a 13.68. I'm more inclined to go with that figure.
'Lurk, I've always been impressed with your S2000 knowledge (based on many of your previous threads I've enjoyed reading) but
I'll respectfully disagree with you on this one. Your link, while interesting, appears to be tailored to dyno corrections,
not on-the-street accelerometer testing. Of course, I'll agree that temperature and atmospheric changes most certainly affect timed
runs, but the conditions I test in are so tightly controlled, the single digit temp variances I accept before testing result in
differences that amount to thousanths of a second, not tenths. For example, when I finished breaking in my S2000, I began to baseline
the car and after a week or so, I was averaging 14.07 in the 1/4 (again, for the anti-accelerometer folks, this isn't meant to
say I would duplicate this at the track). Anyways, I calculated before installing my Tanabe, that if what previous owners who
had the Tanabe dyno'd were correct, I should expect about a 7hp gain with the exhaust. With that in mind, I was thinking my 1/4
should drop by about .15 to 13.92
After a weekend's worth of runs, the final average of my post-Tanabe 1/4-mile runs ended up being 13.96 so I was satisfied with
the install. Using my formula for hp explained above, it appeared my Tanabe was giving me about 5 hp which seems to be about
right with aftermarket catbacks for the S2000. In addition, the temps (according to my logbook) were within 4.3 degrees of the baseline.
As for the PRM Jet Stream Intake in the engine compartment, the 1320's dropped fairly significantly to 13.78 which would indicate,
at first glance, the intake is making 8.2hp (on average) and that also, seems reasonable, considering what intakes usually dyno at.
If you can correct me or enlighten me further on your opinions, please do so. These are discussions I like to sink my teeth into
and I appreciate your input. I'm not sure there is a practical way to use the link you provided me but I would love to find one
that would allow me to put in atmospheric inputs to see what margins of error I might be overlooking, if I'm not already. And one more time for the masses. Bear in mind, I use my accelerometer not to REPLACE the dragstrip, rather to chart what mods work and don't work. I've been to the track before and I'm well aware of the variables involved. I plan on purchasing Tesla's latest unit soon, so the current unit will be retired. I look forward to having the ability to check times based in one gear with a mph run of say 30-70mph. That ought to take shifting out of the equation and give me a very accurate idea of what makes horsepower and what doesn't....at speeds most of us would want the benefit. I'm not sure I'm interested in any mod that only reveals itself if the car is doing above 100mph.

 

Sorry Russ, but you're missing some key information. Don't take this the wrong way (nothing personal), but I'm going to outline some key points here that I think you're neglecting or misinterpreting.

First of all, if you run the ideal gas law calculations, you'll find that if pressure is held constant, density decreases by 1% for every 3 deg Celsius increase in temperature (assuming normal temps in the 20-30 deg C range). 3 deg Celsius is equivalent to about 5.5 deg Farenheit. Therefore, assuming other conditions remain the same, you'll find that 10 deg F will result in a maximum theoretical power decrease of closer to 1.85%. In reality, due to other factors, it tends to be closer to 1.15% - if all other factors are held constant, but that could be considered nitpicking. :-)

Second, when considering temp and air density calculations, you have to consider total engine output, not wheel output, not even crank output. Don't forget that an engine must overcome substantial internal losses to just rotate. At normal operating speeds, a significant portion of the power produced is consumed by internal friction and pumping losses. If you consider internal losses, an engine like the S2000 is producing a lot more than its rated power (in terms of actual air and fuel combusted), but it gets sucked up in friction, etc. before the crank will even turn. To get an idea, take an engine on an engine stand (full of fluids) and spin it with a torque wrench. Note how much torque it takes. You can make a rough minimum calculation of how much hp that translates to at 9000 rpm (and the real number will be higher due to other things). The point of this paragraph, is that when calculating hp changes, you have to consider a larger base number than wheel hp - and since crank to wheel hp losses are relatively fixed, the magnitude of actual power changes are larger than what you calculated (closer to 3 hp vs. the 2.04 you calculated). But again, this could be considered nitpicking - however, things start to add up.

Third, your logic on expected acceleration gains from a Tanabe is incorrect. Simple peak hp gains are not sufficient for calculating expected acceleration improvements. You have to consider power increases over the normal operating range during acceleration. If you had actually gained 5 hp (~2%) across the entire operating range you would have gained a lot of acceleration improvement. But that probably wasn't the case. However, note that when temp changes, you gain a percentage increase across the entire power band. If you calculate average power gains for the Tanabe vs. a 2-3 hp gain (~1%) _across the operating range_ for a temp decrease, what do you get? Average power is far more important than peak.

Fourth, the links I provided are well accepted and scientifically derived correction factors. The first link tells you how to compute density altitude, which is a one number representation of the effective air density taking into account barometric pressure, temperature, humidity and altitude. The second link tells you how to correct acceleration times using the density altitude number. These are NHRA accepted and utilized correction factors BTW. You'll find that holding all other conditions the same, a 10 deg F change in temperature will result in a density altitude change of 600-700 ft, which is good for a 0.7% change in acceleration times. But in your case, enter in your conditions for two separate days and see what the density altitude change is.

Fifth, we haven't even gotten into the variance caused by other weather variables. Try varying the humidty 10% (you have to play with the dewpoint), the temp 10 deg and the barometric pressure 0.1 inches and see how much the density altitude correction factor changes. I got nearly 1.4% for just those small changes. And then wind...

Sixth, when we talk about statistically significant changes, you need to put together a mean and standard deviation. I suspect the standard deviation between test sessions with different mods is close to the actual difference in means, without even taking into account the weather correction factors. But I don't know, so maybe you could publish it.

Finally, if you were doing a steady state acceleration run without launch, as you plan on doing with your new unit, the numbers would probably be more consistent. Any time you introduce a hard launch on a car like the S2000, you're going to introduce human variables. When we do accel testing using a Vericom, while we do use standing start launches as an interesting data point, we only use in gear interval acceleration runs for trying to determine true performance gains (as a backup for tuning on the dyno). This eliminates standing start, shifting, etc. which all have the human factor involved. Even the professional drag racers I work with (who are far better drivers than I could hope to be) have to deal with run to run differences in the 0.5% range from run to run, even if conditions don't change, because of traction, shifting, etc. I find it very hard to get runs to duplicate within 0.1 second when I go to the drag strip, even if my 60 ft times are super consistent.

Anyways, if you want to publish your data on your mods, give us the mean, the standard deviation and the full weather conditions for the test. Just the mean doesn't tell us anything and could even be misleading, even if you hold the temps to 10 deg maximum differential.

UL

 

UL, your research certainly seems valid enough, but I'm not sure how it relates to me determining if my intake or cat-back is performing as advertised? I think we're truly nitpicking over thousanths of a second. I have performed more than 200 accelerometer runs over the course of three years with five automobiles (Contour SVT, MR2 Spyder, Camaro SS, Ford Lightning SVT and my S2000). Even when I compared baseline runs when the temps were 75-degrees to those run in 40-degree weather, the times weren't indicative of such huge increases in performance as you suggest and granted, make an interesting case for.
I just haven't seen it. I went back into my SVT logbook and compared some spring runs to fall runs and the times were literally, only .2 apart when the temp variation was almost 40 degrees. I'm not sure how much the other weather factors played a part in the times but in most cases, aside from temperature, the weather conditions are literally the same with only very minor differences. As I stated earlier, I won't even take the car out if the wind is blowing over 7 mph (according to NWS).
As for the Tanabe information you published, I'm not really using the horsepower factor I derived to chart gains, rather the time itself. A ten horsepower spike at 4,000 rpm's is STILL 10 horsepower, however short lived. Granted, it will be nice if it was 10 hp from 2,000 to 8800 rpm, but it's the actual decrease in time that I'm most interested in, not any peak or areas under the curve. These are factors useful in evaluating a dyno run but with the accelerometer, as I'm sure you're aware of, the limitations reveal themselves quickly. I'm not really certain trying to convert such a decrease to horsepower terms is even a useful endeavor, but I do it anyway for grins.
From a standpoint of complete accuracy, your links and subsequent information would be the ideal scenario for a comparison of modifications, but my goal has been not really to chart HOW much each mod is giving me (once again, the accelerometer isn't really going to be truly accurate enough to give me the complete picture) but rather IF the mod has helped me or not.
If I put the Tanabe on and found out my 1/4 mile times increased by .10 seconds, assuming I've run in like conditions, I wouldn't really need to know by how much before ripping it out from under the car.
For the most part, I agree with much of what you write but in the real world of me working with what essentially is a crude instrument compared to a GPS or more advanced accelerometer, I figure the more nuts and bolts in the plumbing, the easier it is to clog up the drain. I have written that both the PRM and Tanabe, when tested separately, showed decent gains (online with what most intakes and catbacks provide, certainly no less) and to the extent of how much climatic conditions played a role in those gains could be debated; but I'll stand by my statement that if I was to use the .7% factor described above, I should certainly see much lower times this fall when I test my S2000 and to date, I've never had such a disparity between spring and fall runs that would support such a huge #. I don't think you can point at the driver because I average a great many runs before coming to any conclusions and usually, the difference between my worst 1/4 and best is under .15 seconds...I'm very consistent with my launches and shifting, though I suppose you could make a case that .15 is a huge gap.

Good discussion. I love this section of the s2ki.com neighborhood.
Gearheads indeed. Thanks!

 

Russ, if the times didn't change as much as suggested, then you should consider the other weather factors. These aren't just theoretical factors, they are proven to have an effect. I spend a lot of time at the strip with a couple professionals I test and consult for and when I look at their plotted data (ET, mph and full weather conditions) there is a great level of consistency.

It isn't hard to come up with a set of realistic weather variables that would only show a 1% improvement in ET for a 30 deg drop in temps. Just run the cold weather calcs with higher humidity and lower barometric pressure. The point is, if you don't compensate for weather variables, you don't know what the real change due to mods is. Furthermore, with a standing start test, traction issues are always present - and in cold weather, traction may be more problematic, meaning your ETs may not drop as much as you'd think (which is a variable you can't correct for on standing starts - which is why I advocate rolling in gear tests).

The point of all this Russ is that I don't think you can make claims about improvements without more careful attention to the data and conditions. I have no doubt that there was some hp increase with both your mods, but the dramatic loss of performance you noted with a simple extension on the intake is unbelievably large without knowing more about the actual conditions.

UL

 

[QUOTE]Originally posted by Russ
[B]Good discussion.

 

[QUOTE]Originally posted by ultimate lurker
[B]