I guess the last couple of posts from myself and 997.2 GTS were just ignored when we both went to the trouble to measure the so called "heat soak" (which is the wrong term here anyway) on our cars. Did you guys actually read our posts?

In regards to the race team reference, we don't really know if they used any sort of heat shielding between the intake its entirely possible that a fully prepared race car with a race tuned engine at full racing speeds may experience something other than most of us. I do know what my setup is and what my real world measurements revealed. I also know that I'm happy with my tests at legal highway speeds here in Texas (up to 85 out on the road to Lockhart) and know that my measurements were well founded. Maybe in the next couple of days I'll go out and take screenshots of the measurements I am getting under these real-world conditions if that helps anything.

In any case, rather than consider hearsay about engine heat effects, here is some more factual data about the effects of the air intake heat on power. I'll post some screenshots at the end that help show the basis for this. It all comes down to calculating the effect of air temperature on charge density and its resulting effect on horsepower. I've done these calculations before just for grins and posted some info about our car's volumetric efficiency a while back, but let me give you the data as it applies here.

As a rough rule of thumb, you can figure that a 10 degree increase in temperature will result in a 1% loss of horsepower. You'll find this stated in many places but the calculator results shown below will provide some substance. So as I said in my earlier posts, I guess my ~12 degree additional heat above ambient at a stop results in about a 4 hp loss at idle, neglecting whether or not there are any gains to be made with the filter or plumbing of the Fabspeed setup (although with the smooth intake tubing and smooth joining of the two intake channels of the intake I would think there would be). However, as soon as I am moving this drops quickly to pessimistically a 3 degree above ambient rise, or roughly 1 horsepower... again disregarding any effective gains from the intake itself but I can't easily prove that since I didn't do before and after testing under the exact same conditions. I don't even know that the OEM intake doesn't report some temperature increase under these conditions since the temperature rise might be coming from the compression and movement of air as it squeezes down into the throttle body itself.

So when I'm running around with this filter I may be losing one horsepower or I may be gain several based upon the manufacturer's data. And the intake howl at higher RPMs is outstanding! I'll stick with it. I have to anyway since my Turbo wing hydraulics would hit the original air box. And yes, I know the wing thing is controversial as well.

Thanks to 997.2 GTS as OP for starting this thread and providing a very nice install thread. Hopefully this discussion will help us "air" out some of what I consider myths about this subject.

Here are some charts for sea level performance taken at three different temperatures and all other parameters kept the same, courtesy of the calculator found on the Shelquist Engineering website:

 

I have a Werks1 Carbon Fiber airbox from Champion Motorsports. It uses ITG oiled filters. The airbox itself was reverse engineered from the Porsche X51 airbox. Champion Motorsports put together a psuedo-X51 kit using after market parts (Werks1 aribox, Tubi SS Race Exhaust, & GIAC custom tune). It works well, I can tell a difference in throttle response and power curve between the stock tune and the "pump" gas tune.

 

Thank you for taking the time to post all of this data. Definitely makes me feel better about my purchase.

 

[QUOTE=StormRune;12961737

In regards to the race team reference, we don't really know if they used any sort of heat shielding between the intake its entirely possible that a fully prepared race car with a race tuned engine at full racing speeds may experience something other than most of us. [/QUOTE]

Rolex GS rules do not allow for many mods...stock engine...not race tuned. These were GTS cars I saw in person at the shop and at the races

 

THANK YOU StormeRune!!!

I guess people just couldn't comprehend the information? Well all that matters is that some find happiness, with those (us) being as informed on their decision and execution.

Now put about 100 miles on it...various driving. I do notice that when it isn't warmed up, and I have been babying it or just mellow, there is a "lag" in response; from a start or 10mph-25...BUT I also live in Santa Barbara and this is the first time the car has been in sub-50 degree weather (48 the last two times it went out first thing in the morning). So I truly think it is weather related, as once it is warn the response is improved (car prior was always in 75-90+ degree weather). So it will be good to report back once the temps rise here. I have also noticed that after hard driving, the trunk lid isn't putting out nearly the heat as it was with the stock box ( I pop it for 10-15 minutes every time I get home). There really is a lot of room with that out of there for the entire bay to "breathe". Paired with the rubber inlets that connected to the stock intake housing, there is nice fresh cold air coming through those vents/ducts.

4500-6500 RPM's in Sport w/ Motor Sound is pure sex...I am really thinking about doing the side muffler bypass from FabSpeed...anyone chime in? Also been looking at Sharkwerks...

Will report any negative findings and will update in general...but so far,

 

That sounds like an amazing setup...kudos!!!

 

Thanks so much for running your experiment, StormRune. It basically demonstrates that in the worst case scenario (i.e. there are no appreciable airflow benefits from upgrading to the Fabspeed intake), you would lose 4HP off the line and no power loss at speed.

To answer the airflow question, is there way to measure air velocity through a section of the intake with known cross-sectional area?

 

Glad to help. I'll be posting some more data here shortly from a test run with the OBD-II app I just made. Too bad I didn't see your question earlier but the app can display the Mass Flow Air Rate for you, but that is only at the MAF sensor location. I used this previously to do a volumetric efficiency calculation for the car.

 

With MAF data, it should be pretty straightforward to make an a priori argument for whether the car is actually making more HP with these aftermarket intakes. That would settle the debate once and for all.

All you would need to do is compare the volumetric flow rate (e.g. Liters/min) for stock vs. aftermarket, under identical conditions. This could be at idle and cruising along the highway. Assuming that the engine management system is maintaining the same AFR (and OBD should be able to read this out, as well as STFT or LTFT), any differences in air "uptake rates" by the engine should be proportional to HP, right?

 

I'm going to include a bunch of screen shots below showing various screen captures with annotations, but here is a summary of what these appear to mean. These are taken with a ObdLink MX Scan Tool reporting to the ObdLink App on an iPhone. It can be configured to show many of the ODB-II readings from the car plus some that it can derive from that data (at a rough guess a hundred or so parameters). For simplicity I configured the screen to report only speed, engine rpm, ambient temperature, intake air temperate (from the MAF sensor) and the engine temperature.

For those nerdy enough to care the official air pressure in the area was 30.10 inches and the humidity was an unusually low 23% as reported by Camp Mabry not too far away from home base. I guess the low humidity explains why it was 34 degrees this morning and 72 by midday. This low humidity may also explain the slightly higher temperature differences I saw this time as opposed to what I recall from my early tests since drier air heats much faster and would react more quickly to heating as it moved over the engine.

The initial readings were taken with the car warmed up with a roughly 20 minute drive. When moving it was showing temperatures that ranged between 3 and 5 degrees Fahrenheit above ambient. This is a little higher than I recalled earlier but not too far off. After this roughly 30 minute drive I stopped for lunch and the car sat for about 45 minutes to enjoy the the effects of heat soak.

After departing lunch, I only saw the lower 3 degree differential a couple of times but I did see a pretty rock solid 5 degree higher intake temperature over the ambient, regardless of the RPMs of the engine or speed as long as it was above 25 mph or so.

When at a stop the temperature difference rose pretty quickly to 9 degrees. A typical stoplight would see a rise of about 11 degrees. And the final 5 minute stop in the garage with the engine idling saw a rise to 13 degrees above ambient (in that screenshot the coolant temperature also showed a rise). The car was next to a wall front and side so I think some heat that would normally be dispersed was going back into the car.

Using the calculator available on the Shelquist Engineering website, here are some key charts stacked do they don't take up so much space. You can see in the typical 5 degree case, the percentage difference in horsepower is 0.6% or 2.4 horsepower in a 400 horsepower car. At a typical stoplight or stop sign that rises to around 9-11 degrees. At 9 degrees the difference in horsepower is shown right at 1% or 4 horsepower. In the worst case observed, the car was sitting at idle for 5 minutes but as noted early was getting some heat reflected back from the walls of the garage on the side and front. This resulted in an 18 degree difference that would cause a 2% power loss or 8 horsepower. Note that as shown in some of the other samples, once the speed rises back above 20 mph this difference declines fairly rapidly.

Now assuming that the smoother bores and joins in the intake runners and the possibly better breathing dry filter do give the power increases claimed by the manufacturer, then you are still at a net gain, but in either case I doubt that any of use could feel these losses or gains. Supporting screenshots follow.




Here are the screenshots in order they were taken. Starting with the initial tests with a 20 minute warmup from cold. All of the readings were taken at steady throttle for the speed indicated.

Two early samples showing a 3-5 degree higher intake temperature 20 minutes into the drive.




Moments after stopping the sample reveals a 9 degree difference.


After idling for 3 minutes out in the open we see an 11 degree difference.


Initial reading after a 53 minute heat soak and just starting to move (35 mph)


Back up to speed 20 minutes later out on the high speed tollway. 5 degree difference at 80 mph


5 degree difference at 90 mph


Stop just after speed run shows a rise only to a 7 degree difference.


4 minutes later sitting out in the open the difference is 11 degrees.


After some maneuvering, back up to speed at 75 mph, difference dropping to 7 degrees.


2 minutes later at 90 mph back to a 5 degree difference.


At 100 mph still only a 5 mph difference.


Beginning downshift sequence but holding speed. 3300 rpm at 85 still shows 5 degrees.


A half minute run in a lower gear at 5000rpm but keeping the same speed, still 5 degrees difference.


Back onto normal roads and taking it easier, a 3 degree difference returns.


At 18mph on a back street starting to see a rise to 7 degrees.


At under 10 mph a rise to 9 degrees.


Initial full stop in garage showing 13 degrees difference.


After 5 minutes in garage with door open but no breeze, coolant temp rises and difference rises to the maximum observation of 18 degrees.

 

BTW, you Rennlisters shouldn't have to endure my prolonged posts (see above!) too much for a while after this, I've been relaxing for a few weeks between contracts and am bored... but I should become well occupied elsewhere soon!

 

That's very true. Ideally you'd want to show it in the case where it really matters for performance at wide open throttle. I did some WOT tests when I was gathering the tests earlier but I couldn't responsibly do that and take screenshots at the same time. The temperature difference data at WOT looked pretty much the same anyway but I was only glancing at it.

It can also be difficult recreating the exact same conditions but immediate back-to-back runs would likely suffice. You would need to be on the same exact stretch of road so even minor elevation changes are the same, using the same driver and the same everything.

The app I'm using does have a graphing capability so it should be able to catch the peak flow numbers at each shift point. Since the OBD-II only reports data periodically though, you may miss the peak shift RPM and peak MAF flow although on some runs and hit close to them at other times (this is known as temporal aliasing just to be more nerdy). This may make it hard to compare results accurately. This only matters if the performance differences between the things you are comparing are pretty small, and I think that may apply here. I'm doubtful that would be able to get data that shows a statistically meaningful difference in this case.

Just FYI, if you use the volumetric efficiency equation it takes into account differences in conditions and reports a value in terms of percentage regardless of temperature, humidity, altitude, etc. For example, a 3.8 liter engine with moves 3.8 liters of air per cycle has a 100% volumetric efficiency. If you can move more, and our cars do even without Turbos due to sophisticated intake tuning, then a high performance engine would have 120% efficiency if it could move 4.56 liters of air every cycle. Turbo engines (and superchargers) move much more than this using compression of course. Common cars on the road have efficiencies well below 100%.


In any case, without changing out my deck lid I am unable to test this since my deck lid will not allow fitment of the stock airbox. I would be willing to lend my ODB reader out to someone else to try this if they'd like. It isn't all that expensive. I know the iPhone app works well, I assume there is an Android one as well.

 

Very impressive collection of data but I would think the interest would be between a stock setup verses the Fabspeed intake. I had Fabspeed intake installed for a few months before I went back to the stock intake. My intake temperatures collected with a Go Point OBDII reader showed a considerable increase in intake temps at low rates of speed - from memory about 10+ degrees F. At higher speeds the difference was negligible; 2- degrees F or so. That is pretty much what I would have expected since at low rates of speed the heat from the engine is pulled in from the Fabspeed intake regardless of the heat shield but no so with stock. I suppose at speed heat is more effectively removed from the engine compartment and there is simply less to absorb into to intake.

 

No worries... That's good stuff right there.

My simple note: Dyno runs where the intake mfgr can quote a HP gain probably do come from the better flow, and the conditions in which they can squeak out 10 HP are just fine and more than offset intake temp increases (if they even exist on the dyno run in question).

And they lack a of 'controls', which are more critical in actual experiments.

.

 

Which obd reader can log and graph air intake temp, ambient temperature, and MAF airspeed? That would settle this once and for all.