HSRK Components?

[toedrag]

FWIW, on the other board blugoat06 has been posting (#47) regarding IAT with the card MAF data suggesting relocating IAT sensor gains minimal with the card MAF.

Your data is excellent.

Thx! I saw that thread. Without seeing his data, it's hard to compare notes. I did find the IAT tables interesting. I suppose if someone did use an aftermarket IAT sensor, the IAT table could be modified, which would remove the 5-10F error due to differing R/T curves. At this point, I don't plan to play with that, though, but only because I don't have any tuning HW/SW in my possession already.

[toedrag]

I did a few tests while the car was in motion comparing the AC Delco 213-243 & bent stock sensor. Sadly, I couldn't figure out a way to safely include the temp probe. The last test shown below is the most interesting. I drove around until the engine was hot, then I parked next to a freeway and idled to let the IAT warm up until the ECM read 130+. It only took about 6-7 minutes. The purpose of this test was to see how rapidly I could get the IAT's to cool from 130+ until they leveled off. Ambient was 85F.

As I started the test, it took about 1:17 to go from my parking spot until I had turned onto the service road, after that, I kept RPM's at 3k unless I was making a U-turn during my little course loop. The U-turns are represented by the little up-ticks in temps.



My observations:

• It takes a loooooong time for the air to cool off, and it leveled off at 107F. Remember that ambient was 85. As mentioned previously, I suspect this is due to the Roto-fab intake constantly sucking in hot air, likely made worse by the fact that I have an oil cooler up front.
• If there is any heat soak here, it's in the first minute where the 213-243 is ~15F hotter than stock
• The ECM reacted as quickly as the 213-243 which indicates the stock sensor is plenty sensitive. Once I do the lower panel mod & block off plate, it'll be interesting to see if the ECM is still plenty sensitive. To put some numbers to it: in my hair dryer test, the stock sensor was able to cool at a rate of 1.7 deg/sec, but in this most recent test, the air is cooling at a rate of only 0.54 deg/sec at the steepest point around 1:26.
• The ECM & the 213-243 tracked each other nicely, only differing by 4 deg F max at any point.

In other news, I did receive the Omega 44005, and yes, it does have the fastest reaction time out of the three sensors (213-243, SU176, and stock), but as you can hopefully see from the above data, there is no benefit to having such a fast-reacting thermistor if the stock sensor isn't having trouble keeping up (in addition to the fact that the resistance is higher at a given temp, as previously mentioned). Again, once there is a true fresh-air inlet for the Roto-fab, this could change...

Next on my to-do list is the lower panel mod and block off plate. Fun activities for the holiday weekend.

[MeanGreenZ71]

I know the lower panel mod but what is the block off plate?

[toedrag]

I know the lower panel mod but what is the block off plate?

It's just a piece of of something (aluminum sheet metal, plastic, etc) screwed into the framing member to block the hot air path. See http://forum.grrrr8.net/showthread.php?t=7126

Block off plate for CAI. I finally got around to doing this.
Hopefully I installed it correctly.....Charlie????

Stock looking up from bottom of car


Block off plate installed -- Keeps hot engine air out
of the intake path. WHen you put the bottom cover back
on the plate lays right on top of it.

I also keep forgetting that GT's can do the Grill Mod (http://www.forum.grrrr8.net/showthread.php?t=6728) where you cut off the back of the grill near the fog lights instead of doing the lower panel mod. You could even try the grill mod without the block off plate and see what happens; maybe the ram-air effect that the grill mod introduces acts as a barrier and keeps the hot air out of that little pocket, or at the very least there should be plenty more cool air than hot air if they mix together. GXP's can't do the grill mod b/c the GXP bumper has painted plastic right there instead of a grill. Since I'm forced to do the lower panel mod, I'm more inclined to do the block off plate in order to create a low pressure pocket to help encourage air flow from under the car and into the hole. In this sense, I think the GT bumper is superior to the GXP bumper. I was disappointed when I realized that GXP's can't do the grill mod b/c it could work for intake cooling, brake cooling, or oil cooling, etc.

[768MPH]

What are the measurements for this plate?

[MeanGreenZ71]

Oh ok. Ive not done the lower panel mod but ive cut the back of the honeycomb instead. Id like to think it helps bring cool air in to the bottom of my spectre intake...

[toedrag]

What are the measurements for this plate?

I wish I knew. I haven't been able to find the dimensions yet. Once I've finished mine, I'll post the dimensions, template, or whatever else is useful.

[768MPH]

I wish I knew. I haven't been able to find the dimensions yet. Once I've finished mine, I'll post the dimensions, template, or whatever else is useful.

Thanks bud

[toedrag]

Did a ton of testing over the last several days in the 95F to 101F ambient temp, and I'm tired & confused. The short summary is that having the stock IAT sensor bent upwards does produce a small, measurable difference. Everything else I tried didn't seem to matter much while driving once the car was good & hot. Maybe my testing procedure was invalid, or maybe it was just too hot? I might re-test when it's colder, like in the Fall/Winter.

Regarding the Block Off Plate, it's easy to make. The dimensions are roughly 8x16 with a little u-shaped cutout for fog light wiring and a slight angle cut near the back where it meets the upward lip of the plastic splash guard. Take off the wheel & wheel arch liner, get a scrap piece of cardboard and start cutting. To determine the final length, I suggest partially reinstalling the wheel arch liner, then mark on your template where it meets the cardboard. I didn't do this originally, and it ended up about an inch too short. Once your template is complete, HW stores sell aluminum sheet metal for like $10 in a 12"x24" piece that's .019" thick, and unless it's galvanized, you might want to paint it so pick some up some spray paint at the HW store. To install it, I chose to remove the bumper, drilled 3 holes in the flat part of the framing that looks riveted/glued, then used some small machine screws with lockwasher & a nut (also add to your HW store list if you don't already have them).

---
Here are the testing details:
Here's what I can see based on the data, and keep in mind this is with Roto-Fab. I make no claims or conclusions on any of the over the radiator (OTR) intakes like Vararam. All of my driving tests went like this: I warmed up the car with errands in the morning and let the car sit until the hottest part of the day. Then, I drove to a parking lot adjacent to the service road of the highway and idled until the ECM hit 130F. Next, I would do short loops on the service road, doing u-turns under the overpasses. I would select the highest gear possible (like 4th gear at 20mph) and would go WOT, which completely bogged the motor, but allowed max airflow through the system (or so I think? - I'm now wondering if this wasn't the best way to conduct the test). It usually took 10-12 minutes to go from 130F to Ambient+10 deg F, no matter what the configuration was.

• This probably won't surprise you, but results from Idle tests did not correlate to motion tests at WOT. Part of this is due to the fact that the Idle tests were always going from cold to hot and the motion tests are going from hot to cold. The intake insulation wrap technique, even the lower panel mod & block off plate, and even ducting from the fog light housing directly to the bottom of the Roto-fab snorkel worked great in the garage during Idle, but proved to have minimal to zero affect while driving at WOT.
• On the street in ~100F ambient, there is no issue with the stock thermistor sensitivity/time-constant; the air temperature simply cannot cool quickly enough for sensitivity to be an issue. The biggest change occurred during the first 2-3 minutes, where the temp dropped by ~20F, but to get it to drop another 10-ish degrees took another 8-10 minutes.
• I could never get either the ECM or AC Delco to get within 7 deg F of ambient.
• In all my testing, I was simultaneously comparing the stock sensor & a common HSRK setup, which should really be called an IAT Relocation kit b/c it does nothing to actually address heat build up. You can see how closely the stock sensor, even in its normal/non-bent position, follows the AC Delco. Combined with the previous tests showing that the resistance vs temp curve for all of the aftermarket IAT sensors results in the ECM thinking that the temp is LOWER than it really is, and it tells me that there is not much point in the HSRK (at ~100F ambient) - unless you plan to modify the stock IAT table to account for the different resistance from the aftermarket IAT sensor.

I admit that my results don't really make sense intuitively and don't seem to align with the conventional wisdom here on the forums, so take it with a grain of salt. I kept waiting to find something that was dramatically better or worse, but I never found it. And believe me, I wanted to. I suspect it's that above a certain ambient temperature, there's essentially nothing you can do. But, I'm tired of messing with it for the moment.

Like I said before, the only measurable and noticeable difference was with the stock sensor bent up as shown below, but it wasn't a dramatic difference. At this point, I plan to keep the stock sensor bent upwards.

--
Below is with the stock sensor in its stock position. The peaks in the graph are from my u-turns


Below is with the stock sensor bent upwards. I had some traffic on this run, so it's not as clean as others I did.


In closing, there's not much I can say definitively, except:
1. Bending the stock IAT sensor is a good idea.
2. Stock IAT sensor sensitivity is not an issue at 95 degF and above (EDIT: at WOT).
3. Due to the different Resistance vs Temperature (R/T) behavior of the various aftermarket IAT sensors in most HSRK's, the ECM is likely being fooled into interpreting the temp to be too low. Validating the temp with a thermocouple at the Throttle Body and/or characterizing the R/T behavior of your specific sensor, followed by updating the IAT table in the ECM might be in order if you want truly accurate IAT results from your HSRK (and isn't that sort of the point?).

[toedrag]

Ran across this comment on a Vararam vs VCM thread:

On a parting note, and please don't take this in any way as a criticism, however of the approximate 6000+ VCM OTR's sold to date, I would have to say that In Australia we have only ever heard of a couple of people playing with HSRK's, and from our personal testing we do not find that it makes any difference whatsoever. Ultimately it comes down to the tuning, not where the IAT is placed. But as I say, here in Australia the vast majority of cars are custom tuned meaning the likes of a HSRK is moot.

Food for thought on HSRK w/the OTR intakes...