Just got back from a trip from Northern VA to Jax, FL to Myrtle Beach, SC to northern VA. Used I-95 on the way down and I-95 to Rt 17 then 501 back to I-95.

On the trip down, using cruise control set to basically 70-75 for most of the trip I got 25.0 to 25.8 MPG. I expected better after earlier, but shorter trips. Those earlier trips were before the VMS HSRK install and it always "felt" like I didn't get quite as good a MPG after the HSRK.

So, on the portion of the trip from Myrtle Beach to home, I switched back and forth between the OEM IAT sensor and HSRK. Most of the non-interstate highway portion was on 4 lane divided primary roads with 55-60 mph speed limits. It was through the "low country" so it was pretty flat, perfect for AFM. With CC set at 5 over (60-65) and running about 35-50 miles on each sensor, I got 27-29 mpg with the OEM and 26 to 27.5 with the HSRK. I tried to keep everything as equal as I could. I would get to speed set CC and then reset the DIC MPG calculator. I did this for each session. I got 2 sessions for each IAT sensor before reaching I-95. The results were quite consistant. On I-95 I went 50 to 70 miles on each sensor before stopping and swapping. Again, I got up to speed, set CC and then reset the DIC. The speeds were higher, 70-75, and the numbers were lower. OEM got 26.1-28.2 and HSRK got 25.6 to about 26.8 over 3 sessions each.

I'm not sure why the differences between OEM and HSRK. Maybe reading cooler (more accurate) air commanded more fuel than the OEM. Maybe driving down to FL with the HSRK "taught" the ECM LTFTs settings that couldn't really compensate in the relatively shorts stints with each sensor.

One thing is for sure, I got better MPG with either sensor than before my VMS ECM/TCM 93 tunes. The last portion on I-95 was 150 miles with CC off, with the HSRK and a "bit" more aggressive driving (faster, more passing, less being passed, some WOTs, heavier traffic, more elevation changes, etc) and it still gave me 25.1 mpg.

Maybe VMS can shed some light and offer some insight.

If you have it dyno tuned with the hsrk it will balance out. PM me about the trip Ed, look forward to hearing from you.

I just installed VMS HRSK 8/2 , it is installed in a rubber grommet and seal on the outside of the grommet wit silicone. I have had 2 check engine lights so far , code p0102 maf sensor circuit ,low input. anybody have any ideas ?

Make sure it is plugged in securely. Someone else had this code and the plug was loose.

Thanks Ray, I took the harness off and found the black wire was not in the plug, reinstalled ,reinstalled wire in plug ,siliconed wires to plug,see what happens ?

If you have it dyno tuned with the hsrk it will balance out. PM me about the trip Ed, look forward to hearing from you.

a dyno tune won't do anything but tune WOT. you need to be tuned on the street to correct any drivability issues.

i can get 28 mpg highway and I am completly stock. Once you go over 65 mph, generally you will decrease your fuel mileage.

Considering i was doing 70-75 and got serveral stints of 28mpg, I think the VMS tune worked well. At slower speeds (60-65), on flatter roads, the 29+ I got was very pleasing to me.

a dyno tune won't do anything but tune WOT. you need to be tuned on the street to correct any drivability issues.

NO! The A/F and timing are being effected by HSRK and can be tuned on a dyno and yes street tuning like I will be doing will allow for fine tuning in a real sense.

Considering i was doing 70-75 and got serveral stints of 28mpg, I think the VMS tune worked well. At slower speeds (60-65), on flatter roads, the 29+ I got was very pleasing to me.

Not all sensors are created equal. Plus, sensor location is different between the MAF and where you located the HSRK. Did you monitor the IAT's while you were running your test?
I have a Dashhawk, and can check my IAT's anytime.
At interstate speeds, either sensor is within a couple degrees of ambiant temp. The sensor should not be causing an overly rich condition based on colder temps. Otherwise, hot temps would lead to lean conditions. Bad for our gas mileage as well.
I don't think it was a very scientific test, but until you can post your IAT's it's hard to understand why mileage would be affected by a temp sensor.
The HSRK really shows it's worth when you are stuck in traffic however.

My guess is a few things changed during this visit not only fuel type ect but possibly ethanol content/altitude? Without having a controlled eviroment thats about all I can surmise IE if it was slightly downhill one way but uphill on the return ect.

The IAT's main duty is simply a spark shaper for temperature corrections, it has pretty much no fueling input whatsoever in closed loop cruise so its not messing with the fueling. Also HSRK's dont require dyno tunes, mainly for the same reason above. IF your tuner shaved the IAT table it MAY require some adjustment but for our tunes and stock its a plug and play item.

Try running on a straight stretch/flat of highway with the same fuel one direction unplug it and go the other way. Let me know, if you need any more input/help we'll be glad to assist you! sorry it took so long to answer this, we've been out of town since last thursday without internet!

No problem on the reply time. I tried as much as possible to keep conditions the same for both sensors. In fact I alternated back and forth the 2 every 30 to 50 miles hoping it would average out variations. Either way, I was pretty pleased with the results. Before the 93 tune I had a hard time getting 24mpg so the numbers speak for the value of the tune.

I've got a stretch of flat road nearby and will try the test as you suggest.
Thanks,
Ed

No problem on the reply time. I tried as much as possible to keep conditions the same for both sensors. In fact I alternated back and forth the 2 every 30 to 50 miles hoping it would average out variations. Either way, I was pretty pleased with the results. Before the 93 tune I had a hard time getting 24mpg so the numbers speak for the value of the tune.

I've got a stretch of flat road nearby and will try the test as you suggest.
Thanks,
Ed

Let me know how it works out, if we can make it better we will :D Thanks for the input though we appreciate it!

You really can't compare gas mileage unless you are driving the exact same road , in the exact same direction , at the exact same speed , with the exact same conditions . Seriously , 1-3 mpg difference can happen going south instead of north on the same road because of a slight slope , etc . You shouldn't be so worried about a 1 - 1.5 mpg increase or decrease here and there because it is completely normal and there are so many variables to to truly compare it , that it is generally impossible on a road trip , just my opinion ...

You really can't compare gas mileage unless you are driving the exact same road , in the exact same direction , at the exact same speed , with the exact same conditions . Seriously , 1-3 mpg difference can happen going south instead of north on the same road because of a slight slope , etc . You shouldn't be so worried about a 1 - 1.5 mpg increase or decrease here and there because it is completely normal and there are so many variables to to truly compare it , that it is generally impossible on a road trip , just my opinion ...


Mike I completely agree, my only concern was he seemed to find a direct correlary to when the HSRK was plugged in so I figured better safe than sorry ;)

I was aware that many variables affected the readings and that is why I swapped back and forth to see if a trend developed. I was more interested in a trend than the actual MPG, though both were better than stock.

I was just curious because it "felt" like the overall MPG was a little lower after the HSRK install than before. I know it went up with the VMS 93 tune but had a good opportunity on this trip through the low country (flat) in SC to run the experiment.

I wanted to see if my gut feel was correct or just erronious. If it was correct and the MPG was a little lower with the HSRK, then I wondered if the HSRK was reading cooler, more accure air and the ECM was running just a little richer for that reason. I know the IAT affects timing commanded but the ECU uses the IAT sensor along with the MAF signal to deternime air volume, doesn't it? If so, then the LTFTs would adjust for the variables to keep the O2 sensor readings in the desired range. It occured to me that perhaps the output characteristics of the 2 sensors in terms of temp vs output voltage were slightly different and the ECU had "calibrated" the LTFTs for the HSRK (I have run it for a few weeks and hundreds of miles) but that calibration was a little leaner than the OEM IAT sensor would have calibrated to in order to get to the commanded AF ratio. Maybe the swapping back and forth did not allow enought time for the ECU to get the LTFTs to the numbers the OEM IAT needed. It was not until writing this that I realized that the delta between the 2 decreased as the number of swaps increased. It makes me wonder if the LTFTs were moving toward an average of the what was wanted by both sensors. My best OEM MPG and worst HSRK happened after the first swap from the long term use of the HSRK to the OEM and the just the opposite after the last swap. Maybe the best OEM MPG number were artifically high and would have "tuned" to the HSRK MPG numbers if the OEM IAT sensor was left in longer.
Just some thoughts.
What do you think?

No, as I said in the previous post the IAT's job is a spark shaper and has little to no input on any fueling calculations :) Best bet is if you are REALLY that curious is to get a Dashhawk and check the readings while tdriving that will tell you exactly whats gonig on.

No, as I said in the previous post the IAT's job is a spark shaper and has little to no input on any fueling calculations :) Best bet is if you are REALLY that curious is to get a Dashhawk and check the readings while tdriving that will tell you exactly whats gonig on.

Ok. I thought there was a second order correction of the basic MAF table based on reported IAT and that would influence the LTFTs. I'm an EE and some of our products use automotive MAF sensors to measure air volume. We do not run closed loop in our applications nor are we controlling fueling (this is not an automotive application). In trying to equate our non-automotive experience with an automotive application, I must have compared apples to oranges.

The repeatability of the better mpg with OEM IATS and the decreasing MPG delta between the 2 as the number of swaps increased led me astray apparantly in thinking it was LTFT related.

VMS, I just sent you a PM about getting a Dashawk.
Ed

Was that with 93 octane? Ever try 87 for just cruising?

Vector....

I'm on the verge of purchasing a VMS Tune and CAI. I plan on dyno-ing a baseline (stock), installing the CAI, establishing another baseline to see the CAI HP gains, then flash the VMS tune... then run another baseline on the dyno to see final results. I plan on testing on a Dyno-flow machine...all pulls on 93 octane fuel. What gains in HP do you traditionally see? On your website... 40 rwhp? Please advise. ... also what is the stealth option for the VMS tune?

Thanks in advance for your time \ reponse...:)

Was that with 93 octane? Ever try 87 for just cruising?


I'm tuned for 93. MPG with 87 will be not as good.

Unfortunitely when I used the vector hsrk my plugs become dark again. It runs a little rich and mileage does go down. I am positive. With that said I have the superchips tuner. Maybe they do not like each other. At the track though I think it definitely helps between runs. I am unplugging it away from the track and plugging it back in at the track.

I have that tune too, but disagree with the assumption. Secondly, what type of CAI, or did I miss it?

I disconnect the vms sensor. I let a couple of days pass by and pull a plug. All tan. Self cleaning. Very good~ I reconnect the hsrk and a couple of days later I pull a plug. Black.

I have the rotofab with the 91 rotofab tune.

But I can definitely seeing it working at the track.

I have mine disconnected under the hood. 30 seconds later it can be hooked up at the track.

I am not a mechanic. But it must affect the fuel delivery even cruising around.

In my previous car (I have the powerflash cable), VMS did a retune for my cai, cat back and hsrk. You might want to ask Kirk if a retune for the hsrk would make a difference.

that's what I think. To fully take advantage of the hsrk you really need to tune for it.