With a 180 tstat in 165 Vette with stock programming, I lost 4 mpg on the highway. I didn't have a scanner back then, so i don't know if I was staying open loop or if the ECM was just trying to warm the engine up. Anyway, what could I do in the programming to get the mileage back? Should I just stick with a stock tstat ad change the program from there?

 

Aaron,

I don't think that your car was remaining in open loop from a 180 T Stat. However, it may have remained in open loop for some other reason (can't tell unless we hook up a scanner to find out for sure). I ran a 160 T Stat (before I knew better) for a long time and never had a problem getting into closed loop (even with the stock 1-wire NON-heated O2 sensor).

So, what really remains is to see why your car was getting bad gas mileage. Sounds to me like this may be a standard question for the TPI board. O2 sensor going bad? Possibly. Really can't tell. That would be one of my first guesses.

For anyone else who reads this post keep your eyes peeled Glenn will be discussing some very cool 'Highway Mode' stuff at a later date. How does 20% better gas mileage on the highway strike you?

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

What stat did you move to? The reason I ask is because there is a debate on corvetteforum.com about the validity of 160 tstats.

 

Guys, there is a chance that if he is running a high-flow 180 stat it could be running a litle cooler thatn 180. Combine that with a slight calibration error in his CTS and he could be in open loop, no? Just thinkin' out loud. I'd scan it to check for CL operation for piece of mind and to check for CTS temperature numbers.

 

Most of the closed-loop enable coolant temps I've seen are in the low 100-degree range, like 104 degrees or so. The stock '87 305TPI/A4 bin (ABUN) has a CL enable temp of 77 degrees. I used 80 degrees for a nice round number, but there are other variables that need to be met before the computer goes into CL, like O2 sensor voltage (> .699 V or < .200V) and a timer depending on start-up coolant temp. So, I doubt the problem is with the thermostat unless it was stuck open and his coolant temp was really low. Like Tim, I've never had a problem with my 160-degree 'stat and 1-wire O2 sensor. I'm thinking of getting a heated O2 sensor since that's what takes the longest in my car to meet the CL qualification. The timer values and CL enable coolant temp can be changed with WinBin or TunerCat, so it's just a matter of bringing the O2 sensor up to speed sooner.

AFA the guy with the the 180 'stat in the Vette, his Highway Fuel Mode isn't being activated since it the enable temperature is 185 degrees for most of the 350TPI bins I've seen. That temp can be changed in WinBin and GMEPro so that the HFM activates at a lower temp.

------------------
Greg Westphal
'87 IROC 305TPI/A4

 

Which WinBin ECU has the Highway Mode temp enable? The one I have only has Highway MPH enable. Are there any 32B ECUs out there?

 

I must've been thinking of the wrong value, since I just looked at the latest $6E .ecu and it only has the Highway MPH enable. Sorry.

------------------
Greg Westphal
'87 IROC 305TPI/A4

 

20% better on the hiway? Bring it on!! That'll be a hot article considering the riseing gas prices. Good point though, my 6E doesn't show any kinda hiway mode stuff... just "Enable".
------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)

[This message has been edited by branz28 (edited March 02, 2001).]

 

to approach this from another perspective, depending on the motor & the initial tune, when the motor running @ 160 VS 195 (or whatever the temps are) the efficiency of the engine as a system has probably gone down. this is why the throttlebody has the coolant running through it etc. my car did the same thing. i did not understand it as you can smell the difference @ the exhaust. you can also see it in the BLM numbers that it is FAT.

I called the guy that burned the prom for me & his input was eng efficiency & told me to stick the higher stat back into it. I did not understand as i thought that this was efi & that it has self compnesation built in (O2).

I thought him high & thought that something must be broken. I changed the O2 sensor. no change. I did not have a heated O2 sensor so i put one it. no change. i checked map, TPS, Timing, etc, etc, etc, & replaced a number of things.

finally in a addmision of defeat i put the 195 stat back in & the eff went back up (although it has never been good). put the 180 back in, down it went. put the 195 back in & up it went. I have the 180 in now.

so this not being accepatble to me, i hit the net to find out how to fix the big picture & make it the way i wanted, & here i am.

Tried to keep it short, diarrhea of the mouth is a family trait.

BW

 

Regarding Highway Mode, even in the 8D TDF, there are "missing" definitions that must be addressed in order to make it work properly.

On the 8D TDF, Highway Mode Spark Advance will not work with the variable defined in the 8D TDF; I am finding you must play with "hidden" variables and part of the code to get it to work properly.

With Highway Mode itself, the 8D TDF needs some "tweaking" with the "Lock out Timer" to function properly too. So the 8D, a more completely defined TDF, is still incomplete as Highway Mode goes. So it doesn't surprise me that the 6E (and 32/32B) are missing vital variables also.

I just got back from an out of town business trip, so I have not been able to "play" with my 8D TDF while I was away. But I am hoping to have somemore "positive" results this weekend and recommended settings for the SD guys.

I also have recently befriended a 6E "user" and will be working with him on this feature (plus others) to help addresss the MAF guys. These things require actual testing as the "code" and variables often must be played with to get them to work right.

But the good news is that since you have some of the Highway Mode settings, I am willing to bet the code and other settings are there, just waiting to be found.

Also, my "code changes" will most likely be directly "exportable" to the 6E; so even if the code is incomplete, we will figure out a way to make it work properly.

I am at the point now with eprom burning that just because the stock GM code cannot handle something, it doesn't stop me from doing it anyways. Getting into the actual machine code is the next evolution us eprom burners must do if we want COMPLETE control of the ecm.

I have talked to Tim (Traxion) and we hope to address "machine code manipulation" in future "articles". Initially, how to "bit twiddle" where you only change the hex code at specific addresses and later into "disassembling and re-assembling" the actual source code. This level of manipulation will allow you do to virtually anything with the ecm with the given sensor inputs.

I see some really great things coming up in the near future where we go beyond the simple "changing" of "constants and tables" and dive right into the code itself.

I hope to have some positive results on my "code manipulation" late Sunday/early Monday (for Tim) and the rest in a few weeks.

 

160s 180s, are all hot rodding **tricks** from the flat head ford days. PERIOD.
If you run better with a 180 it's cause you Coolant Temp Correction is wrong.

You can fudge hardware kledges using the CTS, but again, why?.

IMO (ok not so humble), use the 190, little things like end gaps, piston clearance, head bolt torque all matter and are CTS sensitive