Displacement on Demand - Highway Use

[Texsrt4]

Could you elaborate on how much you changed your timing? A little or a lot? Did you monitor KR to know when to stop or did you not make that much of a change?

I too am playing with my DOD right now and finally have it making a smooth transition from V8 to V4 and back, at least as far as MPG. Stock V4 used to only go down to 23 then it jumped to V8 at 19 then back to V4 at 23. I moved the TPS max up a little and now V4 goes down to 20 and stays engaged longer at a higher mpg, before V8 kicks in. I did see an overall 1.5 mpg change on this tank of gas.

Yes, my '07 does not have a VE table. Luckily for me the LTFT and STFT are not too bad.

i didnt do much, in the way of adding timing. i just adjusted and datalogged. adjusted and datalogged. it seemed to work fine. i would post up my tune, but my tuning laptop took a dump on me, and im waiting til i can afford a new one. i am thinking, if i remember correctly, it was just a couple degrees. just enough to allow me to maintain speed while in DoD.

i always found that was the worst part of the DoD. it would be engaged for only a couple seconds, but then disengages to have the vehicle speed up. i simply adjusted the DoD engagement so that it will allow me to cruise at 65 or 70mpg on flat ground while staying in DoD.

i first started with trying to keep the DoD engaged by adjusting throttle position, etc. but it wouldnt allow me to maintain. adding a bit of timing seemed to do the trick. i promise, as soon as i can get my tune up, i will give the specs.

i may have got lucky...it would be a first though!!!

[LazMan]

Finally made some headway on the 2007 Monte Carlo SS. Runs great, and yes timing is the secret. For some reason those stock DOD timing tables are crap.

When I used the V8 timing tables (thats what GM did on the E40 DOD vehicles, such as the 2006 Monte Carlo SS) I got better results. Much better results.

Given, my car is not a truck, but my highway MPG at 70-75 is now a smidgen under 30 (instead of 24-25 before I started fiddling). I even tried open loop lean, and got 1-2 more MPG but drivability stunk.

I'll post my stock and current tunes when I get a chance in the next day or so.

-Laz

[TiredGXP]

The Ls4 comes factory with a 6100 rpm redline.

OK, so not the highest RPM out there, but three years of occasional 6000 rpm shifts don't seem to have wrecked anything yet.

[LazMan]

Serious? Mine came set-up to shift at 5950 via the transmission. I thought I was "pushing it" setting it up for 6000. Might have to make a few more changes. I did tweak the actual red-line to 6200 I believe. I dunno, don't have the tune in front of me, and am too tired to get it. I still haven't gotten the shifting satisfactory, particularly at light throttle-medium throttle. Have to admit tho, I'm pretty happy with this car and the significant better mileage than my GTO gets with significant performance.

GRR ... I'm going to wait a few days before posting my tune, see if I can work out the kink in the shifting out. I changed EVERYTHING in the timing (used the 7.0L corvette as my starting point for timing.)

As for the 2007 VE non-existent tables, there is a program that converts to tables. However, I dont usually bother with the VE tables anyways and run CLMAF (closed-loop MAF sensor only) by setting the RPM boundaries for "high airflow" to below idle and just tune the MAF. Some say that this is less "throttle responsive" ... but my car lites up those tires like if they were made of phosphorus and not rubber.

Tuning it was easy once I realized I had to turn off DOD for tuning (ty for that tip).

[SilverG]

Thanks for the input. We have had either snow or freezing rain everyday lately. Just not worth trying to log and tune. After we get back from a short vacation I will try bumping up the timing for the V4 tables.

Do you guys run regular or premium? I know what I put into the tank but is there a way to tell what it thinks it is (high or low table)? I also think it makes sense to not pull timing (KR < 2) just based upon one tank of gas with one or two WOT pulls. You agree?

Sorry so many questions, just trying to make sense of it all.

[TiredGXP]

Man, I gotta check out the truck tune files. LS4 has no V4 tables that have been made available for tuning. I figure there also has to be at least the timing table you referred to and a VE table for V4 mode, but nothing shows up.

[LazMan]

My LS4 has a separate V4 table as of 2007, others maybe 2006. Anything not running the E40 PCM.

I based my timing on the Corvette 7.0L engine, so yes I run 93 octane. I also have both the high and low tables set to high timing and have tuned out all the knock permanently.

The way I always tune is to bring down the sensitivity on the knock sensors, then set both tables to high octane, then drive 20-30 miles, logged, with a few WOT runs. Then I tune away all the spark knock. I do this 2 or three times to make sure its all gone.

Then I work on getting the AFR closer to 12.8-13.0, shifting (which is what Im on now), timing tweaks for more power if it can take it at WOT, and other such stuff.

I promise to post my tune tomorrow. I think I got the light-throttle 2-3 and 3-4 shift issue solved (needed a WEE bit of torque management in there, testing it further tomorrow) along with a summary (and "why") of my changes.

I love how this tune "starts" the car ... it sounds MEAN with a completely stock engine and exhaust. ...GTO-ish.

[TiredGXP]

My LS4 has a separate V4 table as of 2007, others maybe 2006. Anything not running the E40 PCM.

Hmmm, probably explains it, I have the E40 for 2005. Hey Chris/Keith, any new tables new coming out for the earlier LS4s?????

I love how this tune "starts" the car ... it sounds MEAN with a completely stock engine and exhaust. ...GTO-ish.

Yeah, I have a nice rumble on start-up, when it isn't drowned out by piston slap at -30*C. At least we're back up near freezing around here now.

[LazMan]

I'm too lazy to "quote" ... LOL.

I had a 2006 GTO, which had the same computer you have. There are some things I liked about that calibration/computer, but all in all the E67 is far superior. Its faster too, resulting in lots more data logged per second.

See, I did the opposite of what you asked for. I copied my V8 timing tables to the V4 timing tables. Im already running a LOT more timing compared to stock at part-throttle.

I don't have time to go over all the changes, but I'm sure you can manage. I'll explain anything you ask about. I'd love to see your tune sometime to compare your changes / results. Its always a nice 'sanity check' imho.

One thing though, my DOD vaccum enable / disable tables are different than yours, so you'll have to open 2 VCM Editors to compare. Ditto with the "idle spark" tables, and the spark burst knock retard base vs cylair delta.

That last one I just zero-out anyways, but I remembered thats one of them.

Also, the slight Torque Management I introduced did resolve my "clunky" part-throttle shifting.

MCSS Version 4.01 is my latest tune.
MCSS Version 0.00 is the stock tune.
Corvette 7.0 I threw in, as its the base for much of my spark timing.

[TiredGXP]

Well, since we're comparing files, here's the tune that is currently in the car. Running in CL MAF (stft only) w/o dod at the moment.

I've just played with the usual stuff: VE, MAF, timing, TM, TCC, Knock recovery rate, some shift pressure/WOT shift speeds, but nothing real major was required for what is still a stock engine.

Just clicked over 60K km this week - warranty gone, accumulating parts for some mods.

I'm actually planning something more ambitious for an upcoming project car - I want to stick an LS4 into a Fiero. It has been done a couple of times now, and I'd like to play around with ~400 hp driving the rear wheels of a 2700 lb car (this will probably be a looooooooooong term project given how much time I usually have available.)

Attachment 10776

[LazMan]

Very nice. I like your spark tables ... they are actually quite similar to mine!!! :O

Go figure. Great minds think alike. A lot of your changes are the same changes I make. Hooray for systematic tuning!

I saw that you have your upper-end timing higher than I do. I've not had a chance to work on that systematically yet, but I'm inclined to raising it via the PE/COT Spark Advance Correction (Gas) table. If you look there, you'll see I have more timing added. I had a lot more in my last version but decided to take it out because I thought I heard some knock and I haven't had the time to scan properly.

Thanks for the file swap.

I love your fiero idea btw. Those cars are a blast (I had an '84) ... it was quick with the puny stock I4, imagine a modern V8 with DOD.

[TiredGXP]

I'll have to find time to compare the files too. Good to see that someone else has come to more or less the same results independently.

Most of my timing work was done in the main spark table, the only modifier table touched was, I believe, the IAT adder. Ended up removing the timing added at low IAT; the stock table was adding up to 6*, which was causing KR at temps of -20*C or so.

Shamelessly stealing the Fiero idea from others who have already done it.

[TiredGXP]

Lazman, was thinking about your comment on timing changes in the upper-end.

Did you notice that I rescaled the timing tables? There wasn't any need to map timing up to 8000 rpm on a vehicle with a 6100 rpm rev limiter, so I rescaled the horizontal range to keep the 200 rpm increments throughout the rev range, my table only goes to 6400 rpm now vs. the stock 8000+ rpm.

Don't know if this really made any difference, but I figured, why not?

[LazMan]

Did you notice that I rescaled the timing tables?

No. I hadn't noticed.

Ok, now it makes a lot more sense, though we're not so far off each-other, particularly with the changes I made last night. Still, HPTuners should notify somehow that scales do not match between compared files.

I decided last night to richen mine up a smidge (from just under 13.0 to about 12.8-12.9) to play with timing on a quick test yesterday and got no knock until I crossed 30 (accidentally. eek.)

The LS4 does seem to handle a bit more timing than my LS2 ever did, must be the lower compression). Maybe 26-29 degrees? That doesnt mean its making the best power. Again, I add my timing in the Gas table at the high end, that way its only there while PE is on.

All that said, I' logged my MAF sensor hit 37 on a pull yesterday (kinda-sorta 370hp) when I kept the timing at the top just under 30. I think 1.8:1 rockers and slight exhaust would bring up the torque curve past 4000rpm. These engines are quite impressive considering the front-wheel-drive shoe-horning they've been subjected to.

Once I've tested more, I'll send you version 4.02 with a data log.

Oh, and as for IAT, its HOT here (south florida) so I lowered the multiplier from 1.0 to .9 and .8 and such, as well as zero'd it for the "cold" side of the IAT (where it adds timing instead of subtracts) ... I think I'll use your numbers as a guide in case I ever drive up north.

[LazMan]

Several things GXP.

First, I ran into the "Fiero LS4" link on another thread (with you in it) ... VERY awesome. I can see why you are tempted to do that. I'd skip the tap-shifting as well as the "display" computer adaptation / addon. (i.e. no need to put in the BCM) and simplify your life ... as its already a complex project as it is!!!

If you ever build it, I may put some miles on my SS and go see it!

As for the SS, I got inspired by your tune and did some tuning of my own. I cannot thank you enough for sharing. I skipped posting version 4.02 ... this one (4.03) is the outcome of tweaking 4.02.

Since you have your DOD off, I made the DOD smoother on mine (I had it staying on TOO much in 4.01 and 4.02) and adjusted timing down a bit and PE down a bit too (higher lambda numbers) ... and the car really woke up, and DOD is barely noticeable. Perhaps it will inspire you to try it.

I also adjusted the shift parameters to make the TCC smoother with DOD (took TCC to 40% min, 100% max) as well as shifting out of overdrive easier. Take a look at my shift curves. In addition, I made some changes to ECT so that the care is (i figure) drivable in cold weather (like yours) so when I go see the Fiero I won't have to pull over and flash stock.

The car is a champ right now. As always, I still want to fiddle slightly with it (in fact this exact version of the tune hasnt even been loaded yet, but all I changed was to compensate for some spark knock here and there) ... overall VERY nice and ready to roll.

-Laz

[TiredGXP]

Lazman

Thanks for the comments. I'll take a look through your latest tune and compare with what I have.

Just re-enabled DOD yesterday, in fact. 91 octane just hit $1.20/liter here - equivalent to $4.53 per US gallon at today's exchange rate. (and we frigging export gasoline that is sold for less in the US )

With my TCC settings, I notice some surge on entry to, and exit from, DOD. No doubt this is due to the throttle "blip" that the ECM uses.

As far as the Fiero goes, yeah, I'd drop the BCM and DIC. Seems the tapshift is directly wired to the TCM, so I might just want to retain that since the shift lever doesn't let you downshift. It is also sometimes good to start in second gear on icy roads (oh, yeah, you don't get those in Florida ).

[LazMan]

The non-tapshift tranny will start in 2nd (ok, I think it will ... I'll check.) Hey, we export meds cheap to you!

Set your min TCC to 40% ... that helps a LOT with the DOD being less-feelable. I am changing my shift pressures now, they are too high (they zoom up to 90psi, thought that would be better), so ignore those.

When I first started tuning, I used to get close to 40MPG at around 45MPH / 65ish kp/h ... it was wicked. ...but ...WAY too shakey an engine.

(Looking at your tune again ... maybe I am less sensitive to the V4/V8 switching than you.... hmmm.)

[LazMan]

This tune will be very aggressive at staying in V8 mode at up to 4th gear / 1900 RPM, where it then tries to stay in V4 mode. I find it very nice to drive, and still does better MPG wise than straight up V8 mode.

[Penguin]

I just wanted to post and say that I have now flashed my truck for the first time (WHEW! It still runs!! ). Only two changes, swapped in the vac charts that Russ posted earlier in this thread (thanks Russ!) and also took out about 50% of the TM but only in performance mode.

It seems like it wants to hold the V4 mode higher for sure, actually had it staying on at 120km/hr (75mph) for a fair amount of time but throttle still seems pretty touchy, perhaps a guy could play with those vac charts just a little more?

Shifting in tow/haul/performance mode seemed a bit harder, hard to tell. Maybe I missed something so will go over the logging and play around a bit more....

Just wanted to thank all you guys for the info you have posted so far.

[LazMan]

Congrats Penguin!

Try lowering the 4-th gear numbers on the "DOD Vacuum Table Disable Vac" table at the RPM where you would like it to hold V4 mode a little more.