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Ugh... when new tires force you to retune! Well the ECM is coming back down again... :lol: My tires were evidently so old that it was almost effortless to light them up. Figured my launch tune was pretty good. I didn't really take that into account I guess... I put on some new tires the other day... Took it out for a drive today and found an isolated street, so I decided to nail the gas from a standstill. To my surprise, I got a nasty bog. Did it again... same thing. The bog doesn't recover until about 2500 rpm after which starts pulling really hard again... I guess the new tires hook so well, the engine isn't allowed to start winding up that fast and now has to contend with the actual full inertia of the car at those low RPMs. I happened to be logging data so I went home and started looking at it. My AFR looks great... WB O2 shows idling around 13.5:1 in forced open loop idle... it drops to about 12.5 when I hit WOT (i.e., no over-rich or too-lean conditions). So the AE/PE fueling is perfect. What I found though was an issue with the spark timing. I idle at 25 deg. After going WOT, the spark advance drops to the 10 deg that I programmed in at 100 kPa at idle speed... all well and good. But, the problem is, it stays at 10 deg until about 2300 rpm when it finally starts to climb back up (slowly). The commanded advance doesn't start matching the main spark table until literally around 4000 rpm! For instance, my advance curve at 100 kPA in the main spark table goes to 10 deg at 600 rpm. By 2000 rpm, I'm supposed to be at 28 deg (but ECM is only commanding 13). At 3500 rpm I'm supposed to be at 33 deg (but ECM is only commanding 20). At 4000, I'm supposed to be at 33 deg (ECM finally catches up by commanding 33 deg). I'm getting no knock retard or knock counts. My PE spark adder is set to zero. So what gives here? Commanded spark advance seems to match my spark table at all other times except for during launch. Is this a function of forcing open loop? My forced open loop gets disabled at 1500 rpm (goes back into closed loop above 1500). If so, it seems like I should be back at full advance right after 1500 rpm? Man, I hope this isn't a conundrum... The open loop idle is so smooth and the throttle tip-in is so razor sharp, I never want to go back to closed loop idle. But, this spark timing problem is killing my launch... |
Re: Ugh... when new tires force you to retune! I can't wait to see the answer to this one. |
Re: Ugh... when new tires force you to retune! Well, it doesn't seem like an issue with open loop... Looking at a couple of instances where I went from 0 to ~60% TPS from off idle, the spark timing didn't have any issues. It seems to be an issue with going from 0 to 100% from off idle. SAUJP has some sort of launch control built into it, no? Is this something to do with that? |
Re: Ugh... when new tires force you to retune! Anyone have any ideas? |
Re: Ugh... when new tires force you to retune! Reviewing the data some more... Looks like it's something to do with the launch control. It must be activated in my SAUJP_V5 bin. Soon as I nail the throttle, the launch control shows active and the timing is literally stuck at around 10 deg. At t=0 I'm at TPS=0% and 24° BTDC, and I hit the gas. At t = 143 ms, launch control activates... I'm at ~6% TPS and I'm at 63 kPa and 24° BTDC. At t=287 ms, launch control still active, I'm at 31% TPS, 95.2 kPA and now at 10° BTDC. That's the correct timing for that point in time... However, again the timing curve is extremely lazy compared to what I have programmed in. Launch control remained active until 3850 rpm where the timing only hit 21° (it should have been 33 by then). As SOON as launch control deactivated at 4075 rpm, the timing jumped to the correct 33 deg. I was still at 100% TPS WOT, so it's unclear what the significance is to 4075 rpm to why the launch control suddenly deactivated. I guess I need to dig into the launch control subroutine in SAUJP and deactivate it first of all. But also curious why it's doing what it's doing. Though if it's trying to keep me from "wasting time" spinning my tires, it's certainly doing a good job of it! :lol: |
Re: Ugh... when new tires force you to retune! 1 Attachment(s) Ok, it's the launch control causing it... and it's duration is related to time, not RPM. I found the launch control (LC) spark timing table (attached below). And now I know the significance of the 10 deg (and it's not my 100 kPa value in the main spark table). The LC lasted for 2.4 seconds according to my data. In the table, the LC contains non-zero spark adder values for up to 2.4 seconds, after which the spark adder goes to zero. Tunerpro says it'll maintain LC for up to 3 seconds (but in this case all the values are set to zero between 2.4 and 3.0 seconds). So that explains the duration of the application of LC. Now for the 10 deg... The commanded timing I'm seeing at each RPM while LC is active is 10 plus the value in the table for the given point in time. I.e., the timing at 1 second is 10 + 1.05 for 11.05 deg (exactly as reported in the data). The final timing at 4075 rpm (2.4 seconds after going WOT) is 10 + 11.95 for 21.95 deg (again exactly as reported in the data). I was scratching my head on why the spark timing is not following the profile established by the 100 kPa column in the main spark map until I realized that I have the base timing set at 10 deg in the constants. So what the LC is doing as a function of time is simply adding the LC spark adder to the base 10 deg and completely ignoring the main spark table altogether. If the base timing was set at the stock 6 deg, then it would be adding the LC spark-adder value to 6 deg instead of 10. I just found and disabled LC, so I'll have to see what kind of improvement I get in the WOT launch off the line. |
Re: Ugh... when new tires force you to retune! Good to know, ill want to tinker with that when i get the kinks worked out of my engine. Looking towards my next run at PIR (did my first run a few weeks ago) |
Re: Ugh... when new tires force you to retune! Yeah, if disabling it solves my current issue, I may revisit it later to see if it can help (now that I understand the logic of how it works). |
Re: Ugh... when new tires force you to retune! Yep, that was it. I disabled the launch control and the timing returned to nomral. |
Re: Ugh... when new tires force you to retune! The Table in Post #6 is only an example, just like VE and Spark values in a stock factory BIN. The docs released with S_AUJP provide the cautions below if using Launch Control. It really works if table values and invocation thresholds are set to the car's requirements. You were encountering caution #3. CAUTION:
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Re: Ugh... when new tires force you to retune! So I've been playing around with the launching lately when time permits and it still seems like I'm leaving some power on the table. Launch mode is definitely deactivated and I'm definitely getting the spark timing that I have programmed in. Basically I'm running the LT4 Vette spark table everywhere except at the cells for low rpm and high map. The TPIs like ANHT and AUJP hit about 18 deg BTDC whereas the LT4s go down to about 8-10 deg. And I'm not using launch control at this time. so is more timing here bad or good? I'm getting a little bit of knock retard... couple of deg, but I doubt that was the issue. fueling seems spot on. I nail the gas from a standstill and the AFR dips into the mid 12s. So seems like AE fueling is right. drivetrain is a 700R4 auto with 3.42 axle and the LT1 vette torque converter. Cam is a 212 @.050 on the intake so should have plenty of low end. I run open loop up to about 1800 rpm due to the better crispness of the throttle at take off. But because of that, the PE doesn't kick in until 1800 rpm even though the map and TPS are well over the PE threshold. It remains in open loop until 1800 rpm... this is visible as the SAUJP reports out when the ECM goes into PE mode. Nevertheless, the Open Loop fueling seems to be right based on WB O2 readings. So not sure it makes a difference whether the fuel is delivered via OL or PE. so given all of this I should be accelerating at least as hard than an LT4 Vette off the line, but somehow I doubt it. I can barely chirp the tires, but with my setup I'd expect to be able to blaze the tires.. I'm sure the LT4 vettes could with the traction control turned off. trying to figure out what else I could be missing. 84Elky was kind enough to look at my datalogs, but nothing obvious seems to jumping out at us. acceleration while rolling at speed is great and couldn't be happier... horrendous amount of power. Its just the off idle launch that seems to be lacking. |
Re: Ugh... when new tires force you to retune! Since PE doesn't kick in until 1800 RPM. Add some to the main SA table between 80 & 100 KPa. That should kick it up a notch. And, since it stays open loop, can also add some fuel in the same area. RBob. |
Re: Ugh... when new tires force you to retune! 2 Attachment(s) Thanks RBob. Currently my data says I hit about 12.5-13.0:1 AFR and I stay there from the time I go from idle to WOT. No lean or rich spots indicating (to my knowledge) the OL, PE, or AE tables need any adjustment? Also, I seem to be skipping over the idle speed rpms in the high map area... 1st Image below is from 84Elky's log file analyzer showing what cells I hit during the entire run. The run contained four WOT bursts, and none of them hit the really high maps anywhere near idle speed. My actual timing map is also below. Any rate, based on this data, would you still think adding more timing in the PE spark adder would help? |
Re: Ugh... when new tires force you to retune!
Originally Posted by ULTM8Z
(Post 6239320)
Any rate, based on this data, would you still think adding more timing in the PE spark adder would help? RBob. |
Re: Ugh... when new tires force you to retune! Sorry.. lack of clarity on my part... My PE spark adder is zeroed out. The main table is "what you see is what you get"... so the timing is the same regardless of whether in PE or not. |
Re: Ugh... when new tires force you to retune! I don't know the stall speed of an LT1 convertor. But below that speed you can add a bunch of SA at high load. The reason is, is to quickly bring the engine up against the convertor. In the EBL products there is a launch mode (LM) that is designed to do exactly that. Being that the load is light (just the engines rotating mass), it is safe to do this without detonation. I've used it on several vehicles with success, it even helps with stick shift cars. RBob. |
Re: Ugh... when new tires force you to retune! ULTM8Z, that area in the SA - Main Table is meaningless. An LT1 converter couples at 1650-RPM, right on par with what the analyzer is showing, so no real load prior to that, and you won't see that area lighting up much at wide open throttle off idle, so adding timing through the spark adder in the 100 kPa column will solve nothing. Adding it directly to the SA Main Table itself, which apparently you can't, would in fact help as RBob had suggested because it creates a higher average overall in that general area, not just the specific cell. You need more converter for your setup to light them up off idle, 2400 stall speed at a minimum. Either that, or put those old tires back on... ;) - Rob Edit: Didn't see RBob's response... :) |
Re: Ugh... when new tires force you to retune! Hmmm... SAUJP has launch control...lol... which is what started this whole thread! Maybe I'll play around with that a little... |
Re: Ugh... when new tires force you to retune! So if I hit the converter harder, it may improve things? I'm always nervous about higher stall converters... like the thing is going to be slipping all time during normal driving. I like how right now as soon as I touch the throttle the car moves. In any event next year I have plans for a gear vendors overdrive unit and either 3.90 or 4.10 axle ratio. So that should wake things up off the line... |
Re: Ugh... when new tires force you to retune! I have never come across an LT1 C4 w/automatic that was able to roast the tires off idle. The factory stall was just too low for the RPM band, which was essentially mid to high based. Same complaint was always heard when swapping to an HSR from TPI, power in the RPM band was raised, and loss of power down low kept the tires from spinning off idle because the factory stall coupled too soon. An aftermarket stall would put a huge grin on your face with your setup. You should also get an EBL and be done with it as well... :thumbsup: - Rob |
Re: Ugh... when new tires force you to retune!
Originally Posted by ULTM8Z
(Post 6239657)
Hmmm... SAUJP has launch control...lol... which is what started this whole thread! Maybe I'll play around with that a little... RBob. |
Re: Ugh... when new tires force you to retune! My two cents for what it is worth; even in my case, no tire spin off idle whatsoever currently with a stock stall speed, and I am using Launch Mode on top of an already averaged 28* of timing in the SA - Main Table in that same area. He needs to remember that even though his air/fuel is good in that range (1600-RPM and lower), that doesn't mean it's enough air and fuel to propel the car to tire spin, regardless of air/fuel ratio and timing. I just don't think he is making enough power down there under a real load without power braking to see any tire spin... - Rob. |
Re: Ugh... when new tires force you to retune! You may be right... Like I said, I guess I up the gears to around 3.90/4.10 next year when I do my Gear Vendors. That should give me plenty of punch off the line and with effectively an 8 speed transmission I'll never be out of the power band. All else fails, I guess I'll try the ~2000 rpm stall converter. |
Re: Ugh... when new tires force you to retune!
Originally Posted by RBob
(Post 6239769)
My understanding of SUAJP launch control is the opposite of our Launch mode. The first decreases timing to prevent tire spin, while the latter adds timing to boost power. RBob. |
Re: Ugh... when new tires force you to retune!
Originally Posted by ULTM8Z
(Post 6239903)
The launch control in SAUJP basically disables the spark map, then uses your base timing scalar and adds timing to that using a special launch control spark table. Basically figured out how it works the hard way back in post #6... lol... RBob. |
Re: Ugh... when new tires force you to retune! Maybe the folks that put together SAUJP should speak up and support it? RBob |
Re: Ugh... when new tires force you to retune! Well I guess what I'm trying to say is it doesn't add timing to your main spark map. It takes your base timing and adds timing to that. At least that's how I read the data. Depends on what we mean by "add" I suppose. it can be higher or lower than the main spark map depending on the base timing and what's in the launch control. In my case it was lower because of the way the numbers work out. |
Re: Ugh... when new tires force you to retune! ... so it was explained already that the SA - Main Table in this code is "fixed", it essentially is what it is, take it or leave it. But, is this the case for the SA Launch Control as well in this code, or can that area be added to? Pretty sure all LT4's came with a manual transmission, so it's difficult to compare your auto w/1650 stall speed to one in terms of off idle performance. I mean that was always the gist of it back in the day, when tuning a more radical cam, a manual is way more forgiving down low, whereas an auto needed a higher stall speed otherwise it was a dog down low. I still believe you need a higher stall convertor, but why not test the SA theory by disabling Launch Control, advancing the distributor two to three degrees, and launching it to see if you get tire spin. - Rob |
Re: Ugh... when new tires force you to retune!
Originally Posted by RBob
(Post 6239918)
Maybe the folks that put together SAUJP should speak up and support it? RBob The routine "removes" advance from what is programmed and ramps it back in over time. Its a power reduction so the tires will not light immediately when using a setup that able to fry the tires. My 406, HSR, hyd roller/700R4 needed this with the 2400 converter as it allowed smoother start coming up. 1st gear was useless without it. I have run this for several years now and it made life easier to setup the bin to have good driveabilty and then work backwards reducing timing and get the car to launch without sitting and spinning. Best to disable it, get your tune decent. then go back and reduce just a bit to get it the "slight" reduction in timing you desire for the launch. Should not be used until you have the setup dialed in pretty good. But if your not making enough power at those rpms to spin the tires easily then it does not do you any good. HTH Jp (back in the mix :) ) |
Re: Ugh... when new tires force you to retune! Thanks JP. Good to see you back on the board. |
Re: Ugh... when new tires force you to retune! JP -- Welcome back from going dark :lol:! As JP said, the purpose of Launch Control (LC) is to provide a way to keep from boiling the tires at launch. It's not the be all-end all because it's not integrated with the VSS and does not provide forced cylinder misfire, but it does work even with a stock converter. It's best to read the S_AUJP docs to understand the concept. In summary, LC retards spark to specified amounts for up to 3.2 seconds. BPW is not changed. LC will only be invoked when not moving (0 MPH). It can be invoked from idle or above a specified RPM once TPS% exceeds a specified setting. Once invoked, the Reference Pulse Spark entered in the LC Spark table: "0xB4B Launch Control-Spark Degrees .vs. Elapsed Time" is used (Note: it's spark relative to Reference Pulses, NOT TDC). The LC spark table will be used until a '0' value is encountered, whereupon spark control is returned to the normal TDC spark tables. Below is an example log snippet showing LC and the LC Spark Table used. The logged SA-REF spark matches that of the LC spark table until '0' is encountered after the 11.95 degrees, where control is returned to the normal TDC spark tables. Note SA-TDC values are maintained during LC, by adding the Distributor Setting (10.5 degrees here) to the LC Reference spark. https://cimg2.ibsrv.net/gimg/www.thi...30a48f4614.gif |
Re: Ugh... when new tires force you to retune! figured I'd update this thread with the latest from back in December.... basically mostly the contents of an email I sent to 84Elky who was gracious enough to work with me offline to see what could be done to help the situation... I had decided to try the AE vs Delta TPS table from the 93 A4 Trans Am (BDZL) the other day... Holy crap, what a difference! I started blazing tires again off the line and when it finally hooks up it freaking launches hard. I don't know what made me want to try that table again... I remember the last time I tried it I got what I thought was a rich bog. I had origainlly been running the M6 Z28 AE table vs delta TPS table which is quite a bit leaner at larger delta TPS values. I'm not sure what changed this time... unless somehow I made a mistake when entering it in last time....? Any rate, I know people talk about "giving up low end torque" with the Miniram over the LTR TPI manifold, but somehow I guess I wasn't ready to accept that... it always felt like I was leaving a significant amount of off-the-line torque on the table (especially since if I hit the gas just 1000 rpm higher than idle it's a freaking missile)... but now I can launch hard right off idle again... woo hoo! |
Re: Ugh... when new tires force you to retune! Post Deleted. Improperly posted to wrong thread????? |
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