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Thread: Grand Prix Top Swap Part-Throttle KR

  1. #1
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    Grand Prix Top Swap Part-Throttle KR

    I've been trying to figure this out on my own, reading, making tuning changes, checking for possible mechanical issues, but I just can't seem to get rid of the knock retard. I'll get up to around 11* (usually starting around 35-40% throttle). The car is a 99 GT that I "L67 top-swapped" with an engine I had laying around doing nothing that I used for parts (Gen III M90). I can give all of the "build" info if requested, but this post is already going to be long enough. I didn't do anything too radical, but it has some light P&P, 1.9 rockers w/ new springs/retainers, front plog (all manifolds and crossover are header wrapped), 3" catted downpipe, 3.8 MPS and DIY "cold" air intake. I have tried TR55's gapped at .050 and .055", 103's gapped at .050" and TR6IX (factory gap at .035"!!!) and am currently back to the TR55's. Engine and trans mounts are new solid units and I have poly dogbone mounts. Running an L67 MAP sensor that needs a little more tuning, but I'm only seeing 4 psi with the boost/vauum gauge (getting that figured out was an ordeal in itself). I have a wideband coming, but it hasn't shown up yet. I am running DHP, so I don't have some of the tables that HPT has. I haven't tuned anything in a long time and back then I didn't get too far into it. My friend helped me a lot back in the day (I'm borrowing his PT), but he had some memory loss from around that time.

    The base tune I made was using a stock 2000 GTP bin with GT transmission tables and I reduced the good fuel spark 2 degrees across the whole table. When I was fiddling with everything this weekend, the logs would show KR seemingly right when it was entering PE. I tried lowering the A/F ratio in PE to 11.5 and 0'd out the RPM vs Time table, giving it more AE at 30% and above among other things I will detail later. I also changed some of the TCC tables (not sure if correctly, however; this is where I don't know anything at all) and copied the performance shift tables over to the normal shift tables since it doesn't have a performance shift button, thinking it was a lockup release issue or that it wasn't downshifting when it should. I'm sure there is a lot more work to do there. Sometimes it will have 0 KR, sometimes maybe 2-4*, but occasionally it will get as high as 11*. I don't think with a 3.8 pulley and 4 pounds of boost that I should need to lower the timing any more.

    I went back to the base tune with a few tweaks to try and start over. I have a couple logs I'll share, but they don't show the massive spikes I occasionally get since it decides to not show up when I'm logging sometimes. I'm going to take another log with this tune later today, but going back to GT TCC tables with performance shift tables copied over to the normal shift tables. I'm not sure if sharing the *.bin file will help since HPT uses *.hpt, but I can share those also or screenshot certain tables. The first bin/log has the following applicable changes to a stock GTP file:
    99 GT Transmission tables
    EGR disabled
    Good_Fuel_Spark -2*
    P0243 removed (no boost solenoid)
    Cat_Protection_Coolant 284*
    PE_RPM_vs_Time_A/F zero'ed

    I went back to another tune I made with a lot of changes. I will attach a scan from last night and one from this morning. The second and third bin/log have the following changes (in addition to the ones previous):
    Base_PE_A/F 11.5 from 50-284*
    Traction Control Removed
    Closed Loop Idle Spark Correction (AP On/Off) 0'd
    AE TPS Re-allow 30% throttle
    AE Enrichment +5% @ 30% throttle and below, +10% @ 35-75% throttle, +15% @ 80+%
    Closed Loop Desired A/F 14.2 (running E10)
    PE Enable TPS stock
    Bad Fuel Spark reduced
    Good Fuel Spark reduced by up to 3*
    Peformance shift tables copied over the normal shift tables


    Any help would be greatly appreciated. I've been racking my brain for days trying to figure this out.
    Last edited by pwmin; 02-18-2021 at 11:51 AM.

  2. #2
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    A few things I forgot to add that might help: L67 injectors, fuel pump re-wire. I've also tried 2 different MAF sensors, one from the GTP engine and one from the GT (same part numbers). I have shortened dogbones, but it doesn't seem to change anything when I switch them out to the regular ones and there seems to be plenty of clearance between the downpipe and the firewall and sway bar. The struts are completely shot, but I don't see how that would cause it. I'm waiting for tax returns so I can get coilovers. I did at one point pull the supercharger belt and didn't get any KR. I haven't tried seeing if 100 octane gets rid of it, but I don't think it's false. I want to run E85 eventually, but want to get this sorted out first. Seems like if I roll into the throttle, it's fine, but if I go from say 5 to 35 or higher, that's when it usually shows up. If it's in the correct gear, it seems to keep it at bay, though.
    Last edited by pwmin; 02-18-2021 at 01:17 PM.

  3. #3
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    Uploaded a couple different bins and took a few more logs. The first one, I changed the TCC files back to stock GT and then copied the TCC performance shift files over to the normal shift tables. The second log I went back to the first tune except with copying the TCC performance shift files over to the normal shift tables. I'm going to copy all of the performance shift files over.2-18-21c2000GTP99GTTransBasicsSCTMCL0AE14.2PerfShiftc.csv2-18-21d2000GTP99GTTransBasicsPerfShift.csv

  4. #4
    First off, I would definitely stop messing with it until you get the wideband installed. It's very possible it's running quite lean, or even way too rich. Next up after you get the wideband installed I would suggest pulling another 2 or 4 degrees in load and then slowly feed it back in until you get some KR, then pull another degree back out. If you find yourself still showing the same KR after correcting the AFR and pulling timing, I would suggest throwing some really good fuel in it and adjusting the knock sensor sensitivity. From there you will likely need to retune timing again. It would be beneficial to get on a dyno for all this, as it can become quite tedious on the street trying to do pull after pull to fine tune the knock sensors.
    Owner/Tuner@Evolution Automotive Performance
    Lincoln, Ne

  5. #5
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    Thanks for the input. I'm going to get some logs with the wideband this week. It was supposed to show up last week, but I finally got one and it's almost ready to go, just need to do a couple things yet and I'm out of town right now. I'll update when I get some new logs.

  6. #6
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    Got the WB installed and appears to be close to commanded AFR. Was still getting KR with toluene added for about 98 Octane. Used a 98 GTP file as a base and KR went down to less than 1 max even with stock timing tables. VE table is the only one where I see any difference in the 98 vs the 00 bin.