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Just posted my results on '91 #473 after SW headers and exhaust, timing for 93 octane, fidanza FW and Haibeck chip/tune. 345 rwhp / 349 rwtq. This seems low to me, even with a hot engine, for the modifications done so far. Assuming 15% drive-line loss, the engine sits at 402 hp, a gain of only 27 over stock..
We did not have a tailpipe sensor this time, but past runs (have metal matrix cats installed) put the AFR at tailpipe below 12 for the entire pass. Average was between 11.6 and 11.9. I'm going to install a wideband O2 sensor permanently (ahead of the cat) and install the display unit in the center console to measure accurately.
I'm very competent with HP Tuners, but this is OBD I, so no go there. What is the best tuning package for these cars? I have one of Marc's piggyback chips in the ECM, so would this prevent me from doing any fuel tuning on the engine?
Does the LT-5 "want" to be at an AFR of 12? Seems very rich to me as my LS engines have always been tuned to about 13.5..
get a fuel pressure gauge with a very long hose and take the car for a drive to make sure it can maintain 50-52 psi to redline. If one of the fuel pumps is going out it might taper to 45 psi after 5500-6000 rpm. The stock tune is rich- it should run ok with typical bolt-ons.
A. As Lee said, port the intake. The LT-5 NEEDS air.
B. For OBD-1, go to thirdgen.org, Moates.net, and Tunerpro.net
Th LT-5 likes a 12.8-13.1 AFR. Make sure you consider the stoich for the fuel u are using, i.e. 10% ethanol. Frankly, before I do any WOT tuning, I need to get part throttle right since all fueling is a derivative of VE tables.
Then Spark.
Thanks! I'll pull the intake and port/polish after the Texas Wannagofast race on November 13. Marc calculates I'm missing 16 HP at the crank for mods to date, so not too far off.
Will check out the tuning platforms. I'd love to be able to tune my LT5. Sure miss doing it on my LS2! HP Tuners made it nice!
Posting my response to your pm for the benefit of others that may be interested in the topic.
"U can use any LT-5 ECM however, the bin file needs to be correct for that year. For '91, the Mask is $AF and $AFA. It looks like the .adx is less critical. I have used a 90 .adx and it still reads the ALDL stream correctly.
I would use the $AFA mask, but you will need to read the bin, then see if it is using the AF or AFA setup. These are similar but they added a few extra lines of code in ALL the LT-5 masks which is why u will see an "A" variant of each mask ID.To tell if u have the correct mask, look the scalar for Inj. #/hr. The entry should read 22.7. Another parameter to look for is Cyl. Volume which should be .71. If it doesn't, close the .xdf but make sure you don't save the bin w that .xdf open."
Thank you Dominic and thank you for all of your counsel.
Fellow tuners, I went with TunerPro RT, Craig Moates APU 1 and an AEM wideband O2 sensor. I'll start another thread as I get into the tune of my LT-5 to share my journey. I've enjoyed tuning my LS engines and look forward to learning how to apply those tuning nuggets to my LT-5..
Well the last few days have been a bit challenging. With some great help from Jeff on ZR1 Net Registry, I've got an ADX which allows solid data logging with the Moates APU1 in bypass mode, but can't get my wideband data to come through in this mode. I've added the wideband values to the ADX as well as the dashboard (gauges) for AFR and wideband volts. Per Moates support, I need to be in APU mode to bring the A/D channels through, which shuts down the ALDL connection. Multiple experts helping me which is very appreciated. Hopefully we will identify where I'm off and I can share the solution with everyone.
One point re: WBO2 w ALDL. I never went forward w that because the ALDL is slower than the frame rate from my Wide Band. In fact its double. At higher rpms you'll lose some of the datapoints for properly adjusting AFR.
Thanks for that tip. Dave (Moates) and Mark (TunerPro) are going to look at my ADX and see what they can do. If I can't get this going, I'll complete my part throttle VE tuning with existing tools and then seek another solution to capturing my wideband O2 data at WOT to get the PE set correctly. Bummer if I can't find a way to get a complete datalog set..
Working with Dave Blundell and Mark Manzur, who were both superb, along with a starter *.ADX from Jeff (Thanks!!!), I've finally gotten a good data logging system.
Tied in 0-5V DC analog signal from AEM to A/D buss on back of APU 1 (note, it is actually wired to Channel 1, which is the first connection outboard of the ground lug on the A/D buss, BUT, it is arriving as Channel 2, so I needed to move the offset from 65 to 67).
On Dominic's recommendation (thanks to him for all the counsel and help!) I'm replacing the existing Narrow Band O2 sensors with new AC Delco AFS74 sensors.
I've created some additional history tables to ease the BLM tune to optimize the VE tables. I'm still working on some monitor frames (TunerPro RT), so will post up my final tuning ADX when completed.
The Analog channels cannot be streamed with the ALDL data unless the APU 1 is in APU mode and TunerPro RT preferences are set to look for the APU, rather than a plug in(pass through). To get TunerPro RT to communicate through the APU 1 to the ALDL port and ECM, the "Connect" command needs to be set to <none>, otherwise you will NOT be able to connect. I'll post up more as I learn how to move from HPTuners to TunerPro RT. I've got a good start now though, thanks to the help from Dave, Mark, Jep, Dominic and Jeff!!
Last edited by jss06c6; 11-29-2016 at 03:02 PM.
Reason: typo
That's great! It is always good to work with people whose products support each other. I already have access to chip programming hardware so I never had to buy the APU1...that and I live in CA so I don't need to go too deep into the VE tables for an almost stock car.
Lots of data logging. First was to get VE Low, then VE high tables set to hit BLM of128 in all MAP/RPM cells. Got close. Driver side is about 3 BLM units richer in low rpm/map region than passenger side. Averaging 126-128 on driver side and 128-130 on passenger side. They are 1-2 BLM units apart above 2000 rpm and MAP of 40 kPa.
Commanded secondaries open to tune VE tables for port throttle open. Had to spend quite a bit of time with the VE low table below 2000 rpm and MAP below 40 kPa. Engine wants to run rich in this zone. Finally got it to average 125 on driver side and 128 on passenger side. Called it good and started wot tuning. Moved port throttle open versus TPS down to allow secondaries to open earlier. wot pull from 2200 to 6000 rpm in 4th gear showed knock retard across this area (100 kPa). AFR steady between 12.5 and 12.6 so will pull some timing (1 degree) and re-log.
Silly part is that I'll have to repeat this exercise when I pull the plenum and port the top end! Oh well, it's a enjoyable learning to tune LT5 with OBD1!
10-28-2016, 05:42 PM
OBD I tuning and Wideband O2
