Hi All,

I just finished my build of a new engine for my 1991 Z28 Auto Trans. I'm running the 1227730 ECM ($8D). The tune I am currently using is based on my old tune from my origional 350 that had factory cam, heads, and the same stealth ram intake, and 1.6 ratio rockers. The only changes I made so far were upping the idle to 750, and copying the VE tables from the similar year corvette, which I figured would at least get me a little closer to my current build than my old one. It fired up on the first turn of the key, and I set the base timing to 6 Deg per my current tune. The car is still up on stands, but I should be ready to put it back on the ground soon, just need to get a few things adjusted around so my steering shart stops contacting my exahust header...

The rest of the engine build was discussed in the build thread below:
https://www.thirdgen.org/forums/tech...ispreloading=1

Engine Specs:
- Holley Stealth Ram Intake with dual 58mm throttle body
- D.U.I. Distributor
- High Flow Water Pump
- SLP 3/4" Shortie Headers
- Billet aluminum adjustable fuel pressure regulator set to 45 PSI with vacuum disconnected.
- 2600 RPM stall 9.5" converter in my reworked 700R4 trans. Have to see how long the trans lasts...
- AFR #1040 195 intake runner, street CNC aluminum heads with 65cc chambers.
- Smeding Short Block including full rotating assembly, oil pump, oil pan, timing set, timing cover, hydraulic roller lifters, dog bones, spider, and camshaft "450 HP" .544"/555" Lift W/1.6 rockers, 231°/236° Duration @ .050”, 111 LSA, 9cc 'D' shaped dished pistons to achieve a 10.46 CR with a 0.032 head gasket and resulting in a 0.042" quench.(They call it their 450hp Extreme cam, but in their dyno test sheets they use a carburetor and 1.5 ratio rockers. With my 1.6 ratio rockers and fuel injection it may make a bit more...I'm expecting this build to be in the ballpark of 460-480 HP at the flex plate)
- Comp Cams Ultra Pro Magnum 1.6 ratio 3/8" non-self aligning rockers
- South Bay 36 lb/hr injectors
- 255 LPM fuel pump
- 30-0300 AEM 52mm Wideband UEGO Air Fuel Ratio Sensor Controller Gauge in Passenger exhaust bank. (Wired to ECM for logging)
- Tuning with Moates Burn 2 chip programmer and ALDU1 datalogger
- 3.23 ratio 10 bolt posi rear end, with reinforced cast aluminum cover.

Changes to AUJP BIN (1227730 ECM / $8D):
- Tuning and logging with Tuner Pro RT V5
- Idle set to 750
- Injectors updated to 36 LB
- Displacement scaler updated for 383 displacement
- VE tables copied from Corvette ANHT, after lean condition, I upped all values in both tables by 1%.
Unrelated:
- Fan temps adjusted
- Torque converter lockup adjusted

I have been reading as many tuning threads and articles as I could find that were applicable. My understanding was to start with 30 sec data logs at incremental RPM ranges. Then use the BLMs and divide the average value by 128, then multiply your VE table fields for the given parameters by that ratio. My current questions is do the BLMs take a while to start working, all of mine for all of my logs are 108, which I believe is the minimum they can register. Depending on the engine speed, my wideband gauge is reading between 14.5 and 16 or so. Does this make sense? I want to make sure before I start making the changes and burning a new chip.

I could share the data logs, but I'm not sure how... could someone fill me in?

108 is the minimum, yeah. If the integrator isn't pegged at 108 either, then the ECM may have just barely been able to trim your fuel back to stoich... hence the decent readings on the WB.

Keep in mind with the WB as your tuning, since you have it in the passenger side exhaust... Because the ECM only runs off the driver side O2 sensor, it'll tailor the fueling to what's going on with the driver side. So the passenger side is going to get whatever it gets. Hence you may see situations where the BLM or INT is showing one thing, but the WB is showing another... if the ECM is trimming the fuel leaner due to the driver side, but the passenger side doesn't want to be leaner, the WB will read lean. And the opposite is true for rich. Just keep that in mind so you don't get confused about seemingly contradictory readings.

Also, I happened to see in your signature it's a 383. I'm assuming you've changed the displacement scalar accordingly already?

For posting datalogs, yeah I'm not sure why they won't allow xdl files posted directly here. What you might try is changing the file name from .xdl to .txt or something like that. Then when we download, we can change it back to .xdl. Otherwise, you can email me the log.

Yup, I did update the displacement scaler, so that should be good, just forgot to mention it above. Honestly it starts really easily, so at least for idle, it seems like I could be vaguely close.

I am curious to hear people's opinion here though. If I'm driving around, or doing a data log, how lean (or rich) is too rich, and I need to back out, or stop the log. I've heard about 13-16, but that is a pretty tight range when tuning, I was seeing 16 occasionally while trying to get my logs around 1700 rpm... Of course, I would not call that good and stop trying to get closer to 14.7. but if I see 16+ for 30 sec while running a data log, am I putting my engine at risk?

I actually put the WB in the other bank on purpose, so I could see if there were any significant anomalies. Hope this was not a bad idea. I would think unless there was some significant issue, your AFR in each bank should be pretty similar, wouldn't it?

I'll try posting the logs when I get home.

16-17 afr at light throttle will not hurt the motor but lean enough to misfire will screw up your data logs.

Concur. I actually run about 16:1 during light cruising in highway mode. Doesn't seem to harm anything. As soon as I give a little throttle it instantaneously reverts back to 14.7 commanded AFR... it's actually so seamless I don't even feel it.

14.7 is not necessarily the end all to be all for all driving conditions.

During normal street driving, in steady state, sure, 14.7:1 works good. On a performance engine, when in part throttle acceleration, I'll momentarily dip to about 13:1 for accelerator enrichment during decent throttle transitions, and then could be around 13.5 to 14:1 during moderate acceleration. I've found that I get better part throttle performance with a little richer AFR. You get better follow-through from the AE fueling to steady state fueling in terms of how it feels via seat of the pants.

In 8D, if you want to richen the mixture a little, you'll need to play around with your O2 rich/lean thresholds by adjusting the threshold voltages a little higher.

The nominal threshold voltages are in table...

Loop Closed Param, FAST o2 NOT Idling Rich/Lean Boundary .vs. MAP (Swing Point)

The upper and lower tolerance tables are

Loop Closed Param, SLOW o2 NOT Idling Rich/Lean LOWER Boundary .vs. MAP

Loop Closed Param, SLOW o2 NOT Idling Rich/Lean UPPER Boundary .vs. MAP

Which side the WB O2 is on doesn't make a difference, as long as you know how to interpret the results.

Ah, you have to go into the advance response option for attachments. Please find my data logs attached. They are all in park. The car is still up on stands at the moment, but I hope to get it down on to the ground and moving soon.

As suggested, I changed the .xdl to .txt to allow me to post, so just change it back to view the logs...

Questions/Observations/recommendations:

1.) Raise your TPS voltage up to .54V at closed throttle. You're at .41... I think the ECM starts doing funky stuff with TPS voltage and TPS% when you get down that low.

2.) I think you'd benefit from increased spark timing at idle. Try bumping up your spark table to about 25 deg. The 4th gen LT1's are up into the 25-26 range with their short runner manifolds. Do the increase on both the main spark map as well as in the closed throttle spark advance tables.

3.) Your commanded idle speed of 750 rpm is probably too low for that cam. I'd be up at least at 1000 rpm in park so you get some modicum of idle vacuum for your power brakes. It's good you have a 2900 rpm converter for when you're in drive. You'll probably need some sort of vacuum reservoir to help with your brakes at idle. The last idle bin at full operating temp had upwards of 60 IAC steps to maintain ~750-800 rpm. What I'd do is program your bin to run about 900-1000 rpm in park. Then open your throttle blades until you get down below 10 steps at idle in park. I think you'll get better off idle tip-in response like that as well.

4.) You might want consider switching over the S_AUJP at the ground floor here. It has a lot more capability, in addition to being set up to have TP read and record WB O2 data. It'll also allow you to run open loop idle, which may be needed with this cam. You'd then tune the idle with the WB O2. You're throwing a TON of unburnt O2 into the exhaust stream due to the amount of overlap that cam probably has. It'll wreak havoc on the O2 and trying to dial in your fuel mixture.

5.) Where is your MAT sensor located?

6.) For tuning your VE tables, I'd have the WB O2 on the same side as the NB O2. The reason I say this is you may want to change your O2 R/L thresholds to have the ECM aim for a richer AFR. In which case, your VE tuning would be driven by the new R/L thresholds since the BLMs.... richer R/L thresholds will have the effect of raising the BLMs. I'm attaching my VE tuning tool. The tool uses the history tables in TP to dial in the VE tables. I'm also attaching my adx file that has the needed history tables set up to work with the VE table. When you get the car on the ground and running, this should help with the VE table tuning. I had to change the adx file to .txt. So simply change the extension back.

7.) Did you update your Injector voltage offsets table for your 36 lb injectors? I'm assuming they're Bosch-III style. What P/N are they?

8.) Something is up with your P/N neutral switch. The ECM thinks you're in gear when you're in park. This can cause funky issues with the idle as well.

9.) You might try opening your throttle blades a bit to bring down the IAC steps. I think with your cam, you probably want to not rely on the IAC so heavily to maintain idle speed.

10.) You can also try disabling the idle speed correction spark tables. There's a table for idle speed spark advance vs RPM error and table for idle speed spark retard vs RPM error. Try zeroing out both tables. Might help reduce idle speed "hunting".

Also, what TP xdf file are you using? If not S_AUJP, I'd switch over to that too. I've attached the latest v7 version. You're likely going to need the parameters this xdf has over the standard 8D xdf.

Again, change .txt do .xdf to use it.

Wow, a lot of great feedback there! I'm going to re-read it all 12 more times, then I'll try starting to implement and most lickely respond with many more questions... Thanks!

Subscribed. Just for the interest as I'm not an EFI tuner.
I can say though I can mange power brakes with idle vacuum in or around 10". I'll caveat that by adding that if the idle pulls down any (say sub 800) then I can the feel brake pedal getting low. With a cam such as mine (280/284, 232/236, 108LSA , 104 ICL) it'll idle at 900. 850 probably but that RPM tends to pull the vacuum down as mentioned. That said, this carbureted engine is far from being tuned. I have fueling and ignition timing carried over from the previous iteration which is quite far removed from the present spec. We're in a similar situation in that regard.
The comment about a 16:1 AFR is something I can support. I've a ratio around that for highway cruise. Along with a ton of spark advance. 45°+ has been observed and the MPG responds accordingly. As in, not bad for a little hot rod engine . 21 US MPG more or less.
Anyway @raptere , sounds like you have some capable hands to guide you through this process.
Good luck as always.

Answers/questions in BOLD.

1.) Raise your TPS voltage up to .54V at closed throttle. You're at .41... I think the ECM starts doing funky stuff with TPS voltage and TPS% when you get down that low. So, for this I just turn on the ignition (Engine off) and watch the TPS voltage from my laptop, then loosen the screws on the TPS and rotate until I get 0.54V then tighten it down?

2.) I think you'd benefit from increased spark timing at idle. Try bumping up your spark table to about 25 deg. The 4th gen LT1's are up into the 25-26 range with their short runner manifolds. Do the increase on both the main spark map as well as in the closed throttle spark advance tables. Would I be only increasing the value at idle which would be idle rpm, and idle is it vacuum on the other side of that table. Then smooth it out to the rest of the table? Or should I increase the whole table proportionally until idle is at 25 deg?

3.) Your commanded idle speed of 750 rpm is probably too low for that cam. I'd be up at least at 1000 rpm in park so you get some modicum of idle vacuum for your power brakes. It's good you have a 2900 rpm converter for when you're in drive. You'll probably need some sort of vacuum reservoir to help with your brakes at idle. The last idle bin at full operating temp had upwards of 60 IAC steps to maintain ~750-800 rpm. What I'd do is program your bin to run about 900-1000 rpm in park. Then open your throttle blades until you get down below 10 steps at idle in park. I think you'll get better off idle tip-in response like that as well. 1000 sounds like a lot to me, I'll try going up to 900. Honestly 800 felt high so I lowered it to 750 in those tests. It honestly idles pretty smoothly I thought. To get the IAC steps down to ~10 I just idle and look at my laptop as I turn in the throttle stop screw on my throttle arm, opening the butterflies until it drops to about 10?

4.) You might want consider switching over the S_AUJP at the ground floor here. It has a lot more capability, in addition to being set up to have TP read and record WB O2 data. It'll also allow you to run open loop idle, which may be needed with this cam. You'd then tune the idle with the WB O2. You're throwing a TON of unburnt O2 into the exhaust stream due to the amount of overlap that cam probably has. It'll wreak havoc on the O2 and trying to dial in your fuel mixture. Is this the ADX file were talking about? If not see the XDF file I'm using in the last point but consider the same comments. I definitely want the ability to record WB O2 data. I did look at that S_AUJP, and it seemed like it had a ton of forced in duction stuff I didn't need. It also doesn't seem to break down the different items into categories which I really like about the 8D_90-91_Corvette_Form_TunerPro-site.adx I'm using now. It also didn't seem to do the calculation for me on some of the more complicated parameters like mine does. When I went to look at cylinder displacement it didn't appear to be in CC's looked like some other unit, also the fuel injector flow rate was not in LB/HR, it was some other unit I didn't recognize... Is it possible, or logical for me to use the one I have now, but add the functionality to data log WB data, and to be able to use the extended spark and VE tables. I see them in my version, but I'm not sure how to enable them, since the regular ones are there too, and I see no flag to toggle between the two...

5.) Where is your MAT sensor located? My MAT sensor is in the hole in the underside of my plenum right between the two sets of runners. I can share a pic if necessary, or take a look in my engine build thread linked above.

6.) For tuning your VE tables, I'd have the WB O2 on the same side as the NB O2. The reason I say this is you may want to change your O2 R/L thresholds to have the ECM aim for a richer AFR. In which case, your VE tuning would be driven by the new R/L thresholds since the BLMs.... richer R/L thresholds will have the effect of raising the BLMs. I'm attaching my VE tuning tool. The tool uses the history tables in TP to dial in the VE tables. I'm also attaching my adx file that has the needed history tables set up to work with the VE table. When you get the car on the ground and running, this should help with the VE table tuning. I had to change the adx file to .txt. So simply change the extension back. Ha, great, I just wended the bung in now, thinking it would be good to have some visibility of both banks. How critical is it for me to swap it over to the other bank? I'm hoping I can tune as is, with reasonable success... I do the welding myself, I just don't feel like pulling the exhaust off again and getting another bung and a plug, maybe I can do it down the road, if it will really benefit things...

7.) Did you update your Injector voltage offsets table for your 36 lb injectors? I'm assuming they're Bosch-III style. What P/N are they? I changed the flow rate, nothing else related to the injectors... They are from SouthBay, 36 LB/HR PN 4414, but I had to exchange them for the variant without the extra spacer since the geometry of the Stealth ram is a little different than standard TPI. (36lb 5.7 Camaro Firebird Corvette D3 Fuel Injectors) I saw no other specifications identified on SouthBay's site for the injectors...

8.) Something is up with your P/N neutral switch. The ECM thinks you're in gear when you're in park. This can cause funky issues with the idle as well. This is a physical switch on my shifter, right? I know I had some issues with my reverse lights not coming on and off at the right time, so I had to adjust that switch, if there is a parking one down in there too, I'll have to take a look and make sure it if functioning correctly...

9.) You might try opening your throttle blades a bit to bring down the IAC steps. I think with your cam, you probably want to not rely on the IAC so heavily to maintain idle speed. Duplicate of 3 above.

10.) You can also try disabling the idle speed correction spark tables. There's a table for idle speed spark advance vs RPM error and table for idle speed spark retard vs RPM error. Try zeroing out both tables. Might help reduce idle speed "hunting". It honestly didn't seem like it was hunting so hard for the idle speed. But I can try this if you think it will be better, any negative side affects of this change?

11.) Also, what TP xdf file are you using? If not S_AUJP, I'd switch over to that too. I've attached the latest v7 version. You're likely going to need the parameters this xdf has over the standard 8D xdf. I'm using the $8D-1227730-V1.xdf.

TPS voltage => Correct. Engine off, key on, adjust TPS until ~.54V, then tighten it down.

Idle spark timing => Just do the idle rpm areas. Closed throttle spark table you can add a few deg to 0-800 rpm. Main spark map, upper row is manifold pressure, not vacuum. Look for the MAP Value at whatever idle speed you settle in at, then find the cells that correspond to that rpm and MAP value and add in some timing there. Then smooth around the surrounding cells to blend. Important that the closed throttle table match the timing values in the spark map where you're actually idling in terms of MAP and RPM. If it's very different, you can get off idle stumbles.

Idle speed => Increasing the idle speed certainly isn't mandatory. Do what you think is best and to your liking on idle quality. If your'e happy with idle quality at 750 rpm, by all means go with that.

S_AUJP and WB O2=> Again, you can use whichever 8D files you want to. Keep in mind though my Miniram start bin is based on S_AUJP, albeit v5. Just that you can't get the ECM to read the WB O2 (or report out to TP) without the S_AUJP files (bin, adx, and xdf).

MAT Sensor => Do you have an air tube on the throttle body? Or just a filter hanging off the throttle body? The Miniram start bin I sent you assumes there's an air tube and the MAT sensor is in the air tube. For a performance engine, it's much better setup than having the heat soaked sensor in the metal plenum.

WB O2 positioning => Not the end of the world to have WB on the opposite side. Just need to keep that in mind when comparing WB O2 readings against NB O2 and BLM/INT. Sometimes they can seem contradictory when they're on opposite sides.

P/N Neutral switch => yeah, that's an imperative that you get that fixed. You'll get various idle gremlins w/o it... probably will be exacerbated by your radical cam too.

Idle hunting => Ok. You obviously can see what the car is physically doing whereas I'm only looking at data. So this also isn't a mandatory thing. Just a little trick that can sometimes smooth out minor idle speed variations.

Injectors => Can you see a p/n molded into the injector bodies? One that starts with 0280 or 280? The voltage offsets table very likely needs to be adjusted. If you can find that p/n, I can try to find the data online. Or Southbay may have the info.

Alrighty! Got my IAC to stabilize at 8 once warmed up, and my TPS sensor set to 0.55V.

I also set my idle to 900 rpm and advance at idle to 25 and added another data log, with some idle and a couple of revs fully warmed up:

Injectors => From your link to Southbay, I found the p/n 170843 on the injector bodies. That's apparently a BMW p/n that cross references to Bosch 0280155823, 19 lb/hr at 43 psi

https://www.injectorplanet.com/produ...23-bmw-1707843

Southbay must modify them to convert to 36 lb/hr

Yeah, you might contact them to see what voltage offsets they recommend.

Regarding the Idle surging, I looked those two tables up, and both are 5 deg in all cells. Maybe I'll try changing them both to all 3's.

Those settings should be pretty good I think. How does it run?

One thing I"m noticing is that you're showing .78% throttle when I believe the throttle is actually closed? It should be 0%. Make sure you shut the power off completely after you adjust the TPS voltage, so the ECM can re-zero the % on the next start up.

Yeah feel free to play around with those tables. It's all about seeing what the engine likes and then going with that.

I guess that picture is just a representation... I just checked my actual injectors and they say Bosch 0280155830.

These are them on the site you linked to:
https://www.injectorplanet.com/produ...42399488409818

They say they're 34.6 Lb/hr @ 43.5 PSI, I did up mine to 45 PSI. Are you able to identify any changes to my BIN I need to make accordingly? Or should I still just contact Southbay?

Quick search online didn't turn up anything online.

That said, I'm running Southbay's 0280155831 (32 lb/hr). I couldn't find anything on those either.

I'm actually running 4 of those on the front 4 cylinders and 4 of the 0280155759 (30 lb/hr) on the rear 4 cylinders. The Minram's fuel distribution is very similar to 4th gen LT1's, and when I looked at the idle fuel trims on the sequential injection LT1's, GM trimmed the fuel ~10% richer in the front 4 cylinders, and that continued all the way to 40% throttle. So with a batch fire system, the only way for me to replicate that is by putting 10% bigger injectors on the front 4 cylinders. Had a huge improvement in idle and low speed driveability.

All that said, without offsets on the 831's, I'm just running the offsets I had on the 759's (which I know are accurate since the 759's cross reference to a Ford Motorsport p/n, and I have Ford's datasheet on those).

So absent any other info from Southbay, you could use my injector offsets from the 759's.

The other thing is to zero out the low pulsewidth compensation table. That "helper" table is a relic from the old Multecs which were inefficient at low pulse widths. The Bosch-III's don't need the help, so it's extra fuel you don't need. This will help on your low BLM's. It may not pull your BLMs up by itself, but it'll make it easier to adjust later when you attack the VE tables.

I'm probably over thinking this but I wanted to share some things I found and calculated.

Here is a comparison of some injector data I found, and average taken to see if it would be a better fit for my 36lb ...830 injectors.



I also found the following post, which may be true, given what I found in the bosch catalog attached...

No its good you're doing the research. I definitely applaud that.

I also cataloged a few differen't p/n's during my search on the 831's last year. I'll compare notes later today.

The table pretty much matches what I have.

Not sure about the assertion that the internals are all the same for those injectors.

I used injector data from the internet on several sets of injectors and was never happy with the results. For me close was not good enough. The voltage does change with alternator output, the fan or ac compressor cycling, lights on and other things. I finally bought a new set of new Bosch ev14 35# injectors that came with measured data for my injectors. Huge difference. Almost factory smooth idle that I never expected to get with my cam. I can no longer feel the ac compressor cycling while idleing at a stop lights.

That's completely valid. I too previously had trouble with voltage offsets on a previous set of injectors to the point I took them off and threw them in the garbage. For the next set (my 30lb, 280155759), I made sure there was a factory datasheet for them (turned out they cross referenced to a Ford Motorsport P/N, and there was a Ford datasheet on them).

Same thing happened to me... soon as I fired up the car, I knew right away the problem was solved. Snappy start up, silky smooth idle, smooth throttle transitions... total night and day difference.

But I still think a few microseconds one way or the other won't make much difference.

So, I guess I didn't even realize exactly what I had...

I re-read the Bosch Technical doc and found that my 830 injectors are the same as the 868, same flowrate except with two spray patterns separated by 20 degrees instead of a single conical spray pattern. Since I have the specs for the 868 injects, I think I should be able to use those numbers as is. I'll give it a try and see...

S_AUJP and WB O2=> Again, you can use whichever 8D files you want to. Keep in mind though my Miniram start bin is based on S_AUJP, albeit v5. Just that you can't get the ECM to read the WB O2 (or report out to TP) without the S_AUJP files (bin, adx, and xdf).

So, as I mentioned, I definitely want to be able to wire my WB directly to my ECM. Tell me what exactly I need to do or share a link if this has been well outlined before. Based on my reading I run the 0-5v output wire to a specific connection on one of the connectors of my ECM. How do I actually do that though, can I buy a new pin to connect to the wire and lock into the connector? Then I believe I must wire the sensor ground wire as well, but I think I can just wire that to any ground, even the same ground as I'm using for the main gauge ground, right? If I must switch to the S_AUJP, then I guess I need to, or is there a way to modify the BIN I have now for it to work?

MAT Sensor => Do you have an air tube on the throttle body? Or just a filter hanging off the throttle body? The Miniram start bin I sent you assumes there's an air tube and the MAT sensor is in the air tube. For a performance engine, it's much better setup than having the heat soaked sensor in the metal plenum.

I don't really want to break the seal, and ruin the gaskets between my upper plenum and the intake at the moment, but I guess when I find some more time, should move that sensor to the plastic Y pipe that goes above the filters? Drill and tap a hole and move the sensor there. I believe there is even a flat surface, where there is sometimes a sensor mounted for other uses on the backside of it, but it is not drilled for my application I do have my TB heat crossover removed, so I'm not sure how much the manifold temp makes a big difference once the air is flowing over the sensor... I guess the plenum definitely gets warm to the touch, but I would not say hot, unless I'm running it hard, then parking it... I normally pop my hood after my auto x runs to cool down, and also have converted my factory hood blisters to be functional, so I now have some hood ventilation as well...

You basically need to get the S_AUJP suite of files. bin, adx, and xdf. v7 is the latest (which is what I'm running).

https://www.thirdgen.org/forums/diy-...ion-7-now.html

You then need to get an ECM terminal (unfortunately you need to buy a boat load to get just one, but it's pretty cheap).

https://www.ebay.com/itm/12116044303...3ABFBM6s6v1rtl

Use one of these terminals to connect the 0-5V WB output wire to terminal F14 (it's a secondary MAP Sensor input that GM never used). Just make sure your grounds are excellent for the WB O2, the ECM, and the WB gauge.

Then there's a bit of setup in TP to do, but can tackle that when/if you get to that point.

As far as the MAT sensor, if you can access the harness connector and remove it w/o removing the plenum, you can just leave the existing sensor there unconnected.

The main thing is the heat soaking of the metal bodied sensor in the metal plenum. GM did put a table in the code to compensate for this, but IMO, for a performance engine it's better to have the MAT sensor in the air tube and then de-activate that table. The early speed-density 4th gen LT1's had the plastic sensor in the air tube but still used that compensation table (though you can see how they adjusted for not being in the metal plenum). You can potentially use that table and see how works.

I just deactivated the table completely and found that I get much more consistent operation across a wide range of coolant and air temps.

You have to tweak the VE and other fuel tables a bit since it'll want to run a little richer, but it's worth it IMO.

Just took my maiden trip, short very tame trip around the block. It runs, the wb seems like it's all over the place under light throttle, seemed to stable out a bit with maybe 25% throttle, but as the revs claimed, it leaned out. I took a log of the whole thing, and can post it when I get back home.

I looked into the IAT sensor, I see how the new ones have a plastic probe, instead of brass.

I ordered one of them that came with a new wire and connector, hopefully this extends far enough to get into the y pipe.
https://www.rockauto.com/en/moreinfo...035795&pt=5072

My plan is to drill and tap a hole here, and install the new sensor, this the right idea? I did see how the sensor was reading something like 125 deg when ambient was more like 70...

The 3.1L air cleaner lid had a brass insert in that spot for iat. You can use a 93 camaro iat and grommet if that area is to thin once drilled.

https://www.eficonnection.com/home/p...et-gm-24504388

Do you know what the thread is on the v8 sensor? I wonder if I could find a threaded bung with a lock ring kind of setup to use...

It’s npt, can’t remember if it’s 1/4 or 3/8

@ULTM8Z: I am thinking the tables from your bin with your Mini Ram Intake are probubly a closer starting point than the corvette ve and ignition tables are, I may give those a try then start tuning from there. Pretty sure my BLMs are all still at the minimum, which doesnt tell me much... Or do I need to put some miles or operating time on the tune for those values to become usefull for tuning?

yeah, you need to drive it around a bit and let the BLM's develop and settle in.

The only thing is, with the Miniram start bin, I wouldn't start tuning on the VE until you get your air sensor relocated. The ECM will get confused.

I found it in an online listing, it's 3/8 npt.

I'm thinking one of these should work perfectly, if threading it directly into the plastic, doesn't seem secure enough...

Joywayus 3/8" Female 1/2" Male Soild Brass Water Tank Connector Bulkhead Tank Fitting With 2 Rubber Ring Stablizing https://a.co/d/hOVVgRl

I can definitly feel a reduced level of vacuume I'm my brake pedal, the pedal feels much firmer, more like the feel when the engine is off. That said, they still seem to function no problem.

Someone did mentioned a vacuume canister may help given my cam and lower vacuume levels. Isn't this one, that I have from the factory? Plastic ball under the charcoal canister, front drivers side corner, with I believe just a single vacuume line going to it.

I wouldn't use a brass sensor. It'll be heat soak all over again. Use the plastic one

Alright so I'm trying to get into the actual VE tuning, and I want to make sure I'm doing my calculations correctly before I go starting to make a bunch of changes... Does the below look right? I've seen some where you use just the BLMs and some where you also multiply by the INTs, which should I be doing, or if different at different times, when?

I did find when I hover over the field while editing the BIN in TP, it gives instructions that say to use both, so that is what I started with...




I also noticed that the engine seems to be running really rich, like 11-12 while idling in open loop, then as soon as it goes into closed loop, it starts fluctuation right around 14.7. I just want to make sure this is the right table, open loop % change vs temp, to be adjusting to bring my open loop at least a bit closer to stoich? I calculated my open loop AFR to be about 8% richer than I want it to be, so I multiplied the table by 0.92, is that right, or because the table specifically refers to %'s, do I actually need to change the table value by 8? Also, the percentage is a percent decreased, since you want to richen your open loop in cold environments, so to make it lese rich, would I actually decrease the value, that is what I did so far.



I've attached the full Excel based log as well in case that helps you all help me! Or anyone else for that matter.

Agreed with ultm8z, don’t touch the ve table until you relocate the iat sensor, definitely use the plastic one, not sure if you switched but definitely use the s_aujp bin to start, also I can’t remember if the aujp bin has the correction for the relocation of the intake air temp sensor but just make sure you use the correct values then just lock it in open loop and adjust the ve table to match commanded afr. One other thing to remember is that your cam (111lobe sep) my not like to idle well at stoich so you may have to run open loop for idle.

Factory AUJP assumes the sensor is in the plenum, so the CTS/MAT blending table is active. I believe S_AUJP is the same.

In my Miniram start bin, I disabled the CTS/MAT blend table since Minirams never have the MAT sensor in the plenum. I guess the Stealth Ram can.

If raptere is still using the factory AUJP or the S_AUJP, then his MAT location in the plenum is still consistent with the bin. Once the MAT sensor moves out of the plenum, then as I was mentioning earlier... either disable the blend table, or can use the blend table from say, a early 90's LT1 Corvette or Camaro/Firebird (since they had the sensor in the air tube, but their blend tables set where the CTS had much less of a pronounced effect).

On the open loop...

I created a tool that will calculate the commanded AFR. There's a particular formula that's used and it uses two tables (Open Loop % Change vs Coolant and Open Loop % Change vs MAP)

Though keep in mind, this commanded AFR won't be in effect until about a minute and a half after startup, after the startup enrichment AFR decays out.

Sometimes on modified engines with different injectors, you can find that the WB O2 actual AFR is richer or leaner than the commanded AFR. In those cases, just adjust the Open Loop tables until your WB O2 actual AFR is where you want it.

These are the parts I have or have coming. Maybe I rushed to order the one with the brass body, but I think I'll be ok. Even if I use the brass body sensor, the tip is still the open type, plus mounting it is the intake Y manifold, keeps it pretty far from the engine, so heat soak should not be as significant of an issue.





I think I will want to use the LT1 table for the MAT CTS blending since as I understand it, part of the job of the table is also the effect of the warm intake runners and hot head ports on the intake charge temp once it makes it to the combustion chamber.

Would someone be able to share the right LT1 table values with me, I'm having a hard time finding them...

See below. Here's a compilation I put together when I was diving into the MAT Tables for my setup.

It's interesting that the Vettes assumed much higher heatsoak at lower airflows, even though the F and Y body alumium intake manifolds were the same. I believe the IAT sensors were in the air duct on both F and Y bodies too.

So maybe somehow the IAT heat soaked in the Y body air tube more than in the F body, due to underhood temperatures? Though at higher airflows, the Y bodies evidently heat soaked less? Who knows... What's good is that you can see what GM did and use that as a basis of comparison. I got a TON of benefit out of doing that with things like the AE and other fueling subroutines. We're EXTREMELYfortunate that the early speed-density batch fire LT1's carried over so much of the same calibration elements as 8D.

But on the INV MAT table....all I know is, I have a cold air tube that routes to where the battery used to be (I relocated the battery to the trunk). The air filter is now located under the car in front of the passenger side front wheel (completely outside the engine compartment). So I disabled the INV MAT table completely and then retuned the fueling tables around that. I figure with a non-metallic air tube, and since heat transfer into air only occurs at the boundary layer, that even at idle speeds, there's likely very little heating going on with the air before it gets into the cylinders. But I get a consistency in performance that was never able to achieve trying to dial in that INV MAT table.

My interpretation of the difference between the Y and F bodies, is the fact that I'm pretty sure the Y bodies have aluminum heads and the F bodies have cast iron. I believe the table purpose of the table is not only to consider the heat put into the charge air from the intake, but also through the intake runner in the head, estimating the temp of the intake charge as it enters the combustion chamber. Because aluminum is more conductive than cast iron, but does not retain heat as well, I suspect at low air flow rates, more heat is transferred into the air from the aluminum heads than the iron ones, but as the flow increases, the intake air begins cooling the intake runner of the head making the aluminum one impart much less heat into the air at high flow rates.

I found another set of values from Glenn91 That were even more aggressive than the corvette ones, but his setup was very similar to mine, so I took an average of his and the standard corvette values for now, and that is what I am going to try first.

Possibly...

But heat transfer is a function of time... I can't imagine (even at low airflows) that the air is in the intake port long enough to significantly heat it up. And combine that with how heat transfer from the metal only occurs at the boundary layer with the metal (which is a very thin layer of air), which means just a fraction of the total air going through the port would actually be picking up heat.

But this is all academic... main thing is whether the engine is happy when all is said and done!

so, I've got all my details transfered over to the S_AUJP bin, and have the other two files loaded and working.

I got the IAT wired, but couldn't find a 3/8" tap locally so I'll have to wait for one from Amazon tomorrow.

now I'm trying to wire the white 0-5 V wire from my WB to my ecu. I recieved the connectors from ebay. You say I need to connect it to one of the ecu connectors in position F14. I see numbers on each connector, and letters, bit I'm not seeing an F. Can ypu give me any hints on how to identify the right position on the right connector?



You say the ground also needs to be excellent, it's one of the three twisted, crimped, and shrink wrapped wires in this connector. Bolted to one of the factory under dash grounding locations on the driver's side. Good enough?

This looks like exactly what i need, but there is not enough resolution to read it... Any chance you have another version?

The letter F is embossed on the connector body. The numbers are on the retainer clip.

Found it! It was actually also posted by you.

Third in from the bottom right with the clip at 12 o'clock. (EDIT: Looking at the end of the connector, not the back as plugged in...)

Hopefully I'll be data logging my WB by this time tomorrow... Thanks!