2 Bar Stock PCM Speed Density Tune for >6psi (Forced Induction) - CamaroZ28.Com Message Board

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2 Bar Stock PCM Speed Density Tune for >6psi (Forced Induction)

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Old 12-02-2007, 05:02 AM
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2 Bar Stock PCM Speed Density Tune for >6psi (Forced Induction)

Download working 2Bar files here: 01-30-2009, 10:46 PM Post #238. http://www.mediafire.com/file/zo3zwg...6_OpenLoop.lt1

10-18-08: IT WORKS! (all summer) 2 BAR ON STOCK LT1 PCM - Everything you need is in this original post. Specific questions/answers are in the following posts (there's alot of them).

3-11-08: MAJOR UPDATE/SOLUTION IF YOU RUN 2 BAR MAP on STOCK PCM YOU NEED TO DISABLE BARO RESET ON YOUR TUNE OR YOU COULD POTENTIALLY BLOW UP YOUR MOTOR BY ENTERING WOT AT THE "WRONG" TIME. New TUNERCAT definition file avail. Not sure about update for LT1_Edit.

I discovered the BARO resets (matches MAP PRESSURE) all the way up to 3600rpms under WOT (or more than 37%TPS). This is OK if you run WOT starting under 3600rpms everytime BUT if you start your car and lightly rev to say 4000rpm you could then enter WOT and the BARO will stay at the KEY ON MAP value (usually 52kpa on a 2bar setup). This makes fueling VERY LEAN running WOT at 52kpa BARO compared to WOT at 65kpa BARO. THis also means once you lower the BARO RESET to something like 1000rpms or lower your WOT fueling will now be based off of ~52KPA everytime (consistency) and you will need to increase fueling accordingly (I see about ~10%more VE needed to come even close - I lowered my injector flow rating to lower the amounts of VE needed for the same AFR since VE are limited to 99%).

3-13-08 Minor Update - Fixed a prob with my 83lb injectors having slightly rich idle + rich decel (just above the limit of Decel Fuel Cut Off)...Plus there was this surge upon injector re-light since injectors were over fueling.. I compensated with reduced timing upon re-lite but now the problem is gone... the right way. Tunercat shows stock min PW set at 1.4ms, slight decel and idle mine was 1-1.3... changed to 1.0 and all fixed... hold 14.7 on decel and 14.7 on idle. Amazing control for stock PCM I think.


Information is below... My setup is in the signature...


Original Thread “Speed Density tune, easy?” started by VK, with a lot of input from engineermike and STSturboLT1 located here: https://www.camaroz28.com/forums/sho...d.php?t=500809

Brings me to my point… (bolded points below are the main points I picked up on by reading everybodys posts about SD tuning…

I have a 7 psi forged 383 getting ready to run 15psi on the stock PCM with 83lb injectors and my question is:
1) Whats the SAFEST way to get there other an running a FMU or PE mode (which after the MAP maxes out at 2000rpm and the MAF maxes out at 4500RPM I’m left with only RPM/PE enrichment/100kpa timing…

Main Points by author:
1) “VK”: I usually get my base tune done by Madz28, but if at all possible i'd like to do this myself. I'm completely maxing out my MAF by 5K rpm (471g) so i need to switch to speed density or get a new maf. Sounds like Speed Density mode is a given if you run over ~5-6psi boost.

2) Sweetred95ta: From what I understand, it's not that easy to switch to a 2-bar MAP. I honestly haven't heard of anyone that has successfully done it. Tuning in SD is pretty easy. Instead of making fuel corrections in your MAF calibration tables, you'll make them in the VE tables. Add to the numbers and it'll feed it more fuel; lower the number and it'll take fuel away. Just log the car and find out where it's wanting to run lean or rich, then make the appropriate changes. “Add to the VE tables to add fuel, subtract from the VE tables to take away fuel” This is better than the single lined PE % line…

3) Engineermike: Alvin at PCMForLess did a '93 one time, but said it was a real pain and doesn't recommend anyone else try it. I'm going to give it a try eventually and if it doesn't work, switch to MS2 for fuel-only.

Sounds like it is possible but is a lot of work…?? A lot more work trying to get something else to work is what I understand…

4) LSxManiac: First of all, you can't use a 2-bar map sensor without A LOT of calculations because the PCM is designed to operate with a 1-bar sensor. Second point, depending on the amount of air the engine is using, you may not need to convert to speed density. If MAP goes to 100 kPa and the MAF is maxed out, you can just crank up the PE table values to add more fuel. At this point, the system is functionally in speed density mode because the MAF (being maxed out) is no longer supplying relevant information. This may not work at high boost pressures, or if you're marginal on injector size, but I've tuned a bunch of supercharged cars (including some 86-89 models) using this method.
a. This works fine with the lower boost guys (including me up until now when I think about boost beyond 6psi)

And finally… the reason for this post…
STSturboLT1” This is a pretty old thread, but I just thought I'd share that I recently got my car running a 1.5 bar tune in SD mode with the stock LT1 PCM. Here's what I did to modify the tune by dividing the VE tables, moved the columns accordingly. I realized that 100% is the limit for the VE cells, and when in boost the values needed could be higher than 100%. So I divided all VE cells and the injector constant by the factor of the MAP sensor (STSturboLT1 used a 1.5 bar setup to divide by 1.5) . I (STSTurboLT1) the same basic approach for the spark advance tables, except they were easier since there was no scaling involved, just moving columns around.

Once all the tables were adjusted, I started the car up. It fired up right away and ran ok…

I ((STSTurboLT1) went to a speed density tune because the car has better throttle response compared to using the MAF. Plus I'm sick of always having to clean the MAF, and the fact that it's just a restriction, albeit small, on the intake. I just thought some of you might be interested.

Problem = stock PCM never recognized boost, The new MAP sensor fools the PCM to recognize boost being within the 100 kPa limit. More trickery is needed by scaling the injector constant, to make the PCM add more fuel than it intends. I originally planned to tune WOT strictly with the VE table, and set the PE values to 0, but I worried hitting the 100% limit in the VE tables…. THIS IS WHERE I CONTINUED to realize a 2 BAR MAP on a Stock PCM WORKS (proper scaling results in a stock LT1 PCM Boost referenced Speed Density Closed Loop Tune)

Long story short…

My 7psi 383 (soon to be 15psi) using the stock LT1 PCM references boost (0psi = 51kpa, 7psi = 75kpa, 14psi = 100kpa) I did the following based on everybody’s previous experience

1) Since STSTurboLT1 is the first guy that I read that actually converted it to a 1.5 bar setup and transferred the tables to re-calibrate the PCM into 1.5bar mode… I did the same thing but using a 2 bar sensor and scaling everything by 2 (scaling the VE tables, timing, open loop AFR vs Load, etc by 2) then once it ran I took it one step further according to his statement about the “additional trickery by scaling the injector constants…”
a) divided my injector flow size by 2, (83lb original changed to 40lb)
b) Dividing all the VE% by 2
c) TO FIX LEAN TIP IN STUMBLE I lowered my injector flow rating a considerable amount after I divided by 2 - 83lb/2 = 41lb.. this still had lean tip in like the 1 Bar tune so I lowered it to 30lb and lean tip in DISAPEARED! (all other fueling needs to be leaned out obviously


This resulted in a base tune to run (actually would only idle leanly and stall once throttle was applied…) then I ran in closed loop and used VE Master to adjust the VE tables…

The result for me + others
1) Same (actually better) idle and cruise driveabilty – probably because I was in MAF mode prior to this Speed Density/2bar conversion and MAF just isn’t as good as Speed Density (assuming Speed Density is tuned properly)
2) Better startup – only because before all settings were what I thought “looked correct so I did not want to drift to far from the “correct settings” (now everything scaled by so I have no problem reducing/adding settings beyond what should be normal
3) Tuning AFR based on manifold pressure and RPM (not just RPM alone using PE vs RPM – I set that to 0 across the board and dialed in a consistent 11.8-12.2AFR @ WOT based off Wideband O2 readings) with 0% in the PE AFR vs RPM column… This results in infinite AFR adjustment regardless of what manifold pressure is… READ MAJOR UPDATE AT TOP OF THIS PAGE
4) Better overall timing resolution (with the 1 bar tune timing is locked to 100kpa across the board regardless of actual throttle/manifold pressure

Last edited by dookie454; 03-02-2009 at 07:22 PM. Reason: Added "10-18-08 Long Term Results"
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Old 12-07-2007, 08:28 AM
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I will be trying this on my setup as soon as we get some better weather around here, I think I can make it work!
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Old 12-10-2007, 12:04 AM
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Another person tried this with GREAT success (sounds like he also experienced better results with the 2 bar SD tune than with the 1 bar MAF tune)

Details here:
https://www.camaroz28.com/forums/sho...=500809&page=3
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Old 12-11-2007, 01:59 PM
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My story with a 1.5 bar SD tune is at the link you provided. Although the car ran ok with the MAF, I always battled surging and bogging under acceleration during normal driving, even after the fuel trims were dialed in. The throttle is more responsive in SD mode, making it more enjoyable to drive. I'm an engineer, so it was a fun side project. It was actually much simpler than I thought it would be to get it running correctly.
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Old 12-13-2007, 12:15 AM
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Originally Posted by dookie454 View Post
Another person tried this with GREAT success (sounds like he also experienced better results with the 2 bar SD tune than with the 1 bar MAF tune)
"GREAT" is an understatement. The only thing I'm upset about is the fact I didn't do this sooner. I was waiting for moates to develop the real-time tuning for the LT1 so it would be easier to tune, but it turns out it's pretty easy to tune by scanning and flashing. It only took me about 4 flashes to get it dang close.

All this and I'm tuning in Open Loop, so there is no O2 corrections that would mask an imperfect base map. I imagine once I get the base map close enough, I'll enable Closed Loop and it'll get even better. On the current tune, it's staying between 13 and 15 A/F at idle, accel, and cruise (all in vacuum - much richer in boost). I could probably put it in Closed Loop now and it would compensate, but I'd rather get it closer to perfect before doing that.

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Old 12-13-2007, 07:59 AM
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You should try putting in closed loop then run the Datamaster logs through VE Master... try try that 2-3 times see what it does. I left my VE cells slightly on the rich side to the PCM is pulling fuel slightly most of the time, rather than adding fuel.

If you have a problem with closed loop it's probably because the BLM/MAP boundries need to be adjusted... again VE Master makes it easy to see what cells are getting hits and how often. YOu want the most wide spread BLM cell hit to make the most of closed loop tune.

There's a site around somewhere from the guy who invented the Versafueler... so a search his site goes through everything in detail.
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Old 12-13-2007, 09:19 AM
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I think we should setup a test bed, get a small tank attach the 2 bar map and the 3 bar map along with a pressure fitting to either put a vac pump or a compressor. first test for the most vac a motor will develop 20-30 psi vac or so. attach each sensor to the car and using freescan note down which kpa cell the computer is in. then test for 10 psi vac, atm, and different levels of pos pressure etc etc etc. this way we have a very definitive way of scaling the tables can even make a nice excel sheet too
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Old 12-14-2007, 07:04 PM
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Smile

Well I just sent the tune to you, let me know when you get that testing done!
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Old 12-16-2007, 10:51 AM
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dookie would you mind shooting me a copy to compare to mine? [email protected] i've written and tested one of my own but the car just ate the accel opti so im just bench racing for a week or so...
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Old 12-16-2007, 03:14 PM
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should be in it's way. I got a MSD pro billet and ate that in 2 weeks... looks like they forgot to add locktite to one of the rotor screws.. got a replacement and took it apart and see they forgot locktite again so I locktite myself and so far no more problems.
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Old 12-16-2007, 09:37 PM
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I've been steadily driving and tuning this thing. It's getting better all the time. I probably could have called it good a few iterations ago and never looked back, but I guess I'm a perfectionist.

I've had to polish a bit on the 25-30 kpa at 1600 - 2600 ranges. It seems as though there's a lean spot at about 27 kpa in that range, you can't change the values there so I guess I'll have to live with it. That's the sacrifice I suppose with 2 bar on the stock ECM. BTW, the lean spot is about 16/1 and it's not even noticeable when driving. I wouldn't know it was there if it wasn't for the WBO2. Roll on the throttle to 30 kpa and it runs 14.5 and back off to 25 kpa and it's 14.5 there too.

I've also had to add a whole bunch of fuel in the 45 - 55 kpa and 600 - 2200 rpm range to cure the lean tip-in problem. It's almost totally gone now. You really have to snap the throttle open quick to see a spike on the A/F gauge.

I made a full throttle pull tonight and it was scary fast, but it always is in the cold. A/F started out around 12.5 and richened up to 10.5 by the top. I'm running Methanol injection, which skews the tune results. I plan to phase that out over time as I get the fuel map straight.

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Old 12-16-2007, 10:05 PM
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Nice to hear Mike, I can't wait to give this a try on my car!
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Old 12-16-2007, 10:25 PM
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I have a 6 speed and the 2 bar is smooth, the only "problem" if you call it that is because of the cam (cam surge) but it's very small and not due to AFR or the tune... I wouldnt be able to detect it with an automatic but with my aluminum flywheel and springless twin disk clutch it sometimes shows it's ugly face, sometimes when cruising at 30-40mph, or when idling along in 1st gear in a parking lot.

In the video below it didnt even show up while on the dyno... you can hear the responsiveness after the pulls I kinda blip it a little.
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Old 12-23-2007, 12:43 AM
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I am really interested in how this is working out for you guys. I have a couple of questions:
1. Would this also work on OBD2 cars?

2. Do you think it would be a good idea try this tune unboosted first in order to get the drivability sorted out and then add boost?

Thanks,
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Old 12-23-2007, 10:28 AM
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Where do you get a 2 bar map sensor? I think this is going to be my tuning option right here b/c I dont have the money for an aftermarket system right now.
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