I have been spending a great deal of time searching and reading on this site. This is by far the most comprehensive database on the net for DIY EFI. Despite finding the answers to most of my questions, I have a few that I am seeking some guidance with. Sorry for the length, but these questions seem to be related.

Background:
I swapped the TPI system from my 91’ GTA (5.7 – 245 hp) to my 94’ Suburban (5.7 – 210 hp). Both engines are stock for its application. To put the TPI into my Suburban, I bought a #727 computer, harness and “custom” chip from Street & Performance. You can see the swap here http://www.edgesz28.com/edgesz28/sub...urban-home.htm The S&P harness includes three jumpers to connect back to the original TBI computer, which is retained to operate the 4L60E, anti-lock brakes, AC, etc.

I invested in Craig Moates’ BURN1, ALDU1, HDR1 and GP1 pieces. I downloaded and started using TunerPro RT and DataMaster 8D. Therefore, I have read the S&P “custom” chip and learned that it is nothing more than a tweaked AUJP bin. They added some spark and fuel in the upper RPM and load levels. The stock GTA had an ANJF bin, which appears to be very similar to the AUJP bin.

Other than the difference in the stock engines, the TPI system is stock, except I installed new 24# SVO injectors, set to 40 psi with zero vacuum. The TPI ran perfectly on the stock GTA setup. The S&P chip runs fairly well, but the idle is pretty rough and the cruise and part-throttle areas feel sluggish. Originally I checked the BLM readings with my Auto-X-Ray. Using this information, I was running about 124 BLM at idle and 118 pretty much anywhere below 3000 RPM cruising and part-throttle. So I adjusted the VE tables to about 90% of their original values, from 4000 RPM down and 70 KPa down. I also adjusted the injector constant to reflect 24# injectors in lieu of the original 22# setting. Base timing is set at 6* in the constant and distributor (EST disconnected).

Question Re: BLM
Since I made the first round of VE changes, it runs a little better and I had time to log the drive home yesterday using DataMaster 8D. It is still running about 118 BLM in the same ranges described earlier. But when viewing the datalog, I noticed that when “cruising”, I frequently hit the 80-90 KPa MAP range. So clearly I need to adjust those areas as well. Please review my current VE table and the histogram below. My next step is to reduce the red areas by 8% (118/128 = .92). Is it reasonable to continue to decrease the VE table until the BLM histogram is equalized?





Question Re: VSS
I have read that it is required and not required, and seems to be a topic of debate. Currently my #727 ECM does not receive a VSS signal, for it is still plugged into the TBI PCM. Without VSS, I believe that this is affecting my Decel Enleanment(?). I noticed when coming to a stop, especially abrupt, the engine wants to die, but mostly catches itself. When this happens, the datalog shows a BLM of 114 and the BPW is still present, despite the lack of TPS voltage. Shouldn’t the lack of TPS voltage cut off fuel completely (i.e. 0.00 PW)? Is the lack of VSS signal causing this problem when stopping? Can I tap into the truck’s original signal wire and set the $8D code to meet the truck’s VSS setting (I think 2000 ppm)?

Question Re: Hot Idle
The idle in drive is about 124-126 BLM and is at 40 KPa and 600 RPM. This is fairly decent. But in park, it drops to 122-124 and is has a lope to it. Other than VE and timing, what can I adjust here? The IAC park position is set at 160 steps. Will moving this one way or the other help? I believe that the IAC setting itself is not an issue.

S&P is going to make me another “custom” chip based on my description of BLMs (for free) and E-mail it to me so I can burn it myself. I learned (from this site) that “custom” is in reality a joke. It takes scores of changes to dial it in. But my application is stock, right? Not really, the TBI engine is different than the GTA’s engine, and the Suburban weighs a whole lot more than an F-body. I tried the stock ANJF bin and it ran absolutely horrible! Really low BLM levels, like 116-118.

I have not messed with the timing yet. I noticed that 4*-6* comes out (knock retard) almost whenever I give it gas and at any RPM and load level. I uploaded the TBI spark table (BJLH) to TunerPro RT, and will compare it to the S&P chip (aka AUJP). I’ll bet despite the TPI system, the spark table will end up more like the TBI system. This is just a guess, but only time and testing will tell.

Any input on my questions would be greatly appreciated. I believe I am on the right track, but some guidance is needed. Thank you, Ed www.edgesz28.com

 

Feed the VSS to the 727, you'll have to play with the VSS constants to get the MPH to read right.

Forget about S&P.

I can't think of a reason why you'd see 80-90 K/Pa during cruise. Other then something being plumbed wrong, ie some solenoid opening to atmosphere, ocassionally.

 

"Custom" chip. Problems? Whoda thunk it. Aren't you glad you decided to DIY. I would be more interested in the timing and AE tables rather than the fuel tables. The 1200 to 1400 lbs. (at least) of extra weight and small rear end/tranny gearing in the suburban will require a lot less spark and more AE down low to get the beast moving and keep detonation down. A lot more than a GTA, hence the tip in knock and high MAP values you are seeing. What are your knock counts like? Grumpy's minimal timing gospel applies doubly to heavy trucks. Hook up the VSS, It'll help. HTH

 

IIRC, the stock 94 truck torque peak is 2800 rpm. The L98 is 3200ish. The Vortecs are listed as 3200 also.
My 93 truck shifted at 5000 or 5200. Can't remember.
But your 5600 entries will have little if any affect.

0% tps all by itself will not cause DFCO.
The code checks for several different things and then puts a zero in the pw ram location for anyone of them.
VATS is an example.

I'd compare a truck bin ve to give you an idea, and start with the truck spark curve or less. Your just going to have to tune the part throttle like everyone else.

Do a search on the $od? mask if you missed it.
Just a week or so ago it came up.

edit: Since your a newb...
$OD
Make sure and come back and tell us your results.

 

Thank you all for responding. You’re killing me on all the acronyms (lol). But I am learning, and part of learning is doing research. Thirdgen.org has more than enough to keep me busy. I learn something new each time I do a search.

Grumpy – You are right about S&P. They are some nice folks, but the custom chip part is a bit overstated. Since researching and starting the DIY stuff, I learned that the TPS on a SD resets itself to .54. Try telling that to S&P. They say, “Bump up the TPS to .58-.60, that will richen up the mix”. But why did the TPS come from the factory without slots and why does it always reset to .54? Maybe because it is not adjustable on SD.

I will hook up the VSS tomorrow, probably just tap into it since I need to the original plug hooked up for speedo and 4L60E.

After reading the Holley Commander 950 book, I see that 80-90 KPa is more like “passing” and not “cruising”. I believe my original statement was wrong. I am not really hitting 80-90 KPa when cruising, more like a moderate pass on the interstate.

HaulnA$$ - My knock counts were like 5*-10* using the AUJP table. I have since copied the original TBI table (thanks Z69). Counts are down to less than 5*, some still hit 8*. I will adjust from there. Am I glad I decided on DIY, absolutely! But the learning curve is rough. But I am determined to get it, no matter how long it takes.

Z69 – This is first I have heard of $OD mask. I never thought to look it up since it is TBI. Thanks for the link. I read it, and subsequently found the $0D ECU file at Moates.net. I had already read my truck’s MEMCAL (BJLH), but did not have an ECU file to properly read the table using TunerPro RT. I am now using the TBI spark table, but it still needs to be reduced in places. But the VE table is much higher in the original TBI bin, compared to the AUJP bin. I am going to keep reducing the current AUJP table. Each time seems to raise BLM for the most part.

Now that I have the $OD ECU file, I can adjust my 4L60E shift points and erase the codes that now set off the check engine light since the distributor, etc. is no longer connected.

I think I will also reinstall the original 22# injectors tomorrow. It ran better with those, even when using the original S&P chip. Maybe my stock TBI engine does not warrant 24# injectors, despite adjusting the constant and pressure accordingly (40 psi). Could it not be compared to putting an 850 cfm carb on a stock, two barrel 350?

One more question - My TBI spark table has the advance set at like 28* in the idle range. Why would it revert back to say 14* when idling and at operating temperature? This is when the idle gets rough, even though the BLM range from 126-128 when idling. The base timing is set right and I am sure the balancer is accurate.

Your help is appreciated, thank you for your patience. I learn something new everyday. But there are a lot of table and constants to look at. At this point, I think I know maybe what 10% of them are for and what changes affect. It’s funny, my wife and friends think I am some sort of genius because I can program a chip (lol). I’ll save that title for you guys who are manipulating code and writing programs for knuckleheads like me to simply revise a cell in a table and hit the save button. Any more ideas would are welcome, especially on my last timing question. Thanks, Ed.

 

Just a helping hand, There is a program on the Moates website called "VEMaster".
It will help you "dial in" the VE tables under 3000 rpm much faster than manually (at least for me it helped alot)
Make datalogs of "cruising" and stay out of PE/AE modes and big hills to keep the data from being skewed. I try to get a range of flat and small hills to cover the full rpm and MAP ranges.
After logging run the "VEMaster".
It takes the datamaster log file and your current bin file and makes the BLM corrections based on your settings and results.
Make a copy of your bin before running it!
It only works for the $8D mask bins and Datamaster logs.
Keep making folders on your hard drive for each change so if you get too aggressive, you can go back to a previous bin.
You may also want to adjust the IAC to be sure it is correct (see tech articles on the main page) Could help your idle.
The TPS is actually adjustable by loosening the two retaining "torq" screws and just look at the log while turning it.
Jp

Ps, did you mean TPI instead of TBI? (typos?)

 

Thanks for the tips.

When I said TBI, I was specifically speaking of the original Suburban spark table. Using the AUJP spark table with this heavy vechicle, the knock counts were like 5*-10* at basically all RPM/MAP ranges, other than idle. I read the TBI bin, copied the spark map to Excel, and than back to the the AUJP bin, making sure that the RPM and load columns/rows matched. For the most part, the original TBI spark table for this Suburban matched the AUJP minsu spark knock. That is, the difference between the two spark tables was generally 5* less than the AUJP bin. This is what Z69 thought might work. It is definitely better, but it still needs some more spark taken out in some of the part-throttle ranges under 3000 RPM.

Again, thanks for the VEMaster tip, Ed

 

OK, I see
It is obviously much more difficult to get both spark and fuel tables dialed in at the same time. Each one will cause the other to need a tweak.
getting the spark to best points then working on fuel helped me out. then I went back to the spark to gain a little more where I could.
Took about 4-5 times on both tables but in the end it was running pretty good.
Good luck!
I'm still reassembling and then waiting for the spring thaw.
Jp

 

I changed the injectors back to the stock 22# units and set the pressure to 43.5 psi without vaccum.

I burned a new chip that incorporated the original S&P VE table (tweaked AUJP), but retained the spark table from the original TBI bin.

I have not had time to run a DataMaster log, but just viewing my Auto-X-Ray, the BLMs are running between 128-132 when cruisng and part-throttle. The decel is around 124-126 (no TPS). Idle quickly jumps to 132-134.

This is pretty much where I started from, before I looked into DIY. With the idle BLM between 132-134, it still idles a little rough, but better than when the BLM is down around 122-124. S&P's solution to my high idle BLMs was to send me 24# injectors, giving me a credit for the originals that they had already cleaned. You don't have to say it again, I know "Forget about S&P". If I'd only new then what I know now.

Everything being equal, why would installing 24# SVO injectors (set at 40 psi) and changing the injector constant from 22 to 24; would my BLMs be so low throughout the entire range? Even reducing the original VE table by 80% had no effect. Is it possible that I simply proved that bigger is not always better?

Well, now I am close and can work on my VE table to bring the idle BLM closer to 128. I will also definitely try the VEMaster and tune the entire range.

I spliced the VSS wires from the #727 computer into the original two wires plugged into the VSS that lead to the truck's PCM. I no longer throw a code, but the MPH reads zero on my Auto-X-Ray. Grumpy, you said I will need to adjust this, but even if it is off, shouldn't I at least get some reading other than zero? Maybe I need to tap into a different wire, maybe one coming off the truck's PCM. Any suggestions. Thanks, Ed.

 

But there not. Even slight changes in design effect the opening and closing rates of the injectors. And few (none) injectors are dompletely linear, at the smaller PWs. As close as EFI is, there's still some minor differences, and errors that have to be accounted for. Even in the code numbers are rounded off.