Pro Stock John

iTrader: (34)

I have been doing a lot of research into LS1 Edit. Thanks to Dave and Ken from www.carputing.com for answering my many questions.

I have a question for the board about fuel.

Here are two schools of thought regarding fuel... Which one is makes the most amount of sense?

[Some] say to modify the MAF calibration table. Simple enough - lower the g/sec of airflow, you lower the fueling. Case closed. It's
like a very fine MAF translator, if you will... One that covers every single part of the motor's curve, not one that has only a point or two of +% or -% fuel. Steve Cole at TTS uses this method, and the code hackers say it's the correct method.

The other school of thought is the VE Table tuners. VE, however, is a MAP based function, and is seemingly MAF independent. However, these are the experimenters who are doing this. It *works* on LT1 cars. The code hackers say that VE changes
will not result in any operational changes, but the experimenters are (mostly) showing otherwise. Will the LS1 work the same? Honestly, I do not know. BTW, Ed Wright takes this approach.

Thanks to the guy who who took the time to write the above and send it to me.

I am pretty much planning to get LS1 Edit when it's available.

Thoughts? <img src="gr_stretch.gif" border="0">

Pro Stock John

iTrader: (34)

I believe that FAST/SpeedPro & DFI 7.0 folks have to use the #2 scenario since they are speed density and lack a MAF.

ChrisB

O boy.

Get on the LT1 Edit mailing list, the above currently = world war 3 on there right now. I'm not touching it with a 10 foot pole.


Chris

Pro Stock John

iTrader: (34)

I also was told by one of the folks I talked to that I should get my Ltrims to about 0 before I started to really play with the fuel map.

So if that is the case, which I would like validated, then how would you go about doing that? Change injector pulsewidth?

Camaroholic

iTrader: (1)

LMAO @ ChrisB. <img src="gr_grin.gif" border="0"> I told ya, PSJ, that there is a bit of debate on the topic. <img src="gr_images/icons/wink.gif" border="0">

I tried my first fuel change today. Remember, that my complaint was popping at cold idle. I lowered the open loop VE table values by 10% (grab all the cells from 400 to 2000 RPM, multiply by 90%). No popping. <img src="gr_stretch.gif" border="0"> I also lowered the bottom MAF scalings by a multiple of 90% as well (up to 10 g/sec - that's about where the car should idle). No popping.

AutoTap is so **** poor for this stuff... I hate it. I can't wait until TTS introduces Datamaster for OBDII. If you've never used it, you seriously don't know what you're missing. <img src="gr_grin.gif" border="0"> It should be out this spring.

My strategy on the fueling will be to leave the VE tables to the cold idle / open loop functions, and scale the MAF table when going for closed loop fueling. I figure as long as the LTrims are within the +/- 10%, the PCM is compensating OK during partial throttle, no real big need to adjust.

I still need to get used to this OBDII stuff, I wish I had LTrims based on 128. <img src="gr_images/icons/wink.gif" border="0">

-Andrew

ChrisB

If the L-trim schema carries through from OBDI -> OBDII then I would shoot for slightly under 0% on your l-trims - say -4 to -5 percent.

Datamaster for OBDII? Including LS1's, etc? AWESOME. I concur with Andrew, it is by far the best logging software out there today for OBDI LTx engines.

I run my car in open loop so I can just change the open loop AFR tables and not have to worry about the debate <img src="gr_stretch.gif" border="0">


Chris

John B

iTrader: (10)

PSJ, very good question! I don't have a clue what the hell VE is but I'd be happy to offer an opinion on this subject anyway!

People like Nineball (as if he actually has any credibility....j/k Tony!) are always saying that the stock PCM fuel maps and timing tables are very good as delivered from GM. I would agree with this based on the number of people that have killer power levels without PCM programming.

My thought here is that since GM has openly advertised the fact that they revised the '01 F-body PCM's with both a performance and emissions calibration it would be awesome to do a detailed analysis to compare exactly where did the changes take place. For all of the money that GM Powertrain has spent programming these things I would rather start from where they left off rather than re-invent the wheel.

It would also be a killer data point to analyze the '02 LS6 PCM data.

Just my .02 <img src="gr_images/icons/wink.gif" border="0">

Pro Stock John

iTrader: (34)

VE = Volumetric Efficiency (Tables)

The thing is, I now have 61 lbs of fuel pressure at idle. Car is running very rich. I am running Bosch 40 lb injectors and a Walbro/ARE 255 lph intank. I'd like to know what is the correct sequence for dialing in the fuel.

My first question is this: L trims... I'll assume anything +/-5% is okay... What am I looking at partthrottle for those I am assuming. So what would I do to make it right, change the injector pulsewidth?

Having done that, let's say I throw the car on the dyno. Let's say the AF is 12:1 from 5700 rpms to 6500. Let's say I want 13.1 or in that ballpark. What is the PROPER way to lean out the fuel!

I'll add a PCM Tuning forum if I see some good responses. Single User LS1 Edit is coming out very soon. Let's learn how to do this right.

66ImpalaLT1

I've been a long-time follower and former owner of LT1 Edit and done a lot of pcm tweaking on my own. I even did a little disassembly and work on my 93 LT1 pcm in my '66.

I used the #2 tuning method on my LT1, but I'll probably try both on my LS1.

I plan to be one of the first LS1 Edit customers. <img src="gr_grin.gif" border="0">

[ January 24, 2002: Message edited by: 66ImpalaLT1 ]</p>

Camaroholic

iTrader: (1)

OK, now to PSJ's question (just for giggles <img src="gr_stretch.gif" border="0"> ).

40# injectors, 60 PSI fuel pressure.

What I would do, is to start by asking - is that a 40# injector rated at 43.5 PSI? That means that at 60 PSI, its rating goes up by approx sqrt(60/43.5) 46.98#/hr.

Of course, in LS1Edit, now we have a learning curve. I see an injector size table based on intake manifold vacuum in KPA. Stock, these range from 3.62 g/sec at 5 kPa, to 3.96 g/sec at 85 kPa. Huh.

OK, taking the stock 28 #/hr rating of a '98 LS1, I get 3.53 g/sec rating.

Taking a 46.98 #/hr rating, I get 5.92 g/sec. So, what I would try and do would be to 'fit' this new base rating with the curve given. Going from something like 6 g/sec up to 6.35 g/sec in a somewhat linearized fashion.

That would get your injector sized properly. Note that you may have to tweak your injector offset.. and damn, that's one helluva table! I have no idea where to start with that one. <img src="gr_images/icons/wink.gif" border="0">

From there, then you start tackling your block learns. I would do this for partial throttle by adjusting MAF values.

For WOT tuning (AFR with a wideband), I'd use the PE vs. RPM table. It's pretty darn plain in a stock LS1, though. But it's the fuel multiplier used during Power Enrichment mode.

My ramblings probably don't make sense, but they're a point to discuss...

-Andrew

Ryan 98SSA4

Well where is that fourum?? I'll be there. <img src="graemlins/fluffy.gif" border="0" alt="[Fluffy]" />

The car is gonna be doing lots of this ... all year! New tires, and other toys on the way.

Ryan <img src="graemlins/burnout.gif" border="0" alt="[Burnout]" />

JJH98SS

iTrader: (2)

PSJ-
Most of the Sc'd & turbo'd Pro-5.0 and Outlaw guys use the VE method; The math isn't hard (just real long) to get a base table. It's actually easy to get in range- the turbos all have relatively predicatble flow rates, and the intercoolers have predictables pressure drops. Anyway- on to your setup...

Where are you looking to tune it at? Do you plan on running a MAFT with the LS1edit? If Edit turns out like the DFI 7.0 or the FAST box, it'll do a base map for ya with a little work. MOTEC has an injector map application (VE based); I'll try to post a link.

Sorry for not having a direct answer- It'd be nice to have LS1EDIT in hand to help out (aka- Beta pitch).

Camaroholic

iTrader: (1)

The base map in LS1_Edit is your stock map, or whatever a tuner put in there (if you can read it). It does not have a function to generate a VE table, but perhaps we can talk some software wiz in to making something based on AutoTap or (preferably) TTS Datamaster logs. Joe Georger ( http://www.joegeorger.com ) wrote VEMaster for OBDI LT1 cars, and it seems to work quite well.

I think that on my car, I won't really need all that much closed loop tweaking - the computer should be able to handle that for me (it has, as I've noticed). However, open loop (cold) is where it needs the VE table work, and I reduced the VE even more last night at lower RPMs, and it's running even better when stone cold. I've reduced the 400-1200 to 81% of original, and I've reduced from 1200-2000 to 90% of original.

Now, in PSJ's position, since he's changed his injectors, pressure, and, well, motor <img src="gr_grin.gif" border="0"> , he's basically starting from scratch. The steps I describe above could be used, or just take the difference (47/28 = 1.679) and multiply the values in the injector size table by this. Change your cylinder size to reflect the larger motor, and see what happens with the LTrims. You may have to start tweaking the injector offsets because of the Bosch units - they'll have different performance characteristics than the stock units... but again, I am not familiar with the parameters of that table, so I can't give a direction to go.

The stock tables are pretty good to use as a baseline, IMHO. They do require tweaking when you start changing internals around, tho...

-Andrew

JimmyKash

[quote]Originally posted by Pro Stock John:
<strong>
Here are two schools of thought regarding fuel... Which one is makes the most amount of sense?

</strong><hr></blockquote>

i'm sorry...i JUST couldn't help myself here. <img src="gr_stretch.gif" border="0">

ANYWHO...

i've never played with an LT1_Edit, but i've played with a few DFI's and some FAST systems and using a VE table is pretty and straightfoward in my opinion but i have no comparison. So it would be hard for me to comment on it.

But to me, using a VE table system would be the way for me to change things

Magnus

iTrader: (4)

[quote]Originally posted by Pro Stock John:
<strong>I also was told by one of the folks I talked to that I should get my Ltrims to about 0 before I started to really play with the fuel map.</strong><hr></blockquote>

When people tell you that, ask why? When I started to tune, people told me to shoot for 0% LT's, but every time I asked why I never got a reason. The biggest thing I heard was, 0% LT's is where the PCM has to do the least work (lowest correction factor), but the PCM isn't some calculator processor, it's fast enough to make the calculations instantly.

If you shoot for 0% LT's, thats just saying that your MAF is calibrated correctly and your VE is stock. When you add things like heads and different MAF's etc. etc., VE and calibration change. Bringing LT's back down to 0% wouldn't be accurate.

If you tune the PCM to your new setup, your LT's should (in theory) come back closer to 0%. If you tune for the new MAF calibration and the new VE of the motor, then the PCM wouldn't have to make much correction.

But lets say you want to bring LT's to 0% before tuning. How would you do that? MAFT? Then your using 2 methods that affect the way the PCM calculates pulse widths, not very good IMHO. What about changing the MAF. This is a better idea. You could change the MAF setup so the calibrations are more similar to stock. But that still doesn't take into effect the new VE of the motor. You have things like inktake/heads/headers that really effect the way your motor uses air/fuel. It won't act like its stock anymore.

Anyway, I just started learning this stuff so I could be way off base. I say you pull off the MAFT and any other influencing devices you may have (Aftermarket MAF) before you begin to use LS1 edit. Then use LS1 Edit to program the pcm to the new VE of your engine. <img src="gr_stretch.gif" border="0">

- Keith

Pro Stock John

iTrader: (34)

Magnus: I am learning as I go too. I think the point that Ken from www.carputing.com (Makers of LT1 and LS1 Edit) was making is that you need to get the LTrims w/n a factory range. And work off of that. I had heard something like three years ago that +/- 7% Ltrims were considered okay by GM. I would think that was the case too. Ken did say something about if the Ltrims were too high it screws up something else. I can't remember. I think he said if the Ltrims were too much out of range the PCM will have to relearn something everytime you drive the car. Perhaps the Strims and fuel cells get messed up. Please keep in mind we are talking about pcm tuning. If I am tuning the pcm I won't tolerate 20% Ltrims because I can address it. FWIW, I think I would have to log my Ltrims for a bit, with the MAF T off the car, and then change the tuning. Might take a while to get it right. I'm not though how you get the Ltrims good and still for example target a 13:1 AF ratio on the dyno, what if the pcm tuning won't allow both.
----
JJH98SS, those DFI and FAST guys have to do the VE way. They are running speed density ie NO MAF anymore. They don't have a choice. I have a 96Z28 buddy running FAST and it seems very good, it comes with a wideband, I am not spending $3,000 to get that setup. DFI 7.0 is coming out and it will be around $3,000 too.
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C'holic I already have custom tuning. But my shiftpoints are way too low, especially on 1-2, that's why the car has not run big mph. I made peak HP at 6200. My 1-2 shift was at like 5800. I need to shift my shifts at 6500 maybe even a wee bit higher to run 124-127mph. My best so far is 120.99mph hitting the rev limiter on 1-2 and 2-3.
----
Well, some more comments from a contact of mine, who has some knowledge of how the GM PCM stuff works. I talk to this guy once in a great while, he's very busy... Here is what he said...

First off, the LS1 operates completely differently than the LT1 did.

Second, LT1 had no spark advance connection to the MAF.

Now, i'm assuming the places people want to tweak A/F are at WOT. LS1 Edit
provides a power enrichment cal for just this. how rich and when you want
to be that rich. That simple.

There should be no need to mess w/ anything else.

get the proper injector flow rate in there, there's a table for that.

Get the advance in there, table for that.

set your WOT enrichment, table for that.

and leave the rest alone. closed loop at normal operation is just fine w/
the right injector flow rate.

I've changed: injector flow rate, high octane open throttle spark curve,
and power enrichment A/F. That's it. that's all you need.

FWIW, the injectors you have are rated for 37ish lb/min at 3.5 BAR not 3 BAR.

[ January 25, 2002: Message edited by: Pro Stock John ]</p>

66ImpalaLT1

John, that person doesnt address Open loop (cold idle, and while warming up) issues. I think thats pretty important to improving the drivability of the car.

Eric

boos2

FWIW I say start that forum for LS1edit. I'm just getting into this and I think that would be a good central location to compile everything. Thanks for all the info everyone. I'm learning a lot.

66ImpalaLT1

Chris, I think spark is mapped by RPM and a Calculated Load Value on the LS1, not strictly a kpa from the map sensor.

Other than that I agree with everything you said.

Eric

JimmyKash

Problem with LS1's is the coil packs. Hard to figure out the ignition problem with using those DFI's or FAST systems.

Also, FAST isn't $3000 unless you've been bent over and had it stuck it REALLY good.

The only thing that is $3000 is IF you get the sequential version.

if you use the bank-to-bank (which seems just as good and makes just about the same power) it can be easily had WITH WIDEBAND for $2000.

Problem with the LS1s is figuring out how to get all those coils to work with the new computer, that is why Holley's system has their own coils to match their own computer.

Hey john...whatever happened to charlie's FAST system and his harness?