LA3 strategy experts.

[nik97]

I could use a little light shed on my knowledge base for the LA3. I'm not going to get into specifics about my setup, just want to gain some info on the LA3.

If someone has a good link, please post it. Otherwise, if there are some guys on here who are well versed on the LA3's operating strategies, please chime in.

I basically want to know what inputs affect timing and fuel delivery. I assume most of the fuel calculations are made by inputs from VAM, O2S and TPS... But what about timing? How much of an impact does the ACT and ECT have? What are the capabilities of the LA3 to pull or add timing based on good or skewed signals from these inputs?

Any LA3 geniuses?

[AirBender]

act will pull timing the warmer the air gets, the ect will add fuel with cooler temps mostly for starting and warmup... without the ect it will default to i believe -40 degrees and dumps fuel.... the knock sensor pulls timing also..... it cannot be used with a solid lifter head for obvious reasons... if any of the major components goes bad it will go into limp mode,,,, it will run rich in limp mode but will get you around..thats some basic stuff you may already know... or not... if you could get on turboford.net john k and caroth, svojohn, and a couple others are well versed in the la series ecus... the smoothest factory ecu is the 8au....

[nik97]

Well, perhaps I should provide some more details to get us going on the right train of thought.

This is an '89 2.3 block(.030+) with forged flat tops. '86 ported D-port with a R-Roller and esslinger dual springs and new stock valves(3 angled seats)

Using a tubular manifold(common external gate style) modified with an STi VF-39 turbocharger with internal gate and 3" exhaust.

Fuel comes from a Walbro GSS 342 into 35# browns and uses an aeromotive adjustable 1:1 FPR @ 39lbs static.

I'm running a decently sized front mount and custom tubing. All other hardware is from an '87 Turbo Coupe including intake manifold, harness, sensors and ECU. Ignition is stock and new with NGK plugs. Boost is set at 20lbs and base timing is about 14 BTDC.

My 'problem'...: The truck runs well with the Subaru turbo(not sure if anyone has tried using a VF-39, but it suites the dynamics of the Lima well). 20lbs is a breeze and is available almost immediately(2500 rpm). Fuel delivery at WOT is healthy and there are no cam timing or missfire issues. The thing is LIFELESS after 4000 rpm, however. From 25-3900 rpm is an assault of torque that leads you to believe it will be backed up by some horsepower from about 4-5k rpm(sounds reasonable, right?). But something is missing. Everything I can view from the cabin seems to be in order but it just feels like there is absolutely no timing past ~4000 rpm. You can almost hear it through the exhaust; like something crucial is lacking.

So that's the reason behind the LA3 inquiry in regard to timing. What could cause the truck to run so wonderfully up until the beginning of climax and then have a sudden change of heart? Is that just the reality of the RR cam? Or could it be a VAM sending a part throttle voltage value at wot? What should I truly expect after 4K rpm?

Ok, rant off.

[jfive]

Don't you want timing locked at like 20* or around there for the upper rpm. Personally the Ranger Roller cam is only good till 5000 or 5500 with port work. A turbo grind cam would be better. Also if the turbo spools early than it may be running out of air in the upper rpms. Might be blowing hot air at the top of the powerband. You do need to get ahold of caroth or svojohn. Might try Theturboforums.com for svojohn, as turboford is a bitch to get signed up on. There is another guru on turboford and eectuning.org that has cracked the rev limiter code, and he would probubly be a good one to ask. I thought timing was to be around 10 at base? Think you have too much timing is your issue.

[AirBender]

yeah, back the timiing down to 10 and get a larger turbo.... youre running out of turbo.. i just sold a turbo off of a subie sti and its tiny.....

[nik97]

Ok I'll bring it back to 10*. I just had a turbonetics t3/t04b 57 trim that seemed to be too large. It'd spool at about 3500 but the motor, as stated, would have nothing after 4k so it was useless. The vf39 can easily support 350hp at 5500 rpm(tends to drop off on an sti at about 5800) and I love having something that does not take 75% of my usable power band to spool.

Something else is going on that makes this thing fall flat on it's face(like 120hp flat) at 4k. I'd be happy if it'd pull to just 5k.

[nik97]

Well, I fixed it... I can't wipe the stupid grin from my face :D


So I checked base timing and it was at about 14* and I brought it down to 10* and it was worse, alot worse. So I brought it to about 22* according to my rickety-ass lower cover and drove it... What a blast! still spools around 2700 and rips to 5k like it wants to.

This means my dizzy was retarded a tooth? I think so because it wont even ping untill about 32* base(according to my lower cover and likely retarded dizzy)

Either way I'm thrilled. I feel like all my struggles with this fu***r are worth it. :)

[tcranger]

maybe your cam is retarded and tooth?? and just wondering are you pulling out your spout when your checking the base timing? glad it runs good though. just asking these questions because mine with 10*base and the tiny ihi pulls to 5500rpms with little prob. after that the turbo runs out of breath:turbob:

[nik97]

maybe your cam is retarded and tooth?? and just wondering are you pulling out your spout when your checking the base timing? glad it runs good though. just asking these questions because mine with 10*base and the tiny ihi pulls to 5500rpms with little prob. after that the turbo runs out of breath:turbob:

You mean advanced. But no Cam timing is dead on(actually retarded about 2-3* for a little more on top). And spout is out, hence base :cheers2:

[tcranger]

yup just checking. yah i meant advanced...

[D94R]

The dissy can't be retarded or advanced by "teeth". It's either retarded or advanced in relation to cylinder #1 by loosening the clamp and rotating the distributor.

That being the case, are you 1000% sure on the timing of the cam? If with both the 57trim and the STI turbo it fell on its face at about the same rpm I'd still be suspect that it's not totally solved.


And "hence base" tells us nothing really. You'd be surprised how many people set "base" timing without knowing what the hell the SpOut even is.

[nik97]

Put it this way, I can adv/ret the cam 1 tooth in either direction and that makes it very unhappy in it's own respect(advance or retarded). I can adjust the cam gear advanced or retarded around 8* or so and I get the same result, just not as pronounced as it's not a full cog's worth.

The motor runs good now set at 20*; the turbo stays alive to 5k rpm so I don't suspect cam timing.

I think that there may be a degree or 10 of error in the lower cover from which I am setting base ign. timing and 20 degrees is not the real number. You can literally loosen it and get probably 8* of play.... Perhaps it's time for an Essy pointer.