LA3 question

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abomb1982
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LA3 question

Post by abomb1982 » Thu Mar 01, 2018 10:21 pm

I have an opportunity to get an LA3 and the big vam. How much gain would I actually see over stock?

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Re: LA3 question

Post by hbar » Thu Mar 01, 2018 11:38 pm

My understanding is that there is little benefit to that swap with an otherwise stock setup. The improvement is to be found in a greater capacity for airflow that is only realized when you make other modifications such as increasing boost, running fully 3" exhaust, and doing the necessary supporting mods (efficient intercooler

At 16- 20 psi of boost (perhaps 175-220 hp) you should see noticeable performance gains from the bigger VAM and ECU.

But then, the larger VAM is itself limited. Once you push past 220 hp or so and need to upgrade the fuel pump and get bigger injectors (among other things) it's much better to switch to an aftermarket programmable EFI with MAP sensor (like the PIMP) and toss the VAM and computer.

I'm currently making these mods right now and am basing this on what I've learned from others. I expect to have first hand results when I get my XR back on the road in a couple of months.

Others may have differing opinions based on their own experience.
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Re: LA3 question

Post by thesameguy » Fri Mar 02, 2018 12:34 am

IMHO, LA3 by itself isn't worth much if anything. But with an intercooler it's relevant and useful, and opens up a lot of headroom that the stock ECMs really don't offer.

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Re: LA3 question

Post by merkurdriver » Fri Mar 02, 2018 2:19 am

Stock XR 175 HP, stock 88 Turbo Coupe 195 HP, so stock-for-stock the LA3 with big VAM would add 20 HP.

The beauty of the LA3 (to me) is that its a 16 bit processor vs stock XR 8 bit. I had an XR that put 272 HP to the wheels with an LA3 (with a piggyback chip for bigger injectors) and a big VAM.

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Re: LA3 question

Post by thesameguy » Fri Mar 02, 2018 2:27 am

The 190hp '87/'88 TurboCoupes were intercooled... that's where the power came from. :) You're not gonna see any useful increase with just the ECM. Drivability and probably emissions? Sure. But not power.

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Re: LA3 question

Post by Ed Lijewski » Fri Mar 02, 2018 8:41 am

My butt dyno says the swap is well worth it. Last year I installed an 8UA and big VAM in my otherwise stock automatic (cold air intake only) including adding the Air Charge Temp sensor in the upper intake. Performance difference is yuuuuge; the ACT difference during cool/cold weather is eye if not also butt opening (those who don't install an ACT leave a lot of performance enhancement on the workbench).

My other XR has a PE ECU-which truly leaps forward when asked to. Both swaps are well worth the minor cost and effort.

YMMV
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Re: LA3 question

Post by John Brennan » Fri Mar 02, 2018 9:37 am

Ed Lijewski wrote:
Fri Mar 02, 2018 8:41 am
My butt dyno says the swap is well worth it. Last year I installed an 8UA and big VAM in my otherwise stock automatic (cold air intake only) including adding the Air Charge Temp sensor in the upper intake. Performance difference is yuuuuge; the ACT difference during cool/cold weather is eye if not also butt opening (those who don't install an ACT leave a lot of performance enhancement on the workbench).

My other XR has a PE ECU-which truly leaps forward when asked to. Both swaps are well worth the minor cost and effort.
Intercooling, with each car? I know the PE definitely needs it.
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Re: LA3 question

Post by Ed Lijewski » Fri Mar 02, 2018 10:15 am

No intercooler on the 8UA car.

YMMV
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Re: LA3 question

Post by jasonty » Fri Mar 02, 2018 7:25 pm

I did an LA3 years ago w/ Big VAM, ACT & MP IC, full 3", CAI, on a slightly modded head/block= Great improvement on the butt dyno;
Then I swapped to a PE and that= DAMN!

John Brennan wrote:
Fri Mar 02, 2018 9:37 am
Ed Lijewski wrote:
Fri Mar 02, 2018 8:41 am
My butt dyno says the swap is well worth it. Last year I installed an 8UA and big VAM in my otherwise stock automatic (cold air intake only) including adding the Air Charge Temp sensor in the upper intake. Performance difference is yuuuuge; the ACT difference during cool/cold weather is eye if not also butt opening (those who don't install an ACT leave a lot of performance enhancement on the workbench).

My other XR has a PE ECU-which truly leaps forward when asked to. Both swaps are well worth the minor cost and effort.
Intercooling, with each car? I know the PE definitely needs it.
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Re: LA3 question

Post by merkurdriver » Fri Mar 02, 2018 9:54 pm

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abomb1982
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Re: LA3 question

Post by abomb1982 » Fri Jul 13, 2018 6:52 pm

will buying a PE ecu allow me to run higher boost without going lean?
I ask because I was thinking the other day that I modded a bunch of things on my car and turned the boost up to 20 psi but have know clue if that is save running the stock ecu.

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Re: LA3 question

Post by merk23literturbo » Sat Jul 14, 2018 5:28 pm

will buying a PE ecu allow me to run higher boost without going lean?
No, the EEC has no way of knowing what boost you are running. If you are not using a wideband sensor to monitor your air fuel ratio, you will break expensive stuff.
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Re: LA3 question

Post by Ed Lijewski » Sat Jul 14, 2018 7:26 pm

A qualification I recall Dave Planakis noting to Don's point above is that the PE does run "pig rich" under load, to cool valves e.g., more than the PF/PK series and probably the LA series also.

YMMV
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Re: LA3 question

Post by andyofcolumbusmerkur » Sun Jul 15, 2018 10:19 am

Ed Lijewski wrote:
Fri Mar 02, 2018 8:41 am
My butt dyno says the swap is well worth it. Last year I installed an 8UA and big VAM in my otherwise stock automatic (cold air intake only) including adding the Air Charge Temp sensor in the upper intake. Performance difference is yuuuuge; the ACT difference during cool/cold weather is eye if not also butt opening (those who don't install an ACT leave a lot of performance enhancement on the workbench).

My other XR has a PE ECU-which truly leaps forward when asked to. Both swaps are well worth the minor cost and effort.

YMMV
Second this, more aggressive maps for sure. Feels more lively and boost comes on quicker. Not just that peak hp number but all over the place is better. Be sure to play with base timing, also some performance to be had there.
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Re: LA3 question

Post by my8950 » Mon Jul 16, 2018 6:15 pm

I think they all go pig rich under load. On my stock 89 way back, I did have a WB installed because I could. Once it went into boost the A/F went to roughly 9:1 I believe, some ridiculous number.

Regarding ECU swap to the LA3/8UA types, I've read that the benefit is the 16MHz clock speed among other things improves the performance. As mentioned it also gives more "headroom" for modifications.

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