Single Turbo 4.8L on E85 *Lots of Questions*

[bfurches]

Quick run-down of the combo:

1981 Caprice Classic
2004 4.8L (Bone stock aside from valve springs and Comp's Smallest Thumpr Cam)
Holley Modular Mid-Rise with 90mm Throttle Body
2004 4L80E Manually Shifted (TCI Valve Body with Transbrake)
Single Garrett 70mm Turbo
Turbonetics RG45 Waste Gate
Versafueler & 120lb Low Impedance Injectors
Holley Dominator Twin Fuel Pump
Holley Billet Regulator
-10 Feed -8 Return

Here is where I'm at as of now...



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I am at the point of the project where I need to build a harness and choose a PCM.
I already have a 2004 GTO PCM which is the direction I am leaning towards.
I definitely want to run E85.
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Now given the information above, I am looking for some help!

2004 GTO PCM: Does anyone see any reason NOT to run this PCM for my combo? Is there a better GenIII unit I should be looking for that would offer any additional control/ fine tuning? Since I will be pinning a harness from scratch...if I am going to jump ship on the PCM, now is the time to do it!

Map Sensor & OS Upgrade: For my application, I don't see myself running more then 15lbs of boost. I suppose its a possibility, but I don't think the motor would be able to handle it anyways. As for a map sensor, I know I can use my 3-bar with the 2-bar OS...but what about resolution? I understand you loose some of the resolution by going with the 3bar enhancement....is it that noticeable for tuning? Given my combination, which version of the OS enhancement am I better suited to run?

E85 Tuning: I have read several different perspectives and versions of tuning....overall it seems basically the same as I was doing before on pump gas. Load a custom PID to monitor AFR % Er and adjust the tables accordingly....what really changes when starting fresh on E85? How should I setup my stoich values? How do I even calculate a safe base map given my cam and fuel choice to even get the car started? I am a little lost here with my base tune as I have never started with something so far off from stock.

Custom PID: I am not running the pro version of HP tuners, so my wideband will be processed through the AC pressure switch. Does anyone have a custom PID for the AFR % Err on e85, or is it the same PID as I was using for pump gas?
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Thanks in advance for any help!

[HRD]

I'm running a similar build in my 54 pickup. 5.3L turbo with the Holley Hi-Ram. http://www.hptuners.com/forum/showth...-my-3-bar-tune. I went with the 3bar OS and the brick style MAP. I did learn that even though the LS9 3bar map sensor fits that intake, a gen 3 PCM will not allow the correct negative map sensor offset, so I went with the older brick style MAP sensor with a vacuum line. If you are using a LS2 style cam sensor and timing gear in the front cover, you will need to swap the wires in positions A and C in the cam sensor connector. I know that doesn't answer your questions, but those were a few hurdles I had to overcome so I thought it may be of help to you.

[bfurches]

HRD, thanks for your response and sharing your experience.

I too am running the older brick style 3-bar, but I was unaware of the GenIV sensor issue! Thats great information to have.

As for cam sensor, I am still running stock location back of the block.

Your truck looks really good from the single picture linked above. Very nice vehicle.

[HRD]

The wide band reads Lambda, not A/F ratio. It gets A/F ratio by multiplying the Lambda value (or dividing by the Equivalence ratio which is just the inverse of Lambda) by what you have in the Stoich A/F ratio field. To the best of my knowledge, you should be able to use all the same PID's as with straight gasoline, just change your Stoich ratio in the tune. The stoich ratio for 85% Ethanol is 9.76. Problem is E85 is generally not exactly 85%. It varies quite a bit from region to region and from season to season. I believe most people are using 9.8 for the stoich ratio when on E85.

[RonSSnova]

I set my stoich to 9.76. Have been debating on first fire with gas, but might as well learn E85 from the get go.
I made my own 3 bar MAP.
I plan first start tomorrow or sat. So nice to tag along.

You guys have nice rides. Here is my effort



Love the room in that Caprice! Novas are cramped up front.

Ron

[bfurches]

Ron, good luck with the nova. Clean combo.

...anybody else care to chime in on my questions?

[MustangPunk]

Ron, good luck with the nova. Clean combo.

...anybody else care to chime in on my questions?

I've never messed with GTO PCM's so no answers there. I would spring for the 3 bar, you never know when you're going to want more, and loss of resolution hasn't caused me any problems yet. My turbo 4.8 loves boost I run about 14 lbs atm with intentions of more boost this summer when I get a water meth kit, the 4.8's take it and love it..

When tuning with e85, like mentioned I would get a test kit to test the fuel at each fill up, and adjust your stoich accordingly. I would just tune in Lambda also... Lambda VE Err % not AFR etc.. The base tune to get running by using stock 4.8 silverado tune for most settings and copy VE rows from 100 kpa and below to correct rows, and take the 100 kpa row copy it to the last row in the 3 bar and multiply it by 30-40% and interpolate and should be pretty rich in boost for tuning.

[gn2beatu]

If the ECM is an E40 from an LS2, then your better off with a 411 ecm IMO. Look at a 03-06 silverado harness and pcm.

[MustangPunk]

If the ECM is an E40 from an LS2, then your better off with a 411 ecm IMO. Look at a 03-06 silverado harness and pcm.

04 GTO should be a LS1, but I don't know if it's a typical LS1 PCM