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Flex Fuel Conversion

16K views 38 replies 17 participants last post by  OutlawTBSS 
#1 ·
I just finished a story for Truckin' magazine on converting a stock 2008 AWD TBSS to Flex Fuel. We even ran it on the dyno, and (surprise) it picked up power with 3/4 of a tank of pump E85. I plan on following this up with another test using a boosted combo. Let me know what you guys think and any questions.

How to Convert a Gen IV GM Truck to Flex Fuel for More Power

Sources:
KraftWorks
KraftWorks | Proven Performance

Lingenfelter Performance Engineering
Lingenfelter Performance Engineering

EFI Live
EFILive - Home

Titan Motorsports
Performance Car Parts | Supra | EVO | WRX | Porsche | TitanMotorsports.com
 
#3 ·
Good info. I just started this conversion on my 06 2 weeks ago. Looking forward to trying this out.
 
#10 · (Edited)
Tuning is not different then a 07 with an E67. (Same Maf limit, same 8 g/s IFR limit)

If you get into boost at a higher level you have to run an SD Custom OS.

I have quite a few E40 vehicle with larger injectors on E85 out there. Now it isn't as easy as a 2009+ E38 with a 16 g/s limit but sometimes you have to earn your paycheck.

For the purposes of the truck in your article though, it would be exactly the same. I suspect the stock 255 fuel pump would have been ok at the 335whp level as well and only needed an injector change.

I have seen a single 267 pump support well over 600whp N/A on E85 with 60lb @ 3 bar injectors.
 
#12 ·
Perhaps I am confusing the early E67 with the later (2012+) version, but I didn't think those had the same injector limit problems as the E40. IMO once you get into that funky injector scaling, it is definitely not something a novice/intermediate level tuner will accomplish (to say nothing of Speed Density and a custom OS).

As for the pump...I went by LPE's recommendations, which wasn't just about the volume but about the materials as well. Plus I like to err on the conservative side. If someone gets away with a stock pump then great, but if not I don't want them blaming me (or the magazine) for thousands of dollars in damage. Not mentioned in the story, we were originally supposed to be installing heads/cam with a higher compression after this. Plans changed, though.
 
#19 ·
Very cool, thanks for sharing. I have am doing the same conversion to my TBSS once it gets back from the body shop. The thing that concerns me is the potential restriction presented by the FlexFuel sensor (it has a "ring" inside) which cannot be good for total flow on the feed side; and I understand this is why most of the time running a return-style system with the sensor there is preferred.

In my case I am splicing the sensor into one of the two fuel rail cross-overs.
 
#21 ·
I did a full flex fuel conversion on my Fiero recently. Turbo 3.4 DOHC with 19 PSI of boost. And what a difference it has made. I was limited to about 11 PSI on premium, 15 PSI on race gas, but E-85 I run 19, but its making my clutch slip, probably in the upper 400 to lower 500 HP range. Love it.

Not to stray off topic by droning on about my Fiero, I've been considering doing this for my otherwise stock 08 2WD TBSS.

I used to run Nylon fuel lines in my Fiero, just like the TBSS uses stock. But I was concerned with how the nylon fuel lines handle E-85. Most things I read suggested that the nylon fuel lines are not compatible with E-85. I tired to find any OEM E-85 applications that used nylon lines and it was inconclusive. So I converted my car to run stainless braided Teflon lines. A little pricey, but its so pretty. I'm wondering if you know something about compatibility that I've missed.

Second thing, I have HP Tuners for my TBSS. The only params' I could find for flex fuel was "Sensor Present" and "Sensor diagnostics". Not sure yet what other related tables are available. Do you have a public tune or anything that can lean me in the right direction? I can tune myself, but if my software is somewhat limited, it could be a deal breaker for me.

Bottom line, is that unleaded is slightly more than E-85, but I run premium, so the price gap may justify the reduction in mileage with the additional power. And being able to switch between the two is always necessary for a daily.
 
#22 ·
Newer cars tend to have ethanol compatible fuel lines since most states serve up E10 at the pump. I have been going off others' past experience that it is not an issue. When it is, I will certainly change over and make note of it. In an older car, I would certainly switch over the fuel lines like I did in my '83 Buick.

We used EFI Live, but the process should be similar to what is in the story if you have an E67 ECM.

I would consider E85 as a cheap alternative to race gas, and not use it to try to save money daily driving. It allows you to run more timing and make more power.
 
#23 ·
Update: we just completed an LSA swap (I start a separate thread for that when I have time), and it picked up a lot more power at just 60% ethanol. The bad news is I ran out of fuel pump and the front driveshaft broke. Does anyone make an upgrade or I am stuck with a stock one?
 
#24 ·
I remember when I converted my wife's TBSS to flex fuel a few years back. Till this day, my wife hunts for E85 stations because of how it smells. lol
 
#30 ·
Flex fuel tunes are super popular these days. Even people with n/a setups are doing it.
 
#34 ·
I am in the middle of doing this conversion now, it is amazing how little info there is on this deal. I have picked up tidbits of info here and there as far as parts and install, etc.. I have gotten everything done except for the pinout to my ecu, I ordered some terminals for my harness plug and ended up getting some that were too big after waiting a week for them, lol grrrr!!! Now I think I have ordered the correct ones, GM micro 64 terminals, hoping so anyways.. I like doing things DIY for the most part, so I bring on some of my own frustration, but at least I learn that way.. the parts, fittings, sensor, fuel pump have cost me about $250, I already have big enough injectors, im N/A, so not too bad so far. Hopefully will have it done in a few days then retune for it. My main objective since im N/A is to be able to be more consistent with my timing, with less timing pull, especially in hot weather and hopefully gain a few ponies to the ground, since I should be able to bump up my timing tables, which are kinda low now.. Looking forward to see the results and gain those few 10ths im looking for....
 
#36 ·
I think I finally figured out what Kind of pin/connector to use after 3 tries/orders, should be here Wednesday. Thanks to Chad aka 11-6.2, its a (GM mx64 molex connector).. Ive spent $45 on a $.05 cent connector, LOL.... we will see...
 
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#37 ·
What did you have to do to see the alcohol tables when tunning? I switched over to e85 but when tunning, my guy said the power enrichment tables weren't there. The turck will run on e85 now but the tunning to switch from 93 to e85 is a bit of an issue. Any thoughts or suggestions? I upgraded to 102mm throttle body, 1300 injectors, duel pumps ( no boost a pump ) abd the truck is boosted with a lsa blower.
 
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