COBB Tuning

iTrader: (1)

E85 is a blend of 85% ethanol and 15% gasoline. Originally developed as a bio-fuel for "flex fuel" domestic cars in the US, E85 has become the alternative fuel of choice for performance enthusiast. The allure of this biofuel comes from its high octane compared to regular pump fuels - 91 to 94 compared to 105 - and a very low price compared to higher octane race fuels. In many parts of the USA E85 costs as little as 2 dollars per gallon. When compared to 8 to 14 dollars quality high octane race fuels E85 represents a huge bargain.

If you don't know about E85 you're naturally asking the question "why am i not running e85 every day?". The answer is you can't. Most stock vehicles are not calibrated or equipped to utilize ethanol based fuels.

Despite having a higher octane rating, E85 has a lower overall energy density than pure pump fuel. Pure gasoline contains approximately 125,000 BTUs per gallon, while E85 contains approximately 84,000. This means that a greater volume of E85 must be utilized to realize the same energy content. This lower hydrocarbon content is mirrored by the stoichiometry of E85 and pure unleaded gasoline. Complete combustion of pure gasoline requires 14.7 parts air (mixed gas air with 23 percent oxygen) with one part fuel. In contrast, complete combustion of E85 requires a much higher relative content of fuel with only 9.7 parts air required. The distillation of this information means that larger volumes of E85 are required for equivalent combustion when compared to pure pump fuel. Thus, the cost savings associated with lower E85 prices is offset by an overall reduction in fuel economy. (taken from driving sports article "methanol injection vs E85" i wrote the article so i'm plagiarizing my own work. http://www.drivingsports.com/site/2008/07/...anol-injection/


The graph below shows the stochiometry of E85 (lamda) is similar for pump and E85 but the volume of fuel required for E85 is much higher by proportion (Air to fuel ratio).



Despite these limitation of E85 we wanted to tune our GTR to utilize this fuel. Together, the lower cost, higher octane, and higher overall power potential are simply too much to resist. Furthermore, because E85 has not been used in the new GTR platform I simply couldn't resist the technical challenge.

Because a stock GTR can use nearly 100% of its available injector capacity on pump fuel the first step in using E85 is to replace the stock injectors with larger units. We chose to use Deatschwerks 800cc injectors. These are ~30% larger than stock and should be able to provide the additional fuel volume needed for E85.

The injectors were installed and the car tuned on pump fuel:

Stock - completely stock calibration with 92 octane pump fuel - BLUE

Stage 2 800 cc - COBB catless midpipe, COBB prototype cat back exhaust, stock intake, stock fuel pump. - RED



We then drained the tank and refilled with E85 full. I adjusted the calibration with COBB AccessTUNER Pro software and prepared to run the car. The first few runs were done at low boost and all was well.

The calibration was then adjusted for higher boost and we attempted a full run. I aborted the run because the motor went progressively leaner at RPMs and fuel demand increased.


This increasing lean condition clearly points out a lack of fuel delivery. Because our injectors are mathematically ideal for ~30% higher flow it's clear that the stock fuel pumps simply cannot keep up with higher duty cycle with 800cc injectors.

To combat the lack of fuel we installed two walbro 255s in the place of the stock fuel pumps. The installation took about 4 hours total as the stock in tank fuel surge tank needed heavy but straightforward modification.

With new fuel pumps installed we went back to the dyno with high hopes of sufficient fuel delivery. The results are presented in the graph below.


Stock 2009 GTR - 92 octane - BLUE

Stage 2 800 cc - COBB catless midpipe, COBB prototype cat back exhaust, stock intake, stock fuel pump, 800 cc Deatschwerks injectors - RED

Stage 2 800cc - E85 - COBB catless midpipe, COBB prototype cat back exhaust, stock intake, Twin walbro 255 fuel pumps, 800 cc Deatschwerks injectors - GREEN

This E85 Stage 2 configuration is now the highest HP and torque stock turbo car tuned on our Mustang dyno. When the weather clears here in the pacific northwest we'll find some dry test roads and report V-box data. We're also planning to rent a local drag strip for development and testing so ETs and trap speeds are coming.

As a next step we plan to install some custom intakes. If our early observations are correct this car will make more than 600 whp on stock turbo's with E85.... all while retaining the factory downpipes.

Best regards
Tim Bailey
Lead GTR calibrator
Cobb Tuning SurgeLine
Lead GTR calibrator

Z_Nick_Z

iTrader: (14)

wow, the GTR is just an amazing car. good job on tackling that technical challenge

i cant wait to see some more results

John@z1

iTrader: (2)

Great job guys.

Entaille

iTrader: (16)

impressive! I knew about the e85 craze but never understood how it works, so thanks for posting that.

StrafeAuto

nice #'s

UMW350Z

iTrader: (18)

You have to live near an E85 pump, you will drain that tank quickly running it hard

COBB Tuning

iTrader: (1)

We just recieved this PM, I thought I would post it (name removed to protect the innocent) to answer any potential questions.



The comparisons do have increased boost pressure, however, there is a limit to how much boost you can run on standard pump fuel before detonation starts to occur. While most premium pump fuels range between 91-93 octane, E85 is 101 octane, allowing us to push the engine much harder. E85 is also oxygenated and it has greater cooling properties than straight gasoline.

The downside to E85 is that you have to run about 1/3 more fuel to acheive comparable AFR, this means larger fuel pumps and injectors and extra tuning, you cannot simply dump E85 in your tank and go. Read the post again and there is a link to another document explaining E85 tuning in more detail.

http://www.drivingsports.com/site/20...nol-injection/

Travis
COBB Tuning

Bumpinjeep

iTrader: (3)

Hows the gas mileage after the new tune?

COBB Tuning

iTrader: (1)

Tim Bailey, tuner and owner of the GT-R in question, reports that his mileage has stayed around the 10mpg mark... that should tell you something about how he drives and the lead composition of his right foot...

UMW350Z

iTrader: (18)

by your BTU numbers, you could interpolate a E85 is roughly 67.2% as efficient as pure gas, all other metrics the same. If gas is 10% ethanol, it could be more like 75% as efficient. The owner must live at the pump or at least have a PO box there.

If E85 was available, i'd definitely look into it for the Z. The only thing that makes me weary is the extra corrosion.

Do the emissions smell the same as an all-gas engine?

Adon

iTrader: (2)

thanks for posting this, better yet thanks for doing it, amazing results, this is why COBB tuning is the leading after market tuner for the GTR in North America by far.....

all I see other shops like Hennessey doing is slapping on bigger turbos and calling it a day, nothing compared to COBB.

Sisko99

Seeing as your customer will be running E85 all the time, did you not upgrade your fuel lines and seals? From what I understand E85 likes to eat those (for converted regular gas cars) and thus you need to change to a different material.

Armitage

iTrader: (15)

So to run E85, you only need to upgrade the fuel equipment for higher flow to accommodate for the increased demand in fuel, not actually to allow the use of E85?

xenonZ

very nice i must say

kennedy

iTrader: (16)

Not to thread jack but just maybe alittle more info and cobb if you don't want it here pm me and I can delete it. My buddy is an engineer and sent me his write up on e85 which also gave me a greater understanding for the fuel.

Taken from a Pm my buddy sent me about his write up e85 from xceedspeed.com

ok first off i offer a few pointers on things. namely your fuel pump (granted you already have, but just look)



the walbero dies off hard at 80psi....granted you'll never cross 70psi on stock turbo..theres still a 90lb/hr flow difference between the two.

the biggest difference is that the Bosh pump has viton seals and has been tested, proven and validated on e85...the walbero has not.

also, another quick fact. the bosh 044 there is the oem pump out of the 911 turbo....that car carries a e85 cert.

none the less, on to injectors and such.

now i've never played with a stock evo ECM, just stand alone cars (apexi, AEM, and my fav HKS!)

so i'm going off general ECM tables and settings...

inside the ECM there is a IFR(injector flow rate) table/ setting (from now on, i'll just say table) as with any ECM there is a limit of what you can enter as a valve as that table has a internal limit.

are the 1000cc injectors past the bounds of that table? if so then you'll have all sorts of part throttle and low speed (idle, ect) drive ability issues because the injector is dumping more fuel then the computer can control. there are several creative way around that table tho, mostly with battery voltage modifiers.

however if that injector can be entered into the computer then your part throttle conditions wont suffer much, however your low speed and idle settings will be off.

the car will idle surge as the injector pulse width drops in and out of the .15ms range.

when it drops below the .13-.15ms pulse width duty cycle range the computer "looses track" of the injector. the engine will start to stall, then the stall saver inside the ECM will kick in and rev the engine, thus bringing the duty cycle up and it'll calm down again...only to repeat this process over and over again.

now if your stock ECM tuning software gives you access and control to the "injector offset" tables your in luck.

these tables scale the injectors against MAP sensor inputs and battery voltage.

you can use these offsets to "adjust" the low speed properties for the injector (by enlarging the offset)

the offset is added to the injector pulse width to help keep the pulse width above that range i talked about above.

in order to help you out here, here are pictures of what i'm talking about. there from my GM ecm but it'll hopefully help you understand things here.

first one is my list of avalabile fuel control settings, you can see the offset tables in the middle there.


you can also see that theres a box that allows me to enter a minimum pulse width, so that no matter what the injector drivers reports to the ECM the ECM will never register any thing lower that what that value is. however the proper offsets still make the car idle like factory.

heres a snap shot of an offset table (***** to tune, but worth it)


now, the min PW box might but unaccessible via your software, and the same might be true for the injector offset tables.

however its a fact that they are there, inside teh ECM.

i'd like to take a look at your stock ECM with what ever software you have as i might be able to save you several head aches.

let me know if you have any other questions, or if i left any thing out here.

Bryan-

kennedy

iTrader: (16)

I agree unless you have plastic lines then you would be fine... I am not sure what the gtr has or the Z in the end result yes e85 is cheaper but it takes more to use it so you are back to square one for the most part...

COBB Tuning

iTrader: (1)

I will let one of our tuners respond to your concerns. However, I would make a few points first:

We have been using the Walbro pump in many other E85 applications and to date, have not had a single failure related to E85 use. These are intake pumps, mostly for Subaru applications in the NW where E85 is readily available. The Bosch 044 is an inline pump and would require a completely custom fuel pump assembly to be used in-tank. I will link to the install process for the GTR, but it is not simple to say the least. The GTR features both dual pumps, stock AND an intake surge tank.

Our external pump setups for running E85 on larger turbos involve a single walrbo pump feeding an external fuel surge tank and then either a single or dual bosch 044 pumps feeding the fuel rails etc. Since this is a stock turbo setup with just a catback, we still had injector left on the dual walbros at higher boost levels. Doing a complete turboback exhaust with intakes, might max out even this setup and we would be looking at running a "built" fuel system like this one we recently did on a 35R-powered STI that made 540whp!



As for rubber fuel lines, this is a concern and only long-term testing will determine if this is a place where we will need to replace the stock lines with proper fuel line as the GTR uses soft rubber "accordian" lines. However, for the purposes of this initial test, this was not a concern as this car will not be running E85 all the time.

That said, there is a lot of misinformation out there about the corrosivness of E85 on modern stock fuel systems. Granted, again, most of our experience comes from the Subaru and EVO world, but these stock systems are more than capable of handling E85 over the long term. Also, seals seem to be unaffected by E85. If you have enough E85 in your oiling system to eat engine seals, fuel lines are the least of your worries.

As for injector offsets, I will let our tuners deal with these questions, but in a word, yes, we do have the ability to offset injector scaling to run larger injectors as we are able to run this setup on both pump fuel (92 octane) and E85 with normal idle operation.

Travis
COBB Tuning

COBB Tuning

iTrader: (1)

Kennedy:

The Cobb AccessTUNER software for GTR can scale injectors as large as 2000cc with two separate tables for to control latency including offset and a votage dependent multiplier. Properly tuned, there is no issue with running larger injectors in a GTR.

We've been using walbro pumps with E85 for more than two years in other vehicles - subaru's in particular. I do not hesitate to recommend walbro pumps for use with E85.

Best regards
Tim Bailey, Calibrator
Cobb Tuning

kennedy

iTrader: (16)

As clearly stated at the top of the post it was what Friend who is an engineer posted for e85. I am not against walbro just what he stated he had experience with. Would it be worth using e85 on a bolt on hr car? If you say the factory lines can hold it I would be more then interested in using one of my maps for e85 and put bigger injectors and fuel pump in.

rcdash

iTrader: (18)

I'm sensitive to fuel vapor odor and I think E85 exhaust emissions smell a whole heck of a lot better based on my brief experience with Joe K's car at ZdayZ.

Nice post Tim@Cobb!