E85Forum.com

Mb49 · Joined: 10 Aug 2010 Posts: 3 Location: New York

I have a 1989 Bentley Turbo R. It uses Bosch Motronic Fuel injection. Can someone please tell me what needs to be done to increase fuel volume so that I can run E85? It's a dollar cheaper than premium here, and I want the performance advantage from the cooler intake charge.

Mb49 · Joined: 10 Aug 2010 Posts: 3 Location: New York

Someone here must be able to at least point me in the right direction. Anyone?

slowboy0 · Joined: 08 Aug 2010 Posts: 14 Location: Duluth

Give it some time, somebody will help out.

murphinator · Joined: 08 Jan 2010 Posts: 93

well I left this post alone figuring someone more qualified could take a crack at it but I guess I can get a few ideas out there for you.

first off do you have a means to tune the vehicle ? especially in regards to fueling : make changes to injector data ,change stoich settings in the tune ,etc.. ?

if not then you would have to do it in a much less precise manner ( being polite here some would call it hack tuning)

converting to 100% e85 is going to take somewhere in the neighborhood of 30% more fuel across the board and the most straight forward way to come close with no means to tune would be to replace your injectors with units that are rated at approx 30% more fuel flow - MAKE SURE THEY WERE RATED AT THE SAME PRESSURE AS THE STOCK INJECTORS or else you will need to consider how much larger than the 30% you will need to go if rated at a higher pressure , or how much smaller you will need to go if rated at a lower pressure

there are typically many injector parameters in any tune beyond the flow rate and the likelihood that all or most of the characterization matches closely between any 2 injectors is low so you may have some issues to overcome due to some mismatched data for the injectors you choose.

you could also increase the fuel pressure to increase injector fuel flow but probably not enough to gain 30%

you could also run out of fuel delivery which you would address with higher rated fuel pump , increased voltage to the pump under high demand conditions ( boost-a-pump) and less likely fuel supply lines being too small unless this car is modded then that could be a concern also

I have yet to run anything on 100% e85 but have been blending with gasoline until I have all the upgraded parts to do it properly on one of my vehicles which I am in no rush since I have to drive 2 states away to the nearest e85 station (Boston) , even e25 can make for some nice gains in boost & timing while only requiring a small bump in fueling and some cars seem to tolerate small amounts well on a stock tune

I am no expert in this and only threw out my thoughts to give you something to start thinking/researching about - I am fortunate enough to have software capable of scanning to check running conditions , editing my tune to make changes to accomodate things like larger injectors , and a wideband oxygen sensor to verify that I am running in a safe Lambda/air fuel ratio range ( you should strongly consider getting one)

I am still trying to gain all the knowledge needed to run e85 on a modded efi car without any incidents and you and I have both found a great spot for that here Cool

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PB's 1/4 mi 12.209, 117.75 trap ,1/8 mi 7.76 ,93.99 trap , 1.949 short time 4.53 0-60

I tune with HP Tuners software

TimZ · Joined: 02 Feb 2008 Posts: 48 Location: Dearborn, Michigan

My vague recollection of this was that there was a weird mechanical/electronic fuel injection hybrid that was sold for a while, and it sounds like this might be that system. Mechanical systems used a different injection scheme, and might not be easily adjustable for flow like the newer electronic systems are.
Do you have any additional info on the MK-Motronic system? I can't seem to find much except for the same marketing blurb repeated on a thousand different sites. A system schematic or service manual info would be helpful to allow us to give an idea as to how you might go about modifying this system.
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Information is not knowledge
Knowledge is not wisdom
Wisdom is not truth
-FZ, Joe's Garage

hotrod · Joined: 19 Apr 2005 Posts: 872 Location: Colorado

This article implies that your system is an electronic fuel injection system not a mechanical fuel injection.

http://www.hiperformancestore.com/Motronic.htm

If this is the system on your car, you basically have the same options and problems that any electronic fuel injection system has when converting to E85.

As mentioned above your basic goal is to increase fuel flow by 30% over stock flow rates. There are several ways to do that.

You can increase fuel pressure by changing the fuel pressure regulator to give a higher fuel pressure. Fuel flow goes up at the square root of the pressure change.

Second option is to put in large electronic fuel injectors intended for a larger displacement engine. You might call a fuel injection cleaning service like witch hunter or RC engineering to see if they know of a higher flow injector of the same type.

Third option is to fool the air sensor into thinking 30% more air is going into the engine than is really being used. To do that you need to understand exactly what type of air sensor your system uses and figure out a strategy to trick it into reporting the wrong amount of air. In some cases that is as simple as adding a resistor in line with the wire the ECU gets its air flow data from but without knowing exactly what sort of sensor you have I cannot even guess on how to do that.

The forth option is to use a piggy back system that intercepts the injector pulse, and electronically lengthens the pulse duration by the proper amount.

Some of us use a little bit of several of those strategies. For example it is difficult to raise fuel pressure enough to get the whole 30%, but sometimes increasing it from perhaps 43 psi to 55 psi is enough so that the engine management system can adapt enough to allow you to at least use a high blend of ethanol like E60.

Larry

Mb49 · Joined: 10 Aug 2010 Posts: 3 Location: New York

Thank you everyone for all the help and information! Smile

I'm still digging through all the documents that came loaded with the car buried under the shag carpeting in the trunk and what did I find today but a service manual for the fuel injection system (and a manual for everything else on the car). Wow. Is there a way to post this to the forum?

E drifto · Joined: 26 Mar 2010 Posts: 12

if it's anything like the vw with the same management, the stock fuel pump should have no problem pushing 30% more fuel pressure

i'd just put on an adjustable fuel pressure regulator, fuel pres guage, confirm stock fuel pressure & turn it up 30%, like 60 psi from 45 psi

you "should" get it tuned, but even without a wideband you could get it right

also, the first tank really seems to clean out the system so i'd change the fuel filter after the first tank or two or when it clogs up
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1987 16v Scirocco w P1SC-1 Procharger
recurved cis-e jetronic - flex fuel knob on the dash

TimZ · Joined: 02 Feb 2008 Posts: 48 Location: Dearborn, Michigan