I seem to constantly bounce back and forth between carbs and EFI.

I used to be really pleased with the fuel economy of my 4-cylinder with carbs. I really couldn't complain about 30mpg on a carb'd 2.1L type 4. Well, with gas prices going back up, and having installed the 6, I'm getting a whopping 16-18 at freeway cruise, which is unacceptable for me. The motor is a 2.7 built to RS specs with S cams, and it really does go quick, but either the jetting is off, throttle shafts are worn (I know for a fact they are based upon carbon deposits on the butterflies), or I'm suffering from the fact that the 40's were never really meant for a 2.7, so the transition circuit is hugely rich.. becasue fuel mileage is awful.

Anyways, I have this vision in my head of removing the fuel lines, closing off all of the unnecessary ports in the carbs sans the air bleed screws, and essentially converting them into ITB's.

I would adapt a TPS onto one of the throttle shafts, plumb the intake manifolds for vacuum for the MAP, and then weld in injector bosses/bungs which are readily available, and cheap, from various websites for the standard 14mm bosch style o-ring sealing injector. There would be no permanent modifications to the carbs, just to to the intake manifolds.

Am crazy for even trying to attempt to start collecting parts for something like this? The hope is to not spend a whole lot of money on everything, and keep it bare bones with no ignition control, just fuel control.

Brain would be megasquirt, not sure what version yet, but I was also tossing around the idea of microsquirt. I'm not sure what would be the best avenue for something like this.

Any thoughts on this? Don't do it, don't waste your time? etc.

Why not MFI?

If your still thinking of selling , don't do it, sell it, but if you want a fun project,,

you cant tune it from a laptop..

Look up Al's Retro cool high butterfly setup on Pelican. I have the six in mine too and that's what I'm going with plus I've had a good experience with MS.-G

Pray tell, tell us more!

Did you buy it yet, I thought he sold that design to D-Zug to market/sell.
Btw his old 2.7 test mule engine is up for sale on eBay, wonder what he's up to next.

Actually If I don't like my fuel mileage I may do the exact same thing. If you hide the FI and fake the carb fuel lines it would still have the look of a carbed engine.
I'd remove the venturies and just install straight tubes.

If you have Webers I'd sell them and get a set of cheaper Zeniths. This would probably pay for your ECU.

The plan for this was to be a cheap way of going ITB, and making due with what I have. Would I like to run aftermarket ITB's, of course, but I have the webers, and they make an excellent ITB as is.

Then again, I was also throwing around the idea of the Bitz Racing kit that modifies CIS injection setups..

I believe I could make most of my money back from purchasing the kit and injectors based upon how much a set of used webers cost...

Nathan,
He gave me a parts list. I'll be collecting the parts over the next several months and purchasing his custom fabbed parts directly. If you want the whole enchilada it's like $3200, but as I'm away from home I'll be doing my usual scavenger hunt to build the common items like the brain, t -bodies and wideband. Should be a real gas as I was trying to figure out how to run MS on this app like 3 years ago. Once I have the 911tuned and registered again I'll sell my 40ida 's to offset co Ultimately I'm hoping this will be my DD.

Are your heads drilled for MFI injectors? I make adapters that let you drop in EFI injectors. Sell your webers and manifolds. Then buy some good used MFI stacks/throttle bodies for less money. Use the difference to pay for almost your whole MS setup.

There are many ways to get EFI benefits. A CIS plenum would work, would be easy to install. Did your heads get ported? Use a 3.0 plenum that will probably match common port sizes.

I don't think I would close off the webers. Just sell them and put a few hundred into throttle bodies. The current price for nice webers is close to $2K. For $2500 you can get a complete Borla/TWM 3003 setup with manifolds and linkage and TPS and air-horns and fuel rails. Get the idea here? Leverage what you have to offset the cost.

my above TB's have injector ports, cable linkage , and are $50, Mcmark, and I made similar manifolds as did..
http://forums.pelicanparts.com/911-engine-...olaris-tbs.html

The webers are worth way more that you could build an MS setup for. Gather some parts and motorcycle TB's and build the system then sell off the webers. you'll be money ahead and have a fun project.

Pm me, i have the unique ability to probably help you out with this.
plus im sort on the route you drive between work and home.

A while back I picked up a set of Zeniths with the intention of using them on a different 6, however I think I may be using these as possible throttle body options. In my opinin, zenith castings look cooler than weber castings, and they should make nice throttle bodies. Plus, with the auxiliary enrichment circuit removed, there are ports that are left open on the flanges. These can be easily repurposed for MAP sensor vacuum sources.

Also, through work, I have access to a few people with lots of in depth tuning experience on porsche engines, to say the least..


Click to view attachment

EFI is awesome! If you have it properly tuned, it will out preform carbs and get better mileage.

ITB's can be difficult to tune but they look very cool.

If it were me, I would get a 3.2L manifold and adapt it to the 2.7L. It will run way better for your commuting and be easier to tune. It is probably cheaper to build also.

You have many ECU choices. in the long run, they will all cost you similar money. Megasquirt will be slightly cheaper but can be more work if you build it yourself. You WILL absolutely need a dyno tuning session. Maybe more than one.

In every EFI build I have done, it has cost $3000-$5000 all in. Amortize this cost versus your fuel cost and the time you will own the car.

I actually have possible access to a mostly free Pectel SQ6M ECU. That would take care of pretty much every question mark from the system.

If I can find a carrera 3.2 intake, I will pick it up. I haven't been able to find anything cheap though as of yet, but I haven't been looking intensely.

I am in the same boat with my 2.7. I have all the CSI stuff, so I can go the Bitz route. My main sticking points are a. it uses MS 1, which I don't believe can handle spark, and b. it doesn't look very cool with a hacked up air-box. Toying with the idea of a custom air-box to remedy the latter.

MS1 can handle spark, and it's upgradable to whatever you need. I can't imagine using it today though unless it was practically free since the later versions do it all and more right out of the box.

I'm a huge fan of Megasquirt and currently run MS3X in my car. I love the tuneability that it offers.

I'm also a huge fan of MS.....BUT....instead of going through all the gyrations of EFI at this point, why not install an 02 sensor and see if you can do better with the carbs.

For $190, you'll get real time readings. You can then try some jetting to see if the MPG's get better.

If it's still not to your liking and decide to go the EFI route, the 02 sensor will be there for you to tune the EFI.

Unfortunately with S cams, there's really no way to get good fuel economy with carbs. I bit the bullet and had them rebuilt and rebushed by Paul Abbott of performance oriented, and the car runs absolutely spectacular, and the gas mileage is definitely better, but it's still not to my liking.

I think I just have too high of expectations for fuel economy. haha

I'm not familiar with those cams. If they are carb. specific you may be looking at a finicky EFI system to tune, but it still can be done. MS EFI gives you ultimate control of fueling, your MPG's will get better.

If you add the option of timing, it can be rather involved, adding a trigger wheel and all that goes with it.

I've found that being able to manipulate the timing curve plays a big role in MPG's

Unfortunately, the Bitz kit that we are talking about runs MS1 (I believe). I would much rather run 2 or 3.

http://bitzracing.com/products/Partial_EFI_KIT/index.html

your setup was never intended for fuel economy. I would leave the engine the way it is, enjoy it and economize somewhere else.

Question: Do you need an O2 sensor on each bank of headers or would one-side work well enough?

I think I only had MSDS install a bung on one-side of my headers.

Mileage is not produced by fuel injection. It is influenced by energy needed and state of tune. The energy requirement may well have changed because you now drive faster. The drag goes up far more than linearly with speed, especially above 55 mph. That limit was imposed by Nixon in 1973 as he turned up the air conditioning so he could sit by the fire in San Clemente. Really does save an enormous amount of fuel. I suspect that the turbulence produced by the car may goe quite high around 60-65 as judged by my cht in the four banging 2056.
Zenith Stromberg carbs back in the day produced mixture miracles matching those of many FI systems, so I humbly, sort of, suggest tuning the carbs professionally instead. I cannot believe that they are being efficient with the mileage you describe. Unless you cruise at 80. If you do, the fi isn't gonna make energy for you. My 0.02$

I respectfully disagree

Only one side is sufficient. Both combined is optimal.

If you are only able to monitor one side, make it the cylinder #3 side.

Since you cannot individually adjust each cylinder OR each bank of the motor one side is fine.



Since

I respectfully agree.
I was trying to see if the carbs could be saved. Have seen a lot of retrofit fi jobs halted midway with tuning problems that cannot be resolved. I know that webers aren't designed for mileage but my friends with 911s tend to ditch their efi for them. Energy is energy from what I learned in physics. Spend it as you like.

Can you elaborate? As in which part?

With the infinite tune ability of FI ( I'm referring to megasquirt as a retrofit). All fueling parameters can be manipulated for optimum efficiency.

Fueling can be adjusted to consistent AFR's. With carbs you are limited to the "jets" as a metering system, there are limits to what you can control.

As far as being able to control timing, this has far more advantages than the stock dizzy. being able to control, idle timing, how fast it comes in and the upper end has huge advantages to power and efficiency.

My 1.7 with MS1 and a 36 to one trigger wheel has lots of power and still gets 39 miles to the gallon. This is possible by leaning the the areas of "cruse" and adjusting the timing. These two things are not possible with carbs. and a stock dizzy

I was a proponent for the OP to keep the carbs. also. An EFI retrofit is not an easy task.

Ethan, if you want better fuel economy; loosen your throttle cable so they only open half way. No more WOT runs. I guarantee better fuel economy my young friend.

Hello,

As I have done the conversion using the bitzracing kit, I thought you might want some input.

First, I did the whole conversion for about $2200 all in, and I then sold the carbs/ manifold for about $1000.

Started first time after I finished the install, but, I spent a fair amount of time tuning after that. On the dyno, it made about 5hp more. But, ran much better throughout the range. But, doesn't sound as nice as the carbs when on the throttle. I have a 2.7l with e cams, Euro pistons, and header.

Gas mileage with carbs was about 16 mpg. And, even after several years, I have not checked the MPG after. Really didn't care. I did it, due to the carbs running like crap every few months, and having to clean them. Now, I never have to fuss with the carbs.

-- brett

If you go the bitz route (or modify it for ms3) I have a full CIS from a 2.7 I'm going to sell off. I went back/forth on the CIS/EFI/carbs decision. I'm going carbs, since I don't care how much mpg I get on a fun car.

It may seem trivial to many, but my one remaining hangup on the Bitz kit is that it uses MS1, which is still only able to reliably interface via serial port. MS1 offers probably everything I will ever need to control my motor the way I want it, but laptops with serial ports are becoming scarce. I know that there are serial to USB adapters, but from what I have read, they are often less than reliable (between MS1 and Tuner Studio).

Hello Ken,

Its really not an issue with the serial port. You do have to get the right USB to serial adapter, there are some that do not work. I use my laptop with serial adapter with several varieties of ms with no problems. I am using tunerstudio with ms1, ms2 and microsquirt and not a problem.

To be clear, I ordered the adapter from efianalytics as they had the one that would work.

-- brett

I agree, not all dongles are created equal, a quality one should work w/o issue.

http://www.diyautotune.com/catalog/usb-to-...tudio-p-67.html