simplest MFI system?
 

what is the bare minimum you can use as an MFI system?
ideally without warm-up and microswitch/fuel cut-off systems, or anything else not necessary for go-fast. in buying MFI stuff for my 2.4 engine, as is my nature, I went a little nutty. now I have a STACK of MFI stuff and another couple of 2.4T sets coming, and a pump or two.

http://forums.pelicanparts.com/uploa...1257660060.jpg



I'd like to convert this engine:

http://forums.pelicanparts.com/porsche-911-technical-forum/502996-3-0-dyno-day-pleasant-surprise.html

to MFI. I'm not worried about rough warm-up, or emissions issues. what is the bare minimum I can run for components? simple = good. I'd like to keep headers and the Bursch, and probably run K&N's or screened tall stacks. any thoughts much appreciated. thanks, Don.

The shut-off solenoid is integral to the pump, as is the thermostat. You might as well use them. I noticed much better running with the fuel shut-off on the over-run. Crisper, cleaner, smoother throttle response, more engine braking, and better fuel economy. No popping noises, black soot, or stumbling. I run with a screw for the thermostat enrichment becuase I have headers, works fine here in Southern California. Other than that, there is only the starting fuel squirters which I find make a surprisingly huge effect. I cannot start the car without it, even on warm, nice days.

do you run a hot air hose to the thermostat? any chance of a pic or two? thanks, Don.

On a 72 2.8 MFI twin plug I built some years back I had a block off plate made for the thermostat with a screw through it set to the length of the thermostat pin when hot. I actually put a spring and knob on it so I could easily adjust my AFR externally.

For the primer system I put a button on my dash to use for cold start. Not sure I really needed it. I also had the mechanical throttle lever between the seats so I could step up idle speed if needed.

I kept the fuel cut off but do not think it worked as I had a lot of nice popping on de-accel.

Double check this info as it has been a while.

Second thought.

You might contact Gus and Pacific Fuel Injection or some other builder you like and see if they can set up a pump to work with your set up and cams. I would send them you TQ curve.

There is a cam for the later pumps (RS) and specs for a 3.0 w S cams & 36mm intake ports. When we go custom things can be a bit of a challenge when converting to MFI. If it is a race motor and you do not care about drivability it is not to tough. With your flat TQ curve you could probably just put a 2.4T pump on it, faten it up and get it to run perfictly from 4100 to 5500rpm at WOT. It is if you want it to have manners under 3k rpm and part throttle where a good match comes in.

Don, I run a 2.7 short stroke, MFI, 38mm intake on TB's, with 10.6 comp. GE-60 cams, headers and twin plug. I made the MFI system very simple. No shut-off or warm up thermostat and K&N water shields. I have no cold start fuel squirter's. I use the adapter plate with lever and cable to control the warm up and cold start. I have it adjusted so for cold starts the plunger is all the way out causing the MFI pump to go full rich which gets the engine started in about 2 seconds of cranking. As soon as it starts I adjust my knob a little towards lean and let it warm up. Works perfect. I might not have the best fuel ecomony I could, but that was not on the top of my list. I do not suffer from any popping, stumbling, back fires or black soot. The driveability is without compromise. There is some time consuming MFI tuning to get this all working right.

http://forums.pelicanparts.com/uploa...1257697185.jpg

Here is the pump on my 2.5SS. Similar to Mark's but I also removed the baro cell and plugged the oil fittings (it's filled with Mobil 1)

.... and I love the collection ;)

http://forums.pelicanparts.com/uploa...1153109452.jpg

Don,
Nice MFI stash! You're as bad as I am, during a project. I am now trying to limit myself to three of everything. While searching for MFI parts for my 71E, I ended up with two or three of everything, too...until I found parts I really liked....slippery slope, but a nice one.

Regards,
al

Cool pump!

Last full set of MFI take of parts I bought cost me $20 for the box.

How much should I expect to pay for a good set of core's with injectors, lines, pump, TB's & linkage?

Thx. ;)

2 weeks ago on this site I bought a complete 2.4T MFI setup less the plastic air cleaner and a few TB linkage rods were missing. Paid $1000.

I have headders on my 2.4T MFI so I have no thermostat. It runs rough when cold but when warmed up its a dream. I just use my hand throttle to keep it ideling....start around 2K RPM....then within a few moments I can drop it to 1200 RPM and it idles there just fine. After about 5-10 mins she idles at 900 without issues.

...and considering how quickly they went, I think I underpriced them a little bit. Glad they went to a good home. :)

jbell959:
356RS:

Does someone sell the bracket that replaces the thermostat....both you two have the same looking bracket.....I WANT!

Not to hijack.....

Wow.

No one used to want these at one time. Now they are golden it seems.

Guessing a pump about a grand to have a pump converted to RS specs?

Bought my last RS space cam for under $300. Are they still available?

How much to have the TB's opened up w larger butterfly's and the shafts done?

Have a project in mind. I loved my 2.4T, 2.8RS and 2.4S MFI cars.

Thx.

Darren: I bought mine from Henry at Supertec Performance

Photo as requested :)

http://forums.pelicanparts.com/uploa...1257734059.jpg

I MAY have gone a little overboard, but I figure this stuff is money in the bank, they ain't makin' any more of it. ;)


I bought this set-up on pelican for $1300. 2.4T

http://forums.pelicanparts.com/uploa...1255715248.jpg

and a very nice one from Aase motors, on ebay, for $1500 also 2.4T


http://forums.pelicanparts.com/uploa...1257738837.jpg


http://forums.pelicanparts.com/uploa...1257738855.jpg


http://forums.pelicanparts.com/uploa...1257738875.jpg

Don - I was over at Aase Motors a few weeks ago picking a part up from Allan and he showed me the MFI parts.... you got a very nice setup.

I've managed to collect a bunch of MFI stuff also... every few months I need to sell some stuff so I can walk through the garage - it's a sickness

thanks for the input and pics guys. Mark, that's the kind of system I'm thinking of. Flieger, I like the simplicity of yours too. a cable control for cold start and warm-up is my kind of thinking.

I was bootin' around in my car today. :D:D:D:D:D:D:D:D:D
I'm not sure I want to mess with this engine. it would be a serious dissappointment to convert to MFI and have LESS hp/torque. and it's hard to imagine this engine finding any more than it's got now. the cams are the heart of this thing and changing them might ruin the combo.

I've got a line on a core 3.0 that I think I'll pick up to do the MFI thing on. also will give me a bit more time to gather the bits and pieces and plan things out. I'll be putting an E MFI system on the 2.4 for the green car. that will give me some experience in MFI before doing a custom system.

funny, all this and I've NEVER driven an MFI car.......... yet.:rolleyes:

thanks John. nice to hear. I paid a bit for it but I also considered the source. I felt comfortable with the item as represented. knowing it came from a running car is a big deal, it'll be my 'troubleshooting' pump.

So as much as $1500 for a nice set that may still need the pump serviced.

I assume most are the going to be "T"'s. Pad $300 for my last set of 2.4S stacks & $20 for a full low milage T take off when I converted my 2.8 twin plug years ago.

Are we talking about $2000 to get the pump modified w new space cam, the throtle body's enlarged and the shafts done or is it more than that?

Also have to have the heads modified for the injectors and the cam block added for the drive.

I am interested in doing an MFI on a late 3.0 SC long block w stock cams, the intake ports well worked and opened up to around 36-38mm. HP goal being 240-260 @ the crank w 1.5" headers & full race exhaust.

Help is appreciated.

A complete MFI pump rebuild can cost anywhere from $950 to $1250, some quote even more than that. Including an new RS space cam to the rebuild will add $750 to 800 for the part plus the recalibration. So the pump alone could cost over $2000.

I'm running a late ('83) 3.0 SC longblock based motor on MFI. I started with a '72 T MFI system. The throttle bodies are opened up to 36mm (S spec) and the plastic stacks are bored to match. The 015 pump is dead stock, save for being stripped of the warm up and shutoff solenoids, and being isolated from the engine oil supply (it's capped off and filled with Mobile 1).

I retained the bypass solenoid on the filter console, but deleted the thermal time switch and hard wired it to a push button on the dash. This gives me full manual control over the priming circut. A quick shot of gas will get the car started even on the coldest days around here, with no need to mess with the screw I used to replace the warmup solenoid. I simply pull the floor throttle up and let it warm up a bit at a fast (but very lean...) idle.

The heads have had the intake ports opened up to 38mm, providing a 1mm "reversion ledge" around the base of the 36mm throttle bodies. They have also been drilled and tapped for the MFI injectors and a second spark plug. The CIS injector scallop on the intake ports had to be welded over, as they protruded beyond the base of the throttle bodies.

I've detailed the motor build and MFI tuning elswhere on this forum. In the context of this thread, suffice to say I'm very happy with both the driveability of my minimalist MFI system, and its performance. My first dyno runs, when I had it somewhat crudely tuned, netted about 216 rwhp and 210 ft lbs of torque. The A/F ratio had too much variance accross the rpm band, and the gas milage was too poor for my tastes at that time. I've since spent a good deal of time tuning it with an LM1, finally narrowing the A/F varaince to just about half a point over the rev range. My "butt dyno" senses a very noticeable increase in power, and my wallet likes the measureable increase in milage, from 11-12 mpg to 15-16 mpg.

Sounds like a proper rebuilt and modified MFI will make PMO's look cheap then.

Jeff,

I will search out your thread. It sounds like a good reference point. It sounds familiar.

Did you keep the SC cams?
Did you time them for TQ, HP or split the difference (3.2 spec).
What header size & muffler?

I did the same thing with the primer system as you on mhy 2.8 MFI conversion years ago. Also worked well as did just putting my foot to the floor on start up and pulling it back to about 10% on first sign of life.

I suspect a 3.0 w stock cams that is done right might be able to get close to 260 fwhp. 3.2's with ITB's and the right exhaust have achieved 270fwhp w stock cams & ports. There is one SC stock block build that used a special tuned ITB EFI with resonance chambers that was represented to get 265HP.

I have spent a lot of time playing with MFI in the past including removing space cam, marking it with a felt pin to see where the sensor would ride on it under given conditions, grinding on it, and other such nonsense. I very much like and understand MFI and I guess I could do a roll your own system for less.

I think I could get where I want with 35-36mm intake ports. I believe the 2.4T butterfly's are large enough. Would have to open up the stacks to about 36mm and the bottom of the throttle bodies to 35mm. I mostly want a broad power band from about 5k to 7k that will work well with the stock SC gears. Kind of like a big 2.4E but with a point and a half higher compression.

Might be something here. I got ta dream!

No, I didn't stick with the SC cams. I went with a custom grind from John Dougherty ("Camgrinder" here on Pelican) that he calls his "GT2/102" profile. It's his GT2 ground on 102 degree centers. I think I timed them at 4mm, but I would have to check.

Exhaust consists of SSI's and an M&K sport muffler. I kind of think 1 1/2" or 1 5/8" headers would give more power than the SSI's, but I like my heat. So does my wife...

"S" size stacks, butterflies, and throttle bodies are kind of small for a 3.0 liter as it is. I think the "T" spec stuff would be way too small to breathe well enough to reach your target hp number. Mine, even on the "S" spec induction, makes peak power at only 6,200 rpm and starts to run out of breath past that. Remember, factory RSR's were what, 43 or 44mm? Granted, they ran in a much higher rpm range. I wanted a streetable "torque motor", not some high rpm hand grenade with the pin already pulled. I achieved that with the "S" setup, but I really think it is at about the bottom limit of flow needed to feed a 3.0 liter. I wouldn't go any smaller.

nobody ever said performance was cheap. ;) we're talking about a 70's vintage, racing fuel injection system.

to your last post. with stock cams I don't think you'll ever see the hp numbers you'd like. I just don't see a 3.0 with stock cams making 250 hp. change out the pistons and cams, at least. my 3.0 makes 250 hp on webers and only stock size 34mm intake ports. but the torque is what gets the job done.

don't throw away your torque driveabilty for some big hp number that isn't really useable anyway.

My garage used to look like that - finally got rid of all of the MFI stuff I didn't need.

Just look up Jeff Higgins thread "Open heart surgery" to see what can be done on the cheap for an MFI 3 liter. It is astounding.

Jeff,

Agreed, stacks would have to be close to 36mm like the S stacks, or more. I think the butterfly's in the T,E, and S are the same size. About 38-40mm if I remember right. T&E stacks and ports if I recall correctly are only about 33mm.

haycait911, if your cam makes 250hp thru 34mm ports that is a good referance point. If the ports are on the small size but a longer duration cam can and with overlap can make up for it I would think.

Another data point for me is I talked to an SCCA 914-6 racer running a 2.8 years ago that ran big webers but with only 35mm well profiled ports compaired to most of his compention's 40+mm ports. He had an advantage out of the corners and still made 280+hp through them. Thus, I was thinking it would be better to start with the small port heads and have them worked by someone that understands my goals and keep them at a minimum size.

A couple of nice things about MFI is the timing of the fuel injection, that it gets squirted at about 240psi and the lack of and restriction from things sticking out in the flow of the air like with carbs. This should make for 10 more HP over carbs. If I get the ports just large enough I am not worried about the intake side with SC cams. I suspect there is more issue on the exhaust side staying with 1.5" primaries.

SSI's are good 1.5" headers. The biger issue is what one dose after them. I suspect the wrong muffler can be a 10 to 20 hp cost over the right race set up like a Flowmaster or Phase9's.

I feel confident that one can make close to 250hp with stock SC cams on 93 fuel and keep a wide power band. Compression would be around 9.8. Probably would use a Programable MSD on the igntion side to fit the ignition curve around the MFI's AFR's where lean spots would take less timing and rich spots more. Would have to get everything right.

Again, the main data point I am working from used SC cams and a 1.5" race exhaust with a very special intake and EFI that made 265hp. There are a lot of stock block SC race motors out ther making 240hp already.

Here is a quote on a stock block 3.0 w SC cams & 1.5" primarys that was I belive dynoed at Jerry Woods:

I would think MFI if done right might be able to come in between the 240-265hp referance numbers.

I am really drawn to the small port SC. Again the cams are already very flexable and can make power over a broad range (more like an E cam than an S cam). The stock crank and rods can take a lot of RPM. It already has decent compression for a single plug motor that can be bumped a bit with blueprinting or euro's. And, the small ports flow very well and still leave enought material to alow for some quality porting if needed.

Not an expert on this and still in the concept stage.

Simplest MFI - 901 4 cam engine
 

This is the simplest MFI implementation I can find..

Maybe a 901/21 4 cam ??

No baro cell
No thermostat
No flyweights (speed independant !!)

Fuel delivery just governed by throttle position

http://forums.pelicanparts.com/uploa...1257819447.jpg
(C) unknown

Plastic fitting for MFI Cold start Nozzles
Does anyone know where I can find one of the plastic connectors for the cold start nozzles. Our host says they are not available anymore. I only need one with a T for the center stacks that broke when I replaced the cold start hoses. See link for picture: http://forums.pelicanparts.com/Porsche-911-used-parts-sale-wanted/509743-mfi-parts-wanted.html
Thanks

Any auto parts store will have little plastic tees that will work. They are commonly used on all kinds of vacuum lines and such. Just bring your broken one in to match it up.

The plastic Ts are squirters.. I would think a normal T would have too large of an opening. I'm sure I have one in the garage. I'll check tomorrow.

Oops... I thought you meant the tee in the line where it branches out to the two sets of stacks. Sorry. The one you are looking for is going to be tough...

I have no microswitch for fuel shut-off on my car. I also don't have the electronics console that is usually mounted on the left side of the engine compartment. If I wanted to add the shut-off, would I just need the microswitch (and attach to the existing solenoid) or would I need all the additional electronics too?

someone who knows more than me can chime in here, but, the microswitch just activates the solenoid on the end of the pump. you just need a 12V source to run thru the switch to the solenoid. the solenoid is already grounded. so you need a microswitch and some wire and a couple of spade ends.

So, the rpm transducer is not necessary for this? What is its function? Car runs great without it and without the shut-off solenoid, but I get backfiring, unless I run the mixture a bit richer than optimal (also this seems counter-intuitive - why does running it richer backfire less?).

You need the RPM Transducer. These are often non-functional due to the leads on the transistors inside becoming brittle and snapping off after all the years and heat cycles. If the box rattles, this is likely your problem. I fixed a unit that I bought from a fellow board member to fix my (missing) unit. The 12V goes through the box, to the microswitch, and on to the solenoid.

My problem is more serious than the box rattling - there is no box at all;)

My car has no transducer (the whole console is missing and was never on my car - originally a 73.5 911T with CIS). I was told the racecars never had this feature and since my car is mostly a track car that I wouldn't miss it. Most of the time I don't, but I fear that I'm leaving a little power on the table by running the motor rich to avoid backfires (with nice flames out the exhaust if I run it leaner). Is it worth the effort to add the transducer and microswitch? Any potential harm if I lean out the motor (to the proper level) and increase backfires?