ditching heater what about MFI
 

anyone has been stripping the heater stuff out of an 72 MFI car?

first i want to get ridd of my heater stuff since i only drive during summer. first the hoses , block off plates, flapper box and blower motor...

eventually remove the heat exchangers and use simple exhaust headers.

my question is : i've heard that the MFI system is somehow connected to the heat exchangers, and it somehow uses this to regulate cold/hot running...but i haven't got a clue how this works, and how it will affect my engines operation when i perform the above work

will my engine work different if i just disconnect the heater hoses?
do i need to do something on the mfi?
i'm not modding for racing or anything, i'm just looking to simplify the car to just what i need it to do...

is there someone around who knows the low down on this?

thx,
Stijn

There WAS someone around. . . Roland Kunz. . .

In a very old thread, Roland described, in his ininmitable way, the various ways the factory got around no heat exchangers.

As the bulb heats up so do the thermostat discs, adjusting the mixture.

But keep in mind that the early heat exchangers have a header type set up in them, not equal length, but I see no HP increase from going to headers on your car.

i'm not thinking hp increase, more like
less problems with oil drips stinking up when burning on the HE's
easier acces , less cluttered engine bay

mine are currently stainless steel...

There should be a hose that runs from the left side HE up to your MFI pump. That hose pulls air across a thermostat leaning the mixture. I'd pull all the heater stuff and leave the MFI part of the shroud on the HE's

wouldn't there be a way to manually override the mixture

say if i use the handle that normally controls the flapperbox?

there's actually 2 sets of hoses from the HE. there's the large one to your intake that almost nobody has or uses anymore since it's an emmissions device and there's the MFI pump hose which is essential to operation.

Which one are you refering to?

i want to get ridd of all that's not wanted , so it seems i need to stick to the MFI one... or find a workaround...

There's a work around with a light bulb or a cover plate. Check the archives and there should be some good info.

Setting the mixture on MFI for best power is hard enough to do with a dyno or a gunson gastester. Once you get it set right, best not to change it, and certainly, you don't want an adjustable mixture control like an airplane engine!

Do a search on this board. I know of at least one or two guys that have come up with manual ways of adjusting the MFI thermostat.

seems like the only draw back would be to loose the rich mixture when starting cold...i'll try some experimenting on this, maybe there's a way to have a timer switch on my dash to turn on rich mixture when it's starting cold, like a choke switch you see on other cars...

No,no,no the exact opposite, you keep the rich mixture all the time without the thermostat working! The disks in the thermostat housing expand and operate a rod that leans out the mixture after the car warms up.

:confused:

condradictions... that's the only drawback on this BBS :D

guess i'll have to find out the hard way and see what happens

The discs EXPAND to change the mix. The lightbulb thing is novel to say the least. I am with the prior. If the headers you have are SS and equal length there is very little to gain by eliminating the heater. I mean you can lose the control flappers, that would work. But as far as stopping the drips..it will still drip on the header pipe, with or without the exchanger shrouding. The manual lever in the cockpit only operates the throttle linkage and has nothing to do with mixture. The thermostat needs warm air blowing over the discs to expand them. So you need AIR FLOW over them, in my mind making the exchanger shrouding necessary. No heater shroud no way to get air pressure to the back of the exchanger where the warm air pipe connects. good luck. Keep us posted as to what you come up with.

beeing the newbie at techie stuff, i'de say it might take a while
befor i actually start ripping out the guts of my car..

i'll start by removing the right side of the car's heating...less things i can screw up :D


btw noticed you got a 0111 too , greetings dude !

Stijn:

My former 911 had no warm-up circuit. It did have some fuel "foggers" that were piped into the trumpets that were activated by a switch in the cabin.


On cold starts, depressing the fogger switch for about 2 seconds before ignition would allow the engine to start dependably. It probably also served serendipitously as a theft prevention device as it was difficult if not impossible to start the motor if one did not know how to use the switch!

The former owner and builder of the motor had a dial in the cabin where he could richen or lean out the mix - I told him that I (a novice!) did not want that level of control because I would probably frack things up. :) . . . hence the simple fogger switch, cold start approach.

Here's a pick where you can see the "hoseless" modified RS MFI pump:

http://forums.pelicanparts.com/uploa...1067984463.jpg

It can be done!

BR,

Kurt

sweet looking engine Kurt !

looks better than the stock huge air intake box i have

would you know what exactly need to be modified to end up with a foggerswitch setup like you have?

Thanks!

Well, I don't know how "exactly" it was done, but I think I can explain in a general way.

There were six individual, very thin, fuel lines that went into the outside of the intake trumpets - I think they were about half-way from the top and bottom - that sprayed the fuel. The very simple electric button switch was installed under the dash and it somehow caused fuel to be delivered into the above mentioned thin fuel line; how this part was accomplished is the critical piece of the puzzle I don't know.

I am not sure if there was an "extra" pump or if somehow one of the existing pumps was used to spray the fuel. I think someone here much smarter the I can probably backwards engineer such a system.

Good luck!

BR,

Kurt

Well if you do, and the ss exchangers are in good shape, i'll buy them

i plan to keep em in case i want to go stock again, they will look pretty cool hanging on my wall :D

Yea Kurt! Sweet engine compartment! So ...what kind of air filters are those? I have been trying to ditch the stock "elephant" airbox for years. Do tell.

targa:

They're K&Ns - I had never seen the K&N metal tops until I bought that motor.

I like 'em better than the rain shield models and since I live in SoCal I was never too concerned about rain with this motor.

Geeze, all this talk about my former motor is bringing tears to my eyes. http://www.pelicanparts.com/support/smileys/huil.gif

You can find the assembly here:
http://www.knfilters.com/Racing/customcarb.htm

Pic: http://forums.pelicanparts.com/uploa...1067993391.jpg

Best,

Kurt

I'd try to fix the oil leaks before I'd consider messing with removing heat exchangers.

Kurt.

Thanks. I see a change in the future of my engine compartment. Now I did see an MFI in that car right? Was there any special alterations to make them fit or was it right out of the box? part number, link, and all...you da man!

Do a search here on K&N and their filtering properties before dropping the factory filter and housing.

targa:

I think there was some special stuff done to use this type of assembly on the MFI tubes, . . but I did not build this motor and don't know the details.

I think you can use other types of filters with this assembly and not just the K&N type.

Take care,

Kurt

JSDSKI..yea, your right. I have read those posts. Seems K & Ns just strain out the big chunks ...but they look so cool. It was a weak moment. Thanks I'm better now.
You too Kurt.

You are describing the factory cold start set up. A lot of people including myself wire a cockpit switch (momentary contact type is best) to control the cold start solenoid that sits ontop of your fuel filter/distributor housing to have more control over it. The solenoid extends downward producing a small squirt of fuel under pressure into a fuel line split into two for each bank then plumbed along the side of each intake. Kinda crude but does the job.

thought i'de update my own old thread bout the mfi enrichment thingie...

i found a quick and dirty way to do it

1 take off the thermostate from the mfi pump
2 there will be a metal intermediate plate with a round hole in the middle

3 take this plate , lay it on a plastic flat surface

4 put a nut in the hole , one that fits nicely , not to much extra space

5 prepare some JB Weld and put it on the plate so the nut is wel covered, but the threads aren't

6 after the JBweld cured, spray some satin black paint , screw in a long bolt , and prest :



http://forums.pelicanparts.com/uploa...1119270679.jpg

http://forums.pelicanparts.com/uploa...1119270841.jpg

as far as functionality goes , no it's not automatic , and there is no cockpit button or switch.. but the idea to me is , that i should be checking my oil anyway once the car is up and running, so i might as well turn that screw thingie.

it's not something that springs into view , it ain't fluorescant and blends well in with the pumps original look.

Thats how mine is setup. Grady posted this about a year ago with a little drawing. I welded up a mini plate of what you just described. I only run my car in warmer weather, so starting it is not a problem. I actually dont adjust it at all. I have the bolt tighten 1 half turn away from full tight & the car runs *well*. I also run headers, heater block off plates & the loudest muffler I could find :)