ditching heater what about MFI

[svandamme]

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

[304065]

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.

A other solution is the "Kadach" way. he just removes the complete hose to the exchanger and places a 10 Watt lightbulb from the underside and closes the top with a rubberhat. The bulb is runing via ignition. This was mostly used on raceengines with headers and with changing the lightbulb or using a resistor it could be finetuned to suit the engine.

Kadach was also a factory mechanic and worked mainly on race engines so he had a other problem and a other solution for that.

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

[Rot 911]

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.

[svandamme]

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...

[Tim Walsh]

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

[svandamme]

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

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

[Tim Walsh]

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?

[svandamme]

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...

[Tim Walsh]

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

[304065]

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

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!

[Rot 911]

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.

[svandamme]

The only thing you run into with this set up is you no longer have the pre-heat hose going to the pump to ritchen the mixture at cold-start. As with the heat, cold-start is not a problem that you face. I removed my thermostat and added a plate with a screw in the middle for an externel adjustment. Works nicely.

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...

[Rot 911]

Originally posted by svandamme
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.

[svandamme]

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

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

[targa911S]

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.

[svandamme]

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


btw noticed you got a 0111 too , greetings dude !

[kstar]

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:



It can be done!

BR,

Kurt

[svandamme]

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?

[kstar]

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

[tobluforu]

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