Remove Motronic intake without engine drop

[porschenut]

....intake plenum, fuel system, the whole nine yards in one piece....while the engine is still in the car....can it be done? I want to be able to swap the whole mess for carbs, and then back to stock again every 2 years in the most efficient manner possible.

[DRACO A5OG]

If it is just the top end, why not?

[sjf911]

I've done it many times (actually, too many times).

[john walker's workshop]

easier than a CIS. take the heat blower, A/C stuff and airflow meter off for fairly easy access to the fasteners.

[rusnak]

I have to know: how will you get the Motronic dme to work with the carbs? And you are keeping the stock cams too?

[James Brown]

The motronic system won't work, the brain box will just be unpluged and bypassed. You just need the fuel pump to work. Stock cams will work fine with carbs. My guess.

[rusnak]

That last bit is what has me wondering why do this at all.

[sjf911]

Motronic controls timing so the distributor/coil control will have to be changed

[James Brown]

timing should still work, just the signals that go to the injectors will do nothing. at least in theory, the flywheel sensor still is hooked up. All this just for carbs, it's a disease!!

[porschenut]

Thanks for the input. I just want to pep the engine up with this project, which includes swapping the HE's for headers into a 2 in, 1 out M&K muffler and switching to carbs for the intake. For spark I may use the stock DME and distributor, or install an Electromotive XDI system. I can't do anything with cams or compression as I need to be able to switch back to stock configuration in order to pass smog every 2 years.

This shouldn't be difficult if all I have to do is swap out intake and exhaust every couple of years, especially if dropping the engine isn't necessary.

I'm looking to improve throttle response, but am also hoping for a few more horsies.

[sjf911]

Originally Posted by James Brown

timing should still work, just the signals that go to the injectors will do nothing. at least in theory, the flywheel sensor still is hooked up. All this just for carbs, it's a disease!!

I believe Motronic uses the MAF signal for load calculation based timing except when at WOT and idle.

[porschenut]

Originally Posted by sjf911

I believe Motronic uses the MAF signal for load calculation based timing except when at WOT and idle.

Yep. I was thinking of using a MAP sensor when the carbs are installed.

[stlrj]

Originally Posted by porschenut

Yep. I was thinking of using a MAP sensor when the carbs are installed.

Think again. MAP and AFM signals are different. If it were that easy, we would all be plugging in a MAP sensor in place of the restrictive AFM.

[porschenut]

Sorry, I meant that I would use a MAP sensor with the Electromotive XDI ignition system, when I have the carbs installed. I don't expect to use the DME for anything at all.

[James Brown]

humm, hard to hook up a map sensor with carbs I would think. Maybe a TPS would work.

[porschenut]

Here's what the Tec-GT installation guide says about the MAP:

"Engine Load = MAP Sensor

As nice as the 60(-2) tooth trigger wheel is for determining engine speed and position, more is necessary to perform ignition and fuel control; namely a load input. While many OEM’s use Mass Airflow (MAF) sensors to determine the airflow (and thus the load) of an engine, Electromotive systems are designed around Manifold Air Pressure (MAP) sensors as the load-determining device. MAP sensors simply plug into the intake manifold of the engine (after the throttle), and are inherently easier to install than MAF sensors since they are not sensitive to vacuum leaks or engine airflow requirements. A 1-Bar MAP sensor is designed for naturally aspirated engines. A 2-Bar sensor is used for turbo/supercharged engines with up to 15psi (about 200kPa absolute) manifold boost. A 3-Bar sensor is good for up to 30psi (300kPa), while a 4-Bar is good for up to 45psi (400kPa). Choose the appropriate sensor for the application, and you are done."

The part I found encouraging is "MAP sensors simply plug into the intake manifold of the engine", although I'm starting to wonder if the PMO carb manifolds have a provision for a MAP sensor, or can be modified for one. More research necessary.

[James Brown]

The can, like my Zeniths, there is one port for each barrel. I ran them into a 7-port manifold to smooth out the cam lumps. That might work well.