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Discussion Starter · #1 ·
So, has anyone actualy turboed a carbed A-series? I was poking through maximum boost, and it gave me ideas for my next car.
 

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just do a search and there are a couple threads that pop up on this forum
 

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I imagine that is a pretty difficult task. Tuning a carbed turbo must be tedious.
I've never done it personally, but I'd think you'd have to run boost through the float bowls too to pressurize them. Otherwise once the turbo spools up, wouldn't the boost pressure keep the fuel from flowing out of the jets? I'm not sure though, just a thought. I'd like to know more because I'm in the process of gathering parts to do the MJL crank-fired ignition that cygnus x-1 did on his, then eventually I want to turbo mine ('87 DX).... :Rock:
 

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Discussion Starter · #8 ·
MJL crank-fired ignition ? do tell. I am in the process of turboing my car (87si) and i am using a msd btm for timing, is that more effcient?
 

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MJL crank-fired ignition ? do tell. I am in the process of turboing my car (87si) and i am using a msd btm for timing, is that more effcient?
MegaJolt Lite. It's based on the Ford EDIS 4 crank-fired ignition using parts from 91-96 Escorts/Tracers with the 1.9L. You use the trigger wheel from the harmonic balancer, the corresponding sensor, the EDIS 4 module, and the coil pack from the Escort/Tracer with the MegaJolt Lite module and eliminate the distributor. I think cygnus even did a writeup on it. As far as which is more efficient/easier to tune, that I don't know. I've never used the MSD systems or the MegaJolt system before. Hey cygnus, if you're reading this, feel free to chime in and offer your $.02... ;)
 

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MJL is awesome. the single best thing I have done to my car. Cygnus's DX to Si thread is a great start info (although he is using mega squirt)and there is some info on the MJL specifically on my "new engine successes and failures" thread. search and you will find what you need.

hope that helps


Smeado
 

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From what I've read with the Webers, it's not too hard to do. Blow through anyways, you can just make sure that you pressurize the float bowls using the vents, like fullthrottle_man said. Then usually I hear that going up one size on your fuel jets puts you on the safe side of the tune. And blow right through the carbs. Then you get a rising fuel pressure regulator because the fuel pressure needs to stay at 4psi above boost at all times or the boost will push the fuel back up the fuel line...

Also I believe if you suck-through, it's a little more work with piping, but less carb tuning is required. General rules I've read are to keep the intake passages as short as possible, and keep the air-fuel mixture travelling downward (top mount intercooling probably required). Or else you'll get fuel building up on the intake piping and obviously that will cause problems.

I've not done any of this, just a bit I've skimmed from reading. I've got an old Car and Driver with a bunch of Turbo'd cars from the late 70s, including a Turbo 78 or 79 Accord (I couldn't resist).
 

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I asked about this some time back, and this is what I was told...
If you want to do a blow through turbo setup, take notes from those toyota corolla guys running their 1970's round backs with turbocharged 3TC engines.

Yeah, there isn't too much information regarding blow-through weber turbo systems on the internet. I was lucky enough to hook up with a guy in Hawaii that built some fast corolla's. At the time he had a corolla that broke into the 9's with a blow through setup. He was running 30+ lbs of boost through a set of 45 DCOE's.

There is no real trick with boosting a weber setup except for these few key components:

1. Make sure to pressurize the fuel bowl of the carburator. This will ensure that fuel will still flow out of the jets into the intake runner and not the otherway around.

2. Be sure to use plastic floats. Those old brass floats will crush under boost and will take on fuel eventually flooding the carb/engine.

3. You must use a rising rate fuel regulator. It sounds odd to run more than 4 psi of fuel pressure through the carbs but it is needed to compensate for boost pressure.
And fullthrottle_man, sweet to hear you're going EDIS, me too. I already put together my MJL and soon as spring rolls around, cygnus will be helping me out with it. Can't wait :)
 

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MJL crank-fired ignition ? do tell. I am in the process of turboing my car (87si) and i am using a msd btm for timing, is that more effcient?
In the 1990s Ford used an Electronic Distributor-less Ignition System (EDIS) on some of their cars. Because it's a fairly simple and reliable system (and performs well too) it's become popular as a retro fit for older cars. Instead of running a standard distributor from the cam it has an ignition module that senses pulses from a toothed wheel mounted to the crank pulley. Using the crank position it can control ignition timing based on whatever the ECU tells it to do. So some smart people created a standalone controller (the Megajolt) that uses manifold pressure (vacuum) and the tach signal from the EDIS ignition module to tell the ignition module what ignition timing should be. It's essentially an ignition only ECU.

With the Megajolt and associated EDIS parts you have a totally programmable completely electronic ignition system. No more mechanical parts to wear out, no leaky vacuum advance diaphragms, no messing with springs for tuning, no oil leaks around the distributor, it's great. For tuning you plug in a laptop or any computer with a serial port. There is a table of RPM vs MAP that sets the ignition advance for everywhere in the engines operating range. The RPM and MAP values themselves are also programmable so you can tailor them to your particular setup. A boosted engine will have different MAP ranges than an NA setup. A D-series Honda will need higher RPM ranges than a big block V8. The Megajolt will work for all of these. There is also a TPS controlled version if you have a really hot cam or an individual throttle body type intake that has lousy vacuum characteristics.

The other nice thing is that the EDIS parts are common and cheap in junkyards and I think are even still available new from Ford. So you can put together a complete ignition system for relatively cheap. The EDIS parts can be had for under $100. The Megajolt ranges from $75-$160 depending on whether you want a kit or pre-assembled unit. There are some other misc parts needed; like wire, connectors, a plug for the distributor hole, and you need to make up brackets to mount the sensor and other parts; but the biggest hurdle for most people is getting a toothed wheel mounted to their crank pulley. For me it's easy because I have the equipment to do it. So after doing the conversion myself I decided to round up a few extra sets of parts so I could make pulleys for anyone else that wanted to do the conversion. So for $75 I can send you a modified OEM crank pulley with toothed wheel mounted and ready to go. The one catch is that you have to remove the AC belt and compressor to make room for the toothed wheel and crank sensor. If your partially nuts like me and also decide to dump your power steering I can also cut off the PS goove on the pulley if you want. And I have some extra EDIS parts available too if you don't want to bother with junkyard scrounging.

As far as the BTM goes, I don't really know anything about those so I can't say much there. The EDIS/Megajolt system however completely replaces your stock ignition system, so nothing else would be needed. Depending on how much boost you plan to run you may need a different MAP sensor than what comes with the Megajolt. But I'm pretty sure the standard Megajolt is good up to at least 15PSI boost.

Umm, that's about all I can think of for the moment. If there are any other questions feel free to fire away or PM me. And I was about to say sorry for spamming up the thread but actually this would be quite relevant for someone wanting to do a turbo carb setup. And in fact the Megajolt was specifically intended for carburetted engines, boosted or not.


C|
 
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