Switch to Mag?

[ricardo1967]

Supercat stated that his fuel shutoff closed by itself @300', This overcenter spring will keep the valve from closing and still allow one to pull the cable and close the valve. I machined the first ones 18 years ago and never had the valve close on me.

Thanks Bruce, I had missed Supercat's post. The overcenter spring makes sense to me. Worse than having the fuel shutoff valve closing all the way, is having it going partially closed!

[Supercat]

Bruce what is the cost on the spring arm?
Thanks for the link

[dreracecar]

talk to Spud, he sells them

[Supercat]

Will do.

Spud what is a cost for the spring arm? Let me know. We are using a Hiborn pg 150c pump.

[ricardo1967]

Will do.

Spud what is a cost for the spring arm? Let me know. We are using a Hiborn pg 150c pump.

FIE Fuel Shut-off Over-Center Spring Bracket:

http://fuelinjectionent.com/webstore/product_info.php?products_id=154

[Spud Miller]

 Hi Guys,

 Thanks for covering for me here in the cave...I've been on vacation. Horses for a week instead of horsepower

 The more compression ratio and/or boost (or nitro which is liquid compression ratio), the more spark you need. More spark can be expressed in terms of either more voltage, current or spark duration. Voltage (or electrical potential) is what makes the spark jump the gap. Current is basically the SIZE of the spark. Spark duration is how long the spark lasts. The different brands of mags and coils all have different characteristics and the different characteristics benefit different applications. But that's another post.

 The easiest and very best way to see if you need more ignition power:
 
 Open the plug gaps up to something a bit larger than normal...say .025" or so. Make a few passes and note the ETs and speeds. Now close the gaps down to .015" or so and make a couple of passes like that. Did you gain any power with tighter gaps?

 You're making the ignition work harder with the larger gap and making things much easier with the tight gap. Many times, a racer will see significant improvement with the tight gaps and more ignition power is needed.

 The main issue with the box ignitions is that they use battery voltage...on a drag car without an alternator, it's impossible to suck 8-10 amps out of a battery and have it STAY at 12+ volts. Generally at high RPM, the voltage drops down to 10-11 volts. Remember, most guys have just FLOGGED their battery by starting the car at the line, so it's already in recovery mode and low on voltage before the race even starts.

 With a magneto, the faster you spin it, the more juice it makes...period.

 My own example...years ago I was running a 7AL-3 on an injected methanol SBC (14:1 CR). It twisted to 7400 RPM on each pass and the world was simple and wonderful. Then I started running nitro. At 25% I had a top end miss that I couldn't get rid of no matter what I did. A friend told me I needed a mag and loaned me a Super-Mag III setup. I dropped it in and not only was the top end miss gone, but I shed almost .05 off my ET and picked up almost 3 MPH consistently. SOLD!

 You can still have bells and whistles with a magneto, but they are add-ons, not included in the box like with the 7AL-3 and others. Rev limiters, timing control, tachs, shift lights, etc. are all possible through various means. It really depends on what type of racing you do and what you need for functionality.

 Spud

[slingshot383]

Electronic ignition has more energy at low rpm, where a mag will produce more energy at mid and high rpm.  Also, you don't have to run solid core wires anymore, and ETC makes a box that will give you rpm switches to control starting line rpm, and shift rpm as well as over rev protection.

[Spud Miller]

 

Electronic ignition has more energy at low rpm, where a mag will produce more energy at mid and high rpm.  Also, you don't have to run solid core wires anymore, and ETC makes a box that will give you rpm switches to control starting line rpm, and shift rpm as well as over rev protection.

 To make that statement you'll have to list makes and models because it isn't true across the board. Sure, an MSD 7 box has more total energy than a Vertex or even a Super-Mag III below 3000 RPM.  But a 7AL3 doesn't beat a Super-Mag IV at an idle.

 Most of the boxes deliver multiple sparks at low RPM and it artificially makes the energy look terrific. While the mag makes one spark, the box makes 3 per firing....until 2500 RPM when it drops back to 2 sparks. Then at 3000 RPM, it goes to a single spark just like the mag. When you measure voltage, current and spark duration, the box looks incredible below 2500. Sure...overall combined "energy" is higher, but you're comparing 3 sparks to one.

Do 3 weaker sparks per cycle light the fuel better than one spark that's stronger than each of those 3 individual sparks? I don't know. Driving down the highway, I think multiple is probably a terrific thing. On the racetrack (all above 3000 RPM) the energy of the boxes isn't anything terrific.

Yes, solid core wires are definitely NOT required with a magneto any more. As long as it's 50 ohms per foot or less, you lose VERY little energy and the noise reduction is tremendous. There are some mag shops out there that just absolutely call you an idiot if you tell them you're running suppression core wires. Those guys must still be running cable driven tachs, shifting by feel and have no data loggers. If you want that stuff to work you'll HAVE to run suppression wire.

 Speaking of plug wires...Mallory stopped making their old black, stainless core wire. It's no longer available. We sell a lot of plug wires and I went out in search of a solution. What I found was that Taylor's solid core fit the bill perfectly. They also make a 40 ohm/ft suppression wire and we've quit selling the MSD wires now in favor of that. It seems like there's something we don't like about all the different brands of wire sets out there. So, we bought Taylor wire in BULK and we make our own universal (trim to fit) sets here. Nice boots and terminals, EXTRA LONG wire lengths, extra hardware to make spare coil wires included, solid Hemi sets with MSD Hemi tubes, etc. We finally have it all listed on our webstore now: http://fuelinjectionent.com/webstore/index.php?cPath=22_38

 Spud

[FEDNV]

Thank you Spud for the explanation, always great information on this site.

[slingshot383]

Spud, I know I used the broad brush, but trying to get that through some peoples head that the mag will beat the electronic at High cylinder pressures just doesn't work any other way.  Have a friend that 15 years ago had issues with his digger.  It would fire and sound great in the pits, but wouldn't finish a burnout nor launch without dropping cylinders and sounding like it was on it's last leg.  I asked him what his plug gap was, .030, I told him to tighten it up to .018, and his car cam alive.  He was running a vertex internal coil mag.

[ricardo1967]

Spud, I know I used the broad brush, but trying to get that through some peoples head that the mag will beat the electronic at High cylinder pressures just doesn't work any other way.  Have a friend that 15 years ago had issues with his digger.  It would fire and sound great in the pits, but wouldn't finish a burnout nor launch without dropping cylinders and sounding like it was on it's last leg.  I asked him what his plug gap was, .030, I told him to tighten it up to .018, and his car cam alive.  He was running a vertex internal coil mag.

There's where I get confused... if mag is so capable, why the instructions of using a mag usually includes "tighten the plug gap to ...". That tells me the mag produces lower voltage than conventional ignition. Would it be the case that, despite its lower voltage, it has higher amps (stronger/thicker spark)? For the same resistance, voltage and current are proportional, which makes hard for me to understand the previous question.

I don't have a dog in this fight. I currently run N/A methanol. I'm just trying to learn.

[Spud Miller]

 When the plug gaps get too big with a mag, the spark tries to go elsewhere. It jumps inside the cap, out of a plug wire, through a boot, etc.  You'd have no problem running a big gap with a mag using all new cap, rotor, wires, etc. Electricity wants to jump from one sharp edge to another (rotor, cap terminals, etc.). While everything is sharp and wonderful it will work fine. Once the sharp edges on things wear off, it'll be finding an easier path. Keeping gaps at .018-.020 means things not wearing prematurely and knowing the spark is going to make it to the plug.

 Spud