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Vaccum Advance? Get out of here, How To

Im sure that this had done before but if anyone wants a "How To" im willing to make one.

The idea is to get rid of the vaccum pods on the dizzy and run full advance at all times to create better fuel economy and better power through acceleration. All that you have to do is take the dizzy apart, remove the springs that return the advance, remove the pod arms, then tack weld the dizzy at full advance. It cut my quartermile times by almost 2 seconds in my honda and it gave me almost 5 miles more per gallon.

You can also just take the springs off and put lighter ones in so that you get full advance in lower rpms/lower vaccum. That or bigger weights on the rotating part.

Lead the way, always looking for a good innovative mod.

LOL its a the oldest trick in the book, aparently ppl have been doing it to muscle cars and mechanical/vaccum actuated dizzys for a long time. I just didnt know if anyways tryed it on our cars. Its so simple. Il have some updates tomorow night.

Yeah i think Peejay has spoken about this mod, I just haven't done it yet...

Quote:

Originally Posted by chedda_j

I think you are confused. The vacuum advance is for better economy at part throttle. At WOT, the vacuum advance does nothing, since there is no vacuum. The mechanical advance is there for high RPM, since the ignition must happen earlier to time the Peak Pressure Pulse (PPP) to the point of highest mechanical advantage over the crank. Instead of locking it, which is a compromise, you can simply time the engine at full mechanical advance (past 4K RPM). After that point, it's basically locked. Some people like to defeat the mechanical advance, but I can see no reason to do so on a street car...I've never seen the mechanical advance fail. All it accomplishes is to over-advance the timing at low RPM, which is bad for the bearings in addition to robbing you of power at those speeds.

If you want more advanced timing at WOT at high RPMs, you don't need to defeat the mechanical or vacuum advance to get it; just set the timing at FMA and be done with it.

Then why has there been ppl doing it for 30 years with big V8's. Why do they sell kits at lordco and nappa for dizzy's that give you bigger weights and lighter springs? Im not sold buddy. I know it sounds like what you are saying is whats right, but i know for a fact that i got better milage and low end hp with my crx with this mod.

Quote:

Originally Posted by chedda_j

Distributors have a long and troubled history...particularly American distributors in the muscle car era, when they were running MegaCompression engines (e.g. 14:1) on pump gas. Defeating an *unrealiable* system can be a reasonable compromise, no matter how good it is when it does work. But Mazda distributors are bulletproof. They never wear out or break. We are also not asking a lot from them. And, bigger weights and lighter springs you describe is *recurving* the distributor timing; not defeating the advance mechanism. In real racing, we get rid of that stuff only because it's NEVER used. On the street, you might as well take advantage of it.

What you experienced with your Honda is probably the effect of having too little timing to begin with and by messing with the advance, you had a lucky outcome; you advanced the timing and it payed off. You could just as easily have timed it properly at FMA and seen the same benefit.

Ignition timing is the single most important thing to getting the best performance from an engine. The PPP must happen at the point of best mechanical advantage over the crank to maximize torque (torque at any given RPM = horsepower). If the PPP comes to early (advanced), you are punishing the bearings and not creating power. If the PPP comes too late (retarded), it's like bicyling down a hill in too low of a gear and your feet can't catch up with the pedals. EGTs go though the roof. The flamefront is pretty consistent in speed, so the faster the engine RPM, the earlier the combustion must begin. It takes time to create pressure. The distributor is very much like a carburettor. It is just trying to use mechanical forces to achieve something like what the engine actually wants, but it is never exact. The complexity of both is a testiment to engineering trying to overcome very real challenges. Electronic variants of both simply take that effort one step further towards perfection.

The guys running turbos on their distributor-equipped cars are locking the mechanical advance as a kind of boost retard (boots coinciding with higher RPMs). It's a hack, but like most hacks it has some real benefit or they would not do it.

Anyway, it's your life and your car, so do what you want.

Quote:

Originally Posted by chedda_j

You are confused. There are two seperate advance mechanisms in the dizzy, vacuum and mechanical.

Disabling the vacuum advance is a simple as disconnecting the vacuum hoses from the pots. Vacuum advance is for idle and light throttle only and has no effect on the timing at WOT. Which is why a lot of people disconnect it.

Mechanical advance on the other hand incorporates springs and weights that advance the timing with the rpm. Some people choose to lock the mechanical advance at a fixed setting or you can alter the curve by using different springs or weights. It's mainly beneficial on turbo engines as it allows more timing while off boost.

Weights and Springs = your MECHANICAL advance
The vacuum pots on the side = your vacuum advance.

By changing springs/weights, or tack-welding, you're not changing the vacuum advance at all, you're changing mechanical advance.

The turbo guys do this so that they can just time the dizzy to a certain timing and not have to worry about it changing (because unexpected advance/retarding is bad for turbo setup). They leave the vacuum pots open to the air so that they're not causing any vac advance, and they remove the springs and tackweld the weights so that there's no mechanical advance.

Then they time the car to the degree they want it, and go.

This will definitely not help with your fuel consumption. The advance systems were put on the stock car to improve fuel economy and emissions mostly (power was marginally affected). It will be a more *reliable* system, since your timing will not change. It's good for guys running boost, but stock cars should retain both systems as they are.

Jon

Alright well thanks for clearing things up on the rx7, thats why i was asking if ppl do it on these cars. I know tonnes of ppl that do this on RPR to their first gen crx's. Advance the timing so it locks, the idle sucks but the car runs better overall, more power ect...thanks. I wont fuck with shit.

Quote:

Originally Posted by chedda_j

There is power to be made by advancing the ignition timing. It's just that you had vacuum advance confused with mechanical advance.

you can do a write up on it if you want there are ppl that sell the dizzy's already done.. so if you wanted to inforum ppl how to do it im sure no1 is going to give you a thumbs down for sharing info...lol i know how to do it but i hate typing

I might still do a write up. Maybe on a spare dizzy, i dont want to fuck mine up if im not going to be running a turbo for a while. Its prety self explanitory, take it apart, remove the springs, and put lighter ones in. How hard is that. Or just advance it and tack weld them two pieces together. Its not very hard at all...common i did it.

can you guys help me out with how to set the timing up this way for my SE like how rotarygod says to do it

Reset timing to 25 degrees total advance witha 10 degree timing split.

edit: and how do you set the timing w/o extra marks on the pully?

Quote:

Originally Posted by rotarygod

If you intend to retain the stock factory fuel injection, don't even think about a bridgeport. The stock air flow meter has a total area for air to flow through of 4 square inches. That is equal to a 2.25" intake pipe. WAY too small. You will absolutely choke the engine. To make matters worse, there is a spring loaded door in the way further hindering airflow. It almost flows enough air to supply a single rotor bridgeport! You want to feed 2 rotors through it? No way!

Also just consider the setup you are planning. If you use a 12A intermediate housing, where are the fuel injectors going to go? Also i assume you are trying to use the large port center plate. Look at the size of the intake runners vs. the stock intake manifold. The manifold runners are about half the size. Don't even think about port matching them. You will lose a ton of air velocity once the air gets to the center housing. This will slow down the intake air and less will actually get in the engine. The center ports are also the wrong ones to bridge if you are only going to bridge 2 of them. You have far too little airflow through the intake manifold for a bridgeport. Actually this is true for any ports. The stock intake system is a huge restriction.

Your combo is a prime example of how bigger is NOT always better. Your proposed setup may actually be even slower than stock! Yes it is possible. What counts in the power department is the total package. It all has to work together properly.

I have a GSL-SE. It is streetported. I ported it myself so I am very familiar with how it was done. The end housing ports are about the same size if not very slightly larger than the stock 2nd gen intake ports. The primaries are a little larger but nothing insane. One very common mistake you see damn near everyone do on this forum is to go hog wild with the porting on the outer housings. Don't ever open both ports up into one large one. You'll kill velocity and make no low end power. Since your stock afm is so restrictive you won't make much about 7000 rpm anyways. Do you want a motor with no low end or top end? My ports are very close to the ones on Mazdatrix's site.

Here are the mods on my SE up to this point. Cone filter. Didn't notice shit. Long primary collected exhaust system. Very nice power upgrade across the whole rpm range. It's the first thing you should do. Underdrive pulleys. Maybe felt something but not enough to really matter. Light aluminum flywheel. Oh yeah this is noticable! MSD direct fire conversion. This is a very nice upgrade as well. It makes the car run really smooth. Starts are better and gas mileage is improved. It sounds like a 2nd gen now. Reset timing to 25 degrees total advance witha 10 degree timing split. Combined with the direct fire conversion, this was noticable. Streetport. Yes the car is faster. All of the other mods up to this point have made a much larger improvement than the porting did though. Is it worthwhile? Yes. Do it last! I have an S5 n/a intake manifold. The 6 port system and the VDI still work. While the afm is still a restriction, the VDI effect on the car improves the top end. The next upgrade for me is a standalone ecu. This should make the biggest difference yet and it isn't uncommon to see 15% gain in power just solely off of the fact that the airflow meter is gone! Then you can also tune it to your combo. All of these things work together very well.

If I were to bridgeport it, I would go no faster. I would be forced to change intake manifolds and ecu's. I would lose drivability and gas mileage. I would not pass inspection. Without a port job, you can get an SE to run mid 14's!

Do everything else first. Trust me on this one. You'll be glad you did. Then save porting for last and even then don't go too crazy. This forum is full of people who insist bigger is better but you never see anyone with a street driven car with bigger dyno numbers than the streetport guys. I wonder why! My car idles at a stock 750, makes good low end power and still gets me 20 mpg in the city. Good enough for me. If I wanted more, I'd turbo it. Why sacrifice drivability for speed when you can have both?

Quote:

Originally Posted by Blake

As hard as it is for me to admit :), I totally agree with what Blake says here and what he's been saying in other posts about timing and locking the ignition. Ideally, there's a different spark time for every RPM/Load condition, like in a computer controlled ignition. Locking the timing may make tuning easier from a users standpoint, but it's far from optimal and far from the best solution for the engine.

There is a write up with pics on how to lock the Mec, Most likely it is in the archive.

if you take off the springs, there is no need to tack weld, as the the weights will be at full advance any time the rotor is turning due to centrifical force.

Quote:

Originally Posted by 3rd and final 7

Wow that was an old post. I've been standalone for over a year now. That was well before the Megasquirt.

Check out this article from Paul Yaw about timing.

http://www.yawpower.com/pultime.html

Quote:

Originally Posted by Dr_Jeff

if you take off the springs, there is no need to tack weld, as the the weights will be at full advance any time the rotor is turning due to centrifical force.

Yeah, no kidding. Pop the distributor apart, CAREFULLY remove the springs (they are easy to ruin and you MAY want to put it back to stock later) and reassemble. Done. If you don't remove the distributor from the engine, you don't even need to reset the timing. (Well, you'll need to re-set the trailing if you don't mark the vacuum pot before removing it)

Ok i have a question, how the hell do you set the trailing and the leading...is there screws..im so lost about how to set the trailing and leading because im not used to this double spark plug thing. How would i mark the vaccum pot before moving it so i dont have to reset it?