Why use a distributor?

[lazaris]

"The point is, my exhaust temps are not out of line from other reported alcohol fuel exhaust temps. And I run a leaner mixture than is customary for blown alcohol engines."

But you still havent tested and compared to know for sure. You may only see a 50* drop compared to gasoline. "Other reported" alcohol EGT's surely vary at least this much from car to car....

"You're forgeting a basic tuning truth here. A person who is tuning a gasoline engine for maximum performance and is monitoring exhaust temps, will do what in the face of rising exhaust temps? Regardless of the type of ignition system."

We were talking about cam overlap and fresh A/F charge being blown into the exh. I'm missing your point here.

"Would it be possible that the reason for less EGT after going to a distributor is actually because of less of the supplied fuel being burned during the normal combustion cycle?"

I dont see how?

[dr_frankenstein]

Originally Posted by BlownV6

I dont know ,but a F1 engine probably uses a $500,000.00 ignition system!!!
Cant afford that!!! MSD rules my little world!!! Mike

Are you supercharged as well? if you dont mind me asking.....

A.j.

[DonWG]

I'll say it again. As far as I can tell, everyone is still comparing a distributor system to the 'STOCK' coil pack system. It's very apparent to me, and it should be to others, that the stock system is lacking if it's true that the primary feed to the coils is restricted by design. That being said, again I will say, that a switch to 'ANY' high performance ignition system, no matter what the 'TYPE' would be a vast improvement over the 'STOCK' system. I hope this is clear by now.

Supplying ample voltage to jump the spark plug gap, current to maintain the intensity and duration of the spark are the key. That has nothing to do with a 'distributor'. A distributor in itself does not add horsepower. Sorry to break the bubble guys.

The only true argument that I can see so far is that a 2 step rev limiter works better with a distributor than you can get to work with a coil pack. What's the difference?

You guys got me curious. I don't use a 2 step rev limiter, though my system has a 3 step soft rev limiter included. I think I'll play with it on the gasoline program and see how it works. What are the effects that everyone is looking for with the distributor 2 step?

[DonWG]

OK. Back to large overlap with the camshaft causing short circuiting into the exhaust system. It's absolutely true that short circuiting of the incoming mixture with large cams occurs. That is how you get the best exhaust gas evacuation from the combustion chamber so that the next a/f charge is less contaminated with exhaust gases from the previous cycle. Very basic four stroke stuff.

The question now being, does that bit of short circuiting mixture burn in the exhaust. I say conditions are not adequate for that small diluted charge to be ignited. I am also certain it doesn't burn as it is traveling past the exhaust valve.

First, lets look at the later. If that small bit of charge happened to ignite from the waste spark and was burning as it went past the exhaust valve, no one would be able to keep exhaust valves in their cars. Other than heat transfer to the cylinder head when the exhaust valve is seated, it also depends a little on that short circuiting to cool the head of the valve before it seats. Now, if that incoming charge had been ignited by the waste spark, what keeps the rest of the incoming charge from continuing to burn? Why does the burn stop when the exhaust valve closes? If we follow the logic of some that the waste spark started the ignition of the incoming charge, why would it stop? Why wouldn't the burn continue past the intake valve into the intake runner?

[DonWG]

I have to say no. And my reasoning is not that difficult to understand. Those that tune with oxygen sensors would have to agree with me. Oxygen sensor readings give a direct picture of what's happening with the oxygen content in the exhaust system.

Have to run for now.

[norbs]

I'm told wastespark makes the wb read incorrect, for what reason I'm not sure. If you have doubts contact duttweiler he can shed on light on the subject, he is just difficult to get a hold of most of the time. I will try and Talk to Jeff Rand, i think he is close to him.

[DonWG]

Originally Posted by norbs

I'm told wastespark makes the wb read incorrect, for what reason I'm not sure. If you have doubts contact duttweiler he can shed on light on the subject, he is just difficult to get a hold of most of the time.

Maybe someone who has better access to Kenny could get an explanation for us. And if the ego reading is off, how much are we talking about?

[BlownV6]

Originally Posted by dr_frankenstein

Are you supercharged as well? if you dont mind me asking.....

A.j.

Yes Im supercharged. I believe that you bought your manifold from me last year. Are you building a dragster with the stage 2 in it??? Send me some pics and info. Maybe start another thread!!! Sorry for Hi-jack!! Mike

[DonWG]

Originally Posted by DonWG

OK. Back to large overlap with the camshaft causing short circuiting into the exhaust system. It's absolutely true that short circuiting of the incoming mixture with large cams occurs. That is how you get the best exhaust gas evacuation from the combustion chamber so that the next a/f charge is less contaminated with exhaust gases from the previous cycle. Very basic four stroke stuff.

Let's look at another angle on this.

We're assuming that with a high overlap cam that the incoming mixture is washing out the combustion chamber and making its way out into the exhaust system. Lets not forget that we're talking about a turbocharged application with exhaust pressure buildup that is commonly at a higher pressure than that of the intake system.

Most people running turbochargers... Excuse me, the vast majority of people running turbochargers, I would guess somewhere around 99.99 percent of them, are not running tuned exhaust systems that would take advantage of exhaust pulse tuning. When running a large overlap camshaft, the chance of obtaining any short circuiting with a turbocharger and exhaust bp is even worse without some effort being made to take advantage of exhaust pulse tuning.

So what happens in that case? The exhaust valve opens. Exhaust pressure in the cylinder is higher than the pressure in the exhaust system, so exhaust exits the cylinder. The piston travels up to help pump the remaining exhaust out. Near TDC the piston slows and the pumping action of the piston slows also. The pressure begins to equalize between the exhaust system and the cylinder. This pressure will most likely be at a higher pressure than that of the intake system with a turbocharged application. No pulse tuning is present at this point to help draw the remaining exhaust out of the cylinder and lower the pressure in the cylinder. The intake valve has already opened by now with the intake runner pressure at a lower value than that in the cylinder and exhaust system. Exhaust flow reverses into the intake runner momentarily until the piston begins to travel downward to start suction into the cylinder. This back flow into the intake runner during overlap is called reversion and is surprisingly present throughout most of the rpm band. Especially if the exhaust system is not tuned to take advantage of pressure pulse tuning.

So at 24 degrees before TDC on the exhaust stroke, the waste spark is lighting off in a mixture of mostly exhaust gases, a little bit of extra gasoline that is left from a rich mixture, since not all of it burned because there was only so many oxygen molecules to go around, and very little, if any oxygen is left because most of the oxygen molecules were able to pair up with the fuel molecules in the fuel rich environment.

[DonWG]

So. If enough stray oxygen molecules did survive the combustion process in the fuel rich environment, and happened to pass by the spark plug when it lit off on the exhaust stroke, what are the chances that a fuel molecule would also be there at the same time? Remember, we're talking about an environment in the cylinder that is mainly spent exhaust gases.

And, for that stray pocket of a/f mixture to light off in the mostly exhaust gases environment, we need a certain ratio pound for pound, fuel to air for it to even have a fighting chance of lighting off. I believe the rich burn limit for gasoline is 6 pounds of air to 1 pound of fuel. What are the chances of that, unless there was a very, very incomplete burn or a misfire. Even then, where's the temperature and pressure to help establish the burn? That's already passed.

[DonWG]

Another way to look at this.

Even the spark at TDC compression stroke has a limit as to how well it can light off a full uncontaminated mixture.

Try retarding the spark lead to a point far after TDC. Lets say 160 degrees past TDC. Some point way out there, but not so far that the exhaust valve has started to open. Lets see someone light that off! And thats not even massively diluted with exhaust gases.

[DonWG]

Again, what is everyone looking for with the 2 step and the distributor?

[Mike Licht]

The stock module will not stay synced when doing a 2 step which is waht guys use for launching the car. The distributor will give more energy than stock and no sync problems when doing a rev limit. An LS1 type coil system would be even better than the distributor.
Mike

[Scott Atk]

Sound good Mike... Why don't you and Bob build one?

[DonWG]

Originally Posted by Mike Licht

The stock module will not stay synced when doing a 2 step which is waht guys use for launching the car. The distributor will give more energy than stock and no sync problems when doing a rev limit. An LS1 type coil system would be even better than the distributor.
Mike

So we're still talking about the stock waste spark system.

What are peoples experience trying to use a 2 step with the FAST system in the waste spark configuration. Does it still lose sync? Doesn't the FAST system have rev control of some sort?

What about the Motec in waste spark configuration? Same story?

[dr_frankenstein]

Originally Posted by BlownV6

Yes Im supercharged. I believe that you bought your manifold from me last year. Are you building a dragster with the stage 2 in it??? Send me some pics and info. Maybe start another thread!!! Sorry for Hi-jack!! Mike

Sweet! Looks like were the odd ones with an Iron Lung. I Sent PM as to not hi-jack anymore.

A.j.

[Mike Licht]

Originally Posted by DonWG

So we're still talking about the stock waste spark system.

What are peoples experience trying to use a 2 step with the FAST system in the waste spark configuration. Does it still lose sync? Doesn't the FAST system have rev control of some sort?

What about the Motec in waste spark configuration? Same story?

I did not say anything about waste spark, but since you brought it up IMO waste spark in and of itself has NO impact on HP. Buck pretty much proved this with the Indy Car program which was wastespark (if there was something better they would have used it, they had the budget). A wastespark system will not stay synced in rev limit (2 step) so a properly designed LS1 coil conversion would need to eliminate WS if it was to include a 2 step. There is about 2 degrees effective timing advance when going to an improved ignition system (distributor oe otherwise) and that is where the power gain comes from.
Mike
Donnie, for what its worth I agree with you for the most part in this thread

Mike