Yellow Bullet Forums banner

1 - 14 of 14 Posts

·
Registered
Joined
·
960 Posts
Discussion Starter #1
Time for an indepth technical discussion comparing the use of a Dizzy (Distributer) and the use of DIS (Distributerless Ignition System). I'm posting it here, because I am looking at this from a trubocharged aspect moreso, than just running an engine.

Now, for myself I'm looking at this from an all out performance standpoint, this will be for the Franken60 (3.2L Turbo hybrid) or the FrankenBeast (The next build that I am collecting parts for).

Now my understanding of the DIS system that is used on teh GM 660 is mostly for emmisions, mainly due to the wastespark system that is used.
My understanding also is that waste spark will actually slow the exhaust gases when it fires, which is not something that is desirable with a turbocharged engine, high rate of flow + lots of heat = quickly spooling turbo.
Another benefit of DIS is the dwell and charge times can be LONG, so the spark can be very strong, and last for a long duration of crank degrees.

Benefits for Dizzy, would be no wastespark, which if the theory is correct, then the exhaust gasses would not be slowed any, upon exit from the cylinder, cheaper aftermarket ignition systems, I.E 6AL/6BTM/Digital6, one coil, so cheaper there too.
Drawbacks include custom intake manifold (GenIII heads), which is going to happen anyway, in my quest for mo' powa, so the manifold isn't THAT much of a concern, shorter dwell time, though there can be things dne to change that, and less coil charge time, which may or may not be a factor.

The other thing I have noticed is that most of the faster turbo cars are running a dizzy, some have even been converted from DIS, such as a few late model F-bodies, so there has to be some ultimate reason for that.

What are your thoughts?
 

·
from across the pond...
Joined
·
6,926 Posts
the dizzy for me has too much spark scatter.you can never control something that thrusts it back and forth like you will a crank trigger wheel.Granted if you use(chevys have to) a cam sync in the dizzy hole you will still get it to some to a degree even with DIS. Take at look at what i'm going to use.Features are excellent and they have already had it working on big inch turbo motors.Nelson racing engines build 572ci twin turbo motors and then drove them across america...with 1700hp on pump.
http://www.getfuelinjected.com/products/xdi.html
i'm sure there are others but the features of this one caught my eye.I'm also going to use the TEC3R ECU....
 

·
Registered
Joined
·
960 Posts
Discussion Starter #3
That system looks really good, but I already have the GM version of it. ;)

I really want to get away from the wastespark.

Don't get me wrong I love most of the benifits from DIS, like the longer dwell time and longer charge times, and a stronger spark because of this, but, I see most of the really quick cars using a Dizzy or switching to a dizzy from wastespark DIS.

Just one example, the GM sponsored turbo ECOTech Cavalier. Normally these engines use wastespark DIS, but GM adapted an MSD dizzy to it. Unless the rules stated dizzy only, there has to be a good reason for this. I don't think a rule was the case.
 

·
from across the pond...
Joined
·
6,926 Posts
ok,i see were you're coming from.But,the wasted spark occurs when the piston is at TDC on the exhaust were there is no velocity of exhaust gas and i believe that the spark on the wasted side is not as intense as the compression stroke....i may be wrong here....?
Anyone want to chime in on this one?
 

·
Registered
Joined
·
12 Posts
Thanks for bringing this up Six and Red. I've noticed this in trend to go to "back" to distributors as well. Specifically some people in the Buick community have gone to distributors to gain some extra ponies. Here's one comment from a Buick member;
The waste spark design has issues:

Ken Duttweiler dynoed a twin turbo buick with the DIS then a Dist and the
dist made over 100 more HP. Please keep in mind this was a 1300HP Plus Motor. On Dave Bamford's TSM Motor the Dist was worth around 75HP.
The waste spark also causes issues with the wide band 0/2 readings according to Joe Lubrant.
Note that the the top TSM motors are probably in the 800-900hp range. Heck, I'm getting into this territory and if I can pick up nearly 5-10% by going to a distributor and more tuning, I just might!

I'm going to start digging for some more specifics...
 

·
from across the pond...
Joined
·
6,926 Posts
mmmmmmmmmm,interesting.I'm going to ask some questions. I have the dizzy stuff already so i have the option to keep them.Anyone else got info?
 

·
from across the pond...
Joined
·
6,926 Posts
Just a thought here.....How did they evaluate the changes? Maybe they picked up performance because the dizzy did something else? Retard the timing in a more positive way maybe? remember a distributor retards the motor slightly as the rpm picks up and a DIS stays constant(unless you put a curve into it....) I just don't believe that a dizzy will outperform a DIS system. It's all about accurate spark surely???
 

·
Registered
Joined
·
960 Posts
Discussion Starter #8
Thanks Novachris for the info, I had heard from someone else about Duttweiler picking up the same 100 horses, but there was no further information.

I'm drawing a blank, what is "TSM"?

I don't nessisarly think it's about "accurate spark" so much as good spark, or strong spark.

I have a feeling that that when the DIS coils are measured, especially with the dual output, they are measuring both terminals, so when some spark goes to one cylinder and some spark goes to another, then there is a drop in spark energy is the cylinder under compression. This is my theory, not really based on anything I've read to confirm it just yet.

My initial plan is to have both ignition systems in my truck, and will be able to switch between them in a matter of minutes for testing, both on the dyno and at the track.

Going by feeling, I've driven very similar engines that were equipped with either ignition system and the dizzy equipped engines always sounded and felt a little stronger, a little more crisp. But I haven't driven the SAME engine with both ignition systems yet.
 

·
from across the pond...
Joined
·
6,926 Posts
strong sparks aren't much good it they aren't at the right time.....
We need to get some evaluated evidence on this...Homework for the weekend... :-D
 

·
from across the pond...
Joined
·
6,926 Posts
Intersting article.....http://www.picotech.com/auto/tutorials/primary-vs-secondary.html

DIS has its own drawbacks by having half of the plugs firing with an acceptable negative voltage, while the other half is fired by the less acceptable positive polarity. This will have the effect of pronounced plug wear on the positive fired plugs.
This is all i can find for now...
 

·
Registered
Joined
·
12 Posts
TSM = Turbo street modified. Buick club Grand National and Turbo Regal class that runs production motors only.

I don't know if the test motors were in the same state of tune with Dist and with DIS or if other variables were introduced, skewing the results. Interesting claims, but more info needed.
 

·
Registered
Joined
·
960 Posts
Discussion Starter #14
redvictor, interesting article, and I agree, strong sparks still need good direction, but with some careful tuning, I'm sure the dizzy would be fine, as has been for many years. ;)
 
1 - 14 of 14 Posts
Top