OK...I'm not sure if this belongs in the tuning section or Tech....its all bunched together.........

I have been struggling with my combination since I got it going. Finally after getting the vigilante in the car I got to go to the track...

The results were better than the first time with the stock (bad) converter but still less than expected out of the combo....

13.2 sec at 104.55 MPH

I posted that the best run of the night was done after turning the distributer back (retarding) the base timing from the set 6*. In fact I advanced it, but this is the weird part. When I went out today to check what the timing was at and realized what we had done it really shocked me that no knock counts were seen on any of the runs with the base timing advanced and here is why.

I have been posting and wondering why when I set my base timing at 6* and burn my chips for an advance of around 30-35* in the main spark table I get all kinds of knock counts. With the stock ARAP timing which is pretty high the knock counts are everywere! So I pulled timing out of the chip until I got to 25.3* and the knock counts went away. Up to that point I thought the counts were false, but they disapeared at 25.3*. I should also add that I zeroed out the WOT spark advance tables, so that is not causing the problem.

Well here is why I am confused. When at the track the other night, it was suggested that maybe the timing was still not retarded enough and I should retard it some more. So I figured it was worth a try. That is when we thought we had retarded it, but in our haste getting flagged to the track actually advanced it. Added ~8* more! So with the spark table at 25.3*+8* that is a total of 33.3*

After that... I ran the above time with NO knock and picked up nearly .2sec and 1mph.

Today at my dads we advanced it some more and took a ride...WOW! Its even stronger yet. I can be going 30MPH and break the tire loose with no problem. Still no knock counts at WOT! I figure I am about 36* now at WOT.

Why is my question...would the knock sensor not pick up any counts when the timing is added at the distributer, but go crazy when I add the timing in the spark advance tables.

The same dynamics are going on in the combustion chamber regardless of were the timing is added.

Everything about the car is better now....idle is tons smoother, throttle response is unbelievable, top end pulls extremely hard, takeouts are silly...I just can't come up with an answer.

The only thing I can think of, is the harmonic balancer has spun and the base timing is much less than more/less than I think it is, but that doesn't make sense because I am advancing the timing and not retarding it.

Perhaps someone has experienced this before.....Its freakin driving me nuts...What is anything can you guys think of.

Sorry for asking so many questions about this car, but its driving me bonkers, yet its a great challange to get right.

I should also add, because others were suggesting that I may be running to rich, that my WB02 is running right at 12.6-12.7. Fuel pressure also holds steady through the entire run.

Hope someone can shed some light!

Thanks everyone!

 

Changing the base timing (w/distributor)
will change the relationship of the rotor
to the distributor cap at a specific crank
timing value.

If at-crank timing is 30 deg, the rotor/cap
relationship will be different between 6 deg
base and 10 deg base.

RBob.

 

I don't understand what you are trying to say.....

Why can I achieve 36* of advance by turning the distributer with no knock, but when I advance the timing via the chip I get knock?

 

My previous answer relates to the only mechanical
difference in the distributor/timing system
relative to the changes you made. Rotor tip to
cap terminal plays an important role in ignition
systems. This is the reason manufactuers went
to DIS and now CnP & CoP.

RBob.

 

RBob is exactly right.

There is an air gap in the distributor. The wider that gap, means the spark has to use up more energy crossing that gap, so less is available at the spark plug.

An ignition system has a reserve amount of power since it USUALLY doesn't need to use it all up. WOT is very tough on the ignition system, and if things aren't right, yes a poor spark may at times lead toward detonation.

Remmember too rich and too much timing will allows feel faster then the proper tune. The proper tune involves a stop watch.

Also, to a min degree being off in timing can lead to a small AFR error. Too much timing will make a calibration look slighlty leaner then it is. Too retarded to rich. It's not an issue unless you miss the tune all together. That's why I'm very specific about the ways I refer too in tuning.

 

Fellas.

Thanks for the comments but you are way above my head with your explinations.

I guess I thought the rotor passing by the posts is what caused the spark to be sent to the spark plugs. Perhaps I am wrong? Please explain.

I guess you did bring some things to the for-front like how exactly does the spark get advanced by the ECM?

Still my question is if tuning the ECM to 36* gave me knock, why now can I have it at 36* by mean of the distributer, with no other changes, and have no knock counts?

1+1 doesn't add to 2 in this case? If the engine is starting the combustion cycle at 36* it should have knock in either or both situation.

Someone please explain to my WHY! I'm positive this is why I am not running were I should be.

Unless what you are saying is I moved the rotor further from the post and now the spark has to jump further and its not as potent at the spark plug. hence not burning all the fuel and not causing knock..... please clear up this confusion.... Thanks

 

I gave it a whirl this morning, advanced the timing to 8* results were better off idle reponse, blms dropped to 124 from 126, harder starting and I got some knock retard which is good because now i know everything works okay. I think I might keep it at 8 for now.

 

Does this make sense to anyone?:hail:

 

So too much timing and too much fuel will cover up detonation? Because I've been having a difficult time even getting more than a couple knock counts on my motor and from the looks of it, my car shouldn't even have been running if there wasn't a 40.1 max SA constant!
I do understand the whole timing effects fuel AFR which in turn effects timing which keeps on looping hence the reason why you can't just jump in and focus on one item and not go back and change it. I guess you shouldn't just sit down and tune the VE tables until 128 perfect because a few adjustments with the spark and those BLMs will be all out of wack again....
Does anybody think that the stock OEM coil on my TBI might be hurting my performance?
Bruce, that CNP looks SO cool , makes me want to wait off on the whole 6 speed swap....hmm....if I can find the coils for under $100 I'll do it.

 

At 6K RPM you have 10 msec for one crank revolution. Four sylinders will fire during that time, meaning each cylinder firing allows for 2.5 MSECs for the coil to charge and fire.

You can do one of two things, go CD which the trade is that you get the voltage, but at a limited amperage (short spark), or with CNP you can get both voltage and amperage since you have all the time in the world to charge each coil.

Coils were $35 a pop, but that took some shopping to find.

 

Ski, let me see if I can help a little. If you think about how a vacuum and mech. advance work you will understand that as the spark advance increases it also advances the whole mechanical mech., stator, rotor button everything is advancing. Now when the coil fires the spark jumps the same size gap inside the cap now matter what the advance is. On a computer controlled dist nothing advances mechanically, it's all done in the ecm or some is done in the dist module, just depending on the type that is on the vehicle. So with the ecm controlling the advance the spark now has to jump a larger gap inside the cap from the rotor to the terminal that is firing, ei., the more advance the bigger the gap, the bigger the gap the more power is robbed for the combustion process. So what I think Grumpy and Rbob were saying is that by advancing the dist along with the lower advance in the ecm and still being the same as your original setting before, is that it has a more powerful spark therefore a more complete burn and so on and so forth.

Steve

 

I was kinda think that is what they were conveying, but needed it put into other words for verification.

Here is the scoop on the car now.

I took Ralphs timing table and applied it to what I already had. In addition I unhooked the knock sensor.

OH MY! Hello power! I am running 36.2* when PE is invoked. My blms are now a bit lean, but that is expected. A/F at WOT is 12.2-12.4, a bit rich but I added some fuel for testing. Thought I would be safe, rather than sorry. I can easily fix these items on the next chip.

I tested it on the highway first, and eased into the power while carefully listening for pinging. Nothing at at...After I was pretty sure everything was OK I went to my testing grounds. Came to a stop and reset the computer so I could log the run and record 1/4 mile pass.

Stomped the gas and to my amazement the car did not even move! Its just cat there spinning and ever so slowly lurched forward gaining speed at every second, I hit my shift point and shifted and the tires still spun in second then grabbed. I went through the 1/4 but left up shy of my mark and coasted across the line....The computer returned a new best of 12.4 at 109.86MPH. I was truely elated!

I know the computer is not very accurate, but its still a good reference to use.

The car overall is MUCH more responsive and feels like there is a whole lot more power available. Hopefully this cures my loss of power. I sure think it has, but time will tell.

The car used to stall after hard runs and when put into park at times. Now it idle perfectly.

No codes were set and I am a happy camper. I will lean out the mixture a bit tomorrow and see how it responds.

The next time I go to the track I may take 3-4 chips with different fuel curves and see how each performs.

I really think the knock sensor was the problem....There was no way I could get above 25.3* of timing without tons of knock counts. I have nearly 11 more degrees now and I can definately tell the difference. I was probably only utilizing ~80% of the possible power available.

I will do some plug reading tomorrow too, just to make sure that everything is OK with the tune.

Beach those are very good point to make on the items that usually get overlooked. I am 99% sure they are all correct though. I took my time and paid very close attention to detail. It was either you or Ralph that gave that advise, I just kept repeating it in my head....

Thanks guys and essecially Ralph for sending me the timing table way back. Just wish I would have had the rocks to disconnect the sensor before, but I'm glad in a way I played it safe.

Hopefully now I can join the ranks of the individual running 12's!

Can't wait to hit the track again. It will have to wait though, this weekend I have my two other kids! I will have to do a burnout for Hunter! He's 5 and everytime he sees a vette he says he's going to buy it with his piggy bank money!

Thanks again guys!