Gen7 log...RPM related....

Cool. Did he say it needs to have the positive going part 1st, or the negative going part? Just curious.

So it sounds like your ref pulses are occuring at TDC then? That would imply a predictive spark ecu. I thought that the generic VR input ecu was usually the delayed spark box? Hmm.

EDIT- whoops, when you said Craig I thought you meant a FAST system ;) lol...

TurboTR
 
You can't run without having any offset. No wonder your having problems?It says in the dfi instructions?Or am i confused? Also ski I still don;t like your rpm trace, still looks shaky!
 
Norb...I too was looking at it, but its a million times better than the first log. At least now I can see my shift points etc.

I spoke with lengths on the phone today with Rossler and TCI about my converter, which last night I realized is slipping about 11% on the topend, and stalling much higher than we had planned. So I pulled it out tonight and its getting shipped out tomorrow to have it tightened about 1000RPM.

Rossler looked at the logs as well and said its most likely, what he experiences all the time with his car, and he has videos of it happening in slow motion - the tires actually come up off the ground if the track is bumpy or if the track is loose, the tires will spin even out at the 1000+ ft mark. Last night on several runs it was all over the entire lane going down. back and forth, weaving the entire way down. The track was pretty greasy- so I contributed some of that to the track or perhaps the converter was causing some of it - not fully locking.

I should gain some ET with the converter change - HOPEFULLY! :confused:
 
norbs said:
You can't run without having any offset. No wonder your having problems?It says in the dfi instructions?Or am i confused? Also ski I still don;t like your rpm trace, still looks shaky!


I also agree that will have to put in an offset. I called Craig, when I started doing mine and realized that I could not get the timing to sync up - he walked me through that I should have as an offset - i had to use 20 degrees, and then it was a piece of cake.

If your logs are real jagged like mine, and your timing is coming out of the distributer - you are probably having the same issues I had, with all the "links" in the timing scenerio.

I suggest a crank trigger, they are more compact than I thought they would be. On mine it was a pretty simple install.
 
Yes a crank trigger is good, but the distributor signaling approach should work ~ fine too. Consider the millions of OEM vehicles (like the F*rd TFI system) that used it. I'm glad your problem appears to be solved, but IMO it would be great to figure out what this particular issue is, rather than having everyone have to put on a crank trigger at additional expense. It seems to be an issue with the DFI VR input not being happy (yet?) with the particular dual sync sensor setup. Wish I had a car to scope and look at. Maybe they aren't taking full advantage of the common mode noise rejection that differential signaling provides (the VR sensor is inherently differential and floating wrt ground), and/or the sparks happening inside the distrib are screwing up the signaling with too much noise coupling to the sensor signal.

TurboTR
 
Turbort,

I agree the crank trigger is the last ditch effort - but in my case I replaced everything possible in my ignition makeup, short of going into the motor, and nothing helped it. Even despite the motor being just put together last year, there still had to be slop in everything just enough to cause the problem. Craig when I spoke with him said that this is NOT at all uncommon, and actually more common than people care to know. I think his figures were 99% of all cars making good power see (actually don't see it cause of the lack of logging capabilities) this happening.

I was given some good advice long ago by a fella that I use everyday and had given me the opportunity to develope some terrific ideas at work and in my racing.

"Don't try to control things that you will never control. If you can bypass the actually problem at hand, and make it work another way, then do it."

Its sorta the thinking outside the box theory.

But at any rate, I do understand that all other possibilities need to be exhausted and he should explore those first, like I did with changing the ignition components first.

I would bet that Craig might be able to offer some insight into what the problem might be he is seeing. Try giving them a call at the number earlier in the post. They are not easy to reach all the time, but very helpful when you do get them on the phone! :cool:
 
Ski, about your tire spin - Eric Rankin once told me that when he put the big wing on his Regal that he lost several mph, gained several tenths, and his slicks started lasting twice as many runs. I think the wing got him from very low 9's to high 8's and the slicks lasted about 30 passes instead of 15. The tire life really surprised him. He had no idea how much he was still spinning at the big end.
 
ijames said:
Ski, about your tire spin - Eric Rankin once told me that when he put the big wing on his Regal that he lost several mph, gained several tenths, and his slicks started lasting twice as many runs. I think the wing got him from very low 9's to high 8's and the slicks lasted about 30 passes instead of 15. The tire life really surprised him. He had no idea how much he was still spinning at the big end.

I believe it, TOP FUEL draster use that wing as in integral part of keeping traction. You can generate a LOT of downward force with a wing.

My one buddy that is always a few hundredths quicker than me, with the same basic combo, says my wing is slowing me down. :D It was on the car when I bought it, and just never took the time to take it off to see if it does make a difference. ANd its intent was more for appearance than functionality - being the car was stock when I bought it. Suppose someday I will give it a try. Its not that hard to remove.

But I do believe that you get tire slippage as your moving down the track. I have watched my father drive my car down the strip and you can see VERY distinct tire marks well out past the 300 ft mark where he drove it, so it has to be laying down some tread, as a result of spin.

Guess the only way to truely know is to have a driveshaft sensor that can be tied to the distance you traveled to know if you have extra turns. I know they have systems like that out on the market. Rossler mentioned that is the only way you know for sure if you have a dead hook and no wasted energy.
 
Hey that's fine, maybe Craig will chime in. FWIW I haven't seen this on any of the distributor signaled cars I've worked on.

TurboTR
 
why do you need crank index offset?.........that is only to fudge the timing if you cant get it to match mechanically mine is set to zero cause when i have a timing light on the motor and i force the gen 7 to 30 degrees of timing then verify it with the light it says 30 degrees.
 
this is the info for checking the distributor i got


With all connections in place, hook the scope up to the white wire on the crank connector from the distributor. When you start the truck, you should see a square wave coming out of the distributor that goes from 0 to 12 volts. It should basically be an even 50% duty cycle signal. If you start to see the signal edges getting very rough or dropping away at the same time the truck starts breaking up, that would indicate a likely problem with the distributor and we can take it from there.
 
Hmm, interesting. I didn't realize this was a Hall effect sensor; thought it was VR(!) That changes things :) Unless you are looking at some other sort of output than the crank signal itself (dunno). What is the make and model number (etc) of your distrib?

If it is Hall effect then plain old noise coupling would probably be the #1 suspect at this point. With shielding and close attention to the grounding scheme among the possible fixes.

TurboTR
 
the dist is an acccel dual sync hall effect setup. the sheilded wires are connected along with all other grounds in the truck to the negitive battery cable so as not to have any ground loops or other issues
 
Well in general a cable shield drain wire should be connected at the signal source point, on one side of the cable only. This implies that the shield be connected at the sensor inside the distributor. The shield should not be used as the signal return. But the ins and outs of cable shielding has alot of black magic and "it depends on ...", and quickly gets way beyond the scope of this forum :)

Metal foil shielding can do wonders for voltage field shielding, but does ~ squat for magnetic fields. Something to keep in mind when routing the cable :)

When I converted a Nissan application optical distrib to a FAST app, I ran the crank signal out inside shielded cable, and grounded the shield drain at the distrib body, per above. The oem routing was also inside shielded cabling if I recall the wiring diagram; but unfortunately I don't remember where the oem shield was connected. But FWIW it never showed any problems when running. Maybe it was the right way, who knows. I also like to pull the signal up as high as I reasonably can to give a bit of extra margin.

How yours should be connected is hard to guesstimate w/o knowing all the details :)

TurboTR
 
I am just going by the instructions in the Manual, the crank sensor offset is recomended to be 5-10 degrees. You maybe ok if everything reads right. It maybe as a safety factor not to run the engine at 0 degrees, as the igntion angle can't be made less than the offset degrees, even though you can change it on the screen.
 
ok, so the way i was told to use that was if you could not get it right you could use the crank offset. i know it wont go negitive (cause i tried) but i just messed with it till we got it right.
 
So can someone with a VR sensor equipped sync distributor check something out? Visually inspect and/or probe the two VR sensor wires of the crank sensor with an ohmeter and see if it is connected to the distributor housing or ground. Would expect it to be floating wrt ground, but ya never know...

TurboTR
 
Top