Dual sync distributor
 

Does anyone know what rpm these go to in sequential fire using both crank and cam sensor? My car breaks up right before finish line, and in good air like Charlotte this weekend, even earlier in the run because the rpm wanted to climb. Happens right around 6500rpm, little blips here and there. Everything checks out.

Re: Dual sync distributor
 

Sounds like maybe a bit of valve float. IMHO

Re: Dual sync distributor
 

What type of ignition, and what rev limiter chip do you have in it ?

Re: Dual sync distributor
 

while I can't say what rpm they are good for I do know that I was told to use a crank trigger and not use the crank signal from my dual sync....
Rich Nedbal of Fastman Efi said it would not be as accurate as the crank trigger.....


D L Rambo....Stk 1300

Re: Dual sync distributor
 

Crane HI-6 with LX92 coil. That only has one rev limiter and that is set for the starting line launch. The EFI has a high side that I have set at 7500 that I raised to see if that had any impact.

Re: Dual sync distributor
 

Bobby,

When in sequential mode it is not triggered by RPM. It will be active at all times.

Re: Dual sync distributor
 

Hey cooter are you talking about the rev limiter?

Re: Dual sync distributor
 

Bobby, in my opinion the best place to create an ignition signal is at the crank. Using the dist. can induce a fluctuation in the signal due to many factors such as chain or belt whip, plus the gear interface of the cam and dist. gear, compounded if you're also driving the oil pump. looks like you could install a standard crank trigger set up and still use the cam sync input from the dist. for sequential. I wouldn't think the real issue is the actual RPM of the engine but more a result of all the potential lash in the system. Most dist. based cam syncs will vary a degree or two simply due to the lash in the system. Good luck Joe BTW this is all assuming that the dual sync is the actual problem.

Re: Dual sync distributor
 

"Crank trigger systems prohibited unless OEM distributorless ignition." Believe me I want to.

Re: Dual sync distributor
 

Bobby, I've never used one of the dual sync set ups....what type of trigger is being used? Are both sensors the same (Hall effect,or VR type) ? Also your EFI controller does it have datalogging? If so does it indicate unusual engine speeds when the issue arises or a big change in injector pulse width? Or do you have other datalogging (racepak Ect.) that may show an unsteady RPM? I would think that if the crank trigger portion of the unit were acting up it would show up on a datalogger as a drop or spike in engine RPM. Joe

Re: Dual sync distributor
 

Joe,

They are both hall effect sensors in the distributor. Yes the DFI box has datalogging and the RPM curve looks kind of choppy throughout the entire run but I don't know the resolution of the curve. Car sounds strong though up until the mph cones when this miss starts happening. However, yes you see it on the graph, the injector pulse width starts fluctuating at the end, the MAP sensor reads more (or less). In Charlotte it was 97.9kpa the whole run until the traps and it jumps to about 101-102kpa. It is usually 103 on the two step. o2 sensor reads rich at the end as well. I have tried leaning it out/fattening it up but doesn't change anything.

Looking into possible valve float but I have good springs on there because I told Manley I wanted something good up to 7300rpm since I had no clue what I would go through the traps at when I was putting it together. This is only 6500 rpm though..

Re: Dual sync distributor
 

You may be onto it there with the valve float as that would definately effect the Map reading. This is a stick car isn't it? does it act up before the gear change or are you shifting prior to this RPM?

Re: Dual sync distributor
 

Bobby, what lifters are you running ? Mine used to stutter from 1200' to the finish line @ 6500, I put Sherman lifters in , and the stutter disappeared.

Re: Dual sync distributor
 

They are supposed to be Sherman but I got them used on eBay a few years back.

Re: Dual sync distributor
 

Joe it's an auto but I shift in the 5700 rpm range so it never gets that high until the finish line.

Re: Dual sync distributor
 

Most Oem fuel injection equipped vehicles for more than 20 years use a factory crank trigger while " Crank trigger systems prohibited unless Oem distributorless ignition. " this does not apply since the distributor does not initiate the spark in this case.....if this actually applied (and it doesn't) there would be hundreds of illegal crank trigger equipped vehicles on the track.....




D L Rambo....Stk 1300

Re: Dual sync distributor
 

Hey Bobby, do you have a bracket type cam your car, or a dwell type stocker cam? There can be a big disconnect between a random Manley tech that does not know the traits of a stocker cam and lobe profiles. An off the shelf street or bracket cam will not need the spring pressure that one of our cams will require. Maybe talk to the guy who ground your cam, and ask him about the RPM and spring your running.

If your search doesn't turn up anything, maybe try shimming up the valve springs and see if it changes where you have the problem.

Re: Dual sync distributor
 

Very good point Todd. I just went back to cam grinder emails and found one with his spring recommendation based on 7000rpm and it looks like the Manley spring I went with was actually a little stronger and had a slightly higher rate than what was recommended. I think I need to put in-car camera onboard and let you guys listen to it.

Accel recommended the large cap for the dual sync but that wouldn't clear my fuel rail so I had to use small cap. I have read dual sync can have trouble in the 6200-6500 range so I need to research that more. Either that or I got some bogus lifters. Head starting to spin lol. Thanks for your help.

Re: Dual sync distributor
 

Here is a zoomed graph of RPM (red) and MAP (blue) and you can see at the end there are some gaps in the red RPM line and the MAP also senses the blips. I don't think this is valve float but I don't entirely know what that looks like on a graph.

Re: Dual sync distributor
 

Bobby, it's a bit hard for me to see (maybe my screen resolution) but it looks like your MAP starts to really jump just as your RPM trace begins to show gaps. I've never seen a trace where there is an actual gap in it before. However that may be a clue, as an engine misfire will effect the MAP reading, how bout you contact the manufacturer of your data logger and run it by them. This is only my opinion but since the trace has a gap does that indicate there was NO RPM signal recieved? Also does your tach in the car indicate similar issues? Such as jumps or bounces?

Re: Dual sync distributor
 

How's the AFR look up in the RPM range?

Re: Dual sync distributor
 

A few cylinders get rich during that little breakup. Right now I have o2 sensor in number 8 and it reads rich at that high rpm. That plug gets wet with fuel also. Number 1 has a good clean color so leaning the fuel map at high rpm will be dangerous to some cylinders as the breakup seems to only affect certain cylinders and right down at the finish line. I was leaning out number 8 to try and help as well but it still happens.

I just want to figure out how to hook the FAST Dual Sync to the Accel DFI ECU and see if the signal cleans up a bit or even just run a test n tune with a crank trigger to see if that clears it up. Then at least I will know where the problem lies.

Crane cams says this HI6 box and LX92 coil should be fine up to almost 8000 rpm and I'm not even close to that.

Re: Dual sync distributor
 

MAP - Blue
RPM - Red
Injector Duty Cycle - Pink
Pulse Width - Teal

Re: Dual sync distributor
 

Bobby, if you are not running it in Sequential mode, and individually tuning the cylinders, there is no need for a cam sync distributor.

Re: Dual sync distributor
 

I prefer sequential for the extra individual cylinder tuning ability.