F355 coil-on-plug conversion

Jeff
I got everything hooded up and running . The car idels great and runs great up to about 4500 rpm then it feels like its cutting out , If I keep pushing the gas it picks back up and and runs fine to redline . It only gives me a problem between 4500and 5000 rpm . I checked all my connections and such and iam stumped .
I tried many diffrent switch positions on the dis4 and no luck . I figure it must be something with the dis4 of the switch settings .
What switch settings are you running ?

Thanks

Bill.

 

Jeff
I was rereading your post and came across something that confused me ,
In the frist post you said that plugs 1/4 -2/3-6/7 and 5/8 pair together and in your drawing it shows that plugs 1/3-2/4-5/7 and 5/8 pair together .
I have mine hooked up by the frist order , This seemed to make sense by how the wires were connected to the factory coil packs .
Bill

 

Timing retard, you need to disable it.

 

Do you have yours set for lost spark ? Or cpc ?
I have the rev limit set as high as it will go , and the retard disabaled .
My dis 4 is a bit diffrent than yours i think , it has rotory dials for adjustment .

 

I spoke to msd and they are not much help . Seem to have no idea what I was talking about . All they did say is that it wont work the way i have it set up , i need to use two dis-4 s one channel per coil. They say that the coils only get half the votage when paired together .

 

They also said that it must be alean condition in the car , teh dis-4 could not cause thei condition . weird it worked fine befor it did this , it should have been doing this before.

 

The cops are wired like your drawing ,basicly the negitive is split then goes to each coil , and teh positive goes to all coils .
I have all my wires run in one bundle , would it help to sperate the trigger wires from the rest ?

Bill

 

After a long talk with msd they suggested getting a 8912 tach adapter .
Not sure if this will work or not .

Bill

 

I didnt know thay came in levels .
Ive checked everything 3 or 4 times , I even drove around and went through everyswitch setting . The weird thing is that the max rev limit doesnt work , if I set it for say 6000 rpm it lets me go to redline no problem.
They had no answer for this . All my coils have a 3 ohm resitance , what do yours have ? I dont see how atach adpter would help ,but its worth a try ,I didnt go this far to give up .

 

The msd guys might be exactly right. If you have 2 coils wired in series, each coil only gets 1/2 the voltage....but the diagram a few pages back shows them in parallel, so they should all be geting the same voltage and double the current draw on the DIS....which might be current limitted internally, which brings us back to reduced voltage.

4500-5000 is a little low, I would expect the problem closer to the torque peak where the cylinder pressure is the highest, but if the engine is a bit lean in that region, you could see the problem.

You might try gapping the plugs down to .020" and see what happens. If that fixes the problem, you can either keep the gap there or add a second DIS4

 

I tried gapping the plugs down to .020 , It didnt solve the problem , It appears to make it a little less smooth.
However the neighbors hate me for running up and down the block at 2 in the morning .At this point Iam not sure what eles to try . Should have the tach adpters on Tuesday , Doubt they will help but worth a try .I was thinking of running the dis-4 back into the stock coils to see if its the dis-4 causing the problem, Not sure if I could do that thou .
Thanks for everyones help this far .

 

Put tah tach adapters on today and the problem is solved , Have no idea what it did but it works .I have a weird burble when I rev it up thou , I think it is because i still have the plugs gapped at .020 ,
What would it sound like if it were missing ?

Bill

 

Put the tach adapters on today and the problem is solved , Have no idea what it did but it works .I have a weird burble when I rev it up thou , I think it is because i still have the plugs gapped at .020 ,
What would it sound like if it were missing ?

Bill

 

Regap and let us know. I had a miss in my previous 78 308 GTS with my plugs gapped at .025, but once opened up to .034 the car ran great (Crane Cams XR700 ignition).

 

I can tell you from the little bit of driving I have done ,with all the wires hanging out and the dis 4 zip tied to the frame , it is a major diffrence , I would not go back to the old set up , It really brings out what this car should be , much smoother , better sound .
Now I need to figure out a way to put this in my Porsche turbo , But it has a distrubitor .
I think there is something diffrent between our dis-4s , Mine has the rotory switches and I thing yours has the dip switches so maybe they changed something eles .

 

I am working on this for my 348 with a motronic 2.7. However now with my beautiful transmission explosion the work is put on hold. I have everything laying in my basement at the moment with my wiring harness started but havent got back to it due to the tranny and work just killing me lately.

Glad to hear you two have it working so well and that it is performing beautifully.

 

Sorry for sending you down the wrogn path.....I still have no idea why a tach adapter fixed it.....I'm guessing they were thinking you were just looking at the wrong rpm and that's why they said to use an adapter. strange.