Currently running a 12a dizzy on my turboII with a FC leading coil. Fuel is controlled by SDS. Avoiding locking the dizzy. Here is my thinking on useing the above ignition box. Set the leading and trailing timing on the marks. This gives you a 15deg split at idle. At 4000rpm's the leading timing is 25deg +or-2. The trailing is still 15deg behind the leading. Now with the Crane retard box installed the leading timing can be retarded 10deg after 10psi. Now your leading timing is 15 +or-2 and the trailing timing is now 5deg behind the leading spark. Or the timing split can be increased at idle and have the box retard the leading spark more to have a total advance of 10deg and still keep the split at 5deg after 4000rpm's/10psi of boost. Now I adjust my timing at 4000rpm's to what ever I want to run but my idle timing is retarded, sometimes as much as 10deg. Makes tuning at idle a little hard. Make sense? Anyone try this?
chuck

 

So you want it to reduce the split as you go into boost?

Little or no split is not really worth it to me, more risk of detonation.

Why don't you just lock the dizzy anyway?

 

Not really trying to reduce the split but trying to limit my total advance after 4000rpm and 10psi. I have had good results with my timing pushing 20-25psi of boost but I think it is on the edge. In San Antonio I did not care if the motor blew but here the car is driven everyday. Only one car per person here on the base. Taking the car to the dyno today. Looking for 425-475rwhp depending how much boost I push.
About locking the dizzy, Idle timing will be 15deg advanced. Not sure if I like that for a everyday driver. May try it though.
Direct, is yous locked? what is your idle rpm? I now live in Officers quarters (wife) and can not have something to loud. Not running the small bridge for this reason and installed a side port with very large exhaust ports. Idles at 900rpm.
chuck

 

you have a SA in Yokota? That is cool as hell. I'm not too sure if this is easy or even the correct way but what if you went and got a 12at dizzy. I heard those actually retard timing when boosted. I'm not too sure if thats true because I've never messed with one but that is what I've heard from couple of different sources.

 

SA's here cost to much, I have a FC, allot cheaper. Trying to find a 12at dizzy but they are very hard to find.
chuck

 

I have a stock and locked FB distributor. Idle RPM is a steady 950 rpm, even with the new street-port.

BTW, I have a 12AT distributor that I could put on, but nobody seems to know the total amount of advance/retard this unit does.

Even with the locked dizzy, it drives great, and is not as sluggish as people made it out to be.

I hope to be in the 450+ range right after I break her in too!

 

hey, can anyone help me find the write-up on how to lock your dizzy? i'm still searching, but if anyone knows where to look then let me know. do i search locked dizzy? hahahahah, i still dont understand it. are you locking it to a total advance? or total retard?

 

Hey chuck did you used to live on Okinawa with a SA?

 

junia
Sure did. Drove the blue one on occasions.
You are?
chuck

 

Willie, I used have a white silvia with the 180sx front end then I got the two tone one with the sr motor. I used to hang out with Jason. He had the black FD then he sold that one and bought Jimmy's FC. Oh and I'm the half Okinawan half black guy if that helps. We went to your place once to take a look at the SA.

I got a 85 pretty much identical to the GT in Japan. Its kinda hard to come up with parts up here in RI.

 

Total advance is a term that means minimum advance so to speak. It is a little backwards but oh well. You can think of it as total retard if it helps you understand, but I've never heard that used before.

 

Talked to a old timer today who plays with n/o. This is what we came up with. MSD 6-plus. Have the box retard the leading timing under boost, activated by a hobbs switch set at 5-8psi. This way I have factory 12a dizzy advance under all condition until a given boost level. To much power is lost with a locked dizzy at 12-15deg. These motors rev so much better with 20-24 deg of advance.

Willie, sent you a pm
chuck

 

so basically, we could get an msd 6a with the btm, and just retard the leading timing? NIIIICE this will be GOBS better than locked dizzy!!! wootumus!

 

This has nothing to do with the turbo setup but, Last week I reconnected the vacuum line for the timing advace I guess I could notice a little difference on the top end when I'm accelerating.

So on the turbo setup you want the timing to advance up to a certain boost level and then start retarding itself?

Replied to the PM Chuck.

 

I had a btm fail on my tII. I was running dual btm's and it happened on the trailing side of things, so i got lucky. I have heard plenty of horror stories with the btm's though. When they work it is a wonderful thing.

-Marques

 

You would need two BTMs.

You don't want Just the leading to retard, and not the trailing, otherwise the engine would run on "trailing" spark only - BAD.

 

ohhhhhh, i see. is this hard to hook up? which msd box would i use? any 6a?

 

Buy the one with it built in .

MSD6BTM

 

It wouldn't run on trailing spark only, but if the leading spark every got retarded beyond the point of the trailing spark (negative split i guess...?) then you could have some problems.

Slightly off topic. Don't some of the 3rd gen guys run 0 degrees Trailing split in the high boost upper rpm band?

Marques

 

Ordering a MSD 6-plus today. Not sure about a Boost Timing Retard box. It retards timing a set amout of degrees for every pound of boost. I want 24deg of advance up to/around 7psi then retard. The 6-plus a switch activated retard setting. I am going to set my timing split at 15deg. Install the box on the leading coil only and retard the leading timing 10deg at/around 7psi. This will give me a 5deg split under boost over my switching level. I will give it a try.
chuck

 

DirectF
Test the 12at dizzy on the bench. Get a deg wheel and put it between the rotor and housing and use shop air to retard the timing. Then take the amount of degs it moved and times it by two. Then also check total advance. My dizzy moved 12-13 deg by hand, then when I installed the dizzy on the car I got 24-25 deg of total advance. Marked the crank pulley, did not use a timing light with the advance adjustments.
chuck