engnerdan

Has anybody here used a 730/727 for timing control only? I am currently using it but it is not working so well. I want to know if there are any tricks.

My current setup is a ford 351 with a 727 running the S-AUJP code and a Holley 750 (soon to be a 650 spread bore).

Any help would be appreciated.


Thanks,
Dan

91L98Z28

What kinds of problems are you running in to?

JPrevost

The bold is your problem. Running code that pushs the limits of one engine is most likely going to be over the limits of a different engine! Tame down the SA tables of the S-AUJP and start reworking the VE tables because they'll need it. Sometimes it's the little things like incorrectly set base timing or injector size, double check those.

89 Iroc Z

He has a carb, the VE table, injector size, etc won't matter. I think you read his post too fast

engnerdan

The problems I am haveing are as follows

Wont start and run unless the base timing (@ the dizzy) is set to 20* - did this EFI and does it carbed

It cuts out at about 2500-3000 - did this EFI and does it carbed

JPrevost

Well he said the chip wasn't working well so I figured (correctly mind you) that he had troubles getting the fuel correct so he went to carb. I gave him my answer now where is yours?

engnerdan, If you're setting the base timing to 20 just to get it started that right there is why it's not running past 3500rpm. You're probably going WAY advanced with the timing to compensate for a fuel problem. Add a lot of timing and really lean and really rich will run the engine.

Get the base timing set to an acceptable 6-10 degrees. Set that in the bin as your initial timing. Set the "warm" SA bias or just SA bias to 0, save, open the main SA tables and set something reasonable like on the 90-100kpa ramp in the timing from 10-30 degrees by 3200rpm, for low MAP values raise the timing by like 10-15 degrees. Depending on your cam you might only need 20 degrees at idle or 35, every engine is different.

There is an article floating around the interweb about running the 7747 as SA only. Have you read it yet?

91L98Z28

Ok, well lets see here.

First - the basics. You know that you have to unplug a wire in order to set the true base timing at the distributor - correct? If you aren't doing this, you're probably setting a true base timing of around 0* or even retarded.

Second, what kind of cam are you running? most mild cams will start/run at even 6* of timing. more radical cams won't. the 240/248 (at 0.050) solid roller in my 406 won't start with only 6* of timing.

third, when it "cuts out" - have you observed the timing with a dial-back light and/or taped/marked balancer to see what your real world timing actually is?

jprevosts' comment regarding true base timing of 20* + all the timing the ECM throws out could be spot on. You could be well past 45* timing advance at some points, which is the point where the dist starts having problems and you could be throwing sparks to the wrong cylinder(!). not to mention all the other problems of too much advance. what do your plugs look like? any signs of detonation after it cuts out? any audible signs?

another thought - if you unplug the advance wire (the same one mentioned in my first point above), and leave the dist at 20* advance with NO ecm input - will it still cut out? Yes, you'll be down on power running fixed 20* all across the board, but if it still cuts out completely then you've got fueling or timing or some other such problems. It's a good easy test.

JP86SS

iTrader: (1)

Just came across this and it sounds like you are running a V6 memcal in the 730.
A few guys were having cutoff problems when doing burnouts and I believe that was the case.
Double check you indeed have a V8 memcal in there.
There was a note posted by RBob somewhere that he mentioned bending out pin 9 on the memcal "could" make it work like the V8 but you may want to check deeply into that before trying it.

Grumpy

Set every thing you can spark wise to 0, and verify that 0 is actually 0.

Also be sure that the reluctor wires (to the module) are on correctly. If swapped the timing will be off.

engnerdan

Well after some fiddling I some how got the timing down. I am going to switch to a different distributor I think something is up because I can only get 8* or 30* initial timing. All I am running for ignition is the GM ignition amplifier and the modified ford duraspark (mechanical advance welded and vacuum advance bypassed) distributor and a factory GM coil.

engnerdan

So after all the work I have put into this truck to get it running I have one important thing I have learned - CARBERATORS SUCK!

I want my EFI back, but I will have to wait until spring, anyways I re-wrote my timing tables to simulate the basic timing characteristics of the vacuum advance and mechanical advance. So I am going to install the computer again and hope with a little tweaking on the distributor I can get this hunk of junk running.

engnerdan

I made great progress tonight with this project, I re-wrote the timing table to simulate the mechanical and vacuum advance plus the base timing, the best I can. I also un-checked the flags for things like TPS and O2 sensor which are not installed and when I tried starting it ran and would spin up way past the RPM it used to. It backfired out the exhaust once (choke not open 100% at that point) and it seems to fall off in the upper RPM range so I think the carb is now at fault.

I think I am going to try tweaking the tables and such a little more to make sure I am only getting the timing I am aiming for.

87_TA

If you were only reading 8* and 30*, sounds like limp home mode where it adds 22* to whatever you have.

Or was that 20*

Make sure you verify with light that its working now.

engnerdan

Limp home mode is higly unlikely becasue there was no computer in the truck, unless the ignition amp will do that on its own with only power, pick up and coil hooked up to it.

87_TA

Sorry,
Did not realize ECM was not in...

RBob

iTrader: (1)

Yes, the module advances the timing itself. While in limp mode there is no ECM control of the timing.

On a stock setup this can be seen while the bypass connector (also called the EST connector) is open (tan w/black stripe). Observe the timing while slowly increasing the RPM. Somewhere around the 1400-1600 RPM range the timing will suddenly increase by 12-14 degrees (or there-abouts).

RBob.

engnerdan

That explains it, Thanks much. Time to get the timing light back out and turn the idle speed down some more and see if I can hit my desired 10*

87_TA - No problem, your input was helpful.

Grumpy

Ocassionally, I'll take a .bin, and then 0 most of the timing stuff out, ie choke, MAT, IAT, the bias, and the main SA table (or set it to ALL 10d entries.

And, then check the timing, with a timing light.

The only way to make sure you doing what you're think you're doing is some times running a sanity check.

And, you get alot more familiar with all the bias, tables, etc., that deal with SA.

But, that's just me....

engnerdan

Grumpy,
I'll have to try that, I set the main timing tables to the values I want and then I unchecked the flags for everythign I dont have connected. But I think I may have throw a flag or two that I did not check because it started running crappy again. So I have to get the laptop out and check it. I think there are more tables/values I need to adjust for this to work correctly.