[jseabolt]

Originally Posted by spinn

The 5pin modules should be similar. The factory pin is marked R they vary identification letter. Using a 3M snap on type connector, the wire splice is made without damage to the HEI connector, and attached to a switch that is grounded to the head. Enables my build to run 16-18 degrees inital and then crank for a hot start with a flick of the switch.

The upper left pin (tiny one) is the "R" pin. The thin "R" pin is for a connector that plugs in and goes directly outside the HEI. It went directly to a vacuum switch that apparently was grounded when whatever vacuum condition GM wanted was met, and it pulled the overall timing down by 10 degrees only. Same Mechanical and Vacuum advance, just offset.


Five pin modules were used for:
HEI-EMR (Electronic Module Retard)
HEI-ESC (Electronic Spark Control)
HEI-ESS (Electronic Spark Selection

At least two different 5pins were made. One is set up to retard timing based on a + voltage going to the fifth pin. The other is set up to retard timing based on grounding the fifth pin.

Here is a picture of the one I found at O'Relieys.



Here is yet another 5 pin module:



I believe the tiny pin is marked "R" on this particular module.

So your saying the second module is the one that when grounded retards the timing 10 degrees?

Here's a link I found on these modules, but yet again the question is which module is the one that retards when grounded. These guys don't seem to know either.

http://speedtalk.com/forum/viewtopic.php?f=1&t=24559

Thanks!

[jseabolt]

One more question. Both of these modules are marked L and H. I'm assuming these pins goto the magnetic trigger and the third pin goes to the retard function?

[ap72]

The two fuel tanks isn't that complicated, There are many ways to do it too. Another option is running two fuel rails and have the second set of injectors on its own fuel system, you could then run race fuel and adjust the percentage of race vs regular for any given engine running conditions- that would make the most use of your fuel but also be the most expensive to set up, I've seen simmilar systems set up with E85 so you can fill up both at the pump, you get better mileage out of the regular gas but have E85 for when the boost turns up, a good EFI system can make the transition effortless.

If you go with two tanks size the one for race fuel much smaller than the other as fuel can go stale after sitting a while AND you don't drive at WOT- the race gas will be used much less.

Water injection is a great alternative for moderate boost levels but it has its limits. A dual fuel system can operate far beyond the mechanical capabilities of your engine if properly set up.

[jseabolt]

Originally Posted by ap72

The two fuel tanks isn't that complicated, There are many ways to do it too. Another option is running two fuel rails and have the second set of injectors on its own fuel system, you could then run race fuel and adjust the percentage of race vs regular for any given engine running conditions- that would make the most use of your fuel but also be the most expensive to set up, I've seen simmilar systems set up with E85 so you can fill up both at the pump, you get better mileage out of the regular gas but have E85 for when the boost turns up, a good EFI system can make the transition effortless.

If you go with two tanks size the one for race fuel much smaller than the other as fuel can go stale after sitting a while AND you don't drive at WOT- the race gas will be used much less.

Water injection is a great alternative for moderate boost levels but it has its limits. A dual fuel system can operate far beyond the mechanical capabilities of your engine if properly set up.

Well all I'm interested in doing is retarding the timing 10 degrees under boost which will do the trick. Hooking up five wires sounds allot easier than adding a second fuel tank or extra injectors.

I tried water/alcohol injector with my first turbo project and it worked as long as I was using a water/alcohol mix. Straight water didn't work. Or at least I had no luck with it. It does clean the carbon build up off the pistons.

Once I figured out it was a lean fuel mixture and the alcohol was making up the difference, I removed the unit and sold it.

[spinn]

The second picture looks correct. A wire off the skinny pin went directly to a vacuum switch on the firewall. At a predetermined psi amount the switch grounded the skinny pin. This was the EMR type system. the ESC system like on the Turbos and cadillacs had a computer controlled set mechanical curve, and you werent able to play much with the timing curve. A wiring diagram for the 5 pin application will show what is what.

[jseabolt]

Originally Posted by spinn

The second picture looks correct. A wire off the skinny pin went directly to a vacuum switch on the firewall. At a predetermined psi amount the switch grounded the skinny pin. This was the EMR type system. the ESC system like on the Turbos and cadillacs had a computer controlled set mechanical curve, and you werent able to play much with the timing curve. A wiring diagram for the 5 pin application will show what is what.

I called Advance Auto parts and they are going to order one for me. $36. I used 1980 Olds Toronado V8 as the reference model.

Interesting is this particular module seems to be only used on 1980 and 1981 GM Vehicles according to AC Delco's website.

I'll post a follow up some pics of my setup once it's done. I'm going to use my Fiat 2000 turbo Spider as an initial test vehicle since the magnetic trigger was originally controlled by a 4 pin HEI module from the factory.

The module goes behind the coil in this finned unit. I'm currently using a Jacobs Boostmaster that has long since been discontinued and I'm looking for a cheaper alternative to the MSD, Crane and Megasquirt systems in case this one craps out. But maybe sooner or later.

Thanks for your help and answering my questions.

[jseabolt]

OK. got the module wired up today on my Yugo 1500 turbo. For whatever reason the information I read about trigger polarities on Bosch distributors was wrong. So I reversed the wires and it started right up.

However I was dissapointed that the module only retards the timing 5 degrees, not the 10 degrees I was expecting.

However I did learn something today. The dual port diaphram I had been using from a VW Rabbit was not doing anything! So that explains the lack of advance.

I wired in a pressure switch which grounds the tiny pin under boost. The hose going to this switch also goes to the vacuum advance which I'm taking my vacuum/boost signal from manifold vacuum instead of ported vaccum.

Using a jumper wire at the contacts, I'm showing 5 degrees BTDC at idle and when the switch is open I'm showing something like 20 degrees BTDC at idle.

I test drove the car and it's no longer jerking and carrying on and there is no detonation under boost.

Seems the jerking must have been related to the vacuum advance not working.

Still not sure why I am only getting 5 degrees retard.

[cobalt327]

Originally Posted by jseabolt

Still not sure why I am only getting 5 degrees retard.

If the 10º of retard is in distributor degrees, the crankshaft degrees will be 1/2 of that amount.

[jseabolt]

Originally Posted by cobalt327

If the 10º of retard is in distributor degrees, the crankshaft degrees will be 1/2 of that amount.

Here's some pics of one of my cars. It's a 1987 Yugo with a 1500cc Fiat engine, T25 turbo, blown through a Weber 32 DFTA carb.

http://s222.photobucket.com/albums/d...urbofiat/Yugo/

I spent this weekend wiring in a 5 pin GM HEI control module on my Yugo that is supposed to retard the timing 10 degrees when the small pin adjacent to the pickup connectors is grounded. Turns out that's 10 degrees in cam timing, not crankshaft timing so when measured with my timing light, it's 5 degrees. But still seems to do the job.

This module was used on 1980 and 1981 Pontiac and Oldsmobile V8s. It is
variation of the 4 pin GM HEI modules used on Spiders and Bravas with the Marelli electronic ignition systems but with a retard function to offset detonation under wide open throttle and help the engine start easier on high compression engines. It was wired through a vacuum switch on GM cars but in my application I ran mine through a pressure switch which activates at 1 PSI.

It will also work on Bosch distributors but for whatever reason the polarities have to be reversed in order for it to work. Or someone just posted the wrong information I read on the internet and I ran with it.

On Spiders and 131s it's a drop in replacement. No mods needed to the wiring but requires shaving off a small tab on the finned coil unit otherwise the connector won't clear it because the pins are angled differently.

Now here is the suprise. I pulled the dual diaphram advance module I had been using (the infamous Golf mk1/Rabbit) and discovered it was not advancing or retarding the timing at all! The diaphram will hold vacuum but the arm just won't retract which makes me think the spring inside got twisted or something. So no wonder the car ran like crap.

I put the factory (advance only) module back on and connected it to manifold vacuum (not ported vacuum) that way it appears I'm running 20 degrees BTDC at idle.

The car idles so smooth and no detonation under boost. It has been in the 60s here lately so it's too early to tell how well the car is going to run in
freezing weather but so far I've tried lugging the engine in top gear at 1000 rpms and no bucking or backfiring.

Eventually I'm going to try this on my Spider. If it works I'll remove my Jacobs Boostmaster I have been running to simply things.

Here's some photos:

http://tinyurl.com/89r37us

[TurboS10]

One of the lessons I have learned over time with projects and turbos in particular is that you can spend alot of time, headache, and money trying to do things the cheap way. The BTM will work flawlessly and make the engine work like it should.

Retarding timing does not reduce power if it is done correctly. Rather, it keeps cylinder pressure from spiking to the point of catostrophic levels. With higher cylinder pressure the combustion process is accelerated. With this acceleration it takes less lead time for the timing even and flame propogation. So, a gradual timing retard with boost increase is the one and only way to do it 100% correct.

The other option is to allow the engine to run timing for full boost and allow it to be retarded off boost. This works for a competition only engine that only runs at WOT. I did this on my turbo gas puller.

[jseabolt]

Originally Posted by TurboS10

One of the lessons I have learned over time with projects and turbos in particular is that you can spend alot of time, headache, and money trying to do things the cheap way. The BTM will work flawlessly and make the engine work like it should.

I'm assuming your refering to MSD boost timing master?

I considered this system but MSD says you have to use MSD's main box in conjunction with the retard box. I figured once all was said and done I'd have $700 in the system.

If I was running some major boost, I might consider paying for a system like this but only running 7 lbs of boost on a stock engine I can't justify spending that much.

This bucking condition off cruise returned the other day. I think the Hobbs pressure switch I was using to ground the retard pin was stuck in the closed position. When I got home I noticed my engine was idling lower than normal which leads me to believe the timing was stuck in retard mode.

I pulled this switch from my stash and tested it before hand but it didn't seem to closed under pressure. I took the set screw and spring out and just barely screwed it in. Then it seemed to work.

I've had two of these Hobbs switches either stick open or not work at all on my Fiat Spider. I discovered this one day when my air conditioner stopped working. I had the wire going to the compressor run through one of these switches so it kicks the compressor off under boost.

Smacking it with a wrench would "fix" it for awhile. I finally ran a jumper wire across the terminals to get me to Nashville and back.

I replaced them with a different brand of pressure switch made by a company called Drywer from Omni Controls.

The previous day the car ran fine in the 60s. The next day it was in the mid 40s and pouring down the rain.

This bucking starts to happen when my boost guage shows manifold pressure is between 10" HG and 0. I seem to think at this point the vacuum advance is pretty much closed. I'm using "manifold" vacuum and not "ported" vacuum.

So if the ignition was stuck in the closed position retarding the timing 5 degrees, that would explain why the car started to buck and tries to backfire off cruise.

This engine seems seems super sensitve to ignition timing. If I set the static timing to 5 degrees BTDC it runs and idles like crap. Just advancing the timing to 10 BTDC makes a world of difference in how it runs.

[TurboS10]

I am pretty sure the BTM with integral ignition box is under $400, but I have not looked real recently. I will still stand by my opinion that until you get a progressive, accurate timing control module you will not run at optimal conditions. I am the worlds worst about trying to go cheap and be enginuitive on projects, but this is not a place I would skimp. Timing and fuel control are pivotal for a successful turbo engine experience....and they are still not always successful without alot of work.

[Landshark928]

Sounds like a great way to run a small 150 shot of nitrous with 5* of retard under spray.

How would one hook the module in with a street fire or 6al since they both replace the internal module of the HEI?

Right now I drop timing at the track, but would love to have it wired in with the N2O system activation.

[TurboS10]

Originally Posted by Landshark928

Sounds like a great way to run a small 150 shot of nitrous with 5* of retard under spray.

How would one hook the module in with a street fire or 6al since they both replace the internal module of the HEI?

Right now I drop timing at the track, but would love to have it wired in with the N2O system activation.

You can trigger a 6AL with a stock HEI module. I found a couple, one relavent with the HEI and BTM stand alone module.

http://www.msdignition.com/assets/0/...47d1c59147.JPG

http://www.msdignition.com/forum/showthread.php?t=7911

[jseabolt]

Originally Posted by TurboS10

You can trigger a 6AL with a stock HEI module. I found a couple, one relavent with the HEI and BTM stand alone module.

http://www.msdignition.com/assets/0/...47d1c59147.JPG

http://www.msdignition.com/forum/showthread.php?t=7911

I thought an MSD ignition system replaced the factory control module. I mean the box is big enough to run an aftermarket fuel injection system as well as the ignition. What would be the reason behind running an MSD control box in conjunction with an HEI, Duraspark, Bosch, etc. control module?

Here's an update on my bucking (misfiring?) issue.

Today I pulled the spark plugs and replaced the 100K mile distributor with one
with fewer miles on it.

The spark plugs (~5K miles on them) looked a bit dirty but not fouled. I
beadblasted them, inspected for high speed glazing (found none), check the gap and reinstalled them.

Then I installed the other distributor. I just recently pulled this one from a
parts car with 13,000 miles on it. I had previously degreased this distributor
in kerosene.

I wanted to clean and oil the cam weights but the snap ring was as far as I
got. I couldn't figure out how to get the "star" off without excessive force
and was afraid I might damage it. The shop manual shows nothing holding it on.

Instead I pulled the access plug which exposes the centrifical advance
mechanism and gave it a good lub with 3 in 1 oil. Pulled the felt wick and
loaded it up with oil and so forth until oil was dripping from it.

Popped the distributor in and even connected the retard pin to the control
module. Since last time the car would barely run under boost with it connected.

Today it was in the 50s and dry. Took my dog to the vet which doubled as a 20 mile test drive (my pit bull loves riding in the Yugo!).

No sign of bucking or misfiring whatsoever. Of course this does not mean the
problem was a sticking centrifical advance mechanism. It just means the problem did not occur on this particular day. This misfiring between 10" HG and atmopheric pressure below 3K rpms comes and goes like a case of herpes.

The reason I feel so confident this problem is related to the advance mechanism is years ago I was messing around with the centrifical advance on my Spider.

The shop manual says on Legend Industries turbo Spiders they installed a clip
in place of one of the weight springs to limit the centrifical advance from
something like 12 degrees to 2 degrees. One weight provides 10 degrees advance and the other one provides 2 degrees.

The Spider (which is fuel injected) bucked and drove like crap which is basically how my Yugo was running.

The only thing I can think of as to why the engine seems to run like crap when it's either cold and raining (assuming the centrifical advance is not functioning properly at that time) is the cooler/wetter air reduces the combustion chamber temperature so the spark doesn't have enough balls to properly fire the fuel/air mixture.

Or because of the delay in the compression stroke, the mixture doesn't properly burn. Does that make any sense?

Still wondering about the backfiring. Any ideas on that? What causes backfiring?