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1996 VP 5.7L GM TBI Timing chart help..

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PNWBoater

New member
Hi,

I do not have my manuals with me and I am running into some timing issues..

1996 Volvo Penta 5.7 L GM
TBI
ECM1
Delco EST Distributor

I have the tool to plug into DCL to put timing in base mode.
Start engine> 1000 RPM> switch to base timing mode and
Base timing is set at 8BTC > then back to running mode.

But I am getting 40* BTDC above 3000 RPM, seems to be way too aggressive.

Anyway, not sure if 8BTDC as initial timing is the right value. Could be the IC module in EST not being right.. Hard to tell if someone would have purchased an automotive IC and installed it on boat at some point..

Anyone would have the Timing graph for a VP 5.7L TBI mid 1990's?

Thank you very much.
 
Hi there,

Well, I have the manual now but it only refers to Base timing value (8* BTDC), nothing about total advance..:confused:

Anyway, If someone with a 5.7L TBI Volvo penta reads this and has a chance to check their timing, it would be awesome if they could post your total timing advance at 3000 Rpm.

Thank you.

Fred
 
You won't find a traditional timing curve as the ECU control the advance function. Best case you might find the timing plot showing the range of each phase of the timing extent as a function of RPM...

It is very possible you can see 40 deg of advance at 3000 RPM under No-Load conditions. As long as the ECU is "happy", it should mitigate any excess timing issues under load.
 
makomark said:
You won't find a traditional timing curve as the ECU control the advance function. Best case you might find the timing plot showing the range of each phase of the timing extent as a function of RPM...

It is very possible you can see 40 deg of advance at 3000 RPM under No-Load conditions. As long as the ECU is "happy", it should mitigate any excess timing issues under load.
Click to expand...


Oh ok, didn't know that the load would have such an effect on the advance. Thanks a lot. I will check it under load just out of curiosity. And will post back.

PS: would it be preferable to set the base timing under-load as well?


Thank you again.
 
not really...when you use the timing shunt, you disable the ECU control of the timing, in essence locking it....so there isn't any variation....in other words, there's no benefit from setting the initial timing under load because the load won't have any impact.

if you check the timing under load, don't be surprised that it varies rapidly and across a wide range...
 
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Mark is sorta right. The ECU doesn't control spark advance, it's the module on the distributor that controls timing. These are preset within the ignition module, so you need to have the correct module for the engine. There's no adjustment other than base timing.
 
o2batsea said:
Mark is sorta right. The ECU doesn't control spark advance, it's the module on the distributor that controls timing. These are preset within the ignition module, so you need to have the correct module for the engine. There's no adjustment other than base timing.
Click to expand...

That makes sense, from what I read on the volvo Ignition and TBI manual as well as some GM material it seems that the computer has it's own algorithm using temp, TPS, rpm, knock sensor and MAP to send a signal to the IC module and uses the pre-loaded ignition advance curve of the IC module to control spark.

This is why, when I saw the 40* advance at 300RPM (and above) I was wondering if that was normal or if the previous owner had replaced the IC module with an automotive part (different advance curve).

Unfortunately the volvo manual only talks about the base timing value and nothing at all about total advance.
However, most of the other (non-TBI or MPI) motors discussed in the manual have a max total advance of 32*. I'll check under load if the 40* I am seeing in driveway changes.

Thank you everybody for your replies.
 
I think you will find the ECU drives the ignition timing once the engine starts...the module within the distributor in essence becomes by-passed...and the ECU does have the algorithm (GM used to call is best average timing or something similar) for spark timing adjustment as described.

And you can change it, but that requires a change of the code in the ECU...
 
makomark said:
I think you will find the ECU drives the ignition timing once the engine starts...the module within the distributor in essence becomes by-passed...and the ECU does have the algorithm (GM used to call is best average timing or something similar) for spark timing adjustment as described.

And you can change it, but that requires a change of the code in the ECU...
Click to expand...



Thanks.

Quick update:

I have a friend with the same motor (not working), I swapped the IC module and computer as well and ended up with the exact same result.
I did setup the base timing under load at 8* BTDC. In normal mode, the computer kept 8* BTDC at idle and the max advance was at 36* BTDC.
Reducing the base timing ( I tested with 4* BTDC base timing) didn't affect the total advance.

So here it is, seems like the computer is in charge of the timing no matter what base timing is. I guess the base timing is set for the start cycle til 200/400 rpm and also in such way that if computer fails you ll be able to get back home in crawl mode..

Thank you everyone.
 
I guess I should clarify. This might help show what we are talking about. As you see, the ignition module picks up timing signal from the spinning diz via the little coil inside the cap. This signal is sent to ECU (4 way plug) which then sends weak voltage pulses to the coil (2 way plug) which amplifies the voltage and sends it to the distributor rotor and cap and on to the plugs. I believe this is a wasted spark type ignition. It has no adjustment other than where you set it in base mode.

http://imaworkinprogress.com/images/ignition_schematic.jpg
 
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PNWBoater said:
... So here it is, seems like the computer is in charge of the timing no matter what base timing is. I guess the base timing is set for the start cycle til 200/400 rpm and also in such way that if computer fails you ll be able to get back home in crawl mode...
Click to expand...

That's it...and if you search around on the web, you can find a MEFI-1/2 manual and it will explain the ignition control and interactions in detail...
 
Not sure if this will help or fuel the debate but this is the timing advance for a tbi bigblock.You will have to add base timing to the numbers.At 2800 and light load it is at 41 total.
03-28-2011 11:52 AM Timing curve.JPG
 
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