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Topic Review (Newest First)
10-21-2012 06:25 PM
S10BlazerBuilt OK initial has been set to 9* BTDC Then I hook up the ECM back up static idle is 22.5*BTDC. At 3500 RPM, when the mark it at it's peak, it's hittin 35* BTDC. Comp cams doesn't recommend going beyond 8* initial But the builder said 10* was fine and that total time should be 37* BTD. She idles higher (1250) at those settings. Where it's at now, it still idles at 1000 which is a touch high. I'm going to examine the exhaust manifold gaskets to see what's up. (Still getting code 13 after 60MPH is reached)
10-11-2012 08:54 PM
S10BlazerBuilt
Quote:
Originally Posted by LATECH View Post
That is prolly what he thought. I had to re read the first post, and I saw TBI both times. I see a few others here missed that as well.
Whats important is that all the guys here were truly iterested in helping, its all good.
Oh , and you can have more intial timing than factory, as long as the knock sensor circuitry is working, the upper limit will be controlled by the PCM.
Also, did you perform a minimum air rate adjustment after the mods?
You should look at the scanner live data to see where the fuel trims are as well.If it runs lean, you may need to tweek something there.
The only thing I can tell ya, is that it's getting more air and fuel than stock. I have a K&N filter, and high rise injector spacer, AFPR, and running 10% more fuel with Venom injectors, and Edelbrock chip. In other words, if I want real tuning, taking it to someone with a dyno who will be able to tune it and reprogram the prom for the performance I want would be my only option? Right now, I guess all I can do is play with initial time, and HEI distributor advance kit. No pings or smoke, no damage? How much room do I have to play with in this engine as far as initial timing? Any ideas? I really don't wanna drop any more money into, except for a performer intake, and ported polished tbi, and $3250 later I don't wanna damage it. Only got 6K for mileage. The timing advance kit for the distributor would allow for some adjustment for the fuel curve.
How do I do the air rate adjustment?
10-11-2012 06:52 PM
LATECH That is prolly what he thought. I had to re read the first post, and I saw TBI both times. I see a few others here missed that as well.
Whats important is that all the guys here were truly iterested in helping, its all good.
Oh , and you can have more intial timing than factory, as long as the knock sensor circuitry is working, the upper limit will be controlled by the PCM.
Also, did you perform a minimum air rate adjustment after the mods?
You should look at the scanner live data to see where the fuel trims are as well.If it runs lean, you may need to tweek something there.
10-11-2012 06:49 PM
S10BlazerBuilt
Quote:
Originally Posted by LATECH View Post
Thats pretty much it.
So why the heck did the engine builder tell me to take all the steps I mentioned, in regards to setting initial, and then adjusting after the computer was back in control?! lol Damn. I guess maybe he was assuming I was going with a carbuerated setup?
10-11-2012 06:17 PM
LATECH Thats pretty much it.
10-11-2012 06:09 PM
S10BlazerBuilt
Quote:
Originally Posted by LATECH View Post
On a TBI engine there is no advance mechanism. Its all calculated by the PCM
You can add more timing to the base or inital timing to compensate for things like cam duration.Put a vacuum gauge on a manifold source to help you get it to a happy spot between Idle qaulity and speed.
Base timing , and computed timing are basically stored in the PCM algorythms. It does have an "Adaptive strategy" which will allow the timing to run further advanced if it detects octane will support it, and retaard the timing when the low octane fuel causes a knock or pre ignition, which is detected by the knock sensor.
Its a good thing to have the kock sensor hooked up and working. As you drive the vehicle , the PCM will advance the timing through all the rpm ranges, untill it gets to the point it detects a knock, or pre ignition, at which point it will retard the timing until it stops.After that, and a few drive cycles, the adaptive part of the pcm will run the timing based on strategy it has developed through it range of operation.
The amount of timing that the pcm is delivering is based on the initial or base timing being correct.Or factory spec as on the underhood sticker.
If you add some base timing, you will have to add the extra amount to the value of timing advance that you see being displayed on the scanner.
OK. I'm getting the point here, I think. So I can adjust the initial time to fix the idle by advancing it. No worries about any other issue because the ecm will compensate. As long as my engine starts just fine, no hang ups, then I am good. That's assuming I have no piston ping...
10-11-2012 05:13 PM
LATECH
Quote:
Originally Posted by S10BlazerBuilt View Post
Thank you. I was thinking about getting a advanced timing kit for the HEI so I could change the fuel curve to do it's thing in the lower RPMs. I may go that route. I may have to advance it further to lower the idle to where it needs to be. Then adjust for total time. The one thing I am wondering... Doesn't Initial time change in the procedure? I mean, set initial, plug ECM back up, then adjust total @ 3500 RPM... Either way, the distributor is being turned... Does the ECM store the initial time setting and adjust for what it needs at that point?
Also, one other thing bothering me... If Comp recommends 6-8* and it's not working as far as idle goes, will advancing it to where the idle is proper damage anything?
On a TBI engine there is no advance mechanism. Its all calculated by the PCM
You can add more timing to the base or inital timing to compensate for things like cam duration.Put a vacuum gauge on a manifold source to help you get it to a happy spot between Idle qaulity and speed.
Base timing , and computed timing are basically stored in the PCM algorythms. It does have an "Adaptive strategy" which will allow the timing to run further advanced if it detects octane will support it, and retaard the timing when the low octane fuel causes a knock or pre ignition, which is detected by the knock sensor.
Its a good thing to have the kock sensor hooked up and working. As you drive the vehicle , the PCM will advance the timing through all the rpm ranges, untill it gets to the point it detects a knock, or pre ignition, at which point it will retard the timing until it stops.After that, and a few drive cycles, the adaptive part of the pcm will run the timing based on strategy it has developed through it range of operation.
The amount of timing that the pcm is delivering is based on the initial or base timing being correct.Or factory spec as on the underhood sticker.
If you add some base timing, you will have to add the extra amount to the value of timing advance that you see being displayed on the scanner.
10-11-2012 04:50 PM
S10BlazerBuilt
Quote:
Originally Posted by LATECH View Post
Checking the timing on a electronic injected engine is not what you are thinking here. Timing adjusts differently in closed loop than it does in open loop. AND the engine needs to be operating under load to be able to actually read the true timing that is being dialed in to the PCM..
If you have a scanner, it will read the amount of timing being adjusted into the system , just read the live data while driving.
Closed loop conditions are usually
At least 160 degrees engine temp
Gear selector in drive(if automatic)
Active O2 sensor
Then you can throw it into gear, stomp the gas, watch the roadspeed vereses the ignition timing and RPM on the scanner. Then you will be getting closer to what you need to know to start with
Also, if the knock sensor is hooked up and working, if it does get too much timing, the knock sensor will signal the PCM and back the timing off, roughly about 3 degrees each time it happens.Eventually it will"learn" where it needs to be.
The drive method you had for setting the timing in your first post was probably the way to go.
You can dial in more base timing, but the knock sensor should keep the advance curve from going to an excess , which could cause engine damage.
Thank you. I was thinking about getting a advanced timing kit for the HEI so I could change the fuel curve to do it's thing in the lower RPMs. I may go that route. I may have to advance it further to lower the idle to where it needs to be. Then adjust for total time. The one thing I am wondering... Doesn't Initial time change in the procedure? I mean, set initial, plug ECM back up, then adjust total @ 3500 RPM... Either way, the distributor is being turned... Does the ECM store the initial time setting and adjust for what it needs at that point?
Also, one other thing bothering me... If Comp recommends 6-8* and it's not working as far as idle goes, will advancing it to where the idle is proper damage anything?
10-11-2012 04:26 PM
LATECH Checking the timing on a electronic injected engine is not what you are thinking here. Timing adjusts differently in closed loop than it does in open loop. AND the engine needs to be operating under load to be able to actually read the true timing that is being dialed in to the PCM..
If you have a scanner, it will read the amount of timing being adjusted into the system , just read the live data while driving.
Closed loop conditions are usually
At least 160 degrees engine temp
Gear selector in drive(if automatic)
Active O2 sensor
Then you can throw it into gear, stomp the gas, watch the roadspeed vereses the ignition timing and RPM on the scanner. Then you will be getting closer to what you need to know to start with
Also, if the knock sensor is hooked up and working, if it does get too much timing, the knock sensor will signal the PCM and back the timing off, roughly about 3 degrees each time it happens.Eventually it will"learn" where it needs to be.
The drive method you had for setting the timing in your first post was probably the way to go.
You can dial in more base timing, but the knock sensor should keep the advance curve from going to an excess , which could cause engine damage.
10-11-2012 11:38 AM
S10BlazerBuilt OK, so after reading all of the links provided, and doing some research, I'm gonna go over the steps I need to take to set advanced time, and if anyone sees something amiss, please say something. I have a MSD distributor and coil, no vacuum advance on it.

Shooting for 37* BTDC Total Time

Setting the initial at 10* BTDC (unplug the ECM sprague wire to do this)
then, once initial is set, plug the ECM back up to the distributor, here's where things are iffy for me, Put the light to the engine, rev up to 3500 RPM, or until mark moves no longer, then adjust (twisting the distributor) to 37* BTDC, and that's it? Doesn't that change the initial time? Then Static Time is with no load at idle?

Quick question. If my idle is too high, that suggests initial is too low. Do I advance it a bit more to solve that issue? The cam company recommends 6-8* BTDC, but that just ain't cutting it.

I'm installing a MSD timing tape to eliminate the need for an advanced timing light.
10-09-2012 02:00 PM
S10BlazerBuilt
Quote:
Originally Posted by cdminter59 View Post
Read this article then you will understand how to set the initial, total, and with vacuum advance.http://www.crankshaftcoalition.com/w...EI_distributor
Actually, this is a great link! Now I know why it idles at 1250 RPM. But what sucks, is that Comp Cam recommends 6-8 for initial time. However, I have it at 9 and it still idles high. I guess I will have to try between 10-12 initial to see if it cures my high idle.
10-09-2012 01:21 PM
S10BlazerBuilt
Quote:
Originally Posted by cdminter59 View Post
Read this article then you will understand how to set the initial, total, and with vacuum advance.http://www.crankshaftcoalition.com/w...EI_distributor
Thanks for the link.
10-09-2012 12:59 PM
cdminter59
Advanced Timing Question for built 4.3

Read this article then you will understand how to set the initial, total, and with vacuum advance.http://www.crankshaftcoalition.com/w...EI_distributor
10-09-2012 11:08 AM
S10BlazerBuilt
Quote:
Originally Posted by vinniekq2 View Post
no load,no vacuum at idle,is the static timing.3,000 rpm in park,no load is full advance(or should be)This is just a starting spot and will get you very close if you follow this procedure.

recurving the advance takes time/or money.(both)
I also forgot to mention that it doesn't idle at factory. Factory is 750, it idles at 1250. All sensors and etc are new.
10-09-2012 10:58 AM
S10BlazerBuilt
Quote:
Originally Posted by vinniekq2 View Post
no load,no vacuum at idle,is the static timing.3,000 rpm in park,no load is full advance(or should be)This is just a starting spot and will get you very close if you follow this procedure.

recurving the advance takes time/or money.(both)
So does this mean I should set my initial, then when I plug the ECM back up, do I take off the main vacuum/plug it? Then follow your steps?
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