ok ..

probably saw another post or two by me for the timing tables / help with tuning problems ..

well someone today mentioned that my spark plugs are too short (i got vortec heads) .. so i changed them out ..

now the car runs ALOT smoother in open loop, but once it hits closed .. it goes crazy and starts counting up knock counts and retarding the timing like crazy ..

ive played with everything from spark tables to reducing fuel / adding fuel .. best i found was the stock table with 2-3* taken out before 3200 rpm ..

but in all of them i have a problem with knock occuring in the low rpm (1200-1600) and around 40 to 70 kpa according to the datalogs ..

now my question is .. what causes this knock .. b/c ill be driving one minute and itll run fine at that rpm / load .. then a couple miles later it will pull timing and run rich ..

any ideas what is causing this / how to fix it ..

i need the car asap for college ..


adrian

 

What do you have your base (static) timing set at with the EST unplugged and what do you have the base timing set as in the PROM?

Make sure they are both the same.

When I burned a chip for the first time for my 305 i set the timing to 13* BTDC and plugged the est wire back in. Then I advanced the timing even more, (by turning the distributor) which turned out to be a big no no.

I ended up adding way too much timing and I got these large spark knocks at low RPM's and I couldnt get the spark tables right.

 

im pretty sure im sitting at 8* .. and i set that in the prom ..

but ill be sure to check it, just to see if the distributor came loose on me ...

umm .. oh also .. i noticed in the datalog ..

for a few values in tunerpro where it says "spark relative to TDC" and "spark relative to reference pulse"

sometimes, when its detecting knock .. those values jump up to 3000* or so .. what causes this?

 

Like I suggested in your other post, Download Datamaster and VEmaster $8D.
Do several iterations of 10-15 minute "cruising drives", stay off the throttle and get good data to work with.
Clear the ecm after each run/change.
By the end of the day it will be runable, then you can target trouble spots within the overall range later.
The knock could be coming from lean spots or too much timing.
Look at your logs for what the timing and BLM was during the event. Pull timing or add fuel to start with and then start logging again.

 

Sorry i don't know speed density that well.

Are you saying you have L31 style vortec heads? In a 305 with that huge camshaft?

What injectors you using and what is the injector constant set at in the PROM?

You are probably going to have to do a lot of tuning to get it to run right.

Listen to JP, i had to do a lot of datalogging with my MAF setup.

 

im running summit racing vortec heads ..

and the comp cam 08-501-8 cam which is slightly bigger than stock .. my 91 z28 305 tpi cam stock with a 350 cam in it ..

im thinking that it might be too much timing ..

if the computer takes out 20* during knock retard .. does that mean i need to take out that much timing .. or just a little ..

if i have to take out 20* then that means ill only have around 8* left .. which makes no sense to me ..

idk .. i guess ill figure it out ..

 

Thats basically the same cam i have in my IROC, at least i think thats what the previous owner put in there.

What do your spark advance tables look like?

Are you using tunerpro?

Go to your BIN and double check Base Timing and go in there with a timing light and warm up your car.

When its at normal operating temp, disconnect the EST wire by the blower motor and double check to make sure you are at 8* BTDC.

Turn off the car, reconnect the EST wire and clear the codes if you need to.

If you have 6*BTDC programmed into your PROM and you have 10* or something else thats timed on the distributor, you are going to be over advanced at just about every RPM range.

Also you might want to do a search for Vortec TPI setups and see what the other DIY guys say about tuning for that setup.

If you are running stock 19# injectors you most likely need to set the injector constant at a lower number to compensate for the extra air you are sucking in. This is where datalogging comes in handy.

You may notice that when you log you are going to be running richer down low and leaner up top with that cam.

 

im pretty sure im running 8* in both the prom and on the motor .. ill check next time i get it warmed up though .. i might be 1* off ..

i got the injector constant set at 20.3 right now with the stock 19lb injectors .. im running 46 psi .. so i used a calculater online that said mine are 20.3 pounds now .. should i make it lower instead of higher .. ???

ive noticed im running rich down low and it gets to 128 the higher my rpms get .. will this get better by tuning the ve tables .. or is that why the blms stay at 108 even when i lower the ve tables ..

EDIT:

i just tried a lt1 spark table a second ago .. and it had less power but i dont think it knocked as much as the stock table with 2-3* taken out ..

when i say it didnt knock as much .. with the other table you can feel the computer taking out 8-20* of timing and the car falls flat on its face .. but it didnt do it as much with the lt1 table .. guess i dont need much timing with the vortec table .. or i might be running lean .. could i be running lean even if the blm's show 108 in the low rpm's???