22lambo

Hi there, I am using TunerPro VT 5 to tune my LT1 Camaro. The Camaro has a Vortech supercharger with 5 lbs of boost. I want to know how much I should retard the timing and where. Any other tips are greatly appreciated. Thanks!

Orr89RocZ

iTrader: (20)

5 psi isnt much but definately want to try pulling around 5 deg total for now at 5psi. Try 1 deg per 1 psi of boost and see where that gets you. Keep air fuel around 12.0 to 1, slightly rich for 5 psi. More conservative would be to pull 6-7 deg and run 11.5 to 1 air fuel. Then work up from there, adding timing and reducing fuel to get the engine to its peak performance.

At 100KPA map thats WOT for a n/a motor. Boost comes in after all that but its not linear. It will move up and to the right on the table. YOu may start making 1-2 psi at 2800 rpm and by 3500 be at 5 psi. It may make instant 4-5 psi at 3000. Hard to say.

Just taper your timing curve up as rpms rise. Then taper it down as MAP increases. So at peak hp rpm, say 5500 rpm at WOT for a n/a engine you may have 36 deg timing. For 2 psi, I'd make that 34 deg timing. Then at 5 psi, make that 30-31 degrees and see what happens. Taper it down something like this: 5500 rpm, 31 deg timing. 5000 make it 31 deg, 4500 ish make it 30, around 3600 make it 30 and then go down from there alittle at a time. 3000, 29 deg. 2600 ish 27 deg. etc.

Thats just my advice on what I did with my turbo car and it seems to like it so far.

You may find out with your setup it may want full timing at 5 psi, or may only need 2-3 deg pulled total and only at 4-5 psi. 0-3 psi may want full timing. Just something you need to play with.

Ronny

iTrader: (1)

Orr: Would you suggest same SA curve for a 75 shot of N20? I will need to check my SA table but I think when in PE I am at 36 deg but it tapers off at higher RPMs(4000 to6000). Does not boost similar to N20 as in increased cylinder pressures? I suspect all increases engines VE?

ps. I have NOS installed but need to determine why hitting on only pass side cylinders. Should have that sorted out on weekend.

Orr89RocZ

iTrader: (20)

General rule was to pull 2 deg for every 50 shot. I think that is a good conservative tune. Some have said 2 deg for every 50 shot after the first 50 or 100. All depends on what the motor wants.

Also want to make it abit richer to be safer. With good heads that have efficient combustion chambers, you may not need to pull much timing. For my 383 HSR motor with 150 shot, I only needed to pull 2 deg timing over my n/a tune. That motor only needed 34 deg n/a so I ran 32 with the shot. Air fuel was near 11.8-12.0 to 1 on spray.

75 shot may not need any timing pulled. To be safe, start with 4 deg pulled and watch the air fuel ratio. Make sure you are slightly rich and then start playing with timing. I'd use a similar taper to the timing curve as a starting point. Seemed to do well on my motors to have max timing in by 2800-3400 rpm depending on where peak torque was expected to occur, and to hold it constant up to redline. Track testing and dyno testing will help determine the best timing curve but that will take alot of runs to really find the sweet spot. My AFR heads ran 34 to 39 deg timing and dyno/track times didnt vary much. I ran lowest timing that made best torque which was 34 deg for me. So by 3200 rpm I think i had 34 deg timing, ramped up from idle to 3200 rpm in that WOT column. With the converter and gearing, I never saw below 3600 rpm WOT anyway

The best setup is a ignition box that has timing retard function so you can activate it once nitrous comes on. So when the system is off, you have full n/a motor power. Its easier to press the up and down arrows on the ignition box to raise/lower timing or swap out timing retard pins/chips for MSD type setups than it is to reburn a chip or adjust base timing.

Ronny

iTrader: (1)

Good stuff. thanks. My ECU turns on at whatever rpms I wish (>3000) and off same(redline 5800 so off 5300). Also MPH sensitive. On at 25 mph.

22lambo

I will post up my tables but stock timing was already pretty low. However I took away 5 degrees as you said and noticed a big improvement. Now I will go datalogging to check for knock because the stock on would have about a spike of 8 degrees of knock retard and the engine would choke around 5500 rpm.

Orr89RocZ

iTrader: (20)

yeah too much timing will cause some detonation at times and cause the motor to break up. Also can do that with lean spots. Make sure you are getting enough fuel with the boost.

22lambo

So did a run and man does it pull so much harder! However I had 11 degrees of knock retard at about 6000rpm at WOT and I am running 17 degrees on the table. Does this mean I am running lean? I don't have a wideband but I should get one by the looks of it. Thanks!

chevy1500z71

im running 31 degrees of timign at 8-9 pounds of boost with no knock at all, im spraying methanol tho.

i have to ask, are these numbers actual timing numbers or is there a modifier im missing, becasue it just seems odd how low the numbers are on a stock timing table. im having issues with knock retard durring light acceleration and its happening with the timing as low as 12 degrees, how is it possible that i can have a knock present at 12 degrees of timing with 93 octane and low compression.

Orr89RocZ

iTrader: (20)

The table may have various adders. There are tables to change timing based on coolant temps, based on PE mode, etc. All gets added in to the main table to make overall timing the motor should see.

Stock tables can be pretty mild. Some can be pretty aggressive, all depends on what motor you are talking about and which tune the motor came with.

Also you can have false knock counts that could happen if the motor is picking up noise/vibrations from things in the engine bay. Sometimes a noisey rocker/lifter, exhaust pipes on frame, etc. Can happen. Doesnt mean you have knock, but motor thinks somethings wrong.

22lambo

Oh okay. So should I worry about the knock retard or not? It seems to drive so much better to me and my dad and we cant hear anything. Then again, it's our car is very loud and I guess if you did hear something it might be to late

Orr89RocZ

iTrader: (20)

I'd check your tune to see how much fuel you are getting at 6000 rpm and if any more timing is being added to your table that you may not be aware of. It may be going lean too. Thats not a lot of timing for low boost but if its lean it will break up and have knock counts.

22lambo

Finally convinced my dad to buy a wide band so I will post of the afr when I install it. Thanks!

chevy1500z71

wideband is the best investment youl ever make, but it can be a real headcae if you dont get it right. make sure the sensor is as far back in the system as you can go and i like to put my bung in a small peice of pipe that extends a few inches from the exhaust pipe to keep it out of direct exhaust flow, keeps it cool. i used to go through sensors fast before i got the placement right. and a tip of advice for the future, dont go ordering new sensors from moates if they go bad lie i did, buy one from autozone, they actually stock the replacement sensor and have a lifetime warranty on it, i could have saved hundred if i had known this sooner.

i think my knock sensors is going off becasue i have forged pistons and they are set to a pretty loose tolerance being that i bought my short block out of a circle track car, i also know the valvetrain is a little noisy even when set properly, high lift cam profile and stamped rockers can just be a little noisy. of course none of this cant be heard over my super loud exhaust which im sure leeks at the headers a bit and the loose bolts on the collectors rattle too im sure so its very hard for me to tell if my motor is really knocking or not, i know it cant be knocking but i cant help but think it is when i see the sensor reading knock, what i did for now is put maximum knock retard to 0 past 80kpa so that it doesn't interfere when im really getting down, im afraid if i put it to 0 across the board it will remove all functions of burst knock like rapid throttle movement and things like that that i still want to retain.

22lambo

Okay so today I installed the wideband and my readings are 14.8 out of boost and 11 at WOT. So you said I should be running 12? How much fuel do I need to take away? Thanks.

Orr89RocZ

iTrader: (20)

11.0 isnt bad, its a real safe air fuel for that combo, but if its really only 5 psi boost, take out abit and run closer to 11.8-12.0. I think that will get the most power out of it while keeping it somewhat safe.

I'd try taking out alittle at a time. Assuming you have a MAP table that is handling the boost? You will have to guess what 1 VE change will do to the air fuel ratio and go from there.

Are you seeing any knock retard now with that current air fuel ratio? How much timing you running at 5psi thru that rpm range? Should beable to get near 28 deg I would think.

22lambo

Okay, sounds good.

I have a table that's called "Open loop AFR Vs Coolant Temp. Vs MAP" would that be the table you are talking about?

Yes, I still see knock some times but not all the time during WOT. During one run it when from 2-7 degrees of knock retard. My timing is

25 @ 4000
24 @ 4500
20 @ 5000
17 @ 5500-7000.