hodge9386

iTrader: (5)

Just curious to what your timing strategy is? I have been doing my own tuning for a few years now and I am by no means a expert and am always trying to learn new things. I have done a lot of reading on timing and it seems to be some huge secret within the tuning world. It is pretty common knowledge that a ls1 style engine likes 24-28 degrees of timing at wot but without having a dyno how are you supposed to know if it likes 24 or 28 degrees? My engine seems to like around 25 degrees so thats what I run it at and it runs very well but who knows. Also what is the best way to bring in the timing? Do you start low and bring it in up top or do you give it more timing down low bring it down up top? I have been starting low and ramping it up to my desired timing around 3000 rpm. I have looked at several tunes in the repository and this seems to be how most people do it and my car seems to run well doing it that way but if there is a better way please teach me.

I attached a copy of my tune so you can tell me what you think.

redtan

iTrader: (5)

You don't know...that's why tuning on a dyno is so important vs. just a street tune. You can never know what your engine likes or what makes the most power without some sort of concrete result. Some people say you can do the same thing at a drag strip and see if more timing helps your trap. But there are so many variables with drag racing that any little thing can affect your speed and you won't get an accurate answer whether or not the timing change did anything.

You start high at low RPM, around 3000, ramp it down smoothly to wherever your peak torque is, then ramp it back up smoothly to redline.

Ideally your timing curve should be an inverse of what a torque curve looks like on a dyno. The less torque there is produced, the more timing you can run due to lower cylinder pressures. The more torque there is produced, the less timing you can run due to higher cylinder pressures.

hodge9386

iTrader: (5)

Ill have to find my dyno sheet from the last dyno day I went to but myy car has a flat tq curve from the time I hit the gas till probably 5600 or so. Is that because my spark table is flat?

redtan

iTrader: (5)

Yeah please do share it, cuz unless you have a PD blower I can't imagine your torque curve is dead flat. That or you went from 4500-5600 only.

hodge9386

iTrader: (5)

I cant seem to find any of my dyno sheets. The previous tune is tuner locked the attached one should be good. I added 3 degrees of timing under 4k rpm because I noticed in the attached log that the cyl airmass was dipping down under 4k rpm. This is also noticeable in the car when making the pull. If I start a pull from 2500 rpm in 3rd gear the car pulls pretty good then at around 4k rpm it really kicks in and pulls good. The previous tune was flat lined at 25 so I added a few degrees to try to get the dip out of it. I havnt tried the new tune yet so I dont know if it worked.

kingtal0n

iTrader: (1)

Another timing thread I put alot of info

https://ls1tech.com/forums/nitrous-o...07-timing.html

It is similar to what was said here already about timing vs torque.

The ' other stuff ' iis considerations that compare EGT managment vs fragile cast pistons in daily driver applications. I.e. if you can manage your EGT, have a gauge, are using methanol, blankets, coatings, all of that... then using minimal timing, while limiting peak power, will also help preserve the fragile castings through a wide range of operating conditions.

hodge9386

iTrader: (5)

Thats a good read. I see where you said you start off bringing in the timing then taking a couple of deg out around max tq then ramping back up which is what I have always done buy you mentioned that with modified engines you might not have to do that and could just flat line it. How do you know when you have got a combo you can do that with? If i can make more power by leaving the timing in it then I might as well do that. It would be nice to get more low end power, the cam in my car kicks in hard at just under 4k and seems to fall off a little up top if you look at my log which is the intake being a restriction that im about to fix this weekend with a fast 102 setup.

kingtal0n

iTrader: (1)

Engine which are prepared properly for enormous pressure spikes with mods like O-ring seal, are ideal for using maximum timing to generate maximum torque. If there is a factory HG you want to be as far away from that peaky spike of pressure, so we use vastly reduced timing, which knocks some % of efficiency off the table with the reward of being easier on parts. Where does that lost energy go? It is seen in the EGT. The only major danger of reducing timing is the increased EGT due to energy left in the exhaust system, for which there are many ways to control such as water/meth which further reducing efficiency to make things even safer. Ultimately for max power want to move the largest airmass as safe as possible so a combination of effects (both reduced timing and cooler "egt" which is really combustion temp we want to lower so we can move even more air mass and react it safely). This is assuming infinity airmass is available (an infinite turbocharger). Once we start placing restrictions on the airmass, we can then attempt to extract max power by allowing temperature increase (faster hotter moving exhaust is a performance feature) and increased timing, move towards the better sealed up engine, as crankcase pressure is another feature which can be manipulated as well as oil containment. Like the difference between a stock HG and an O-ring there is a difference in crankcase from wet to dry ability which must be taken into account when deciding whether or not to use maximum boost/temp/timing for maximum effort (competition, win at all costs) and the more testing you can do prior (engine dyno sessions with similarly built engines you have performed and observed their behavior and output, assume infinity longblocks are available ideally you will have tested countless engines) the better the result.