i am going back to the dyno on saturday and have a few questions about timing if anyone is interested in tossing out some info. i am sure "every set up is diferent" so i wont take anything i see a gosipal but i would like to know what some of you other guys are seeing. i also know what works on the dyno may not work at the track so i will be dialing it back and working back into it once i get to the track.

is there a rule of thumb or any real world experience on how much timing you need to add when switching from pump gas to race gas just to make up for the slower burn rate of the race gas?

i was told minimum timing should be at peek tq. is this true?

i was also told to keep prety decent timing in it while spooling and that would help it to spool faster. is this true?

i was also told to keep it lean(not super rich anyways) while it is spooling up and it will spool quicker. is this true?

i was told more timing in the upper rpms will help with the power up there? is the true? if so how much more timing? lets say i am at 15deg at 5000rpm and thats my peek tq how much timing should i be looking at around 6500, my peek rpm?

i was told when playing on the dyno to add 2 deg at a time and i should see significan't power each time. once i dont see a nice gain like 35hp then go back to my previous timing numbers and call it good. this seems reasonable. anyone disagree? if i keep gaining power as the timing goes up is there a max timing number i should just stop at?

i am sure i will have more questions. right now i am running the same turbos as many supra guys. they have 3.0L and one turbo and i have 6.7L and 2 turbos. i am told they see 30psi by ~4000rpm. i see 23psi by 4700rpm. with the extra cubes i would think i should be spooled sooner than them. is it tuning or maybe the turbo kit design(log headers). the local dyno is very reasonable so i will have some time to try diferent things. i just want to have a good idea of what i want to try.

TIA

 

I can only comment on a couple of things I've seen. kp, Mike, Harlan, etc can add the hard answers.

1. More timing makes my combo spool quicker...I actually dropped timing down low to keep from blowing the tires off.

2. More timing up top does help my combo hold hp up top.

3. My min timing is at max torque.

4. My timing curve is U shaped.....starts at 17 drops to 14 at peak torque slowly ramps up to 18 at 6000rpm......I drop the start of the U down 2 degrees if the track is sorry.

Good luck!

 

i have heard that pulling timing puts more heat in the exhaust and makes faster spool, but ive heard adding timing helps spool too, but nothing that makes sense to back it up?

i posted up my timing chart a while back.. here found it..


i'd like to see the same screen from Mike Brown.

 

These are just my opionions based on engines I have dealt with. I very rarely look at the power number on our chassis roll, I just use it to check tune.
I have very little difference between peak torque/hp in my timing maps on a 402ci engine. Generally picking common points I have 19 degrees at 5500 at 22 psi, then it tapers to 21 degrees at 8500 still at 22 psi. It will depend some on the cylinder head, generally better heads will use less timing at a given boost number.
With the intake you are using I generally remove fuel from the corner cylinders. In the Nova I have correction at -6 on cylinder 7 and 8 and -3 on 1 and 2. This engine has the throttlebody on the rear (pointing towards back of car). I do this with the chassis roll, I just clean cut the engine at the end of a run, then line all the plugs up. Adjust fueltrim for a uniform color.
Spool timing. I have timing at 4500 (this is two step set point) 33@2psi-32@4psi-31@7psi-24@11psi (it normally leaves here) 21@15psi. The high early timing helps to "bring it up". You may want to alter injector timing on buildup to help it spool.

Kurt

 

I bet you would.

13:1 A/F and 28* of timing helps to get mine spooling. I bring in more fuel and start dropping timing as the boost rises. Auto cars= more timing/less fuel. Manual cars= less timing/more fuel.

 

I left mine at 14 at the top of wot, its in the 20's in the mid range though. Im just a street car though and i run it at about 11:5 a/f as well. Im too scared to blow it up

 

Interesting thread. What do you guys consider to be normal spool time to get to say 4400 rpms on a 2step?

 

Time to hit 4400 rpm on a 2 step will depend on the converter and the turbo spool time assuming it's also on a TB. I have a 2600rpmstall and it would hit 4400 on the tb in ~2 to 2.5 seconds.

 

The tune will make a big difference as well, and with the BS3 you can tweak the timing and fuel while on the 2 step to help spool it faster.

 

Underwoods car takes just under 1 second to hit the two-step once the transbrake is applied, I think Mikes car does it faster. If you can get it down under a second, you will race well.

Kurt

 

the timing helped a ton and we worked on the fueling some too. i couldn't get rid of that dip at 3000rpm, thats right when the meth kicks on.

up top i picked up 43hp at almost 2psi less boost. this is at 21deg peek timing and 19.5deg at peek tq. the run from before was 16deg all the way across. it also picked up some nice power in the lower rpms even though it was spooling slower. i need to work on my valve train so i can carry this power into the higher rpms.

here is a link the a more detailed post >> https://ls1tech.com/forums/forced-induction/592346-back-dyno-again-1055rwhp.html