Timing Change - how much does it affect low end power?

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bellabulldog

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My timing is currently set at 25* degress and I'm unhappy with my low end power band, how much difference is it going to make on the low end if I retard timing to 16*?
 
17 and under, you won't notice.
18-23 and you're in a sweet spot of best of both worlds.
24-32 and you better be spinning some rpms with larger charger(s).
33+ I like you, but you're crazy man.
 
When we bumped the shop truck from 20* to 25*, we were no longer able to build boost at the line/build enough boost to do standing burnouts. I was surprised that 5* was all it took to finally stop the ability to do boosted launches similar to staging at the drag strip. This was on our 95' shop truck with a maxed 215 pump, lower than stock stall DPC triple disk, 369sxe turbo w .80ar T3 housing, and most of all hot summer at 5700' altitude.

With that tidbit, I think you'll have small but noticeable pickup in spool-up going from 25* down to 18* or so.
 
I tried 18 and 20 on a 215 pump but I had to really go back to stock timing to get the smoke vs. off idle power good for stop and go driving. It falls flat at higher rpm as you would expect.
If I ever get the coin im going to try a blower kit (or high compression pistons) on it next so I have the low rpm air to add back a some more timing and fuel via AFC.
Also Id say my stock 160 pump pulled harder than this 215. doesnt make much sense but thats what my seat of the pants dyno tells me.
 
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Not trying to derail the thread, but I also don't want to start a new thread for a similar question. Where should timing be with non-i/c pistons and 155* injectors? Running 18* now, and feel like I need to go several degrees higher to get rid of a smoke problem
 
Not sure at what point the spray is out of the bowl with stock washers and 155*.
But I can tell you the low end will smoke more and make less power the higher you go.
Non-ic pistons should be the same compression or a tiny bit lower because of a higher crown to top ring measurement. But if you are not running an intercooler in the truck you will run higher EGT. higher timing and more turbo will help bring it down.
If you could -raise- compression a little that would help with low end power and smoke.
Mine reads 360psi (low) on all cylinders when cold. 240k on it.
 
kawi600 said:
Not sure at what point the spray is out of the bowl with stock washers and 155*.
But I can tell you the low end will smoke more and make less power the higher you go.
Non-ic pistons should be the same compression or a tiny bit lower because of a higher crown to top ring measurement. But if you are not running an intercooler in the truck you will run higher EGT. higher timing and more turbo will help bring it down.
If you could -raise- compression a little that would help with low end power and smoke.
Mine reads 360psi (low) on all cylinders when cold. 240k on it.
Click to expand...

The truck is a p pumped 12v with non ic pistons, very mild port work, 188/220 cam, s467fmw and 5x.014 155° injectors with thin washers. Pump is a 160to pump worked over by Seth with 4k gsk and 7mm dv's. Afc live is installed, and everything on the bare minimum setting I was still getting a considerate amount of smoke at 18° timing under acceleration and a slight grey haze at 2k rpm running down the freeway at around 70mph. Egt's were never high, around 850ish during those circumstances. I plan on stepping down to a s362 asap but I bumped it to 20° timing today and it seemed to run pretty clean going down the road now
 
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opening up the intake ports decreases the speed of the intake air and lowers swirl, which diesels need for good combustion at lower RPM. Cam overlap will do the same thing. Theyre all mods that move efficiency up in the higher revs.
I went through this awhile back on mine. Need to bump airflow when you open up the ports or add a cam. only ways I can think to do this are higher compression, supercharger or small tow twins. A VGT turbo in the mix may help.
Once youre on the turbo, if its still smoking youre running out of air. gotta back off on the fuel plate.
 
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when I went from 12.5 (stock) to 20 on my setup I lost a lot of spool, can barely spool at the line now, don't think the little bit of top end gain was worth the low end loss. Ill probably end up running 18-20 on the street and just add another turbo for top end power...
 
I know the OP was about injection timing, but the symptoms can be affected by valve timing too.
There -was- a guy developing a mechanical jake brake setup for the 12v Something like that could be taken a step further and made into variable valve timing and would help a lot with that off idle smoke.
One of the vids is still up on youtube, but everything else is gone.
Theres an old pirate thread about it..
http://www.pirate4x4.com/forum/tow-rigs-trailers/1115351-finally-real-6bt-12v-jake-brake-not-exhaust-brake.html
 
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