LS3 Low RPM Timing Boost

[gmorris]

Quick question for anyone running a 2300 blower on a stock LS3 with decent blower cam...what kind of timing are you running at low RPM (like 1000-1600) under boost? I know every motor will be different but all the magnuson tunes I have looked at have timing super soft in that region...like 6-7? between .8-1.2g airmass. With an A6 and stock stall I'm hitting 1g airmass at 1200 rpm when launching and the super low timing makes it fall flat on it's face. I've been slowly adding timing in but just curious what most people are running at low rpm vs mid/high rpm under boost. I'm up to 10-13? and it's completely changed the car lol.

Running a heartbeat with 224/232 0.600/0.600 cam, stock heads, 7psi peak right now on an 87mm pulley, stock lower, ID1050x/meth.

[Lakegoat]

I don't know how you are getting .8 to 1.2 g at that low rpm. At 1100 rpm, mine is about .3g. Lets see your log of that.

[gmorris]

This is the first log I pulled up and it's from a hot afternoon so it only pulled .68 @ 1200rpm but in the cold I've seen it do more. This was just a quick throttle stab from a stop. Ignore the ugly afr error on this lol, must have still been dialing in the fuel and mani volume when I took this. This is also after I started adding some timing to see if it would pick some snap down low. Screenshot is from the magnuson tune that I've found several versions of. I know they're set up safe but 5 degrees is pretty low and when it came off my 20 degree idle timing it really stumbled.

launch2.hplScreenshot (3).png

[Lakegoat]

Something screwy with your map sensor reading. Post your tune and what (for sure) are you using for a map?

[gmorris]

What makes you say that? Sensor is a stock lsa/zr1 sensor. Keep in mind at my altitude normal baro is 87-88kpa and it does the baro update thing but when I correct the boost for our baro it's right where it should be.

current ecm tune 23-08-18.hpt

[lukearmstrong1990]

it says your barometric pressure is 104KPA. your data is correct for a stock LSA MAP sensor.

your PE is delayed until 2000RPM and your wideband records 1.17 lambda (17:1 AFR) under WOT until after 2000RPM where is richens up.

PD blown car will be HATING being that lean under boost down low.

0 out your PE RPM delay and disable your fast torque exit. use the VVE table to dial in the transition into boost.

with a nice 12.5AFR into the transition tapering down to around 11.8AFR by full boost you'll probably find it takes the timing youre currently commanding.

PD cars under boost down low generally don't take much spark. you need to add it in progressively with RPM as air velocity increases.

also zero out all the spark correction tables that aren't relative (piston slap, fuel, VCP, catalyst etc.) basically IAT and ECT should be the main correction tables which need work. youre not pulling any timing from IAT

disable burst knock too.

[lukearmstrong1990]

LS3 HB2300 11psi.hpt

LS3 with 22x/23x .600ish 114 cam manual. HB 2300 blower and full exhaust. 11psi full boost pump fuel.

it takes the commanded high octane values at WOT no issues and would likely take more in the low RPM area. difference being its straight into the 11.8-12.0 AFR region at anything about 4PSI boost. and it starts at 12.5 AFR on the transition into boost... not 17:1 like yours is.

[gmorris]

Thanks for taking a look. Mine has no problem taking timing either...it's actually really knock resistant and I've never seen more that .5 degree retard anytime. I have just never worked with a higher compression PD blower setup and wasn't sure what kind of timing numbers are expected down low like that. I'm up to 13 degrees now and no knock. Also, as I said that was an old log to show lakegoat the airflow I was hitting and I didn't have the manifold volume and fuel dialed yet. Now it is .78-.8 right off the hit and commands full PE at 1200rpm with a slight ramp despite the delay still being in there (still going to change it and hopefully be able to drop my manifold volume a bit). I have more timing everywhere than that file (adding more in the low IAT range for the meth) but I'm only running 7psi.

MAP only says 105 kpa or higher after it goes into boost once. At startup it will read 87...there's no way to avoid the baro update without going 2 bar is there?

[lukearmstrong1990]

high comp PD blown cars on pump fuel are most prone to knock in low RPM high load areas. I always ride on the side of caution and roll in the timing under boost with RPM and I never get too aggressive unless on E85. being such low boost you'll be able to add a reasonable amount. having PE or BE as soon as the load is introduced add enough fuel is super important with PD cars on pump. lean low RPM transition under boost easily causes knock.

as for tuning WOT and the transition into boost below 4000rpm you'll need to use both your VVE and MAF tables. I would recommend scaling the VVE MAP axis to include some columns into boost up to at least 160KPA. tune both that and the MAF table to adjust fueling for the transition under 4000rpm. or disable the VVE table and use MAF only.

as for meth injection I personally hate it. yes it cools the intake by turning the liquid into a gas and absorbing the heat energy from the manifold air charge reducing its temperature. unless its direct port injection it doesn't do it evenly for all cylinders. some run hotter than others. the hotter ones can knock individually without you picking it up. this can cause damage. the Meth also alters the AFR as its alcohol. again not evenly for all cylinders. some leaner some richer and you're tuning off a combined bank AFR at the collector. if one pot is too lean it can also cause damage. the meth injected into the manifold, once it enters the cylinder raises the octane of the fuel as its now part pump gas part methanol and effectively an ethanol blend of small percentage. this is also not even. one cylinder may be 100 octane the next 95 etc etc. the methanol allows it to take far more timing than without. individual cylinders if you're commanding too much timing for its particular octane can also knock undetected.
if you've got an extra 4 degrees spark and your VE table under boost is 15% less than it would be without the meth injection then heaven forbid one day if you're doing a WOT pull and the meth runs out it will melt and knock pretty aggressively. have seen engines melt from that.

I wouldn't suggest adding timing vs IAT to make use of the Meth injection. I would tune the high octane to what it will take without meth but a cooler IAT. that would be the max I would use and only use the IAT corrections to retard timing with high IATs.

you also should compare for yourself WOT AFR with water/meth, water only and no water/meth. you'll likely be surprised