It's been a while for be in the boosted LSx world. While I didn't have my Vette from 2010 through a week ago, I still had a boosted 93 LT1 Trans Am.

With having the Vette back, it's got the "race gas" tune in it. I quoted that because, it's set to 16 psi, and with the race gas tune is only running 18* peak timing. On the pump gas tune it's running a peak timing of 16* under boost.

That seems ULTRA conservative to me. Even the previous owner thought it was conservative. I'm used to the LTx Gen II world and the like still, where I was running over 20* timing on 20# of boost.

The question I'm boiling down to is how conservative is this race gas tune? Conservative enough to through pump and be safe to give it the throttle at will? Or not? Like I said it's been a while for me and I have to brush back up on my LSx world knowledge.

 

Theres no way to tell based on the information provided. There are a million details that affect this. Stock motor? Cam? Compression? Forged components? Type of FI? Meth? Target Lambda? Are you observing any knock? It sounds like you need to find a good local tuner who can pull the tune to go through it with a fine tooth comb, hook up a wideband and make sure that the VE table is correct, etc.

16PSI seems optimistic on stock internals, but I'm sure there are a million opinions on that. I'm running 11-12 through a twin screw and I feel like I'm pushing it, but it's all in the tune and I went to a good one rather than tinkering with it myself, even though I have all of the tools and most of the knowledge needed to not blow things up.

 

It's built. No factory stuff. Forged LS3 Shortblock (factory crank, forged H-Beam rods, custom forged diamond pistons), 9.25:1 SCR, twin turbo, meth, AFR shooting for 11.0-11.5 on meth I believe, don't know about knock, have AFR gauge in car. Have pump gas in it now and it actually runs better than with the race gas it had when I picked it up at part throttle and especially highway cruise. With the race gas at 70-75 in 6th it felt like it was cam surging. Pump gas and it cleaned right up.

For the most part there's a range per se where the vast majority of people fall in terms of timing at certain amounts of boost. I always remember the LS stuff being lower than the older LT stuff, but 18* timing at 16lb boost on race gas seems very very conservative to me. As it sits now with the race gas tune is how it ran the mile. I plan to have a tuner look at it in the future and get away from the OLSD tune and back on to a MAF tune (it has the 100mm LPE drop in MAF setup, so it has the resolution I'd need) to better driveability. Street car first.

 

Hey fastbird do you have hptuners download the file and ask the hpt forum they will help

 

BTW I'm on sd and its totally streetable

 

You can't compare a Gen 2 engine's timing to a Gen 3's Old school SBC's could run 20-22* with 8 lbs of boost the LT1 style engines slightly less---However the LSX engines have such efficient heads that aggressive timing does not make more HP and maybe even less without having detonation problems---A typical boosted LS1 with a manufacture's
canned tune may only have 11 to 15* of timing at WOT depending on the boost and compression
ratio---with no loss in HP--- With canned tune from the SC manuf---they usually error on the side of safe---So the most you can add safely is only another 1-2 degrees---You are already getting over a 100 HP increase with a SC so why would you gamble by adding too much more timing to gain another 10 or so HP----A dedicated race car is one thing where you may want to push it to get that last little HP left on the table but a street racer used as a daily driver??? you're asking for trouble----eventually---

 

I don't thnk 18 is conservative. Even with a built motor and meth. If you're not getting any detonation, put it on the dyno at 14 and add until it doesn't make much more power(and doesn't knock of course) and take a couple out of it. I rarely go above 16 degrees with a decent amount of boost, the motors just don't need it.

There are plenty of times you can add timing and not pick up any power yet still not be knocking.

 

It's fully tuned, road and dyno. I just felt that 18* was conservative but I was apparently wrong. Still trying to get the Gen I and II stuff out of my head. Just have to watch the go pedal until I can get the tune looked at and cleaned up/changed for my own purposes.

HP tuners won't work, it was tuned on EFI Live.

 

Are you logging knock or checking plugs? If you're running 91 with straight meth you're probably not going to hurt anything even if the timing is not needed. I just err to the side of caution, no point in trying to eek out that last couple HP.

You could save a log and your .bin and post it on EFIlive and they can look at it.

Is there anything you're really worried about other than the amount of total timing?

 

Right now I'm only concerned with the timing. A plus is that I am fortunate enough to have 93 octane gas available everywhere, and I have a good stock of straight meth. I just dont want to go make some pulls and have it start detonating because of toi much timing. Its definutely not tuned to the ragged edge but it is still one of those better safe than sorry things.

 

Somebody's wrong, but it's not you.
Telling someone how much timing they should run is irresponsible IMO.
Helping someone figure out what timing their car likes is the conversation to be had.

If you haven't already learned to properly read plugs, I recommend you do that. Make a pass, shut it down, pull your plugs at the end of the track.
This doesn't work on the dyno and don't let anybody tell you otherwise.
The generalized statements about timing are worthless. I've run 22° timing on 10.5:1 compression, stock bottom end with 21psi boost. Think that's nuts? Maybe so, but the car got the crap beaten out of it for 3 years before giving up the ghost and it wasn't on that tuneup.
The job of any good tuner isn't to decide how much timing to run in a car. It's to let the motor decide. A good tuner will learn to read plugs and read the proper feedback from the car and make adjustments accordingly.
Dial the car in with YOUR motor, and YOUR fuel and your race. If you dial it in for the best 1/8mi and then go run 1/2 mile races, you can expect to hurt things. If you change fuels, tire height, track length or anything like that, it'll be time to revisit your tune.

I might not start off at 18 degrees, but when you're done, it's quite possible that on race gas, you end up over 20°. There could easily be 60RWHP in a few degrees of timing. It depends on how badly the car wants it. As you approach the point where the car is happy, you'll see it quit giving you gains and you'll know to stop. For the record, if you think you're close and you want to be conservative, you can increase timing in increments of less than 1°

 

I gotta ask what that combo was. What engine? What heads? 21psi and 21* total sounds like a recipe for either a really really fast car, or a really really slow one hahaha

I did a bone stock 5.3 with an s480 on 12psi and 11* of timing it made 650 to the tire and ran 9s, this was on pump gas with one nozzle 50/50. Yes we could have gotten away with more timing and definitely picked up more. But a 9 second stock *** 5.3 in a 3200lbs car was pretty legit. Didn't need to **** out a rod before the cae even made it to the track.
After a small cam swap and switching to straight meth(still single nozzle) it made over 800 to the tire on 14psi with 13* of timing.

 

With meth you're not going to hurt it. Knid of doubt you will without meth either to be honest. But I do like safe myself Just don't know if the timing is necessary. That's why you either put it on the dyno or take it to the track and find out. Like I and blownblue said, the car will tell you what it likes. You will hit a point that adding timing won't net any real HP increase. That's when it's time to stop.

 

60 RWHP with a few degrees of timing is an overstatement and a pipe dream---LSX engines don't require a lot of timing to make max HP---Look at a stock boosted Corvette and they have around 11* of timing at WOT --I'm sure that's conservative but going to 18 20 * would be extreme---A dedicated race car is one thing where you may want to run everything on the ragged edge---But on a DD/weekend racer--18-20 seems too much on pump gas especially--- as mentioned reading the plugs can tell you a lot as well as a wideband 02 where exactly your combination is at---Advice on the forum is strictly a basic average starting point--

 

Between the two of us, only one built and tuned the quickest and fastest stock bottom end C5 in history and speak from experience. Call it a pipe dream all you want. It's obvious you don't understand and therefore don't agree and that's fine.
Fastbird I don't advocate changing spark timing without doing it properly and responsibly. If you're unsure, back it down and leave it until you're able to get comfortable with feedback from your setup.

 

I definitely appreciate your input on this. Your words and advice ring very true on everything stated (Yes, I've seen a couple degrees timing make a HUGE difference, did it to my boosted LT1 on the dyno a couple years ago).

For what it's worth, the car hasn't been tuned since before it ran the mile in 2012 and was run on race gas, but PLENTY of pump gas has been run through via the previous owner and his tuner without issue. I guess you could say I'm being overly cautious if anything, probably simply because I'm still getting reacquainted with the car and don't know all of it's nuances and tempermets again yet. I'm actually pulling the plugs when I get a chance and time because I want to put a fresh set in anyway, so I'll have a look-see then and see what they say though I only opened it up once (and good lord it's far and beyond more powerful than when I sold it) for a quick 2nd and 3rd gear pull. I'm not planning on changing anything up unless it NEEDS changing (or I get to a tuner to have it reworked and polished up a bit) in terms of tuning/timing.

Honestly this entire thread wasn't so much about the car because I'm feeling more and more comfortable with it at this point, it was more of a "get me back into the general vicinity of thinking for LSx related timing" so I could rewrap my head around the differences so I could KNOW if it needed to be addressed or not.

 

What did the car run? Share some specs on it, heads, cam etc/

 

I assume Arun?

We've gone 9.16 @ 156 on a shakedown in Sac and the 9.11 @ 137 diff **** itself midway through the run but was .2 quicker at the 1/8th on thaty second pass.
This was a stock bottom 6l on 16psi and 14 degrees of timing. Car weighed a little over 3k on a 26" tire and pump gas with meth.

 

That's a C6, no? This is quickest/Fastest C5 to date, owned by ALGZ06

9.03 was quickest
149 was fastest.
Stock bottom, TFS heads worked by BTR, custom cam by BTR, stock intake and throttle body, the 149 was with a A&A T trim kit. went a 9.19 with that T trim then went 9.03 with ECS Novi 2200.

Beat the **** out of it for 3 years at the track and drove it on the street regularly the whole time too. Full weight, (well over stock weight) Z06. It's done now. Finally puked and nobody's crying over it. We wanted to see how many licks to the center of a Tootsiepop.

 

No it wasn't a vette. Untouched lq4 with off the shelf TFS heads, a Dougherty racing cam and an s480. Pretty basic stuff. But 156mph was pretty impressive.

Same with going 149 on a t-trim lol that thing must have been maxed out. No wonder it needed everything you could give it lol