pwrtrip75

iTrader: (8)

I was running E85 but am going to use my car as a daily driver for awhile so I put 93 octane back in it. I dont want to reprogram my boost controller that has 3 settings. 8psi, 14psi, and 18psi. It is intercooled and no meth.
is 12* timing ok for the 18psi? ... or living on the edge trying to hit it with 18psi on 93?

2000 5.3L - stock bottom end, stock compression 9.4:1??, ported 5.3 heads, TU1 cam, PT76GTS.
A/F right around 11.6:1 I lowered my timing from my E85 tune to
8psi=20* 14psi=14* 18psi=12*

Most ive ever ran on 93 octane prior is 15psi on a 8.6:1 engine. Been on E85 for a few years.

Ive made some test passes on 14psi and no KR. Just curious if anyone else has ran 18psi on 93 octane? If its a bomb waiting to happen I might make my own meth kit... didnt want to, but also want my car to last a complete season too.

OldGold

iTrader: (1)

I did it with 10:1 compression and meth, 15-16 degrees of timing. I also cracked a ring land with the same motor and mix on 14 psi, although I think one of the pistons was just bad and unfortunately, cracked. When Matt had the car and was breaking pistons, he was breaking 3-4 at a time. Still went 140 on 7 good holes.

Mike

Twin turbo c5

I think 12 is fine I've run 18 psi before on other ls engine's im working towards getting there on my Fairmont .

Sarg

iTrader: (6)

Guessing you have a good intercooler? If not that and some colder plugs will probably help keep it alive on 93.

SPOOLED UP

iTrader: (2)

Colder plug for sure especially since your not going to retune it.
I had ran 18 without meth b4 but had a big intercooler and street drove it.

pwrtrip75

iTrader: (8)

My IAT's on a full pass in mid summer with E85 were 120* I dont remember the spark plug number that ive been running but they are the non-projected tip NGK -8's they seem to last forever.
I am retuning it getting it dialed in... I just want to leave the boost controller alone.

95bowtie

Im really debating going back to 93 from e85. Im only making around 600whp and thats all I want no meth.

Could I make 650-700whp on 93 oct with no meth? Car has a cam only ls1 running a 6 speed.....

copley87blaze

I think you are pushing it with no meth. With 93 oct I think you iat will sky rocket, heat - detonation. You could always mix your 93 with e85, maybe get it to 30 percent alky. That might help.

95bowtie

But then my tune will lean out. Once it's tuned it has to run that gas always since speed inc will be doing it I can't change it on my own.

Can I have them tune it for 600-700whp without the meth and add it later without retune?

In the mean time ill run around with it turned down to 550ish whp without the meth and 93 oct.

95bowtie

To note I do 90% of my beating on it at night when its usually 60 degrees or so....that should help some haha. Still ticking time bomb I suppose without the ole washer fluid injection.

Sarg

iTrader: (6)

No, and here is why..when the meth hits, the ECU does not know that it is there. At least on the cars I have tuned in the past, unless you do something tricky like pulling fuel when IATs go low, you have to compensate in the MAF or VE table for when the psi/KPA hits a certain point by actually pulling fuel out as the meth adds a ton of fuel. If you do not pull that fuel out then the motor will be quite rich..at least with the kits I worked with. So if the meth is not there adding fuel, then at that point the motor leans out and goes boom.

Now if you had hptuner or EFI live or whatever, then you could flash back and forth yourself.

95bowtie

So basically your saying if I have it tuned on 93 and it holds a 10.50-11.00 afr wot and I add a meth kit later for safety the meth leans it out?

I was figuring adding meth to a already tuned setup without meth would make it more rich....

Sarg

iTrader: (6)

No if it is tuned for meth and you don't have it it goes lean. If it is tuned for 93 and you add meth it goes rich.

denmah

iTrader: (2)

yes, we have run 18lbs on stock shortblocks, and 20lbs on stock shortblocks with no methanol just pumpgas, i would say you just cant be as pushy and watch those inlet temps

methanol is an easy solution i think

rotary1307cc

iTrader: (5)

Egts will be ridiculous

milkplus

iTrader: (3)

I have no idea what I'm talking about but wouldn't rich+water/meth cool it down? You could run a smaller orifice, it doesn't have to be a firehose.

I'm interested how you would tune around meth that's kicking in with a hobbs switch.

Sarg

iTrader: (6)

Sure, it would, but at the same time, give it too much and it will not be able to burn efficiently. Personally I feel that in order to get any real boost from the octane and cooling of the methanol you will need to be injecting enough that it will drop the air fuel at least a point or more.

I am not planning to use meth, but I have seen some threads (here or hptuners) I forget that discuss using the IAT tables to pull fuel and ground out the sensor when meth is activated. Again I have not tried this.

On other platforms I have just tuned the area of the tables where the meth comes in to pull fuel out. This is one of the dangers of meth. If it should clog or stop spraying you will lean out. Just another reason that despite the failsafes available I choose to use e85 instead or just do a conservative pump gas tune.

Sarg

iTrader: (6)

When? Without meth on pump gas?

Nitroused383

iTrader: (10)

It isn't hard at all to setup several fail safes on the stock ECM. Overboost protection and a meth fail safe can easily save a motor and in my case has several times. The worst thing you can do is tag the factory rev limiter while spraying meth. I prefer to use timing for a soft rev limit over the stock fuel cut.

95bowtie

Okay that's what I thought, your post before this had me confused a little I must have read it wrong.