ss4luck

my fiancé bought me a 3.4 pulley for my V3Si and I was talking to my tuner today and he was worried about safety on 91 Octane.*

leo12

With a good tune/ tuner and meth you shouldn't have a problem
Am at 17 pounds boost for couple years with out any problems

ss4luck

That’s what I had thought. I’m gonna call him back today and discuss with him. He’s a solid tuner so I’m not worried about the tune being off, but when he said “that’s a lot of boost for 91” it caught me off guard

romandian

17 psi on a ls6 and 91 octane? how much meth and what timing?

stevieturbo

You say SBE....but is this also stock compression ?

You also dont mention how much boost you're aiming for ?

The meth can go a long way to supporting poor fuel...but how much are you willing to risk, as no matter what anyone else says, with stock pistons etc there are always risks.

Water_Walker

25 k motor here , added a&a 3.4 pulley, cam headers tune. 611/532

Last 1500miles with 9lbs boom!

ss4luck

Chrisrokc

General rule of thumb, if the tuner hasn't done it before, pass. I was going to throw a 3.4 on her and retune it with BlownBlueZ06's help.

Also...Let me know if you need any help getting your HPtuners software working. Might save you some $$$.

BLOWNBLUEZ06

My experience has been the following: I've seen people blow up on 8psi boost before the car leaves the shop (not mine) and I have tuned some that make 22+psi boost, get driven hard at the track for 3 years before they let go. What I share with people I tune for: I've seen stock motors break. Every motor has its breaking point and as you increase power, you're moving closer to that line. It's heat, pressure and time that gets them in the end. Knowing that stock motors can break, any increase in power decreases the life expectancy of the engine. If you're not willing to deal with a failure, don't start playing this game. It can be incredibly fun and rewarding, but it's expensive and addictive for most and can also be the bane of your existence. There are a number of things that can be done to mitigate possible failures. Running meth injection or E85 and proper tuning are on the top of my list. Just because it makes a good # on a dyno without breaking doesn't necessarily mean that it'll stay together or run accordingly at the track or on the street. At a certain point in power, I recommend the vehicle owner get a wide band, HP Tuners and learn some basics so they're not held hostage by anyone to make and keep their car running its absolute best.



Bret

ss4luck

Im aware of the dangers of increased boost and breaking points, I have begun a parts stash for an LSX 427 to go into the car at somepoint in the future, weather that be because hte LS6 popped or because the new motor is together and 4 digit HP numbers are calling my name. The car does have a wideband and runs a single meth nozzle and 100% m1. I would love to know what i am doing tuning the car, but im not sure i would know where to even begin researching for that. Ironically you were the last person that tuned the car.

JoeNova

I would consider switching from 100% meth to a water/meth mix at that level.

BLOWNBLUEZ06

JoeNova

Water cools far better than methanol could ever hope to.
Charge air temps have a lot less to do with preignition and detonation than people think. Methanol does a slightly better job of cooling charge temps because it evaporates more readily than water, but water absorbs twice as much heat energy as methanol when it is converted to gas. It also takes twice as much energy to raise the temperature of water at room temps as it does methanol. Water wins in the cooling department, hands down.


The second problem is that methanol still burns. It might cool charge temps slightly, but its still going to ignite and produce heat. The water will not. Methanol's only benefit here is that its 'slightly' cooler than gasoline. It will still force heat into pistons, it will still cause rings to expand. For guys running cast pistons and tight ring gaps, water wins here too. During compression, the temperature of water is raised high enough that it flashes to steam before ignition. This removes so much heat from the cylinder that it makes detonation or pre-ignition almost impossible. Methanol is still able to detonate in this situation. It will remove some heat, but if it has evaporated, it takes far less energy to raise its temperature, and therefore its still very possible to obtain pre-ignition temperatures during compression.


So for guys running cast pistons that need to stay cool to prevent cracking, and tight ring gaps that need to stay cool to prevent expansion, water beats methanol every time.

If you have forged pistons and preferable ring gaps, methanol is the way to go.
If you are out of fuel injector and need supplemental fuel to make more power, methanol is the way to go.
If you have a wild combo but the CFM flow of your heads isn't up to the task, methanol will cool the charge air better and allow more power for a given port size.

But for pure cooling purposes, water is king.

JoeNova

To put that into real world results:


My Nova has a 10:1 5.3 in it with a billet S480.
I had a wastegate failure last year and drove around all day beating on the car without noticing.


At least 6 times that day, I overboosted the stock shortblock to ~40 lbs, running 15:1 - 17:1 on the AFR scale with my logs showing 160-180% duty cycle. None of the logs ever showed a hint of knock.


My engine is still strong. I just recently did a teardown after 6000 miles to see that all of the rods are straight, cylinder walls are good, pistons are in perfect shape with zero signs of detonation. I attribute it to the fact that I run 70/30 water/meth and that the evaporating water draws out SO much heat during compression that I was never able to push compression temps over the knock threshold.

typeav

http://www.snowperformance.net/category-s/187.htm

9. What ratio of water/methanol is recommended?

• A 50/50 ratio is recommended. This has been demonstrated to be the best for charge/air cooling, excellent detonation control, and safety.

• Ratios of anywhere from 30% to 50% methanol work well and deliver excellent octane gains and cooling.

10. Can I use pure methanol?

While all components of Snow Performance systems are designed to be able to handle pure methanol, it is not recommended for a number of reasons.

• Safety: Pure methanol is easy to ignite witha low 140F degree flash-point and burns with an invisible flame.

• Performance: Water absorbs almost twice as much heat as methanol in the intake and inside the combustion chamber. Water cannot be flash-ignited, so has what is almost an infinite octane number. In the government studies for WWII piston-powered aircraft, 50/50 water-methanol was found to be the best fluid to use for auxiliary fluid injection.

stevieturbo

Ultimately what is better ??? Is entirely down to each user to test on their application for whatever their goals might be

typeav

This is all common sense but if I'm wrong please correct me so I don't have to keep spreading misinformation.

Manufacturers are telling you already which one is better, you need both water to cool down and meth for octane. Users can use whatever they think is right in their mind but many hours of test have show real results.

If you using pure meth you need to understand that is not for cooling and is not that safe because it easy ignite with a low 140F degree, taking this point into consideration you are better off with high octane race fuel or another source like e85

stevieturbo

There is no generic one is better than the other as a final statement for all.
In no way whatsoever is that the case. So a manufacturer cannot tell you, and nobody else can tell you. Everyones needs are different, everyones goals are different....and indeed everyones engines are different.

If every single person wants to find what is "optimal" for them....they need to test. Anything else will just be a best educated guess....and usually that's a hell of a lot cheaper and easier than hundreds of hours of dyno time to optimise with testing dozens of different mixtures and setups.

Water and methanol each have their own pros and cons, and even those will depend how they are used and even more so in what quantities.

And it's pointless saying you're better off with better fuel, race fuel etc....when clearly it is a pump gas car.
That's like saying you're better off with a fully forged LSx...when it's a stock engine build.

typeav

you are absolutely right

Julio

Boiling is 160 on methanol. It won't ignite at 140F degree's. Just get a sterno for heating food at the buffet.. thats alcohol.. you have to put a match to light it up. A rag with gasoline on it will ignite at way lower temps than a rag with alcohol on it.

Alcohol cools just fine, pour some on your arm and blow on it

Agreed, there is no blanket statement one liquid is for all, granted we are on a C5 forum with cars that typically are fuel deprived, MAF's that are pinned above 540 to the tire, run intercoolers so IAT's are lower, are owned by folks that dont want to constantly be messing with tunes, have intake manifolds that are unequal length from throttle body to cylinders, etc.. hence why most use 100% meth. Not that its the best for every application, but it sure does make tuning easier as it ignites and doesnt blow the flame out or have distribution issues when the volume goes up.

Single plane intake, non-intercooled, adequate fuel system, love messing with the tune(winter vs summer), etc.. water/mix is fine. Local customer on an NA Vette made more gains using mix then straight alcohol, and there are those that need the fuel to make up and no comparison.

Hope this helps