Rich, what ratio of water to fuel were you using for that setup, at the time you experienced the detonation?

 

Arnie: to be honest, I am not sure there was detonation. What I am sure of is that the pistons were trashed!

I was using 3/1 water to methanol.

Rich Krause

 

I used it on my 401 motor. anyway, if anybody wants a DIY kit, I have a high pressure pump, a regulator, and the windshield resevior converted for a tank(nipple added to bottom etc). new this stuff cost 150+. ill sell it all for $65 shipped

worked great on my 401

 

Let me rephrase that ? What ratio of water to gas were you using?

 

Sorry, not enough data to figure it out.

Rich Krause

 

The best way to deal with detonation is lower compression. It's also very important to have the car tuned. If you switch to a forged piston you gain alot more strength. The hypercrap pistons that are in the stock lt1's will not take much. 8#'s max of intercooled boost. I don't care what anyone says about those hypercrap pistons. You will destroy them. Thats not an opinion, thats a FACT! Talk to the many people who have joined the blown motor club because of not listening to others who have had first hand experiences.

 

As Groucho Marx said, "I wouldn't want to join any club that would have me as a member..."

Well, I'm at 5800 ft altitude and the air is a lot thinner here. Additionally, we're dropping the CR to ~9.2:1 and third, I'm trying the alky/water injection. I've got a day on the dyno with a great tuner who's been running SCs here for quite a few years and is a former engine builder for Calloway. I understand it's a gamble and according to everyone here, not a very good one. That's OK with me...

I've definately got plans to build a bullit-proof 355 and it won't take forever to stick it in when this one goes. I just didn't want to build a low compression blower motor and go slower for the next six months while I waited on the money for a blower. If worst comes to worst, I've got another '95 Z I can drive if this one bombs.

I appreciate everyone's advice and experiences. No one has really talked about how much CR plays a role and what boost 9.2:1 can be pushed to with the stock bottom-end. No one has addressed the altitude differences. I suppose I might be trying something a little different than others here and who knows, it might be worth trying...

Then again, I'll probably end up joining the "blown piston" club and adding my dumbass experiences to the next guy's post...

 

The altitude will make your blower work harder. Which causes your blower to be less efficient at a given boost level.

The CR should help with the detonation but the most important thing is going to be tuning. Do you have a wideband Lt1_edit and some sort of datalogging.

I would run a logger full time so you can see what went wrong when the motor fragged. <g>

 

I can understand the less efficient part, but how can the blower work harder? It only turns so fast based on the engine RPMs...

Please explain.

 

The altitude thing is pretty simple for NA cars. All else being equal, the air pressure is lower at higher altitiude. Lower air pressure means that for a given volume of air the motor takes in, the mass of oxygen will be less. Without any changes in setup, the volume of air is fixed for any given rpm (at WOT). So, there is less oxygen and the motor will make less hp.

Turbos are different, as many of them produce "excess" boost, which is bled off by a wastegate. Depending upon the capacity of the turbo and how the wastegate is controlled, there may be some compensation for altitude and relatively little loss in hp. Of course, this only works to a point and very thin air will cause a drop power output even for a turbo car.

Centrifugally SC cars will pretty much lose power in proportion to the air density, just like NA. If the blower is not already flowing at maximum, increasing blower speed can partially compensate for the decrease in air density. However, the extra power it takes to drive the compressor faster will prevent all of the "lost" hp from being regained.

The additional hp from nitrous will not be influenced by altitude. Of course, the portion of engine hp which depends on NA operation will be decreased.

Rich Krause

 

Thanks Rich. How do you think it will affect the effective boost/CR in relation to my stock bottom-end? Any ideas on how to quantify the difference at altitude. Guesstimates accepted. For example, if a blower is rated at 12#s at sea level, would that relate to 11#s at 5000 ft altitude? I realize you probably don't have a conversion for something like this, I'm just trying to figure it in relative terms... Is the compressed, thinner, air less combustible due to less o2?

 

Well guys, my decision was made for me...

In pulling the heads, my builder found a very weird sludge in the heads. It looked almost like someone spiked my oil... No coolant signs, but it was amazing the bearings had held up. Definately not the way a 77K engine should look...

Anyway, we're pulling the engine tomorrow and I'm going to have the bottom-end forged and getting a custom blower cam. Mo' money...

The good news is next month I'll be worring about blowing the tranny and rearend instead of the pistons...

The abuse never ends...

Thanks for all your advice. Damn, it looks like I'm going to take it!