Time to go Stage II!

[Alky V6]

You're probably not going to want to hear this, Norbs, but you made me curious about what might happen if I were to fix the liquid intercooler and just run plain water in it. No icing. I ran the sim using 80% intercooler eff and a turbine nozzle diameter of 2.3". Stroke is still 3.06".
The output was 1,565 bhp by 8000 rpm. This is assuming that the advertised rating of the compressor (1650 hp) is accurate.

 

[norbs]

Norbs, could you clarify the above quote. Do you mean air to air at the beginning of the sentence and then air to water for the 80% eff?

That is correct air being lower efficient and water the higher numbers.

 

[Alky V6]

The latest sim I made with the 80% intercooler efficiency caused some problems. The increases in performance with the better intercooling pushed cylinder pressures beyond my set limits. An intercooler efficiency of around 55-65% keeps performance and cylinder pressures more under control.
Increasing intercooler efficiency had about the same effect and complications as you would have by increasing boost levels through the midrange. Cylinder pressures just got out of hand, almost all the way to redline.
An option would be to run the intercooler at 80%, but control boost levels through the midrange. Hmmm. I'm not used to having exhaust energy in reserve. The problem with this strategy is, if boost rise was not properly controlled, it might get expensive. Boost control, fueling and timing would become very critical through that particular section of the rpm range. This is all assuming the new engine configuration can spool this turbo as well as the sim is predicting. I have to think that this Stage II configuration, even with the larger cam, will spool this 91mm a little better than the Stage I configuration did.

 

[norbs]

Donnie are we talking efficiency as in pressure drop or discharge temperature, causing your issues?

 

[Alky V6]

Donnie are we talking efficiency as in pressure drop or discharge temperature, causing your issues?

Discharge temperature. A colder, denser intake charge contains more air and fuel. More mixture gets packed into the cylinder creating higher cylinder pressures. It's not a drastic rise in cylinder pressure, but when you're already riding the edge, that large of a change in intercooler efficiency will put you over the edge.
The lower charge temperature does help with the knock limit number, but you have to consider the mechanical limits of the machine, too.

 

[Alky V6]

Watching cylinder pressures is more critical with the short stroke. The shorter stroke makes up for the lack of stroke with more cylinder pressure.
That's how you can have the same HP level with different strokes. You trade stroke for more rpm and cylinder pressure.

 

[Alky V6]

The slower piston speed of the short stroke allows more avg cylinder pressure to build.

 

[norbs]

Donnie, I' have never seen too much inter-cooler hurting a combination, you have a very different approach to all this. Anyone else have any feedback on this? I know your putting all this in the sim, but in real world it seems radically just wrong to reduce inter-cooler effectiveness?

 

[Alky V6]

Donnie, I' have never seen too much inter-cooler hurting a combination, you have a very different approach to all this. Anyone else have any feedback on this? I know your putting all this in the sim, but in real world it seems radically just wrong to reduce inter-cooler effectiveness?

My first alcohol engine didn't quite have the fueling right, but it is interesting that the run that the engine decided to give up the ghost, was the one run I decided to ice the liquid intercooler. Engine went into preignition and a few rods exited the block. I was getting away with the tuneup I was using right up to the one run I decided to ice the intercooler.
I do have a little real world experience with most things I bring up. How do you think I established my cylinder pressure limit? From real world experiences.

 

[Alky V6]

I know most people think it's silly to spend the time to come up with a sim that attempts to closely match an engine that you're planning on building, or work to match a sim to an engine that you're already running, but what most people don't understand is that if you have a problem with an engine, it's a wealth of information to be able to go to the sim and see what might have caused the problem. Once you think you've identified what caused the failure, you are now armed with that new bit of information that you can use with your next build, and run your next engine knowing what sort of issues to steer clear of.

 

[Alky V6]

So when you hear of someone leaving the line with 40+ psi boost at a relatively low rpm, with a nitrous shot on top of it all, and a rod folds, I think I know what happened.

 

[Alky V6]

I'm not going to say that the cylinder pressure limit that I've set for myself is the mechanical limit of the machine. But, at high cylinder pressures, having the tuneup dialed in becomes extremely important. There is very little room for error. If a tuneup does happen to be on the edge (lean best power), something as seemingly harmless as an intercooler efficiency change can push that tuneup over the edge. If the tuneup happens to be pushed to preignition, which in some circumstances with methanol is not that hard to do, well, then the mechanical limits of the machine will be found out. Believe me.
Norbs, are you understanding this? Are you aware of how the change in intercooler eff can change the tuneup?

 

[Alky V6]

If one were to assume that the FI91X compressor capacity is only capable of supporting 1550 hp, and I think this is a good assumption, then the output of the engine may end up being about 1425 bhp at around 40 psi boost. About 1210 rwhp. This should produce a 5.2-5.3 1/8 mile ET and 8.1-8.2 1/4 mile ET.

 

[norbs]

I'm trying to understand but I need some time to absorb your info.

 

[Alky V6]

If you have any questions, just ask.

 

[Alky V6]

A curious bug just crept into my mind. So far, the sims I've been performing on the Stage II config have shown a tight correlation between the capacity of the compressor housing and the predicted output of the engine. What if I start plugging in turbos larger than the 91mm? Will output increase? At what level will the output plateau? Heck, we've got nitrous to spool the thing. We can throw anything we want on the sucker.

 

[Alky V6]

Well, it looks like between 1400-1500 bhp, depending on the turbo, is going to be it for this combination.

 

[turbobitt]

Well, it looks like between 1400-1500 bhp, depending on the turbo, is going to be it for this combination.

I think it will do better with your turbo and high boost, say 45+. Guessing about 100 HP on the table.
Allan G.

 

[278cikiller]

Donnie! You are over the Top with this sh!t.

 

[Alky V6]

I think it will do better with your turbo and high boost, say 45+. Guessing about 100 HP on the table.
Allan G.

I'm sure you're right. Unfortunately, for the turbo I'm using now, there isn't a smaller a/r ratio turbine housing available. I suppose I could see what Bullseye could do for me, if I find I want more after getting it running. Or, I could inject nitrous/methanol directly into the turbine housing to create extra exhaust energy to drive the compressor harder. That nozzle is already set up and being used to spool the turbo. I could simply keep that one nozzle on to feed the turbine housing for the duration of the run.
But the real limiting factor is going to be the cylinder pressure. Not so much a problem with the stroked configuration, but then max rpm becomes an issue. I want to build a screamer.
What I'd like to do first is get the engine running and tuned to the limit of what it can do up to 40 psi, get some track results, collect some data then decide where to go after that. It could very well be that my chassis will have a hard enough time as it is with the projected 1400 bhp.