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Discussion Starter #1
This has been nagging at me lately, and I was hoping you tuning gods might be able to answer it for me. Recently I see a lot of people running a lot more boost(10psi and over) (on stock motors) than I have seen in the past. My diablo chip from tom is like 3-4 years old, and has so much timing in it that I can't run over 8.5psi on 91oct with out fear of pinging and knock. So basicly my question is this: is it better to have more timing with less boost, or more boost with less timing? Or, do they come out to about the same thing?
 

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Good question. I ask myself this daily as we're developing our blower kit stages with intercooler. Personally, I like more boost and less spark. More spark and less boost does work, too. Sometimes, though, on Cali 91 octane it can really suck. Guys with 94 octane are lucky.


Load plays a huge roll in deciding what to do IMO.
 

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Oh, lemme bust a Nazthug here. I do find that with our blower kit it's better to run more boost and less spark than less boost and more spark. The peak numbers are really close, on purpose per the programming to be safe, but most of the graph before peak clearly shows that there is a benefit.
 

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Discussion Starter #4
so what you're saying is that more boost gives you better results throughout the powerband? Yea, the safety of having less spark for the street is greatly desirable. Thanks for the quick feed back Randy.
 

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would the same thing apply to turbo's as well? I've been thinking about upping the boost lately, but I'm worried about deto past 10 psi.
 

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so what you're saying is that more boost gives you better results throughout the powerband? Yea, the safety of having less spark for the street is greatly desirable. Thanks for the quick feed back Randy.
That's what MY tests indicate, yes. Of course Cali 91 octane plays a big role in this, with higher octane you could safely run more spark and the difference wouldn't be as much.
 

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would the same thing apply to turbo's as well? I've been thinking about upping the boost lately, but I'm worried about deto past 10 psi.
The same would apply to turbos, I'd rather run more boost with less spark. Unless you can verify your programming is safe and are able to check your A/F, I would be wary of turning up the boost without tweeking the file.
 

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yeah, I was definitely going to get it dyno tuned if I was going to up the boost, just wondering if it would be safe for my application.
 

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Discussion Starter #10
I did have another question while you're here Randy...When you have a built lower end in the car, is that just for a higher total output for the engine? I'd imagine the same pressures would cause ping with a built engine, and with a stock engine (keeping compression the same)
 

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A built bottom end if built properly will be stronger. The rods for example, are powdered metal on the Zetec. With a built bottom end, you'd address that and go with stronger rods. And you could step up to higher quality forged pistons, too. However, I'd lower the compression if I did pistons. One of our customers has 9:1 comp pistons and I really thought it was a great choice for FI tuning. You could get a better crank, but that is not needed as much as rods and pistons IMO. And using ARP hardware whenever possible is a good idea.


For high revving, a modified or better oil pump may be needed.

I like the idea of the Cosworth CGI block that we sell, personally, along with everything else I noted.

A built bottom end is just better and stronger.
 

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Troy you will get detonation in both motors at the same timing and PSI if the both have the same compression. The only differance is that the built motor(rods and pistons) will be able to tolerate it for a long time then the stock. So say your at the point of detonation and you buy some bad gas your stock motor will only be able to put up with that for a very short time before a piston or rod breaks, were as the built motor might be able to run the tank dry and not suffer any ill effects. Only compression ratio, timing, octane and PSI are going to allow you to run more of each. It is getting the combinations right that makes the most power without blowing up the engine.
 

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One thing you can do with centrifugal blowers, over a turbos, is that you know exactly where what levels of boost will be present. And since there's zero chance of ever having more than a few pounds of boost down below 3500 or so, you can tune more like it were NA down low and then boost up high.

This method gave me 25+ more ft/lbs of torque down "low", for normal driving. Which is a *very* noticeable difference.

BTW- Great question!
 
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