Another thing to remember, not just for this build but all builds in general, is that power is easier on parts than RPM. For example, the same rods that might be good at 700hp @ 6000rpm might only be good for 550hp @ 8500rpm
Another thing to remember, not just for this build but all builds in general, is that power is easier on parts than RPM. For example, the same rods that might be good at 700hp @ 6000rpm might only be good for 550hp @ 8500rpm
Keith Tanner wrote: You gave a goal, I gave my opinion on how to reach it! As we say when troubleshooting at work, what's the REAL question?
Yeah, I realized I wasn't asking well.
Since I have dual goals (compete at the Challenge, AND build a good car with value for future events), I have dual questions:
What's the best way to build a competitive reliable car on a budget? (I'm asking this first, because I know it is the harder question), and
How much can I get out of it for a short term? (Challenge competitve). This one I know how to do- I already know how to boost it too high, and throw cheap parts at it.
Keith Tanner wrote: We've done some testing on various rubber parts and fuel components with E85. They don't all fare well.
Good word.
I also know the next question I am not asking...
"What is it I am trying to be competitive at doing?"
Well, that one is harder to answer. I do not live anywhere near any viable racing venues, and will never be a great driver. In the rural South, a fast Miata is pretty worthless.
Emod? Track days? Spec Miata? SuperMiata? I dunno- Still working on that. I am taking opinions. 
It won't be a drag racer or a dirt track car. 
If I was doing a budget turbo build, I would be pretty comfortable working with an engine with a proven bottom end, and not look to obsess on making it stronger for the sake of the turbo. As Corky Bell puts it in "Maximum Boost", "the increased combustion chamber pressure due to a turbo, and thus the power load, will have only a moderate adverse effect on the structure of the engine." Certainly, I recommend reading the entire book! 
Heat management, obviously, should not be overlooked.
Even the supposedly fragile Mazda rotary can stand 20 psi on stock internals without coming apart. Ask me how I know!
I would recommend looking further afield than Corky Bell's book.
The increased power load definitely has an effect on the structure of the engine, but it's the shock loads of detonation that bend rods and blow holes in the piston (*). So tuning and good fuel goes a long way. E85 is a big plus. We know the Miata engine is good for long-term use at about 250 rwhp, but if you want to run 300 then you're going to have to upgrade the structure.
As for SVreX's car - we'll need to make at least some assumptions to generate any useful info. Give us a goal. Say, a car that will withstand 20 minute track day sessions in Southern heat and will survive for five years. Or a car that will work well as a daily commuter. Or a kick-ass autocrosser. The answers will be different. Otherwise you'll get random bits of advice that may or may not be useful.
Keith Tanner wrote: .......a car that will withstand 20 minute track day sessions in Southern heat and will survive for five years. Or a car that will work well as a daily commuter. Or a kick-ass autocrosser. The answers will be different.
How much different? If I choose the turbo route over a motor swap (eventually) those are almost exactly the parameters I'd wish for.
**note: locally kick ass autocrosser and fairly good daily commuter/weekend toy.
An autocross build is going to prioritize response and light weight over pure power. A track build is going to focus on heat management but can have a peakier powerband. A daily commuter is going to need a smooth powerband and the ability to switch to E10 instead of E85 - or ideally, respond to an ethanol sensor.
You can cover all the bases, but if you have budgetary limitations you need to pick and choose. You might spend your money on an ethanol sensor instead of stronger rods, for example.
In reply to Keith Tanner:
Yes, I understand the goals determine the recommendations. I am not yet ready to decide that. The racing goal is part of what I am researching and learning about.
I will probably never have the opportunity to race it myself. There are simply no opportunities in my area/ my life.
But I want to build something of value. Something that is appealing to a broad range of people on this board.
It will not be a street driver. It will be a kick-ass autocrosser that can also lay down a reasonable 1/4 mile, because that is what the Challenge is. I am confident in my abilities to build this part (I've already done it). I understand suspension, setup, MS, and the basic formula.
I am also confident in my abilities to build an awesome radical body- think Emod or equal.
I am trying to decide what I am capable of, then self-impose an additional layer of guidelines and restrictions- I want to build to a class, and build a car that can be converted easily after the Challenge to something that is not a Frankenstein's bride, incapable of serving any other purpose. I want to build a real dedicated race car. It's a personal challenge.
Maybe a track car. Maybe a dedicated autocrosser at a high competitive level. It's not a decision I have made yet, but am willing to listen to ideas. Give me some suggestions.
I know the vagueness is killing you.
SVreX wrote: I want to build to a class, and build a car that can be converted easily after the Challenge to something that is not a Frankenstein's bride, I want to build a real dedicated race car. Maybe a track car. Maybe a dedicated autocrosser at a high competitive level. It's not a decision I have made yet, but am willing to listen to ideas. Give me some suggestions. I know the vagueness is killing you.
Pick a class, then we can give you some concrete advice.
I will say that I have yet to see a cheap, reliable turbo miata on track. Cooling is one issue. Keeping the manifold from cracking is another. Keeping all of the turbo bits bolted together after judicious heat cycling is a third.
It's doable, I'm just not sure it's doable with an $800 budget.
How about stock bottom end, E85 and water/method injection and IC sprayer. Knock down those IATs, cool the charge and prevent detonation.
E85 makes the water/meth injection irrelevant. It's magical stuff.
So, vague suggestions for a vague result: the same ones I've given already. Concentrate on the head because it's zero cost. New bearings and rings. Get good rods if there's room in the budget after machining. Then concentrate on the fuel system, ECU tuning and heat management.
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