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Old 09-12-2012, 04:04 PM   #11
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Member#: 95901
Join Date: Sep 2005
Chapter/Region: SWIC
Location: Las Vegas, USA

Your browbeating, grandstanding, sarcasm, and bluster do not prove your point. While you demand data from us, why can you get away with "search the forums" and "I did 20+psi on a td04 first" as data?

My evidence comes from books. I should write hypothesis instead of evidence. Technical books. Greg Banish's Engine Management:
Advanced Tuning
; Jeff Hartman's How to Tune and Modify Engine Management Systems. But If you like forums here's a thread on TurboBricks, one from EvolutionM, a thread from AEMPower

The meat of what Banish and Hartman write is that there is an AFR that produces a maximized torque curve a particular forced induction engine can produce on a particular fuel (e.g. 91 octane gasoline). This can vary a bit from engine to engine. But it is somewhere between 12.8:1 and 11.5:1. With forced induction this leans toward the richer side, because it's safer. Naturally Aspirated can be leaner. But both are within that 12.8:1 and 11.5:1 range. Now with your AFR target locked, tune your timing and up your boost til it's not safe anymore.

I know, here at Nabisco, the groupthink has everyone picking the boost target first then dumping loads of fuel in to to prevent knock and backing off the timing. The extra fuel at that level (10.0:1 - 11.5:1) doesn't make more power, it slows the in-piston burn (flame speed) thus preventing knock that you get from picking a ridiculously high boost goal beyond the efficient range of the turbo. The extra fuel is just slowing the flame front and reducing cylinder pressure, keeping knock at bay. Reduced cylinder pressure = less torque. But bragging, "I'm boosting 22.5 psi!" sounds cooler than, "I'm max'n' torque at 11.8 A/F!"

Here's a video from Innovate Motorsports, maker of the LM-1 wideband, o2 product about A/F Ratios and why too rich costs power and wastes fuel. Caution: heavy product promotion.

From Hartman's book page 132:
At high loading and wide-open throttle. richer mixtures give better power by making sure that all air molecules in the combustion chamber have fuel present to burn. At wide-open throttle, where the objective is maximum power, all four-cycle gasoline engines require mixtures that fall between lean and rich best torque, in the 11.5 to 13.3 gasoline range. Since this best torque mixture spread narrows at higher speeds, a good goal for naturally aspirated engines is 12.0 to 12.5, perhaps richer if fuel is being used for combustion cooling in a turbo/supercharger engine.
The tuning philosophy I subscribe to goes:
1. Dial In MAF Table
2. Pick AFR (11:76:1 for me).
3. Pick target boost based on the turbo's compressor flow map (19 psi, vf-35 UK STi turbo)
4. Tune Waste Gate Duty Cycle to maximize spool up/prevent surge/prevent over boost
5. Timing Table Tuning Time
6. Tune Waste Gate Duty Cycle part II
7. Timing Table part II
8. Brag on Internet
9. Install new part
10. Repeat

Here's the main problem with our argument. Neither you, nor I, and probably no one here, has the data to prove which tuning philosophy produces more torque. That requires two different tuning maps and dyno sessions on the same car with the same parts on the same dyno under similar atmospheric conditions. That's some coin we'd both have to shell out to get that data. Which one of us will pay a tuner to finalize one map, then tell them to bin it and do it again but another way 'round?

But until you or I do that we can't prove which makes more torque and therefore more power. Right now you've got "Nabisco says" and I've got "Books read". No data for either point.

We can agree about one thing: We both want to maximize torque from our setups.
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Last edited by 68Cadillac; 09-16-2012 at 11:49 AM. Reason: engrish be hard, yo
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