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Discussion Starter #1
Hello, I was playing with the idea of increasing my boost on my procharger but its not really worth it at the moment if it requires me to get a re-tune. I run on e-85 and have plenty of pump with 2 400lph fuel pumps so I was thinking of increasing my base fuel pressure to compensate but I don't think that will work since I have a speed density tune and my fuel pressure regulator is boost referenced anyway. I have a wide-band in the car so I can test and play with the settings.

I made 540whp with the 4.25 pulley on completely stock motor. At ~85,000 miles would I have to worry any more about reliability with the 4.00 pulley especially since I rarely get on it? I drive it a lot, mostly highway and daily drive it although its not my daily driver.
 

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It is very possible you could go from a 4.25 to a 4" pulley without a retune. It's also possible your fueling would be off. I just went from a 4" to 3.9" spinning to about 6800 rpm on sbe ls1 and only made a very small adjustment to my VE table to dial in fueling. It wasn't absolutely necessary and it wasn't enough to hurt anything. I only run 60% ethanol and still have such a huge tuning window that a little off on fueling isn't going to hurt anything. Since you have a wideband you can at least keep an eye on it and see how it looks. It's really worth logging to verify any time you make a change though. Do not compensate with fuel pressure a change in fuel pressure would cause more fueling issues than the small pulley change. Even if you were lean in boost and compensated by raising fuel pressure then you would be rich when not in boost.
 

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It's possible if your tuner made a safe zone past your current Boost pressure in the chance it goes up due to elevation and changes in air temp etc...

If you have the ability to call him/her, do it. Let them know what you're looking at doing.

Since you're boost referenced, that's great. I'd imagine the tuner left it safe above your current tune and going down that small of a size on the pulley is not that much. Good luck.
 

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Discussion Starter #4
Cool, thanks for the replies guys! Out of curiosity what would you say the ideal wot fuel ratio is? My fuel regulator might be slightly off from when I recieved my tune. I'm currently seeing 11.5.
 

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11.5 on the gas scale with E85 is typically what people aim for. E85 has such a big tuning window that there isn't much gain from high 10's to high 11's for afr on the gas scale. I had a plugged post pump filter when I first got the car back out last spring and saw afr's in the low 12's in boost and still got no knock retard and no signs of detonation on the plugs. E85 is very forgiving.
 

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Discussion Starter #8
Results from the pulley swap yet?
Yes, actually. I did it maybe last week. I haven't hit the rev limiter yet but I got up to 6k rpms and the a/f ratio was good. Rich if anything. I heard 11.1 for e85 on the gas scale is good since e85 likes to be a bit richer. So far I noticed about 10.8 under wot.(reading from driver side exhaust). I don't get on it that often, I mostly daily drive it and wanted a little more grunt for passing other cars on the highway in the higher gears.
Thanks again for the help everybody!
 
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