If you're running anywhere between 8-12lbs. boost FI, what should your target AFR be for say a 100 shot of nitrous? I'm hitting an AFR right now of 11.8 - 12 with 8# of boost. I do have a wideband tied into my EMS, and the J&S Safeguard Knock Controller to help keep me detonation-free.

Jim

 

is it a built motor or stock bottom end?.... is there a reason you dont just up the boost?... the nitrous will help keep it cool to an extent but too much power and it'll heat things up alot more than usual, you want to run rich to be on the safe side, but you need to adjust your nitrous jets along w/ the fuel settings, alot of people think bigger fuel jets will make it richer but it will also make more power too so you could end up running too much power and if the engine cant take it or the tune isnt perfect things wont be pretty, also if your adding alot more fuel anyway the jet chart could be off so I would start off small on the nitrous side... I say dyno(mustang) tune it w/ the nitrous and shoot for mid 11's

 

Depending on what dyno you use I like to see between 11.7 - 12.2 range. Again dynos are different in the way they load the car

 

Thanks, guys.

"Is it a built motor or stock bottom end?.... " It's an all forged 383 bottom end, ARP main studs, GMPP 4-bolt block w/half fill of Hard Blok. Fluidampr.

I'm pretty much getting all the boost I can out of the Vortech V-2 S-trim. Around 8# max after FMIC and throttle.

I have the Progressive controller so I can ramp it in instead of a hit. Window switch for the 2nd stage.

I also have a completely seperate fuel cell, pump and bypass regulator for the squeeze, so I can run leaded C16 or a meth/C16 blend. Dual Cheater plate system. I'm gonna start conservative with a 50 shot, and go from there.

Jim

 

c16? you're gonna kill your 02 sensors.

i would think the wet kit would keep the air fuel right, you can always go up on the fuel pill..

 

You're all set man! I was going to ask what octane you were running til I saw your last post. With just the pump gas I would've said probably stay in the 10:1 range, but with the C16 you're in good shape. I always suggest for people to run a dedicated fuel system for their nitrous, and there are big advantages.
Now I haven't tried it myself, but have multiple reports of the methanol not working so well when run through the nitrous system. It may have to do with methanol requiring a bit of heat to vaporize. If you run one of those methanol injection kits upstream (before) your nitrous is injected, then there's a good chance you'll have better results all around.
I also don't know a lot about mixing C16 with the methanol in a tank. It's possible that the mthanol could change the structure of some of the gasoline or have some other problem I can't imagine. It might be fine, but I'd probably still keep them separate.

With the higher octane you should be able to run much leaner. I wouldn't be nervous about mid 12's, but remember that the heat will build up near the end of the 1/4 mile so you have to manage that. When running lean, the sparkplug builds more heat, so a cold racing plug may be good insurance. Some people run without a thermostat so the coolant doesn't build so much heat by the end of the track. If it's possible for you, adding a VSS vs fuel-multiplier table is another option since you actually only need the richer AFR's on the big end of the track. VSS being vehicle speed sensor, or speed. I don't know what EFI control system you use, but the older ECM's allow this change.
I call it dynamic tuning as the AFR richens with speed/load. With this you can see 13:1 in low gear with no problem.
In case you're wondering why you would want to do that... well running pig rich, or even running higher octane will make the engine lazy in the lower gears. Your piston speed is fast, yet the burn is too slow & that's not a good match. Of course you need more fuel as load increases.

IMO this is why a lot of boosted cars run their best in high gear... because of the conservative tune. That's just what I think.

 

I'm using the Holley Commander 950 Pro w/FJO Racing Wideband controller tied in.

As far as killing the O2 sensor, my understanding is that the NTK UEGO WBO2 sensor will stand nitrous runs with leaded gas, as long as you run unleaded the rest of the time. They are a lot less sensitive than the narrow band sensors.

If you haven't seen it, here's my motor and my site link:



Thanks for all the input. Even though I don't have an LSx car, I love them and get a lot from this forum!

Jim

My Site: http://home.mindspring.com/~jim_fisk/id1.html

 

I'm very impressed with your site.
I can't even list all the things I see in your site pictures that you've went way out of your way to do right.
This is uncommon in todays world of quick bolt-on and expect the best.
Impressed.