383LQ4SS

iTrader: (33)

Do you guys try to tune your AF ratio on your nitrous kits to make best power on a given pill size? And if so how lean are you willing to go? What actual AF have you seen to make best power?

For instance..if you have a heads and cam car making 430 rwhp and spray a 150 shot for a total of 580 rwhp and 640 rwtq...but AF is at 11 to 1...do you try to get it leaner in order to squeeze a little more power out of it?

What is your approach to tuning a healthy motor of say 500-600-700 rwhp. Please be specific and provide examples if possible. Also include thoughts on timing and octane if it pertains.

Robert56

iTrader: (2)

What do is a fuel curve. Meaning, start leaner then progressively go richer to torque peak then progressevly lean out to redline. I start say 11.7 or 8 then at torque peak I'll be at 11.2 or so then at redline I'll be leaned out again in the 11.7/11.8 range. This has worked very well for me and have gone to 200 shot on stock longblock this way. Timing at 22* and running 91 octane. I have had 0 kr and no fried plugs or the such. I am tayloring a similar curve for my upcoming 250/300 shot, however, it will have a richer curve, and race gas, colder plug and maybe a tad more timing pulled.
Robert

383LQ4SS

iTrader: (33)

Excellent Robert....any others?

CAT3

iTrader: (9)

I set mine up like Robert does. Curve it, except I am not so lean at start, since it has a huge torque spike down around 3000rpm launch. I leave it rich til pk tq and then begin the curve, with it richer after peak HP just in case I miss the shift rpm. Timing I have played with 22* on 140+ shots, and found that 19* was too much without the race gas. Didnt burn any plugs before but used the right tune. I prefer a healthy mix of race gas after 150 shots for the insurance. I hit 220 DP before on stock bottom, went nearly straight 113leaded in the tank, didnt kill the O2's either.

stang90gt50

iTrader: (6)

I dont actually really curve mine much..and I've sprayed up to a 250 on stock shortblock and it was for a solid 100 plus dyno pulls and alot passes.

Since Im spraying through a TNT F2 kit in front of the TB I do worry about potential lean cylinders so I tune my setup at 10.5:1 On the street im sure its a bit leaner.

91 Octane in the tank, dedicated 2 quart fuel cell (little jr dragster one like $40) with C16 in it.
I use a timing retard to pull 10 degrees on the hit (28 degrees down to 18 degrees).

We have since went to a forged bottom end and on the 300 rwhp TNT pills we have been through alot of experimentation. Everytime we have tuned the car at approx 11-11.5:1 a/f (verified also by the in car innovative wideband in the car), it works great on the dyno and from early 2nd gear up street pulls..puts down 800 rwhp using this pump gas setup and C16 cell..then when you spray the car for a full pass from a dig through the 1/4 on tire, it burns plugs, has popped the cometic head gaskets, burned the head requiring welding etc.

Running straight race gas doesnt fix the problem, neither does pulling more timing. Its just spraying that much through two foggers in front of the TB. We have tried different nozzles, rotated placement etc etc..

The only tune that hasnt had a problem and will make full 1/4 runs without hurting something eventually has been tuning it at about 10.5:1 (I think a direct port might fix this problem because you wont ever get a lean cylinder).

calongo_SS

iTrader: (7)

That's a big shot through the intake like that. I'd def. go direct port.

383LQ4SS

iTrader: (33)

outstanding info guys. Keep em coming.

I just wanted to get a thread on actual tuning beyond the typical 100 or 150 shot on pump and no race gas. Lots of people are stepping up in the area of 175-300 shots these days and it seems many are not fully aware of what goes into tuning.

Good stuff.....any more?

white2001s10

iTrader: (4)

I concur with this part.
The torque/power peak is generally a little earlier (maybe 500 RPM) when on a big bottle shot, and it fades off at a faster rate after the peak than a NA engine, so there's no need for as much fuel or timing retard well after the peak.

For maxium power you want to be leaner and with more advance while in your low gear/s to increase the burn speed to match the piston speed. Once in high gear you want more fuel and less advance. This assumes a car that will hook the power down low. One way I've found to do this is simply to increase the bottle pressure to a point that will fade soon after launch, and also to lean down the enrichment fuel up to the point of shift-recovery RPM so you're only lean during the launch.

(on the other hand)
So far most vehicles I've seen have trouble hooking a big bottle shot, and it's neccessary to use the tune to soften up the bottom end a bit. To do this you go the opposite way by adding fuel and pulling timing up to shift-recovery.
This doesn't give maximum power, but gives quicker times in a lot of cases.

NXRICKY

iTrader: (1)

I have a different thought to the richer or lean to get more power. To lean a system out to gain ever last HP out of it, is not sound tuning in my opinion. Heres why the close you get to that MAX HP point of no return the smaller your window for a mistake becomes. So you keep dialing the Power up to gain a little more power maybe 10-15 I do not know, maybe even 25hp that will cost you or win you a race.?? But now you are done on the dyno and you out playing at the track. And you are in some good dense Air, you just leaned the car out and possibly too lean and hurt something. For a few HP.
In the Carburator stuff I play with, we pull the timing back until the car slows down ET wise, then add a couple back in. This yeilds the largest window of safety as far as the timing goes in relation to the air that is available. So now you are testing on another day, good air and the car picks up et but not to the point of hurting the engine. Now I am talking about 500+ on nitrous(race car) not 150hp but the process is the same, there is no need to run a car on the edge to make it go fast.
Stay a little rich and a little light on timing and have fun for a very very long time.
Ricky

CAT3

iTrader: (9)

Alibi- I dont tune on a dyno. I use logs from the highway/byway and track. I agree with you Ricky that richer and lower is safer and lasts much longer, which was to be the goal of my dry tune, self adjusting timing and fueling based of temp vs load etc..

stang90gt50

iTrader: (6)

Dry kits are nice also because they are very easy to use progressively, A/F is easily tuneable through your tuning software as well as timing.

I really want to mess around with some 300+ hp dry setups (like ive seen you do in the past 383lq4). I have all my maf flow tables working nicely on 100-150 dry shots pulling timing automatically and ramping more out as more dry comes in (very trick actually). Also its easy to dial in a/f through the P/E table with the increased airflow read by the nitrous.

All of that almost points dry kits as being superior to a non-direct wet in everyway, but I am still leary of stacking that much dry on a car.

383LQ4SS

iTrader: (33)

I agree with Ricky. The point I was going to make...and the reason I asked the questions the way I did was because IMO I would rather have a car at 11.5 to 1 Af making 600 rwhp total on a 200 shot....than make 625 at 12.4 to 1 with those same jets. I would rather keep it at 11.5 and just increase the nitrous jet to attain the same HP level.

Also...I generally see the power go down as the Af starts going up above 12 to 1. Maybe its just me...but I alwasy make greatest power right in that 11.5 to 1 +/- .3 or so.

Same goes for timing. I would rather pull a decent amount and add nitrous/fuel to get to the power I want.

Stang90GT50...I agree about the dry shot. They are pretty easy on LS1s with a MAF. But at certain HP levels they become very difficult. Generally anything over 700 rwhp total gets much harder to do.

And at smaller levels...dry and wet are equal. So to me it seems benifiial to know where you will end up as far as total HP from the motor (na + nitrous) before you pick your setup.

My dry setup is currently running 10.5 to 1 Af and at 22 degrees of timing and I still use a good amount of 100 octane. Even though I would be fairly safe on 93 probably. Its about a 130 shot and makes about 460 rwhp through the Th400. I will leave it that way for when I run the 225 shot. I dont want to even remotely be close to the parameters that will invite detonation.

Robert56

iTrader: (2)

My torque peak is in the low 4xxx rpm range in second gear, so I can get away with leaner to start, so no real torque spike. That's been tuned out for longevity's sake.

NX Ricky [qoute]I have a different thought to the richer or lean to get more power. To lean a system out to gain ever last HP out of it, is not sound tuning in my opinion. Heres why the close you get to that MAX HP point of no return the smaller your window for a mistake becomes. So you keep dialing the Power up to gain a little more power maybe 10-15 I do not know, maybe even 25hp that will cost you or win you a race.?? But now you are done on the dyno and you out playing at the track. And you are in some good dense Air, you just leaned the car out and possibly too lean and hurt something. For a few HP.
In the Carburator stuff I play with, we pull the timing back until the car slows down ET wise, then add a couple back in. This yeilds the largest window of safety as far as the timing goes in relation to the air that is available. So now you are testing on another day, good air and the car picks up et but not to the point of hurting the engine. Now I am talking about 500+ on nitrous(race car) not 150hp but the process is the same, there is no need to run a car on the edge to make it go fast.
Stay a little rich and a little light on timing and have fun for a very very long time. [quote]
I concur. This is why my car see's little dyno time, but rather use the LM1 and data logging for tuning and monitoring each race day. I don't feel I am on the edge because of watching all of my parameters between each run, allways looking. Now if I could just get a car capable of running a 500 hit.

stang90gt50 [quote]Dry kits are nice also because they are very easy to use progressively, A/F is easily tuneable through your tuning software as well as timing.

I really want to mess around with some 300+ hp dry setups (like ive seen you do in the past 383lq4). I have all my maf flow tables working nicely on 100-150 dry shots pulling timing automatically and ramping more out as more dry comes in (very trick actually). Also its easy to dial in a/f through the P/E table with the increased airflow read by the nitrous.

All of that almost points dry kits as being superior to a non-direct wet in everyway, but I am still leary of stacking that much dry on a car.[quote]
I agree, you gotta love those dry hits in multi stage and/or progressed. Yea, Al is the dry "Master of no Disaster".

white2001s10, as usual a very good explanation, and usefull insight.
Robert

white2001s10

iTrader: (4)

I'm pretty positive that your huge torque spike is a function of your torque converter and not a direct relation to N2O power vs RPM.
Piston speed will be changing very quickly up to the flash point of your converter, and so you don't need to be rich or retard the advance up to that point.


When I was using the words "lean" and "rich" in my first post, it was in regard to running with the N2O flowing.

Stoich assumes 20 - 21% oxygen in the air, which we all know changes when you use a big bottle shot.
The max power AFR of 15% richer than stoich is no longer going to be just 12.4 - 12.6:1 AFR.
I usually see this drop about one full point to the richer with a good sized shot.

To clarify my reference points, for a big bottle shot I call 10.8:1 the rich end, and around 11.5:1 the leaner end.
I didn't want people to think when I said lean on the bottle that they should tune for 13.4:1 or anything like that. I should've put this in my first post.

I will say that you can get away with 12.5:1 AFR below your converter flash point, and in first gear unless you're running a glide. The reason being the piston speed is so high and that you spend very little time at or near your peak torque due to less load on the engine. Since most people run less spark advance across the board when on the bottle, the tune is already conservative for low-gear operation.

Of course the opposite is true as well. After about 800 ft into a run the engine is going to want some more fuel to slow the burn down, and some added cooling that comes in handy about that time, due to the increased load. If you have a small bottle that is losing pressure about this time, then you have to do nothing to the fueling as it will just go richer on its own.
Guys running large bottles might want to play around with the tuning on the big end and see how you do.

I normally see a measurable gain by cutting 2* of advance around the 800-900 ft point. If I cut 2* across the board, or even at the 3rd gear shift, then I don't see a gain at all. If I run more advance in 3rd, but then cut the 2* at 800ft then I do see a gain.
This is only going to work if you're pushing your tune. For conservative tunes you're not going to see any gain by dropping another 2* advance anywhere.

Sport Side

iTrader: (6)

I wish I was able to tune spark/fuel for each individual gear.

CAT3

iTrader: (9)

White, I understand what your saying on the reference to lean/rich...I used to go as lean as 13.0:1 on small wet shots, but stepped it up and lower went the AFR, to 12.5, then 12.0, then into the 11.x. I tried playing around quite a bit more with the dry, since there are the vs. IAT functions and such. My TC is not efficient for a nitrous converter, I am positive it wasnt meant to do what I have asked of it. If I tried to lean out any or add advance in 3rd, it would get KR and possibly worse. My timing curves down from 24* to 18*, and the fueling does a wave form, starting 10.0:1 leaning slowly to 10.8:1-11:1 and then back to a 10.5:1 after peak hp. I added more fuel past the peak hp mark, I dont have my Harlan shift light hooked up, so I go from sound and feel for shifts (so far pretty good) and figure since I want to shift and not have a dramatic AFR shift to induce KR that it would be better to go back rich.. I havent seen any loss, and cant recall any gain persae, other than it held together nicely. I do believe I need to finish the larger shots tune, now that I have new plugs in

red90cobra

iTrader: (36)

good read guys thanks

Robert56

iTrader: (2)

ttt, for someone.
Robert