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Discussion Starter #1
Currently have a overly tight converter spec’d for a much larger motor.

I threw a 4.8 in the car to finish out the season while I finish building up a larger motor. With -20* of timing I can manage 4lbs of boost and 3000rpm on the trans brake. When I release the brake boost falls and the car bogs to 4k before the turbo lights off.

Recently threw a n20 dry kit on I had laying around. Using Mega Squirt to control this and cut the nitrous off at 4k. Using a .035 jet (maybe 50ish hp?) I’ve still yet to fill the bottle and plan on disabling the anti-lag/timing retard on the 2step.

Question is, if I’m still having issues. Should I just keep upping the jet size? Or should I incorporate some sort of anti-lag in addition to the nitrous? I can add or subtract as much as 40* on the brake.

Thanks
 

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Discussion Starter #3 (Edited)
I would not go lower then 1 or 2 degrees with the nitrous or you will risk a nitrous backfire. Just up the shot a little if it's not enough.
Lower than 1-2* total? Or 1-2* less than the map timing? Do you do this on your setup?

Not trying to be a smart ass, but wouldn’t a nitrous back fire in the exhaust pre turbo be the goal?

Hanging the valves open and pushing the combustion out in the exhaust is the whole point isn’t it? Or are you saying it would be too violent? With the wide open path to the turbo I wouldn’t think it would be splitting pipes or anything? Wouldn’t the “explosion” just take the path of least resistance through the turbo and spool the crapola out of it?

Or do you mean a backfire through the intake?

Thanks!
 

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This is simple... i would keep putting the juice to it till you get it where you want it unless it's not legal for some kind of class you are running.
Then i would look at running a 2-step or anti-lag setup and a bump box to help you sit and spool longer before the lights go down...
 

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We don't retard timing like that with autos. I actually add timing in order to get up higher on the tbrake before going up on the 2 step. The spark cut of the 2 step puts plenty of fuel in the exhaust to get the turbo(s) spooling. The timing retard strategy is good for stick cars as it creates artificial load on the engine that it doesn't have while reving in neutral.
 

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Discussion Starter #6 (Edited)
We don't retard timing like that with autos. I actually add timing in order to get up higher on the tbrake before going up on the 2 step. The spark cut of the 2 step puts plenty of fuel in the exhaust to get the turbo(s) spooling. The timing retard strategy is good for stick cars as it creates artificial load on the engine that it doesn't have while reving in neutral.
Appreciate the input! I've actually tried -20 and up to +40 degrees. -20 seemed to work better on my setup. Advancing took longer to build the boost, though it did eventually build about the same amount of boost and was less violent sounding. I'd like to limit the amount of nitrous used if possible. I'll play with adv and retard if the 50 shot alone doesn't do it. I don't want to throw a 100+ shot at this thing to get it going if I can help it.

Should mention again though this part combination is so out of whack, I'm having to go to extremes to try and launch it. 2 step alone would be fine if the converter was matched to the motor.
 

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Appreciate the input! I've actually tried -20 and up to +40 degrees. -20 seemed to work better on my setup. Advancing took longer to build the boost, though it did eventually build about the same amount of boost and was less violent sounding. I'd like to limit the amount of nitrous used if possible. I'll play with adv and retard if the 50 shot alone doesn't do it. I don't want to throw a 100+ shot at this thing to get it going if I can help it.

Should mention again though this part combination is so out of whack, I'm having to go to extremes to try and launch it. 2 step alone would be fine if the converter was matched to the motor.
What turbo is it?
 

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Discussion Starter #8 (Edited)
What turbo is it?
S410 based cartridge, 76mm billet comp. 1.25 t4. 77.5/87 exh wheel. 2.5" hotside with F-body manifolds.

9.5 billet PTC converter. Spooled great with my 5.3 and old stator. Went from at 17 blade stator to a 14 blade. The 17 was too loose. I could hit 5k+ and 25+psi. Though it was so loose it didn't put the power to the ground. I was launching at 25lbs off the t-brake to cut a 1.3x 60'. Then 90' out power was "all in" and a hand full. I wanted something that was much tighter down low. And had also planned to move up to a 6.0 this winter. So they suggested a 15 blade. Zac Brown went with a 14 and said it acted like I was wanting with his huge T6 100+mm exh wheel on it. So that's what I tried.
 

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Lower than 1-2* total? Or 1-2* less than the map timing? Do you do this on your setup?

Not trying to be a smart ass, but wouldn’t a nitrous back fire in the exhaust pre turbo be the goal?

Hanging the valves open and pushing the combustion out in the exhaust is the whole point isn’t it? Or are you saying it would be too violent? With the wide open path to the turbo I wouldn’t think it would be splitting pipes or anything? Wouldn’t the “explosion” just take the path of least resistance through the turbo and spool the crapola out of it?

Or do you mean a backfire through the intake?

Thanks!
1-2* total. Yes I was talking about through the Intake. I tune multiple cars with small engines. Pm for more info if you'd like
 

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Discussion Starter #11
Does it need boost to get to 3K or are you at 3K without boost and then the 2 step builds it from there?

Do you have CO2 on the gate?
It's barely making 3k at 4lbs of boost. I'd guess it stalls to about 2700 on the brake before it gets into boost. I'd have to double check but its around there. Takes it a second or so to get up to 3k.

No C02 on the gate. I block the lower signal to the gate completely when I go to the track. This nets me about 20lbs. Then I add pressure to the top port from a cab mounted pneumatic regulator for more boost. Usually run 24-25lbs. May run a little more on the 4.8. I don't believe the gate is blowing open on the line.
 

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Just spray it. Won't take much. A 50shot will be like 75ftlbs down there

And I have a 13-0. Tighter yet
 

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Personally I would start with a 61 jet. Its only on for a very short time.
Ive done a 45 ish jet(no antilag) on a v6 and it worked well. I had it shut off at 9 psi. Only used 1.5 lbs in 8 passes

There was a guy on here or Turboforums with a buick 231cid v6 with an s500 on the car. He tried a bunch of things and in the end he was spraying 400hp for .8 of sec. to spool and get it on boost. Dont think he was using antilag. Just a transbrake.
 

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Discussion Starter #14 (Edited)
Play time was cut short, but after a little driveway testing I'm pretty optimistic. Was able to stall up past 4300 rpm and make 7psi very quickly. This was also with the exh dump closed. I think 4500 and 10+ lbs will be no problem.

The jet was originally a 22 and I drilled it out to a 35. Looks like thats in the neighborhood of 60hp? This was with no fancy ignition tricks. Hoping to head to the track tomorrow evening and get a little street testing done on the way. Spraying at the turbo inlet. IAT went form 125 to 115 in a hurry! My IAT sensor is right by the throttle body post IC. :p


Personally I would start with a 61 jet. Its only on for a very short time.
Ive done a 45 ish jet(no antilag) on a v6 and it worked well. I had it shut off at 9 psi. Only used 1.5 lbs in 8 passes

There was a guy on here or Turboforums with a buick 231cid v6 with an s500 on the car. He tried a bunch of things and in the end he was spraying 400hp for .8 of sec. to spool and get it on boost. Dont think he was using antilag. Just a transbrake.
Yea thats donnie's car, he's nuts! He is using straight methanol on the nitrous side and spraying a fogger with meth/n20 pre-turbo for an additional "afterburner" effect.

 

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Read somewhere on here about somebody spraying it into exhaust before turbo to help spool by burning unburnt fuel.closed loop control
Anybody know more about this?
Just curious to learn more things.
 

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With -20* of timing I can manage 4lbs of boost and 3000rpm on the trans brake. When I release the brake boost falls and the car bogs to 4k before the turbo lights off.
Is it bogging to 4k because 4k is the next rpm column with normal timing? Low timing will make more boost, but it will make the car an absolute turd, and can actually limit rpm if you're trying to get more. If you're trying to drive out on that low timing that's a problem. It needs to be switched off when you launch (back to normal timing). I went through the same thing with my Mighty Max. Switching the timing back to normal with the brake pedal was much better than waiting for rpm to climb out of that low timing. Nitrous would fix most of my problems with that truck but I'm avoiding it for a couple of reasons, so ECU trickery is my next best option and I've played with it extensively.

If you need more RPM as well, and quickly, you made the right choice with the nitrous. It just plain works. Run normal timing with it, it will build the boost anyway, and the rpm will climb quicker with normal timing. Run whatever shot you need to get it up quickly. At a 100 shot, a bottle lasts about a season on my car, and I run it pretty often.

The drop in IAT with the nitrous is nice, but I think you'll find that at WOT when it matters that effect will disappear. Just not enough nitrous flow vs airflow at that point to make a dent in IAT.
 

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Discussion Starter #17
Is it bogging to 4k because 4k is the next rpm column with normal timing? .

No, the timing retard is triggered by the trans brake button input. As soon as I release the TB button timing jumps back to my base map. I’ll look at the logs but I believe it’s almost instant. No long ramping process or anything.

Timing is at 24* at 1psi. Ramps down to 18* by 12psi and 12* by 25psi. AFR is about 11.0-11.2 across the board. E85 fuel. 16gph of 50/50 water meth as well over 20psi.


I had no idea a 100 shot would last that long!

Do you use a dry shot? What pill size? When do you activate the nitrous? On the brake? On the brake release? How long is the 100 shot active? I’m trying to get an idea of the staging and launch process I’ll have to use tonight.

I figure I’ll need all the rpm I can get, so the 2-step is off. I have the nitrous come on at 99% TPS and 3100, then off by 4500. I don’t have a way to control it by boost at the moment. I figure I’ll load the car up on the lights at below 99% TPS and as soon as the lights start to drop I’ll go 100% TPS and activate the N20.




Thanks for the input! You car is one of my favorites, been following it for years.
 

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Discussion Starter #20
That timing is really low for e85. You should be able to add 4-5* everywhere safely.
I'm sure I'll end up with more. Still haven't got to tune at the track yet. Can't run big boost on the street.

I may add timing depending on what it wants. I'm running a tiny cam (212/212 @ 112) so I'm not keen on big timing numbers right off.
 
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