Cux350z

iTrader: (162)

i think everyone else is saying just run 15lbs throughout and screw running 12 below 5500

westpak

iTrader: (19)

one thing you don't know in those set ups is the timing curve, I have mine set up similar to stock where it dips in the middle of the rpms and slowly creep up

str8dum1

iTrader: (11)

^well thats how a standard MBT curve would look. I'm sure you could counteract the trq drop to a degree with more timing, but more boost is safer from what I have read, esp at the levels we are talking about.

15psi thoughout would still have you dropping trq 100 ft-lbs or more by redline and doesnt help gettin a flat trq curve compared to a sad face (

Plus like in the original dyno's case, 15psi would produce too much trq at 4500 rpms. where as 15 psi at 7000 rpms probably would be fine (ie, think of why people say superchargers are safer, bc the trq is right shifted). So essentially you are getting the big kick of a turbo with the pull of a supercharger.

Cux350z

iTrader: (162)

15psi throughout would keep the tq the same post 5500rpm and increase it before hand. You would have more area under the curve.

4SHIZZIL

iTrader: (10)

what is the first thing people to with their new stock block TT set ups? Top Speed Run! 6th gear for a long period of time and if the motor had a few miles on her before the TTs, boom. I have hit the speed limiter in my car many times...10 or 15 in 2 years of boost. We have tracks all over DC: :-)

The main reason I choose the Vortec over TTs is that I only hit max HP and TQ (combined) for a very short period of time. VS a TT set up where the TQ is maxed early on and hangs around long enough to snap a rod. I only run stock blocks, so I dont have PERSONAL built block experience.

The majority of boosted cars here on the eastcoast are stock blocks with the same above posted dyno curve issue (or perceived issue).

Just like everthing, there is a sweetspot where air/fuel/boost and everything esle is happy... do much or little of one or the other and the effeciency runs out. Just as a turbo has its limits, so does the VQ.

Like I first stated, if you spend about 2 weeks doing runs in the car under exact load, you can fix this issue by playing and modifying boost, timing, and all that.

It is my opinion that BOOST doestn fix your issue or answer your question... Its VOLUME and a peak effeciency range that is not close to being hit.
or you can build a car with 700RWHP capabilities but run it at 600RWHP and get a line as linear as a dead guy on life support.

drop the boost down and the graph posted above to 3psi less and I bet that flat spot will increase dramatically...drop it another 3psi and I positive that you will get it flat as paper.

increased boost IMO wont help this issue.

deanfootlong

iTrader: (10)

dyno charts 101: area under the curve is greater than area over the curve. i understand what you're trying to do here. on haltech i initially adjusted my duty cycle to do similar to the image you posted. then i switched to PID control. if your motor can handle 15 psi at redline, then it can handle 15 psi at spool up. why lolly gag yourself and start at 12, only to end at 15. theoretically, if you had two identical cars, using both theories, the car that started off with 15 psi will smoke the car starting off at 12 and gradually reaching 15 psi. granted traction isnt an issue. only think you might consider changing is timing to not give you a huge tq amount right at spool up. in the end i think you're over-thinking this one dude.

midz350

iTrader: (4)

I think people here missing that what limits you is the TQ # not the boost you are bushing.
Lets say the peak TQ # that you can achieve without knocking is 550ft-lbs, so why not upper the boost at were you TQ curve start to drop to keep it flat all the way to redline.

550ft-lbs@4500rpm and 500ft-lbs@700rpm > 550ft-lbs@4500rpm and 420ft-lbs@700rpm.

str8dum1: Is this what are you tiring to get to.

rcdash

iTrader: (18)

str8dum1, few folks have turbos with as much breathing room as what you've got. I know mine are tapped out around 18-19 when you factor IC pressure drop into the equation. 18Gs could maybe go a little further, but I think boost increases would show diminishing returns for usual set ups. Also keep in mind that if you set boost to 18 psi, it actually osciallates well above (and below that) at a high frequency. Do a 5 ms recording of boost on the Haltech and see how high it actually spikes... I think most tuners would see hitting above 20 psi on pump gas as a high risk scenario - even if it's well established that a particular engine isn't breathing well enough to generate dangerous cylinder pressures (as measured by torque output).

str8dum1

iTrader: (11)

^any current VQ turbo kit on pump gas has enough breathing room to use boost to bump engine VE. The dyno posted in post 1 is using a turbo that will run >35 psi and >680whp. There should be no reason why his trq curve doesnt pull til redline. I am not talking about strung out setups on race gas. I am talking daily driver tunes.

How would increasing engine VE thru the use of cams, intake manifolds, timing, etc be better/different than upping the boost? In the end, its the same result, without having to buy/install lots of new parts.

Its kinda like beating a dead horse. either people dont understand engine VE or dont mind not getting the most out of their builds...

rcdash

iTrader: (18)

Alright man, if I blow this up, it'll be your fault Next time I'm on a dyno, I'll try it and compare curves.

tonyzS/C03

iTrader: (3)

in for comparison graphs, this should be interesting to see.

Vas_Z33

iTrader: (39)

I may have to stop by at RT/Tuning again soon... so Ill see if I can put it on the dyno again lol

binder

iTrader: (8)

back from the dead.

I might end up doing this so i can get traction on my beast yet still pull harder up top.

It's amazing how many people aren't understanding this concept.

15psi at 4500rpms is NOT the same thing as 15psi at 7000rpms. The same as 500ftlbs at 4500rpms is way more destructive than 500ftlbs at 7000. People are forgetting that the higher the rpm the less load will be on the rods. This is why nitrous is so destructive on engines. It provides tons of tq down low in the rpm range which snaps rods.

Also, say 500ftlbs is the same stress at 4k as it is at 7k. Well you know the rods held that 500ftlbs at 4k then why not hold that 500ftlbs all the way to redline instead of it dropping down to 300ftlbs. That's what he is saying.

Here is an example: I'm tuned to 22psi at 650hp right now. 581ftlbs tq. I have TONS of turbo left and plenty of engine and fuel. My problem is traction. So, if i ramp my boost up after peak tq (581tq) and just hold that tq to redline i will pull harder. I still have my traction down low and i have head room up top. So it basically would be liek a supercharger and flat tq curve.

Now you say, "well why don't you just run 28lbs so you have that 581ftlbs at redline and call it a day". For 2 reasons: 1, i won't get traction so it would suck. 2, that means i would have like 700ftlbs of torque down low which i think is outside of my personal safety window.

Alberto

iTrader: (14)

PFS was doing this in 2007

Go back and search for their 18G dyno's and crazy flat TQ curves

Closed down FT even did this on some cars...

binder

iTrader: (8)

see, so someone is using it. It makes perfect sense to me. I don't really want over 600tq on my car but i'd like to have 600tq all the way to redline

jerryd87

iTrader: (4)

actually 500 ft lbs of torque is much much more destructive at 7000 rpms, the faster speed mixed with the same torque results in more stress. force = mass x acceleration torque is the subsitution for mass and i dont know fast the rods are moving off the top of my head but 7000 rpms is much faster then 4500 hence 500 ft lbs at 7000 rpms making 666 hp vs 500 ft lbs at 4500 is only 428 hp. both cause stress on the rods so both must be accounted for.

now as far as using it for traction, if you have traction issues it makes 100% sense to do it, i used to use the same concept on my nitrous fed camaro i dragged. used a jacobs mastermind(did nitrous % by rpm for only 200 bucks sucks they dont make it anymore) to hit the car with a 75 shot at 3k rpms and it would progress up to a 300 shot at 6000 rpms with my shift point being 6500.

the big issue with nitrous isnt the torque it delivers its the fact it is a much purer mixture so when it burns it burns ALOT hotter, all the extra **** in the outside air makes it burn colder. Thats why you cant burn liquid oxygen it will result in retarded hp but it burns so hot it will melt right through a cast iron block. the purer the concentration the more unstable it is as well making it unpredictable, turbos might be forcing more air in but the ppm is still the same its still right around 21% oxygen just a larger volume vs nitrous being 33%

Eno

iTrader: (1)

Nothing to contribute to the education here (obviously) but I will say that it's the threads like this that remind me why people who want to talk shop go to my350z. Really great to get a variety of informed perspectives!

I did find myself seeing the value in spreading boost out to maintain traction so to me the concept was intriguing.

I'm becoming less interested in the "rwhp" and more interested in what the rear wheel is able to put into the ground. 500ftlbs of torque to the wheels resulting in standing still sounds like a waste. Of that 15lbs of boost creating force that goes to your wheels, only about 8 of that is probably being used by the vehicle to move you forwards anyway.

Law of conservation of mass and energy dictates that something can not become nothing- and this fact is evident considering the force generated by the remaining 7lbs of boost is transferred into heat and smoke of spinning tires. I may be standing still with my 15psi- and all that torque may be generating force- but all that force is being converted to bald tires, smoke and noise and not a thrilling forward motion.

The conversation here has made me want to go back and look at the few dyno sheets that I have. I'm still learning a lot, so I get quite enthusiastic to follow these kinds of threads.

I'd like to see a few of the guys who were involved in this thread last year weigh in again- especially str8 and dash...

3hree5ive0ero

iTrader: (95)

This is wrong. Nitrous oxide (N20) cools down the air temp and does not burn hotter. One of the reasons why you gain so much power/torque with nitrous is the cooling effect from the liquid nitrogen changing into a gas phase when exposed to outside air. Majority of the power comes from nitrous oxide being broken down into 2 parts nitrogen and 1 part oxygen during combustion. The extra oxygen from this reaction is what allows for more power/torque, with more fuel. The nitrogen molecules released helps the mixture burn slower.

And while what you're saying about liquid oxygen is correct, that has nothing to do with liquid nitrous oxide.

jerryd87

iTrader: (4)

when it is initially sprayed it cools down similar to how meth or co2 has, it absorbeds an immense amount of heat when it is vaporized. once its done with that and is actually burning it does indeed burn hotter, due to the higher purity..... not a larger amount as in turbos or super charger but a higher purity. you can see this with the old boat races, when it was first starting up and people where experimenting with things, they where finding anything more then 50% oxygen would melt pistons regardless what you do and i have personally watched someone using 100% pure liquid oxygen melt a hole through a cast iron block in about 10 seconds after starting the injection.

the cooling effect on N/A applications is negliable at best, slightly better then pure meth injection but not worth more then a couple hp more then meth from cooling. forced induction however is much better which is why on a 50 shot you will typically gain around 75 hp, more if you arnt using a proper intercooler or operating way out of your effeciency zone. what you say about nitrous is pretty much repeating what i said its a higher purity 33% oxygen vs about 21% from the air we breath. inject say 800cc a min of nitrous and your are displacing 800 cc a min of air the engine would normall injest, the extra 12% oxygen the nitrous has over the air we breath is enough to make enormous gains. the 67% nitrogen the nitrous contains does indeed make it burn slower and hence cools down as it makes it less energetic, but 79% other stuff in air makes it burn even slower then nitrous and hence it burns at a lower temp.

http://www.nitrousdirect.com/nitrousoxide.html
it dosnt say exactly how much but it says right from a manufacturer that it indeed does burn hotter.

3hree5ive0ero

iTrader: (95)

Nitrous oxide increases the burning rate. Pure oxygen alone would increase the temp, yes, but we're not talking about pure oxygen. We're talking about nitrous oxide, which means you have to consider the overall effects, rather than talking about one aspect of it. Also, I don't see where that site says the nitrous oxide makes things burn hotter.

And here's something else I pulled from that site you linked.