Boost by RPM?

[Jordan Y.]

Some of HybridSS's latest posts have gotten me thinking about something- is there a boost controller that lets you set boost by RPM? Al has been talking about using progressive or multi-stage nitrous setups to combat falling torque with rising rpm to keep the torque output fairly even throughout the operating range of the engine. Centrifugal superchargers also do this by the nature of their design. This seems like a really good idea that might be applicable to turbocharged setups where the power you can produce is not limited by the fuel you're running but by the strength of the internals or block.

The idea would be a boost controller that would let you ramp up the boost after the torque peak to keep it there. So, on something like a turbo 5.0 on a stock longblock, with the torque falling fast after 3500 or so, you might be able to keep the torque line flat by raising the boost like a centrifugal charger and achieve a broad powerband and optimum torque up to redline.

Is there something like this out there, or is it too complicated a task for the electronic boost controllers out there? Is this even a good idea- is my underlying theory sound?

[TIM TIM TIM]

never heard of it, and i think most people max there boost out from the get go, so they wouldnt have that much room to RAISE it durning acceleration

[Josiah]

I can program my standalone to control boost by RPM, it would have the definate advantage of less wheelspin....but its not RPM you want to set it by, its MPH

[Rich]

I believe the AVC-R will do it. I've never messed with it much because I prefer full boost whenever possible.

[Slash]

AVC-R will do it. However it takes a really good tuner to make an avc-r work smoothly as a profec B.

[Ian MMF]

aem ems does it, avcr does it also

[HybridSS]

Heres how I try to do it. Look at your shortblock combo..and think of how much TQ it can handle. On mine I will say 750rwtq is cake...so I want to make 750 rwtq from 3000 rpm where i start spraying...to redline if possible. My redline is 7500 rpm. DO the math and you will come up with the HP curve.

By going with the TQ line to plot your goals it does a few things.
#1 peak tq is were detonation is most likely..so plotting your TQ line will be helpful in tuning. ESPECIALLY if you are trying to maintain a PUMP gas tune.

#2 it provides for a flatter, longer suitable rpm band that is very useful and you can gear your car accordingly


Jordan you are really catching onto the finer points of designing a combo. Especially when you refer to doing this on something like a very limited 5.0 short block.


How to do this on a turbo though I cant provide much input. But I can tell you I look at SOME turbo graphs and boy do they need help. Peak HP #s are sometimes great. But the Tq line can come up very late...and fall off quickly. To me it seems for a street car the best way to get around this would be to OVERTURBO the engine and use a bit pf spray to spool up...then limit the TQ with the boost controller and add more TQ/boost with RPM. Thats for a street car. For a race car there are a ton of ways to plan around thwe Turbos poer band with Tq converters and gearing and such.


Glad to see you thinking!!!


I have to head to work...Ill post more on this later.

[Ender.]

This is all really interesting stuff. I <3 the smart people on TR. These are the type of threads that I enjoy reading and to get me thinking.

[Josiah]

eh, it would be better to program one to limit boost by mph to prevent wheelspin, I have no problem with my power or torque curves from my turbo, I do have a problem with wheelspin

[HybridSS]

That true about wheelspin. So what I am trying to do is when I set up a combo and dyno...i want to MAKE ALL THE HP I CAN in the 1:1 gear. I do that by using TQ management prinicples with filling as much juice as I can based on RPM and magane that TQ. Doing it this way show the MAX safe HP that you can make and are tuned for. Then to combat wheelspin at the track or street I use whatever is avalable to limit power production in the lower gears. My new NX maximizer has nitrous by the gear and it sounds as though you guys have boost controllers that do the same. I want to limit power in first...but by third I want ALL i can get safely.

I really have no clue to the best way to get this done on a turbo car. And some turbo cars maynot even benifit especially if they are an auto with the correct stall and gears etc. But i do belive most street driven manual boosted cars would benifit greatly by doing something like Jordan Y has suggested.

The days of slapping on a turbo or a single stage nitrous kit are over if you want to be competitive. There are ways to design your power graph the way you want it. The fast guys are the ones who will figure it out.

[Sneakin Deacon]

I can program my standalone to control boost by RPM, it would have the definate advantage of less wheelspin....but its not RPM you want to set it by, its MPH


no, it really is RPM you want to set it by.

and yes, Al has definately done this great. i use a centrifical blower, and my tq right now is almost as flat as it could be...its just a slight arcing but from 2-6k it is no lower there is only a 20-30rwtq variance.

i think this may be harder to accomplish with a turbo as so many factors come into play. flat curve is somewhat hard to do, as you either get a smaller exhaust wheel to spool up and get the torque going in the lower RPMs, but the problem then lies with too small and there no top end even if you crank up the boost. and what you want to do with increasing the boost as you come into the higher rpms is a good plan, but if the turbo cant really support the airflow needed, its hard.

http://i.b5z.net/i/u/1473169/i/95_LT1_Torque_ezr.jpg

thats the rear mount sts kit, the red is the kit, the blue is stock. stock is a great torque "curve" till about 4.5k where it begins to run out of breath. see how the turbo has affected the torque curve though? yea, its much more power, but the torque isnt steady any longer. basically, this car has a kick ass mid range, but in a race situation, on every shift, he is rolling right out of the torque.

only thing i could really suggest, is figure out your usable rpms at WOT in a race situation say 4000-6500 or so, and make your goal to have that as your power band area. either by having a cam selection with a duration geared towards upper rpm's where it can compensate for a dying turbo, or spraying it.

[Sneakin Deacon]

also, if anyone was curious what the formula Al was talking about it is

HP = (torque * RPM)/5252rpm

eg. 495hp = (400tq * 6500rpm)/5252rpm,

so to attain 400wtq at 6500rpm, youll be making 495whp at 6500rpm. and at 2500, you'll only make 190whp.

[BOOST JUNKIE]

Applying progressive nitrous theories to increasing boost with RPM is really not a good example.

This is due to the nature of the beasts.

With nitrous, you are somewhat limited by the VE of the motor in terms of how much power you can make at a particular RPM. You reach a point where introducing more nitrous into the chamber does nothing for power. This is because at ~1ATM nitrous packs roughly 2.37times as much oxygen as air, and this is a FIXED value at that pressure. You can empty the entire bottle with no nozzle and you won't squeeze more than X amount of air into the combustion process. This is why increasing the amount of nitrous as RPMs goes up helps, because as the engine is turning faster, it can injest more nitrous, thus maintain a flat torque curve.

With a turbocharger, its a completely different story. On an engine with good VE N/A, it will maintain a flat torque curve with a properly sized turbocharger. This is due to how a compressor works. If a turbo has a max flow of 100lbs/min at 10psi for instance, and the motor can take in 50lb/min @ 10psig at 4000RPM, and 90lb/min at 7000RPM @10psig...if you run 10psi on the turbo, it will fill the motor with 50lb/min at 4000RPM, and 90lb/min at 7000RPM. This is VERY different than a nitrous setup.

For a fixed amount of nitrous, the amount of increase drops as the engine can injest more air. Not so for a fixed amount of boost and a PROPERLY sized turbo.

Doing RPM/MPH based boost for traction is a good idea though.

[HybridSS]

Applying progressive nitrous theories to increasing boost with RPM is really not a good example.

This is due to the nature of the beasts.

With nitrous, you are somewhat limited by the VE of the motor in terms of how much power you can make at a particular RPM. You reach a point where introducing more nitrous into the chamber does nothing for power. This is because at ~1ATM nitrous packs roughly 2.37times as much oxygen as air, and this is a FIXED value at that pressure. You can empty the entire bottle with no nozzle and you won't squeeze more than X amount of air into the combustion process. This is why increasing the amount of nitrous as RPMs goes up helps, because as the engine is turning faster, it can injest more nitrous, thus maintain a flat torque curve.

With a turbocharger, its a completely different story. On an engine with good VE N/A, it will maintain a flat torque curve with a properly sized turbocharger. This is due to how a compressor works. If a turbo has a max flow of 100lbs/min at 10psi for instance, and the motor can take in 50lb/min @ 10psig at 4000RPM, and 90lb/min at 7000RPM @10psig...if you run 10psi on the turbo, it will fill the motor with 50lb/min at 4000RPM, and 90lb/min at 7000RPM. This is VERY different than a nitrous setup.

For a fixed amount of nitrous, the amount of increase drops as the engine can injest more air. Not so for a fixed amount of boost and a PROPERLY sized turbo.

Doing RPM/MPH based boost for traction is a good idea though.


Good post. Its definatly different in HOW you could do it. But the desired result is basically the same. The path to get there will be very differnt. Huge HP peaks suck if they only maintain TQ for 1500 rpm.

Managing Tq on the boosted car will be more difficult. But I think its possible. I have some ideas id like to try. But it involves a combination of boost and juice and would need some serious electronics.

[HybridSS]

also, if anyone was curious what the formula Al was talking about it is

HP = (torque * RPM)/5252rpm

eg. 495hp = (400tq * 6500rpm)/5252rpm,

so to attain 400wtq at 6500rpm, youll be making 495whp at 6500rpm. and at 2500, you'll only make 190whp.


750 ft/lbs x 7500 rpm / 5252 = 1071.02 rwhp :naughty: Thats my goal. :tard: