Jackson Racing Rotrex Supercharger System Info and Discussion

[Calum]

Originally Posted by tendogy

Whaaaaaaaaaaaaaaaaat?!?! You got so much crap for the lack of acceleration (relatively speaking) in that video and you didn't want to mention that it was at elevation? So you were only at ~22psi instead of ~24psi; that explains everything.

Do you mean 22psia or 22 psig?

[CSG David]

Originally Posted by Calum

Do you mean 22psia or 22 psig?

absolute broski.

[Sellout]

Originally Posted by qtwre

Won't a turbo just spin faster to hit the same boost target, regardless of elevation? Oh, but then I guess intake temperatures would go up, losing power.

Touche.

There's a little more to it that seems to be forgotten when people talk about turbos at altitude...

Quite often the boost control setup is designed for a target above atmospheric pressure, and isn't set up to read absolute pressure. (this will be the case with a manual boost controller) What happens in this case is your turbo spins a little faster to create the (same as sea level) pressure to overcome the spring, but atmospheric pressure is lower, and so your absolute pressure at the manifold is lower as well. It's not as big a difference as you have with a supercharger. but it's there.

if your boost control is set up to hit a specific absolute pressure in the manifold, using a map sensor and controlled by the ecu or some other electronic device, then this isn't an issue and your car should be capable of VERY similar horespower numbers at elevation and at sea level. like what Mike mentioned about the BMWs.

[Coheed]

Originally Posted by jamesm

if you lose power when you go up in elevation on a turbo system (i.e. the turbo can't keep up due to an inability to push the PR required to maintain target boost at that altitude), your turbo is way too small.

this isn't a realistic concern with any of the turbo kits available for this platform.

I don't think it will be an issue with lower boost setups. But PR can have a drastic impact on the power delivery and output of the system. Remember with higher PR comes higher temps, lower efficiency. The lower compressor efficiency increases the amount of drive force the turbine requires, increasing backpressure. Increased backpressure reduces volumetric efficiency and is detrimental to scavenging, this increases pumping losses.

I've seen turbo setups make 30-50whp more just by going to sea level. And it isn't just because of boost. A lot of these turbo setups utilized Absolute pressure for the boost controller. The system as a whole simply maxes out faster with elevation.

The JR system shouldn't have too many issues with running at higher altitude. But with the system so close to max output in stock form, it will probably be closer to maxed out at 4500ft.

[jamesm]

Originally Posted by Coheed

I don't think it will be an issue with lower boost setups. But PR can have a drastic impact on the power delivery and output of the system. Remember with higher PR comes higher temps, lower efficiency. The lower compressor efficiency increases the amount of drive force the turbine requires, increasing backpressure. Increased backpressure reduces volumetric efficiency and is detrimental to scavenging, this increases pumping losses.

I've seen turbo setups make 30-50whp more just by going to sea level. And it isn't just because of boost. A lot of these turbo setups utilized Absolute pressure for the boost controller. The system as a whole simply maxes out faster with elevation.

The JR system shouldn't have too many issues with running at higher altitude. But with the system so close to max output in stock form, it will probably be closer to maxed out at 4500ft.

You're correct it's not just about being able to hit boost target, but I maintain that f you're seeing you're turbo fall out of its efficiency rage (especially at low boost) due to an altitude change, you simply picked the wrong turbo. Also, as I a stated above it's really a moot point since no one even makes a kit for this car with a turbo small (or maxed out at reasonable boost) enough to warrant this concern.

[CSG Mike]

Originally Posted by jamesm

You're correct it's not just about being able to hit boost target, but I maintain that f you're seeing you're turbo fall out of its efficiency rage (especially at low boost) due to an altitude change, you simply picked the wrong turbo. Also, as I a stated above it's really a moot point since no one even makes a kit for this car with a turbo small (or maxed out at reasonable boost) enough to warrant this concern.

Not sure if serious..

[jamesm]

Originally Posted by CSG Mike

Not sure if serious..

very serious. do you have an example? one may argue avo... but even then i doubt it. unless you live in nepal or something...

[CSG Mike]

Originally Posted by jamesm

very serious. do you have an example? one may argue avo... but even then i doubt it. unless you live in nepal or something...

Avo and Greddy, to name the most common ones...

This is really easy for us to test, because the CA tracks are all at higher elevation, and we have tons of mountain roads.

[jamesm]

Originally Posted by CSG Mike

Evo and Greddy, to name the most common ones...

This is really easy for us to test, because the CA tracks are all at higher elevation, and we have tons of mountain roads.

true... florida guy here. i'd be shocked if either of those kits actually lost power at altitude, but then i don't have any altitude to test this with .

[Sellout]

Perspective, wording, blah, blah, etc, etc...

The efficiency change in the compressor that you see from the altitude change is going to happen on any and all compressors. (supercharger included)

The amount of that change is going to be dependent on how much of an altitude change you're talking about, what the compressor map looks like, where in that map you're usually operating, etc.

Obviously, driving from sea level to Denver is going to mean one hell of a change in compressor efficiency, it will also mean there is less dense air to remove heat from your intercooler and less total density in your intake manifold. Atmospheric pressure in Denver is roughly 12psi so you've lost about 2.5 psi right off the bat. Your boost target (10 psi example) is still 24.5 absolute. Your pressure ratio on the compressor map has gone up two ticks to hit 24.5. You're making more heat. You're rejecting less heat. You're going to lose power. How much depends on your mapping. If you're an OEM you may have spent hundreds of hours mapping an ECU to generate the same power at altitude that people get at sea level, and that's probably the real reason why there's not (much) of a change.

WSIR in California is roughly in the 2300' range, so the changes will be less drastic than the Denver comparison, but they will be there.

We can't say it's all in the turbos efficiency, or all in the atmospheric density because there are things that change at damn near ALL points in the system.

If you're losing power because you didn't have enough headroom in your turbo system, then your turbo system is just too damn small to account for the altitude change. 100% accurate. You'll lose power and no amount of mapping changes will bring it back unless you switch to a fuel that needs less air to burn. So if you're on the ragged edge of what you can get out of an AVO or Greddy kit at sea level, then you're kinda fucked when you decide to drive through colorado and get a dyno sheet at every dyno shop you pass...

But if we're being realistic, we'll admit that we've known for a hundred years that going up in altitude means less power. It's always been that way. Unless you spend the time adjusting your tune to make similar power at altitude the way Mercedes Benz and BMW apparently have, it's going to continue to be that way.

[Jackson Racing]

In other news...

Jackson Racing Engine Oil Cooler Kits are now shipping!
Press Release on Monday.

-Oscar Jr.

[tendogy]

I had given up hope that you guys would meet the February deadline, and here you are squeaking under the wire! Nice job.

[CSG Mike]

Originally Posted by tendogy

I had given up hope that you guys would meet the February deadline, and here you are squeaking under the wire! Nice job.

Today, I discovered, I can fit quite a few boxes in my S2000.

[enivid]

Originally Posted by CSG Mike

Today, I discovered, I can fit quite a few boxes in my S2000.

UPS just notified me I have a package from CSG arriving on Wed. Oh what could it be? Feeling sick. Might have to take that day off.