[NEVER ENUF]

I have a question for the experts, or those that run RB's at altitude. I am wondering what I can realistically expect to gain with these at altitude (Denver area-6500ft) and what is the max boost they are reliable to?

The reason i ask is because obviously the turbos have to spin a lot faster to make the same boost up here. It is evident that the stock turbos are working overtime even at moderate boost levels. I wonder how much of a buffer the RB turbos will give before working too hard also?

It amazes me that I see Skylines up here at the track running mid to high 11's on stock turbos, that MUST be nice.

Thoughts?

[135Pats]

It’s all about how much you’re spinning approaching redline, and on that front I wouldn’t feel comfortable with much more than 18 PSI or so up top. I saw a dyno sheet a few days ago that literally didn’t taper, 21PSI at redline…RB’s are great, but that type of boost curve is going to smoke them IMO.

R35 GTRs are ridiculous, that's the bottom line on that front.

[Carl Morris]

If I were going with upgrade stock frame turbos at high elevation (and I may at some point), I am leaning heavily toward the Vargas Stage 2s with the GTX style wheels. The increased airflow on the compressor side would be particularly welcome for those of us at high elevation. I still wish Forced Performance would get in the game...

[raceyBMW]

I believe there is one person on here (maybe in Colorado Springs) that is running RB's. You might want to search around and contact him if you can figure out who it is.

Any upgrade you can do at altitude to help the car breath better, especially upgrading the turbo, well help. Upgraded turbos will run more in their optimum efficiency range than the stock turbos would when tuned, and probably create less back pressure and increase VE.

[NEVER ENUF]

Yeah, I know the stock snails are way too small. I am hoping maybe the RB upgrade will be enough to not fall off too much or work too hard, but would hate spend that kind of money and just end up stressing these turbos and being out $3K.

Seems like there aren't too many options to make bigger power up here and still figure out the emissions thing. Swapping to a single rules out throwing on the stock downpipes, so stock housing turbos seem to be the only option. Any others with experience cranking them up at altitude?

[Joshboody]

19psi at sea level is pressure ratio 2.3… so at 12psi baro that’s 15.6psi gauge pressure or 27.6psi absolute. What do stock turbo guys run at 6k rpm… and what WGDC? You can’t really compare WGDC though since the vac pump efficiency is a % of baro… so equivalent WG pressures would equal higher DC at altitude.

[Rob@RBTurbo]

OP, this RB Turbo customer made these numbers at 5500ft just recently:
http://www.e90post.com/forums/showthread.php?t=856461

FYI.
Rob

[NEVER ENUF]

Thanks Rob, I appreciate you chiming in. If that really is at 5500 ft I would wonder what the correction factor is. At altitude the dyno really tends to over correct turbo cars. Even on my Cobra a few years back that was supercharged it dyno'd 493HP up here, but uncorrected it was only 380.

since the correction factors seem to be fixed around Elevation and air temp on most dyno's it tends to artificially inflate the corrected numbers on turbo cars because they don't really lose as much power. Only way to really see what's going on at altitude is to look at uncorrected numbers, as that is what is really going to hit the road and make the times.

The other thing I noticed, is this the first chart I've seen where the peak power dropped so quickly after 5500 with your upgraded turbos. While the other thread seemed to focus on fueling, I would think it might be more altitude related.

What are your thoughts? I don't mind a bit of drop off, but don't want to be working the turbos too hard...

[GeorgeSmooth]

Originally Posted by NEVER ENUF

I have a question for the experts, or those that run RB's at altitude. I am wondering what I can realistically expect to gain with these at altitude (Denver area-6500ft) and what is the max boost they are reliable to?

The reason i ask is because obviously the turbos have to spin a lot faster to make the same boost up here. It is evident that the stock turbos are working overtime even at moderate boost levels. I wonder how much of a buffer the RB turbos will give before working too hard also?

It amazes me that I see Skylines up here at the track running mid to high 11's on stock turbos, that MUST be nice.

Thoughts?

I have been running mine at 5600ft 20psi peak tapered to 17.5 for the past 25,000miles with no issues. You can conservatively see 450whp and up too 470whp at dynos at my part if the world. Stock turbos tap out at around 410whp here.

[Carl Morris]

If the turbos are completely maxed out the standard correction factors actually are valid (and are usually 20-21% or so around here). But since turbos usually aren't totally maxed out Harvey usually just uses a straight 15% factor for everyone just to get in the ballpark of what they will see if they dyno again at sea level. My guess is that guy was using the 20+% factor.

[Christopher110]

It’s all about how much you are rotating nearing redline, sydney limousine | limo services | sydney limousine service and on that front side I would not understand much more than 18 PSI or so up top..