I've got an Evo IX that I use for rallying and hillclimb. For now, I'm on the stock turbo, with the traditional bolt-ons (intake, downpipe, exhaust, IC, IC piping, walbro), and I just got ARP head studs installed. The car is tuned for E85.

In Denver, I was tuned for 22psi on the first go-around, and ended up with 358/342.

This past weekend we had our first race at high altitude (9000 feet at the bottom), and as expected spool was a bit slower, but what surprised me was how little boost the car would make. I thought I'd be able to turn up the MBC and get back to the 22psi I was tuned for, but no such luck. I assume that I was getting the turbo to flow all the air it could.

Here's what happened: at first it would spike to 19psi, then immediately fall back to 15psi. I think what was happening is the boost controller setting was asking the turbo to make more boost than it was capable of, so it was just superheating the whole system. I dialed the MBC all the way back to WG base pressure, ~10psi, then slowly worked my way back up. I was able to get the turbo to spike to 20psi and hold 18psi. So is this the best I can hope for? My next race, PPIHC has a start line at 9400 feet, and finishes at over 14,000.

What I'm hoping to see here is a listing of what boost the stock turbo is capable of at different altitudes. So, if you've ever had your wastegate line pop off and your turbo spin to its max...or you're just nuts and wanted to see how high it would go, please post up elevation and max boost seen.

Thanks,

Dave

 

Try shortening the threaded wastegate actuator rod four complete 360* turns.

 

Dave, we have a ton of info like this on RMEVO.com and ColoradoEvo.com. You won't find much in the Evo General forum here, since most aren't from our altitude.

Down in the 5000-6000' area, we don't have trouble running high 20s on E-85, so your results seem a bit abnormal unless you are only running at rpms above 4500-5000rpm, at which point you would never see peak boost anyway.

 

Have you thought about doing some road tunes up at those altitudes? You're talking about doubling your altitude there. Thats like doing a tune in Death Valley and then heading straight to Denver lol

And +1 on what Warr said, something seems off. Many EVO's around here on the corn with 26-30psi. 26 myself until my studs get put in

 

Street tune sounds like a good idea, but finding someone to tag along with me as I search for a road at 9k+ feet probably isn't that feasible. In addition, the car isn't street legal, since taking it to the state for salvage inspection isn't something I'm looking forward to.

It could also be that I'm not able to build the boost at low enough revs that I'd see the boost spikes to 28-29psi like we see in Denver/ColoSpgs.

Dave

 

Davek? Pm me, I know a tuner who would be super stoked to get you road tuned for your needs. He is very competent, especially with e85. 2 people who replied to this thread use him *thumbs up*

 

If you map out the compressor, it will tell you pretty definitively where the turbo would choke.

Turbochargers are pretty much inlet air velocity limited. This means as your density drops (hotter air/higher elevation) the mass flow rate drops because the velocity remains nearly constant. The drop in boost pressure is merely the air pressure the motor needs to ingest that mass airflow rate under those conditions.

Get a bigger compressor wheel. Something like an FP white rabbit. Smaller turbine + larger compressor (within reason) works considerably better at elevation then they do at lower elevation because the larger compressor actually provides the reserve airflow capacity to make the turbine wheel the restriction and not the compressor wheel.