iam know living at a higher altitude which is 3300'feet above see level ive noticed that in a 3erd gear pull or 2nd gear pull i hit full boost between 3900-4000rpms but what i dont understand is why in 4th and in 5th gear pulls i see full boost comes in at 3500rpms is it altitude afecting my slower spool up in the early gears?
thanks

 

i meant sea

 

bump

 

yes, air is less condense so the turbo has to further compress it than if you were near sea level where the air is more condense, thats why almost of hill climb and rally cars use turbo chargers, we have an advantage over NA

 

ok but why do i see full boost at 3500rpms only in 5th gear??

 

Yes the altitude affect your spool up and overall boost output. Your spool up seem a bit slower though. I recorded the following on my car:


21psi in 4th by 3000rpm
25psi in 5th by 3000rpm
25psi in 6th by 3000 rpm

First, second and third the engine revs too fast and the boost can't catch up with.


I went all the way through the top of Pikes Peak(12000ft) in Colorado Springs two summers ago in a WRX and the car couldn't spin the turbo in second gear. I had to do the las 3-4000ft in first gear. Altitude killed my FP18G (forced performance) ported and poslihed turbo performance.

Let me take the opportunity to say thanks for the cool videos you put on this forum in the past.

Carlos

 

thanks again now this gives me peace of mind and i will be posting more vids in the following months...

 

The rate at which exhaust gas driven superchargers(turbos) "spool" is not directly related to the revolutions of your motor´s crankshaft(RPM´s). Conversely, belt-driven and gear-driven supercharger´s spin, or rotation is directly related to the crankshaft´s revolutions.

The spool of the turbo is driven by the flow of your motor´s exhaust gases and not directly off the nose of the crankshaft. In third gear your motor is "pulling-through" the turbo. The engine because of gear reduction in 3rd, is revving up faster than it does in 4th and 5th, hence it "pulls-through" the turbo.

I dont know, cause I dont drag race, however, Ill bet that if you were to just roll on the throttle in first gear from idle, that is a zero-boost, 60 ft. walk-out, and then roll it on, that it would be hard to reach peak boost before having to shift to 2nd gear, unless you have some sort of ball bearing TME. I´d think that in top gear you´ll always reach your peak boost level at a lower RPM than in 3rd.

So, WRXtoEVO is right on. I think that maybe, too, your turbo might spool faster if you reduced backpressure by going to the 10.5 H.S., and upgrade the LICP. Maybe too, your -5/-5 adjustable cam gear setting, although it helps build topend power, may be hindering spool-up as well.

 

JR, I went out and did some full-throttle runs in 3rd, 4th, and 5th gears and I got the following results, starting at 2500 RPM and flooring it until max boost(18.5) was reached:


3rd...............3500 RPM
4th...............3200 RPM
5th...............3100 RPM

I dont think this is too bad considering large FMIC and 280 cam(s). Altitude: 2700´ above sea level.

 

JR, before you moved it was the same - you hit full boost much earlier in the higher gears due to more load. I guess you never noticed?

Btw, I don't hit full boost in 3rd until 4200 on my stock turbo here at 6000'. It sucks - I lost 400rpm spool from sea level (per the dyno).

 

sparky and warr thanks but this altitude sucks when i go to another city called SAN PEDRO i have a much faster car i just hate it but thanks friends...

 

I know you hate it - I lost 45whp peak and almost 70whp at 7k rpm when I moved here.

 

wow that much... and i see you are at a higher place then what i am at and wow at double my altitude i wouldnt know what to do... it sucks...
do people need a different tune when they live in higher and lower altitudes or the cars ecu accomodate to such chahges?

 

It can compensate to some degree, but at this extreme height, the boost is affected so much that I needed a complete retune.

 

so is it true that running rich like in exp: afrs being at 11.0-11.5 at that altitude makes you loose power compare to 12.0-12.5 afrs?