So you are saying that with bigger tires at this alt. that you can run the 2.2 pully with no problem? We have not had a problem yet but I don't need to start with any.

What I am trying to figure out is why I went from 7 to 10 psi. I guess I will have to see how much the vac. and boost the stock pully will make.

 

Too weird...
If I were you I would be running to get some way of getting some AFR readings and go from there. Your truck should sound like its got marbles in it!?

I understand the principals of F-I and why higher altitudes should be "safer" for our lean engines but when I had my White 4R (2nd Gen S/C with no fuel mods) it ran like a champ at sea level. The minute I start to head up in ALT there was no way I could touch boost w/o major ping (any ping you can actually hear when driving is really bad). The only conclusion I can think of (in my limited experience) is that the same amount of air is going into the engine but b/c of the lack of oxygen the explosion is not as effective which is essentially like running lower octane fuel which in turn causes the ping. What do you guys think. I sort-of pulled that out of my "hind-end" so feel free to prove me wrong but it makes sense right now anyway :great

 

Many people have said the exact same thing to me, in that engines ping less at altitude. But, in my experience I had the same thing happen to me- the higher the altitude the more the ping.

Not sure what the explanation is I don't know, but the experience is what it is.

 

I know that I am dumb but what is a AFR reading?

I was thinking that the higher the alt. the less dense the air which would mean that the 4runner would be breathing in less air. Correct?

 

AFR is your engine's Air/Fuel Ratio; this can be measured by special equipment, which doesn't come stock on the vehicle. When a supercharger gets put on the engine which is used to running naturally aspirated, it will tend to run much too lean, leading to ping, high EGT's, and possibly chatastrophic detonation.

It is true that the air at altitude is less dense than at sea level, but it appears to me that the less dense air doesn't help prevent ping/spark knock, but actually makes it worse.

 

Hi all! I just found this thread...


Brian, no problem reposting the pic - that's pretty much what it's there for.


my86yota:

• do you remember which line you put back on?
• What happens if you take it off again, does it drop back to 7?
• Which boost gauge is this?
• and like TRDatVT asked, what does the gauge show at idle?

 

Brian what octane do you have there? I seem to remember the premium being 90 around there.

 

I always run 91. You can find 90 in some places, but if the station only has 90 I move on to the next one... As a general rule I always run Shell V-Power 91, or Chevron 91.

That's an interesting point to bring up though, because you can get 93 at sea level, but the higher you go the lower the "premium" octane gets...

 

Sorry about taking a while.

I don't remember exactly which line it was. One of the one on the back side.
Once I see the 4runner again I will know which line it was and if it changes the boost.
The boost gauge is a ultra lite.
The gauge shows 15 psi vac.

 

Hmm... 15 inhg (vacuum) is low, should be 20 at idle. Add that to you showing 10psi on a 2.2" pulley and I'm wondering if the needle isn't physically off-kilter on the dial.

With the engine off, does it show "0"?

 

I dunno, I suspect the altitude "lowers" engine vacuum as well as boost. With the 2.2" pulley, I pull 13-15 inHg vac at idle and push about 6-7psi boost. However when I drove down to Tucson (2500ft asl vs. 7500ft asl) my boost went up to about 8-9psi, and vac went lower, to about 18inHg IIRC.

It's actually a little disconcerting, I kind of want to go down to sea level and make sure my vac and boost readings are a-ok...

 

So wouldn't that be called raising the vacumum to 18inHg?

 

I dunno

One way or another, in my experience the higher the altitude the closer to zero the vacuum is, which kinda makes sense because if you were in a pure vacuum (space) you would pull 0inHg of vacuum. I suspect that vacuum, like boost, drops as the air density drops.

 

Hmm, I think I'd buy that, but then it still doesn't make sense why the vacuum is down _and_ the boost is up on this guy's gauge. That lead me to think about the needle not being mechanically correctly.

 

Ok so by looking at the gauge when the motor is turned off it is reading just above 0 but not quite 1psi boost.

 

My boost gauge at 5000 ft. on top of the mountiains in VA reads about 15-17 mmhg and with my 2" pulley I read approximately 11 psi... I also notice that when I drive home (chesapeake bay area) that i tend to read closer to 17-19 mmhg which supports the idea. I think 15 is fine, wouldnt worry about it unless its smokin' or running funny.

 

huh... okay, well it is what it is then!

 

Yeah, would you trust a bathroom scale that read 15 lbs before you stepped into it.

 

The TRD Boost gauge is not known for its accuracy...

 

Ok so I installed the stock pully and it seems to run good. It is running about 5psi of boost and the vac. is still about the same at 15. Is this about what it should be running?

Thanks Brain for the pully