mastacox

Ok I've been reading a lot about supercharged 3rd gens because I am going to be buying one to combat the lack of air where I live, but I haven't found the exact answer I have been searching for (have read about 30 supercharger related threads).

So, here it goes:

You put a supercharger on the 3.4, and the fuel mixture will tend to lean out, that's obvious. The more air you have, the more fuel your system has to add to the cylinder. If the stock fuel system can't keep up, you can get a dangerously lean mixture, and you get ping, possibly engine death if driven like that for too long.

The air is MUCH thinner at 7500 ft than at sea level, obviously. So, that would mean that going up in altitude will RICHEN the mixture because there is less air available. Is this correct? I have read that some people experience no ping at lower altitudes, yet when they drive through CO for example they will tend to get ping? Is this what happens, or did I miss something? Is the high-altitude ping due to fuel starvation, or is it something else?

Basically, I'm trying to figure out if I should add a URD kit to my new car budget, or if it can be put off some as long as the SC'd 4Runner doesn't have ping problems at lower altitudes.

Thanks for your help

Mikestang

It would lean out if that's all you did, but usually installing a blower includes bigger injectors and a new computer program to retard timing (don't forget timing in this, it's going to have a direct effect on ping or no ping) and increase fuel delivery. A forced induction motor has to run richer (11:1 to 12:1) than a naturally aspirated one (13:1 to 15:1) in order to not blow up, but you can run more timing on a n/a motor than a blown one.

Your assumption is correct if you assume the fuel supply is constant, but it's not. The computer should make adjustments based on the volume of air it sees being pulled into the motor. How does your motor measure the volume of air it pulls in, mass air or speed density? Either method should really not be affected by altitude since it sees the actual volume of air the engine is sucking in and calculates fuel demands based on that (and a few other parameteres).

Generally speaking, properly tuned forced induction cars are less affected by altitude than naturally aspirated cars.

X-AWDriver

When I ran my Eclipse up heree i was able to push the stock fuel pump and injectors a little more at 6000ft asl than at sea level and some do run SCs at this altitude with no issues but a fuel upgrade kit should still be installed at some point.

mastacox

Thank you, this is the exact answer i have been searching for.

rimpainter.com

Remember, much of the issue with the 5VZ is timing. The timing is just too advanced in certain areas of the map for forced induction, thus you get HG/LR ping even at altitude (although it's to a lesser degree). When I was at the beginning stages of my tuning debacle, I would drive up to Flagstaff (which is 8000ft or something) and I would still get ping going up "the hill" until I got to 7000ft or so. Keep in mind, at that time I was running about 8 degrees of retarded timing and all the other mods in my sig. That told me a couple things: 1. I didn't have enough timing retarded in certain areas of the map. 2. Stock injectors are a serious problem, even with all the other mods. So, until I get my 305 injectors from Mark, I have the timing cranked way down (-10) in a lot of places of the timing matrix.

People are simply "playing with fire" by running the SC'r with no fuel/timing mods. EGT's will sky rocket, then drop suddenly, as will power with the stock fuel pump at WOT for sustained periods of time. I don't know about you, but the last thing I want to have to deal with is passing a big rig fully loaded with camping gear and family in the mountains and having the engine power drop suddenly.

04 Rocko Taco

Im with 96 Runner on this one, fuel kit should be in there eventually.

mastacox

Yup, I'll be getting the URD kit because it's relatively cheap insurance against major engine failure, and I'm not interested in suddenly losing power at speed, as 96Runner mentioned.

Thanks for the timing explanation.

Bennito

ttora and customtacos have many members at elevation. You can find more details on those forums (sorry YT).