Turbo talk

[MikeGyver]

It's an automatic transmission, so when you punch it the rpms immediately start to climb, the pcm notices the rapid change in tps and map and then commands a downshift, by the time it disengages and engages in the new gear, the rpms are somewhere higher, that's why you see the rpm needle moving before the mph.
If I lock the car in 2nd gear and do a pull from a very low rpm, full boost was developed by 3k.
The video doesn't illustrate this very well because a downshift always reengaged at like 4k, then once there's a load again it can start building boost.

You can see the vacuum snap to zero the instant the throttle is opened, then pause, then as soon as the downshift completes and grabs you can see the boost shoot up very quickly.

 

[MikeGyver]

Here's a fun video lol. In this one the car has to flash past the low rpm stock converter, then once it does and gets to boostable rpm the tires light up and it sounds like a cut air compressor hose.
If/when I get this going again I'll consider buying an appropriate high stall converter. Turbos absolutely loooove automatics with a correctly stalling converter.


[video=youtube;8hvxUaadk1M]https://www.youtube.com/watch?v=8hvxUaadk1M[/video]

 

[TurboMinivan]

could you go into specifics here? I vaguely knew there were two or three different sorts of superchargers, but I didn't realize there was a significant difference in the effects of each.

A centrifugal supercharger is essentially a turbocharger which is belt driven rather than exhaust driven. No surprise, then, that it looks like, well, half a turbocharger. The compressor and its housing will be virtually identical to a turbocharger's hardware.

A typical centrifugal supercharger:

A positive displacement supercharger, OTOH, is what you often see mounted in the V of a V8 engine. Inside are two rotors that create boost. There are actually two different types or classes of positive displacement superchargers:

1) Roots. A Roots supercharger uses a pair of rotors (with an equal number of lobes on each) that basically just 'fan' or 'blow' air through the housing faster than the engine can ingest it. This backup of airflow creates pressure in the intake, which equals boost. This is why Roots superchargers are often nicknamed blowers.

A typical pair of rotors in a Roots blower:

2) Lysholm (or twin screw). From the outside, these looks just like Roots blowers. Inside, however, they are vastly different. Twin screw superchargers use advanced helix-style rotors, and these complex shapes actually compress the air as it passes through them. These rotors usually have a different number of lobes compared to each other. As a result, twin screw superchargers tend to be much more efficient than Roots blowers (ie, they add less heat to the charge air than a Roots blower does). This advanced engineering comes at a price, as a twin screw supercharger has a higher price tag than an equivalent Roots blower.

One example of rotors in a twin screw supercharger:

When it comes to turbo vs centrifugal supercharger vs positive displacement supercharger, each has advantages and each has drawbacks. You should study all of them and decide which one has strengths that match your desires. That will be the best choice for you, Kevin.

 

[dutchman]

Bumping this up, as I've got a related question. On the topic of intercoolers, what would be the best option for the low speeds of rock crawling air-to-air or water-to-air?

 

[TurboMinivan]

On the topic of intercoolers, what would be the best option for the low speeds of rock crawling air-to-air or water-to-air?

First, I'm very happy to see this question. Intercooling was long looked upon by the general public as an 'optional' aspect of forced induction. Nothing could be further from the truth. When you add an intercooler to a turbo or supercharger system, it is not the icing on the cake; it is more cake.

Air-to-air and water-to-air each have strengths and weaknesses. For a street-driven car, air-to-air is almost always superior. For a dragstrip-only vehicle, water-to-air offers some compelling possibilities that air-to-air cannot physically match.

Rock crawling sits between those two extremes. Personally, I would still lean heavily toward an air-to-air setup. Once installed, it will be trouble-free and should function very well. You may want/need to create some ducting to ensure maximum thermal effectiveness of the core, but this extra effort would certainly have a worthwhile payoff.

Some may look down on this opinion, claiming the need for a fan to pull air through the IC at low speeds. While that may be true, don't forget that a water-to-air setup would have a similar need for a fan to pull air through the water heat exchanger(s), also. So unless your power needs come in bursts of 30 seconds or less and you have significant time between these needs, I'd still say air-to-air will be superior even given the low-speed nature of rock crawling.

 

[Kevin B.]

Mmm, cake.

 

[mombobuggy]

Mikes Camaro looks like a fun Ride.

 

[TurboMinivan]

Mikes Camaro looks like a fun Ride.

Sorry that I can't post in kind. A friend of a friend got good video footage of my Caravan making a 13.5 pass at RMR, but I never was able to get a copy of it.

 

[Trate D]

I use to have some footage of your van from back in the day. I'll have to check my computer.

 

[Troop92]

Stumbled upon this thread, recognized a name - Rick Squires is a college buddy's uncle. He (buddy) had a 2nd gen Tacoma with a remote turbo, thing was crazy quick, had a fun sound to it as well. He wheeled it pretty hard, I'll ask him about longevity or if water crossings were ever an issue or anything. Not sure if he still has it.