Prodigy Performance 3.6 Turbo DIY Install

[UselessPickles]

I'm hot-linking to images on my own web server ("From URL" option in the "Insert Image" dialog).

[Timmy]

[QUOTE=UselessPickles;3705]MOAR BOOST!

I now have seen boost peaking in the 8.0-8.3 psi range! Previously, I was only getting up to the 7.8-8.0 range. I seem to be on par with NOLA with boost numbers now. The highest I saw today was 8.58 psi in 4th gear."

Forgive me for asking, I'm only doing so for my own information, but it appears the boost numbers you are seeing are no better than what is seen for a supercharger with a standard pully, let alone the high elevation pully that seems to bring the boost up to 11 PSI. If I recall, the sales pitch on a turbo vs. SC was that it was suppose to spin up faster and provide more boost, but from your information here that doesn't appear to be the case? Am I missing something on this? Please know, this question is NOT a jab at anyone that has a chosen a turbo over an SC, I'm just trying to understand the differences for when it comes time for me to pick one.

BTW, JeepLab, you get that high elevation pully on yet? Any feedback? It appears you should have been seeing about a 30% increase in boost!

[JeepLab]

[QUOTE=Timmy;3727]

MOAR BOOST!

I now have seen boost peaking in the 8.0-8.3 psi range! Previously, I was only getting up to the 7.8-8.0 range. I seem to be on par with NOLA with boost numbers now. The highest I saw today was 8.58 psi in 4th gear."

Forgive me for asking, I'm only doing so for my own information, but it appears the boost numbers you are seeing are no better than what is seen for a supercharger with a standard pully, let alone the high elevation pully that seems to bring the boost up to 11 PSI. If I recall, the sales pitch on a turbo vs. SC was that it was suppose to spin up faster and provide more boost, but from your information here that doesn't appear to be the case? Am I missing something on this? Please know, this question is NOT a jab at anyone that has a chosen a turbo over an SC, I'm just trying to understand the differences for when it comes time for me to pick one.

BTW, JeepLab, you get that high elevation pully on yet? Any feedback? It appears you should have been seeing about a 30% increase in boost!

I had the SC out and separated, but I could not remove the pulley!

[UselessPickles]

it appears the boost numbers you are seeing are no better than what is seen for a supercharger with a standard pully, let alone the high elevation pully that seems to bring the boost up to 11 PSI. If I recall, the sales pitch on a turbo vs. SC was that it was suppose to spin up faster and provide more boost

I don't think anyone ever claimed that the turbo would produce more boost than the superchargers, but only that the turbo would produce more power. A turbo produces power more efficiently than a supercharger because it is using heat energy from the exhaust that would be otherwise thrown away out the tail pipe. The superchargers get their power directly from the crankshaft, so there is more parasitic power loss. Given a turbo and a supercharger that produce the same peak boost, the turbo will produce more net power to the drivetrain.

For the RIPP (and other centrifugal superchargers) specifically, even with the 11 psi high altitude pulley, you only get that 11 psi at 6500 rpm (and only if running down near sea level). The chart I posted with the RIPP boost curve appears to be with the high altitude pulley, because it gets up to just over 10 psi. Compare that boost curve to my boost curve. If the additional boost of the high altitude pulley being run at low elevations is enough to catch up with or surpass the power of the turbo, it will only beat the turbo near redline.

Somewhat unrelated, but speaking of high altitude pulleys...

The intent of the high altitude pulley is to compensate for thinner air at higher elevations, and produce the same amount of boost up there as the normal pulley would produce near sea level. With a given pulley, a supercharger will lose boost as go up into higher elevations.

The turbo, however, adjusts to changing elevations automatically. Its boost is controlled by a wastegate, which is calibrated to open up when boost pressure exceeds a fixed amount of pressure above ambient pressure. My turbo will produce about 8.2 psi peak boost at sea level, and up in the mountains, without making any adjustments.

[Pznivy]

The turbo, however, adjusts to changing elevations automatically. Its boost is controlled by a wastegate, which is calibrated to open up when boost pressure exceeds a fixed amount of pressure above ambient pressure. My turbo will produce about 8.2 psi peak boost at sea level, and up in the mountains, without making any adjustments.

This is why planes are turbo props. You couldn't use a supercharger on a plane. You'd crash.

[FieryRobot]

But you can add a wastegate to a supercharger, no? Especially a centrifugal one.

[Timmy]

I don't think anyone ever claimed that the turbo would produce more boost than the superchargers, but only that the turbo would produce more power. A turbo produces power more efficiently than a supercharger because it is using heat energy from the exhaust that would be otherwise thrown away out the tail pipe. The superchargers get their power directly from the crankshaft, so there is more parasitic power loss. Given a turbo and a supercharger that produce the same peak boost, the turbo will produce more net power to the drivetrain.

For the RIPP (and other centrifugal superchargers) specifically, even with the 11 psi high altitude pulley, you only get that 11 psi at 6500 rpm (and only if running down near sea level). The chart I posted with the RIPP boost curve appears to be with the high altitude pulley, because it gets up to just over 10 psi. Compare that boost curve to my boost curve. If the additional boost of the high altitude pulley being run at low elevations is enough to catch up with or surpass the power of the turbo, it will only beat the turbo near redline.

Somewhat unrelated, but speaking of high altitude pulleys...

The intent of the high altitude pulley is to compensate for thinner air at higher elevations, and produce the same amount of boost up there as the normal pulley would produce near sea level. With a given pulley, a supercharger will lose boost as go up into higher elevations.

The turbo, however, adjusts to changing elevations automatically. Its boost is controlled by a wastegate, which is calibrated to open up when boost pressure exceeds a fixed amount of pressure above ambient pressure. My turbo will produce about 8.2 psi peak boost at sea level, and up in the mountains, without making any adjustments.

Thanks Pickles, food for thought when making a decision between the two.

[UselessPickles]

But you can add a wastegate to a supercharger, no? Especially a centrifugal one.

Technically, yes, you could setup a supercharger system with a wastegate (or some sort of precision bypass valve) on the intake somewhere after the supercharger. Then you could use a smaller pulley wheel to over-spin the supercharger some, while relying on the wastegate/bypass to limit boost. With a centrifugal supercharger, this would give you peak boost before redline, then hold peak boost up to redline. With other types of superchargers, it would just over-work the supercharger constantly unless you drove up to a higher elevation.

The big difference between this idea and how a wastegate fits into a turbo system is that on a turbo, the wastegate limits the speed of the turbo. The wastegate bleeds off exhaust, around the turbine side of the turbo, limiting the turbo speed, and indirectly limiting boost. With the supercharger setup, the wastegate would be directly bleeding off boost pressure, but the supercharger would still be spinning faster than necessary to generate the controlled amount of boost. Faster supercharger = less efficient = more heat.

This variable ratio ProCharger looks pretty cool, though: http://www.lsxtv.com/news/procharger...-supercharger/

[gbaumann]

Technically, yes, you could setup a supercharger system with a wastegate (or some sort of precision bypass valve) on the intake somewhere after the supercharger. Then you could use a smaller pulley wheel to over-spin the supercharger some, while relying on the wastegate/bypass to limit boost. With a centrifugal supercharger, this would give you peak boost before redline, then hold peak boost up to redline. With other types of superchargers, it would just over-work the supercharger constantly unless you drove up to a higher elevation.

The big difference between this idea and how a wastegate fits into a turbo system is that on a turbo, the wastegate limits the speed of the turbo. The wastegate bleeds off exhaust, around the turbine side of the turbo, limiting the turbo speed, and indirectly limiting boost. With the supercharger setup, the wastegate would be directly bleeding off boost pressure, but the supercharger would still be spinning faster than necessary to generate the controlled amount of boost. Faster supercharger = less efficient = more heat.

This variable ratio ProCharger looks pretty cool, though: http://www.lsxtv.com/news/procharger...-supercharger/

I think Pickles is spot on. And, I don't mean to hijack this portion of the thread but since we're talking about bypasses and wastegates and how to make desired power I thought I'd "share."

The engineers for these power mods are much smarter than me so I'm sure there is a good reason for bypassing superchargers. I'd just like to know what it is. I understand wastegate operation on a turbo. The turbo boost is not linear with exhaust flow. There's no ideal blade pitch for low RMP through high RPM. Pick a good one for lower RPM operation which would produce too much boost at high RPM and adjust by bypassing exhaust. It's elegant. Makes sense to me, that is, unless the wastegate is eliminating boost altogether which I presume it isn't.

But the bypass on my supercharger is binary (in the case of Magnuson). You're either putting boost into the engine or your're not. There's no middle ground according to Mag. The bypass closes when manifold pressure is ZERO which is pretty near WOT. Great for a dragster. But not for a daily driver. Seriously, the compressor is turning all the time. Why not use the boost better and throughout the RPM range? Again, smarter people than me I'm sure have concluded that you need boost to get you from 0-60 (assuming that you've got your foot all the way to the floor) but you don't need boost when you get there. We'll they haven't' driven my jeep. They've driven corvettes or challengers which have one big difference. When they get to 60 mph and the supercharger goes to bypass the car is still being powered by a big motor. They started life as powerful HP to weight ratio vehicles. Superchargers take them from really fast to downright irresponsible.

But that's not us. We have jeeps. Big, square, heavy, full framed, solid axle, locking differential, large diameter tire jeeps. We started life under powered and overweight. I want boost at part throttle so when I speed up from 40 to 60 mph or 70-80 mph the truck accelerates with confidence. And I don't want to get that by opening up to WOT. There's no need for it. It just causes my auto trans to downshift. Heck, if I want to increase acceleration by lowering gears then I'd put 5.11's in the diffs and accelerate in third gear at around 5 thousand rpm's. I'm sure she'd pin me in the seat and I don't need a supercharger or turbo to do that.

So I've made a decision. For those of you who know that I'm struggling with the "lift to sift" issue I've found new PCM that I can install that will finally control my auto trans. I'm going to have it installed for me after the new year. Good new is it should meet my need for better shifting and all-time power. The catch is the PCM costs $25,500 to install and comes with a 6.4L hemi.

[FieryRobot]

The catch is the PCM costs $25,500 to install and comes with a 6.4L hemi.

Ha! That certainly is one approach.

I'm liking the benefits of Turbo more and more, especially since my driving can take me into the Sierras for skiiing, so we're talking about a range from near sea level to 10K ft. Seems like the turbo would cope better. Would a supercharger just start to behave badly at altitude, or will you just get less boost?

The other side of this of course is that the install is definitely very involved compared to the SC, and being in CA I am concerned about passing smog tests later (my truck is new enough to not worry for a while, but it will happen eventually).