Prodigy Performance 3.6 Turbo DIY Install

[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).

[UselessPickles]

Would a supercharger just start to behave badly at altitude, or will you just get less boost?

It should not behave badly. You would just get less boost at higher elevations.

I am concerned about passing smog tests later (my truck is new enough to not worry for a while, but it will happen eventually).

The turbo kit will definitely not pass emissions tests. It won't even pass a visual inspection, because the crankcase breather vents to atmosphere. The BOV venting to atmosphere may also be an automatic fail. If you get the turbo, you'd be taking a gamble on the idea that you could modify the kit to recirculate the crankcase breather back into the air filter (through an oil catch can), swap out the lower section of the BOV for the recirculating body and connect it to the air filter, then hope that you can find a performance shop to make a custom tune for you that passes emissions tests. You might even need some custom work done to the exhaust to add a bigger catalytic converter. The high-flow cat in the turbo kit seems pretty small, and is probably bare minimum in functionality.

Prodigy has told me that they have no plans to make their kit pass emissions inspections. If you are seriously interested, call and talk to them about it. Maybe they'll change their mind if they get enough demand for an emissions-compliant kit.

[UselessPickles]

Crap... I just realized that some of my boost calculations in past discussions may have been wrong.

At some point, I had come across something saying that to convert from inHG to PSI, you simply divide by 2. It turns out that's just a rough approximation. To make it more fun, some of the boost numbers I have reported in the past were valid, and others may not have been valid, and there's no way for me to know which is which. Some data logs gave me atmospheric pressure directly in PSI (if the log started recording before the engine was started, then manifold pressure = atmospheric pressure). Other data logs required me to convert the logged barometric pressure to PSI. Sometimes I used an online conversion tool. Other times, after reading the "divide by 2" claim, I was lazy and just divided by 2. I don't know if I used this lazy approach with any of the number I actually reported online.

I do know at least that the most recent boost curves that I posted are correct (both before and after fixing my exhaust leak).

BTW... if any boost numbers were calculated wrong, they would low by about 0.2-0.3 psi

[UselessPickles]

Crap... I just realized that some of my boost calculations in past discussions may have been wrong.

I went back through some stuff and think that I have confirmed that all boost numbers I have shared were correctly calculated. False alarm

[jeepsking]

I went back through some stuff and think that I have confirmed that all boost numbers I have shared were correctly calculated. False alarm

I am using torque App and it showed today 10.9 psi once as a peak value.

Anyway i have received the front shaft and installed it today , i am really happy with it.

[UselessPickles]

I am using torque App and it showed today 10.9 psi once as a peak value.

That sounds scary. Prodigy told me that the tune is designed to handle up to 9.2 psi. It's possible that Torque just captured a very brief spike in boost as you lifted off the throttle, but before the BOV opened.

I think you need to send me a data log from the inTune so I can compare your boost to everyone else I'll PM you.

[jeepsking]

That sounds scary. Prodigy told me that the tune is designed to handle up to 9.2 psi. It's possible that Torque just captured a very brief spike in boost as you lifted off the throttle, but before the BOV opened.

I think you need to send me a data log from the inTune so I can compare your boost to everyone else I'll PM you.

Hi,

Today i made my setup same as yours Jeff and it went down to 8.3 and sometimes 7.9 looks like i am gona go back to PD setup (taking vacuum source shared with BOV for the waste gate) and i will send the data later.

Sorry i just read the post and the private message after doing your setup

[FieryRobot]

It should not behave badly. You would just get less boost at higher elevations.

But will the tuning be able to deal with it successfully? That's the 'bad behavior' part I'd be worried about. If it's just less boost/power, I'll live.

Prodigy has told me that they have no plans to make their kit pass emissions inspections.

Damn. That might be the deal-breaker for me. At least the SCs are trying to get CARB compliance. Though, they've been in that state for some time now...