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Discussion Starter #1
To everyone with the 3.8 supercharged jk, whether your running RIPP, magnunson, etc. how much boost are you guys running? I've got the avenger supercharger, (I know they went out of business) but I was able to get it custom tuned, etc, and it runs great. Im running 4lbs of boost maybe 5 at peak RPMs. Just wanted to get thoughts if I could/should go higher or if the shitty 3.8 won't be able to handle 6-8 lbs of boost? Thanks in advance
 

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If its an 2007, I would be hesitant. Other than that, I don't see any issues with 6-8 pounds. Get a wide band o2 just to make sure everything is working like its supposed to and you shouldn't have any issues.
 

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Single digit boost is generally considered safe on stock motors. 8 would be a good safe and fun number and definitely get it intercooled.

I am peaking at almost 9.5 and I am happy from a kit that is claimed to be 7psi.
 

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Sorry to kinda hijack the thread but what's everyone's opinion on adding a Supercharger to a motor with 85k miles on the clock? It runs strong (as strong as it can, anyhow), very little oil consumption.
 

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Running an intercooled RIPP SC with the altitude pulley at a little above sea level and getting between 6 and 8 psi. Haven't really gotten on it to see if it will go above 8 psi as I don't want to replace my auto trans yet.


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Sorry to kinda hijack the thread but what's everyone's opinion on adding a Supercharger to a motor with 85k miles on the clock? It runs strong (as strong as it can, anyhow), very little oil consumption.
I installed a roots style blower on a Miata with the same mileage - not intercooled. I ran it around for a while then pulled the blower off and sold the car and the blower. No issues. Car did not burn oil and passed smog. The blower install was completely reversed.

If I remember from the Miata boards, I don't think anyone can come up with an example where a single digit psi blower (or turbo for that matter) could be blamed for making a stock engine fail.
 

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Ripp with altitude pulley and dyno tune, have seen 10lbs of boost on the gauge but normally push no more than 5.
 

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Discussion Starter #10
Sorry for such the late reply, kinda forgot about this post. Thanks for all the advice and info everyone. Im going to 40s which is why I wanted to up the boost to 6-8 lbs. need to gain the power back somehow. Alasha it is an 08 so it'll be fine most likely. Ive never heard of a motor failing with single digit boost before either but with the 3.8 ya never know ? thanks again guys ?
 

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With the high altitude pulley I am only seeing 4 lbs from the Magnuson. I have pulled the filter to see if that helped and got up to 4.5. But for the most part, only see around 2-3. looking into a custom tune to see if that will help to up the boost a little
 

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With the high altitude pulley I am only seeing 4 lbs from the Magnuson. I have pulled the filter to see if that helped and got up to 4.5. But for the most part, only see around 2-3. looking into a custom tune to see if that will help to up the boost a little
That doesn't sound right unless perhaps you are not spinning up the RPMs enough.

Are you running a snorkel? Stock airbox?

Also check for belt slippage.

If you have too large of a diameter for the exhaust tubing, that will drop PSI as well. I would stick with a 2.5" diameter exhaust versus a 3.0"
 

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Running an intercooled RIPP SC with the altitude pulley at a little above sea level and getting between 6 and 8 psi. Haven't really gotten on it to see if it will go above 8 psi as I don't want to replace my auto trans yet.


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Same with me.
 

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I had thought that the Aeroforce gauge was reading incorrectly after seeing what you and others were getting for boost. Switched out the boost sensor as others had said that the 3 bar was not reading low psi correctly.

The 4 psi is at 5 K so that is about all there is left in regards to RPM

Not sure how to check for belt slippage. But no squealing coming from the belt. But PSC pump is throwing alignment off a little.

No snorkel and stock airbox has been modified (Lower section cut out to make way for trans cooler. But I am still running a K&N panel filter.

Exhaust is modified. Lower cats out to make way for LA. But still using 2.5 tubing.
 

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Well, how fast is the rig? Do you believe the gauge? What are you getting for a 0-60 time and how is your rig (lifted? heavy wheels and tires?, 2 door? Heavy armor?)

A 3 BAR is probably incorrect and only needed for higher boost applications. I think that the tune is most likely based on a 2 BAR so unless you get the tune updated for the 3BAR sensor then I think you may be getting erroneous readings for sure. The sensors are 0-5 volts so for the same MAP reading you would see a lower voltage at the ECU with the 3 BAR.

The Magnusson comes with a trinity. Did you try reading boost with the trinity?


for the OP:
I would go with 8psi over 6.
 

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Not all boost is created equal.

Boost is just a product of restriction. If you had two 3.8's, but one had ported heads with bigger valves, headers and such, and the other was otherwise stock, the engine with the work that improves flow would have less boost with the same size pulley/blower, BUT make more power.

It's not always as easy as "single digit boost is safe". You have to look at the size of the blower and projected power output. That's what I would be more concerned with, the max power on the stock valvetrain and rotating assembly.

You can have a smaller blower with 10 psi of boost make less power than a larger blower that only makes 5 psi of boost because of the larger volume of air it moves while working more efficiently (which means it won't produce as much heat which equates to more power).
 

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Dead on man. At the same time, my generalization is directed at the available pre boxed kits and I think those are all sized appropriately for our stock engines and can take some over clocking. In this context, I maintain that 8psi would be the most satisfying and safe number. Yes it is a generalization.

Me, I am comfortable with my pulley size. :D I was told that mine was a 7psi kit and I am seeing over 9 psi in logs and am enjoying great performance with stock drivability.

What you say -IMHO, anyway - I think might apply more to a ground up custom FI job where you spec'ing all the parts and fabbing stuff on your own. In this context, someone might be moving more air at a lower psi.

edit:
For the OP... If there is an option from Avenger to go 8psi then that probably means it is okay. Perhaps go with the largest pulley that *they* recommend and/or make available.
edit 2:
I did not catch at first that these guys were out of business.
 

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Stock is a 1BAR (up to 7.25psi) and as far as I know most bolt on kits with single digit boost levels probably include (and are tuned around) a 2BAR sensor (up to +14.5psi). The 3BAR sensor (up to +21.7psi) is typically used in high boost applications. Output is going to be 0 to +5vdc with either sensor.
 

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Output is going to be 0 to +5vdc with either sensor.
Yes but the meaning of every reading changes dependent on the sensor i.e. 2.5v on a 2 BAR tells the engine management you have ~7 psi while 2.5v on a 3 bar is saying ~12 psi. This is why things go boom when the tune doesnt match the MAP sensor. Your tune is designed around a 2 BAR. If you switched to a 3 Bar without retuning, you are running lean.
 
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