what compression for mild supercharger

[flexin91xj]

So after months of researching, I've decided I will be adding a centrifugal type supercharger to the stroker motor I am currently building. RIPPMODS will build and sell the supercharger bracketry to mount the Vortech V-3 SCi-Trim Supercharger in place of the air conditioning compressor. My '91 XJ didn't come with factory AC so that's another plus.
My question is what would be a good safe compression ratio to use for my stroket motor? I will only be running on 8-10 lbs of boost max. I will also be using some type of forged pistons and upgraded connecting rods. Basically a safe motor to run mild boost on without having any weak links.
I will be dropping the motor in and driving it for a while before I add the supercharger. I just don't have the money to do it all at once. So I would like compression ratio that does good without the blower but will be safe from detonation once I add the blower. I will also be using some form of water/meth injection as well.
Would a CR of 9.0-1 be a safe choice?
Any help or thoughts would greatly be appreciated!
here's the link to rippmods http://www.rippmods.com/RIPP_Supercharg ... -sds-1.htm

[atias]

the centrifugal superchargers build boost as rpm increases, its not kicking in off idle like the roots type superchargers.
so a 9.0-1 is good for a mild boost centrifugal supercharger,its still gonna have nice low end when your off the boost.

[Cheromaniac]

Would a CR of 9.0-1 be a safe choice?

Yeah that'll be fine. If you add an intercooler you could run a slightly higher CR for better off-boost response.

[flexin91xj]

Will the OBD I computer be ok controlling fuel and spark on 10 pounds of boost as long as I upgrade injectors, fuel pump and use an ignition box?

[SilverXJ]

No, the PCM has no way to read when the engine is in boost, even if you add a 2 bar map sensor. What will happen is that when you hit boost the PCM will think there is no manifold vacuum and cut fuel. This is what happens when you try to do what you proposed: http://www.jeepstrokers.com/forum/viewt ... f=5&t=2474

[atias]

if you upgrade the injectors,fuel pump,and some timing control box you can get away with a FMU and a check valve in the map sensor vacuum line,
and it will work but its not gonna be as efficient as if you put some kind of piggyback or engine managment unit.
you have to put a good wideband gauge so you can monitor that every thing is ok.
the water meth will give you some detonation control ,octan boost ,and intercooling effect but don't count just on that!! the tuning must be perfect

[flexin91xj]

This is what drives my nuts and confuses the heck out of me. I thought the OBDII was the finicky of the two computers and the OBDI would learn as it goes. What can I use to control the fuel, spark, timing, and boost that works best with OBDI systems and wont break the bank. Or is there such a thing? I've read forums where the person uses a piggyback system but that was on a 2000 XJ with OBDII and a Turbo.

[flexin91xj]

So this is what I found, ACCEL DFI Thruster EFI Engine Management Systems. Heres the link
http://www.summitracing.com/parts/ACC-7 ... refilter=1
Any input or thought or other sugestions would greatly help.

Jeff

[SilverXJ]

I though you didn't want to break the bank? That Accel unit is a stand alone unit. You remove the stock PCM and wiring and install the Accel. Judging from you knowledge level, you might not be able to use it very well.

Go with a piggy back and use an AEM FIC. You will also need a wideband. Or ask Rippmods what they recommend and perhaps they could supply a piggy back with a base tune.

[flexin91xj]

That's all I thought was out there but got some knowledge dropped on me last night about the AEM F.I.C. 30-1913. That's what I'll do

[CobraMarty]

Another supercharger company just selling the hardware and no help with the tuning.

(.0 is fine. I would use APR head studs and good head gasket. You will need bigger injectors as well. How much HP are you hoping for? Stock is 190 and 8-10 lbs boost will add 50%. Are you putting in a different cam? Headers?

[flexin91xj]

I would be very very happy with 300 horses at the wheels maybe even a little less. Before I ever owned a Jeep, I had a pretty much stock '93 mustang GT. It had full exhaust including headers and no cats(when it wasnt emissions time lol), K&N intake and filter, under-drive pulleys, and it was geared to 3.73. Im pretty sure I was only pushing around 250-260 horses, but it was so much fun to drive around town and on the highway. I loved how it threw me into the back of my seat! It ran a 15.4 quarter mile up here in the mile high city of Denver.(mid 14's at sea level) And the altitude does effect a vehicles power big time! I bought the mustang in Dallas Texas and drove it to Denver, and it was night and day difference performance wise by the time I hit higher elevation.
Anyways...
If I can get 270-280 "reliable" horses on pump gas to the wheels out of my Cherokee, I would be pretty happy. I dont care about gas milage. I just want the reliability that I have with it now cause it is my daily driver. Now if I can make that power without a power adder, I would be even happier. I just dont know if thats possible without using an extreme 5.0 stroker kit. Thats when the piston walls get thin and I start to worry. Plus its a lot of custom machine pieces.
If someone out there knows of a stroker recipe that will give me a "RELIABLE" 270 to the wheels without any power adders, please inform me! I dont have an unlimited budget either but Im willing to take the time so I can get the good parts. My goal is to have some kind of stroker motor in my 2-door, 5-speed, XJ and running by the summer of 2013. So a little over a year's time.
Ive already got a used 4.0HO block(#53008405) and head(#7120) both from a '91 Cherokee. I do plan on using a bigger cam(1200-5400RPM range) and maybe possibly using the Hesco aluminum head. I like the PaceSetter 6-2-1 header. I will use ARP studs, nuts, and bolts wherever I can. My next purchase is the AEM F/IC piggy back computer and AEM digital wideband A/F UEGO gauge kit. Thinking of also using some sort of water/meth injection as well. Im still going back and forth on what kind of boost I wanna use, and if I even have to or need to. I'll probably be purchasing all of my internals from 505 Performance. http://www.505performance.com They seem to know what theyre doing with Jeep engines.