Thanks for the input.

I already have headers, high flow cat, an 2.5" exhaust all the way back. I have run my set up open at the TB to see if I could make more boost or if my filter and hose set up are causing a restriction. No change is boost was noticed. I like the simplicity of no other fuel or timing mods so once I reach a point that timing needs to be changed I will stop pushing. With the current set up I have, I would easily make 10+ psi of boost at sea level but at 6000ft and above (where my jeep is driven) I cant build that much boost. I believe a bigger TB and intake to the supercharger would add some boost but another 2psi? I spend a lot of time on the rocks and don't want my throttle any more sensitive than it is. I was hoping to stay with a 62mm TB for that reason. I was planning to install a new head gasket, new head bolts or studs, and 1.7 rockers along with the next step in upping boost. With the injectors I have now I'm still really rich at WOT and instead of bringing back fuel I'm wanting to add a little more boost. If I can't I might try to find some slightly smaller injectors.

 

According to 505 Performance, the limit of stock pistons is about 12psi. I have yet to confirm that, but.... Lol.

I gained about 2.5psi going from a 62mm to a 70mm on my Sprintex install. (5.5-6psi with 62mm and 8psi with 70mm on stock Sprintex pulley)

I go wheeling at Rausch Creek all the time and it's mud and rocks and I haven't had a single problem running a 70mm TB. Extremely easy to modulate throttle. Granted I'm running 32s on stock 3.55 gears too. Lol

 

What brand TB are you using? The cheapest I could find one was $400. Are there any that aren't that expensive? By the time I buy a $400 TB and have the a bigger TB mount custom made it would probably be the same cost or even cheaper to toss on a M90 and keep my current TB.

 

F&B/505 Performance. It's a billet TB, and that's about what they go for.

As for a custom adapter for the 70mm TB... Just have yours (or buy a second one) put in a lathe and bored to 70mm. I can't imagine that being very expensive to have done.


But, if you want to "toss" a m90 on, go for it. I think that will open up a whole bunch of headaches, but idk, maybe I'm wrong about that. Lol.

 

Crawling/trailing with the 70mm TB on the supercharger is not touchy at all. Sure, on a stock N/A 4.0 it will be very touchy. Remember when not in boost, all the air flows thru the 'bypass' port and that is 39mm and that smaller hole will 'damper' the flow of the 70mm TB when not in boost. When in boost, wide open 70mm all the way thru as the bypass valve is closed. It just is not an issue from someone who actually has a 70mm TB. If tried and you didn't like it, I am sure you can resell it for $300 all day long.

 

Hey guys have some more questions. what effect will changing gears have on supercharger performance? I know lower gears will mean more vacuum while driving because less load on the engine. So will this make the boost come on later in the rpm or with more throttle?Will I loose total boost at wot? Or Will it even effect it at all? New to superchargers. Ive been working with turbos for awhile but that's a total different setup and Im sure those principles don't apply with superchargers? Wanting to go from 3:55s to 4:10s on 31s aw4.

 

A supercharger doesn't have a lot do do with regearing other than regearing lightens the load on the engine. Before with 3.55s I spent more time in boost than I do with 4.10s.

 

If I supercharge will I still need to re-gear with larger tires? Or will the added horse power be enough for a nice comfortable ride?

 

It depends, if you live on flat ground I wouldn't regear. I do a lot of mountain driving and love the 4.10s in the hills. I would supercharge first and then see what you think. Just don't assume supercharging will guarantee you won't want to regear later. Regearing also helps take some heat and stress off of your transmission.

 

Cut another JY white hood. This one is a keeper.

 

Looks good Marty.

 

The stock throttle body used on GM 3800 M62 supercharged engines have a 69mm inside diameter outlet stock. We are using 56mm - 58mm throttle bodies stock jeep and I'm using a 62mm. The GM cars got a fairly major gain in boost and HP from swapping the 69mm TBs to 75mm. The stock-bore supercharger housings have 72mm inlets. At home porting can easily take them to 75mm. This got me thinking... I need to find a 75mm TB that will work with the jeeps throttle cable, kick down cable, TPS and IAC. Then build an adapter plate to mount that TB to the supercharger. I bet it will make more boost than we would expect.

 

Sold my SC yesterday. Made a profit. The post about lack of power after 3,000 rpm and on highway or something weighted into it. I wanted it to gain power on the highway.

Anyways, good luck everyone.

 

Noooo, sorry to hear that.

The SC will raise your hp and tq curves by 60-70 across the board. If your engine pulls to 4500, so will the SC.
IDK where you got 'lack of power after 3,000'.

 

Yeah it defiantly adds a huge increase, works great on the highway. Maybe he misunderstood some of our discussion.

Funny story, I pulled my 62mm TB and installed a stock 56mm TB and went for a test drive. To my surprise no change in boost level. I was very confused until I pulled the oem TB off and measured the supercharger inlet size, it was basically the same size as the 56mm TB. I knew I had an earlier generation supercharger because the rotors are grey instead of black, but I idea the inlet was that much smaller. I guess my next step will be to swap to a newer SC and see what that does.

All the SC's sold with the "kit" are the never style with the black coating on the rotors. Back when I bought my kit superchargers were not supplied.