So I'm at 10.5 psi with my h23 Crank pulley. (Bigger, turns supercharger faster) So anyway, as i rev past 6K RPM, the boost starts dropping from 10.5 all the way down to 7psi @7500rpm. Has anyone else noticed less than 8psi at the upper rev range? (My limiter is set at 8K with Hondata)

I'm not even sure what the "stock" boost level is suppose to be from J.R. 8.5?

 

Could the JRSC's bypass-valve seal be compromised at the high pressure you are running; so needing a better quality seal?

 

well first of all, stock boost is supposed to be at 6 psi. also i would suggest switching out the h23 crank pulley for a b20 crank pulley.

it'll be more efficient. b20 isn't too shabby. and your boost shouldnt be dropping at all, this isn't a turbo setup. which you may know. also what OTT said.

 

I'm thinking the boost loss is due to the supercharger not being able to keep up with the air flow of the engine. (Volume of air is too great compared to the ability of the supercharger) I'm fairly knowledgable about engines and boosted applications. I know its probably one of three things, but I wanted to support my theories with any actual experiences. Sooooo.

Who's got the JRSC kit on their Prelude, and what boost is it hitting? And if its higher than 7 psi, do you see a drop after 7K rpms. (Although I think the limiter is at 7200? 7600? on most stock prelude h22s. So they might not see the drop anyway! Mine is raised to 8K with the Hondata. So, I may be the only one to witness this.

CAZ? I hear you've done a few of these before. Experiences.

SHark Cohen. HELP!

 

Damn. I talked to Keith, their main tech there. (JRSC) That thing is only suppose to be a 6.5-7psi kit.

Hmm. So you're saying a b20 pulley? Do you know what the diameter is?

Shark Cohen. What pulley did you change out to get the 9psi?

I was thinking something like 8.5 psi. 6.5 is low. Oh well. It really only performs well up to 7psi anyway. I guess they geared it for it's max. They knew what they were doing eh? (JR)

 

Bump for a good thread

 

If you're droppin off the boost in the higher RPM's, then it's more than likely the belt slipping.

 

The twin impeller design in the JRSC may limit the high-end volume of air it can impell, It is verygood low down i hear but apparently they just cant blow hard enough at higher revs.

I still think the kit was made for that level (6psi) of boost as the seals in the bypass valve are not strong enough at the higher boost to give a good seal. If it seems like there is a sudden drop at 9 or 10psi that that would suggest the boost escaping somwhere; but if it just 'smoothly' died away then that would to me seem like it couldnt pushg the air!

So how does the boost feel whenyou get up between 9-10 then?

 

Belt slippage on a JRSC? Never heard of it! No, I agree. I'm going with the belt is probably slipping.

 

Yes, the belt could slip. In fact, both belts could slip, the one that drives the charger and the main belt that drives the ps and alternator.

The stock pressure is 6psi, normally h22 would read 6.5-8 depending upon the restriction of the exhaust. Maybe it's because that it's the h23 that it has a different reading.

 

nsxlr8, I assume you have larger injectors since your running a hondata if not you need to drop your boost now or your engine wil go bye bye. Im currently running a 9psi pulley , when I boost it goes up to 10.7 or slightly higher, I have the stock exhaust on right now because im trying to get the car through emmisions. The smaller more restrictive exhaust will show more boost and have a stronger bottom end, as the exhaust size increases you will see less boost but make more power on the top end. My friend with a 5th gen jrsc had the same problem as you , his boost would peak and then drop off like yours. It could be a slipping belt it could be engine management, it could be alot of things. First off I would put a h22 crank pulley on and see what your boosting and if it falls off or not. Im really suprised that your boost isnt considerably higher with that h23 pulley, its an inch larger in diameter than the h22 pulley which is a HUGE difference.(I believe its every 12% larger diameter = 3 psi increase) Im putting my race exhaust back on today because im suposed to be meeting with an AEM EMS Tech and were going to final tune the car and try to get it to pass emmisions. Ill keep an eye on my boost gauge to see if it drops off or not, my rev limiter is set at 9000 so ill let you know what happens, im getting ready to up the boost to 12psi probably next week. Also Im considering machining a new pulley set that will include 4 pulleys so you can run either 6, 9, or 12 psi These pulleys WILL NOT HAVE ANY BELT SLIPPAGE GUARANTEED however they wont be cheap to have machined so probably the only way I will make these is if I can get some people with jrsc s that want them and do like a group buy or something. These new pulleys will fix the belt slippage problems and you will also be able to easly obtain a new blower belt instead of spending all day on the phone hunting one down as the case is now. Also the belt will last alot longer too.

Caz

 

My three theory's are the belt is slipping. (I don't think so. They are on extra tight just for this) The larger one is a Goodyear. The other theory is exactly what was said earlier. The Diaphram can't handle very high boost.

My Strongest feeling is that the supercharger can't keep up the flow. The boost starts dropping slowly after 6Krpms. all the way down to seven.

Yes, I have 450 cc injectors and Hondata. Tuned with a wideband. I also have a stock exhaust. But, like Caz Said, It's still a much larger pulley and should keep up there in the boost.

I don't think the belts are slipping. They are quiet. I can hear them because of my full exhaust. I know, I know, that doesn't mean they aren't slipping. Still keeping this possibility open.

Also Caz. Tuning this thing for 10.5 psi is impossible. 215 Degree intake temps! (only 75 deg F ambient) It just hates that kind of psi. Your car runs silky smooth with that boost? Mine doesn't unless it's cold outside. (It's winter now, but it still gets to 75-80 here in Houston) I don't suggest it at this point anyway! I would like to stay around 8.5. Where did Sharkcohen get his pulley from?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by caz245 &raquo;</TD></TR><TR><TD CLASS="quote"> Im really suprised that your boost isnt considerably higher with that h23 pulley, its an inch larger in diameter than the h22 pulley which is a HUGE difference.(I believe its every 12% larger diameter = 3 psi increase)
Caz</TD></TR></TABLE>

Which is more proof that the supercharger should be doing more , but just isn't capable.

What pulley are you using. A smaller one on the supercharger? From where? Or a bigger crank pulley. ?

 

Actually your stock exhaust may be causing you to lose boost, whats happening is your not able to expel all of the ex gases because your exhaust is to restrictive. I ran my car down the street twice and when I came back my whole car smelled like it was on fire, lol the stock exhaust can not flow any more than around 8psi, I opend my hood and my jet hot coated headers - well the coating was burned up so the exhaust cant flow out quick enough. With my larger race exhaust I dont have this problem at all. Im using a smaller pulley on the blower right now but im getting a bigger one for the jackshaft.
My air intake temps were 210 @3500 rpm on a 74 degree day. I dropped my compression down to 9:1 and its much better now im in Arizona so I figured ill have the fun with the higher boost while its cool out and then drop it down lower when the weather starts getting hot if my cooler design doesnt work.

 

The bypas valve is a butterfly valve it works on engine vaccum and postive pressure (boost) when it sees boost the valve is closed , you may want to put a wire tie around the vac live going to the bypass valve just to make sure your not leaking there.

My change of plans : getting tuned tues at 5 pm instead of tonite.

 

[QUOTE=caz245] you may want to put a wire tie around the vac live going to the bypass valve just to make sure your not leaking there. QUOTE]


I wonder if this will boost at idle and all that. I don't think I can do that. Some other way?

 

Sorry, I didnt understand your last post? you can call me if you want,
480-614-6661

Caz

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by caz245 &raquo;</TD></TR><TR><TD CLASS="quote"> Im using a smaller pulley on the blower right now but im getting a bigger one for the jackshaft.
</TD></TR></TABLE>

What psi does your current pulley run? (The boost you will be tuning with tomorrow at 5)

 

9si

 

OH.

I thought you meant zip tie it shut! you just mean put a zip tie on the vacuum line so that I know it isn't leaking vacuum. . I already did that when I installed it. It seemed too big for the port. So I zip tied it.

 

I'll end up checking this last. If I can figure how to test it.

 

the boost hits 9-10psi right away. As soon as I stab it down low. Car hauls ***. keeps on pulling even though the boost is dropping. Doesn't work when it gets warm though, Or I've heated up the intake above 180 deg. F. It just dogs down to something closer to stock! Working on water injection, and maybe a smaller pulley than the h23, but bigger than the h22? B20? will that work?

 

You'll see a 2-3 psi drop in boost pressure after vtec engages. This is not an indication that the blower is putting out less air, but that the engine is flowing more on the high cam lobes. What do you have vtec set at? The blower is a very efficient air pump, it can keep up just fine. If you are seeing a drop in the high rpms that is not accounted for by vtec engagement, it means you have a slipping belt. A belt can slip without making a noise. I've never seen a high rpm drop in pressure as you have described on my own car, except when a belt was slipping. I've only had a belt slip on me once.

Incidently, I recently saw my "supposed" 9 psi pulley produce 13 psi on a cold winter day. Scared the **** out of me.

I swapped my passenger side jackshaft pulley for a larger pulley for 9 psi.

 

And why are you running an H23 crank pulley

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sharkcohen &raquo;</TD></TR><TR><TD CLASS="quote">And why are you running an H23 crank pulley </TD></TR></TABLE>

That's what was originally in my car. Not that I didn't have the h22 pulley's. I just wanted the higher boost.

I'll tighten the belts some more. They have probably stretched somewhat. I'll keep y'all updated.

So, sharkcohen. Your car runs fine with this boost? I can't get mine to run smoothly when it hits any higher boost than 8. It starts stuttering. (Only when it's warm) When it's cold, it just hauls ***. But this is Houston. It WILL get warm soon.