10-25-2013, 11:01 PM #1
Need some help understanding supercharger upgrades.
This is for the 04 RXP with mods in signature.
The plan over the winter is a supercharger upgrade, bigger injectors and impeller I do not plan on upgrading the ECU and valve train for a higher rev limiter. I would like to get into the low 70s with some arm straightening acceleration while still keeping the machine very reliable. I would sacrifice top speed for acceleration.
I have been researching supercharger upgrades and my head is spinning. A common upgrade is an X model charger and 42lb injectors. This is probably the most expensive option even though I can get a great price on a new charger from my dealership. Another option is a new wheel in my existing charger and bigger injectors. Am I correct in my assumptions that the highest boost at 8100rpm along with the correct fueling will give the best power upgrade ? The specs on the Riva and R&D wheels all seem to be around 9lbs at 8100rpm where the ET127 is 11lbs at 8100rpm. On the surface the ET wheel seems the best bang for the buck and after reading Greenbullets build thread he really likes the 127 wheel. Anything I'm missing here ? The current charger in the ski was rebuilt by Jerry about 5 months and 15hours ago so I feel comfortable with just a wheel upgrade at this time.
What is stock boost ?
What is the difference between the 185 and 215 chargers just the teeth on the drive gear ?
If I do the SC upgrade what do I need for impeller pitch ?
Sorry for all the questions just trying to learn all this 4tec stuff after owning two strokes for the last 10 years.
10-25-2013, 11:18 PM #2
Hey Chris. Kevin "greenbullet" has gone threw the whole RXP modding thing as have I. Trust me I know. I have been there for every step of his mods. In my quest for speed I left the RXP platform in favour of the conversion. Listen to him because he has been there and done that. The best bang for the buck for sure is the ET 127 wheel, #42 injectors, Fizzle ic and a Solas 15/20. It's hard to add one mod without another supporting mod or two. What I have suggested to you should get you anywhere from 73-75 mph.
Last edited by h2jim; 10-26-2013 at 12:00 AM.
10-25-2013, 11:37 PM #3
Boost on a stock 215 charger is 7-7.5 lbs.
10-26-2013, 06:29 AM #4
+1 with h2jim. I have that set up now with Kevin's and h2jim's help as I to was new to the 4tech's. Pretty much a bullet proof setup. I have added the freebies and a 4" rear air intake. My best to date is 77.6mph @8160rpm. I do see about 10-11lbs boost on my gauge. Good luck! Need help just ask. Pretty easy install if your somewhat handy. Have 4"front air intake and filter if your interested. Would just need the sc adapter. I also have my pitch numbers. Might be able to save you a couple pump pulls maybe. Had mine off 4-5 times to get it right. Pitching also pretty easy once you understand it.
10-26-2013, 06:48 AM #5
The et127 if you think you will stay happy with it for a while otherwise a x charger has more potetial for mods down the road.
Drop a et137x4 wheel into a x charger bam 14-15 psi
10-26-2013, 07:18 AM #6
This is really fairly simple. Assuming you do not have any leaks in hoses and connections, at WOT, for any given RPM you will get a very predictable pressure in the intake. The stock wheel will produce
3.1 lbs of boost at 5000 rpm
4.9 lbs of boost at 6000 rpm
7.0 lbs of boost at 7000 rpm
10.3 lbs of boost at 8000 rpm
11.0 lbs of boost at 8300 rpm
If you continue to increase RPM, the boost will continue to rise at this same rate. How high do you want to spin the motor?
The red line in and in the green circle this screen shot.
These were all about 600 foot elevation. A larger blower will get slightly higher boost numbers at any given RPM.
Hope this helps
Last edited by whittlebeast; 10-26-2013 at 07:42 AM.
10-26-2013, 07:19 AM #7
chris... stay with the 127 you will see easy 74-75 mph... add a ride plate and more prop pitching your up to 77-78 mph... ive gone threw it all 127.. 137... and now 140. H2jim has been there the whole way as we have cottages close and ride the lakes every weekend. rxpjays ski is running real well for the mods like jim and I have suggested for him when he was starting out. The 127 is a easy go ride wheel but when you get into anything bigger you will need a RRFPR or some kind of fuel controller with bigger injectors to run a bigger charger. need anything else just ask- kevin
10-26-2013, 07:27 AM #8
10-26-2013, 08:22 AM #9
10-26-2013, 08:39 AM #10
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