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The one thing to remember is the all motor Pistons have thinner material at the domes. Go read Muckmans thread about his high compression (13.5:1 IIRC) turbo setup. He was running "shelf" high compression Wisecos with the lightweight pins and he had problems with the pins deforming. He moved up to a slightly heavier straight wall pin and it still bent and caused the engine to throw a rod (I have his old block). From what I recall he also had issues with the forging thickness of the dome and wound up having Wiseco make him a custom set of high compression pistons with a much thicker dome and their thickest straight wall pins. I don't think he had an issue with the skirt design though.
The next major thing I would work on is a proper intake. Having the charger ingest the hot air from the radiator and around the header is killing compressor efficiency and intercollegiate capabilities. I would try my best to get the filter as close to cold air as possible even if it means running piping all the way to the passenger side frame/wheel well area.
Whatever you do though either put reflective gold foil or a reflective heat blanket on the intake tubing or possibly even ceramic coat it. The gold foil will do a good job of reflecting heat but it's so thin it won't stop all of it. They make thick reflective heat shield kits that lace around piping and do a pretty amazing job of reflecting heat. Although depending on how much room their is between the block and header you might not have a big enough air gap to use it in which case ceramic coating would be ideal.
My one gripe with centrifugal chargers on small displacement Hondas is how they deliver power. Since they depend on RPM to make positive pressure they do little in the way of increasing midrange torque output, something Hondas already lack. Hell I think that even a base JRSC kit would have more midrange torque lol. I think if someone could design a stepper/overdrive pulley system for the Rotrex it would go a long way in improving midrange torque numbers but I don't know if something like that would push the unit past its reliable operation point.
Although I guess in a light enough chassis with the proper gearing and tire size you don't need much midrange. I'm building a high HP (500+) time attack civic but it takes such an aggressive tire sizing, suspension, and aero package to put that kind of power down, especially on slower tracks, that you have to absolutely drive the **** out of it.
I think from a standpoint of having fun that if you took a high compression high revving engine like a 12:1 or higher B16 with an ITB/plenum setup and ran something like this supercharger or a GTX2860R (some form of forced induction with minimal lag) that didn't break the 350-375whp level and put in a sub 2000lb chassis like a reasonably prepared CRX with a complete suspension setup, sticky rubber, and decent aero that it would be something you could take to a road course or the mountains and drive the brakes off of it without having to worry exhaustingly about driving technique or tack of traction and other issues that come with high HP FWD cars and you could just enjoy yourself.
yes sir all in all its a lighter weaker desing then most other high comp shelf pistons,thats what i was really getting at. when i was planning this out i told my tuner and sk2 that we more then likely will blow the block up with this lol but if its not tested we will never know. this car and motor is a test mule so i know what i can suggest or sell my customers.the thing that has me on the fence about these pistons is that ive built alot of motors with them and of course they held up all motor but there are a few that are spraying and making 400 hp with these pistons with zero issues. we all know that nitrous is like hitting the motor with a hammer unless you have a progressive kit witch nobody buys lol. so im ASSUMING that if it can take the abuse nitrous then why wouldnt it be able to withstand the boost pressures from a charger since it comes in slowly and isnt a shock to the motor like hitting full boost or spraying nitrous. in due time we will find out though alls i can do is keep my fingers crossed. im keeping a close eye on the motor and doing leak/comp test after every beat run and shes taking it good so far.
the intake will be taken care of like i said before its a work in progess,i run my own shop and only work on this car for a couple hours a week when i can. my plan is to use the supplied elbow from kraftwerks and run it under the blower and into the front bumper on the drivers side. i like to keep my bay clean so definately dont want to run it accross to the other side although ive seen it done like that and it doesnt look too bad. personally i think underneath and into the bumper is the best bet. it doesnt have to travel in between the block and header that way.
i drag race so i dont notice the lack of low end/midrange all the autocross guys keep mentioning. how early does a jackson style charger start making boost? im not too sure about partial throttle but at any given rpm above 2k once i hit 50% throttle the car instantly makes 7psi so getting out of a corner shouldnt be too bad imo but i have no clue on that subject as i never autocross. the whole underdrive idea definately wont work with these as like you said it will overspin the charger. personally i know if set up properly and the boost is controlled via wastegate on charge pipe then you can definately build a mean autocross/roadcourse car with one of these, like mightymouse from australia.
Oh something I just noticed in your photo... I would heat wrap the #4 header runner ASAP. That small air gap is also causing a premature elevation in charge temps but with how close it is to that silicone coupler it's only a matter of time before the high heat structurally compromises the coupler causing it to burst or you melt through it. You'd actually see benefits all around by wrapping the header. Not only would underhood ambient temps decrease but you'd get far less heatsoak at the supercharger, intake manifold, charge piping, and other objects within the engine bay. Those alone will increase power slightly but by keeping the exhaust gases within the header hot you'll see an improvement in scavenging effect.
also I just curious but why didn't you run one of the "sidewinder" header or whatever you call them? Not only do you free up a ton of room around the charger inlet, thus making the intake easier to build and route (I thought up an insulted air box of sorts for that), but you also move the largest radiant heat source far enough away to reduce its effects. From what I've seen that style header also tends to generate a slightly broader power curve on these supercharged setups over the "long tube" 4-1.
I know the B JRSC kits loved the short runner 4-1 Kamikaze header, it made considerably more power and a much fatter power curve than your usual 4-1/4-2-1 header like DC sports and others. I would be interested to see how header designs can influence the power delivery with the centrifugal superchargers. Granted the Rotrex delivers more high rpm power and less low/mid power over a roots midrange but I think the traction drive of the Rotrex might help increase pressure production at low rpm (they still have a traction drive right?)
I'm also curious about your crank pulley, I'm assuming it's just a larger diameter pulley. However if it's something like a solid steel or aluminum pulley with no dampening I would remove it ASAP. We've seen a lot of failures on boosted engines resulting from running the CTR pulley and the aluminum under drive pulleys. The unchecked harmonics (due to the increasing imbalance with rpm resulting from the flat plane crank) tend to pound out main bearings, especially at the crank snout main.
From what I can tell he's running the base Rotrex that comes with the kit. An interesting side note is that Skunk2 owns and develops these Rotrex kits. I don't remember what the company is called A spec or something but it's owned by David Hsu who owns S2 and Grams (injectors). They also happen to be the largest Rotrex distributor.
You'd think S2 would develop an application specific header for their B Rotrex kits. I know early on people were having to modify or build their own until people found a few that fit out of the box however they might not be optimal for the setup. I know Skunk2 has the capabilities to design, fabricate, test, and revise a header design in house. I guess it depends on the demand for the product and would likely require a firm commitment from a minimal number of current kit owners unless trends show steady kit purchases to the point where potential future purchases make it profitable but with the proper application specific header you could see far better power output and a wider power curve. Might have to talk to David and get his opinion.
I also think it would be cool to throw this kit up against a B series with a large roots blower (M90 at least, Mounted in place of AC) just for giggles. B and K series have seen stout power from a larger properly engineered roots blower. I think it was D-Rob who posted a K24 with a TVS1800 or 2300, air to water intercooler, etc and it made something like 500+ and a crazy huge fat, flat torque curve. I'll try to find the thread, I think you would enjoy the read.
I can say though that this kit definitely seems more promising than the centrifugal kit that Vortech made for the B series, even if that kit had much better packaging, because power output was meh. I think it would be cool if you could put the Rotrex on a jack shaft and put it in the same area as the Vortech charger. No clearance issues or components near hot things and you could run a very efficient A2W intercooler with very minimal charge pipe length making response that much better.
My inner engineer can be a curse lol. I'm constantly looking at everything to see how to improve it. It gets even worse when I can't sleep. Like I stumbled upon someone who custom built a jack shaft for a B series mini running a roots blower that places the blower over the trans. I immediately saw flaws and started to think of a better way to do it. He over-engineered the unit using multiple pulleys to rotate the jack shaft CW when he could have just flipped the drive gears on the supercharger and that was the first thing I noticed lol.
However I am curious to see if the wrist pins survive once you start making lots of power and turning high rpm. I don't think you'll have problems with the dome forging thickness but the pin thickness and tapered wall have me worried. At high rpm/pressure under normal operation I don't think you'll have an issue but I would be worried that a significant enough detonation event would hurt the pin first. If it were me and it wasn't a lot of work to do so I would go on ahead and get a thicker straight wall pin from Wiseco and put them in before I started doing serious tuning. It's better to spend a couple of hours and a minimal amount of now to replace pins than to have to replace an engine later. Depending on the time on the engine, compression/leak down results, and a lab test of used engine oil it could also be a good time to refresh the engine before you go for broke.
I don't know of anyone running 18psi on this Rotrex unit on a B series so I'm especially curious to results over the setups running much lower pressures, especially since the engine made so much power NA (which is impressive for that kind of NA setup to say the least). How much higher can you as far as charger rpm/pressure before you're outside of its efficiency and flow limits or the physical shaft speed limit? I wonder if Rotrex posts compressor maps?
*sorry for huge quasi-rambling posts, can't sleep so I'm brainstorming*
The unit is limited to a pressure ratio of 2.5 or 21.75psi @ 100,000RPM
Airflow limit is .39kg/s or 51.58lb/min at a pressure ratio of 1.8 or 11.6psi. This means the unit is capable of generating enough airflow for just under 520 CRANK horsepower minus the parasitic drag the charger creates to spin it (not sure what kind of power a Rotrex requires to drive it)
It has a maximum efficiency of 75% and a minimum of 40%. What I find bothersome is how very small and narrow the maximum efficiency island is... It extends roughly from .14kg/s (18.5lb/min) to .22kg/s (29.1lb/min) and from a pressure ratio of 1.4 (5.8psi) to 1.75 (10.87psi). Virtually every other Rotrex unit has a much much larger center (maximum) efficiency island that both taller and wider covering a larger range of operating conditions.
In your case running a maximum of 18psi (2.24PR) gives you a maximum airflow potential of .37kg/s (48.94lb/min) which will probably yield 430-450whp depending on numerous factors. If you can get me a boost vs rpm list I could plot your application on the map to get a fairly good idea of how the charger will perform on your particular setup.
wantboost i appreciate all your input and help but you have to read what i write before you comment lol in my first post i stated that im changing the header due to clearance issues.. im aware of all the issues within the bay and working on them as i can,this isnt my first rodeo ive built alot of high hp applications. intake will be made/headers will be changed in due time i was just anxious to install the kit. as far as the pulley goes im running a dampened pulley its custom in the sense that its made to run the c38 with a 6 rib belt,witch is whats on the car and the reason why it made the 18psi.on the c38 the maximum impeller shaft speed is 90000 and im a little over 89k at redline,if i seen 21 psi at redline that would be awesome but your plot is for the c30. changing the pins is definately a good idea though as i was worried about them as well. you mentioning the turbo set up with the same pistons made it a reality so im definately thinking about switching those out.
Thanks Backyardtech, I appreciate the response. I asked because you mentioned 18psi and I noticed in the picture that you posted of the engine bay that you had a 4-rib belt on the upper idler of the kit. I am shocked that you actually made 18 psi that way with that tiny belt... without slipping.
Thanks Backyardtech, I appreciate the response. I asked because you mentioned 18psi and I noticed in the picture that you posted of the engine bay that you had a 4-rib belt on the upper idler of the kit. I am shocked that you actually made 18 psi that way with that tiny belt... without slipping.
i was surprised myself, it only slips when i slam it into 4th gear, any other gear it actually holds
I wanted to post a little update on my retune.
Setup:
kw B race kit
98 Jdm B18c R
Arp studs
Go-autoworks Kw pipe kit
1320 RMF V2 megaphone header
Rc 750s
3" exhaust catless
1st time I went to dyno I only hit 7 psi cuz the off the self pulley combo and me over looking it. 279/178 on itr pulley/120mm Charger pulley. 8500 redline
This time around I switched to a gsr crank and 110mm charger pulley and Drob at Innovative MotorWorks made some magic and pulled 361/226 out of it. Was actually a tad higher but some timing was pulled to keep it safe. 8400 redline. 93 octane pump gas. 13.5 psi
Albert Marty informed me that if I had cam gears I could of gained ~20hp from the exhaust cam.
Future plans are to go E85 and an ethanol content sensor with cam gears, valvetrain and some 1000cc injectors. Maybe build the bottom end but not sure yet. I'll hit 400+
I wanted to post a little update on my retune.
Setup:
kw B race kit
98 Jdm B18c R
Arp studs
Go-autoworks Kw pipe kit
1320 RMF V2 megaphone header
Rc 750s
3" exhaust catless
1st time I went to dyno I only hit 7 psi cuz the off the self pulley combo and me over looking it. 279/178 on itr pulley/120mm Charger pulley. 8500 redline
This time around I switched to a gsr crank and 110mm charger pulley and Drob at Innovative MotorWorks made some magic and pulled 361/226 out of it. Was actually a tad higher but some timing was pulled to keep it safe. 8400 redline. 93 octane pump gas. 13.5 psi
Albert Marty informed me that if I had cam gears I could of gained ~20hp from the exhaust cam.
Future plans are to go E85 and an ethanol content sensor with cam gears, valvetrain and some 1000cc injectors. Maybe build the bottom end but not sure yet. I'll hit 400+
Nice gains from the previous tune. How does the car drive/feel? Never driven or been in a centrifugal supercharged car, does it feels really peaky like all the power just really starts to pull after VTEC or does the low-end and mid range feel like it has way more torque than when it was Naturally Aspirated?
If you've ridden in a turbo b series car how would you compare your car to a similarly powered turbo car driveability wise/fun to drive factor.
I am pretty dead set on buying a kit for my car, just would like some feedback from personal owners. Any chance you could take me for a spin lol. There are no rotrex powered cars in my area.
Power is instant and all the way through the entire power band. Not like turbo which is a kick to the face power hit. My vtec opens at 3800rpms at 50% throttle up
Power is instant and all the way through the entire power band. Not like an improperly matched turbo which is a kick to the face power hit. My vtec opens at 3800rpms at 50% throttle up
12-14-2015, 02:43 PM
Re: KraftWerks B-Series Race Supercharger Kit (Unbelievable Gains!)
