boardkid280z Posted April 15, 2007 Share Posted April 15, 2007 Hey guys, I just ordered Corky Bell's books "Maximum Boost!" and "Supercharged" and hopefully they will have answers to my questions. But for now I figure I would ask you guys what you think. I am pursuing a project similar to Frank's plans to twin charge his Z. I bought a used JCR supercharger kit which should be in the mail any day. I plan on using the stock turbo/exhaust manifold setup and modifying the JCR manifold as necessary for a) fitting over the exhaust manifold+turbo, ported fuel injection similar to stock EFI. Here's my question about boost. As I understand superchargers they provide a constant ratio pressure increase, meaning if I have a SC that runs 7psi, it has a 1.5 compression ratio, because it's compressing atmospheric pressure of 14psi (approx) to 21psi. >21psi/14psi = 1.5 ratio So what happens if instead of 14psi absolute at the SC inlet, you have precharged air from the turbo at 7psi gauge or 21psi absolute. Will the SC compress that air at a ratio of 1.5 again, producing 31.5 psi(abs)/17.5psi(ga)? >1.5 * 21psi = 31.5psi absolute(abs) >31.5psi - 14psi(atm) = 17.5psi gauge(ga) So, my question is, if I setup the turbo to produce only 7psi (boost) at the SC inlet, will that produce approx 17psi after the SC with that stock SC pulley that I described above? Any replies or ideas or comments welcome. Also, Frank280ZX, I am curious if you have made any progress on your twincharging setup. I am hoping to beat you to it only because I haven't heard of anyone else having completed this setup. Anyone else have any record of this setup on an L28?? ref: (Lancia S4) Thanks guys, Matthew Brazle Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 15, 2007 Share Posted April 15, 2007 I just ordered Corky Bell's books "Maximum Boost!" and "Supercharged" and hopefully they will have answers to my questions. Unfortunately tthey are over ten years old, and have relatively dated information in them. They will give a genaeral overview, but many of the statements in there can mislead you. They were a standard and totally relavent when they were originally written, but now they are out-of-date in regards to what current state of the art technology exists. As for your question on compound charging, yes, that is about how it would work, but you will HAVE to intercool that 7psi on the turbo back to ambient or you will have hellacious discharge temperature issues on the supercharge outlet. Yes, with the turbo putting 7psiG into the SC at a 1.5:1 CR, then you would get 18.375 using your example. The total compression ratio across the powerplant would be 3:1 and your discharge from the supercharger would be 350degrees F or thereabouts giving a ballpark guess. So intercooling of the first stage of compression no longer becomes optional, it becomes mandatory. You could inject something like Methanol to take that heat out, but however you choose to do it, the inlet to the supercharger will be limited to roughly 100F maximum of you will be in sad shape with octane requirements. Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 16, 2007 Author Share Posted April 16, 2007 Thanks Tony, I'll just have to compress what I learn from the books and run them by everyone on the forums before applying it. I am definitely intercooling the air after the turbo, before the SC, I had a turbo setup on my car for about a year and had it intercooled, so I will try to use some of that setup. My roommate has a Buick Grand National and a Mustang SVO and talks about running alcohol injection or something like that. So after he does that, I might try a similar setup on my car to cool the supercharged air. My numbers are a bit generalized since I started with 14psi for simplicity's sake instead of 14.7 actual atmospheric pressure. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted April 16, 2007 Share Posted April 16, 2007 Hey Tony, do you have any recommendations for any books that might be a little more up to date? Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 16, 2007 Author Share Posted April 16, 2007 Hey Tony, did you mean that the total compression ratio would be 2.25:1 (1.5*1.5) and not 3:1 (1.5+1.5). Using 2.25:1 I get the 18.375 you mentioned. And that's how the calculations work out in my example. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted April 16, 2007 Share Posted April 16, 2007 Isn't VW looking at using a supercharger at low RPMs and a turbo at high RPMs? It would be the best of both worlds. The surpercharger for low end torque and HP and the turbo for the free HP on top end. The surpercharger would kick off at set RPM or boost from the turbo. NO TURBO LAG!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 17, 2007 Author Share Posted April 17, 2007 They are using one on the Golf and Touran(van/MPV) in Euroland - it's a 1.4L TSI. It has 14% more power but uses 5% less fuel than the 2.0L FSI (N/A). Looks like they've used it in the Golf since '05. Also, note the 10:1 CR. (All my 'facts' come from wikipedia . I've read it produces 177 ftlbs of torque from 1750-4500RPM. No turbo lag indeed. Quote Link to comment Share on other sites More sharing options...
toki Posted April 17, 2007 Share Posted April 17, 2007 bi turbo systems (2 turbos, one small, on larger, used exclusively at different rpms) have been implimented by uhhh audi? or vw? I forget for a few years now.... compounds turbocharging works under the same theory as twin charger, just with two turbochargers....tractors have been using it for years with great success, again, matching a little and a big turbo together. Quote Link to comment Share on other sites More sharing options...
turboboost Posted April 17, 2007 Share Posted April 17, 2007 bi turbo systems (2 turbos, one small, on larger, used exclusively at different rpms) have been implimented by uhhh audi? or vw? I forget for a few years now.... Also the Mazda Rx-7 TT uses that system. Basically no lag at all. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 17, 2007 Share Posted April 17, 2007 Yeah compression ratios are multiples of each other. I don't know why the hell I typed 3, that doesn't work out on my example! DOH! The math is right, what I wrote there was wrong. The total compression ratio is 2.25 (1.5*1.5=2.25) As for books.... there was this one undergraduate text that was 894 pages and was once available from OPMAP Technical Books back in the mid 90's called 'Turbocharging the Internal Combustion Engine' but I forget publisher and author. It wasn't cheap. Your better bet may be to cozy up to someone with an SAE Membership and get some of the recent technical papers on the subject. Kind of dry reading, but if you can handle the math there are no suprises! Garrett (Honeywell) Engine Boosting Systems R&D Complex isn't that far from me, and I get to talk to those guys in the course of my work... So next time I'm over there I'll see if they have any suggestions. Man, their shop has ALL the cool stuff. They can replicate just about any intercooler you ever could want! Oven for brazing the tube sheets, machine to make the fins between the tubes.... I salivate heavily whenever I'm in there!!! Oh, and the humanities! PALLETS of racing turbos (titanium cases, non-containment style scrolls!) All scrap.... Trash... Oh it hurts sometimes. I have learned not to open boxes on the 'scrap dock' for fear of being traumatized for the rest of the day. Same rule applies at Hewlett-Packard in Boise ID, as well... Quote Link to comment Share on other sites More sharing options...
frank280zx Posted April 17, 2007 Share Posted April 17, 2007 Im actually in process with my set up the Supercharger is on the engine and im routing my plumbing at this point ... ill let you know what the outcome will be im feeding my turbo (t3/4) through an m90 .. ooh well it will run somewhere in 2007 Quote Link to comment Share on other sites More sharing options...
Vindicare Posted April 17, 2007 Share Posted April 17, 2007 sorry to point this out, but you are going to need a massive turbo to undertake this, im not sure if you've seen this thread from a australian car club, but a guy who's twincharged a rb25 is running a GT40 with 0.82 turbine wheel or something like that. Im not sure a t3/t4 hybrid could push the amount of air required for the supercharger to compress, making the turbo a bottle neck in the system. However i could be wrong and it is best to read the following link, this guy has completed this on a very reasonable budget and did all the work for it in his garage, except the tuning which was done by a local workshop. http://www.calaisturbo.com.au/showthread.php?t=79101 http://www.calaisturbo.com.au/showthread.php?t=90589 Excuse some of the bable in the threads, most aussie sites arn't quite as informative as hybridz.org, and the particular car the site is dedicated to has a cult following of absolute dropkicks, there are very few who actually know and understand what they are talking about, and im not always far from that description. Afterall i did own one before the zed I hope this help atleast a little. Oh, and if you notice he has taken away the need for 2 intercoolers and run the turbo's outlet straight back into the superchargers inlet then it continues to the intercooler. If you search user's on that forum, warpspeed is another person who has previously taken on a twin charging project on a car where space is at a premium. They are both quite knowledgable, and are very friendly, and if they cant enplain it, they'll know where you can get the information you require. And hows that video from his test run on youtube sounds awesome. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted April 17, 2007 Share Posted April 17, 2007 They are using one on the Golf and Touran(van/MPV) in Euroland - it's a 1.4L TSI. It has 14% more power but uses 5% less fuel than the 2.0L FSI (N/A). Looks like they've used it in the Golf since '05. Also, note the 10:1 CR. (All my 'facts' come from wikipedia .I've read it produces 177 ftlbs of torque from 1750-4500RPM. No turbo lag indeed. I think the Volkswagen one has the tubo and blower running side by side with a flapper valve directing air into the engine from either the blower or the turbo depending upon which one is making more boost. Popular science had an article on it. Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 17, 2007 Author Share Posted April 17, 2007 I think the Volkswagen one has the tubo and blower running side by side with a flapper valve directing air into the engine from either the blower or the turbo depending upon which one is making more boost. Popular science had an article on it. Yea, that sounds right, since their SC has a clutch to disengage it, so I guess they are twin charging, just not compound charging. Vindicare - A bigger turbo will happen eventually, right now I have a stock hot side with a Grand National compressor, which I think is close to some common T3/T4 setups. I don't care much about high end, mainly 2000-5000RPM, so if power starts trailing off around 5grand because the turbo is bottlenecking, I'm OK with that for now. We'll see. Frank - what kind of IC are you gonna run, and how are you going to run the tubing? (turbo>SC>IC>motor?) I would love to see some pics and will try to post some of mine when I start mocking it up. UPS should have it here Thursday, then I can see if and how much I'll need to modify the intake manifold. I'm getting more and more excited about this project. Quote Link to comment Share on other sites More sharing options...
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