Guest JAMIE T Posted March 17, 2002 Share Posted March 17, 2002 I think blow through turbo systems look great! But, from what I have read, SU's aren't the prefered carb for that set-up. You would probably get better performance from Mikunis or Webers. I believe they are easier to tune in that configuration. If you do get the SU's tuned up right for a blow through system, please post details about it. I think plenty of people would like to know about it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 18, 2002 Share Posted March 18, 2002 I guess if you've read the archives you know the downside to blow-thru applications. As far as using SU's, I won't say its not possible because I don't know SU's very well at all, but I believe they'll have a problem with boost trying to get stuffed down they're throat. As I recall, someone mentioned it would not lift the slides properly under boost conditions, but that is a recollection. I think they need vacuum though to lift the slides, a boost condition would tend to hold them shut I'd reason. A pair of downdrafts might be easier to modify for blow-through than the SU's. You will probably also need a boost switch to fire a extra injector (a cold start injector works for this, not sure out of what, I saw it on this page: http://www.geocities.com/MotorCity/Downs/8668/index.htm ) so it won't go lean when it gets to boosting, thats the key thing, keep it fat and retard the timing if possible under boost or limit its total advance and it'll be happy, if it gets lean, well lets just say boom. It'll require carb mods, like a solid float so it doesn't get crushed and some throttle shaft mods, or put the whole carb in a box and boost into the box thats the best way although you still want to change the floats. Good luck with it, Lone Ps: Corky Bell's book Maximum Boost has a chapter on blow through as well thats worth reading. Quote Link to comment Share on other sites More sharing options...
kalium99 Posted March 18, 2002 Author Share Posted March 18, 2002 MY word that car is a piece of crap!! I guess it all comes down to weather or not the particular carbie can handle the pressure needed to keep the right A/F ratio. He had a holly 600 and was using an injector as well, but he was runing a 10 second twinturbo V8...which would need a ton more fuel than an L28. I guess I will have to have a closer look at the 2" Su's and do a bit more research on them. Thats actually where I got the idea for the blow-through turbo, from Corky Bell's book. That Triple Mikuni Blow through turbo setup looks absolutely dreamy! Cheers Ray Quote Link to comment Share on other sites More sharing options...
kalium99 Posted March 18, 2002 Author Share Posted March 18, 2002 Hi, I have recently become interested in doing a blowthrough setup just for fun. I am eventually putting a 2JZ or RB26 into my Z, but in the mean time I am looking for a project and was thinking of trying a blowthru setup with twin 2" SU's. I have been through the archives, and one thing which ppl complain about is trying to tune the setup, but I didnt read that anybody was using a fuel pressure regulator that varies as a function of boost. Would this not somehow alleviate the problem if you could always have a constant relative fuel pressure to the intake pressure ? I can get a newly rebuilt T3 with external wastegate for $150USD, and I have a set of twin 2" SU's lying around. I figure that the project would not be TOO expensive. Probably just the turbo, intercooler, piping, mods to the exhaust manifold, ignition retarder, fuel pressure regulator, pumps etc etc, and time to mod and tune the SU carbies... I am not looking for an awesome power beast, otherwise I would be going EFI. What do you guys think? Cheers Ray Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted March 18, 2002 Share Posted March 18, 2002 In the days before fuel injection su's were use heaps in draw through set ups. They seemed to be the Easyest solution at the time. Might be a little less fabrication as well. Douglas Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 18, 2002 Share Posted March 18, 2002 In the days before fuel injection su's were use heaps in draw through set ups. They seemed to be the Easyest solution at the time. Might be a little less fabrication as well. Douglas IMO, the big drawback with the drawthrough is the inability to intercool. Some folks use water or alcohol injection to cool the charge, but will not remove the heat - you just reduce the temperature by adding less energetic fuel (water can't burn!). Intercooling is a huge advantage as the heat is actually removed from the intake air. Quote Link to comment Share on other sites More sharing options...
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