caen fred Posted April 3, 2009 Share Posted April 3, 2009 I have converted my 240Z SU to FI. Basically they just now are a big throttle body with one GM injector where the piston was. It works OK, I made the mistake of trying new tech on a new engine with lots of unknown parts So the set-up takes a lot of time and trying and guessing but I am getting there! My question for you to debate on (at least 3 pages or I would not feel paid back for the effort I did towards Z science ). If I can get enough fuel by my two injectors will I actually have enough air to match a triple carb set-up????? Picture the carb now as an empty tube with a velocity stack at one end and the std manifold after the plate? I have a pair of Jag SU just in case I would need more air, but I'd rather stick to Datsun looking parts. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 3, 2009 Share Posted April 3, 2009 Yes, with a qualification... What is the drop height of the conversion piece he made that houses the GM TBI Injector? That is, how big of an opening is there remaining compared to a 46mm open tube? I know the 46mm hole will flow (roughly) 740cfm (from memory) and two will have a potential of twice that. Most Triples are choked down to around 6 34mm holes, but have to operate at a higher delta-P due to siphoning fuel from the bowl, so they are usually around the 1100-1300cfm range for flow. Since EFI is measured at a lower restriction, the holes 'flow more' than carburettors. Our 45mm Carbs netted 40 less HP at 750 less RPMs than the 45mm ITBs. To run that kind of power we would have had to go to 55mm Triples (using 45 mm chokes to function!) Depending on which injectors you use from GM's parts supply, there should be FAR more fuel than you will ever need. Two injectors are all that are on my 7.4L tow vehicle, and that is well over 150HP. The 7.4's run an elevated fuel pressure, closer to 30psi than the normal TBI pressure of 20 or so. Show us photos again. I miss seeing the parts on the car. I have to drop him a line and see the progress on the other SU adapters. I sent him 52# worth of every Datsun SU ever produced to get the patterns made and set up for sale. That was a year ago. I think you ended up getting the first set off his production line after I sent in the carbs for samples! More importantly, how does it RUN NOW?!?!?!?!?! Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 3, 2009 Author Share Posted April 3, 2009 We sended both carbs to him the same week I need to time my cam and advance to be sure. The only issues I have is Iddling speed 1000 rpm not under and it need 3 turn of the key to start... other than that it's verry nice. I will take it to a dyno to get some figures. Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 4, 2009 Author Share Posted April 4, 2009 The TBI adaptor is barely protuberant. The real restriction is the venturi where the needle was. Looking at it I think that if I carve it out I will need to sleeve it in some way because I will go past the thickness of this part at this very location. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 6, 2009 Share Posted April 6, 2009 The TBI adaptor is barely protuberant. The real restriction is the venturi where the needle was. Looking at it I think that if I carve it out I will need to sleeve it in some way because I will go past the thickness of this part at this very location. Excellent news, since I already have carbs with that venturi cut out! My friend has a HAAS machining center (er...several actually) and machined them out for me. If you use devcon or other epoxy filler on the body of the carb (or welding it Heliarc/TIG) in the areas of the die-cast where it will cut through to the outside of the body when bored, you can do it in one operation. On my 73's it was in the float bowl only, so I used epoxy as it was easy. Since it's not protruding far, that means I can run my Bosch Injector underneath the carb, and his TBI setup from the dome area, and do a direct comparison to the difference in performance and fueling that is needed with each different injector type and position! I had done a 'bosch underneath' setup on another car, but it wasn't firing in the right direction, and we ended up putting the suction piston in to even get it running off-idle properly. It looks like Rick may have confirmed my hypoithesis that you have to fire at the throttle plate to make this application work. Just for the record, my Chevrolet Truck with the factory TBI setup takes some cranking to fire it off, it's not like port injection where it goes right off first thing in the morning. But it's usually good on restarts. Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 6, 2009 Share Posted April 6, 2009 ah, yes, my evil plan is working. with Tony D and Caen Fred on the case, my troubles will be solved and spelled out for me with the Orange-SU-airbox turned-turbo-plenum comes about....that hot air intake is just in the perfect spot for the hidden charge pipe... Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 7, 2009 Author Share Posted April 7, 2009 I wonder if I should switch to Megasquirt? The GM ECM is fine but cannot be altered on the move on a rolling stand. Is it a direct plug from std GM ECM to Megasquirt? Quote Link to comment Share on other sites More sharing options...
evildky Posted April 7, 2009 Share Posted April 7, 2009 no Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 7, 2009 Author Share Posted April 7, 2009 When it's backed up with so many facts, it can't be beaten Is it a no NO, a no No, a no no... Try to be more specific It's scienZe matter in here! Quote Link to comment Share on other sites More sharing options...
Xnke Posted April 9, 2009 Share Posted April 9, 2009 Yes, swap to MS, No, you can't just plug and play. There is some setup and some re-wiring that you'll need to do, in 99.9999% of cases. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 9, 2009 Share Posted April 9, 2009 The GM setup is very close, but there is wiring changes involved. There is a website out there that detailed a MS install into a Corvette that used the stock GM harness and pretty simple changes. Depending on what GM ECU you have, tuning on the fly is possible, but likely you have something in the late 80's or early 90's with a reburnable prom. You might want to contact Turbo City in Orange CA...they used to do custom burns on GM ECUs to run everything from N/A VW 1600's to Turbocharged what-have-yous! Though MS will drive what you have, and likely will be cheaper to boot! Later (OBD2) compliant GM ECU's have a program called "TunerCat" that has a very nice interface for tuning on the fly. Given the long and short term fuel trim in the newer ECU's, it is a very nice setup. It's my 'dark side' but yeah, I've been helping a buddy with his LT '94 in a 74' Camaro Swap...yeah, I do domestics too. It's not something I'm proud of, kind of like the sheep incident up outside London some years ago... Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 9, 2009 Author Share Posted April 9, 2009 Thanks a lot Tony I will have a look at TunerCat Might be just what I need, I only want the on the move (or on the dyno) tuning ability of MS. Quote Link to comment Share on other sites More sharing options...
Tony D Posted April 9, 2009 Share Posted April 9, 2009 It's only available for OBD2 or never GM ECUs' If it's driving TBI injectors, likely it's OBD1 Tier0 and will not have that capability. Which GM ECU are you using? Something from a Mid 80's/Early 90's 2.8L V6 Pickup Truck like an S10 or S15 should be very close to what you need. Quote Link to comment Share on other sites More sharing options...
caen fred Posted April 9, 2009 Author Share Posted April 9, 2009 I will check... Quote Link to comment Share on other sites More sharing options...
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