Chewievette Posted October 12, 2006 Share Posted October 12, 2006 I've been wanting to turbocharge my 240 since I bought it and since it doesn't look like I'll be driving it this year *Looks out the window at snow falling* I might as well tear it down and start the restomodding. I want to keep the twin SUs because I like the way they look and I dont really care for the stock fuel injection setups. What I want to do is run a megasquirt with either one or two injectors in each carb. but since I like messing with people I want to make it hidden. The injectors will go in the suction chambers on top of the carbs using a custom made piston. My question here is do I need to retain the piston movement for the venturi effect or is it okay to replace it with a fixed piston? I wouldnt think you need it but I want to double check. Also what functions of the carb do I need to keep, eliminate, or restrict? From what I know about efi I would think that I need to keep the throttle plate and linkage and eliminate the rest, basically turn it into a big throttle body. I think that with some creative thinking I can hide most all of the efi sensors and wiring. I have a few ideas for the temp sensors and fuel injectors but the throttle position sensor is giving me problems. But I think I might have an idea for that too. If you guys have any ideas for me I'd love to hear them, I'd really like some help with this. Also if someone could help me with setting up a megasquirt for this type of setup (near constant flow) I'd really like to have a chat with you. I have a couple more things to ask about but I'm going to pickup my new used lathe right now, very excited! Quote Link to comment Share on other sites More sharing options...
veritech-z Posted October 12, 2006 Share Posted October 12, 2006 funny how prevalent this idea is...Me and OTM and Olie05 were kicking this around via PM awhile ago. So far as I know, none of us got anywhere with it. My idea was to get a low profile, high output injector, maybe a gm V-8 tbi injector for each carb, and hide it in the air cleaner. www.twminduction.com sells a rail for their carb conversions that has floating injectors that are mounted in front of the carb throat, so I was looking at that concept. Hiding it in the air box, it would be just as injected as if you hid it in the carb, but without all the hassle of plumbing the lines and wires through that confined space (I also think this would give you a more even distribution of fuel, since mounting it in the hat would spray directly on the bottom of the throttle bore). It also enhances the ratty stock looking underhood appearance. We thought this conversion would be great with flat top SUs, since their non-performance reputation is so well known. All you would need to retain of the original carb should be the throttle body action, so remove the pistons and block off the holes. Quote Link to comment Share on other sites More sharing options...
GrayZee Posted October 13, 2006 Share Posted October 13, 2006 I know you can get TBi injection systems that look like sidedraft webbers. Don't know where or how much, but I have seen one before. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 13, 2006 Author Share Posted October 13, 2006 Webers dont have the look I'm going for and a minimum of $1000 for a functional carb set and $3000+ for tbi (made by TWM) they are totally out of my price range. I acctually have a set of flat tops that I want to use for this, what can I say they were cheap. I want to put the injectors in the carbs so that I can use the stock fuel inlet point and then a drill new passage up to the suction chamber. I want to make a new stationary piston(with my new lathe) to mount the injectors. I am 99% sure I cant mount all the efi parts within or obscured by the stock components. The main reason that I want to convert to efi is so I can turbo it without the hassles of blowthrough. That and the WTF factor. With the throttle position sensor, I think I can mount it on the back side of the firewall behind the linear to rotary part of the linkage, slightly modified of course. I think that I can make this work but I'm not sure if it will function properly, any thoughts? The air temp sensor could be mounted on the back end of the balance tube but it would be fairly visable. My other thought would be to mount it on the back of or inside the air cleaner box. But since I want to turbo, the air cleaner would be somewhere else so I might as well mount it to the manifold somewhere. Maybe in the carb next to the injectors or something. The coolant temp sensor could be mounted inside the fuel bowl reading the coolant in the carb, or in the bottom of the manifold, or I could mount it somewhere else entirely, any thoughts? I was thinking about snagging the exhaust manifold off of my 280zx and using it with the stock o2 sensor since that obviously looks very stock. I'm looking at a wiring diagram for the megasquirt and I'm confused by the fast idle solenoid. I'll do some reading but if you got a sec to explain it I'd appreciate. Will the existing fast idle linkage work for this? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted October 13, 2006 Share Posted October 13, 2006 I know you can get TBi injection systems that look like sidedraft webbers. Don't know where or how much, but I have seen one before. If you go to the link I posted earlier, they have the weber conversions (they aren't the only one, but they are the only one that I know off the top of my head ) and SU conversion throttle bodies as well, but they are super pricey. Chewie, if you are going for the sleeper look, how exactly are you planning to run your fuel lines so that they don't look obvious? I really don't think you'll have room to angle your injector down the throat of the carb AND run fuel to it if you hid it under the hats. Also, I think the turbo will pretty much give it away that you don't have a stock vehicle. Nitrous is so much more conducive to sneaky HP than a turbo. Something to think about is this: If you mount the injector underneath the carb and remove the piston and needle seat, you would have plenty of space, and you are going to need a plenum for boost, which will hide the injector itself. That means that you could just run your fuel hose through the float bowls and out the bottom to feed your injectors, but the carbs will look stock from the top. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 13, 2006 Author Share Posted October 13, 2006 The plan for fuel is to run it up into the engine bay, through the gutted mechanical fuel pump, through the stock fuel rail then into the carbs in the stock location. Then drill passages in the carbs to get the fuel where I need it. I'm going to have to run an electric fuel pump and regulator under the car somewhere. The whole point of this sleeper is Not to look stock but so that its difficult to know where my performance level is. A big shiny TWM triple dual TB setup with HKS style plenum, big honkin intercooler, and a T4 turbo on a tubular manifold, just wouldnt mesh with what I like, or what my budget is. Now a pair of flat tops, T3, cast iron manifold, and small-ish intercooler that all look like fresh junkyard pickings are more to my liking. I think that there is more room inside the domes than there is in the bowls, although you are right in that I can lay the injector down on the bottom of the carb without it being seen even though it wouldn't be entirely internal. I'll see what I can come up with. ADD - I just went out and did some measuring and calculating. By putting the injector in the dome I can lean it over to an approximately 40* angle with room to spare. Nowhere near the ideal but better than 90*. But then you have to remember that the carbs sit level and the engine is not vertical so the intake manifold is at a downward slope to the head. This theoretically puts the injector at about a 20* angle, much closer to the optimal angle, which is 15* if memory serves. Now I do realize that the critical angle here is the injector to the adjacent airflow but having the injector mounted on top would give more of a straight shot into the cylinder where mounting on the bottom would be a curvier path. btw, there is enough room in the dome for two injectors. Would there be any advantage to using two injectors per carb, totalling four? Quote Link to comment Share on other sites More sharing options...
veritech-z Posted October 13, 2006 Share Posted October 13, 2006 posted by chewievette: Would there be any advantage to using two injectors per carb, totalling four? Offhand, I would say no, not if you size your single injector properly, unless cost is a factor, and it would be cheaper to use two smaller flowing injectors rather than one large flow injector. In your measuring, did you account for fuel hoses and electrical connections, or just physically squeezing in an injector? What injector did you use as a baseline? I still think hiding your injectors in the plenum is ideal, from a practical AND from a functional standpoint. You can have a straight shot down the throat of the carb, nobody will see it, and there is plenty of space. You are going to need a plenum anyway, there is no hiding that, so you might as well make full use of it. This would work pretty well with a side feed injector like on an SR20 motor. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 13, 2006 Author Share Posted October 13, 2006 I allowed for plenty of room for the fuel hose and electrical, that's why I said with room to spare. I could lean it over more with a side feed but I'd rather have the flexability of top feed. I just used a standard bosch injector that I had rolling around in one of my parts boxes. My only problem with putting the injectors in the plenum is that I want to create a tubular plenum to keep the size down. If it had injectors inside it would have to be larger to flow the same amount of air. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 14, 2006 Administrators Share Posted October 14, 2006 Chewievette, Interesting idea. I think the difference between a 90 deg. inj and one that is 'optimum' is going to be negligible in most cases. You'd be most likely to notice it at idle and very light loads, when airflow is low. Mount them at whatever angle you can in the upper chambers and you should be fine. 4 injectors (instead of two) coupled with MS might have an idle quality advanatage as well. MS's resolution is not that great (0.1 millisec) and this could become critical with two large injectors. However, I did hear rumor of a new code release that improves MS's resolution... I haven't looked into that yet. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 14, 2006 Administrators Share Posted October 14, 2006 My question here is do I need to retain the piston movement for the venturi effect or is it okay to replace it with a fixed piston? I wouldnt think you need it but I want to double check. Also what functions of the carb do I need to keep, eliminate, or restrict? From what I know about efi I would think that I need to keep the throttle plate and linkage and eliminate the rest, basically turn it into a big throttle body. All you need is the butterfly... 'delete' everything else. Quote Link to comment Share on other sites More sharing options...
BlackBeaut Posted October 14, 2006 Share Posted October 14, 2006 Are there any issues with just one (or maybe two) injectors feeding 3 cylinders? It would have to fire 3 times as often as the usual six injector set ups which seems to me like it would be a tough job at higher revs. I'm guessing you're not fitting Formula 1 spec injectors Cheers, Rob Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 14, 2006 Administrators Share Posted October 14, 2006 Are there any issues with just one (or maybe two) injectors feeding 3 cylinders? It would have to fire 3 times as often as the usual six injector set ups which seems to me like it would be a tough job at higher revs. I'm guessing you're not fitting Formula 1 spec injectors Rob, I would see it as the injectors needing to be 3 times larger... opening for the same duration. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 15, 2006 Author Share Posted October 15, 2006 That's why I asked about multi injectors. If I could run them as constant flow then I wouldnt have a problem, it would act almost exactly like a carb only I'd be tuning the electronic control rather than mechanical ones. If I did put the injector at a 90* angle then I could run six injectors of approximately stock size. However I dont know if the improved idle quality will make up for the non-optimal angling. If anyone has a spare flat top carb that they might be willing to let go for cheap, I could use a test subject before I modify my "good set" PM me, thanks. btw, I just did some measuring and with the right size injectors six injectors would fit in EACH carb(at 90* to the airflow)! However three is much better for packaging reasons. Thought you might want to know. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 15, 2006 Administrators Share Posted October 15, 2006 That's why I asked about multi injectors. If I could run them as constant flow then I wouldnt have a problem, it would act almost exactly like a carb only I'd be tuning the electronic control rather than mechanical ones. If I did put the injector at a 90* angle then I could run six injectors of approximately stock size. However I dont know if the improved idle quality will make up for the non-optimal angling. I think you're barking up the wrong tree... constant flow means having an injector open at all times while modulating fuel pressure. None of the current aftermarket EFI systems that I'm aware of are intended to be used this way... and its about 10 steps backward in complexity and control, in my opinion. A pair of fair sized TB injectors should do the job well with a stand-alone EFI system. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 15, 2006 Author Share Posted October 15, 2006 I only mentioned constant flow because its just simple enough to fix the problem. I dont really intend on using that system. I think either two or three injectors per carb will work just fine. When I want to max out performance I'll go to six injectors at the cyl head like the stock efi. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted October 29, 2006 Share Posted October 29, 2006 good luck with this setup. I'm probably going to be going with SR power sometime but I still will build an L2xET sometime and try to sell it one piece and get rid of all of my cool L6 stuff like this nice 11Lb. flywheel and clutch that have 700 miles on them... Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 29, 2006 Author Share Posted October 29, 2006 I've been tinkering away at this project. I've just about got the new piston drawings done so I can start machining them. I hope by spring this will be up and running. I wanted to get it running on carbs for the drive to my house (its in storage right now) but that's just not going to happen, so trailer it is. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 29, 2006 Administrators Share Posted October 29, 2006 ....... The air temp sensor could be mounted on the back end of the balance tube but it would be fairly visable. My other thought would be to mount it on the back of or inside the air cleaner box. But since I want to turbo, the air cleaner would be somewhere else so I might as well mount it to the manifold somewhere. Maybe in the carb next to the injectors or something. The coolant temp sensor could be mounted inside the fuel bowl reading the coolant in the carb, or in the bottom of the manifold, or I could mount it somewhere else entirely, any thoughts? ........ Dave, The Air Temp sensor needs to at least be mounted in la ocation that gets "flowing" air across it. The balance tube doesn’t really see “flowing” air, but pulsations back and forth, if that makes any since. Here is thread about the inlet Air temp sensor mounting positions. http://forums.hybridz.org/showthread.php?t=115937 The water temp sensor could easily be threaded into any portion of the cylinder head such as the rear if stealth is your concern. When drilling and tapping the head, just be sure you aren't anywhere near the oil galley or into and combustion chamber etc. Interesting project by the way. Quote Link to comment Share on other sites More sharing options...
Chewievette Posted October 29, 2006 Author Share Posted October 29, 2006 That was a good read, I'll have to keep tabs on that. From the jist I'm getting is that I need to put the IAT right before the fuel injection point which is acctually really easy for me so I'll probably put it there. The only other issue I have is that the fuel is injected before the throttle plate so basically before the TB like was being said. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted October 29, 2006 Administrators Share Posted October 29, 2006 From the jist I'm getting is that I need to put the IAT right before the fuel injection point which is acctually really easy for me so I'll probably put it there. I think you're in an unusual position to do what I described. There is one flaw that I see though... If its too close to the injector, you could easily get fuel on the IAT sensor due to reversion. Not good. Quote Link to comment Share on other sites More sharing options...
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