DIY_EFI Digest Wednesday, July 28 1999 Volume 04 : Number 437 In this issue: Re: DIY_EFI Digest V4 #436 Re: Trip computer? RE: Some efi: carby/super charger setup See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Wed, 28 Jul 1999 06:45:42 -0400 From: "Charles Brooks" Subject: Re: DIY_EFI Digest V4 #436 Hi Dan, I'm nearly certain that the Float will have to be replaced or modified so id doesn't crush under boost. I'm slowly putting parts together for a twin turbocharged small block Chevy (And I'm selling a complete single turbo system for a SBC to finance the TT project, if anyones interested contact me off list) and one gentleman I ran into showed me a float from a 2bbl Holley that was on his Turbo Ford 2.3, the float looked like someone had stuck a straw in it and sucked REALLY hard :) You do have to reference the regulator off of boost however, if you run more boost than the pump itself can handle... The home grown turbo projects I've seen have been on V8's and used a mechanical pump that was modified to accept a manifold pressure reference. The Holley Mech. pumps are easily disassembled for the mods. I'm not sure if you could use a high pressure EFI pump with a low pressure regulator or not. If you do, make sure the regulator is a 3 port (Or more) design that has a bypass for fuel to return to the tank. That way the fuel flow will cool the EFI pump, if you use a "Deadhead" regulator with no bypass the pump will probably overheat and be damaged. I'll take a look at some of my parts books and see if I can find a regulator that looks like it'll work. How much boost are you thinking of running? Charles Brooks - ---------- Original Message ---------------------------------- From: DIY_EFI-Digest-Owner@xxx.edu (DIY_EFI Digest) Reply-To: diy_efi@xxx.edu Date: Wed, 28 Jul 1999 05:00:01 -0400 - ------------------------------ Date: Wed, 28 Jul 1999 09:33:29 +0800 From: dzorde@xxx.com Subject: Some efi: carby/super charger setup Hi all, With the list in digest mode it seems the mail has really slowed down. Anyway, I'd appreciate if someone has a solution for this minor inconvenience. I have finally managed to get my Fiat 850, with the MR2 supercharger on it, running. Currently its using the original carby in a blow through configuration (the setup is crap, but will have to do for the time being). With the whole carby being pressurised there is enough fuel pressure in the electric pump to make the car idle, however I'm sure as the pressure builds up the fuel pump runs out of steam. What is the solution? Do you use a high pressure efi pump with a 0.5bar regulator, vacuum/boost compensated to the inlet manifold, so the fuel pressure is always 0.5bar above boost level ? What about the float. The carby currently uses a soldered brass float, will it be strong enough to withstand say 20psi of boost ? Or will I need to fill it with something non collapsable ? What about the needle and seat, will there be any problems here ? Might sound logical, but I'm a bit out of my depths here and so appreciate any answers, on list or off list. Dan dzorde@xxx.com ------------------------------ Date: Wed, 28 Jul 1999 09:52:43 -0700 From: "B.Robert" Subject: Re: Trip computer? To Pat and all, This article was in Circuit Cellar #98 (Sept. 98) but I must caution anyone interested in this system: The article from Oztechnics is an "infomercial" ! Contrary to what the article says, the guy refuses to release the microprocessor code (source or object). Instead of honoring the build-it-yourself spirit of the magazine, he wants to sell it to you. I contacted him twice and now Circuit Cellar magazine are on his case (they were fooled by a 2.5 MB ZIP file that he sent them and contained no article code). Tsk, tsk, tsk! Just my $0.02 cents! Benoit R. >Date: Tue, 27 Jul 1999 15:59:39 -0400 (EDT) >From: Pat Ford >Subject: Re: Trip computer? > >a few months ago circuit cellar ink ( a magazine) >had just that kind of beasty try > >http://www.oztechnics.com.au/frame_car.htm > >this beast keeps track of your injector on time ------------------------------ Date: Wed, 28 Jul 1999 11:44:33 -0700 From: "Buchholz, Steven" Subject: RE: Some efi: carby/super charger setup > With the list in digest mode it seems the mail has really slowed down. > Anyway, > I'd appreciate if someone has a solution for this minor inconvenience. I > have > finally managed to get my Fiat 850, with the MR2 supercharger on it, > running. > Currently its using the original carby in a blow through configuration > (the > setup is crap, but will have to do for the time being). With the whole > carby > being pressurised there is enough fuel pressure in the electric pump to > make the > car idle, however I'm sure as the pressure builds up the fuel pump runs > out of > steam. What is the solution? > > Do you use a high pressure efi pump with a 0.5bar regulator, vacuum/boost > compensated to the inlet manifold, so the fuel pressure is always 0.5bar > above > boost level ? > > What about the float. The carby currently uses a soldered brass float, > will it > be strong enough to withstand say 20psi of boost ? Or will I need to fill > it > with something non collapsable ? > > What about the needle and seat, will there be any problems here ? > ... by no means would I consider myself to be an expert on carburetted systems ... but there is one issue that seems quite apparent to me. The float bowl of the carb is running in atmospheric pressure, so as you increase carb inlet pressure above atmospheric it sure seems to me that you're going to start pushing fuel (& even air) back into the bowl. I don't know how you're going to be able to work around this pretty fundamental issue. The carb is trying to meter fuel using Bernoulli's principle, so pressurizing the bowl would probably cause other problems. I wouldn't worry about the float collapsing under pressure, but it might tend to sink a bit lower in the fuel when the bowl is pressurized. You would also need to have a fuel pump that was capable of overcoming the pressure in the bowl as well ... The simplest solution I can come up with would be to replace the carb with some sort of TBI unit ... but I don't have any suggestions as to the best source of such a system for a blown Fiat ... I know Smokey Yunick had a system where he put a turbocharger in front of a carb way back in the early 70s. He may have had a specially made carb though ... I know he had some funny name for it ... what was it ... "homogenizer" ???? You may want to check back through Popular Mechanics ... HTH! Steve Buchholz San Jose, CA (USA) ------------------------------ End of DIY_EFI Digest V4 #437 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".