madmatt48 Posted October 23, 2009 Share Posted October 23, 2009 The Demon is specifically designed for blow through turbo and supercharger application. I could understand if I had a regular Holley, Carter or other make of carburator that was not intended for blow through application but this carburator is. The Demon installation instructions do not state your above comments that you must select pressure of fuel to be above that of the boost. That is why I picked this specific carburator and use a boost rising fuel pressure regulator. I receive my new fuel pump tomorrow morning and I will run this 155 gph pump with the current 72gph in tandum and that will be 227 gallons per hour of fuel potential running through the Demon 650 cfm carburator. That is a lot of fuel pump capacity with the pressure being just over 9psi. When I had the fuel starvation or pushing problem last weekend, the boost was set way down to only 6 psi. If your above description is correct, I should not have had that problem being my fuel pressure was 9 psi which is 3psi higher than my boost. Thank you for your updated information and ideas. I will know this weekend where I stand with fuel pressure whether or not I will need to order the super hoss of an EFI pump. I would like to see the distributer plate modification Tony-D was talking about which would be a good thing to have to avoid advancement under boost. Every safeguard to prevent blowing an engine is a good thing. Thanks for all the great ideas, hopefully I will have a monster runner yet. Quote Link to comment Share on other sites More sharing options...
24OZ Posted October 23, 2009 Share Posted October 23, 2009 Do you have an Air Fuel Ratio sensor, to help keep an eye on what's going on? Will be a good investment. Quote Link to comment Share on other sites More sharing options...
madmatt48 Posted October 23, 2009 Share Posted October 23, 2009 Have an A/F ratio gage with sensor mounted on the downpipe, Exhaust Gas temp gage with thermocouple sensor tapped just after the turbine flange where 6 meet one and boost gage that reads up to 30psi. I agree with you, a very good investment. Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 23, 2009 Share Posted October 23, 2009 dude your doomed to blow ♥♥♥♥ up. I dont care what carb it is. Boost pushes the fuel back to the tank when the floats are pressurized. Boost prep means the carb can handle positive pressure. so you have lets say 1 psi of fuel and 1 psi of boost well that one psi of pressure is gonna push the fuel back so you need 2 psi of fuel to keep the 1 psi of fuel in the carb. Listen now or reap the benefits of not listing. I am out. I really cant help you anymore and tony is gonna say the same thing. flow matters but even more is psi to keep the flow there. Look here people another blow through thats gonna blow and give it a bad name! Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 23, 2009 Share Posted October 23, 2009 Go turn your garden hose on a little than blow 10psi of air at it if that does not sum it up i dont know what does. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted October 23, 2009 Share Posted October 23, 2009 That's a little harsh, correct, but harsh. It doesn't matter what carb you have, if you don't have the proper pressure air will force the fuel out of the carb. Go to theturboforums.com and read as much as you can in the Carburetor+Boost section, also, do a search for demon carbs in the same section. Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 23, 2009 Share Posted October 23, 2009 Harsh yes but sometimes people need a slap in the head when it comes to blowthrough. I dont have time for people to theorize about what there package or manual tells them. I tell it like it is, not how others think it is. Hey its not my motor wtf do i care. This is why it gets such a bad name. People dont listen to other people who have done it. MANY TIMES! DRIVEN FOR MANY YEARS! if the man does not want to listen to the facts not the " I think's" then its over he will blow his motor and say blow through sucks and does not work. You need efi pump bigger return line to keep pressure in check. Or use vent line via TonyD's idea. You need 1:1 rrfpr tapped at the hat not the mani. At the mani is to late BOOM! Most important you need to listen and take it as the law. Flow is good but means nothing if it cant combat the pressure inside the carb that you are forcing in it. Quote Link to comment Share on other sites More sharing options...
madmatt48 Posted October 25, 2009 Share Posted October 25, 2009 Thank you for your replies. I had not planned on installing a tap on the carb hat or the larger return line, now that you mention it, I like the ideas. I will stop experimenting for now, get the EFI fuel pump and the other growing list of goodies you both mentioned and not fire it up again until I have it all installed. After all, the race track I go to is closed until next spring so what's the rush? Getting the Z running again after so much time sitting in the garage had me on a rampage to drive. Well I will exercise more patience (hard to do) get all the noted mods and hopefully have it ready to roll by next April/May when Top Gun raceway opens again. By the way, do you have a better description of the distributer plate modification that you and Tony were talking about and the best way to route the carb hat tap? Quote Link to comment Share on other sites More sharing options...
280zex Posted October 26, 2009 Share Posted October 26, 2009 My Holley/T3T4oe blowthrough works fine!!. Get a Mallory unilite dizzy and lock out the advance curve. go to theturboforums.com check out the carb + boost section. Look for blowthrough 280z as a topic. It can be done. it DOES work well. Gota get the right parts. Aeromotive makes a boost regulated fpr. 1 to 1 rize with boost!! get one and use it..I'll post pix after work.. Quote Link to comment Share on other sites More sharing options...
280zex Posted October 26, 2009 Share Posted October 26, 2009 here's how the blowthrough looks now. I added the stock injection cooling fan and adjustable controller to help after-run heat soak (fuel boiling off). So far so good. T3/T4oe .63 trim @ 8lbs boost blown through a Holley 390cfm double pumper. I got a free spin on a local tuner shops dyno. 250rwhp before the clutch started slipping... Quote Link to comment Share on other sites More sharing options...
280zex Posted October 26, 2009 Share Posted October 26, 2009 Tony I just read your timing set info.. Seems we bolth agreed on the setting. 18 degrees, no advance(lock down), pump 92 octane. And yes I did just go and check it with the light again How did you calc. fuel consumption/milage at wot? I assume some top speed R&D.. Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 26, 2009 Share Posted October 26, 2009 how is that ebay turbo holding up Quote Link to comment Share on other sites More sharing options...
280zex Posted October 27, 2009 Share Posted October 27, 2009 for now everything is working very well. about 17.5 mpg. I don't think the clutch has a long life at this point though. I'm in love with the sounds of boost. Quote Link to comment Share on other sites More sharing options...
280zex Posted October 27, 2009 Share Posted October 27, 2009 For those who wana know -- the turbo came from CXRacing in california probibly via china...it works well too. Use syn-oil! Quote Link to comment Share on other sites More sharing options...
280zex Posted October 27, 2009 Share Posted October 27, 2009 and yes the head is pollished:-) Quote Link to comment Share on other sites More sharing options...
madmatt48 Posted October 27, 2009 Share Posted October 27, 2009 Now that is a nice clean solid blow through set up. I used a centerforce II clutch on my prior 1970 240z with triple weber 45 setup and worked great not too much grip to where you blow transmissions when running sticky tires but enough to hold around 300hp reliably. What EFI fuel pump are you running for your reliable set up? Quote Link to comment Share on other sites More sharing options...
280zex Posted October 27, 2009 Share Posted October 27, 2009 stock efi pump. original to the car 8/1976 Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 27, 2009 Share Posted October 27, 2009 18btdc is the magic number for one it offers great start up two decent off boost response and three is more than enough until the 15psi range then it needs to start going back again. If you are building a car like this mpg is not a issue if it is go efi or drive a Honda civic This is power is its rawest most primitive form. ITs good it gives character but not ease of or best approach. I do them all the time Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 27, 2009 Share Posted October 27, 2009 Mileage for 17 mpg in commuter service was from about 26,000 miles in one year filling up the tank while driving to and from work in Brea, while living in Corona and tracking it as usual. Track numbers were taken after filling up trackside, running laps, measuring miles driven, then refilling and going "Oh, I guess the gas gauge gremlin is NOT rearing it's head and I CAN suck down 12 gallons in less than 70 miles!" (around 58 miles, in fact...) Depending on the temperature outside, I would have to be light-footed at 17psi, so what yerbetten says about 15psi is probably true. I don't run the best gas, either. At 12psi I was running Arco 87 octane at that advance level! Quote Link to comment Share on other sites More sharing options...
yetterben Posted October 29, 2009 Share Posted October 29, 2009 0_0 Quote Link to comment Share on other sites More sharing options...
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