chino Posted September 16, 2005 Share Posted September 16, 2005 hi i have a 240z with a 280z engine thats running the mikuni triple carbs. my car is running rich as hell, how do i know u can smell tons of gasoline coming from the exhaust and im spending 100bux a week a tank. anybody know where the air/fuel ratio screw is? Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted September 16, 2005 Share Posted September 16, 2005 get a book on the carbs.its probably from a float level thats too high.those things arent the hot set up for a street car.to make them work they need to be jetted on a dyno or install a wideband o2 system and learn about jetting carbs.those carbs have many adjustments.stock su's with some mods work better for street. Quote Link to comment Share on other sites More sharing options...
chino Posted September 16, 2005 Author Share Posted September 16, 2005 thanks for the info but i didnt put those carbs on they came with the car. car isnt really a street car either, came with a whole lot of goodies. i agree it needs to go on the dyno for a tune. where do u get these books? Quote Link to comment Share on other sites More sharing options...
Collectindust240Z Posted September 16, 2005 Share Posted September 16, 2005 I'm sorry that I have to say this, but I don't know why people are so quick to say that tripples are no good on the street. I ran tripple Dellortos for years with no trouble at all. I live in Connecticut and drove the thing year round ( even in the snow) and the thing ran great. You definately have to learn how to jet them and tune them, but once you get them right, they're right. If you don't want to take the effort it takes to tune tripples properly, I would agree that you'd be better off with SU carbs, they're pretty much idiot proof. The tripples are kinda finicky and are very sensitive to float level and fuel pressure. I'd buy a book, which should at least give you some tuning guidelines, buy some jets, emulsion tubes, and take the time to tune them, and you should be very happy with the results. Quote Link to comment Share on other sites More sharing options...
Collectindust240Z Posted September 16, 2005 Share Posted September 16, 2005 Amazon.com should have the book on Mikunis Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 16, 2005 Share Posted September 16, 2005 I drove my 240 with cam, triples, and light flywheel to work every day for 4 years in stop and go. As for books, How to Modify Your Nissan/Datsun OHC Engine has a pretty good writeup on Mikunis. Quote Link to comment Share on other sites More sharing options...
chino Posted September 16, 2005 Author Share Posted September 16, 2005 thanks guys! Quote Link to comment Share on other sites More sharing options...
srgunz Posted September 16, 2005 Share Posted September 16, 2005 Chino I run the same set up as yours on the street. (240 with L28 motor) The first thing you need is to get that fuel pressure down to 3 psi. Nothing you will do will make any difference until that is done with mikunis. I have $600 worth of jets just to get mine set to were I want them. Even then you will get terrible mileage as I do. Mine is a weekend car only. I would never use it as a daily driver with gas prices now. These cars are way too old for daily drivers anyway. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 16, 2005 Share Posted September 16, 2005 It is true that Mikunis aren't as street friendly as SU's, but if you get terrible mileage or terrible driveability the answer is probably the driver or the tuner of the carbs. My 44s on an L28 with a cam got mid 20's highway, which is equal to most SU carbed Zs. In town was worse, but that's more because I couldn't keep my foot out of it. I'd suggest a narrowband O2, as they cost $30 or so, then hook that to a voltmeter. That will tell you what the air/fuel ratios are and you can get them reasonably close that way. Quote Link to comment Share on other sites More sharing options...
chino Posted September 16, 2005 Author Share Posted September 16, 2005 thanks more info. about the jets, i did get a big zip lock bag full of them. how do i know which ones the 3psi are? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 16, 2005 Share Posted September 16, 2005 Dude you need to read about these carbs before you start playing with jetting. There is no 3 psi jet. The fuel pressure will come from a fuel pressure regulator. Read before you adjust ANYTHING. If you did adjust the idle circuits (the screws with the springs on them) the turn them all the way back down and open them back up 1.5 turns. Then leave everything alone until you learn more about them. Otherwise you're just going to screw **** up. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted September 16, 2005 Share Posted September 16, 2005 This information is on DCOE webers but has a lot of good information. http://www.teglerizer.com/dcoe/dcoeinfopages.htm Quote Link to comment Share on other sites More sharing options...
chino Posted September 16, 2005 Author Share Posted September 16, 2005 o sorry didnt read that right. then i cant bring the psi down becuz i have an electric fuel pump on my car. awsome site for info thanks Quote Link to comment Share on other sites More sharing options...
olie05 Posted September 16, 2005 Share Posted September 16, 2005 o sorry didnt read that right. then i cant bring the psi down becuz i have an electric fuel pump on my car. awsome site for info thanks you adjust the fuel pressure with an adjustable FPR - Fuel Pressure Regulator. Look in the victoria british and Motorsport auto catalogs for these. You may even have one if you say your car came with alot of "goodies". I suggest you do some reading on these carbs, and do a few searches on this site for what you're asking. Almost anything you can think of for Z's has been discussed before. -Oliver Quote Link to comment Share on other sites More sharing options...
chino Posted September 17, 2005 Author Share Posted September 17, 2005 the car does have one but its not connected to anything anymore. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted September 17, 2005 Share Posted September 17, 2005 Chino if you wanted sorted out bring it over to Vic and leave it with me for a week and I'll dyno tune the whole kaboodle for you. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted September 17, 2005 Share Posted September 17, 2005 Chino(is vancity = Vancouver?), there are only 3 things you can do right now : 1. buy a book recommended, like "How to Modify..." book jmortensen mentioned which is a better idea because it gives you a range of settings that is suitable for the L-series engine. In my opinion, the How to Modify Your Datsun.... book is not enough because it only tells how to set up the carb but not how to diagnose/rebuild/fix it. 2. Pay a chunk of money to have someone tune it for you because Weber/Dellorto/Mikuni sidedrafts are the most complicated carburetor system, EVER. It is impossible to solve a problem on these carbs by talking to someone over the internet, especially when you don't know enough about these carbs or when you don't have a reference book to look at. 3. Switch to SU or EFI, sell the carb setup for a good chunk of change. I am going to do a swap from EFI to triple carbs soon. I bought my Weber books before I bought a set of Weber carbs. Now I almost finished reading the book but the carbs are not even delivered yet. If your car is running rich like hell ALL THE TIME then this could be happening -The fuel pressure is too high. Again you need 3~3.5 psi -The float setting is too high -The choke is on (I don't know if there's a choke on your carb, ppl may or may not install it) -The jettings are rich also check accelerator pump, this setting can waste a lot of gas if not setup properly. To repeat myself again : These carbs are the most prestigious but also the most complicated. You need to study a book or two. Don't be afraid of carbs, the float system of a carb actually works like the water refill system of a toilet. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 17, 2005 Share Posted September 17, 2005 2. Pay a chunk of money to have someone tune it for you because Weber/Dellorto/Mikuni sidedrafts are the most complicated carburetor system, EVER. Mikunis only have 4 jets to change, pilot, main air, main fuel, and pump nozzles. That's it. They are MUCH simpler than Webers, but you can tune a little bit finer with the Webers. About the only other things going on with the Mikunis is synching them and possibly changing the lever for the acc pump. You can change the jet blocks, but everyone says the OA blocks that most Mikunis come with are the best anyway. If you know when you're rich or lean, you can figure out which jets are going to affect that part of the rpm range and you can then adjust the jets and fix it. I struggled for a while until I got an O2 sensor installed, from there it was pretty easy to get them reasonably well dialed in. It is impossible to diagnose problems over the internet though, especially with someone who knows nothing about these carbs. Quote Link to comment Share on other sites More sharing options...
TheNeedForZ Posted September 17, 2005 Share Posted September 17, 2005 Thanks Jon I didn't know that. Does that mean Mikunis don't have idle jets or pump jets? Does mikunis only have one type of emulsion tube as well? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 17, 2005 Share Posted September 17, 2005 Pilot jet is the idle jet, pump nozzles are the pump jets. Jet block is the emulsion tube and everyone you ask will tell you to use the OA block which is what 99% of them have already. Quote Link to comment Share on other sites More sharing options...
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