racerx260 Posted July 1, 2005 Share Posted July 1, 2005 This is my first post so cut me some slack.I just put in an 83 turbo w/ computer into my 260z,thanks for all the helpful info. Its totally stock and am fine tuneing it before I try any mods.I have never driven another turbo so I have questions about what the power should be like to tell if it is normal or not.So here it goes. The boost starts to build about 2300 rpm . I have 7 lbs of boost at 2700rpm.It accelerates strong but seems to flatten out between 4000-5000 rpm and then accelerates strongly up to redline.Is this flat spot between 4000 and 5000 normal? I have replaced the o2 sensor, have a 2 1/2 exhaust into a magniflow,and have checked all sensor connections.I have run sea foam in the oil and gas to clean up the injectors , valves and a ticking lifter, yes its a p90a head.A second concern is when in 5th at about 3000rm on the highway and I floor it the boost jumps to 7 lbs but the car just sits there and acts too rich.If i roll it on it does ok.Its like a two stoke dirt bike below the power band.IF this is normal great I'll move on, if not I'm open to suggestions.thanks, now woow me with your wisdom. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted July 2, 2005 Share Posted July 2, 2005 well the power seems to be good.. the turbo should give ya full power to nearly 5,200RPM which is usually the peak RPM in 280ZX's... have you checked the spark plugs to make sure your engine is running ok and not too rich?! any feeling of a mis-fire? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted July 2, 2005 Share Posted July 2, 2005 Ohh yeh.. Welcome to the boards!! Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted July 2, 2005 Share Posted July 2, 2005 Spray both sides of the AFM and ECU connector and pins with electrical cleaner and then smear dielectric grease (non conductive) into the connectors and re-assemble. Rich spots and flat spots may very well be due to marginal connections....even if they look clean. WELCOME!! Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 2, 2005 Share Posted July 2, 2005 I'll second that! Make sure it is all clean and secure. Things vibrating loose and making intermittent contact are a problem also. Next step, MEGASQUIRT! Muahahaha! Call me "the devil" for putting the "temptation" out there! Quote Link to comment Share on other sites More sharing options...
racerx260 Posted July 2, 2005 Author Share Posted July 2, 2005 Thanks For The Info. I Have Used The Contact Cleaner But Not The Dielectric Greese,i'll Do That Next.however; The Comment About The 5200 Rpm Hp Point I've Heard And Read Also But Mine Seems To Take Off At 5000 Rpm And Build All The Way To 6500 Rpm When I Shift .does Any One Have Any Recomendations For Replacement Pigtails For The Injectors. Mine Are In Bad Shape And Do Vibrate Loose At Times.i Have Ziptied The Wires To The Fuel Rail To Keep Them Pressed Onto The Injector Put This Is Just Stopgap Untill I Find A Better Solution. I Know That With Everything Stock I'm Not Really Building Power To 6500 It Just Seems That Way Because Of How Flat The Power Is From 4000 To 5000 Rpm..the Plugs Are Burning Clean. The Motor I Used Had 103,000 On The Speedo.i Have Some Concern With The Valve Seals Thay Are Probably Original And Hard. I Burn A Little Oil But No Smoke At Startup The Usual Clue Of Bad Valve Seals.part Of My Original Post Was; Is The Flat Spot From 4000 To 5000 Normal Or Should The Power Be Totally Liniar?, Building As Rpm Goes Up Or Are Their Fluxuations Like My Flat Spot?i Haven't Seen Any Stock Hp Graphs . Does Anybody Have One? Thanks In Advance For Any Advice. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 3, 2005 Share Posted July 3, 2005 GM 3.8L V-6's have very nice connectors, and fit the Bosch Connectors VERY tightly. I like them a lot, and they have supplanted the Volvo Connectors I have been using for years. The Volvo Connectors have similar back boots, and have the "quick disconnect, press-to-release" wire bail on them, and fit nice and tight, also. They are black liek the stock connectors, and the boot on the back seems to be made of better rubber than the Nissan Pieces. The TPS and AFM connectors are also of similar design, but you may need to move the terminals around in the AFM one... But for injectors, the Grey ones of the Buicks seem to work nicely for me now. At the cost of not looking stock. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 3, 2005 Share Posted July 3, 2005 I strongly third the suggestion of cleaning the electrical connections! Quite a few of us have had gremlins that were due to corrosion on wiring harness connections. I don't know about the 'flat spot' you're talking about, but the feeling of the torque/power falling off from 4000rpm is about right, a stock L28ET will have peak torque at between 3000-4000rpm and will fall off sharply after that. Since torque is what you 'feel' that's what you're feeling. Power picks back up a little at the tail end of the RPM as the fuel curve leans out... stock L28ET EFI likes to run real rich in the midrange and lean out a bit after 4000-5000rpm, hence why you might be feeling power pick back up a bit? this becomes a problem once you up boost to 10psi at which point anything above 5000rpm gets too lean. Quote Link to comment Share on other sites More sharing options...
racerx260 Posted July 3, 2005 Author Share Posted July 3, 2005 Thanks For The Heads Up On The Gm Connecters, Those Are A Lot Easier To Get Here In Nascar Country.i Was Thinking It Might Be A Dip Between The Tourqe Curve Ending And The Hp Curve Climbing But Haven't Seen A Graph.your Mentioning It Is Reassuring.is There A Best Themp To Check Compression? Mine Seems To Vary Alot Depending On The Temp. Extreemly Hot After Running Hard Its Significantly Lower Than After It Has Cooled Down Some.my Motor Was An Unknown Except For Mileage ; 103,000 Mi On Speedo.there Was Still Hone Marks In The Bore When I Peeked In But From The Condition Of The Turbo When It Was Rebuilt It Ingested Alot Of Dirt.hope I Don't Have To Pull This Back Out And Re-ring Or Bore It.that Would Be A Bummer. I'll Do The Oil In Cylinder Compression Check To See If It Is Rings Or Valves. Quote Link to comment Share on other sites More sharing options...
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