cygnusx1 Posted August 28, 2003 Share Posted August 28, 2003 Well I drove the Turbo Z I just finished building. Runs great and pulls hard. I actually put it in a car show tonight. However, in spirited driving, I notice that the rev's don't drop fast enough to match the next gear speed during upshifts. It is hard to describe. Basically, the engine RPM drops very slowly between shifts. Is this a normal characteristic of a turbo motor or is it because the EFI was from an automatic ZXT. Is there anything that will make the RPM come down quicker in between shifts?--other than bumping the drivetrain with the clutch like I do now. It forces me to wait between gears in order to upshift smoothly. 76Z with complete 83 factory turbo engine and EFI with all emission ctrls stuff in place x-cept the cat. It has a 2.5" S.S. exhaust with a Magnaflow. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 28, 2003 Share Posted August 28, 2003 I asked about this same problem a month ago, and didn't get any answers. The RPMS always want to hover between shifts, and I have to wait a second for them to come back down... makes driving on the street a pain sometimes, hard to get a nice smooth (soft) shift, it's always slamming into the gear. The donor car came with the nissan 5-spd, but I dont think it was stock that way, was probably an auto also... now I'm wondering too if this has anything to do with it? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 28, 2003 Share Posted August 28, 2003 How about a light flywheel? Stock turbo flywheel is what 25 lbs??? You can have a stock one turned down to ~15, but that always seemed like a lot for a cast iron flywheel. Don't know if there is an aftermarket available for turbo. Check with the guy on Ebay who sells Fidanza. He could tell you if they are available. Centerforce aluminum flywheels are not that light if I recall correctly... Jon Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 28, 2003 Share Posted August 28, 2003 I have a lightened stock flywheel, 16lbs about. I was told that a light flywheel will actually drop revs faster...? Less mass in motion, so it loses energy quicker, more mass tends to want to keep moving, isn't that right? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 28, 2003 Share Posted August 28, 2003 Do you still have the vacume assist attached to the throttle linkage? If you kept the stock linkage offthe auto car and hooked everything back up like on the auto car, there is a part that has a vacume line going to it that hold the RMPS up for the auto trans to shift smoothly. Just remove it and plug the vacume line. Hope that helps. Mark Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 28, 2003 Share Posted August 28, 2003 Mark's suggestion sounds good. The RPMs not dropping is NOT normal. I had that problem once on my stock '78 engine, but never on a turbo conversion, either with the '82 EFI or the '86 I have now. Either something is bypassing air, or something is keeping your throttle open when you lift. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 29, 2003 Share Posted August 29, 2003 There is a vacuum line on mine, that runs from the intake manifold, to somewhere on the bottom of the throttle body, is that what you're talking about? I couldn't figure out for the life of me what that connection would do. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted August 29, 2003 Share Posted August 29, 2003 It's also probably got something to do with turbine wheel blocking the way to let the exhaust air exist fast like N/A car. I personally got 11lb flywheel which I have to keep my foot on the gas to keep the rpm to upshift smoothly. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted August 29, 2003 Author Share Posted August 29, 2003 Yes I still have all those vacuum modules on the intake that came with the Automatic Turbo. One that holds the revs up for the automatic trans to shift smoothly sounds like it would be the culprit. But which is it? There is an Idle Control Valve, the AC Idle-up valve, the Air bypass valve, the EGR valve. The motor now idles correctly at 800 or so RPMs. and idles up when I turn on the AC. I tried pinching the hose for the Air bypass valve and it had no effect which tells me that that valve is closing correctly after warm up. Hmmmm..... Quote Link to comment Share on other sites More sharing options...
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