BayAreaZT Posted July 17, 2003 Share Posted July 17, 2003 Went to the track last night to get a few runs in and get the car dialed in. This was my first time at the track in at least 5 years and the first time with my turbo 240 so I needed a few runs to practice and really get the car dialed in. Problem is there were so many cars at the track that I was allowed to run 1 practice run On the practice run I wasn't expecting anything spectacular. Just wanted to get a feel for what the car would do at 10psi with the shift light set at 5600rpm. Launch was okay but not great. Managed a 2.1X 60ft time. Boost peaked at about 11 or 12 and settled aroud 10psi. My shifting on this run really sucked. I was basically shifting like I do on the street and not banging it through the gears. The real problem was the top of third gear. When I got close to 5000rpm, my rpm wouldn't climb steadily. It was cycling up and down. It was like I hit a rev limiter but it only happened in third gear I ended up going through the trap still in third with a 15.1 at only 85mph (still beat the camaro I was up against ) I figured even with the problem in third, if I shift a little faster and sooner (felt flat at 5600) I would definatley be in the 14s. Second run was eliminations already. I just installed my grainger valve at lunchtime and didn't have time to dial it in yet (was hoping to do that with practice runs). So I just tightened it down a little hoping to get 12-14psi. I staged and was reving the engine and somehow I must have rolled forward a little and triped the light. I didn't think the other car (300ZX TT) staged yet and I thought I could re-stage but he took off already and basically I was eliminated. Good news was the second run felt much better. I shifted at 5200 and scratched every gear change. ACT clutch definatly grabs. Still had the problem in third gear but I uped my mph to 92. Boost was still at 10psi. Any idea what the problem in third might be (timing, fuel, AFM, TPS?) I have the audio if anyone needs it to diagnose the problem. Another weird thing is on the way home without changing anything, I was boosting 14-15psi with no problem. Car felt quicker than it's ever been Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 17, 2003 Share Posted July 17, 2003 What engine, what mods? What fuel pump are you running? What is your EFi system, stock? or something aftermarket? What fuel tank are you using? Need some more info please! Quote Link to comment Share on other sites More sharing options...
TimZ Posted July 17, 2003 Share Posted July 17, 2003 The real problem was the top of third gear. When I got close to 5000rpm, my rpm wouldn't climb steadily. It was cycling up and down. It was like I hit a rev limiter but it only happened in third gear I ended up going through the trap still in third with a 15.1 at only 85mph (still beat the camaro I was up against ) I figured even with the problem in third, if I shift a little faster and sooner (felt flat at 5600) I would definatley be in the 14s. Clutch starting to slip, maybe? Generally if your clutch is starting to slip, you'll notice it in the higher gears first. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 17, 2003 Share Posted July 17, 2003 More info needed. You could have a lot of different problems. What does the boost do when the rpms fluctuate? Make sure you clean the connections at the ecu with brake clean really good. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted July 17, 2003 Author Share Posted July 17, 2003 It's a stock L28et with stock efi, mkIII supra ic, 1G eclipse BOV, ACT clutch with ZX tranny and 240mm flywheel. My gas tank is the stock '71 with the feed line at the drain plug and I had half a tank of gas. Fuel pump is stock running stock pressure. Boost seems to stay consistent when the rpms fluctuate but I'm not 100% positive. I have cleaned the ecu connections 2 or 3 months ago. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted July 17, 2003 Author Share Posted July 17, 2003 Forgot to mention 3.54 diff and 25.1" tall tires. Is it normal that I'm barely getting into 4th with this combo. I have the stock DP with a 3" section that goes to a 2.5" crush bent exhaust (1st on the mod list). Quote Link to comment Share on other sites More sharing options...
Jersey Posted July 17, 2003 Share Posted July 17, 2003 Bay, send me the audio. I'd like to hear it. Have you ever checked fuel pressure with that kind of boost at 5k rpm? Stock pump may be failing a little bit. i just re-read your post - you say you just put the grainger valve in, right? Did you happen to have threaded the WG actuator before that and that is how you controlled boost? If so, that's likely your problem. I read a post on where you'll need to take some pre-load back off that spring when changing over and using a G-valve. Just a thought. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted July 17, 2003 Author Share Posted July 17, 2003 I'll send you the audio later tonight. I have to download it to my computer when I get home. Never checked the fuel pressure. I don't have a gauge hooked up yet. I'm gonna check my plugs later and see if it shows anything. Never threaded the actuator arm. I just had a tee in line to purge off some of the signal to the WG actuator. It was a little laggy but it got me 10psi all day and cost me $2.00 Quote Link to comment Share on other sites More sharing options...
fl327 Posted July 18, 2003 Share Posted July 18, 2003 Dale- I suggest before you start doing anything, clean off your TPS injector ecu afm head temp sensor connectors, clean them with either electrical contact cleaner or brake cleaner, then drive it around and see if it still flutters at high RPM. i dont think its the plugs. may be fuel related, i love the 10ga relay trick, brought my car to life. also check the timing, but i dont think that would be an issue too much, just thinking out loud i guess. Maybe next time you go, Ill be there Quote Link to comment Share on other sites More sharing options...
Guest zpeedracer25 Posted July 18, 2003 Share Posted July 18, 2003 I've got a very similar problem in my 280Z. It feels like you hit the rev limiter early. My problem happens in the first three gears and is only there under hard acceleration. You can watch the O2 sensor output signal and I'm sure it will show that you are running lean when this happens. I'm still in the process of finding out exactly what is causing this to happen. Changing timing on mine does effect the RPM at which it happens...it lowers it to 4000 RPM whether I advance or retard it. But watching the waveforms out of the crank sensor, they look fine and I see no problems and the dist is lined up correctly. I've also watched the AFM and TPS and I can see the effects of fuel cut showing up in the waveforms. And yes, I've checked fuel pressure and volume, connectors, and I've swapped in my spare ECCS, TPS, and AFM and still same results. Every time I try to watch the waveforms of the injectors while this happens, but everytime I probe them the car runs great About the only thing I can figure is that I've got a 2 bad ECCS' because the sypmtom is just like coming up against the rev limiter. Hopefully some of this info will help us both to figure out whats up. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 18, 2003 Share Posted July 18, 2003 Hahah BayareaZT you're and my setups are gonna be even closer than mine and Jerseys.... I'm finally dropping my car off with the mechanic this weekend... it will be 90% identical to yours just a different diff (I have a 3.9) and no I/C yet but I was actually planning on getting that exact same IC you have. I'm surprised to see I'm not the only one around here doing this setup with the stock 240 fuel tank! I also just got my Grainger valve from Mcmaster, good to hear more positive results from the cheapest MBC on earth About your problem my first idea would have been clutch slip too but with the ACT you shouldn't be getting that. Second guess from me is fuel, sounds like it's starving out at high revs. I know that the stock fuel pump is a pretty weak link in the chain for this engine, once you up the boost. I have heard that using thicker gauge wires can help this a bit, as well as adding an adjustable FPR, and eventually upgrading to a better pump. It seems everyone who's posts I've read here and at Zcar.com, who runs 10psi on a stock EFI system runs into the problem of running lean at the top, though usually not lean enough to detonate, it will get lean enough to get big power losses usually above 5k. Yo2001 suggests the FPR alone is enough to solve this problem, put one on with a gauge and bump pressure to 44psi and you'll be fine with the stock pump. By the way BayareaZT, can you give a better explanation of how you hooked your grainger mbc up, as far as the tee you mentioned? I'm assuming you're talking about a hose with a restrictor in it to bleed the pressure off the WG when you let off the throttle? To avoid drilling that tiny hole in the 90* barb right? If you're using a restrictor, where did you get it? I dont have easy access to a drill so I'm most likely going to do this tee also. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted July 18, 2003 Share Posted July 18, 2003 Narrowband O2 isn't going to tell you much under WOT. Mine always stayed at 10:1 even with my EGT at 1620deg. I was losing torque after 5000rpm on my dyno with stock t3. I'm sure it was going out of effiency around there. (blowing heat) I went to 60-1 with stage III and my car revs alot hard after 5000rpm. O, and probaly could use more timing too. race gas and bump the timing. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted July 18, 2003 Author Share Posted July 18, 2003 It does feel like a rev limiter but it's weird how it doesn't happen in 1st and 2nd. I guess it only happens under heavier loads. I will go back and clean all the electrical connections again and try messing with the timing a little. I've been wanted to re-wire the fuel pump with the relay and 10ga wire but I just haven't gotten around to it yet. bastaad - I've been reading your posts and I figured our setup will be pretty close. It will be interesting to see how your car does with the 3.90 vs. the 3.54 gearing. The stock fuel tank has been working out fine. The previous owner said the tank was cleaned out and they put baffles in it. I'm not sure if he was BSing cause I didn't really care at the time. I just don't let my fuel level go lower than 1/4 tank. My boost controller is the pressure relief valve with the screw on barb on one side. On the other side I was in a hurry to make so I drilled out the hole on the adjustable side and used JBweld to glue a 1/4" barb cutoff from a plastic tee. Connected that end to a 1/4"x1/4"x1/8" tee. I'm using the 1/8" barb as the pressure relief. Like I said I was in a hurry The tee I was talking about was what I was using before the grainger valve. Quote Link to comment Share on other sites More sharing options...
Guest zpeedracer25 Posted July 18, 2003 Share Posted July 18, 2003 Narrowband O2 isn't going to tell you much under WOT. Mine always stayed at 10:1 even with my EGT at 1620deg. Yo, If you watch your O2 waveform in real time on a lab scope as I was doing, its pretty instantaneous and usable information. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted July 18, 2003 Share Posted July 18, 2003 yap Quote Link to comment Share on other sites More sharing options...
Bernardd Posted July 18, 2003 Share Posted July 18, 2003 Narrowband O2 isn't going to tell you much under WOT. Mine always stayed at 10:1 even with my EGT at 1620deg. Yo' date=' If you watch your O2 waveform in real time on a lab scope as I was doing, its pretty instantaneous and usable information.[/quote'] I have access to a fluke scope. I can connect this and go for a run. What am I looking for that'll tell how rich or how lean? Bernard Quote Link to comment Share on other sites More sharing options...
Guest zpeedracer25 Posted July 19, 2003 Share Posted July 19, 2003 After you probe into the O2, run the car at 2500 RPM for two minutes to make sure the O2 is at operating temp and the computer is in closed loop. You should then be able to watch the O2 switch between 1.0 volts and 100-250 mV if the computer is in good fuel control. Watching the O2 while driving the O2 should continue to switch...1.0 volt being on the extreme end of rich and 100 mV on the extreme end of lean. Under full throttle you should go rich(above 500mV)...O2 should probably flatline and abandon fuel control and go to fuel enrichment as mine did. When my car would feel like it hit an early rev limiter the O2 would go from 800 mV straight down to 100 mV in less then 10 msec and stay there until I eased out of the throttle. I had my scope set to 100 mV/division and time frame of 50 msec/division to easily see what was happening. Plus it helps that I know a guy down the road that does diesel emission testing and was able to use his dyno to make testing different components on the car easier. The O2 waveform can tell you a lot if you know what you're looking at. Anyone who's ever sat in on a Chris Chesney(spell check please!) waveform analysis class knows whats going on. Unfortunately for me I only got to go to one of his Carquest classes. Good luck. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 20, 2003 Share Posted July 20, 2003 Try this, take the dizzy cap off, and then put it back on. Don't ask me why. Quote Link to comment Share on other sites More sharing options...
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