DCZ Posted December 14, 2004 Share Posted December 14, 2004 Our local Z club (Triangle Z Club, North Carolina) had a dyno day last sat and this is a scan of my baseline runs. This is a F54/P79, stock rebuilt about 10K miles ago. ZTherapy carbs with SM needles, K&N air filters. I'm pretty happy with it but of course I wouldn't mind squeezing a few HP out. Torque seems to drop off after 4500 rpm, limiting peak HP. I wasn't able to stay around and tweak anything. What do you guys think I might try as far as tuning? How does the A/F look to you? Base timing is approx 10 degrees. I have, I think, an L24 harmonic damper with an L28 timing indicator and they don't line up well, so I haven't gotten a good handle on the timing. I noticed that my fuel pressure went from 4 psi down to ~1 at high rpms, yet the A/F doesn't show any leaning. I guess the float bowls still had gas? Might this be a problem for a longer WOT run? Thanks for any comments. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted December 14, 2004 Share Posted December 14, 2004 Yes it looks like the float bowls still had fuel, it might be a problem on higher length runs though. Looks like maybe your fuel pump isn't up to the task. You should be able to run a little more timing if you are using high octane fuel. Try 12 degrees initial if you can figure out how to read your setup! With Torque falling off so hard after 4500rpm I'd be looking to eliminate the air restrictions in the system. I'd say either your exhaust or intake (or both) is choking off the car pretty badly at high RPM... are you using the stock cam? If so, there is a lot to be gained yet! Your AFR's look reasonable to me. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 14, 2004 Share Posted December 14, 2004 If the head isn't shaved then you should have 8.5:1 compression. You can crank in a lot more timing before octane becomes an issue. You should be shooting for somewhere in the mid 30's total advance. If you have a ZX distributor that equates to 18-20 degrees advance at idle, with no vacuum advance. I think Drax is right, a cam would help. I noticed a big improvement when I was running an L28/E31 combo and went to a bigger cam. It still never wanted to smack the rev limiter at 6800 very hard, but it could at least get there. Your dyno graph looks like there would be no point in revving too much farther than 5500 or so. All the fun is up in the higher rpms... Quote Link to comment Share on other sites More sharing options...
DCZ Posted December 14, 2004 Author Share Posted December 14, 2004 Yes, stock cam, whatever was stock on an 82 ZX. Previous owner said he only trued the head surface, so I imagine compression is close to stock. Exhaust is 2.5 inch with a bullet in the tranny tunnel and a flowmaster muffler. I need to spend a little time and figure out a good way to read my timing accurately. And I wouldn't mind throwing my little woodpecker fuel pump in the trash. Any suggestions for a good low pressure, low $$ fuel pump? Quote Link to comment Share on other sites More sharing options...
Clifton Posted December 15, 2004 Share Posted December 15, 2004 Exhaust is 2.5 inch with a bullet in the tranny tunnel and a flowmaster muffler. I would loose the Flow disaster and run a straight through muffler on the rear. If you have a timing light with the adjustment knob on it it's easy to check your total timing with the revs up. I would do as jmoertensen suggests and run it in the mid to upper 30's. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted December 15, 2004 Share Posted December 15, 2004 Wow... that looks EXACTLY like my charts from when I last dynoed my turbo setup. So L6's DO behave relatively similiar whether turbo or N/A. My peaks and fall off points are almost at exactly the same rpm's as his. I too am 99% sure that I have a restriction problem keeping my peaks so low in the RPM. With headers, exhaust and cam, there's still quite a bit of power to be freed up with your setup. I had a very similiar setup, higher compression though, and mild cam and exhaust, I put down 170hp. A friend of mine that still hangs out on Zcar.com, got 160rwhp on a mustang dyno with the same block/head combo as yours Quote Link to comment Share on other sites More sharing options...
DCZ Posted December 15, 2004 Author Share Posted December 15, 2004 Thanks for the ideas guys. Clifton, I hear you on the flowmaster. Never liked the sound of that muffler much but it was on the car when I bought it so I've kept it so far. OK at WOT but very boomy otherwise. I figured since it was so loud it must not be restrictive. First order of business is to figure out the timing and see what the butt dyno says. Quote Link to comment Share on other sites More sharing options...
Guest Ricter Posted December 22, 2004 Share Posted December 22, 2004 it sucks I missed your run. I showed up to run three cars after you. I would have liked to see your car on the dyno. -Richard Idalski Quote Link to comment Share on other sites More sharing options...
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