Taxman Posted June 9, 2014 Share Posted June 9, 2014 Took my new SpecZ out to the track yesterday and I had a great time. These cars are a blast to drive! I do have some thoughts & questions that I would appreciate feedback on. 1) It is great to have some power!! I've been racing Spec Miata for 10 years and the most RWHP I've had is right around 120. The 250 or so I have now makes me feel like a god. 2) Did you know if you hit the throttle to soon in a corner you can actually spin a car?!? This isn't something I experienced much in (or EVER) in my Miata. The throttle was almost an on/off switch. It took me a bit to figure out I couldn't do that! 3) My car was really hard to get on the trailer! I ended up having to remove the NISMO front end just to load & unload. Not a big deal by itself, but in my haste to leave home the distraction of the loading delay contributed to my leaving some equipment at home (like a tire pressure gauge). So... I did drive the entire day without knowing my tire pressures. The car didn't suck so I am assuming Scott had the correct pressures in the tires. 4) I wasn't on R1s, but ran on some Hankooks that were on the car. I have always enjoyed driving on good street tires as a change from R compound, and these were solid tires! A couple of issues.... 1) Brakes - I was having a very soft pedal after a couple of laps and I intitally thought it was fade. However now I think it was pad knockback. Is that common? If so, how do you handle? Because... 2) Does the throttle shut off when you touch the brake pedal? I was tapping the brakes (left foot) before each hard braking zone and if felt like the engine would cut out. Is that correct? If so, can we turn it off (legally)? 3) I was crushing the rear bumpstops at my ride height. That was basically how I drove my Miata (probably was never much off the bumpstops), but I was experiencing alot of snap throttle on oversteer. That could be my lack of throttle control but it was consistent even as I learned the car throughout the day. Are the bumpstops "not a good idea" overall, or do many of you intentionally hit them? My biggest thought was surprise that this class isn't larger. The car is a blast to drive and the cost of entry isn't crazy for a really good looking car! Unfortunately for me, I might have already peaked. I had my best lap of the day in my first session (2:35.8 which is slower than the SM track record but now my personal best) and never got back within 1 second of it. Thanks for any feedback you have. I can't wait to get on the track with some other SpecZs. Wish I could get the races under my belt to qualify for Nationals, but I started too late this year. Quote Link to comment Share on other sites More sharing options...
laze1 Posted June 10, 2014 Share Posted June 10, 2014 1) Brakes - I was having a very soft pedal after a couple of laps and I intitally thought it was fade. However now I think it was pad knockback. Is that common? If so, how do you handle? Because... Knockback with Brembos is a common issue...replacing the front hubs/wheel bearings lessens the problem..but still will happen when running Slicks. However pad knock back symptoms is "no pedal" not "soft pedal" And if you haven'v done this yet, rebuild your calipers...do the Master Cylinder as well. Brake ducts help@ What pads/fluid are you running? 2) Does the throttle shut off when you touch the brake pedal? I was tapping the brakes (left foot) before each hard braking zone and if felt like the engine would cut out. Is that correct? If so, can we turn it off (legally)? Yep, this is normal, you can cut a wire to the ECU from the Brake light switch to prevent this from happening...lemme see if I can find the info on this mod. And as you found out, you need to do a "luv tap" on the brakes because of the pad knock back issues. 3) I was crushing the rear bump stops at my ride height. That was basically how I drove my Miata (probably was never much off the bumpstops), but I was experiencing alot of snap throttle on oversteer. That could be my lack of throttle control but it was consistent even as I learned the car throughout the day. Are the bumpstops "not a good idea" overall, or do many of you intentionally hit them? Z-cars DO NOT LIKE to be real low in the rear or hit the bump stops...and as you found out will spin/be uncontrollable when you hit the bump stops...so you need to raise the rear of the car. Quote Link to comment Share on other sites More sharing options...
TXOL Posted June 10, 2014 Share Posted June 10, 2014 John, If you track down the details on the throttle fix please post them. I need to make the change too. Taxman if you check out the post about TX Spec Z with a video you can see a fellow bump stop spin victim in action. MG Quote Link to comment Share on other sites More sharing options...
laze1 Posted June 11, 2014 Share Posted June 11, 2014 BTW the best way to fix the brake+throttle cut is to intercept pin 101 "stop lamp switch" at the ECU connector. pin 101 L/OR Stop lamp switch You can find the circuit drawing in page EC-109 of the Factory Service Manual Engine Control Section. I am trying to save these pages into a .jpg from a .pdf right now so I can post them Quote Link to comment Share on other sites More sharing options...
Taxman Posted June 11, 2014 Author Share Posted June 11, 2014 John, Is that mod legal? I'd love to do it, but I don't see it as a permitted modification in the Spec Z rules. The car came with Raybestos ST4X pads. Not sure on the fluid. I'll probably try some Carbotech pads next as that is what I have run for years on the SM. Quote Link to comment Share on other sites More sharing options...
laze1 Posted June 11, 2014 Share Posted June 11, 2014 Well...... ...... I will petition the NASA to add this to the rules...as it is a safety issue... Quote Link to comment Share on other sites More sharing options...
laze1 Posted June 11, 2014 Share Posted June 11, 2014 I sent this to NASA HQ today: "I have a new rule proposal that I believe is a "Safety" issue. As you may know, the 350Z Brembo Calipers have an issue with "Pad Knock-back". Since there is really no way to eliminate the issues 100%, I propose this work around to allow for the modification of the ECU wiring harness to "cut pin 101 L/OR Stop lamp switch signal" lead. This modification will allow for "left foot braking for the purpose of confirming that the pads are in the proper location. Note: This mod doesn't affect the stop lights from functioning. This mod only prevents the ECU from recognizing the application of the brakes and subsequently cutting engine power to part throttle. Regards, John Evans" Quote Link to comment Share on other sites More sharing options...
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