Pistolio

hey all

just a quick question regarding when to shif gears and stuff.

where abouts in the rev range does the power start to kick in? im more talking about shifting gears to get the best launch and times and stuff. is it better to simply hold each gear to redline or would u get better times shifting earlier in the revs, if so when?????

also my tacho shows up to 7,000 i think but redline starts at 6 (well yellow till 6.3, then red aftar up to 7) iv never reved it past 6.000. should i hold it into redline when trying to get good times or shift b4? (iv never held it into redline b4)

lol may seem like silly question to some but u gotta ask em

WildmaN

Honestly if you don't want to do engine damage. I would shift before redline. I found when I wanted a quick take-off, or show somebody that my Z was no slow dinosaur. At the most I shifted into 5 grand. But not verry often. I didn't want to hurt my engine. After all there is a reason for the red and yellow lines. Kind of similiar to traffice lights. yellow be careful, a warning, red stop you are hurting the engine! And it is not really a silly question. Some people don't understand what they mean. But like the example I gave you with the traffic lights. It makes perfect sense, to me anyway. Hope this helps!

81 Black L28E

5200 rpm is your HP cap.. you wont get any more out of your motor unless you have mods and taking it more than that you just risk messing it up .....sometimes i go more but not very offten you can feel the power drop after 5200rpm......I red some where that the reson that most of the turbo cars came AT is becuase ....they made them this way so we couldnt over rev them as much it would make the motor last longer ...i want a big *** cam so i can rev to 8500rpm

jfairladyz

It depends on your driving style and the powerband of the engine. Taking the engine past it's powerband is not as bad as letting it drop below it. For acceleration anyways. If you take the engine past its powerband, power will start to drop off, not a big deal. It's usually gradual unless you take the engine beyond it capabilities, which is usually beyond redline. However, if you **** too early, you risk dropping below the powerband going into the next gear which can absolutely kill your acceleration. It's impossible to tell exactly where to shift for the best acceleration without a dyno chart and timing how long it takes you to change gears. You can try to feel it out, but remember to be most concerned with how hard the car is pulling after you change gears, and not right before. In most situations, and especially on a street car, you have to make a compromise. Nobody can answer your question but you. Go to a track and try different shift points. Figure out where power begins, and where it drops off before hand to give yourself a base to begin with. One rule of thumb though, don't under any circumstance over rev the engine, you won't see any benefit with stock valvetrain, cam, and bottomend, and worse case scenario, you throw a rod through your block. Every car is different, and every driver is different. Just get out there and drive.

lifegrddude

The post above is right, it depends on your powerband. Best way to determine your shift point is via a dyno graph and knowing your gear ratios. If you want to be exact read this article, dyno your car and then spend a little bit of time with a calculator. I'm not a big fan of crunching numbers, so I just went by numerous experiments at the track and found my shift points on my a/t zxt to be 6k in 1st, and 5800 in 2nd.
http://www.sportcompactcarweb.com/ed...ble/index.html

DoTheDrew888

I dynoed my car on the stock setup before I rebuilt the engine. It made peak power between 5000 and 5200 rpm. After that the valves begin to float because the stock valve springs do not "bounce back" fast enough. Reving up to 6000rpm on a stock engine is very dangerous. When valves float they can contact pistons and you can say bye-bye to your engine. Also, after 5300rpm the stock EFI can't keep up. Right now im running a big cam and performance valve train. I can rev it up to 6500 rpm with no problems but it noticably loses power in the higher rpm range because the fuel starts to lean out. That is why I am converting to carbs. Based on the cam specs I should be making peak power at 6500rpm with this setup and have the ability to rev out through 7000rpm.

Anyway, I have personally dyno tested it an I would say shift at about 5300rpm for best results. That is right before the power drop off and it is a safe rpm for your engine.

lifegrddude

Yours was n/a correct? Just curious. When I dynoed mine, it made peak hp at 5600 rpm. (173 at the wheels) Peak torque was at 4400. How many miles were on your valvetrain? I'm at about 110K on my motor (dynoed it at 93,000). My stock valvetrain floats at about 6500rpm, it feels like a rev limiter on modern cars. I haven't dynoed my Z31 maf setup yet, but it doesn't lean out like the stock setup did as my a/f gauge stays in the rich zone and pinging doesn't occur during extended freeway blasts. I doubt my shift points will change though since the camshaft profile is still the same.

s/cL3.0

It all depends on your motor like everyone else says.. The 533WHP Z my friend Clifton has will make peak power at 7600 RPM, his is a huge turbo though that doesnt hit full boost til 3400 RPM still will pull a 10.2 in the 1/4 mile though

Bleach

The power loss is actually too rich of a burn, not too lean. The fuel injection may not be that good at those higher rpms but it puts out enough fuel for a non turbo engine. The cam is the probelm. The duration is so short that at those rpms there is not enough air getting into the engine. A longer duration cam with stock fuel injection will give you more power and allow you to pull hard at those higher rpms. If you want to really go wild with the cam then carbs would be better or a better fuel injection system.

DoTheDrew888

Bleach, that is why I just bought some SUs .

I thought you guys might want to look at this. It is my friends stock 280Z with the N42 engine. Not a ZX but the dyno chart is basically the same.

http://www.atlanticz.ca/zclub/techti...l28naanalyzer/

Pistolio

cool thanks guys, yet another z problem solved

i have found that the car seems to pull the hardest around the 5000 rev range, im not certain where she starts to lose power but im thinkin from memory its in the really high 5's, iv never reved it beyond 6 grand and by the sounds of it thats a good thing.

yeh its a n/a z with 120k kms (well the driving one)

the thing is this one is an auto and iv been using the shifter to hold the gears longer. in my opinion it seems like the car pulls harder by using the stick and watching the revs rather than simply putting it in d and flooring it. would i be right or am i simply deluded? lol

thanks for the helps guys

Dorifto

Sounds right, Pistolio. On all the AT-equipped cars I've owned or driven - including my '88 Grand Am QUAD-4 and my stepdad's TransAm - the cars were noticeably hotter when manu-shifting them. In the case of the TransAm, the tranny was valved to shift at around 4500 rpm [the stock engine redlined at 5200], but with the prepped 400ci engine my stepdad swapped in, the powerband went from 2250-4000 to 3000-6700 revs. With the stock trans valving, it was great for street driving and getting groceries, but all-out performance was hindered because it shifted too soon.

I also think on some transmissions, when the lever is shifted into a lower numbered gear, the valving changes slightly to allow for more aggressive engine braking and acceleration - perhaps stiffening the whole tranny in general. I'm not sure about any of that, just personal experiences. Hope that helps.

-Dave-O

jfairladyz

Doriftos is right. The only reason manu-shifting your auto would make your car run better times is if, like D mentioned, it shifts too early in the powerband. However, if the trans will allow you to reach up deep into the powerband then manu-shifting won't help your case. I've never driven an auto Z though, so someone else will have to let you know how high it will let you go before it shifts. Don't overwork the tranny though. If you start churning that trans fluid, it'll turn to foam, and then your car ain't gonna go anywhere. Alot of time the torque convertor simply can't go to much higher without slipping through the fluid instead of catching it too. That's another thing to take into consideration. Once you surpass the shift points, does it feel like the car isn't picking up as much. That's the torque convertor. Go to a track and try different combos to which is fastest. This is easy with an auto because your base time of letting the tranny shift itself will be pretty consistant. With a manual, you have don't have that convenience. Good luck Pistolio, you just gotta get out there and drive man.

lifegrddude

The stock zxt tranny will short shift at 4800-5100 rpm if left in D.

Pistolio

lol thanks all, yeh i think the tranny does shift about high 4's or even5's, so im thinking there will be a small advantage of shifting with the stick, as long as i dont shift too early or too late.
cant wait till i get my other z finished its a manual and im sick of drivng a boring old auto, cept when u floor it and it down shifts its kinda cool.

but ur right bro i just gotta get out thar and drive (excellent!) just that im respraying her as we speak so she off the road for probs another week or so boooo