karpetcm

iTrader: (2)

Well ive raced a couple of times and since i have 4.10's i pretty much have to shift from 4th to 5th at about 118mph. Is it safe to spray partially if i need to shift into 5th to about 130-135mph ?. I know 5th is overdrive and probably not the best idea to do that but has anyone done this and what are your suggestions and experiences. The shot is about 125 and soon to be a 150 shot dry after tune and injectors.

thedudeZ

iTrader: (14)

No. turn more rpms or get a taller gear.

TINKRD

iTrader: (27)

spraying 5th is more of a myth IMO. cylinder pressure is longer and you have a greater chance of burning a plug. but if you're tune up is safe and not on the edge, there's not really an issue.

keep the tune fat, get some colder plugs and dont get greedy with timing.


or do like mentioned above.

thedudeZ

iTrader: (14)

No, I'm wrong, do what he said, fatten it up with 26* timing, then slam it into 5th and lug the hell out of the motor. It will be safer and not on the edge.

TINKRD

iTrader: (27)

no one said you were wrong smart guy. and no one should be spraying 150 shot on 26*timing in any gear (going off the assumption we're talking stock'ish compression)

now if you want to have a grown up adult conversation about the harm of spraying 5th gear i'm up for it. I've already mentioned the reasons in my post and can go into further detail on each of those reasons. What's your reasoning? lol

TINKRD

iTrader: (27)

I could further prove you wrong with your comment on more RPM's or more taller tires, but I'll await your rebuttal first.

karpetcm

iTrader: (2)

Thanks guys, i dont want to cause an argument with peeps on here just appreciate any advice. I will take to Frost about getting it as safe as possible so if i need to spray in 5th he has me covered with the tune.

ducatisl

iTrader: (1)

I'm in a similar boat: I have a 1/2-mile event coming up and last time, all-motor I was topping out in 4th, but hopefully this time around I can get it into 5th by spraying something between 100-150. Should I pull an extra degree or two out of the tune?

TINKRD

iTrader: (27)

its what i said above. the longer you spray the more chance you have of that plug getting too hot and then causing pre-ignition and that's what will break a ringland and make a motor go kaboom...

if you want to spray a motor for a longer time span. go down to a colder plug, take some timing out. add some extra fuel, make sure its not lean. HEAT is the enemy.

if you REALLY wanted to do it right. you would log your runs with a scanner (HPTuners). watch for KR. At the end of the pull kill the motor, coast to a stop, pull your plugs and examine them. look at the timing mark, look at the color of the porcelain. get a wide band.

all these things are what it takes to make a motor last, period. regardless of nitrous or boost.

ducatisl

iTrader: (1)

I do log my runs and adjust between runs with HPT and wideband input, also running BR7's Going to sort things on the dyno a week before the race, but since it's not a load bearing dyno, I was thinking that during an actual race, heat, like you said, might be a problem.

TINKRD

iTrader: (27)

most mile events you get multiple runs. best you can do is do a couple shake down passes. or if you have a long stretch of highway somewhere, test before heading out.

thedudeZ

iTrader: (14)

Point is anything past 1:1 ratio is going to lug the motor and drop the rpms too much. I consider OD(that I don't have) a luxury and a cruising gear. Nothing more.

Again, if you want to go faster, either wind it higher, taller gear or taller tire. OD is not an option at all for a power gear.

karpetcm

iTrader: (2)

So whats a safe rpm to bump up to without damaging anything. I have a stock motor full bolt ons and 125 dry shot. Can i rev it till about 6200rpms? maybe that might give me an extra couple of mph. I think right now im at about 6k rev limiter. Ill probably have my tuner pull an extra degree of timing out and adjust the A/F accordingly. Im going to run a max of 125 shot dry with 32lb Svo Injectors and i have the TR6's. I know not the best plugs havent had any issues with them on my last nitrous car or this one but as they say you never know.

thedudeZ

iTrader: (14)

Personally never had an issue spraying up to 7200 on a stock bottom end 110k miles.

karpetcm

iTrader: (2)

stock bottom but did you do anything to the valvetrain. Im more concerned with the valvetrain sicne the springs and so on wont handle higher rpms.

TINKRD

iTrader: (27)

4.10 gears, 26inch tire, 5th gear .74:1. said he redlines 4th at 115mph

that makes his rpms drop to 4800-5000pms on the 5th gear shift. that's not "too much" at all.

is that your reasoning on why you're not supposed to spray 5th? lol

TINKRD

iTrader: (27)

you're on nitrous. there's no reason to whined the car up that high. its not a N/A motor where you need that max HP uptop. the nitrous is providing the TQ/HP.

do your valvetrain a favor and either get a bigger tire or make the necessary adjustments to safely spray 5th gear.

kidcamaro98

iTrader: (8)

5th gear is a over drive. Not a power gear. Your choice to spray in 5th, but there will be no benefit from it, and can potentially cause problems.

beef up your valvetrain and revv the pig out, or get a taller tire. I have 4.11's and when I was on a 26" MT, I was shifting into 5th at 130-135. However, I was shifting at 6700rpms.

now I am on a 28" nitto, and my gears are longer. Spraying a 150 shot here. As soon as I hit 5th, I shut the spray off.

thedudeZ

iTrader: (14)

actually rpm drop is to around 4400-4500 from 6000. That is a healthy drop.

We'll agree to disagree. if he spun it to 6800 in 4th roughly 126mph going to 5th would drop roughly 1800rpms.

3.73 would be a good gear and allow you to go to 140 in 4th gear at 6800 WITH the tire you have now. Or your current 4.11 gear with a 28in tall tire would still put you up to 140 in 4th gear at 6800.

Get some valvesprings.

ducatisl

iTrader: (1)

Lots of information and everyone is playing nice, this is good.

Makes you wonder how guys are spraying in races like the Texas Mile.