High rev Q's

kinkyllama · Post by **kinkyllama** » Tue May 09, 2006 6:19 pm

How bad is it to downshift into 7k rpms? I match the revs best I can..which is 6,500 before downshifting. I do it alot on the track.. I know I could put it in third then 2nd but its much more effecient to throw it right into 2nd and hitting 7k rpms.

Whats your guys input on this?

Danny

Post by **PrecisionBoost** » Tue May 09, 2006 6:43 pm

you crazy man :smt073

I'd guess your hitting fuel cut.... I'm not entirely sure if you would be damaging your engine or not.

Racing will decrease the life of the engine anyways.... so.... it's probably not going to kill anything any time soon.

If it does.... a new engine is fairly cheap.

JohnnyC · Post by **JohnnyC** » Tue May 09, 2006 6:44 pm

Well... I'm not an expert, but here are my thoughts.

6500 RPM is the specified limit for our engines. I don't like to exceed the limits of my engine's rated capability mainly because I don't want to put too much stress on the engine parts and have something bad happen.

I would just hate to see something horrible happen to my engine. But it's your car, and I say you should do whatever you want with it (as long as you're not endangering anyone except yourself) hehe. To be honest I don't know what it would do for you.

Post by **PrecisionBoost** » Tue May 09, 2006 6:51 pm

I don't think it's a question of mechanical stability...... they allways under rate RPM levels.... you could probably go to 7500RPM without an issue... but I'm worried about the ECU freaking out and cutting fuel.... which could lead to conditions where detonation could occur.

MMamdouh · Post by **MMamdouh** » Tue May 09, 2006 8:22 pm

my friend nefary once did that accedantly and broke a tappy... most probably you will run into free floating issues with the valves and they might collide with the pistons or so.

http://www.daewootech.com/forum/viewtop ... ght=#39189

i recommend against doing that as it seems dangewrous for yuo and the engine.

MMamdouh

kinkyllama · Post by **kinkyllama** » Tue May 09, 2006 8:52 pm

chris@PrecisionBoost wrote: but I'm worried about the ECU freaking out and cutting fuel.... which could lead to conditions where detonation could occur.

What if I just increased the rev limiter to say 7k rpms and tune the engine all the way up to that to prevent such a thing. Then dont ever go above the old limit except for downshifting.

Like Chris said though they underrate rpm levels.. I'm sure you could safly move the rev limit to 7k rpms and leave the engine stock with out ever running into problems other than slightly decreasing engine life.

What exactly is the engine doing when downshifting? Is it still burning fuel?

Nubira2.2 · Post by **Nubira2.2** » Tue May 09, 2006 10:14 pm

yes man it is burning fuel

when your start your engine and it's out of 0 rpms it is burning fuel

@ 7000 rpm is burning a lot of fuel

because the injectors are injecting fuel 7000 times every minute

eljunito · Post by **eljunito** » Tue May 09, 2006 10:41 pm

Joso · Post by **Joso** » Tue May 09, 2006 11:00 pm

Nubira2.2 wrote:yes man it is burning fuel

when your start your engine and it's out of 0 rpms it is burning fuel

@ 7000 rpm is burning a lot of fuel

because the injectors are injecting fuel 7000 times every minute

That's not entirely true. You could burn more fuel going full throttle at 1000 rpm than not pressing the throttle at all at 5000 rpm.

Anyway, going back on topic, if you downshift to 7000 rpm, fuel will be cut off and you will lose a little of engine braking. There's no need to downshift so hard. It should me made in order to be able to accel. harder when exiting the corner so I try to have my engine at 4000 when I downshift.

Nubira2.2 · Post by **Nubira2.2** » Tue May 09, 2006 11:07 pm

sorry for the mistake you are right

Post by **Efratech** » Wed May 10, 2006 5:14 am

are u using the stock rev counter? if so how much it marks? 7000?????

because i still dont get it.... 3rd gear..... downshift into 2nd and it hits 7000?

wait a bit more till the car gets a bit less speed so u can downshift into 2nd and the revs get a little lower. or just keep it in 3rd... you will need to get into 3rd anyways...

klonek78 · Post by **klonek78** » Wed May 10, 2006 5:35 am

To gain max performance(acceleration) gears should be always changed in range between max.torque and max.hp
You should get dyno data of your car and mark points of max.torque and max.hp - ex. 4400rpm@max.tq and 5800rpm@max.hp for x20sed. That's why it is very useful to have "shift light"....

nefary · Post by **nefary** » Wed May 10, 2006 1:06 pm

I know that the lanos Tacho is not that accurate one . if you hit the gas and reach 6500 from 2500 in the 1st gear the tacho will refer to 6000 only ( really the tacho not move fast as the engine) so if you downshift from 4th to 2nd as an example the tacho will not refer to 7000 rpm for sure
You can feel it when you go 6500 rpm while in N position you hear the engine hesitate but the needle refer to 6500 without any change
I have a sunny(sentra,almera) it has a perfect tacho the needle jumb fast from 2000 to 6000 in down shifting and it is accurate)

the timing built in our lanoses are not ready for this downshiftting inthis hard action the built will expand for a while and let the pestons hit the valves ( no matching between the camshaft and cranckshaft) . and if you downshift to 7000 where you will go more than that??? for bracking issue? ok the kings of this stuff are the japanese . I saw in many many videos they do that but they hit the gas slightly before they leave the clutch (to decrease the gap between the transmission RPM and engine RPM) after that they reach the limit and go for the lower gear

kinkyllama · Post by **kinkyllama** » Wed May 10, 2006 5:27 pm

Joso wrote: Anyway, going back on topic, if you downshift to 7000 rpm, fuel will be cut off and you will lose a little of engine braking. There's no need to downshift so hard. It should me made in order to be able to accel. harder when exiting the corner so I try to have my engine at 4000 when I downshift.

I know, I dont do it for engine braking as the brakes overpower that so much, especialy with the liter flywheel and goodies. I do it to put it into gear so im not doing it halfway into the corner and upsetting the car... though I'm just starting to learn trail braking and all that so thats not a big deal cuz I'm smooth. But there is one particular corner if you were to down shift it you'd lose it in a sec because its very bumpy and slippery, plus theres a wall you'd probably hit.

Efrain A. wrote:are u using the stock rev counter? if so how much it marks? 7000?????

because i still dont get it.... 3rd gear..... downshift into 2nd and it hits 7000?

wait a bit more till the car gets a bit less speed so u can downshift into 2nd and the revs get a little lower. or just keep it in 3rd... you will need to get into 3rd anyways...

Stock redline is 6,500rpm. I dont know what If I said it wrong somewhere but I ment going from forth to second. I've already bit hitting the brakes pretty hard, I blip the gas, downshift into 2nd from 4th and hit approx 7k rpms for a split second before it comes down.

klonek78 wrote:To gain max performance(acceleration) gears should be always changed in range between max.torque and max.hp
You should get dyno data of your car and mark points of max.torque and max.hp - ex. 4400rpm@max.tq and 5800rpm@max.hp for x20sed. That's why it is very useful to have "shift light"....

Yeah, well to a point. I think its better for my car to wait till a bit after the power starts to drop off, but not much. My exhausst is way to big for my car so I dont make much power down low.. so I try to keep the rpms up a little higher from where my power drops off cuz if I shift right where my power starts to drop I get too low in the rpms.

nefary wrote:I know that the lanos Tacho is not that accurate one . if you hit the gas and reach 6500 from 2500 in the 1st gear the tacho will refer to 6000 only ( really the tacho not move fast as the engine) so if you downshift from 4th to 2nd as an example the tacho will not refer to 7000 rpm for sure
You can feel it when you go 6500 rpm while in N position you hear the engine hesitate but the needle refer to 6500 without any change
I have a sunny(sentra,almera) it has a perfect tacho the needle jumb fast from 2000 to 6000 in down shifting and it is accurate)

the timing built in our lanoses are not ready for this downshiftting inthis hard action the built will expand for a while and let the pestons hit the valves ( no matching between the camshaft and cranckshaft) . and if you downshift to 7000 where you will go more than that??? for bracking issue? ok the kings of this stuff are the japanese . I saw in many many videos they do that but they hit the gas slightly before they leave the clutch (to decrease the gap between the transmission RPM and engine RPM) after that they reach the limit and go for the lower gear

I have a forenza, and the tach seams to be pretty accurate.

Yeah, I blip the gas on the track to.. its really not hard once you learn. See though they have higher hp cars so many times they down shift a couple times in a corner. I think it'd be more effecient to put it into 2nd and hit 7k rpm (redlines 6.5k) than put it into 3rd for a split second.. I mean, by the time the cars fully in 3rd gear I would already put it into 2nd. It's just extra input that isnt really needed.

klonek78 · Post by **klonek78** » Wed May 10, 2006 6:28 pm

kinkyllama wrote:
klonek78 wrote:To gain max performance(acceleration) gears should be always changed in range between max.torque and max.hp
You should get dyno data of your car and mark points of max.torque and max.hp - ex. 4400rpm@max.tq and 5800rpm@max.hp for x20sed. That's why it is very useful to have "shift light"....
Yeah, well to a point. I think its better for my car to wait till a bit after the power starts to drop off, but not much. My exhausst is way to big for my car so I dont make much power down low.. so I try to keep the rpms up a little higher from where my power drops off cuz if I shift right where my power starts to drop I get too low in the rpms.

So you have to change gear ratios to fix this problem........