Meaning of Redline

[**Ghost**]

I've always thought redline means the max rpm u can go to before engine internals start dying or at least suffer damage.

however reading some other posts/forums i've noticed people referring to redline according the ECU attached to the engine rather than the engine itself.

Let me clarify

Some ppl have quoted different redlines for the same engine, on the basis they are running different ECUs.

I dont understand how can ECUs affect the strength of your internal parts?

or am i correct in assuming they are referring to something else?

[lerroy]

redline is the point at which your ecu cuts off the fuel hence why it just bounces
this isnt the point at which the engine melts im sure for example a B18c could rev past 9000 but it would not be healthy at all for the engine would put strain on the Cams etc...that are not rated to that much stress/revs

so honda in there wisdom put a limit on the revs this is the redline :)

hope that kinda helps

[egSi]

redline = safe line.

[ian]

"redline" is literally the redline on your tachometer which at some point during this rpm range the engine will hit maximum rev's preventing it to rev further (cut off) - to protect from over revving which may cause damage to your engine.

[ProECU]

Its not the cams which are the "strain" as you put it, its the piston due to material composition & piston acceleration which causes engine failure along with valve spring pressure (valve float) at extreme rpm's.

[ITRBoI]

i thought redline is just where your tachometer starts the red line and engine cuts off there to prevent damage to the motor......ie itr redline is about 8000 rpm inwhich where the engine cuts.....

[**Ghost**]

AUDM B16A P30, Redline: 8115rpm, Vtec: 5375

JDM B16A P30, Redline: 8290rpm, vtec: 5375

USDM DOHC Vtec P28, Redline: 7410rpm, vtec, 4810

Also note, vtec is load based, under low loads, vtec engagement is higher, approx 5800rpm for P30 and 5500 for P28


ok just to clarify using this example i got from a search. ProEcu/evan the redline u mentioned here is that the same figure as "cutout" as in when the ECU will jump in and say "u stop that at once bitch" and stop f uel?

[nobbs]

on my car the fuel cut off is past redline, so assume redline is the safest revs u should go to, although u can go a little past, but if u go past too much you will hit fuel cut out

[ProECU]

Correct.

The ECU will shut down the injectors at the above montioned Redline rpm's

[wynode]

On a stock ECU and stock car/cluster, does the start of the redline = same rpm as fuel cut out?

I assumed the start of redline was alwasy a bit before fuel cutout?

[Da1nONLY]

Well on stock cars..

Redline - What you see on the tacho, where the redline is....
Rev Limiter (Fuel Cut off) - Helps avoid over revving of the engine preventing it from damage. (Usually just a bit over redline)

e.g. on the dc2r - Redline is at 8400rpm. Fuel Cut Off at 8600rpm.

Cheers... :D

My definition anyways...

[barefootbonzai]

This discussion is just confusing. I think red line is literally the red line on your dash. Just an expression that we all have come to use. Don't think it's anything technical.

[wynode]

Also does the ECU only cut fuel or spark (or both?)

[**Ghost**]

barefoot - i think it was meant to be technical but then ppl just started referring to cluster as the "redline"

so redline = fuel cutout in technical sense from wot i'm gathering

whereas redline colloquially just means where the red bit begins...

[ProECU]

Also does the ECU only cut fuel or spark (or both?)

It only cust fuel, but it can be modified via the code to do both.

[SiR JDM]

Would there be any advantage/reason in cutting the spark as well?

[ProECU]

yes, under boost

[DLO01]

Spark with min fuel may cause a lean out. Cutting the fuel with the ignition will stop this.

[wynode]

So are there any issues (of running lean) with just cutting fuel only?

[DLO01]

So are there any issues (of running lean) with just cutting fuel only?
Yep, thats exactly it. If your on boost and bouncing off the limiter with 'just' a fuel cut, your motor is going to lean out, causing detonation and in the end bang! Cutting the Fuel and the Spark will stop it leaning out.

[wynode]

So on a NA car it isn't an issue (leaning out when hitting the limiter) ?

[ProECU]

Its still an issue for NA just not critical as per boost.
In any event, i'd try stay away from the limiter.

Also, for those who use the Hon$a$a WOT shift or Launch control, they use the fuel cut method.

[DLO01]

Also, for those who use the Hon$a$a WOT shift or Launch control, they use the fuel cut method.
Oh dear. :rolleyes:

[**Ghost**]

rofl... he just had to drop that... so rev to 7900 and i'll be fine...got it ^_^ thats all i wanted to know...

[bumography]

gUYS even i think i know the answer for this!
Redline is a guide to tell you when to change gears cos at redline theres not much more power to be gained. LoL (ie. Shift light)

am i right or wrong ?
i dont even know, i just watched some clip of a dude racing his ITR and changing it at redline as well as leaving the revs past 6000 rpm at all times throughout the lap

PS. Please dont flame my noobness

[Jr]

I know redline is to help conserver or not damage the engine but what happens if you have different engine parts. Like my self d15b7 block which I think redlines on old ecu at 6400 and d16y1 head which redline at 7400 with the ecu im using now, am I hurting the block by adding an extra 1000rpm to my redline?

[aaronng]

Is this still up for debate? In my opinion, the redline is a number set by the manufacturer after determining the maximum RPM that the engine can operate at (minus some tolerance for safety) and the cams are chosen so that peak power is made just below that redline RPM.

Hence, you can build up engine's internals so that it can tolerate higher RPMs, then change the cams or use forced induction so that you make power at that higher RPM and use ECU management control to alter the redline to suit your needs.

[lazymofo]

from Dictionary.com (http://www.dictionary.com)

red·line ( P ) Pronunciation Key (rdln)
v. red·lined, red·lin·ing, red·lines
v. intr.
-To refuse home mortgages or home insurance to areas or neighborhoods deemed poor financial risks.

-To reach the maximum engine speed at which an engine is designed to be safely operated: The car redlined at 80 miles per hour in fourth gear.
Computer Science. To mark or highlight edited text, as with a red line, to distinguish it from unedited portions of a document.

just thought id add my 2 cents

[kayot1k]

besides why would you want to rev to 7900 ? b16a i believe? u lose power after 7600.

on another note one time i revved my b16 on first gear to 8500rpm atleast i reckon. didnt realise how fast the car was.
:thumbdwn:

[DLO01]

besides why would you want to rev to 7900 ? b16a i believe? u lose power after 7600.:thumbdwn:
No, you want to change gears around 8k rpm so your next gear lands on your peak Torque at 7k rpm, then rev through your peak Power again etc.

[**Ghost**]

havent visitted my own thread for a while :)

DL001 is right u want to rev past 7600, perhaps to 7800 to land ur next gear shift into powerband

[**Ghost**]

Just to Clarify my own thread...

Redline has 3 meanings

1. as evan/proECu said, and i respect his opinion (and i'd give hm green cookie points if i knew how to) the factory ECU determines 8125 (see prev page) to be the time when ECU puts a stop to the fun before it gets completely outta hand

2. redline refers to the limit where ur engine internals are meant to be able to safely rev up to

3. redline refers to when ur tacho cluster is "red"

although all 3 are similar, i dont think they are necessarily the "same".... for ppl that tell u to rev up to the redline, i think that piece of advice is designed for #2 and #3, not so much as up to fuel cut as in #1

cheers

[Dxs]

Is this still up for debate? In my opinion, the redline is a number set by the manufacturer after determining the maximum RPM that the engine can operate at (minus some tolerance for safety) and the cams are chosen so that peak power is made just below that redline RPM.

Hence, you can build up engine's internals so that it can tolerate higher RPMs, then change the cams or use forced induction so that you make power at that higher RPM and use ECU management control to alter the redline to suit your needs.
:thumbsup:

redline is the max operating rpm set by the manufacturer, because it is what they believe u should stay under for reliability reasons. so if you exceed it will most likely cause engine damage, hence they even impose a fuel cut. Same reason redlines are set on built tuned engines.. because it is what the builder thinks the max revs should be for reliability. Plus i dont know where the name came from, probably using a gauge back in the old days of green yellow and red, and red always means max limit/trouble, hence a redline on the tacho.

but yeah, everyone i have mentioned has already been said

[mj3610]

Hey Wat About Carby Engines Where There Is No Ecu???

[redliner]

wat about cars that increase that redline? what mod would they have to increase the redline to like 9000, 10 000, even 11 000rpm?

[wynode]

:thumbsup:

redline is the max operating rpm set by the manufacturer, ....

Technically that is wrong.....and the max operating RPM will be that where the rev limiter is set to :)

[DLO01]

Hey Wat About Carby Engines Where There Is No Ecu???
There is no electronic rev limiter, fuel cut/spark cut. You could rev it as far a possible or until something lets go. All you have is your redline on your dial.

[Dxs]

Technically that is wrong.....and the max operating RPM will be that where the rev limiter is set to :)

yeah i know :p .. i guess i should have said max *recommended* operating rev limit.. seeming though the true engine cut rev limit is when fuel cut occurs. Or you could even say that the limit is almost undeterminable if u downshift at high speeds etc.

but really guys, as everyone knows.. the redline is just the set rev limit that the manufacturer imposes to ensure reliable daily use

[wynode]

but really guys, as everyone knows.. the redline is just the set rev limit that the manufacturer imposes to ensure reliable daily use

Hate to be pedantic but you got it wrong again :p

[cupnoodle]

Jesus :!: it all sounds so dangerous and bad for the engine. Thankfully, i'm easilly satisfied at the 4000rpm mark.

[**Ghost**]

thats cos u drive a cruisy comfy accord Euro :)

[h22a jdm]

how much does the spoon b18c rev up to

[wynode]

I think the initial question has been answered :)