Thứ Sáu, 10 tháng 2, 2017

Has anyone encountered a problem with the engine caused by hitting the rev limiter? part 1

MulletSlayer 08-10-2004 11:28 AM

Has anyone encountered a problem with the engine caused by hitting the rev limiter?
If this should be in the 2.0 forum please move it. I posted it here since it has to do with autocrossing.

At one region I run the majority of courses are extremely tight. Tight enough that I can run 50-80% of the course in first gear before I need to shift, but I hit the rev limiter maybe 1-2 times a run.

How damaging is it to hit the rev limiter (the most I'm up against it is for a second)? Should I start shifting to second early to avoid this, and just except loss in throttle response to lessen the stress on the engine?
KC 08-10-2004 11:32 AM

It's not damaging anything. The stock rev-limit is low enough so that nothing will happen if you hit it.

Look at it this way: it's there to protect the engine from damage. If you could damage the engine from hitting a certain RPM, the limiter would be set lower than that RPM.

--kC
jmott 08-10-2004 11:41 AM

[QUOTE=KC]It's not damaging anything. The stock rev-limit is low enough so that nothing will happen if you hit it.

Look at it this way: it's there to protect the engine from damage. If you could damage the engine from hitting a certain RPM, the limiter would be set lower than that RPM.

--kC[/QUOTE]

I actually have heard of cases of prolonged banging off the rev limiter causing problems. Weird vibration issues causing parts in the cylinder head to get out of whack. Probably not an issue for the brief stints at the rev limiter in an autocross.

You might want to shift into 2nd though and leave it there, work on being smooth and youll probably get quicker everywhere and actually make use of 2nd gear
MulletSlayer 08-10-2004 11:48 AM

Thanks, KC.

Thats what I was hoping to hear. I figured that I hit the rev limiter 20 times over the 14 runs this Saturday and Sunday and I was starting to worry.
trhoppe 08-10-2004 12:37 PM

[QUOTE=MulletSlayer]Thanks, KC.

Thats what I was hoping to hear. I figured that I hit the rev limiter 20 times over the 14 runs this Saturday and Sunday and I was starting to worry.[/QUOTE]
Not anything to worry about at all. 20 times in a row? that might be but 2x a run is NO big deal. I like the "rule" that anything over 8 times in a row should be a shift to 3rd next run :)

-Tom
MulletSlayer 08-10-2004 03:10 PM

[QUOTE=trhoppe] I like the "rule" that anything over 8 times in a row should be a shift to 3rd next run :)

-Tom[/QUOTE]

I'll remember that. :)
zzyzx 08-10-2004 04:03 PM

[QUOTE]
Has anyone encountered a problem with the engine caused by hitting the rev limiter?
[/QUOTE]

Yes, and a serious one at that. The car stops accelerating! :lol:
10th Warrior 08-10-2004 04:17 PM

[QUOTE=zzyzx]Yes, and a serious one at that. The car stops accelerating! :lol:[/QUOTE]
like you even know what its like to hit the limiter these days :furious: :p
skuttledude 08-10-2004 04:18 PM

[QUOTE=MulletSlayer]If this should be in the 2.0 forum please move it. I posted it here since it has to do with autocrossing.

At one region I run the majority of courses are extremely tight. Tight enough that I can run 50-80% of the course in first gear before I need to shift, but I hit the rev limiter maybe 1-2 times a run.

How damaging is it to hit the rev limiter (the most I'm up against it is for a second)? Should I start shifting to second early to avoid this, and just except loss in throttle response to lessen the stress on the engine?[/QUOTE]

Rev-limiter is your friend. Don't be afraid of it. It is there so you don't over-rev into the redline area. I nail it all the time in AutoX as well as lapping/HPDE weekends.
See this page for AutoX vids: [url]http://www.skuttle.com/sccaautocross.html[/url]

See this example of me nailing the 1st gear throught the turns and small straights. (turn volume up).
[url]http://skuttle.com/Lowes/Davis%20incar%20Lowe's.wmv[/url]

(right click save as..)

However one can say that you will get more engine wear at higher RPM's which is completely true. So its not a good idea to "live" on the rev-limiter either. Around town I really don't need to redline it as the STi has plenty of torque :banana:

Enjoy,

Davis
DrBiggly 08-10-2004 05:22 PM

[QUOTE=zzyzx]Yes, and a serious one at that. The car stops accelerating! :lol:[/QUOTE]
:lol: :lol:

I hit the rev-limiter without worry (although not quite as frequently as trhoppe.) Not a problem yet. :)
zzyzx 08-10-2004 05:25 PM

[QUOTE=10th Warrior]like you even know what its like to hit the limiter these days :furious: :p[/QUOTE]

:alien:

- Steve Sulatycki

P.S. You kicked arse PAX-wise out there at the Divisionals - awesome!
omahasubaru 08-10-2004 06:04 PM

Steve's rev limiter is super smooth... It's quite impressive how soft it can be set with the Link
Storm 08-10-2004 06:19 PM

FOKKER......


Jay Storm
[I]waiting for a unichip map to move that pesky revlimit up[/I]
WRX_Mundi 08-10-2004 08:32 PM

[QUOTE=Davis K Powers]See this example of me nailing the 1st gear throught the turns and small straights. (turn volume up).
[url]http://skuttle.com/Lowes/Davis%20incar%20Lowe's.wmv[/url][/QUOTE]All I hear is your blow off valve, which can't possibly be stock if it overwhelms your engine.

On topic though, yeah, rev limiter is OK. You'll use it at autocrosses a fair amount. A lot of people say a good rule of thumb is three hits on it means shift. I go by feel, and it depends on other curcumstances such as whether the shift down will happen in a hard braking zone (good) or in the middle of a turn (bad). I've gone through quite a few finishes just hitting the limiter where it isn't quite worth putting it into third. One nice thing is that the STi does have enough torque to make the decision a bit easier. The stock Evo I drove last weekend was just a [i]dog[/i] if you didn't keep the revs up, where my STi pulls really well down low.
skuttledude 08-10-2004 09:25 PM

[QUOTE=WRX_Mundi]All I hear is your blow off valve, which can't possibly be stock if it overwhelms your engine.

On topic though, yeah, rev limiter is OK. You'll use it at autocrosses a fair amount. A lot of people say a good rule of thumb is three hits on it means shift. I go by feel, and it depends on other curcumstances such as whether the shift down will happen in a hard braking zone (good) or in the middle of a turn (bad). I've gone through quite a few finishes just hitting the limiter where it isn't quite worth putting it into third. One nice thing is that the STi does have enough torque to make the decision a bit easier. The stock Evo I drove last weekend was just a [i]dog[/i] if you didn't keep the revs up, where my STi pulls really well down low.[/QUOTE]

Yea, the BOV was fun to listen to, but now its just too much. I was trying to say that you can hear the rev-limiter and the beep-beep of limiter by turning the volume up. Never mind the BOV.

Davis
jbrennen 08-10-2004 10:11 PM

[QUOTE=WRX_Mundi]The stock Evo I drove last weekend was just a [i]dog[/i] if you didn't keep the revs up...[/QUOTE]

[i]<slightly OT>[/i]

Which is why, IMHO, there are very few seriously campaigning an A Stock Evo.

Even my seriously augmented Evo has "issues" below 3500 RPM. :p
turboICE 08-10-2004 10:27 PM

I used to stay away from the rev-limiter but that was because the car wouldn't pull to the rev-limit. Now that I have it tuned and it keeps pulling to red-line there are few road courses I don't hit it a few times a day. Working on improving that though...

I must have hit it over a hundred times by now at the track, nothing wrong on my car.
ColinL 08-11-2004 12:39 AM

the Evo's revlimiter is pretty brutal... it seems to pimp-slap you a lot more than the rev limiter on my Impreza. 3 times would the very most on it before you're loosing major time IMO.

btw, didn't know you frequented here jbrennen. hi!
turboICE 08-11-2004 06:55 AM

I am definitely losing time by hitting it, I would rather not hit it. I just need get more accustomed to the gearing or better yet a higher red line.
KC 08-11-2004 07:40 AM

What I don't get is... why are you even coming close to red-line? Boost and HP fall off a bit before redline. IMHO, you're slowing down closer to the top you get... and there's nothing the right foot can do to get the car to go any faster once you exceed the HP/boost limits... especially in 1st gear.

Also, at the top of 1st gear, the car will get upset much more easily (some say this is a good thing) that a novice driver will then think the car is either a handful to control or 'sucks'. Thingws happen very quickly in 1st gear... and you should be ready for them, even if you're going slow, 2nd gear 95% of the time on an auto-x, is the one to be in, even if you're a tad off boost. Just takes time to learn when you need to feed in the go-pedal. sometimes, 1/4 of the way through the turn... by the time you're pointing straight after the apex, boost might be there waiting for ya. :)

You could also try shifting sooner at around 5500-6000rpm (admitedly it takes time to do this also), but then the RPMs on a WRX will be right where the boost starts kicking in again in 2nd gear.

--kC
skuttledude 08-11-2004 09:26 AM

[QUOTE=KC]What I don't get is... why are you even coming close to red-line? Boost and HP fall off a bit before redline. IMHO, you're slowing down closer to the top you get... and there's nothing the right foot can do to get the car to go any faster once you exceed the HP/boost limits... especially in 1st gear.

Also, at the top of 1st gear, the car will get upset much more easily (some say this is a good thing) that a novice driver will then think the car is either a handful to control or 'sucks'. Thingws happen very quickly in 1st gear... and you should be ready for them, even if you're going slow, 2nd gear 95% of the time on an auto-x, is the one to be in, even if you're a tad off boost. Just takes time to learn when you need to feed in the go-pedal. sometimes, 1/4 of the way through the turn... by the time you're pointing straight after the apex, boost might be there waiting for ya. :)

You could also try shifting sooner at around 5500-6000rpm (admitedly it takes time to do this also), but then the RPMs on a WRX will be right where the boost starts kicking in again in 2nd gear.

--kC[/QUOTE]

Great advice! Very interesting. I'll try that out this Sunday.
P.S.: KC, I'll send you the vids this weekend.
WRX_Mundi 08-11-2004 10:42 AM

[QUOTE=KC]What I don't get is...[/quote]Let me start by saying the talent posting on this forum is very impressive, and I'm posting both to explain what I do, and to learn from the guys like jbrennan and KC who are quite a bit better.

[quote]Also, at the top of 1st gear, the car will get upset much more easily [...][/quote]I actually had written something about this in my post but then decided it wasn't relevant enough the way I had written it. I have been taught and agree that on some fast slaloms and the like, the car is usually much smoother if you take it up a gear -- I'm talking about when the car is in 2nd or 3rd and you're at 6000 rpm. So not even redline, but it does settle things down. At the Wendover Pro the back section was, for me, between 50-60 mph, and my 2nd tops out at 55mph, hence I drove it in third gear. On one run I had brain fade and forgot to shift to third, and when I got to the fast gates I was wondering why the car was so un-smooth. When the rev-limiter hit once I did a big "d'oh!" but by then it was too late.

Regarding 1st, I'll agree completely. First gear has [i]so[/i] much torque that I find it very difficult to drive at an autocross. Generally I'm using it to get through a very tight section or around a 135+ degree pivot cone, and I'm not running it to rev-limiter. The tight section had better be very tight, and there are a lot of courses I've driven that are 1st at the start, shift to second, then stay for the whole course. I had a novice autoxer in a modded WRX ask me at one course what gear I was using. I said 2nd -- he said he was using 1st for the whole course, which just blew me away (note he was 7 seconds behind on a 40 second course). I'll agree that a lot of people would be surprised how tight of stuff you can drive while leaving it in second and using early but correct throttle movements combined with good lines. From what I've heard I'd probably be surprised by KC's driving too. :)

[quote]why are you even coming close to red-line? Boost and HP fall off a bit before redline. IMHO, you're slowing down closer to the top you get... and there's nothing the right foot can do to get the car to go any faster once you exceed the HP/boost limits... especially in 1st gear.[/quote]Here are a couple times I've done it, thinking at the time it was the right thing to do. Course starts through a set of offset slaloms to the right, car has been shifted into second. We do a hard left onto a fairly long straight which leads into a pretty fast sweeper left. For my driving ability and car, 55mph is rev limiter in second, the sweeper can be driven at, say, 45mph and the rest of the course is all second gear. When I drove it, I'd hit rev limiter right before I did a dab of brakes then started turn-in. For me this worked -- I tried going into third once, but this completely destroyed my turn -- there was no good braking area that offered time enough to shift back to second and the car was really unbalanced. A better driver could do it, but I could not. Top PAX by 1 second over 2nd place that day (obviously regionally dependent). Here's [URL=http://www.jacobsensation.com/dana/Autox_2004_05_22.mpg]video[/URL] if you want to see.

Finishes are the other time I have hit rev-limiter. I know there are a lot of times I'm also going through a debate with myself about whether to shift or not. This is of course almost always a stay in second or shift to third debate. There was one autocross I attended in Bend, OR where they wall off the finish area, forcing you to stop in an insanely small box. Most of the prepared cars would smoke their slicks, and a lot of people hit their brakes before the finish lights just to ensure they could stop. I'd come across at rev-limiter -- shifting to third would mean a tad more speed but it all had to go away with a semi-panic brake and a prayer anyway. OK, so that was a special case, but there have been quite a few normal finishes where it is just a last straight shot to the lights and I hit rev limiter a couple times before I cross them. I haven't seen any advantage for me on these of shifting to third unless I'm on it more than a couple times. But I'm willing to believe I'm doing something wrong.

Now if I just had that nice Motec ADL and a laptop to churn through all the data afterwards and get hard numbers on what was fastest for me... Oh, and those fender flares to accomodate the V710s, and the Motec ECU for traction and launch control, and those pretty Motons, and ... :)
jbrennen 08-11-2004 01:46 PM

[QUOTE=WRX_Mundi]...and to learn from the guys like jbrennan and KC who are quite a bit better.[/QUOTE]

Thanks for putting me in the same sentence with KC, but I suspect that he would hand me my own ass if he drove my car. :lol:

I seem to have some talent for driving fast around cones, but I'm no championship contender -- unlike some of the other guys who hang out here.
KC 08-11-2004 01:57 PM

What? I'm just someone who got lucky last year. I wasn't picked to win this year... I'm just one of them 'He's got a shot' guys in SportsCar. :lol:

--kC
trhoppe 08-11-2004 02:15 PM

Shiiiit. Youre a "remote" shot this year. You're not even a "contender" thats for those guys in the 325s ;) :lol:

-Tom
WRXedUSA 08-11-2004 09:28 PM

[QUOTE=KC]What I don't get is... why are you even coming close to red-line? Boost and HP fall off a bit before redline. IMHO, you're slowing down closer to the top you get... and there's nothing the right foot can do to get the car to go any faster once you exceed the HP/boost limits... especially in 1st gear.



You could also try shifting sooner at around 5500-6000rpm (admitedly it takes time to do this also), but then the RPMs on a WRX will be right where the boost starts kicking in again in 2nd gear.

--kC[/QUOTE]

I argue this point day in day out. I'm glad someone else views it my way.

:banana:

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