Knock On Limiter

[Granthem]

Hi Guys,

Ok so I did a search and noticed alot of threads on knock as you would expect, but my question is slightly different to the others.

My car when on limiter will flash the check engine light. Now before you say "well dont bash limiter like a dick", I'm talking first gear, coming on hard and lighting up the rears straight away, the car races to limiter and still has alot of first gear left to wind out.

The car NEVER knocks when just under load (I say this because the check engine light doesnt flash, however I do not have a hand controller with my PFC to get a figure)

I am assuming the sensor is picking up multiple other noises that occur when on limiter, as everyone knows the noises when bashing limiter are plenty.

Car is a S2 R33 GTS-t making 350rwhp on a HKS GT-RS. 15-16psi

A/F's on the dyno were 10.5ish and the car is tuned my Marc Jacobsen of Godzilla Motorsport.

I guess my question is does anyone else has a "safe as houses tune" that shows signs of knock on limiter. I'm planning to take it to the strip over the next two weeks and want to make sure that all will be fine. Obviously launching it its going to bounce limiter abit...

So from personal experience, has anyone else with a nice "safe" tune show signs of knock when on limiter?

Edited November 2, 2009 by Granthem

[DRD-00F]

I get very high knock at the top of third on very cold nights... Unlike you, I'm CERTAIN it's knock cause it reads Knk: 140 !!!

There are 3 reasons your engine light will flash:

1. Knock above 60 (I think it was 60)

2. Maxing out the injectors

3. Maxing out the AFM

Most tuners will turn 2 and 3 off if they are sure that they won't be causing a problem for you. What injectors and what AFM are you running?

Also, you should really invest in a hand controller, they can show you an amazing amount of information!

[Granthem]

I know I know... a hand controller is on the cards!

As for AFM - Z32

Injectors - Nismo 550's

Thats the problem, I dont really know the "figure" its knocking too, however I'm assuming if its not showing the knock warnings under load during the revs, I'm thinking the sensor is picking up another noise when on limiter, as least thats what I'm hoping

[DRD-00F]

The chances of that happening are very very rare. I wouldn't bank on that.

Your AFM and injectors should be fine, so I dare say that it's knock. Most of the time knock will happen at or near the limiter, not just on load.

Sounds to me like a simple case of knock. Was the car tuned in winter? The ambient air temp is raising dramatically at the moment, so any 'super safe tune' done in winter would find itself out of the water in summer.

[skylinecouple]

Take it back to Godzilla, if it is knocking then I'm sure he would not want to know he destroyed your engine.

[Granthem]

Take it back to Godzilla, if it is knocking then I'm sure he would not want to know he destroyed your engine.

Yeh the problem is its 8 hours away...

Stupid Rockhampton!

[joeyjoejoejuniorshabadoo]

i have my check engine light set at 40 knock and i have never seen it come on, even when abusing the limiter drifting.

i'd be getting it checked if it was mine

[Granthem]

i have my check engine light set at 40 knock and i have never seen it come on, even when abusing the limiter drifting.

i'd be getting it checked if it was mine

Hmmmmm interesting. Thanks for that. OK no limiter bashing for me! Time to tip toe around

[Guilt-Toy]

knocking when the engine is smashing the rev limiter is completly normal. every car is different - knock sensors are in different condition and engine makes different noises to other engines.

with my car it would knock badly on the rev limiter when i had the power fc. other engines don't.

i would not worry about it. That goes for you too Dr Doof. if its knock when your hitting the limiter then forget it

if it knocks before the rev limiter cuts in then you should worry. think about it.. all hell is happening in the cyl's when the rev limiter is working... what do you expect it to do? sing a lilaby ?

and also the engines are more prone to knock when its at MBT. so with your turbo that would be around 3500rpm. Call Marc and he will explain it to you

[Cjmartz2k]

Jeez, your tuned for 10.5:1 AFR's at WOT??

[Granthem]

knocking when the engine is smashing the rev limiter is completly normal. every car is different - knock sensors are in different condition and engine makes different noises to other engines.

with my car it would knock badly on the rev limiter when i had the power fc. other engines don't.

i would not worry about it. That goes for you too Dr Doof. if its knock when your hitting the limiter then forget it

if it knocks before the rev limiter cuts in then you should worry. think about it.. all hell is happening in the cyl's when the rev limiter is working... what do you expect it to do? sing a lilaby ?

Lol this is what I was thinking. I mean there are a number of bangs, explosions and noises when bouncing limiter. I assumed if the car was truely knocking it would be showing signs of it during the rev range like you have said. I am of the believe it is registering another noise, and not true knock.

And it does sing a lullaby... a nice RB limiter lullaby

[Guilt-Toy]

Lol this is what I was thinking. I mean there are a number of bangs, explosions and noises when bouncing limiter. I assumed if the car was truely knocking it would be showing signs of it during the rev range like you have said. I am of the believe it is registering another noise, and not true knock.

And it does sing a lullaby... a nice RB limiter lullaby

hahhahaa! your tune is fine. they don't call him Godzilla for nothing

I used to let go of the throttle a little when its about to hit limiter, wheels are spinning anyway so its only going to make the limiter bash a little less savage and after you practice this for a while you will get better and better and the engine light will stop flashing all together.

[Granthem]

hahhahaa! your tune is fine. they don't call him Godzilla for nothing

I used to let go of the throttle a little when its about to hit limiter, wheels are spinning anyway so its only going to make the limiter bash a little less savage and after you practice this for a while you will get better and better and the engine light will stop flashing all together.

Yeh you are correct I'll have to practice my throttle control to minimise it. I have never owned a car with a lightened flywheel before, and I must say I've noticed a difference. The thing revs crazy quick.

[Granthem]

Jeez, your tuned for 10.5:1 AFR's at WOT??

Thats what it ran on the dyno up here yup. They said there is plenty of power hiding in it.

Lets just say there is enough fuel to create "small" (very large ) flame shows...

[r33cruiser]

Well....when i got mine tuned at matty's, he said not to worry about the limiter, its normal.

BUT, your problem has only happened to me a couple of times. So i changed the spark plugs (1 was shattered) and it didnt do it anymore. Even banging on limiter i dont get the check engine light, unless I have the pedal to the floor, still banging on the limiter.

Maybe put in a new set of spark plugs, and try again?

[JonnoHR31]

if your really worried about it you can take a degree or 2 of timing out around limiter (borrow someones hand controller if you dont have one). limiter is hardly a place where you need more power anyway. but as said every cars different, i get some pretty crazy knock readings on limiter, she be right

[Beer Baron]

borrow a hand controller and you will be instantly be able to see what's happening. it could be your injectors hitting 100% duty at that point, or the AFM peaking at 5.115v or it could be knock. borrow or buy a HC and you will KNOW what it is and even better you can do something about it if need be.

[Granthem]

borrow a hand controller and you will be instantly be able to see what's happening. it could be your injectors hitting 100% duty at that point, or the AFM peaking at 5.115v or it could be knock. borrow or buy a HC and you will KNOW what it is and even better you can do something about it if need be.

Yeh i have a WTB add posted up, hopefully someone has one i can snap up.

Injectors are 550's and therefore shouldnt be near 100% i wouldnt think... same goes for the Z32 AFM.

But i will definitely do my best to source a handcontroller and see whats going on

[ECR-033]

i just had my 33 tuned last week, no knock above 30 until tonight..... i decided to put my foot down in 2nd (didnt reach the limiter) the knock was going ape sh!t and hit 98 so i did the same again to see if it was a 1 off, but it went to 60. i was stressing out a bit so i left it sitting for a while. just came back from a drive putting my foot in 2nd through 3rd and it only went to 30..... im hoping it was just the warm weather causing it to rise.....

[ZOKU]

I think your motor knocks bcause of rev-limit lean out. the Power FC (like stock ECU) cuts fuel as a rev limiter, opposite to the desired way to cut spark to stop combustion. this is the way I understand it ( drunk blurb ), You can get knock couple of ways, and possibly others but lean fuel mix and hot combustion would do it. knock on the limiter is bad but it's not as bad as knock under load cos it's duration is longer.

stay off the limiter or diy and upgrade fuelpump and fix the voltage on the fuelpump wiring. making the fuel richer all round might make the car feel sluggish tho.

Octine booster off the shelf didn't seem to work until I put some NF race octine booster (6 ron). It reduced the knock level on PFC, from 74 to high 20's. and even after hitting the limiter at 7700. handset is good for recalling all readings too.

Im curious to find out the limit of stock RB series motors. I think it's related to hitting the limiter and leaning out. I thought the upper limit was at 100 on the screen, but someone on early reply got 140! The motor makes most power at... it's best cam timing and leanest fuel ratio. it's probly case by case and a matter of opinion how much before motors usually pop and associated knock reading.

I like knowing the RB20 handles being on the limiter better than other RBs when running with PFC.

when my car knocked at level 74, stock internal 20 with 84c water temp no oil cooler and 300whp at 20psi boost. so smaller knock reading on the limiter might be ok as long as it's resonable rev for the motor.

thats my 2cents