Knock retard...how to solve?

A

AutoEuphoria

Member
:
'08 CPW Mazdaspeed 3
I was at the track this weekend, and every run I started getting knock retard near the end (fourth gear, mostly). Just trying to figure out what (if anything) I can do to get rid of it for next time? I was using BP 93 octane...mods are:

- catless dp/tp
- cai
- cdfp internals
- 1 step colder plugs
- boost tubes
- rkm bpv
- MAP clamp
- MBC set to 17psi
 
Getting rid of knock in this car does not seem possible. I saw 7.0 for a second on my way home from work today. Son of a b****!

I think the latest trend is to get the Cobb AP with the ATR software and pull timing in the knock retard trouble spots of your rpm band. Not that I know how to do any of that.
 
how about unplugging the knock sensor wherever it is. i had an old zetec ford zx2 that would KR just because of all the engine noise and vibration. it was proven that unplugging the sensor would smooth out the power band significantly if you didnt have a tuner that shut it off automaticaly, it didnt even throw a CEL with this done. but a zx2 is a far cry from our speed3s for sure.
 
GoSpeed3 said:
how about unplugging the knock sensor wherever it is. i had an old zetec ford zx2 that would KR just because of all the engine noise and vibration. it was proven that unplugging the sensor would smooth out the power band significantly if you didnt have a tuner that shut it off automaticaly, it didnt even throw a CEL with this done. but a zx2 is a far cry from our speed3s for sure.
Click to expand...

I wouldn't reccomend that course of action. The best way to get rid of knock is to Run 100% meth
 
DaleNixon said:
^ My knock all happens at cruise in vacuum. Wouldn't you only spray meth in boost?
Click to expand...

really...I've never had any knock while cruising. If your just cruising, your AFR's should be around 14.3-16 and from what I know about motors, thats healthy. I am aware that any pursistant knock under heavy load (under 3000 PRM in high gears) is the actual killer.
 
Yeah, I get KR just cruising around, also. It's weird. I don't mind that much, but when I'm racing it's a different story.
 
mr_mazda329 said:
really...I've never had any knock while cruising. If your just cruising, your AFR's should be around 14.3-16 and from what I know about motors, thats healthy. I am aware that any pursistant knock under heavy load (under 3000 PRM in high gears) is the actual killer.
Click to expand...

I get it with a stoich ratio. I never load it up hard below 3k in high gears. Cobb says the cruise knock is normal as the car is just attempting to find the best timing for fuel economy/performance by advancing timing to the point of knock then backing off.

Then there are those who believe cumulative cruise knock will eventually kill your motor. I just have fun with the car, treat it as well as I can, and hope for the best!
 
Darth Vader said:
No Jack but, where is the KS on this car?
Click to expand...

It is hidden behind the intAke manifold. This sensor is easy to damage according to the Mazda shop manual so don't drop it if you take it out. Also be sure to follow torque specs or it will not work properly. Me and my buddy Scott have tried just about everything to get rid of KR. Starting to think its not possible.
 
From everything I've read, the only reliable way for a Speed3 owner to get rid of all knock retard is to replace with another vehicle.

Like several here, I get KR all the time while cruising, especially when I let OFF the gas in 4th-6th gears. As stated previously, I figure this must be the ECU playing with that durned variable valve timing & AFR's while searching for the most eco-friendly solution.

Haven't seen KR pop up under acceleration, but I'm practically stock aside from a Cobb SRI & Forge BPV.
 
billthecat said:
from everything i've read, the only reliable way for a speed3 owner to get rid of all knock retard is to replace with another vehicle.

Like several here, i get kr all the time while cruising, especially when i let off the gas in 4th-6th gears. As stated previously, i figure this must be the ecu playing with that durned variable valve timing & afr's while searching for the most eco-friendly solution.

Haven't seen kr pop up under acceleration, but i'm practically stock aside from a cobb sri & forge bpv.
Click to expand...

+1
 
KR during cruise is not from REAL knock. It's the ECU adjusting timing. If you get it mashing on the gas at tip in and any time after that, it's real and should be tuned out by adding fuel/decreasing timing in those areas with the AP. A colder set of plugs 'may' help, but I wouldn't count on it. Occassional WOT KR <1.0 that can't be consistently replicated shouldn't be obscessed over. If you're seeing it consistantly and it's up over 1.0, I'd be working on tuning it out.
 
The problem I am having is at tip in. Seems much more prevalent when it's hot outside. I have a fmic, step colder plugs, have replace the injector seals a couple of times and cannot for the life of me figure out why it wil not go away. We moved the crank position sensor a little and that reduced the cruising KR. Going to re-time the car tomorrow to see if that helps. The seas in there now are custom so we will check on them to see how they're holding up. Have tried octane booster, upgraded catch cans, thought maybe oil might be lowering the octane rating. I'm built now so I also wonder if thr forged internal have anything to do with this? More noise and the knock sensor is picking up the noise? Seems to be between shifts 2800 - 3300 rpms if I go maybe 25% throttle and 5-10 boost. So maybe it's time to put the standback back on. I dunno out of ideas. Anyone have any let me know
 
Last edited:
Please log in or register to reply here.

Similar threads

A
Please take a look at this log
Replies
3
Views
1K
ReNaToMS3
R
J
Knock Retard at WOT..
Replies
13
Views
12K
FrequentFlyer
F
A
Tune and exhaust...opinions needed
Replies
8
Views
2K
ms3brendan
M

Latest posts

Back