NewCelica.org Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #1 ·
With every engine, there is always spots where knock is likely to happen. Usually, it can be tuned easily. With my piper cam stage 2, I found a small knock around 6k rpm (43-45 value which is higher than my typical reading of 39-41 at WOT). It happens on the second cam under low throttle while accelerating. I have 10k km with the engine and cams already and it's been there from the beginning. I don't know if it's real knock but I am wondering. Under more load, no problem there. Same goes under constant driving. Since one rarely rev on low throttle input at 6k, it is a minor issue. I typically leave O2 feedback on so my regular A/F is in the high 14s with low load.

I am not expecting to find the miracle cure from this thread, I have tried a lot of things. I have a bit of experience tuning my car so please, avoid the typical answer "lower the timing" and/or "enriches your mixture". I have tried low timing, richer mixture and would not be posting here if it had helped it. It seems to have no effect. Besides, low load should not need extremely low timing values or rich mixtures.

Those cams work like a charm for me. But, I am just wondering if you guys have similar observations with piper cams and if you found anything that helps it. Do you think this is real knock ?

Feel free to post your own observations / problems / solutions regarding tuning with the piper cams in this post. There is not much discussions about the tuning of piper cams and I believe it could be interesting for the community .. Those cams make for a whole different engine, that's for sure!
 

·
Premium Member
Joined
·
18,200 Posts
Have you tried retarding the cam at low load? I know you set up your VVT map differently on the high cam for shifting purposes. I'm assuming that at 6000 rpm, you have the cam pretty advanced. Even if you don't leave it this way, retard the cam all the way at low load and see if the knock goes away. If it does, slowly bring the cam timing back in until you see knock again.
 

·
Bring on the 12's...
Joined
·
6,107 Posts
Dan, did you use power fc with this set up when you still had the stock injectors? How quickly do they max out when you start tuning for power at WOT?
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #4 ·
Have you tried retarding the cam at low load? I know you set up your VVT map differently on the high cam for shifting purposes. I'm assuming that at 6000 rpm, you have the cam pretty advanced. Even if you don't leave it this way, retard the cam all the way at low load and see if the knock goes away. If it does, slowly bring the cam timing back in until you see knock again.
Good idea. I'll give it a shot ... Thanx!

However, I believe I had the same issue when my cam vvt was locked at 55 all the time. Maybe I did not try with lower timing back then, I can't remember .. So, lower timing + retard vvt might be the solution I have not tried yet.
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #5 ·
Dan, did you use power fc with this set up when you still had the stock injectors? How quickly do they max out when you start tuning for power at WOT?
I have run PFC for more than 9.5k km out of the 10k km I have with the engine. I barely used the stock ecu at the beginning. Most of the time with this engine, i had the yellow injectors. But I unlocked my vvt only in last June. Which unlocked a lot of potential of course. So, I used the PFC with unlocked vvt and yellow injectors for about two months.

Maxing the injector depends a lot on your a/f ratio. I had to put my a/f leaner than I wanted at 8k rpms +. Even then, I was at 96-97% injection duty around 8.5k. The thing was sensitive to temp. On fresher days, I was maxing them (~96-97%) around 7k. On my car, it looks like the injection duty increases only slightly between 7k and 8.5k with a constant A/F ratio. With that kind of inj duty, you can't floor it agressively from 7k+ without maxing the injectors .. You either punch it before or press the gas slower ..

I believe Many was able to tune his with safer injection duty with his yellow injectors. I think the main difference is the intake but I dunno for sure .. I have injen. He has AEM.

I have noticed my air flow stays constant at high rpms with the newer injectors. It was falling with the yellow injectors. I guess they were not efficient anymore at that high inj duty ..
 

·
Registered
Joined
·
11,169 Posts
On a related note, or you sure it's actually pinging? That value may or may not correspond with actual knock, especially if you've had work done to the motor. The resonance that reflects actual knock might be a bit different now.

If it is definitely knock, then as Jesse said, try playiing with VVT settings. You might try dialing in a little more overlap at 6K to reduce cyllinder pressure :shrugs:
 

·
Bring on the 12's...
Joined
·
6,107 Posts
Maxing the injector depends a lot on your a/f ratio. I had to put my a/f leaner than I wanted at 8k rpms +. Even then, I was at 96-97% injection duty around 8.5k. The thing was sensitive to temp. On fresher days, I was maxing them (~96-97%) around 7k. On my car, it looks like the injection duty increases only slightly between 7k and 8.5k with a constant A/F ratio. With that kind of inj duty, you can't floor it agressively from 7k+ without maxing the injectors .. You either punch it before or press the gas slower ...
wow, that 96~97% falls as low as 1500rpm on colder days?? It's reasons like this that scare me from sticking in the power fc as I wont be able to use the hunduh tuning method of running it pig rich to mask over initial tuning errors :gap:

off topic:
mine is very sensitive to temp also on the stock ecu. on the pretty cold mornings we've been having here in London, the car needs a firm blast of the throttle to get it moving or else it'll bog like hell.

I'm also getting the occasional misfire on acceleration when the engine is warmed up. I avoid doing sudden full throttle slams, but even if I floor it to just beyond half throttle sometimes, i'll be able to hear the slightest amount of knock.

on topic:
many was kind enough to share his recent map with me and i've also got one from redliner9k. interesting lift points as one is below 6k and the other is nearing 7k...lol, this means that the small cam on piper's are able to outperform the big lobe on the stock cam??

dan, where are you hitting lift at on your set up? which method did you use for deciding on your switchover point?
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #9 ·
I was actually only talking about cam timing, not ignition timing. Try first with your existing ignition settings and fully retarded cam.
Yeah I will .. I understood you. It's just that I believe I had the same problem when my VVT was at the total opposite .. So I will try to play with timing too along with the vvt ..
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #10 ·
On a related note, or you sure it's actually pinging? That value may or may not correspond with actual knock, especially if you've had work done to the motor.
That's what I was thinking too .. I never heard audible knock at that rpm but the engine is pretty noisy at 6k and a real knock might be hard to hear at higher rev, especially since we are not talking of a sky high knock reading ..
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #11 ·
wow, that 96~97% falls as low as 1500rpm on colder days?? It's reasons like this that scare me from sticking in the power fc as I wont be able to use the hunduh tuning method of running it pig rich to mask over initial tuning errors :gap:

off topic:
mine is very sensitive to temp also on the stock ecu. on the pretty cold mornings we've been having here in London, the car needs a firm blast of the throttle to get it moving or else it'll bog like hell.

I'm also getting the occasional misfire on acceleration when the engine is warmed up. I avoid doing sudden full throttle slams, but even if I floor it to just beyond half throttle sometimes, i'll be able to hear the slightest amount of knock.

on topic:
many was kind enough to share his recent map with me and i've also got one from redliner9k. interesting lift points as one is below 6k and the other is nearing 7k...lol, this means that the small cam on piper's are able to outperform the big lobe on the stock cam??

dan, where are you hitting lift at on your set up? which method did you use for deciding on your switchover point?
We are talking of 3-5% of difference in inj duty between 7k and 8.5 k on my car (on the top of my head). So, if temp can impact you inj duty by 2-4 %, it will make that much of difference in rpm injector maxing point! Of course temp correction factor were also playing in the equation ..

From what you say, it sounds like the AF the stock ecu is giving you is off ..that would create bug. But then, VVT has also an impact ..

As for my switchover, to help you decide, I am right in between, at 6k! lol! It's not dyno tuned yet. I might find another outcome on the dyno but I would be surprised to find something way different. I would be surprised too to see the big cam efficient below 6k but I have ran only a lil bit the big lobe below 6k. So I can't know for sure right now. I did all my vvt tuning with air flow on the street with my lift set at 6k. I have tried at first every vvt by step of 10. The highest mv value on the small lobe with the best vvt was at the exact same level as the highest value with the best vvt on the big cam. So I left it there and fine tune the VVT. My fine adjustments still make a very smooth transition of mv at 6k. It's like if there would be no transition. Same feel on the street at high load. Then, after hearing from Many's dynos, I have tried it at 6.5 k with the best VVT that I could find with my earlier vvt testings. It was really close. My conclusion is that both cams run very close air flow between 6k and 6.5k with their own optimised vvt on my car. remember there is not an important lift difference between both lobes compare to the stock cams. I prefer lower lift cause I wont fall out of lift as often which avoid excessive stress ..

But, that is on my car. Given the historic of dynos of my car and Many's car including his recent dynos, his car likes a higher switchover than mine. That was the case before the cams too. It probably has to do with the different intake/header. It looks like 6k lift like me would be too low for Many's car ..

I am planning on trying a lower switchover point cause I don't like the torque dip some dynos show with the piper cams between 5k and 6k. We'll see if I can find something on the streets.. Maybe redliner can bring his inputs in this department ..

I really need to go on the dyno cause at the point of street tune I am right now, I need something more precise ..
 

·
Premium Member
Joined
·
18,200 Posts
But, that is on my car. Given the historic of dynos of my car and Many's car including his recent dynos, his car likes a higher switchover than mine. That was the case before the cams too. It probably has to do with the different intake/header. It looks like 6k lift like me would be too low for Many's car ..
I tried street tuning with MAFS voltage on Smaay's car, then found on the dyno that the actual power curve didn't follow the MAFS voltage curve. In other words I wouldn't put a whole lot of stock in that.
 

·
Registered
Joined
·
3,732 Posts
Discussion Starter · #13 ·
I tried street tuning with MAFS voltage on Smaay's car, then found on the dyno that the actual power curve didn't follow the MAFS voltage curve. In other words I wouldn't put a whole lot of stock in that.
Yeah, Many told me about it. That's weird! It's kinda saying more air = less HP. Other than a lack of precision of air flow tuning, I can't explain what happened to you. Do you think it has to do with the turbo ? Were you running at same boost ?
 
1 - 13 of 13 Posts
Top