E85: knock count on spoolup and load spikes
#1
E85: knock count on spoolup and load spikes
Hey guys,
I've been having this issue while tuning my car on e85. From spool-up to peak torque I have a single count of knock even with very very conservative tuning. It's gotten to the point where I've dialed everything between 2500-5000 back to 0 degrees of advance just to see if it's a timing issue. The load seems to be pretty high for such a low level of boost, where there is knock. Car is a IX MR w/ stock turbo. I've attached a snapshot of my log from 2000-3500rpm. I was thinking maybe boost leak, but the car tests just fine. I'm all out of ideas.
Mods are as follows:
TBE exhaust, catless, Titek v2 o2 housing
non-CDI COP kit
Forge adjustable WGA
GM 3port BCS
Synchronic BOV
Kelford 272
Supertech valvetrain
Nisei LICP
T-bolt clamps all around
New TB shaft seals
FIC 1350cc injectors
Walbro 255lph
Omni 4bar map sensor
Tephra v5 and direct boost control
I've been having this issue while tuning my car on e85. From spool-up to peak torque I have a single count of knock even with very very conservative tuning. It's gotten to the point where I've dialed everything between 2500-5000 back to 0 degrees of advance just to see if it's a timing issue. The load seems to be pretty high for such a low level of boost, where there is knock. Car is a IX MR w/ stock turbo. I've attached a snapshot of my log from 2000-3500rpm. I was thinking maybe boost leak, but the car tests just fine. I'm all out of ideas.
Mods are as follows:
TBE exhaust, catless, Titek v2 o2 housing
non-CDI COP kit
Forge adjustable WGA
GM 3port BCS
Synchronic BOV
Kelford 272
Supertech valvetrain
Nisei LICP
T-bolt clamps all around
New TB shaft seals
FIC 1350cc injectors
Walbro 255lph
Omni 4bar map sensor
Tephra v5 and direct boost control
#2
Evolved Member
iTrader: (7)
Join Date: Feb 2007
Location: MoTown,GA
Posts: 574
Likes: 0
Received 0 Likes
on
0 Posts
I dont see anything wrong with that. even with e85 the knock sensor is going to pick up engine noise. 1 or 2 counts is not really knock. IMO you need a good bit more timing. i see a bunch of 0's where you should probably have at least 3-4.
#3
I dialed the timing down to 0 because w/ 3-4 degrees of timing I was getting knock, so I wanted to see if it would still happen with less timing. W/ 3-4 degress of timing the 1 count is more consistent throughout spoolup (happening at almost every data point from 2500-4000)
#6
Evolved Member
iTrader: (48)
I'm guessing it's most likely valvetrain noise that you're picking up; you've pretty much ruled out that it's real detonation by running low timing. If it were my car I would go back to running normal timing advance and adjust the knock filters to reduce the chance of picking up false knock.
Trending Topics
#8
Evolved Member
iTrader: (3)
What happens to your knock count if you add timing one degree at a time to those areas that are now -1 degree?
You should not need negative timing. I'm running 6 degrees at peak and 24 degrees out the top at 20psi on E85 with no knock.
If you can add timing and the knock count stays the same (meaning 1 count or less), then it's not really knock. Then, I'd agree it is likely valve train noise.
You should not need negative timing. I'm running 6 degrees at peak and 24 degrees out the top at 20psi on E85 with no knock.
If you can add timing and the knock count stays the same (meaning 1 count or less), then it's not really knock. Then, I'd agree it is likely valve train noise.
#9
I posted a log from last night. With a little more aggressive timing, I was still getting a random 1, and occasional 2 count. I did notice that when the car "knocks" it feels like it's hesitating. Is that a result of the ecu seeing the "knock" and pulling timing? You'll notice that where there's knock, the timing advance drops.
Last edited by RJones; Mar 11, 2011 at 02:14 PM.
#11
Former Sponsor
iTrader: (22)
can you rev the car in neutral and produce knocksum in the troublesome areas?
be careful when tuning with e85 man.. its not like regular octane fuels. you cant tune it based on just knocksum.. you must monitor each degree you add to the car with virtual dyno and confirm its making the same hp/tq increment per degree added.. you can easily give a car to much timing on e85 with zero knocksum. be aware AFR plays a huge roll when MBT is hit or missed as well.
be careful when tuning with e85 man.. its not like regular octane fuels. you cant tune it based on just knocksum.. you must monitor each degree you add to the car with virtual dyno and confirm its making the same hp/tq increment per degree added.. you can easily give a car to much timing on e85 with zero knocksum. be aware AFR plays a huge roll when MBT is hit or missed as well.
Thread
Thread Starter
Forum
Replies
Last Post
EvilDSM97
ECU Flash
3
Aug 29, 2022 09:02 AM
03GS-T
ECU Flash
5
Jun 15, 2016 01:21 PM
krillin
ECU Flash
15
Feb 6, 2007 10:01 AM