Knock during spool/load up
Nov 16, 2010, 03:58 PM
#46
Evolved Member
iTrader: (20)
Join Date: May 2007
Location: houston
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
im surprised other E85 tuners havent posted about this... People that are familiar w/ tuning on E85 will tell you its not very knock resistant at low to mid rpm on the evo. In fact, in some cases it seems more sensitive to knock than 93 octane. In my experience, it seems the properties in E85 that allow it to behave like a higher octane fuel doesnt surface until the fuel is exposed to higher VE. You'll notice at lets say above 6krpm you can add timing like crazy w/out knock, similar to that of C16. But if you add more than pumpgas timing down low you will knock, or have inconsistent pulls. Its about how you ramp the timing up if anything. You just can't be aggressive down low like you can w/ leaded racegas... but you can ramp up aggressively to meet those same peak timing #s after a certain rpm. Just my two cents...
-Tom
-Tom
Dec 1, 2010, 10:06 PM
#47
okay, you guys seem like the perfect guys to ask about my problem....
my car knocks when I do a pull and start from 2k-4k in 1st-4th. if I start at anything higher than 4-4.5k, i get 0 knock. Also, if I start the pull from lower than 5k in 5th and 6th i get knock....but if i'm getting knock in a certain gear, then shift, the knock goes away because when the rpm's drop, they stay over 5k.
when I say I'm getting knock, i'm talking anywhere from 10-28 counts of knock. usually in the mid-upper teens, or low 20's.
After reading through this thread, I went back and looked at all my knocking logs and no matter how high the knock got, the knock voltage stayed roughly the same, never getting over 2....no spikes.
so, anyone care to venture a guess? i've done a boost leak test, changed timing, and boost, replaced the DV (it was the only thing I couldn't be 100% about not leaking), did a compression check, everything is fine that I can tell.
my car knocks when I do a pull and start from 2k-4k in 1st-4th. if I start at anything higher than 4-4.5k, i get 0 knock. Also, if I start the pull from lower than 5k in 5th and 6th i get knock....but if i'm getting knock in a certain gear, then shift, the knock goes away because when the rpm's drop, they stay over 5k.
when I say I'm getting knock, i'm talking anywhere from 10-28 counts of knock. usually in the mid-upper teens, or low 20's.
After reading through this thread, I went back and looked at all my knocking logs and no matter how high the knock got, the knock voltage stayed roughly the same, never getting over 2....no spikes.
so, anyone care to venture a guess? i've done a boost leak test, changed timing, and boost, replaced the DV (it was the only thing I couldn't be 100% about not leaking), did a compression check, everything is fine that I can tell.
Dec 2, 2010, 12:53 AM
#50
this issue has been going on for months, and countless tanks of gas.
Dec 2, 2010, 01:17 AM
#52
on the log I just looked at, the AFR was a little over 13 when the knock started, then at the highest knock count it was holding around 9.5. looks like its pretty steady at about 9.5 through all the knocking.
also, I don't have a wideband to log with. it was tuned with a wideband though. these logs were just done with a tatrix cable and evoscan.
also, I don't have a wideband to log with. it was tuned with a wideband though. these logs were just done with a tatrix cable and evoscan.
Dec 2, 2010, 02:22 AM
#54
these problems were here pre and post tune. it seems like the knock moved after the tune though. i used to only get this issue at higher rpms and it was random. i got the car tuned though, and there was no knock during the tune, but started again shortly after....like not even a day or so after the tune. then i found that i had a bad injector, so i replaced all four, and my tuner emailed me a new tune for the scaled injectors, but the problem didn't go away. i sent him all the logs, and my rom, and he didn't see that there was anything different from the original tune as far as i know. this was all within a few days of it being tuned.
there's another tuner coming out here this weekend, and i'm going to have him take a look at everything with a wideband.
i guess my question is, does this seem like a tuning issue, mechanical, or false knock?
i have been reading and some people are saying that the knock voltage should spike when there's knock. on my logs, even at 20-28 counts of knock, the knock voltage remains between 1-1.8, or lower, and the most it ever got was 2.1, and that wasn't even at the peak of the knock. so does that tell you anything about whether the knock is legit?
there's another tuner coming out here this weekend, and i'm going to have him take a look at everything with a wideband.
i guess my question is, does this seem like a tuning issue, mechanical, or false knock?
i have been reading and some people are saying that the knock voltage should spike when there's knock. on my logs, even at 20-28 counts of knock, the knock voltage remains between 1-1.8, or lower, and the most it ever got was 2.1, and that wasn't even at the peak of the knock. so does that tell you anything about whether the knock is legit?
Dec 15, 2010, 11:20 AM
#57
Evolved Member
iTrader: (20)
Join Date: May 2007
Location: houston
Posts: 660
Likes: 0
Received 0 Likes
on
0 Posts
if the knock sensor voltage isn't over 2.0-2.5 volts the it shouldnt be real knock. But its strange that its registering a count. Might be a bad sensor.
My post about the knock in low load/rpm areas w/ E85 is directed more towards well tuned cars that see maybe 3-4 counts if WOT below 4krpm etc. This is remedied by pulling timing and adjusting AFR in this sensitive area. Nothing short of what you'd see on 93oct tunes.
The high counts 15-20 you speak of is alarming. BUT... since you report no damage or audible detonation, you MAY want to check the EGR. I've seen 2-3 guys w/ high knock counts (car runs fine minus the timing being pulled) and it turned out that they had multiple vacuum lines blown off either at the EGR (code will show) or at the other tee junctions behind the intake manifold (this may not trigger a code, thus laying undetected). On both occasions we fix the lines and woolah no more knock counts on the logger.
If it was real knock you should see pitting on the pistons tops (if you have a bore scope), not to mention adjusting the tune would lower the knock count anyways. Bad fuel? just put lucas octane booster or racegas and see if it goes away. Worse case scenario is rod knock, but honestly if that was the case, your motor would've been long gone by now.
Problem solving is a bish... but these are good starting points.
-Tom
My post about the knock in low load/rpm areas w/ E85 is directed more towards well tuned cars that see maybe 3-4 counts if WOT below 4krpm etc. This is remedied by pulling timing and adjusting AFR in this sensitive area. Nothing short of what you'd see on 93oct tunes.
The high counts 15-20 you speak of is alarming. BUT... since you report no damage or audible detonation, you MAY want to check the EGR. I've seen 2-3 guys w/ high knock counts (car runs fine minus the timing being pulled) and it turned out that they had multiple vacuum lines blown off either at the EGR (code will show) or at the other tee junctions behind the intake manifold (this may not trigger a code, thus laying undetected). On both occasions we fix the lines and woolah no more knock counts on the logger.
If it was real knock you should see pitting on the pistons tops (if you have a bore scope), not to mention adjusting the tune would lower the knock count anyways. Bad fuel? just put lucas octane booster or racegas and see if it goes away. Worse case scenario is rod knock, but honestly if that was the case, your motor would've been long gone by now.
Problem solving is a bish... but these are good starting points.
-Tom
Dec 18, 2010, 11:21 AM
#58
Question for those who tune for e-85. Do you ever have to use more conservative timing when first changing from gas to e-85 due to some carbon buildup left over from gas use?
Dec 18, 2010, 06:16 PM
#59
if the knock sensor voltage isn't over 2.0-2.5 volts the it shouldnt be real knock. But its strange that its registering a count. Might be a bad sensor.
My post about the knock in low load/rpm areas w/ E85 is directed more towards well tuned cars that see maybe 3-4 counts if WOT below 4krpm etc. This is remedied by pulling timing and adjusting AFR in this sensitive area. Nothing short of what you'd see on 93oct tunes.
The high counts 15-20 you speak of is alarming. BUT... since you report no damage or audible detonation, you MAY want to check the EGR. I've seen 2-3 guys w/ high knock counts (car runs fine minus the timing being pulled) and it turned out that they had multiple vacuum lines blown off either at the EGR (code will show) or at the other tee junctions behind the intake manifold (this may not trigger a code, thus laying undetected). On both occasions we fix the lines and woolah no more knock counts on the logger.
If it was real knock you should see pitting on the pistons tops (if you have a bore scope), not to mention adjusting the tune would lower the knock count anyways. Bad fuel? just put lucas octane booster or racegas and see if it goes away. Worse case scenario is rod knock, but honestly if that was the case, your motor would've been long gone by now.
Problem solving is a bish... but these are good starting points.
-Tom
My post about the knock in low load/rpm areas w/ E85 is directed more towards well tuned cars that see maybe 3-4 counts if WOT below 4krpm etc. This is remedied by pulling timing and adjusting AFR in this sensitive area. Nothing short of what you'd see on 93oct tunes.
The high counts 15-20 you speak of is alarming. BUT... since you report no damage or audible detonation, you MAY want to check the EGR. I've seen 2-3 guys w/ high knock counts (car runs fine minus the timing being pulled) and it turned out that they had multiple vacuum lines blown off either at the EGR (code will show) or at the other tee junctions behind the intake manifold (this may not trigger a code, thus laying undetected). On both occasions we fix the lines and woolah no more knock counts on the logger.
If it was real knock you should see pitting on the pistons tops (if you have a bore scope), not to mention adjusting the tune would lower the knock count anyways. Bad fuel? just put lucas octane booster or racegas and see if it goes away. Worse case scenario is rod knock, but honestly if that was the case, your motor would've been long gone by now.
Problem solving is a bish... but these are good starting points.
-Tom
well tuned cars wont show knock.. if the tuner knows what hes doing he will have all his bases covered and if its phantom knock he will get rid of it in a safe manor.
Good rule of thumb is, if you can rev the car in neutral to 7k and etc 3-4 times and it doesnt knock, yet knocks when driving it .. chances are its real knock. (unless theres something else going on suspension wise, etc (which would be audible)
The voltage theory isnt bad, but does all knock equal similar voltage to be consistent enough to determine whats real and fake? when i tuned my personal car i just used the reving method and cruising around and slowly adjusted the multipliers to compensate. (I had ALOT of phantom knock from kelford 272 cams)
I know i didnt drowned out the knock fully in my car because I can make it show knock counts by changing the timing curve.. and yes e85 will knock