So what are you guys doing about 4th/5th gear knock?

[Force Fed Mopar]

When I run the car in the 8th I don't see knock, but if I'm out on the highway and drop to 4th and kick it, it lights the CEL. Same if I run up through the gears on the street, 1st 2nd 3rd are usually good, but once I get it into 4th gear it'll light it up, usually as soon as the boost comes back on after the shift. Sometimes it goes back out right away and sometimes it stays on. Fuel is good (low 11's). Is it just the extra pressure from having the car in a high gear at 3500ish and full boost(18-20 psi) Running on 93 octane btw. I have the WOT timing pretty low, to the point that I feel it is hurting my power, because it will break loose easier part-throttling it than at WOT.

Engine is a 2.5 bone stock w/ .040-over Wisecos, ported exhaust manifold, stock Garrett, 2.5" sv and 3" exhaust w/ a hi-flow cat and a resonator, and an AWIC setup w/ no reservoir. Not sure if the intake temps are rising because I don't have a reservoir and the IC core is heat soaking or what. Figured I'd see if anyone else is having this issue.

[1BADVAN]

I don't know the best way, but you could use the boost control maps to lower the boost a bit at those speeds, not the best way but maybe that much boost and that much load is too much for your octane to handle??

Also Is your A/C switch on? Weird i know but in my dad's van if the A/C is on the Dawes device will run lean, but it runs great with it off. Not sure if it is really lean, or a weird electrical interference.

Just some ideas, I know probably not exactly what you are looking for.

[ShelGame]

When I run the car in the 8th I don't see knock, but if I'm out on the highway and drop to 4th and kick it, it lights the CEL. Same if I run up through the gears on the street, 1st 2nd 3rd are usually good, but once I get it into 4th gear it'll light it up, usually as soon as the boost comes back on after the shift. Sometimes it goes back out right away and sometimes it stays on. Fuel is good (low 11's). Is it just the extra pressure from having the car in a high gear at 3500ish and full boost(18-20 psi) Running on 93 octane btw. I have the WOT timing pretty low, to the point that I feel it is hurting my power, because it will break loose easier part-throttling it than at WOT.

Engine is a 2.5 bone stock w/ .040-over Wisecos, ported exhaust manifold, stock Garrett, 2.5" sv and 3" exhaust w/ a hi-flow cat and a resonator, and an AWIC setup w/ no reservoir. Not sure if the intake temps are rising because I don't have a reservoir and the IC core is heat soaking or what. Figured I'd see if anyone else is having this issue.

Is it actual audible knock? Or just lighting the CEL? What does your knock threshold curve look like?

[RoadWarrior222]

Also Is your A/C switch on? Weird i know but in my dad's van if the A/C is on the Dawes device will run lean, but it runs great with it off. Not sure if it is really lean, or a weird electrical interference.

There was a rumor that there was a lean cruise program on some vehicles, activated by the HVAC controls, because emissions testing was done with that off, but most people drove with it on, and it gave better mpg. That's rumored particularly of GM cars, but I dunno if the others got up to it also.

[1BADVAN]

There was a rumor that there was a lean cruise program on some vehicles, activated by the HVAC controls, because emissions testing was done with that off, but most people drove with it on, and it gave better mpg. That's rumored particularly of GM cars, but I dunno if the others got up to it also.

Interesting,

[turbovanman²]

Its because your loading it up more, so back off the timing. That's what happens to me, I'll road tune it, good to go, hit the track, its runs lean and knocks,

[RoadWarrior222]

I was hearing the other day, that you should try and set it up on torque peak, if you know or can make an educated guess where that is... i.e. brake torque it there... then it should be shiny elsewhere...

[roachjuice]

Just let it flash. Thats what I did. I wish you could set timing based on vehicle speed.

[RoadWarrior222]

"The flashing engine light bothered me... so I put tape over it"

[zin]

3500 seems kind of low, and a low RPM combine with high cylinder pressure is a recipe for detonation, but like Rob was intimating, it might be that it's just "noise"...

One way to be sure would be to fill it with some 100(+) octane unleaded and see if that changes anything. If it doesn't, I'd expect it to be just "noise", if it stops it, then it's genuine detonation.

Mike

[ShelGame]

3500 seems kind of low, and a low RPM combine with high cylinder pressure is a recipe for detonation, but like Rob was intimating, it might be that it's just "noise"...

One way to be sure would be to fill it with some 100(+) octane unleaded and see if that changes anything. If it doesn't, I'd expect it to be just "noise", if it stops it, then it's genuine detonation.

Mike

That's a good plan...

[RoadWarrior222]

Though, if it's extended to 100 with toluene or something, you might not find the knock when you go back to 98 or whatever, since it was getting a little carbed up or injectors were a little gummy and it cleaned it out.

[cordes]

Its because your loading it up more, so back off the timing. That's what happens to me, I'll road tune it, good to go, hit the track, its runs lean and knocks,

That's what trips up a lot of folks. Hardly anyone drags the brakes to peak cyl temps and then they wonder why it wants to knock when under heavy load for any duration. There is a big difference between what you can sustain going down the 1/4 and what you can do when you put your foot down in 5th gear on the freeway.

[turbovanman²]

That's what trips up a lot of folks. Hardly anyone drags the brakes to peak cyl temps and then they wonder why it wants to knock when under heavy load for any duration. There is a big difference between what you can sustain going down the 1/4 and what you can do when you put your foot down in 5th gear on the freeway.

Yep, so you just gotta remember that road tuning is good but you still have to tweak at the track.

[shadow88]

Or you do all your tuning on empty country roads in 4th or 5th and it's under the most load it can be. I often start my test sessions at 80 mph and get well above 120 for that very reason.

What is the actual knock sensor output reading?

[shackwrrr]

Or tune on 89 then switch to 93.

[BadFastGTC]

I would suggest you run the reservoir with ice water, also a bigger turbine to reduce backpressure. Put in a fresh set of plugs, go out for a blast, stop & change plugs, read for knock.

[GLHNSLHT2]

A reservoir is a must. One that cycles through. Old 80's volvo's are perfect for it. You drill and tap a small "bleed" hole in the top of the "out" tank of the i/c's water manifold, and run a small 5/16" line or so to the top nipple on the volvo reservoir, Then on the bottom of the reservoir is like a 5/8's or 3/4" line that you just T into the big line returning to the pump. This way air get's bled out of the system. I don't care HOW you fill the system, there will be air in it unless you bleed it into a reservoir. And that air makes the i/c not as efficient at cooling obviously.

On my friends mini van we filled the i/c and hole system as best we could to keep all the air out before we put in the reservoir. Doing WOT blasts the i/c would get warm. If you cracked the inline rad cap on the system coolant would shoot out because of the air in the system pressurizing it. So we did the above and now you can do 4-5 WOT blasts up to 100+ and the i/c is cold to the touch, you can crack open the system with it running and there's just nice coolant flowing by not under any pressure at all. Won't even spill any. It also makes the system much easier to fill. No more holding the ic straight up and waiting for coolant to come out then trying to get the hoses on before any spills out. You just fill the reservoir, turn the system on and it does all the work in about 4 minutes.

[Force Fed Mopar]

Is it actual audible knock? Or just lighting the CEL? What does your knock threshold curve look like?

I don't hear anything. Here is my current knock threshold


I was thinking of either lowering the midrange timing, or I was wondering if the multiplier would be useful for this? It may just be more noise from the increased pressure through.

Its because your loading it up more, so back off the timing. That's what happens to me, I'll road tune it, good to go, hit the track, its runs lean and knocks,

That's what trips up a lot of folks. Hardly anyone drags the brakes to peak cyl temps and then they wonder why it wants to knock when under heavy load for any duration. There is a big difference between what you can sustain going down the 1/4 and what you can do when you put your foot down in 5th gear on the freeway.

Yep, so you just gotta remember that road tuning is good but you still have to tweak at the track.

I am having the opposite problem though Simon, does fine at the track but knocks on the street. I don't want to back of the timing any more because I think it is already hurting my power.

A reservoir is a must. One that cycles through. Old 80's volvo's are perfect for it. You drill and tap a small "bleed" hole in the top of the "out" tank of the i/c's water manifold, and run a small 5/16" line or so to the top nipple on the volvo reservoir, Then on the bottom of the reservoir is like a 5/8's or 3/4" line that you just T into the big line returning to the pump. This way air get's bled out of the system. I don't care HOW you fill the system, there will be air in it unless you bleed it into a reservoir. And that air makes the i/c not as efficient at cooling obviously.

On my friends mini van we filled the i/c and hole system as best we could to keep all the air out before we put in the reservoir. Doing WOT blasts the i/c would get warm. If you cracked the inline rad cap on the system coolant would shoot out because of the air in the system pressurizing it. So we did the above and now you can do 4-5 WOT blasts up to 100+ and the i/c is cold to the touch, you can crack open the system with it running and there's just nice coolant flowing by not under any pressure at all. Won't even spill any. It also makes the system much easier to fill. No more holding the ic straight up and waiting for coolant to come out then trying to get the hoses on before any spills out. You just fill the reservoir, turn the system on and it does all the work in about 4 minutes.

Yeah I am gonna have to get one I think. I'm probably going to have to build one though to put it where I want it (battery tray area).

[shackwrrr]

VW coolant bubbles make nice universal pressure tanks.