Roughness on initial takeoff

[Amm5890]

Hey man. I am getting the same feeling. I am also pretty sensitive to certain things in vehicles. Mine feels much smoother when it’s warmer out especially after the break in period. It’s more apparent when it’s cold and damp outside.

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[tezzasaurusrex]

I also made a thread on this if you do a search. The engine would buzz and vibrate in two waves as it went past 2-4k rpm. It almost felt like a car that had its balance shafts out of phase due to a bad timing belt install. I'm happy to report that after several track days I no longer feel the vibrations, I'm still perplexed as to the root cause because it doesn't make sense for it to go away when it's a "unbalanced" engine but hey I'm not upset that it's smoothened out ?

 

[Zone47]

Quick question for everyone on the FL5. This is my first K20 and I’ve read countless threads about how this engine isn’t the smoothest. I’m also aware that there are no balance shafts and this was an intentional move by Honda.

I feel the vibration going through the rev range that everyone talks about but does anyone feel a sort of roughness/vibration going through the steering wheel when initially taking off from a stop? Just a normal take off in traffic not racing. You let the clutch out normally and start applying throttle and I can feel vibration through the steering wheel until I’m all the way out of the clutch. Nothing crazy feeling but it’s not buttery smooth like I’m used to on manual trans. My other car is 22 year old s2000 and that thing is like butter coming from a stop.

Makes me almost feel like i need to bleed the clutch fluid lol. Car drives fine and pulls like a champ but that initial vibration when going from a dead stop is somewhat annoying. Just wondering if anyone else feels this.

and to be clear, this isn’t a crazy vibration like the steering wheel is gonna fall off. Just a noticeable vibration when taking off in first that I don’t notice on my S2000. It’s the only other manual that I drive regularly so only thing I have to compare

I'm glad you brought this up because I felt the same thing, usually in first gear and then to a lesser extent in second- sixth.

I was thinking:
1. Either I got a bogus engine with a balance problem. I don't know that these cars ever had a balance shaft, but maybe it has to do with the nearly even 86mm x 85.9mm bore and stroke on this engine? I'm not sure but maybe many of Honda's engines are oversquare? The S2000 AP1 must have been oversquare considering the 8900rpm redline.

2. Feels like it could be solid motor mounts. Either that or super rigid urethane material?

3. I know the flywheel was lightened up.... maybe a crappy balance on that?

Since you brought it up, it must be across the board... but maybe some cars are worse than others. My RSX-S was smooth as glass... same family of engines.


Whoops, now I'll read the thread and probably find out the real problem.

 

[TypeRD]

@Zone47 The RSX-S indeed has a related engine, but it was NA, balanced (except for the crankshaft I believe), and fuel injected ; Quite different than what’s in the FL5, despite the K20 lineage.

Coming from a K20Z3 myself, I know what you mean by those older engines running glass smooth thru the whole rev range. The slight noise/vibration of the K20C2 is rather new to me too, but I like it. To me it’s just a characteristic of the engine and not a problem.?

 

[CTR]

I have a feeling we will be going through waves of these types of posts whenever there are big shipments to the US...

Nothing is wrong with your car - it's just the way it is. This engine had the balance shafts removed intentionally to free up HP and give it more character.

Honda make some of the most reliable engines you can buy. You have a 3 year warranty. Rest easy and redline it daily! But only after after reaching operating temp (4 bars and I personally like to wait until 160° F at least).

I remember in my S2000 ownership days a new owner would frequently create a thread asking why VTEC wasn't engaging when the engine was cold. As long as you aren't asking this question you will probably have zero issues.

 

[UCF120]

Looks like a lot feel what I’m feeling and a lot also don’t ? just depends on the individuals sensitivity to certain sounds and vibrations in cars.

@Jester04 actually lives really close to me and graciously allowed me to drive his car a couple days ago to see if his car does it also. I didn’t necessarily feel the slight clutch pedal vibration in his car but I did feel the exact steering wheel vibration in his car that I get in mine while letting off the clutch.

his car also had the Hasport 62a RMM and Acuity shifter bushings among a ton of other mods. His car felt great! Actually the reason I’m going to get the 62A mount and Acuity bushings. His car felt really solid and connected without the rubber band feeling that the stock mount gives. Didn’t fell any other ‘extra’ vibrations from the mount also.

And for what it’s worth, the engine vibration felt through the steering wheel while actually accelerating through the rev range while already off the clutch is not what I’m referring to here. Although I feel that as well, on top of the countless threads about it, Honda has actually said this motor has no balance shafts and the vibration is apart of the cars character. I expected that vibration and it does not bother me.

What I’m referring to is this steering wheel and clutch pedal slight vibration I was getting while coming off the clutch from a dead stop. Almost felt like clutch shudder. I almost think I do have some clutch shudder that I can feel in the pedal but since Jesters car had the same steering wheel vibration, I’m not to concerned about it anymore. Gonna try and bleed the clutch fluid soon anyway and see if I can get it to go away a little more.

 

[Zone47]

@Zone47 The RSX-S indeed has a related engine, but it was NA, balanced (except for the crankshaft I believe), and fuel injected ; Quite different than what’s in the FL5, despite the K20 lineage.

Coming from a K20Z3 myself, I know what you mean by those older engines running glass smooth thru the whole rev range. The slight noise/vibration of the K20C2 is rather new to me too, but I like it. To me it’s just a characteristic of the engine and not a problem.?

So, balance is a function of crankshaft, rods, pistons, bore and stroke working together smoothly over rpm. My assumption is that both engines being 2.0 liter would have the same bore and stroke as well, 86mm x 86mm. From what I can find with google on the K20A2, there is no balance shaft in that engine so why more vibration with the K20C1? I would think the rotating assembly would be beefed up quite a bit to compensate for the turbo charging as in heavier duty pistons, rods, bolts and crank. Who knows. If it's the turbo that is causing the vibration, we have problems in the long run. I also wonder why if using the same bore and stroke, the old Type S could rev to 7900 rpm and the Type R is redlining at 7K?

The other idea too, race engines (from the good ol days) had solid mounts which certainly transmitted vibration to the chassis. I'm thinking the CTR mounts might not be solid but pretty stiff and unforgiving... who knows. Yeah, in the big picture it's not a problem but it does make the car seem a bit more unrefined. I'm interested and will dig in deeper.

 

[TypeRD]

@Zone47 Let us know what you find. You’re right the K20C2 doesn’t have balance shafts. I got engines mixed up and was looking at the K20A3 when I made my earlier statement, and don’t want to assume the K20A2 also doesn’t have an unbalanced crankshaft. There’s so much different info and it’s easy to get mixed up. Be sure you’re looking at the K20C2. The K20C1 is not the same engine as what’s in the FL5. The K20C1 is what’s found in the 2.0T Accord and RDX I’m pretty sure. I think it’s also the basis for the NA 2.0 found in some models.

So a K20A2 vs K20C2 breakdown is what we need.?

 

[Jester04]

Looks like a lot feel what I’m feeling and a lot also don’t ? just depends on the individuals sensitivity to certain sounds and vibrations in cars.

@Jester04 actually lives really close to me and graciously allowed me to drive his car a couple days ago to see if his car does it also. I didn’t necessarily feel the slight clutch pedal vibration in his car but I did feel the exact steering wheel vibration in his car that I get in mine while letting off the clutch.

his car also had the Hasport 62a RMM and Acuity shifter bushings among a ton of other mods. His car felt great! Actually the reason I’m going to get the 62A mount and Acuity bushings. His car felt really solid and connected without the rubber band feeling that the stock mount gives. Didn’t fell any other ‘extra’ vibrations from the mount also.

And for what it’s worth, the engine vibration felt through the steering wheel while actually accelerating through the rev range while already off the clutch is not what I’m referring to here. Although I feel that as well, on top of the countless threads about it, Honda has actually said this motor has no balance shafts and the vibration is apart of the cars character. I expected that vibration and it does not bother me.

What I’m referring to is this steering wheel and clutch pedal slight vibration I was getting while coming off the clutch from a dead stop. Almost felt like clutch shudder. I almost think I do have some clutch shudder that I can feel in the pedal but since Jesters car had the same steering wheel vibration, I’m not to concerned about it anymore. Gonna try and bleed the clutch fluid soon anyway and see if I can get it to go away a little more.

Happy to help! When I drove your car it felt normal. Just keep driving it and everything will smooth out. Your pedal vibration feels like just the disc engaging with the flywheel.

We are going to get @UCF120 some things and go from there.

 

[TypeRD]

Isn’t our engine the K20C1? Accord used K20C4 per a quick search.

UGH!? Yes, the K20C1 is correct for the FL5. I can’t keep the nomenclature straight. Appreciate you verifying my (mis)info.?‍ The K20C2 is (I believe) the NA 2.0 found on some models.

 

[Zone47]

UGH!? Yes, the K20C1 is correct for the FL5. I can’t keep the nomenclature straight. Appreciate you verifying my (mis)info.?‍ The K20C2 is (I believe) the NA 2.0 found on some models.

Ok got that straight. What I find odd is the K20A2 has pretty much the same 86mm bore and stroke as the K20C1 but the N/A K20A2 redlined at nearly 8,000 rpm... and smooth as butter. So I have to wonder why the C1 version has the redline set to only 7,000? My guess is the torque curve falls off too much because of the turbo and cams tuning and there isn't any benefit? ... but the assembly might be able to spin higher if different tuning opened things up.

Here is another thought about the vibration issue: So balancing is labor intensive and consequently expensive, and maybe finer balancing is just one of the cost saving things Honda is doing to make the car more affordable? It's barely noticeable but funny thing, we all pretty much are aware of it.

 

[TypeRD]

Ok got that straight. What I find odd is the K20A2 has pretty much the same 86mm bore and stroke as the K20C1 but the N/A K20A2 redlined at nearly 8,000 rpm... and smooth as butter. So I have to wonder why the C1 version has the redline set to only 7,000? My guess is the torque curve falls off too much because of the turbo and cams tuning and there isn't any benefit? ... but the assembly might be able to spin higher if different tuning opened things up.

Here is another thought about the vibration issue: So balancing is labor intensive and consequently expensive, and maybe finer balancing is just one of the cost saving things Honda is doing to make the car more affordable? It's barely noticeable but funny thing, we all pretty much are aware of it.

Yeah that makes sense : Why run the RPM’s higher if there’s very little or no more power available? I want to say I saw a video or read somewhere that Honda was intentionally conservative with the RPM limit for the sake of reliability. Peak torque is at 2.5k RPM’s with the K20C1. In the K20A2, peak torque didn’t happen until 7k RPM’s (if my info is correct). So, you pretty much had to redline it to get all that VTEC power. In that way, the K20C1 definitely feels weird after owning an NA K20 for nearly 14 years prior.?

I personally don’t think the lack of balancing was a cost saving measure. It certainly results in cost savings, but I don’t think they did it for that sole reason. Keep in mind this engine is already refined to the point that they have to make up for it by pumping in fake engine sounds.? This is not something the NA k20’s ever needed (because they were screamers). So, when Honda says they decided to forego balancing shafts in effort to give the K20C1 “character” and feedback to the driver, I tend to believe them. I don’t believe they would intentionally build an engine that will rattle itself apart for the sake of said character.

 

[PointByPatrol]

You guys think the clutch delay valves might have something to do with it? Anybody delete their delay valves yet?

 

[Zone47]

Yeah that makes sense : Why run the RPM’s higher if there’s very little or no more power available? I want to say I saw a video or read somewhere that Honda was intentionally conservative with the RPM limit for the sake of reliability. Peak torque is at 2.5k RPM’s with the K20C1. In the K20A2, peak torque didn’t happen until 7k RPM’s (if my info is correct). So, you pretty much had to redline it to get all that VTEC power. In that way, the K20C1 definitely feels weird after owning an NA K20 for nearly 14 years prior.?

I personally don’t think the lack of balancing was a cost saving measure. It certainly results in cost savings, but I don’t think they did it for that sole reason. Keep in mind this engine is already refined to the point that they have to make up for it by pumping in fake engine sounds.? This is not something the NA k20’s ever needed (because they were screamers). So, when Honda says they decided to forego balancing shafts in effort to give the K20C1 “character” and feedback to the driver, I tend to believe them. I don’t believe they would intentionally build an engine that will rattle itself apart for the sake of said character.

Yeah, the vibration is such a minor issue, you're probably right, I don't think Honda was too worried about it. And maybe with more break in it will fade a bit? who knows. Weird that most of us only feel it in 1st gear.

I do enjoy Honda's refinement in regards to the power curve as they did a great job. To me the car feels like a strong N/A engine (for the most part) because of the power coming on right off the bottom and being fairly flat across the board.

 

[Zone47]

You guys think the clutch delay valves might have something to do with it? Anybody delete their delay valves yet?

Interesting point considering it's always felt in the lower rpms and in 1st gear... might be something to look at closer.

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