People remove the balance shafts from the ecotec engine because, like all balance shafts they spin at twice the crank speed and are, by nature, unbalanced shafts. On the ecotecs they're cast d shaped shafts, like most balance shafts, and like to explode and take out the whole block if you spin them over 7k for any significant amount of time. They are for NHV only, they cancel out the inherent 4th order vibration in an even fire inline 4 cylinder.

 

I've familiar with the balance shafts getting yanked on 9k 4G63 and 4B11T builds.

 

There's no problem going with a k20 oil pump in a k24. It's done in the honda world all the time. The k20 pump is superior to the k24 pump.

 

If the bump steer induced is minimal, can any of it be taken out by adjustable (shim up or down) outer tie rod ends?

Does moving the rack in that way affect ackerman at all?

 

The bumpsteer and ackerman issues induced by shifting the rack fore/aft cannot be tuned out by raising or lowering the rack or the balljoints. The only thing that would help would be a modified spindle, and then you would have to compensate for the geometry with a different steering rack ratio.

Basically, it's not fixable.

 

Yeah I have lost interest in this swap, end of the year I'm jumping ship for a S2000

 

Best move, after this year of racing I'll be looking for another s2000 to turn into a track car as well

 

Running costs of an S2k are much higher than a miata. I've got one..that's why we decided to do this K swap into this car.

 

Pretty sure I'd do the swap if the kit sans engine could be done for $7k. I've had a couple vtak ricers back in the day and always missed the Honda engines after getting the Miata.

 

After playing around in a suspension kinematics program, it doesn't seem that moving the rack fore and aft affects bump steer as much as you'd think. If the axis through the control arms are parallel to the vehicle centerline (no caster change), the bump steer is completely unaffected, given the z-height remains the same. If the axis is not parallel to the centerline, the bump steer will change, but it's hard to say how much without a coordinate representation of the car. With the vehicle I used to play around with, moving the rack 1" changed the bump steer at full bump, 0.04 degrees. Which in my eyes is negligible, especially at the front. But, however, it does change the Ackerman. Whether it is enough change to care, change for the good, or change for the bad, it's hard to say at this point.

 

^This guy hit the nail on the head. Will it affect steering? probably. Will it be enough to actually matter? We don't think so, and neither do other guys that have done similar swaps.

So instead of going back and forth about this forever, let me finish the swap, get an alignment, and go for a drive. If it leaves something to be desired, then I will look into other options.

For those of you who are supportive of this swap, thank you. I'm spending all the time and money to try it out, so I appreciate your kind words.

I have a feeling the whole steering issue is not going to be much of an issue when we have the car on track abusing people.

 

I for one, would like to see a graphs showing the ackerman and toe for both OEM and the K swap. Going through Riverside at BRP at 100mph with a depowered rack (faster ratio) the steering wheel is at 90°. The info might be relevant.

 

Just obvious thoughts.
Increased Ackerman means larger toe-out with increased steering angle than before change. Would moving the rack forward increase or decrease the Ackerman (or reverse it, since it's a large change)?

Or taking a bit futher Home Page (I have not read all and can't grasp even half of i on a Friday).
It looks like it's much much more than simple angles at play, move the rack too much and you might end up with something completely different than a Miata.

 

I don't feel like looking under my car right now, but it all depends on where the current rack is located. I'm pretty sure it's rear steer (rack/tie-rod rearward of the wheel centerline), so it depends on whether the rack is currently forward, rearward, or inline to the tie-rod pickup point on the upright.

Something to note: this is ALL guess work, basically. Do we know why Mazda chose the Ackerman value they did? Did they tune specifically for performance, or not? Also, as soon as you put on tires that were not factory (which is any tire made today..) Mazdas tuning is altered. I'm excited to see what happens with this car, because testing is really the only solution in this case. Unless the tires used had released tire data (I would LOVE to have tire data for a sticky street tire ) it's impossible to quantify these changes.

Also, just a basic note on Ackerman. High pro-Ackerman will induce good corner entry. The inside tire is steered much more the outside, which kind of acts as an "inside tire brake", thus yawing the car. A lot of tires, though, generate more lateral grip at lower Ackerman settings, but may not enter a corner as sharp. It's all a matter of the individual tire properties, and how/when they generate lateral forces based on loads and slip angles. Sometimes you can use a lower Ackerman, and gain back some turn-in with other tweaks (static toe-out, rear toe-out, dynamic rear-toe, springs/bars, etc..). I'm soon going to be testing a racecar with adjustment available of ~150% pro, parallel, and ~150% anti-Ackerman, which I'm super excited to see the results!

Sorry for keeping up a slightly off-topic discussion, I get carried away with this suspension stuff

 

props to you guys for trying this, I hope it pans out well. please keep the updates coming. my TSX motor just let go and my turbo Miata is getting on my nerves...

did I miss the answer on the balance shafts? I know several brands pull theirs, honestly didn't even know the K24 had them till last week. does the K20?

 

Just read this on magicdc2's build thread over at k20.org.

"I finally have two parts I've been waiting on - the custom flywheel, and the S2000 manifold adapter.

I also just picked up a healthy k24a2 to use for testing, instead of this blown motor we used for mock-up.

I have had zero time to work on the car, but I'm hoping to have some real updates soon. Finally, we are working on a difference design for our subframe and steering rack setup that will preserve the OEM rack location. Too soon to go into details, but as I said before, the hacked up OEM subframe is only a first step."

w00t, sounds good to me.

 

My understanding is that the early K20s (ie RSX-S) do not, and the later ones (ie '06-'11 Civic Si) do have them.

 

Yup. Most people run k20a2 oil pumps which are good to 8700 rpm stock. No balance shafts, that's the pump I've been running since 2009. Zero issues.

 

I love hondas probably more than most here, but this thread really makes me want to v8 swap my miata. Of course most people dont have a ls6/t56 pullout collecting dust on their garage floor.

 

There was fast progress, and now there is none?

What's the dealio