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  #21  
Old 11-22-2013, 08:19 AM
Sleepy_Steve Sleepy_Steve is offline
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I have 20 odd weekends on my current 160k mile KA that's in the car and it's still doing alright. Shifting at 6400, figure most of the time it's averaging about 6000 rpm on track.

I might shift at 6000 on a more stock one, but that's about all I think you'd need to do.
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  #22  
Old 11-22-2013, 08:50 AM
240sxTTC 240sxTTC is offline
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If they let a supercharged miata do it, I don't see why you can't do it with a tapering boost turbo on a 240.
A supercharger is different in that it can't make the crazy torque or pwr plateau a turbo can. In general they are starting to crack down on crazy torque builds. Someone in my region was going to do the same thing with a turbo Miata and was denied the re-class.
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  #23  
Old 11-22-2013, 09:06 AM
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I still think it'd be reasonable to do something like run 8-9 psi in the midrange then taper it down a ton. You'd have like ~220-240 rwtq and 158 rwhp. Would they crack down on that?

It's not much different than the cars with lots of variable valve timing like the S54B32, where you can do like 280 rwtq and like 240-250 rwhp for a long long time.


The turbo isn't really that bad. Cheap eBay components will work just fine, but I would just mod a stock SR manifold. It'll be pretty darn cheap really. And a bottom mount lets you use all the cheap SR stuff like turbo outlets and downpipes.

I don't think there's that much more that can go wrong on the turbo setup when you don't have to worry about the manifold really (I would just go ahead and weld the turbine hsg to the manifold tho' - they're both cheap so who cares, but that's an unpopular viewpoint here).
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  #24  
Old 11-22-2013, 09:08 AM
240sxTTC 240sxTTC is offline
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What would you limit RPM to on a stock motor, if endurance and durability were a big concern (read: Chump Car).
Not sure as my project goals were 225whp and 7800rpm. Based on your pwr level, operating conditions and max rpm, you have to determine the service life.

The half-weighted crank of the KA24DE engine beats up the bearings at higher rpm and definitely above stock redline. Oil pressure is a great indicator of bearing condition. It's obviously best to start with a fresh motor. Monitor and record oil pressure at idle and 3Krpm at full operating temp. Compare these values to the service manual min. From the recorded and service manual min values, you can establish a usable service life.
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  #25  
Old 11-22-2013, 09:13 AM
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There are so many cheap components for our cars that going turbo is really easy. You can get an eBay FMIC kit for like $170 shipped. Then the SR manifold + KA flange is not expensive at all. I'd maybe go with a big external gate to ensure you can bleed enough boost though, but maybe you can do it with a ported internal gate. But it'd be tough given the spring rate of most actuators is ~7 psi, which is way more than you can run and make 158 rwhp.

With a basic NA build you'll probably make 158 rwhp for ~500 RPM, maybe 1-1.2k RPM max? The turbo setup can probably do it for more like 3-3.5k RPM without running big boost in the midrange, and running some tiny cams so your bottom end torque is even more stout if you do fall out of boost (doubtful). Big difference in speed out there.
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  #26  
Old 11-22-2013, 09:14 AM
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I still think it'd be reasonable to do something like run 8-9 psi in the midrange then taper it down a ton. You'd have like ~220-240 rwtq and 158 rwhp. Would they crack down on that?

It's not much different than the cars with lots of variable valve timing like the S54B32, where you can do like 280 rwtq and like 240-250 rwhp for a long long time.
Yes, which is why they are cracking down on torque builds. There aren't any stockish cars in the TTE/D level that make 50% more torque than hp at the wheels w/ a flat hp curve for the last 3krpm. Keep in mind that with a re-class you no longer take pts for engine mods. There needs to be parity amongst engines (turbo, supercharged, NA) taking no mod pts otherwise everyone is going to be forced to build a torque monster turbo engine or stuff in a V8.

177wtq/158whp would be a better comparison to 280wtq/250whp. It's also not just about the peak value but the area under the curve they are starting to really evaluate.
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  #27  
Old 11-22-2013, 02:03 PM
Sleepy_Steve Sleepy_Steve is offline
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^ Cracking down on torque builds does make me inclined to continue with my current NA plans.
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  #28  
Old 11-22-2013, 03:08 PM
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Originally Posted by 240sxTTC View Post
Yes, which is why they are cracking down on torque builds. There aren't any stockish cars in the TTE/D level that make 50% more torque than hp at the wheels w/ a flat hp curve for the last 3krpm. Keep in mind that with a re-class you no longer take pts for engine mods. There needs to be parity amongst engines (turbo, supercharged, NA) taking no mod pts otherwise everyone is going to be forced to build a torque monster turbo engine or stuff in a V8.

177wtq/158whp would be a better comparison to 280wtq/250whp. It's also not just about the peak value but the area under the curve they are starting to really evaluate.
There's really not much difference there, just a question of the rev range the power is being made.

The S54's will do it from about 4.5-8k RPM. The KA will do it from about 3.5-7k RPM. Lower revs = higher peak torque number due to the torque to HP formula, but making the power over relatively the same width rev band gives the same effect.


There needs to be a robust formula that doesn't benefit high revving cars that get a wide powerband by having their torque measured in ft-lbs arbitrarily lower than the same width of flat powerband on a lower revving engine.

It's just a question of units, revs, and ratios.

I think a more common sense approach of "if your HP does not deviate from peak by more than 5% over a 20% your rev range window, you take on some points penalty, or get bumped up a class." Make it cut and dried, and if they really don't want HP flattening, tighten up the rev window. You can figure all that stuff in your head just looking at a dyno graph, so it's not complex.



But maybe I'm just thinking like an engineer, and not a big fan of NASA's "maybe you're in this, or maybe in that" approach to TT classing.
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  #29  
Old 11-25-2013, 06:51 AM
Sleepy_Steve Sleepy_Steve is offline
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Quote:
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But maybe I'm just thinking like an engineer, and not a big fan of NASA's "maybe you're in this, or maybe in that" approach to TT classing.
I kind of like the option to pick where I run based on where the other people are.

For now I have to figure out why the car's running lean all the time before anything with the new block. 17-1 under load near the top of 4th
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  #30  
Old 11-25-2013, 02:21 PM
Def Def is offline
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What's the calculated load do on a pull? Known good injectors and MAF?

I like the flexibility with classing too, but it seems way too open to interpretation. I know it's grassroots and that's the spirit of the rules, but I don't think its that hard to at least start to give more definitive "do and do not do" guidelines a la turbo builds.
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