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  #11  
Old 10-12-2016, 10:20 AM
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Quote:
Originally Posted by clotuning
.025 sounds really loose to me, but Im new to the road racing scene. drag racing I never wanted anything looser than .020, I would guess it has to be more loose since your at 200 degrees for a much longer time so your clearances get tighter?

And I think the cranks are nitrided because they break when you use a cut crank for racing
Are you sure cranks break because they lose the nitride coating or because the fillets/radii get ruined from the grinding and cause excessive stress concentration?

Read that article I linked if you haven't. There's a decent explanation about clearances. You can choose to use the lower value clearance multiplier of 0.00075" per inch of journal diameter + 0.0005" high performance application = 0.002" clearance for KA rod bearings.

I adjusted my previous post with the right clearances, which are the standard ranges for the rod and main bearings. I think 0.002"- 0.0025" is the target. And, FYI, those are the "standard" ranges I posted, but the FSM also specifies a "limit" of 0.0035" on the rod clearance and 0.004" on main clearance.

And which King bearings did you use, the bi-metal or tri-metal ones (race bearings)?

Quote:
Originally Posted by Matt93SE
ok, just curious. I would think that would help keep oil temps down quite a bit.

What about going to a different turbo- like one of Def's babies? the T28 is a small turbo so is always high in it's useful range-- would this be dumping unnecessary heat into the system vs. a slightly larger turbo that runs more efficiently?

would forcing additional water flow to any of these turbos help keep oil temps down? or maybe an additional oil/water heat exchanger? couldn't put it immediately downstream of the turbo, but you could add one after the air-oil cooler to further cool the oil prior to going back into the engine....
I don't think this turbo will be working that hard. Here's the compressor map of a T28 derived from Garrett's "Boost Adviser" (click here) with the following input parameters:

-300 crank HP
-2.4L
-11.2 AFR (pump gas, default is 11.5:1)
-0.46 Brake Specific Fuel Consumption (Garrett default for pump gas)
-0.90 Volumetric Efficiency (Garrett default 4 valves per cylinder)
-4400 RPM Mid-Range RPM (NA KA24DE peak torque)
-5800 RPM Peak Power (NA KA24DE peak power)
-Air-Air IC with 1.5 psi pressure drop and 0.70 effectiveness
-14.0 psi barometric pressure
-90*F ambient temp

Results:
- Pressure Ratio: 1.93
- Boost gauge pressure: 11.75 psi
- Airflow: 21.09 lbs/min @ 4400 RPM, 27.8 lbs/min @ 5800 RPM
- Crank HP/TQ: 228/272 @ 4400 RPM, 300/272 @ 5800 RPM

4400 RPM & 5800 RPM points plotted on GT2560R (i.e. T28) compressor map:



I think the turbine A/R on the OEM T28 is 0.64, not 0.60 though, which means those points should move a hair to the left(?), which would be a slightly better efficiency range. With that said, I also won't be running ~12psi unless I get some forged pistons in there. But, maybe I can? I don't know....
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  #12  
Old 10-12-2016, 10:46 AM
Matt93SE Matt93SE is offline
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Based on those numbers and the peak power, where are you planning to shift? with peak power at 5800 rpm, it's going to fall off some amount but still be useful to run well into the 6000 range (I shift my KA at 6800 every shift. no dynos, but lap times and trap speeds indicate that's the way to go)...
Anyway, if you run it up to 6000 or even 65-6700 before you shift, will that be overspinning the turbo and causing it to wear faster and pump heat? or will it just lose a bit of efficiency and everything is OK?

I realize this is an enduro build and lowering peak RPM is useful for engine longevity, but there will always be those times where you want to run out that gear just a touch longer at the end of a straight or something like that...
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Old 10-12-2016, 11:02 AM
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I think your volumetric efficiency assumptions are low. That much boost will probably do closer to 300 rwhp.

No real damage possible to a small turbo with running it out at a little higher rpm than that.

The compressor housing A/R is 0.60, so the tool has the right info.
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  #14  
Old 10-12-2016, 11:16 AM
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Quote:
Originally Posted by Matt93SE View Post
Based on those numbers and the peak power, where are you planning to shift? with peak power at 5800 rpm, it's going to fall off some amount but still be useful to run well into the 6000 range (I shift my KA at 6800 every shift. no dynos, but lap times and trap speeds indicate that's the way to go)...
Anyway, if you run it up to 6000 or even 65-6700 before you shift, will that be overspinning the turbo and causing it to wear faster and pump heat? or will it just lose a bit of efficiency and everything is OK?

I realize this is an enduro build and lowering peak RPM is useful for engine longevity, but there will always be those times where you want to run out that gear just a touch longer at the end of a straight or something like that...
On our NA KA, we felt that anything passed 6500rpm felt like absolute dog **** so we all shifted around 6200-6400rpm unless it was a situation where it wasn't worth shifting and to just ride it out, i.e.-end of straight. We will probably continue to do the same thing for longevity and reliability.

Maybe it's because we had an S14 head with the 232/232 cams? With that said, we liked the feel of the S14 we had vs the replacement S13 we got, but that was an unopened, unknown compression craigslist motor vs a motor that had a recent valve lapping and cleaning and good compression.

Quote:
Originally Posted by Def
I think your volumetric efficiency assumptions are low. That much boost will probably do closer to 300 rwhp.

No real damage possible to a small turbo with running it out at a little higher rpm than that.

The compressor housing A/R is 0.60, so the tool has the right info.
What do you think is a safe bet for volumetric efficiency? Good to know on the A/R. Thanks.
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  #15  
Old 10-12-2016, 11:32 AM
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Quote:
Originally Posted by gills View Post
On our NA KA, we felt that anything passed 6500rpm felt like absolute dog **** so we all shifted around 6200-6400rpm unless it was a situation where it wasn't worth shifting and to just ride it out, i.e.-end of straight. We will probably continue to do the same thing for longevity and reliability.

Maybe it's because we had an S14 head with the 232/232 cams? With that said, we liked the feel of the S14 we had vs the replacement S13 we got, but that was an unopened, unknown compression craigslist motor vs a motor that had a recent valve lapping and cleaning and good compression..
I'm using an S14 with 248/248 cams, I/H/E. it's otherwise stock, including the ECU. the thing really doesn't even come alive until above 5000rpm, and pulls great to redline. shifting below 6200-6300 puts it below the power band on the other end so you're bogging it and losing speed, especially when you're shifting to 3rd and 5th because of the huge gaps in gearing. 3rd to 4th isn't bad though.
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Old 10-12-2016, 11:35 AM
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I think you'd be closer to 320-330 BHP at the crank at that boost level judging from KA dynos.

I think 300 BHP at the crank is closer to what an SR would be pushing at that boost.
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  #17  
Old 10-12-2016, 11:54 AM
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Quote:
Originally Posted by Matt93SE View Post
I'm using an S14 with 248/248 cams, I/H/E. it's otherwise stock, including the ECU. the thing really doesn't even come alive until above 5000rpm, and pulls great to redline. shifting below 6200-6300 puts it below the power band on the other end so you're bogging it and losing speed, especially when you're shifting to 3rd and 5th because of the huge gaps in gearing. 3rd to 4th isn't bad though.
I think we've discussed this once already, but at Watkins Glen going up the esses to the back straight, I was keeping it in 4th gear instead of shifting into 5th to make it easier to get setup for "the bus stop" and because it felt faster.

Another driver (new to Watkins Glen and wheel to wheel racing) on the team shifted into 5th gear. His lap times were approximately 7 seconds slower than mine, but he had a higher top speed by about 2 mph at the braking zone for the bus stop. Data recorded using TrackAddict app on an iPhone 5s. Whether or not that would translate into faster lap time for me remains to be seen.
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  #18  
Old 10-12-2016, 11:57 AM
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Quote:
Originally Posted by Def View Post
I think you'd be closer to 320-330 BHP at the crank at that boost level judging from KA dynos.

I think 300 BHP at the crank is closer to what an SR would be pushing at that boost.
Perhaps my pressure drop is a bit conservative as well, and I also have the ambient temperature relatively high.

I'm curious if anyone tracks a KA-T with stock pistons at this level. Where are the KA-T people at?!
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Old 10-12-2016, 12:06 PM
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Quote:
Originally Posted by gills View Post
I think we've discussed this once already, but at Watkins Glen going up the esses to the back straight, I was keeping it in 4th gear instead of shifting into 5th to make it easier to get setup for "the bus stop" and because it felt faster.

Another driver (new to Watkins Glen and wheel to wheel racing) on the team shifted into 5th gear. His lap times were approximately 7 seconds slower than mine, but he had a higher top speed by about 2 mph at the braking zone for the bus stop. Data recorded using TrackAddict app on an iPhone 5s. Whether or not that would translate into faster lap time for me remains to be seen.
I have a hard time believing a nearly stock KA can pull 5th gear with a 4.08 diff. My car with a 4.63 diff and T25 at 7-8 psi was nearly at a standstill in 5th gear, gaining about 2 mph over the whole front straight after the shift to 5th. Granted I have a little more aero drag, but my gearing is also way more aggressive.

The 7163 at ~13-14 psi can pull it no problem (top speed at TWS went from 122 to 134ish mph).
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  #20  
Old 10-12-2016, 12:09 PM
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Quote:
Originally Posted by gills View Post
Perhaps my pressure drop is a bit conservative as well, and I also have the ambient temperature relatively high.

I'm curious if anyone tracks a KA-T with stock pistons at this level. Where are the KA-T people at?!
Are you inputing the HP at the crank? I'm betting it's using that for a flow value directly.

As for engine VE. My SR with a T25 at 7-8 psi with an exhaust, FMIC, otherwise stock was at about 106-110% VE in the midrange, and it'd drop down to about 95% at redline (stock cams, S15 SR). The 7163 and Full-Race TS manifold has a midrange VE of about 115-120% at 13-14 psi, redline VE is around 102-105%. No other changes. It's pretty similar at higher boost as well, since I'm not taxing the compressor wheel at all.

This is on a not very exciting stock SR, so I tend to believe the oft quoted engine VE percentages in boost (~80-90%) are from a much earlier era of crappy engine design like the 70's and 80's.
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