This isn't for a Honda, sorry. However, the Honda community is far more advanced when it comes to such as this than the Focus and Mazdaspeed communities so I'm coming to you guys for help. I apologize if it should be in the other automotive tech but I just felt it would get more exposure here and be more related.
I have two sets of cams here and am back and forth about which one would be better for this turbo build. A little background on the build...
Ford Duratec 2.0L DOHC 4 cylinder
3.44" (87.5mm) bore x 3.27" (83.1mm) stroke
10.0:1 static compression
Wiseco forged aluminum pistons w/ valve reliefs on the intake side
K1 H-beam forged steel rods
Stock cast crank
Ported 2.3L head (flows ~250 CFM @ .300", ~280 CFM @ .400", ~300 CFM @ .500")
Crower dual valve springs
FSWerks log-style T25 turbo manifold
Garrett GTX2867R (.86 a/r internal-gated hot side)
3" bellmouth downpipe to 3" exhaust
Cosworth short runner intake manifold
Water/meth injection (50/50 mix) w/ 2 nozzles; 1 before the turbo and another halfway between the turbo and the intercooler
Redline at 7,500rpm (for longevity)
This is mated to a MTX-75 5-speed manual transaxle with an Exedy stage 3 hyper-single clutch, heat treated gears and input shaft, FRPP torsen-type LSD, and FRPP 4.06 final drive gear.
I want a good compromise of power and lope from the cam choice. This will be a street car that will see the track for 11.50 index from time to time. The max I'll be pushing this small turbo is 20-22psi as that will already be getting out of the compressor's efficiency. I'm looking for 380-400whp and 340-360wtq but a broad and useful powerband between 4,500-7,500rpm is more important than peak numbers.
The 2 sets of cams I have sitting here are both NA cams...
Crane PN: 224-0010
212˚ / 204˚ @ .050" lift
.374" / .354" total valve lift
110 LSA
Lobe Centerlines @ 110˚ / 110˚
Overlap: -12˚ @ .050" lift
Crane PN: 224-0014
236˚ / 226˚ @ .050" lift
.435" / .410" total valve lift
110 LSA
Lobe Centerlines @ 110˚ / 110˚
Overlap: 11˚ @ .050" lift
I'm currently running the smaller 224-0010 cams with a GT28RS at 12psi on the stock motor and it makes good power in the mid-range but wants to fall on it's face above about 6,800rpm. The idle is a little too smooth for my taste also. The 224-0014 cams have a nice, lopey idle but with that much overlap, I worry that they'd cause a bit of reversion with the restrictive T25 hotside and actually do more harm than good to the powerband.
I've considered a couple different things that would meet these two in the middle. The first is regrinding the 224-0014 intake cam down to meet the specs of the exhaust cam for an even split of duration and lift with the exhaust cam advanced a few degrees to raise the LSA.
Custom regrind #1
226˚ / 226˚ @ .050" lift
.410" / .410" total valve lift
112 LSA
Lobe Centerlines @ 110˚ / 114˚
Overlap: 2˚ @ .050" lift
^What concerns me about this is possibly having the exhaust valve open too early at 47˚ BBDC causing an incomplete burn in the cylinder and adding more heat to an already backed up turbine. It would be considerably less overlap however and would probably have a nice, mild lope to the idle also.
Another idea I had was regrinding the 224-0014 exhaust cam down and pairing with the 224-0010 intake cam for a forward split duration combo.
Custom regrind #2
212˚ / 216˚ @ .050" lift
.374" / .385" total valve lift
108 LSA
Lobe Centerlines @ 106˚ / 110˚
Overlap: -2˚ @ .050" lift
^^^The bigger exhaust side would help out the powerband in higher rpm but probably wouldn't give the idle I'd be looking for. Here's a third option I've considered is a reverse split duration regrind.
Custom regrind #3
224˚ / 220˚ @ .050" lift
.420" / .400" total valve lift
110 LSA
Lobe Centerlines @ 108˚ / 112˚
Overlap: -2˚ @ .050" lift
^^^This would provide the same low overlap but with a wider duration and possibly a better powerband. I'm not sure how the exhaust opening and intake closing events may effect the engine's performance though.
I'm looking for insight into this. What amount of overlap is acceptable with a restrictive small turbo before you start to lose power? Does a higher or lower LSA yield better results? Does a restrictive hot side favor a forward split duration or reverse split? Thanks in advance for any advice. I've been wrecking my brain trying to fully understand this.
I have two sets of cams here and am back and forth about which one would be better for this turbo build. A little background on the build...
Ford Duratec 2.0L DOHC 4 cylinder
3.44" (87.5mm) bore x 3.27" (83.1mm) stroke
10.0:1 static compression
Wiseco forged aluminum pistons w/ valve reliefs on the intake side
K1 H-beam forged steel rods
Stock cast crank
Ported 2.3L head (flows ~250 CFM @ .300", ~280 CFM @ .400", ~300 CFM @ .500")
Crower dual valve springs
FSWerks log-style T25 turbo manifold
Garrett GTX2867R (.86 a/r internal-gated hot side)
3" bellmouth downpipe to 3" exhaust
Cosworth short runner intake manifold
Water/meth injection (50/50 mix) w/ 2 nozzles; 1 before the turbo and another halfway between the turbo and the intercooler
Redline at 7,500rpm (for longevity)
This is mated to a MTX-75 5-speed manual transaxle with an Exedy stage 3 hyper-single clutch, heat treated gears and input shaft, FRPP torsen-type LSD, and FRPP 4.06 final drive gear.
I want a good compromise of power and lope from the cam choice. This will be a street car that will see the track for 11.50 index from time to time. The max I'll be pushing this small turbo is 20-22psi as that will already be getting out of the compressor's efficiency. I'm looking for 380-400whp and 340-360wtq but a broad and useful powerband between 4,500-7,500rpm is more important than peak numbers.
The 2 sets of cams I have sitting here are both NA cams...
Crane PN: 224-0010
212˚ / 204˚ @ .050" lift
.374" / .354" total valve lift
110 LSA
Lobe Centerlines @ 110˚ / 110˚
Overlap: -12˚ @ .050" lift
Crane PN: 224-0014
236˚ / 226˚ @ .050" lift
.435" / .410" total valve lift
110 LSA
Lobe Centerlines @ 110˚ / 110˚
Overlap: 11˚ @ .050" lift
I'm currently running the smaller 224-0010 cams with a GT28RS at 12psi on the stock motor and it makes good power in the mid-range but wants to fall on it's face above about 6,800rpm. The idle is a little too smooth for my taste also. The 224-0014 cams have a nice, lopey idle but with that much overlap, I worry that they'd cause a bit of reversion with the restrictive T25 hotside and actually do more harm than good to the powerband.
I've considered a couple different things that would meet these two in the middle. The first is regrinding the 224-0014 intake cam down to meet the specs of the exhaust cam for an even split of duration and lift with the exhaust cam advanced a few degrees to raise the LSA.
Custom regrind #1
226˚ / 226˚ @ .050" lift
.410" / .410" total valve lift
112 LSA
Lobe Centerlines @ 110˚ / 114˚
Overlap: 2˚ @ .050" lift
^What concerns me about this is possibly having the exhaust valve open too early at 47˚ BBDC causing an incomplete burn in the cylinder and adding more heat to an already backed up turbine. It would be considerably less overlap however and would probably have a nice, mild lope to the idle also.
Another idea I had was regrinding the 224-0014 exhaust cam down and pairing with the 224-0010 intake cam for a forward split duration combo.
Custom regrind #2
212˚ / 216˚ @ .050" lift
.374" / .385" total valve lift
108 LSA
Lobe Centerlines @ 106˚ / 110˚
Overlap: -2˚ @ .050" lift
^^^The bigger exhaust side would help out the powerband in higher rpm but probably wouldn't give the idle I'd be looking for. Here's a third option I've considered is a reverse split duration regrind.
Custom regrind #3
224˚ / 220˚ @ .050" lift
.420" / .400" total valve lift
110 LSA
Lobe Centerlines @ 108˚ / 112˚
Overlap: -2˚ @ .050" lift
^^^This would provide the same low overlap but with a wider duration and possibly a better powerband. I'm not sure how the exhaust opening and intake closing events may effect the engine's performance though.
I'm looking for insight into this. What amount of overlap is acceptable with a restrictive small turbo before you start to lose power? Does a higher or lower LSA yield better results? Does a restrictive hot side favor a forward split duration or reverse split? Thanks in advance for any advice. I've been wrecking my brain trying to fully understand this.
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