***Official Camshaft Thread***
09-26-2008, 07:16 PM
#1
***Official Camshaft Thread***
Key (stats apply to VTEC lobe only):
Adv dur: Advertised duration. Gives a guide to how much total duration there is but since it's not measured at a particular point there is little consistency across brands. Generally this is measured at valve closure.
Dur at .050": Duration at .050" is the duration at a specific place on the cam which allows for direct comparison across brands. When quoted for most Japanese cam designs it is duration at 1mm, which is slightly different and not comparable to .050".
Lift: Maximum lift of the cam.
Lobe centerline: Crankshaft position where the lobe is centered.
Links: Links to threads where the cams have been tested.
Important concepts
Dynamic compression ratio: The dynamic compression ratio is similar to the compression ratio in that it measures total cylinder volume against volume at top dead center. However, the measurement on dynamic CR only starts once the intake valve is closed which is after bottom dead center. The charge cannot start to compress until after the intake valve closes, so you can lose dynamic compression by having the valve close later. Static compression alone is a meaningless number. It is a maximum theoretical dynamic compression. Dynamic compression is always lower than static compression. Dynamic compression is the only thing that matters for performance.
This relates to big cams because most have longer duration which means the intake valve closes later and lowers dynamic compression. And this is why most cam manufactures recommend higher static compression ratios with their big cams.
OEM AP1 Cams
Adv. duration: 295 / 309
Dur at 1mm: 247 / 243
Lift: 12.15mm / 11.1mm
Lobe centerline: 98 deg ATDC / 100 deg BTDC
OEM AP2 Cams
**Estimates**
Dur at 0.50":
Lift: 12mm / 10.6mm
Note: The stats published on Brian Crower's website are not correct. The AP1 intake and exhaust cam both have more lift then the AP2 in VTEC. The exhaust cam has considerably more lift. The AP1 cams happen to have the same profile as the earlier model USDM Acura TSXs.
One interesting facet of the AP1 cams is that the lobes for the primary valve and the secondary valve are different sizes to promote swirl in the cylinder which increases gas mileage. However, this feature was removed from the AP2 cams because it was found to decrease power. This may be the reason some people have good experience with AP2 cams on the the AP1, below VTEC the AP2 cams are more aggressive. If you can substantially lower VTEC though, this may not be all that important.
In dyno testing I have done, the non-VTEC performance of the AP2 cams is substantially better than the AP1's, supporting the numbers.
TODA Spec A2 (IN/EX)
Advertised dur: 295 / 290
Dur at 1mm: 255 / 250
Lift: 13mm / 12mm
Lobe centerline: 100 deg ATDC / 102.5 deg BTDC
Links:
Cams on 2.4L stroker
Cams on F20C
Cams on S/C F20C
TODA Spec B
Adv. dur: 300 / 290
Lift: 13mm / 12.5mm
TODA Spec C
Adv. dur: 305 / 295
Lift: 13mm / 12.5mm
The biggest difference between the A2s and the Bs and Cs is not in the VTEC lobe but rather in the non-VTEC lobes where the the Bs and Cs have 11mm of lift as opposed to around 8mm for the A2s and OEMs. This should make non-VTEC much more aggressive but idle will suffer.
TODA VTEC Killers There are VTEC killer camshafts that have roughly the same profile as the A, B and Cs above. Basically, the primary and secondary lobes are ground the same as the VTEC lobes on the cams above and VTEC lobe is removed. The middle rocker is replaced by spacer and they sell a plate to remove the VTEC solenoid. Probably gain 1-2 HP from the simpler valvetrain and you safely rev a little higher.
Skunk2 Stage II
Adv dur: 272 / 276
Dur at .050":
Lift: 13.6mm / 12.6mm
Lobe centerline: 99 deg ATDC / 110 deg BTDC
Skunk2 Stage III
Adv dur: 278 / 282
Dur at .050":
Lift: 14mm / 13mm
Brian Crower Stage II NA
Adv dur: 310 / 308
Dur at .050": 232 / 228
Lift: 13.6mm / 13.1mm
Brian Crower Stage III NA
Adv dur: 314 / 310
Dur at .050": 244 / 240
Lift: 13.9mm / 13.8mm
CATCAMS Stage I
Adv dur: 339 / 328
Dur at 1mm: 258 / 248
Lift: 12.45mm / 11.5mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
CATCAMS Stage II
Adv dur: 351 / 340
Dur at 1mm: 266 / 256
Lift: 12.95mm / 12mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
CATCAMS Stage III
Adv dur: 362 / 352
Dur at 1mm: 274 / 264
Lift: 13.45mm / 12.5mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
All the CATCAMS have very aggressive non-VTEC lobes. In fact, the stage I CATCAMS non-VTEC lobes are about as aggressive as the AP1 VTEC lobes (only 1mm less life on the intake, exhaust is about the same). It's unclear how effective this is.
TODA Cam Gears
Cam gears are used to change the cam center either to the left (advance) or right (retard). Typically advancing the center of the cam moves the TQ curve higher in the RPM range and retarding it moves it lower. However, sometimes the entire curve is improved depending on the cam combination. By advancing one cam and retarding the other, you can create overlap which usually increases TQ on an NA car up to a certain point.
About 5 degrees of overlap is the most that should be run so their is no chance of the valves hitting each other. Similarly, 4 degrees of advance should be considered the maximum for the intake so the valves don't hit the pistons. These are conservative estimates; however I clayed the motor and with the AP2 pistons and the F22 crank I was able to get about +7 advance on the intake while keeping adequate clearances. The exhaust cam doesn't have much of any clearance issue with the stock cams. I have also calculated that overlap can likely be run up to 8 degrees, however I have not tried quite that much physically. Anyone that runs more than 5 degrees of overlap or 4 degrees of advance should degree the camshafts to make sure the cam gears are positioned the way they are marked (meaning when you set the gear to +4, it's actually +4).
One of the best ways to increase the dynamic CR is to use a cam gear on the intake side to enable the valve to close sooner. A stock F22C produces a dynamic CR (assuming the intake valve closes at 47.5 deg ABDC, which is close) of 9.8:1. With a cam gear advanced to +5, the same motor would produce a dynamic CR of about 10.1:1. For comparison, without cam gears a Spoon HG would produce a dynamic CR of 9.97:1. The Spoon HG gains CR but has an offset of less dynamic CR because it retards the intake camshaft.
As the numbers show, the cheapest and easiest way to gain effective (dynamic) CR is with cam gears.
Cam Gear Dyno
Although I don't have a specific dyno to post, my experience with the cam gears is very similar to the above dyno after testing the gears on the dyno for the better part of 3 hours with two different setups. On the AP2, the motor likes a lot of intake advance and 4+ degrees of overlap.
Adv dur: Advertised duration. Gives a guide to how much total duration there is but since it's not measured at a particular point there is little consistency across brands. Generally this is measured at valve closure.
Dur at .050": Duration at .050" is the duration at a specific place on the cam which allows for direct comparison across brands. When quoted for most Japanese cam designs it is duration at 1mm, which is slightly different and not comparable to .050".
Lift: Maximum lift of the cam.
Lobe centerline: Crankshaft position where the lobe is centered.
Links: Links to threads where the cams have been tested.
Important concepts
Dynamic compression ratio: The dynamic compression ratio is similar to the compression ratio in that it measures total cylinder volume against volume at top dead center. However, the measurement on dynamic CR only starts once the intake valve is closed which is after bottom dead center. The charge cannot start to compress until after the intake valve closes, so you can lose dynamic compression by having the valve close later. Static compression alone is a meaningless number. It is a maximum theoretical dynamic compression. Dynamic compression is always lower than static compression. Dynamic compression is the only thing that matters for performance.
This relates to big cams because most have longer duration which means the intake valve closes later and lowers dynamic compression. And this is why most cam manufactures recommend higher static compression ratios with their big cams.
OEM AP1 Cams
Adv. duration: 295 / 309
Dur at 1mm: 247 / 243
Lift: 12.15mm / 11.1mm
Lobe centerline: 98 deg ATDC / 100 deg BTDC
OEM AP2 Cams
**Estimates**
Dur at 0.50":
Lift: 12mm / 10.6mm
Note: The stats published on Brian Crower's website are not correct. The AP1 intake and exhaust cam both have more lift then the AP2 in VTEC. The exhaust cam has considerably more lift. The AP1 cams happen to have the same profile as the earlier model USDM Acura TSXs.
One interesting facet of the AP1 cams is that the lobes for the primary valve and the secondary valve are different sizes to promote swirl in the cylinder which increases gas mileage. However, this feature was removed from the AP2 cams because it was found to decrease power. This may be the reason some people have good experience with AP2 cams on the the AP1, below VTEC the AP2 cams are more aggressive. If you can substantially lower VTEC though, this may not be all that important.
In dyno testing I have done, the non-VTEC performance of the AP2 cams is substantially better than the AP1's, supporting the numbers.
TODA Spec A2 (IN/EX)
Advertised dur: 295 / 290
Dur at 1mm: 255 / 250
Lift: 13mm / 12mm
Lobe centerline: 100 deg ATDC / 102.5 deg BTDC
Links:
Cams on 2.4L stroker
Cams on F20C
Cams on S/C F20C
TODA Spec B
Adv. dur: 300 / 290
Lift: 13mm / 12.5mm
TODA Spec C
Adv. dur: 305 / 295
Lift: 13mm / 12.5mm
The biggest difference between the A2s and the Bs and Cs is not in the VTEC lobe but rather in the non-VTEC lobes where the the Bs and Cs have 11mm of lift as opposed to around 8mm for the A2s and OEMs. This should make non-VTEC much more aggressive but idle will suffer.
TODA VTEC Killers There are VTEC killer camshafts that have roughly the same profile as the A, B and Cs above. Basically, the primary and secondary lobes are ground the same as the VTEC lobes on the cams above and VTEC lobe is removed. The middle rocker is replaced by spacer and they sell a plate to remove the VTEC solenoid. Probably gain 1-2 HP from the simpler valvetrain and you safely rev a little higher.
Skunk2 Stage II
Adv dur: 272 / 276
Dur at .050":
Lift: 13.6mm / 12.6mm
Lobe centerline: 99 deg ATDC / 110 deg BTDC
Skunk2 Stage III
Adv dur: 278 / 282
Dur at .050":
Lift: 14mm / 13mm
Brian Crower Stage II NA
Adv dur: 310 / 308
Dur at .050": 232 / 228
Lift: 13.6mm / 13.1mm
Brian Crower Stage III NA
Adv dur: 314 / 310
Dur at .050": 244 / 240
Lift: 13.9mm / 13.8mm
CATCAMS Stage I
Adv dur: 339 / 328
Dur at 1mm: 258 / 248
Lift: 12.45mm / 11.5mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
CATCAMS Stage II
Adv dur: 351 / 340
Dur at 1mm: 266 / 256
Lift: 12.95mm / 12mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
CATCAMS Stage III
Adv dur: 362 / 352
Dur at 1mm: 274 / 264
Lift: 13.45mm / 12.5mm
Lobe centerline: 104 deg ATDC / 100 deg BTDC
All the CATCAMS have very aggressive non-VTEC lobes. In fact, the stage I CATCAMS non-VTEC lobes are about as aggressive as the AP1 VTEC lobes (only 1mm less life on the intake, exhaust is about the same). It's unclear how effective this is.
TODA Cam Gears
Cam gears are used to change the cam center either to the left (advance) or right (retard). Typically advancing the center of the cam moves the TQ curve higher in the RPM range and retarding it moves it lower. However, sometimes the entire curve is improved depending on the cam combination. By advancing one cam and retarding the other, you can create overlap which usually increases TQ on an NA car up to a certain point.
About 5 degrees of overlap is the most that should be run so their is no chance of the valves hitting each other. Similarly, 4 degrees of advance should be considered the maximum for the intake so the valves don't hit the pistons. These are conservative estimates; however I clayed the motor and with the AP2 pistons and the F22 crank I was able to get about +7 advance on the intake while keeping adequate clearances. The exhaust cam doesn't have much of any clearance issue with the stock cams. I have also calculated that overlap can likely be run up to 8 degrees, however I have not tried quite that much physically. Anyone that runs more than 5 degrees of overlap or 4 degrees of advance should degree the camshafts to make sure the cam gears are positioned the way they are marked (meaning when you set the gear to +4, it's actually +4).
One of the best ways to increase the dynamic CR is to use a cam gear on the intake side to enable the valve to close sooner. A stock F22C produces a dynamic CR (assuming the intake valve closes at 47.5 deg ABDC, which is close) of 9.8:1. With a cam gear advanced to +5, the same motor would produce a dynamic CR of about 10.1:1. For comparison, without cam gears a Spoon HG would produce a dynamic CR of 9.97:1. The Spoon HG gains CR but has an offset of less dynamic CR because it retards the intake camshaft.
As the numbers show, the cheapest and easiest way to gain effective (dynamic) CR is with cam gears.
Cam Gear Dyno
Although I don't have a specific dyno to post, my experience with the cam gears is very similar to the above dyno after testing the gears on the dyno for the better part of 3 hours with two different setups. On the AP2, the motor likes a lot of intake advance and 4+ degrees of overlap.
Trending Topics
09-28-2008, 01:29 PM
#9
Registered User
This should become a very good thread once it's gets a bit more information. I may be able to supply some info on the hytech cams within a month or two if all goes well...
