272/272 cam timing test and tune
Originally Posted by vividracing3
264/272 or 272/272 The 272/272 combo runs perfect but let me give some hints here. First the point of timing gears: when a factory cam is produced it has to fall into certain specs one of which is the centerline of the lobe (intake 71deg BBDC Exh 70 ABDC I got these specs from the factory manual) upon installation of an after market cam it is best to use a deg wheel to check that the cam falls into these specs you would be surprised how often an after market cam's centerline is off 3 or 4 deg +/-. So the idea of adjustable cam gears is to bring the centerline back to factory spec. If the ecu is properly tuned at this point you should have minimal to no idle isues. I've installed a few sets of 272/272 and gotten good results. Now as for advancing or retarding a cam past the centerline that depends on what the car is being used for example: advancing an intake cam for example will increase low end power and equally decrease top end power
Last edited by evo 8 ya; Sep 9, 2004 at 01:16 PM.
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From: Phoenix
Originally Posted by Ted B
I agree, but it seems the long duration of the 272s may be such that the resulting long period of overlap becomes a detriment when the cams are installed and adjusted to the factory settings. This seems to be supported by the fact that those who have tested the various cam configurations report better average power with one cam being of shorter duration (264). If the long overlap of the 272s is such that a sigificant portion of the fuel charge is being pushed through the exhaust valve, this will sap some of the factory turbo's ability to keep the system pressurized, and no ECU tuning can fix it.
However, with much area under the lobe (e.g. 272), one should be able to dial out some of the overlap, which will restore idle qualities and improve low and midrange power without sacrificing top end. This seems consistent with what those who have done this have reported. Ultimately, the single most important event is the point at which the intake valve closes, so the point at which retarding the intake valve further compromise average power is perhaps the most important to note.
However, with much area under the lobe (e.g. 272), one should be able to dial out some of the overlap, which will restore idle qualities and improve low and midrange power without sacrificing top end. This seems consistent with what those who have done this have reported. Ultimately, the single most important event is the point at which the intake valve closes, so the point at which retarding the intake valve further compromise average power is perhaps the most important to note.
As for what settings to use (-4, -2) the only way to properly set up your cam gears is to put a deg wheel on them and find out if their centerline is correct if so you would set them both to 0 then very minimal fuel tunning is needed if they are off set the cam gears to bring your centerline back to factory spec
Oh one major thing I forgot about when picking your cams "valve lift" since the cam lobe sits off from the top of the valve on a off center roller there is a difference between the cam lobe lift and valve lift(take note of this when picking how much lift a cam has) I will be flowing an unported factory head in the next week or so and I will post the results on the optimum valve lift unless someone else has those numbers on hand
Last edited by vividracing3; Sep 9, 2004 at 04:15 PM.
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From: Lima - Peru
BTW when trying to set the timing with the HKS cam gears, it says on the instruction that each small mark (line) is 2 degs, so basically to get the suggested -4i and -1e, u would have to go 2 small lines anticlockwise on the intake and half a small line anticlockwise on the exhaust wheel ?
just installed my 272/272 yesterday with fidanza adjustable cam gears. the fidanza's have 12 white dashes going in each direction. each nick is 1deg. I have mine set at -5intake -2 exhaust. i will be trying the -4/-2 tomorrow. all i can say is wow! cams are the biggest difference i have done with my car. the top end is there now. i can't wait to take it back to the track and see what it does
chiraoka, I am unfamiliar with the HKS cam gears, sorry to let you down. I went and did some tuning last night. On an uphill I did my first run with the cam gears at -5/-2 and s-afc set at +6% across the board for high throttle. My low end was at +13%. I started out at 9.4 sec 40-100. After a couple of adjustments I settled in (for now) with -4/-2 and +3% fuel on the high end. My high throttle is set at 80% and my low throttle is set at 35%.
I think whats holding me back a little right now is I had a dyno flash with boost controller, catback, intake, injectors and fuel pump. I know have these other mods, but since my computer was already set for the prior mods, I can't maximize anything. I'm also runnign stock I/C pipe, which is pretty crappy as we all know. My BR upper I/C should be in tomorrow. I'm sure with a proper tune I can get my car to about 6.8 40-100.
I think whats holding me back a little right now is I had a dyno flash with boost controller, catback, intake, injectors and fuel pump. I know have these other mods, but since my computer was already set for the prior mods, I can't maximize anything. I'm also runnign stock I/C pipe, which is pretty crappy as we all know. My BR upper I/C should be in tomorrow. I'm sure with a proper tune I can get my car to about 6.8 40-100.
Wow, this is a long thread.......
Just got my 272's installed Monday along with Fidanza cam gears. Did a little research and found this thread.
Started at 0/0 and the power is evident. Didn't have the top end power I imagined but pulled hard. The idle was a little lopey. Then went to -4/-1 and the idle smoothed out. Can still tell their there, but a nice idle. Took it out on the highway to check it out....OMG! Pulls strong through 5k and let just pulls even harder.
I had a buddy that dyno'd and got max power out of +1/-1. Tried this for a day. Talk about a rough idle. Good power....starts around 4k...but seems to level off around 6k. And it seems to attract the police
So needles to say I went back to the -4/-1.....it pulls harder and makes for a great seat of the pants experience
Just got my 272's installed Monday along with Fidanza cam gears. Did a little research and found this thread.
Started at 0/0 and the power is evident. Didn't have the top end power I imagined but pulled hard. The idle was a little lopey. Then went to -4/-1 and the idle smoothed out. Can still tell their there, but a nice idle. Took it out on the highway to check it out....OMG! Pulls strong through 5k and let just pulls even harder.
I had a buddy that dyno'd and got max power out of +1/-1. Tried this for a day. Talk about a rough idle. Good power....starts around 4k...but seems to level off around 6k. And it seems to attract the police
So needles to say I went back to the -4/-1.....it pulls harder and makes for a great seat of the pants experience
Last edited by cooliodb; Dec 12, 2005 at 02:15 AM.
