Hey guys...
I'm probably going to be doing my upper timing chain soon, and while I'm at it, I was thinking of getting JWT adjustable cam gears. The reason? I have high performance camshafts in my engine that were sweet when the car was N/A but I feel they are now robbing my turbocharged car of power (9 psi...) because of their long duration/overlap. The extra lift obviously is fine. My boost starts dropping past 5k rpm, to around 7.5 psi, which i don't mind--I'd rather have less boost under the higher loads. 3k-5k seems to be my engine's sweet spot. however, at 9 psi, while it does feel fast, I don't think it has anywhere NEAR 250 rwhp (and Orion's has 248 at 8 psi). Do any of you think my high-performance cams are robbing me of power? I contacted the people who ground them (Don nimi at PDM) and he said that they'd be fine for low boost applications.
Anyway, I wouldn't bother doing this if I wasn't going to have my cam sprockets off anyhow. Do you think if I got JWT adjustable cam gears and retarded them (camshafts still confuse the hell out of me--retarding them reduces overlap/duration, correct?) that I would effectively "undo" the high=overlap/duration of the cams and make them more like stock, and therefore better suited to boost? Here's the specs of the stock vs. my cams...
STOCK 91 Cams - Intake - 207 degrees duration, .350 lift, Exhaust 215 duration, .367 lift.
Stage II PDM Cams - Intake 219 duration, .379 lift, Exhaust 221 duration, .384 lift.
As always, thanks in advance,marc
High-performance cams w/ 9 psi of boost...
-
Checkered-Member
- Posts: 1593
- Joined: Wed Sep 24, 2003 7:14 am
- Car: 1998 Nissan Altima (modded)
2003 Audi A6 2.7T (stock) - Contact:
-
littlemilla3
- Posts: 29
- Joined: Mon Oct 20, 2003 4:40 pm
High duration/lift cams will be much better than stock cams for turbo application. The cams you have still aren't very aggressive at all. The stock SR has like 250 or around there duration and people still upgrade cams in those. So basically, the cams you have now should be much better than stock cams. Turbo engines need the longer duration/higher lift to let in the more air and fuel you are adding.
-
WDRacing
- Moderator
- Posts: 15983
- Joined: Mon Nov 25, 2002 2:00 am
- Car: 95 240SX, 99 BMW 540i, 01 Chevy Express, 14 Ford Escape
- Location: MFFO
- Contact:
Well, PDM uses a different measurement to get there duration, since stock duration is 240 and they're saying its 207, thats a difference of 12 degree's on in and 14 on the ex. Do some simple math and that comes out to 252(in) and 254(ex). Personally I don't see the need to use split dur cams, but thats my opinion only. 252-254 dur cams should work perfect for any forced induction motor if the lobes are timed right. In fact, it leans more towards a midrange cam not a lowend one. 256 through 272 duration cams are widely used through the Nissan comunity in everything from RB's to the SR. The KA is no different, other then the lower rev range, which means you wouldn't really need a super long duration cam like the 272 cause you wouldn't be able to take advantage of it.
Cam gears will allow you to fine tune your timing. I've seen serious gains made from properly adjusted cams. You'll need some dyno time, but its worth it in the end.
I'm wondering why your losing boost at over 5000, the cam timing doesn't change, so your valves are still closed when should be. If you were losing boost do to overlap, you'd lose it the entire time, not just over 5000. Perhaps you have a weak WG actuator. Or perhaps your turbo is to small, what turbo are you using?
WD
Cam gears will allow you to fine tune your timing. I've seen serious gains made from properly adjusted cams. You'll need some dyno time, but its worth it in the end.
I'm wondering why your losing boost at over 5000, the cam timing doesn't change, so your valves are still closed when should be. If you were losing boost do to overlap, you'd lose it the entire time, not just over 5000. Perhaps you have a weak WG actuator. Or perhaps your turbo is to small, what turbo are you using?
WD
-
TrunkMonkey
- Posts: 3190
- Joined: Sun Aug 04, 2002 7:48 am
- Car: 2000 Lincoln Navigator
i did some digging. MarkEmark, are you still using the .48/.60 t3?
if so, here's my theory. the .48 exhaust a/r with the overlap is killing you up top. i don't think that .48 can handle the extra flow your cams are giving it.
then again, i'm against using a .48 on a KA altogether, so it may just be me.
-demetrius
if so, here's my theory. the .48 exhaust a/r with the overlap is killing you up top. i don't think that .48 can handle the extra flow your cams are giving it.
then again, i'm against using a .48 on a KA altogether, so it may just be me.
-demetrius
Yes, I'm aware that my turbo is "kinda" choking my engine past 5k...but again, i rarely take it past 5k, it's a daily driver, and the sweet spot is 3k-5k, which in my mind is perfect for me. It's at about 9 psi at 3k, 8 psi at 4.5k, and 7.5 past 5k...Therefore, it's dropping due to the size of the turbo, however, I get insane amounts of low end torque/incredibly good throttle response/very little lag and sacrifice some top-end.
So you guys think my cams are actually better than the stock KA cams for forced induction?
It's just that the times I DO bring it up to 6500 rpm, I wish there were a little more "juice" there, and I DON'T feel like replacing my turbo again (this is the third one!). Demcj, do you think if I adjusted them (again, does adjusting them allow you to reduce the overlap/duration) to a more conservative setting that I'd gain some top-end? I've often heard that cams "make or break" a turbocharged engine. I just hope I'm not braking it.
I'll be doing an upper timing chain soon---so I'd need to decide soon if I want the cam gears--JWT sells them, but I don't see themon their site. Any links of where to get them/how much they are? IIRC, I thought they were ~$120-150
So you guys think my cams are actually better than the stock KA cams for forced induction?
It's just that the times I DO bring it up to 6500 rpm, I wish there were a little more "juice" there, and I DON'T feel like replacing my turbo again (this is the third one!). Demcj, do you think if I adjusted them (again, does adjusting them allow you to reduce the overlap/duration) to a more conservative setting that I'd gain some top-end? I've often heard that cams "make or break" a turbocharged engine. I just hope I'm not braking it.
I'll be doing an upper timing chain soon---so I'd need to decide soon if I want the cam gears--JWT sells them, but I don't see themon their site. Any links of where to get them/how much they are? IIRC, I thought they were ~$120-150
-
TrunkMonkey
- Posts: 3190
- Joined: Sun Aug 04, 2002 7:48 am
- Car: 2000 Lincoln Navigator
-
WDRacing
- Moderator
- Posts: 15983
- Joined: Mon Nov 25, 2002 2:00 am
- Car: 95 240SX, 99 BMW 540i, 01 Chevy Express, 14 Ford Escape
- Location: MFFO
- Contact:
Anything over stock dur/lift would be better for a larger turbo. Stock cams would be better with a small turbo. If your running out of juice at 5000, then your pretty much done. I recomend a set of 248 ex cams from the S13. That should lift your low end grunt without losing any top end. Or simply switch back to stock.
The turbo is the big factor. Its just to small.
WD
The turbo is the big factor. Its just to small.
WD
You can reduce overlap by retarding one and advancing the other thereby turning one counter clockwise and one clockwise this means that the lobes are farther apart in the timeing of things. However, this might not be good because the piston might start compressing while it's still trying to let air in. This would be the extreme of couse.
the .63 woulcnt hurt your low end over the .48. Its still going to retain most of its charactoristics, but with the added bonus of top end power increases. The .63 stage 3 option is pertty common, and is very streetable. Many many people are using it. .48 would be okay for you if you maybe had a stage 5 wheel. But im guessing that isnt the case. and the sppol would be charactoristic of a stage 5 wheel. Wd...what do you think? Would a stage 5 .48 be about like a stage 3 .63? Also...did some say he was running a super 60? as in t3..or a 60-1 as in t04e(s)?