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My specs should have 59 degrees of overlap at .006 and 7 degrees at .050.
this is more than say (for example) a torquer v2 at .006 and the same at .050
That being said, it should thump pretty hard!
"lope" was the absolute LAST determining factor when I picked a cam, but it's sort of nice that you can have your cake and eat it too as I hope this cam will have the same output and better manners than most big "thumpy" cams. even if I spread out the LSA to a 113, it would still have 3 degrees @ .050. not bad
Tang how does yours sound at idle? If my math is right, it has -.5 degrees at .050, no idea about at .006. Does it qualify as more of a "sleeper" cam or do you definitely know its there?
I have my idle set at 825, and you can definitely tell there is a cam in there. With the cutout closed it sounds fairly tame, but with the cutout open it gets into a nice rhythm that shakes the car pretty good.
Here is a video of the idle at 850rpm with no cutout, which is what it was before my last tune.
I hear ya, but Corsa sounds great IMO, so it's no big loss. I've heard it's somewhat common for a car to feel a little slower with the cutout open, but in all reality it's just the lack of backpressure. You should make a couple more hp up top with it open
Yeah, I'm sure you're right. The car definitely made more peak power and torque with it open. I think some of it is mental as well. It's so loud when open, even at lower RPM's, that it feels like I should be going faster than I am
One other thing I would suggest is to give Geoff Skinner at EPS a call. He was with Thunder Racing when they developed the TR227, TR230, and even a lesser known TR236, which was said to be a stud! Here's a quote from him on it back then:
"The cam is 236/230 .590/.570 so it is still a reverse split with an intake closing point the same as the TR 230. This cam is basically designed to have the same power band as the 230...just more of it. Heads that have been milled .005" should be fine."
Cam you spec'd has more overlap than I'd want for a real DD that will drive super nice. It'll have plenty of mid range though. Seems like there's better choices out there with less overlap that will drive nicer and make more power. You have a 3200 stall so being concerned about power off idle or low rpm is pretty moot.
Seems like there's better choices out there with less overlap that will drive nicer and make more power.
I would offer that one of the big reasons that cam he proposes will make good power is because it has a relatively early intake valve open event. If you take that away trying to reduce overlap, I think you will lose power.
That amount of overlap is also a large proponent as to why it should continue to pull into the upper rpm range rather than falling off. The cylinder scavenging will help pull in the intake charge. Not too much, not too little. At least that was my reasoning.
I would offer that one of the big reasons that cam he proposes will make good power is because it has a relatively early intake valve open event. If you take that away trying to reduce overlap, I think you will lose power.
All I'm getting at is I think there are better choices that give you the "have your cake and eat it too". I have similar mods to the OP with a Futral F13 and the torque is table top, it'll pull to 6500 if I want it to (which I don't), and with 3 degree's of overlap it drives excellent regardless of temperature. On a stalled A4, I'm not sure what the expected bottom end torque advantage is going to be for that reverse split.
So you're saying you'd recommend a Futral f13 over what I've spec'd out?
Why do you think mine wouldn't pull that hard up top?
Don't you think i'd be going against the whole goal here if I reduced intake duration and increased exhaust duration. I know that conventional split cams will get the job done for sure, and the're very popular, but I just don't think that necessarily means best.
If not the F13, then what would you change, and more importantly, why would you change it.
That amount of overlap is also a large proponent as to why it should continue to pull into the upper rpm range rather than falling off. The cylinder scavenging will help pull in the intake charge. Not too much, not too little. At least that was my reasoning.
That theory is correct, but you do need to take a look at the size of the exhaust valve and how well the exhaust ports flow. With my setup, I'm experiencing "over-scavenging". My exhaust valve size is 1.575 and the flow numbers on the exhaust side are really high, and because of the valve events of my cam, the setup is over-scavenging really bad up top which is causing power to fall off right around 6,000 rpm's.
Factory limiter is 6200. I don't plan on spinning any more than 6500 and that'll be on rare occasion. I feel 7° won't over-scavenge but may leave a tad more to be needed up top yet.
Even if I do fall off slightly at 6000, I think the area under the curve should make up for it.
I'll probably set up my tune to start shift points at wot around 5900rpm anyway. Ballpark a 200rpm execution time, and I should be just fine. Maybe I'll up that on track days
Factory limiter is 6200. I don't plan on spinning any more than 6500 and that'll be on rare occasion. I feel 7° won't over-scavenge but may leave a tad more to be needed up top yet.
Even if I do fall off slightly at 6000, I think the area under the curve should make up for it.
I'll probably set up my tune to start shift points at wot around 5900rpm anyway. Ballpark a 200rpm execution time, and I should be just fine. Maybe I'll up that on track days
I agree that you will have not issues at all with over-scavenging, given you are running stock/unported heads. Honestly, there are only a few heads out there that have exhaust flow numbers like mine. AFR and Tony Mamo's new MAMO Motorsport heads are the only ones I've seen that have exhaust flow numbers like mine. I did not experience this problem until I switched from 1 3/4" headers to 1 7/8" headers. I picked up somewhere around 15 to 17 rwhp/rwtq under the curve, but with the added exhaust flow, it absolutely petered out around 6,000 rpm's and continued to drastically fall off after that.
I'm glad you think I hit the mark. My heads are definitely not badass enough to have the same types of issues AFR's or Mamo's heads will. For me, and other guys with stock heads like me, I think this should work. If I had some kickass cnc ported, oversized valve, flow-monster heads, I'd definitely have a different cam spec'd out.
So you're saying you'd recommend a Futral f13 over what I've spec'd out?
Why do you think mine wouldn't pull that hard up top?
Don't you think i'd be going against the whole goal here if I reduced intake duration and increased exhaust duration. I know that conventional split cams will get the job done for sure, and the're very popular, but I just don't think that necessarily means best.
If not the F13, then what would you change, and more importantly, why would you change it.
My experience with reverse splits is they usually make great low end power and peak early and fall off hard. And a lower LSA usually lowers the powerband and narrows it. So a reverse split with a low LSA both seem like they would make it more of a truck cam for towing. I guess to me, your original post and goals and what you're saying now dont match. But hell, why not try it.
Sorry speedtiger...looks like I breezed right past your question. With a .041 compressed thickness, 3.90 bore gasket, i believe the math works out to almost exactly 10.3:1
ddnspider, what is your experience? have you run one and weren't real fond of it?
Looking at the graph from tang, his doesn't start to fall off until after 6500 from the looks of it. My specs are a little tighter on the lsa, but also have more duration on the intake side, and just a tad more exhaust side which should allow it to breathe just fine up top.
ddnspider, what is your experience? have you run one and weren't real fond of it?
Looking at the graph from tang, his doesn't start to fall off until after 6500 from the looks of it. My specs are a little tighter on the lsa, but also have more duration on the intake side, and just a tad more exhaust side which should allow it to breathe just fine up top.
Yes I've ran a 226/222 on a 115. It made great under the curve power, but really started to nose over above 6k. Also, just my preference, I don't like to see dyno graphs on a 20/100 scale for something N/A "only" making 3-500hp. I'd like to see that graph rescaled on a 10/50 scale or something smaller. It gives you a better idea of where it actually peaks and where it really noses over. Everything looks better when you "zoom out". Your LSA is lower so I imagined it would peak sooner than Tang, thats all.
Last edited by ddnspider; Jun 8, 2016 at 04:34 PM.
Here's a graph of a 230/224 on a 111. It just keeps pulling. This was through midlength headers with a cutout. I think the added duration will help crutch the top end, allowing enough air to keep things spinning. But at the same time, the early open and close of the intake valve will do a lot of good for the torque down low.
I'm far from an expert, but I try to rationally and logically think of the "how's" and "whys" and that's what I'm trying to explain here. Ultimately Trying to learn, not teach.
If my logic is flawed, or if there's an important point I'm missing, let me know!https://imgur.com/EHJTTzF
Last edited by speedtigger; Jun 8, 2016 at 11:13 AM.
Reason: embeded image
Thats a nice looking graph, what were the rest of the mods on that setup? Looks like it does carry nice, but also has less overlap and duration than your original post
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