Patrick G

iTrader: (14)

Typically, I recommend a 44-46 degree IVC for best power under the curve in a 346, but to do that makes the power peak at 6300, which is higher than some people like to twist their motors. For a true daily-driven A4 or M6 that wants a little more low end torque, I'll back it up to 42 degrees (like you mentioned).

But in Ragtop's situation, he specifically detailed that he wanted a 6000 rpm shift point. Knowing that, he'll need his peak power to occur at 5800 rpm. To accomplish that, he'll need an IVC of 38 degrees. While Joel will be leaving quite a bit of power on the table above 5500 rpm, this clearly doesn't seem to be of concern, hence the recommendation for the earlier intake valve closing point.

PREDATOR-Z

Yeah, that is what I figured. I guess you didn't quite read my post carefully because I had specified 6100 rpm shiftpoints and that was why I came up with 39 IVC (5800/5850 peak {guess}).

I thought I was going bananas, but I stuck to my decision. ( But I was doubting my understanding)

Anycase all is well, the cam is ground and I'm awaiting $$$ for heads.

Ragtop 99

iTrader: (7)

For a car that needs good top end, IVC = 42* is the minimum I'd do. I'd also look for and EVO in the high 40s or or more unless the exhaust is really free flowing. I need the car to slice through traffic with fast throttle response at low rpm so I'm trading off the above 5500 rpm power.

When I was an A4, I did the opposite. I had a big stall and went for an IVC = 48 and made goobs of power up top. Since I never went over 1/3 throttle below 4000 rpm, I didn't care about low end torque.

I was looking at an IVC = 40 until I started looking at the stock F-Body cams and thought more about DAB's 224/224 110 106 which also used a 38* IVC.

PREDATOR-Z

When I put my cam specs together I looked at 3 cam types.
Vinci /Crane (low trq >38* IVC)
GM LS6 (compatibility with stock exhaust- Large intake/exht split-emissions)
CheaTR cam (power made and EVO)
So this cam was born.

RevGTO

iTrader: (12)

Patrick, Ragtop, et al., do you think this OMC/XE-R lobe combo would bring a lot more to the table than a 214/224 XE on a 110 or 111 ICL? Maximum valvetrain reliability is a concern, but also, the best power under the curve. Also, do y'all agree that keeping rpms at 6000 & below is important for A4 longevity? All this plays into cam selection for a DD.

Patrick G

iTrader: (14)

RPM is one of the biggest killer for 4L60Es. You can put 600 rwhp to a stock 4L60E and if you shift it at 5500 rpm, it will last a long time. But a 350 rwhp motor shifted at 6800 will tear one up in a short time. Been there, done that. Joel and Predator-Z are saavy enthusiasts and know the pitfalls that come with a motor turning lots of rpm. For maximum street miles, it's best to shift the 4L60E at or below 6000 rpm.

The OMC/XE-R lobe combo is probably about the most hell-for-stout combination you can run for a pure street car, but keep in mind, the ramps are pretty aggressive. Proper spring choice and setup is key to ensuring long life. For best power under the curve, I highly recommend LSK lobes first, then OMC lobes, then XE-R lobes. For longer spring life and less valvetrain noise, the Comp XE lobes along with the Crane lobes are very nice. Cams are all about compromise. The 215 OMC lobe just happens to be around the best balance of power, driveability and longevity that I've found.

I would not recommend a 110 or 111 LSA for a motor running stock exhaust manifolds because it would either have too much overlap (causing nasty reversion) or the duration would be too small to keep the overlap in check. As outlined in post #1 and #2, you want to limit overlap at .050" to -5 degrees if possible. -10 is better in fact.

RevGTO

iTrader: (12)

Very good - thanks. I think I'm getting my parameters straight. Just for the record, I was inquiring about the difference between the two cams assuming a 114 LSA on a 110 or 111 ICL .

Patrick G

iTrader: (14)

Sorry, missed that. I was reading too fast.

yellergto

How much longer spring life/less power would the XE lobes give you vs. the OMC/XE-R combo assuming similar specs?

Patrick G

iTrader: (14)

Hard to say. I just know that when properly set up, 40k miles on OMC lobes are no problem with PP/PRC/Manley duals shimmed to within .050" of coil bind. Doing this eliminates spring surge and adds to the life of the spring.

Ragtop 99

iTrader: (7)

Rev:
There's a pretty big difference between the OMC lobe and an XE. Maybe Patrick has the difference in total lobe area from a cam doctor report. The XE-R compared to the XE gives you more than just lift. It is faster off the seat, so you get more duration all through the lobe for a given amount of total overlap. Reducing the total overlap can improve idle and low throttle driving Here's an example holding total duration constant:

..........total
Lobe...duration...05....200
XE......277.......224....142
XER....277.......228.....149

As you can see, there is a nice pickup starting at .05, 5% more duration at .200, and by .300 there is a much more pronounced increase on a percentage basis.

BTW, with your 3000 stall, you can use an IVC a little later than what I'm looking at and have good performance. the 214/224 114 straight up or 1* advance should get you off the line and preserve your top end a little more.

Patrick G

iTrader: (14)

Here's another comparison. Look at the duration at .200", then look at the total duration (at .006):

..........total
Lobe...duration...05....200
OMC...265.......215....142
XER....269.......220....143
XE......277......224.....142

So as you can see, the Thunder Racing 215 OMC lobe has as much duration at .200" lift as a Comp XE lobe with 224 duration. This is one of the reasons why the CheaTR cam and Old Man Cams make so much power. Lots of area under the curve with very little advertised duration.

RevGTO

iTrader: (12)

I realize that the steeper ramp rates of the OMC and XE-R mean more than just higher maximum lift - and that means more potential power per valve event than a lazier lobe of the same duration. But again, I'm balancing that positive against the potential negative effect on spring life. Running duals would address that problem, but I'd prefer to run 918's for a number of reasons. I'm looking at practical and low maintenance for DD operation. And for the same reason, the IVC of 38 is related to maintaining my 6000 shiftpoint.

Ragtop 99

iTrader: (7)

Even if you want to shift at 6000, you may be better off with an IVC = 40. You may find that you still get more area under the curve. Certainly after the 1-2 upshift, you'll be better off. You might put the cam in with an adjustible chain and experiment.

SideStep

PREDATOR-Z

Isn't that relative to IVO as well?

I looked at an "old" favorite all around cam. The venerable 216/220 114+4.
That one is on a 38 IVC

216/220, .525/.532 114+4

IVO>-2
IVC>38
EVO>48
EVC>-8
ECL>118
OVERLAP>-10

I used that cam and it was really good from idle till 6300 with headers(obvious by EVO being early), I got 397rwhp with MTI ported LS1 heads, bolt ons in my 99 M6.
Point being the trq curve was phenominal for those lobes.

yellergto

So, the shimming to within .050 of coil bind is more important that the open/closed pressure of the springs? I ask because TR has the CheaTR listed with crane 832 duals on its website, but those springs have less seat pressure at 1.80 installed height than the rest of the springs you list.

RevGTO

iTrader: (12)

Splitting the difference between you and Patrick, I end where I started - 214/224 114+2. It's just another one of the trade-offs involved in this kind of decision. On the one hand, you hate to choose cam specs that leave easy potential power on the table; and yet, on the other hand, having a cam where you shift before it peaks would be lame. So when you are committed to keeping your rpm band moderate, you are trying to find the best possible position between those two pitfalls. But I suppose one degree of difference each in IVO/IVC is not going to be the end of the world one way or another. Predator's 216/220 shows that pretty clearly.

Ragtop 99

iTrader: (7)

I've always been impressed that you made 400 rwhp with that cam and S1 heads. I've haven't seen too many repeat that with those soft lobes. You had it dialed in right.

My only point is that with his stall, mild as it is, he may run faster by using an IVC = 40 if it gives him a little higher average torque from 3500 - 6000 rpm at the expense of power below 2500 rpm. Hence the suggestion of an adjustible timing chain.

CHRISPY

this thread is an oldie but a goodie

Say you have a stock stalled 2.73-3.23 geared A4.

What cam specs would you recommend with a peak power of 5800 and 6000rpm shift point. 11:1 compression, stock exhaust manifolds and stock cats? Maximum power under the curve, great idle (700rpm) and emissions legal.