INTHERED

I have the IC Magnacharger on my 2000 A4 would the CompCam
1.85 rockerarms be worth adding for some extra RWHP ?

ICULUKN-C5

I would say change the cam to a blower cam and you will see more of an increase.

Chris@East Coast Supercharging

I would rather install a blower cam. You will see better results

INTHERED

I do not have the cash or skill to do the blower cam install plus I think
the cam has issues that would require a whole new tune. I was hoping
that the rockers would give me maybe 10 hp and only require a minor
tweek to my existing tune all of which I could handle myself. Does 10
hp sound reasonable or should I just stick with what I have ?

Thanks >>>>> Mike

STAGED

I think after reading all posts and connecting the dots, a good blower cam will give 25-35 rwhp +/- peak and higher ratio rockers about 10 rwhp peak +/-.

But in real world performance gains the A4 ratio spacing requires 10-15% shifts above peak power rpms to make the most out of the powerband (after all, one doesn't shift at 5200 rpms on a stock LS1 or 6000 rpms on a Z06 to get best times).

With a blower cam and Mag. combo on stock stroke, you'll likely make above the shiftpoint and at the rev cut of 6500 to 6700 rpms. But with high ratio rockers, peak power may be around 6000 rpms. Even with high ratio rockers, it's still tough to pull off that 10-15% above power peak rpm shiftpoint rule.

Conclusion: On the dyno you'll see justification of the blower cam purchase. But in real world track results where it matters how the powerband is utilized, one may see small differences relative to the differences in labor costs between rocker ratio changes vs. cam swap. In other words, with a rocker ratio change, you'll probably get 60-70% of the track performance benefits at 30% of the installed price.

Also if you have a good tune now, all you need with the ratio change is to extend the rev limit and do just minor double checking of the calibration at the near rev cut portion of the powerband. By contrast a cam swap (depending on blower cam) will require a full remap plus some cold-start enrichment and closed loop mode retuning.

It's a cost-benefit argument. Now if you plan to go more aggressive on blower drive ratios while keeping stock compression ratios, then a cam swap is an obvious choice because it has the side benefit of keeping boost vs. compression at safe for pump gas levels. If I do a cam swap, then I highly recommend a modest blower speed-up at the same time; you'll keep the boost level same but you'll really get a good bang for the buck. Even though you still won't fully utilize the powerband with the peak power pegged at the rev cut, the blower speed-up will fortify low to mid-range torque a lot, which automatic cars can benefit from a lot.

Ragtop_Rob

From what I understand, just adding the different rockers makes a large increase in valve train stress (more so than going with comparable cam mimicking the same change) - it changes the strike angle to the lobe and does not seat the same. Also - there is no accurate way to just tweak a tune, either you are on a wideband or not, and are monitoring the motor or not. If you are looking for a few hp have you considered a different pulley for your mag (nothing radical, maybe a 3.3") or an alcohol kit that you install and get tuned when you can (again just my understanding) you will pick up power just by running the kit (and they are only around $400.00.

Just my thoughts

STAGED

Great point. I was talking about performance vs. cost. But the durability and geometry compromises are important and good to mention. A valvetrain simulator would be necessary to put the final word on comparative loads. Although I usually associate minor increases in ratios to be trouble-free; in fact I've never run across a post of broken valvetrain parts on just ratio increases but I've run into plenty of broken spring/parts issues with cam swaps.

INTHERED

The car already has a 3.3 and I do have an LM1 A/F meter as well as
a Predator that I use as a scan tool. I thought the roller tip on the
CompCam 1.85 roller rockers made the valve train stress a non issue.

auctiondepot

I wouldn’t do it.

I'd bet real money that you'd lose power! Because... a positive displacement blower fixes the airflow relative to RPM, so if you increase valving during the overlap more air will escape without replacement and with less mass for combustion, this event will be richer.

but then again I could be wrong

STAGED

Blowers certainly can take a small or sub-standard motor and provide heroic output levels. Even if there's a drop in boost from modification of valve events and/or cylinder heads the gains in airflow and power on Mag.'d C5s are proven. At the very least, there's less hp lost in turning the blower for given airflow and one can always increasing timing.

LS1s are seriously cam limited engines and gains can be had with increases in gross valve lift, tighter LSA (to some degree), and increased duration. Higher ratio rockers clearly increase lift and increase the effective overlap even if LSA remains the same. Blower cams generally keep LSA same to a moderate tightening to prevent excessive fresh charge loss, plus they offer substantial increases in duration and lift. Thinking of the cam limitations on stock LS1s, I imagine the first few dozen thousands of gross valve lift will clearly help a lot. Then for every thousandth increase valve lift, there's will be diminishing returns. Yet blower cams generally increase gross valve lift at 2-4 times the increase seen in higher ratio rockers.

I think it's worth a shot to stick with higher ratio rockers (while it may be a BORDERLINE call on NA). There may be small losses or no gains down very low in the rpm band but the copious amounts of volume a Mag. moves from down low anyhow, one will quickly see modest gains and MOST IMPORTANTLY GAINS THAT CAN BE FULLY REALIZED ON THE STREET/TRACK.

Blower cam route is clearly the best, but I think cost-benefit higher ratio rockers alone are fine. Only problem is down the road if you want more power and want to add a bigger cam, your choices of cams along with that higher ratio rocker are much more limited.

auctiondepot

So would you like to put some money on it?
for a 1.85 rocker arm only with no tuning.

STAGED

Not on one car/one case, but over many cars for a statistical conclusion, yes. I say this because for a particular case, the pre-high ratio rocker install dyno/track test could've been in great conditions and different dyno/track enough to absorb the small gains. So it's got to be averaged out over several cases.

Note it's not just high ratio rockers, it's got to have strong valvesprings (but one doesn't need to set valve seating forces too high as with a bigger cam...which saves a tiny bit in friction). There are NA bolt-on modded C5s posting up to 17 rwhp peak gains with higher ratio rockers and spring upgrades.

This Mag'd LSx simulates a larger cube motor. And we all know larger cube motors are hungry for cams with lots of lift not to mention lots of total duration. Higher ratio rockers help the lift part of the equation.

Another example, the '01 LS6 motor has hp/torque gains over the LS1 from numerous sources including higher CR, better venting, better heads, better exhaust, etc. But numerous sources state the cam was one of the biggest contributors (which the '02+ LS6 expanded on further). The difference between the '01 LS6 cam and '01 LS1 cams is mainly lift (and barely duration or LSA) AND WE KNOW the tangible differences stock, NA modded or boosted between those motors with consideration of other contributions to the LS6 advantage. Going to higher ratio roller rockers would contribute in the similar manner an '01 LS6 cam provides over an '01 LS1 cam which is statistical and OEM proof that LS1 cams have lift numbers that clearly limit more performance and something higher ratio rockers can help alleviate with relatively few drawbacks and *installed* cost.

As I said and everybody knows, these LS motors are so cam limited that adding lift and/or duration will add up to real gains BOOSTED OR NOT; even when not squeezing down too much on LSA. Higher ratio rockers help in the lift part and very modestly increase *effective* overlap area w/o decreasing the actual LSA.

All I'm saying is that higher ratio rockers cost relatively little installed and the gains are small but definitive and one can utilize all of those gains onto the road as it should not shift peak power rpms up much if at all. Blower cam upgrades are ideal and they give fairly broadband increases, but note it'll cost a lot more installed/tuned and it'll be tough to fully realize the upper rpm gains as I've observed 346cid Mag+blower cam combos pegging peak power at the rev cut. There's nothing wrong with making more and more power till the rev cut, it's just tough to make the most out of the power curve in a step-wise transmission unless one shifts 10-15% above peak power rpms.