100WHP by installing an N52 exhaust cam in an N55.
- Thread starter 9krpmrx8
- Start date
When duration info is provided you need to state at what lift this duration is measured.
The N54 exhaust cam has 241 +/- 2 degrees at 0.005" lift on the cam, not on the valve.
The N52 and N53 exhaust cam has 254 +/- 2 degrees at 0.005" lift on the cam.
If you send me the N55 exhaust cam, I can measure duration directly off the cam itself with my setup. Also, if you have an extra N55 roller arm, I would like to measure it myself and compare it to a N54 roller arm.
I was going to bring the head and each cam to a local machine shop to plot. Price is just not worth it for such a minimal mod. Unless someone wants to throw me a couple hundred bucks lol... It's only .3mm more lift-- a 3% increase. In regard to the roller, the math to deduce the ratio really is pretty simple. Not much room for error there unless my digital caliper is way off lol. I would send you a roller but I'd prefer to have the entire set to sell. the part numbers for the N55 roller is different if that helps support that it has a higher ratio. N52, N53, N54 owners might want to look at installing N55 rollers...
Within the context of this thread (PS2 turbo), it is speculated that EMAP is very high. Some are even saying there is exhaust valve float but I see no evidence of that... I would say is that earlier exhaust valve opening and increased lift can't really make up for poor exhaust flow. If true the above is true, the increased duration and overlap from the N52 cam would probably actually reduce top end power while gaining nothing from the extra lift. VANOS can only adjust in one direction from what I see as well so you can't negate the additional overlap.
Less overlap in these situations would actually be more desirable. Again this is just speculation based on what people have said recently about exhaust manifold pressure with a hybrid turbo like a PS2. The benefits of this cam would be seen more on freer flowing setups... ported head, bigger turbo, freer flowing exhaust manifold... Even at that, you would probably still be talking marginal gains from just swapping in an N52 exhaust cam. Like single digit whp...
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That statement is false. You can open the exhaust valve 5-10 degrees earlier and close the valve at the same or 2-3 degree later and get lots of top end. It is all about reducing pumping loss and you can help this by opening the exhaust valve several degree earlier to achieve more power. This is where the duration on the exhaust cam comes into play.
I understand that, but, you're talking about an n52 cam swap not a custom cam... these are symetrical cams. If you're getting into lift sooner you're also going to be staying in lift longer, or am I off base with that statement?
All N52, N54, N53 cams have asymmetrical cam profiles, this was validated when I measured them. Even visually I can tell that they are asymmetrical, so I did not need to use any equipment to come to this conclusion. I'm 100% confident that the N55 cam is also assymetrical, based on the fact that 99+% of all cam profiles from all OEM since the late 90s are assymetrical.
The N52 and N53 exhaust cam has more duration than the N54 exhaust cam see post #162.
FYI, google "mikeseli cams" let me know if you have any other questions.
Ok getting all defensive... not sure where to even start with this response. Not a single number you've posted thus far has been correct so I'm not sure what you've measured... all you've posted is assumptions that appear to be incorrect. And I think your comments now about symmetry are just as much of an assumption that you're supporting with name dropping. Not much worth googling from what I've seen so far...
I've posted the n54 cam profile, per frankenturbos plot, and the n55 profile, per the bmw academy docs (click my google drive link). Maybe someone like yourself with more experience can point out the difference in ramp rates? With the naked eye, and also looking at those cam graphs, I see pretty symmetrical curves and lobes. What exactly is it that you've seen and measured that you're alluding to?? Are you trying to say that the n52 cam wont increase overlap? That it has a less aggressive closing ramp or something? Just not sure what you're trying to say... and I dont have an n52 cam profile to look at that you might be basing your assumptions off of.
Yes, I think we covered already that n52 cam has slightly more duration than an n54 cam. 2* per bmw. No one needs to measure anything to know that much.
I dont have any info on the n53 cam but please share what you have... the point was that putting the n52 cam into an n55 to capitalize on the 3%/.3mm marginal increase in lift is also going to result in even more than that 2* additional duration. Duration and overlap not being good things within the context of the hybrid turbo ps2 and as evidenced by the dyno that saw no tangible gains at 6200rpm+.
Please provide more context to your post. We're all just trying to work through how we can take advantage of these part swaps.
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Wow, where have I been?
Bnks334 and mikeseli contributions are very helpful.
I have 4 exhaust cams.
Used N52, N54, N55
New 'russian' sourced N52
I sent them out and had than all 'cam doctored'.
From all of this, what I find most interesting is the different part numbers for the N52 and N55 rockers. It would be great of the N55 rockers were higher ratio than the N52.
So if that is the case, I believe there is some merit to these power gains with using the N52 cam in the N55 engine.
This will add +0.3mm lift and +1* duration just from the N55 rockers with more ratio. Add that to the slight increase in the N52 duration, maybe you see +0.3mm exhaust valve lift and ?+5-7* duration.
This additional lift and duration using the N52 cam and N55 rockers would not add much peak power but will extend the powerband. That is exactly what is seen especially above 5000rpm. This makes for more power under the curve and more top end pulling power.
Yeah I call BS on +90-100 hp gains when the 'gain' is when compared to the stock drop off in power above 5000rpm.
If in fact that N55 rockers are 1.72:1 compared to the N52 1.66:1, I might just swap in a set of the N55 rockers into my N52 engine. Costs about $200 for +0.3mm lift and 1* duration on a N52.
I can post all my cam data sheets if need be.
Bnks334 and mikeseli contributions are very helpful.
I have 4 exhaust cams.
Used N52, N54, N55
New 'russian' sourced N52
I sent them out and had than all 'cam doctored'.
From all of this, what I find most interesting is the different part numbers for the N52 and N55 rockers. It would be great of the N55 rockers were higher ratio than the N52.
So if that is the case, I believe there is some merit to these power gains with using the N52 cam in the N55 engine.
This will add +0.3mm lift and +1* duration just from the N55 rockers with more ratio. Add that to the slight increase in the N52 duration, maybe you see +0.3mm exhaust valve lift and ?+5-7* duration.
This additional lift and duration using the N52 cam and N55 rockers would not add much peak power but will extend the powerband. That is exactly what is seen especially above 5000rpm. This makes for more power under the curve and more top end pulling power.
Yeah I call BS on +90-100 hp gains when the 'gain' is when compared to the stock drop off in power above 5000rpm.
If in fact that N55 rockers are 1.72:1 compared to the N52 1.66:1, I might just swap in a set of the N55 rockers into my N52 engine. Costs about $200 for +0.3mm lift and 1* duration on a N52.
I can post all my cam data sheets if need be.
The main issue with the comparison for me was that the "after" is about the same as most other ps2 pushing 23 psi at 5000rpm. That and the logs show a less than stellar "before" tune. So, we started asking questions about what the n52 cam might actually be doing. A few basics measurements and it's easy to see why an n55 cam wont be beneficial in other engines. And it's much easier to speculate how the n52 cam affect an n55.
The one other thought is the drop off in power after 4800rpm on the stock cam N55 is due to valve float.
With the N52 cam and N55 rockers and the additional 0.3mm lift, that brings the valve spring closer to 'binding' and this decreases the harmonicsof the valve spring and this in and of itself will decrease/delay valve float another 5-800rpm and thus extend the power curve.
With the N52 cam and N55 rockers and the additional 0.3mm lift, that brings the valve spring closer to 'binding' and this decreases the harmonicsof the valve spring and this in and of itself will decrease/delay valve float another 5-800rpm and thus extend the power curve.
Yeah I cant get on board with any of that... this resonates to that old thread with "headgames" on bimmerpost that was pure nonsense. If anything, the additional lift would move you closer to valve float. Pushing the spring further outside of its useable stroke means less control over the valve.
N52 cam is really just not a big change and the additional overlap is probably detrimental in this specific application. I'm going to roll with that unless someone has more info.
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Yeah there is no way we are getting exhaust valve float. I still doubt intake float from Headgames post. I also think opening earlier/closing later would hurt on a PS2 with high back pressure. Just think, you are trying to push against 50+psi of exhaust gas pressure. You want the exhaust valves to close asap before the intake valves open and you push exhaust gases into the intake. On a stage 3 turbo with minimal back pressure, yes it will help there.
IIRC the valve springs are the same as for the N/A N52.
Now in the N55 with more than stock boost, 20+ psi, without upgrading the valve springs, they will not be able to control the valve.
Now in the N55 with more than stock boost, 20+ psi, without upgrading the valve springs, they will not be able to control the valve.
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