100WHP by installing an N52 exhaust cam in an N55.

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Bnks334

Sergeant
Dec 1, 2016
397
New York
Yeah there is no way we are getting exhaust valve float. I still doubt intake float from Headgames post.
They were literally pointing to perfectly normal looking valves as support lol.

My stock turbo and now my ps1 must be causing valve float too. They both taper up top.
 

CobraMarty

Lurker
Jun 2, 2019
11
'Valve float' is genericly used for any and all valve and valvetrain instability, etc.

I have yet to see stock n/a valve springs/pressures work at anything over mild low boost and over 5500rpm.
High boost, over 10-12psi and definitely 20+psi and over 5500rpm nearly always requires heavier valve springs, intake and exhaust.
 

Bnks334

Sergeant
Dec 1, 2016
397
New York
'Valve float' is genericly used for any and all valve and valvetrain instability, etc.

I have yet to see stock n/a valve springs/pressures work at anything over mild low boost and over 5500rpm.
High boost, over 10-12psi and definitely 20+psi and over 5500rpm nearly always requires heavier valve springs, intake and exhaust.
10 years into the platform and 800whp+ cars on stock valve train and now stock tune boost levels are causing valve float at 5500rpm+? I think I'll respectfully bow out of this thread now lol.

Instead of accepting that the n52 cam is a very small change to more or less an inconsequential phase of power production we're now talking about valve float...
 
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Weehe

Specialist
May 21, 2019
68
'Valve float' is genericly used for any and all valve and valvetrain instability, etc.

I have yet to see stock n/a valve springs/pressures work at anything over mild low boost and over 5500rpm.
High boost, over 10-12psi and definitely 20+psi and over 5500rpm nearly always requires heavier valve springs, intake and exhaust.
I honestly want to see what data is out there that shows this.
 

CobraMarty

Lurker
Jun 2, 2019
11
The N52 is optimized for economy and emissions.
It shares the same intake and exhaust valve springs as the N55, a performance based engine especially when compared to the N52.

So why does the N55 use the same light valve springs for the naturally aspirated N52?

How can these springs be adequate when running 20+psi?

What is the seat pressure and the 9.7mm valve lift pressure?
 

Bnks334

Sergeant
Dec 1, 2016
397
New York
The N52 is optimized for economy and emissions.
It shares the same intake and exhaust valve springs as the N55, a performance based engine especially when compared to the N52.

So why does the N55 use the same light valve springs for the naturally aspirated N52?

How can these springs be adequate when running 20+psi?

What is the seat pressure and the 9.7mm valve lift pressure?
Maybe your thought process should be the complete opposite? The n52 uses heavy than necessary springs from a boosted application (parts sharing reduces cost). There is also the weight of the valvetrain to factor in. N55 uses lightweight valves.

This conversation has played out in 100 other forums before this. I lean toward boost just doesnt play as important of a roll in required spring pressure like people have rumored... people have written books saying it's basically just internet bs. Hard to find actual sae whitepapers on this specific situation. But bmw has been lightening the valvetrain and running softer springs on several engines that have made 1000whp+ with stock valvetrain and 30psi+... within that context, upgraded valve springs result in <30whp gains. What again are we saying is evidence of valve float within the context of this thread? Because .3mm lift on an exhaust cam showed 0 gains?
 
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CobraMarty

Lurker
Jun 2, 2019
11
The N52 predates the N55 engine by nearly 8 years.
The N52 does not have heavy springs. If you knew the seat pressure and 9.7mm lift pressure you would know.

Manufactures know and intentionally use lighter springs for economy and limit top end power and rpm for longevity and reliability and warranty reasons.

Light weight valves and retainers are great, they can use even lighter springs. Good for econobox not so good for high boost performance engines.

Look what all the top professional engine builders use and how they build their engines.

Still would like to see this N52 cam swap done on another N55 engine to see if output/gains are replicated.
 

Bnks334

Sergeant
Dec 1, 2016
397
New York
The N52 predates the N55 engine by nearly 8 years.
Does it predate the n54?

The N52 does not have heavy springs. If you knew the seat pressure and 9.7mm lift pressure you would know.
I dont. All the people who have sold valvetrain mods for this platform and none have published any actual info. I know the s55 valve spring rate because it was posted by Dinan and then repeated by others also selling valvetrain upgrades for the s55.

None of what you said is really a rebuttal to what I wrote so not much else to say.

If valve float is a big concern for you then why are you selling milvs?
 
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mikeseli

Specialist
May 23, 2017
96
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.
Take another look at Frankenturbo info, do you spot the mistakes, some info is correct but some is incorrect? They have rocker ratio as 1.5 and this gives wrong valve lift info.

Did you notice that the N54 exhaust cam has a duration of about 243.X degrees at 0.004", did you see what I stated : I stated " 241+/- 2 degrees at 0.005"
I've spotted Webcams mistake on what you shared, do you question this?
Rocker ratio being 1.64 or 1.66 how does this change anything. 5.9mm cam lift x 1.64 = 9.68mm valve lift, while if we use 1.66 we get 9.79mm. 0.11mm difference (we are arguing over 0.11mm??? that is the thickness of a loose leaf paper, is that a difference worth an argument, that can be easily attributed to so many factors. I measure the rocker ratio from the rocker itself with my precise Mitutoyo tools. Maybe others measured by comparing the valve lift vs the cam lift, again the lifter may be or may not be primed creating questionable info.

Do you know what an assymetrical cam is? take a closer look at the Frankenturbo graphs "you" provided, look closely at lifts below 0.020" do you see the difference between the opening and closing part of the curve? If not, look closer. The closing side of the curve is extremely important if you wish to increase revs on the engine. Slowing down the rate at closing allows for valve float control.

Are you aware that we can control overlap with VANOS timing from the exhaust cam OR also from the intake and exhaust cam?

The N52 exhaust cam is an excellent cam swap on the N55 and N54, I recommend others try it if you have access to a tuner than can adjust Vanos.
The 100whp statement is very very questionable, but I'm sure you can achieve 40-50whp gains if you're boosting around 15-20psi.
I'm still questioning the rocker ratio difference between the N55 and other Nseries cars so I just placed an order and will confirm my conclusion.
 

Bnks334

Sergeant
Dec 1, 2016
397
New York
I didn't share a thing from "webcam." myself and others replied to point out that data was incorrect. Further, Frankenturbo has n54 roller ratio as 1.667. They showed 9.65mm of valve lift a hair off bmw's advertised lift of 9.7mm. What are you looking at? CobraMarty also has it at 1.66. Didn't read the rest of your post... All I see is generic statements about vanos tuning. When I made my post I was pointing out that the n55 roller ratio has to be different when you were assuming it to be the same... Not sure what point you're trying to make.

Lets fact check this post too though... I have not measured an N54 cam but I trust that CobraMarty did when he claimed that lobe lift is .230in, or 5.842mm. 5.842 * 1.64 = 9.58 lift. 5.842 * 1.66 = 9.7. That is .12mm difference in lift. More important though is that your numbers are wrong, again, and now you're trying to downplay their significance at the same time as promoting gains from just as small of a difference provided by the N52 cam swap lol... so confusing. Are you rounding wrong or something to come up with these numbers? You're a cam guy that wants to say .3mm is significant but .12mm is ahhhhhh whatever just a small rounding error....

The opening and closing ramp of these cams is such a small proportion of the duration that it is not even relevant. The cams are symmetrical for all intents and purposes. A small delay in closing the exhaust valve at <1mm lift is not what most people would refer to as "asymmetry" in a cam. I am intentionally using logical words like "most" to leave this open to debate as this is not being said specific to anything that has been posted. You have yet to tell us how this applies to the context of the n52 and n55 cam swap.

Now lets get back to facts... what does n54 cam profile, as plotted by frankenturbo, have to do with me saying the N55 cam is symmetrical? #1 that plot isn't perfect. #2 it's for an n54 cam and not an N55 or an N52. #3 BMW literally gave us the N55 profile and I shared it in my google drive link. The plot of the N55 cam ramps look symmetrical to me. As does the lobe lift duration of both opening and closing events. I am talking about the actual lobe not a small difference in ramp area to close the valve more softly (if what you're saying is even applicable since we dont have the plot to review).
 
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CobraMarty

Lurker
Jun 2, 2019
11
Most all of my research and work has been on the valvetronic intake side. Here all N52, N55 and S55 have the same valve springs, rocker arms and same support/MILVS part. Rocker ratio, to the best I can come up with, is 1.66:1.

The exhaust side is different. Searching realoem, the N52 has different rocker arms then the N55/S55(which are the same).
N52 and N55 have the same Valve springs. S55 is different.

IIRK, from my original measurements and research, the N52
stock intake valve springs have 60psi seat and 157psi at 9.7mm.
N52, N55 and S55 all use the same intake valve springs and rockers.
Upgraded springs are 90psi seat and 190-235psi at 10mm.

Exhaust valve springs for the N52 and N55 are the same. They are different from the intake valve springs. IDK their specs. I haven't measured them.

The real truth is there are a lot of unknowns.
Share any specs you might have.
 
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