[Bisimoto]

I have been bombarded with questions on the exchange capability of D16Z6 cams, both stock and aftermarket, in the recently popular D15B JDM Vtec engines. Instead of boring you with the grim details, here are some highlights:

• D15B and D16Z6 have the exact same cam profiles on the primary and secondary intake lobes
• The share the same exhaust profiles
• THEY DO NOT SHARE THE SAME LOBE SEPARATION
• The intake lobes do not share the same reference opening and closing numbers in relation to keyway centrelines. Same goes for the exhaust.
• The intake lobes are significantly retarded in the D15B vtec engines in comparison to the D16Z6.
• The D15B exhaust lobes are slightly retarded in comparison to the Z6.

There is little wonder on the nice power capability of the D15B, despite the displacement "handicap".
I hope that helps, as it helped me a bunch in forcing me to design newer cams for the D15B JDM engines, and the JDM ZC vtec.

 

[DougNuts]

[*]The intake lobes do not share the same reference opening and closing numbers in relation to keyway centrelines. Same goes for the exhaust.

Are they 4.5 degrees off, or in other words, the difference between a z6 and y8 cam gear keyway?

I assume the d15b vtec cam has less lob separation than the z6?

Thanks Bisi

 

[Dominus]

'Bisi all the way FTW...!!!!!!!!!
I have no doub your Level 3 will work great on my Z6 Vtec...:bigok:
I'll post my nbrs when I've been finished my build.
Hurry up with the V2 header please...!!!

 

[Bisimoto]

Doug, not 4.5 off, but unique to the D15B. The intake is retarded as must as 16 crank degrees, and the exhaust in the 10 crank degree range. The cam gear requirements are the same as the D16A6~Z6.

 

[DougNuts]

Doug, not 4.5 off, but unique to the D15B. The intake is retarded as must as 16 crank degrees, and the exhaust in the 10 crank degree range. The cam gear requirements are the same as the D16A6~Z6.

Got ya, but when putting a z6 cam into a d15b block, the y8 gear got all my timing marks to line up..........

I'm now concerned about what my cam is really timed at.

I can fix it by putting the d15b cam back in. Which cam is better for boost? I assume the D15b has less LSA, but probably not enough to worry about loosing power in a boosted application?

 

[cervan]

Do you know what the stock power difference is? and if for a turbo engine (stock cams and heads) What camshaft in a z6 head you would net you more power?

Since both lobes intake/exhaust are retarded, does that mean it has less overlap?

 

[DougNuts]

Since both lobes intake/exhaust are retarded, does that mean it has less overlap?

Not necessarily. I think he meant they were retarded in relation to the cam keyway, which means more high RPM power. However, if I'm reading this right, the D15b cam does have 6* more LSA, which seems like a big difference to me. If I'm on the right track, the D15b cam is much better for boost, and all around power. Bisi explained the angles in relation to the keyway, but not in relation to the z6 cam, so my assumptions are just that, assumptions. :redface:

A little summary I found via google -

More Lobe Separation: Wider powerband, more peak power, smoother idle

Less Lobe Separation: Increased mid-range torque, faster acceleration, narrower powerband

More Duration: Powerband moved higher in rpm range

Less Duration: More low-end torque

More Overlap: Improved signal to carburetor, lower fuel efficiency, potential for reversion

Less Overlap: Improved low-rpm responsiveness, better fuel efficiency, engine may run hotter

 

[Hellhatch]

Great info good to know.

 

[lemon_juice]

what im getting from this is...using an adjustable cam gear alone wont reap the full benifit of the d16z6 cam in a d15b...as it would apposed to having the proper d15b cam.

is this correct?

also, i just recently purchased and installed your d16z6 camshaft(stage 2) in my d15b, even had it running for a little whiles now...my question is, would it be worth it to change over to your new d15b cam(stage 2)? also, is there an exchange we would be able to do?

 

[Bisimoto]

Great questions,
Stock to stock, the D15B cam is superior to the D16A6 due to lobe separation differences.
For boost, stock to stock, the D15B would still be better.
For boost, to reap the best performance, a Bisimoto level 1.2 Z6 or D15B cam is much better.
If you already have a D16Z6 Bisimoto cam in your D15B, it would not be worth the upgrade unless you want an extra 6-8 calculated horses or so at low boost.
Unfortunately, I have not instituted an exchange program.
Thanks for the kind words all.

 

[DougNuts]

The intake is retarded as must as 16 crank degrees, and the exhaust in the 10 crank degree range. The cam gear requirements are the same as the D16A6~Z6.

You didn't say if that was in relation to the keyway or to the z6 cam.

if I'm reading this right, the D15b cam does have 6* more LSA, which seems like a big difference to me.

I think I was incorrect here. Bisi said crank degrees, which means half of my guess of 6*, or 3* more LSA because the cam spins 1* for every 2 crank degrees. However, I'm not sure what the above quoted numbers are referenced from, my assumption is the z6 cam.

Bisi - the next thing I'm trying to wrap my head around is z6 vs. D15b cam on the two different deck height of blocks. Since the cam gear requirements are the same, am I to assume that there is no worries in cam timing when swapping cams around? If that were the case, wouldn't you design all your d-series cams around the "retarded" D15b design, or does the cam need more advance (read: less retard) as displacement goes up?

 

[transzex]

The lobe separation differences is due to engine stroke and how it effects cylinder filling.

 

[Chrisfrom1986]

How does an adjustable cam gear affect things? I have a skunk2 gear on my D15B, getting things timed correctly with that is probably going to be a pain in the ass without much knowledge about it.

 

[jimmyb34]

great info bisi, glad to see somebody finally took the time to spec these out

 

[Bisimoto]

It is painfully obvious that Honda wanted to extract more power from lower displacement...hence the cam design. All of the timing woes would be eliminated if enthusiasts degreed their cams in...it would not matter what cam or gear used. Maybe I should put a video out on how to do it!

Greetings, Sir Bone!

 

[DougNuts]

All of the timing woes would be eliminated if enthusiasts degreed their cams in...it would not matter what cam or gear used. Maybe I should put a video out on how to do it!

Yes! That would be great!

 

[highlift]

It is painfully obvious that Honda wanted to extract more power from lower displacement...hence the cam design. All of the timing woes would be eliminated if enthusiasts degreed their cams in...it would not matter what cam or gear used. Maybe I should put a video out on how to do it!

Greetings, Sir Bone!

PLEASE DO!!!!!!!!! :bigok:

 

[transzex]

It is painfully obvious that Honda wanted to extract more power from lower displacement...hence the cam design. All of the timing woes would be eliminated if enthusiasts degreed their cams in...it would not matter what cam or gear used. Maybe I should put a video out on how to do it!

Greetings, Sir Bone!

I might do a webcam event with a tranny rebuild.

Sir Bisi, would you even wanna try to explain the lobe separation timing and how it is effected by the different strokes?

Long stroke = better vacuum signal, therefore later intake valve opening can occur.

Read up on some V8 info, quite alot to read about. Engine builds start with the cam design IMFO.

 

[DougNuts]

Bone, that's like posting up a picture of naked girl and telling a teenager he now knows how to have sex.

 

[transzex]

Then you need to start reading.