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Just wondering...
If for example there is a B16A VTEC, and the heads are mated to a B20 block and still revs to 8000+ rpm
But the B20 now has quad throttle intake, ported heads, larger valves etc
Would the cams still need to be upgraded? Or would the B20 with B16A cams but all the other work still generate enough power/torque at the 8000rpm mark?
You tell me. In order to accurately tell you would need a dyno. I would think, I know, but ya, more aggressive cams could create more power. But you would of course have to tune the motor and do tests. Just taking a guess!! Also what is "enough power/torque at the 8000rpm mark"? To me there is never enough.
This article might be worth a read.....
http://www.theoldone.com/archive/too...ro_on_cams.htm
i think what you are getting at is, would the stock b16a cams be restrictive, with respect to the fact that theyre designed to deal with 1.6 capacity.
i do not claim to be any sort of authority on the subject, but my feeling would be the stock cams ARE restrictive, because since the capacity is increased, you would need more lift/duration to fill a larger combustion chamber.
b18cr cams might be worth a try?
The best answer is to use some maths to calculate what your engine in theory will ingest in terms of air and then calculate what your cams and intake combination will in effect provide :)
I realise the cams would be restrictive considering the larger engine capacity
But, also considering larger valves, so 1mm lift now brings more air in/out
And ported heads etc
And when I say by enough power, I mean power will be peaking around 8000rpm instead of declining to that rpm range
spetz, theres more to it than just that the engine is larger so it will ingest more air, therefore more lift on cams etc.
Some considerations that you might want to look at that I certainly look at plus more are:
velocity of air at given rpm range, throttle body opening size, intake runner length, turbulence in the air stream, the theoretical VE (of swept volume), the amount of reversion in the exhaust side, the port shape, compression ratio, BSAC, heat/cooling affect on the air flow, the mass of air flow in regards to the tunability of the ecu, harmonic resonance, etc etc, the list continues
for example,
At a given rpm say 5000, the mass of air flow may be that the engine will ingest say x units of air. however, at 6,000 it might not be as simple as 1k rpms more so include about 1k rpms worth of air more, simply because the amount of time that the piston spends at tdc dwell (and accelerates down at a much faster speed) will not be equal as to what it would ingest at delta 2,000-3,000, therefore you have much less time to feed the air into the engine.
Some ways of adding the air in faster might be to give your cam more lift and more duration, but what does that do the lower lobe or lower rpm? another might be to advance/retard the cam timing, but that changes the window of powerband, so does this affect the higher rpm or the lower rpm adversely, ie where do you want the power?
hope i didnt rant on too much, and im abit drunk from sunday afternoon drinks, but i hope that gives you some insight to the considerations you might want to look at.
With a highly modified B20 with DOHC Vtec head...Quote:
Originally Posted by spetz
It seems a bit of a waste not to get the best from it.
As a general rule of thumb,
If the air flow of the engine remains the same (head etc)
A larger bottom end will tolerate a larger cam & give the same power charateristic of a smaller engine.
Should the cam remain smaller, the larger engine will peak sooner, running out of puff before it reaches it's potential.
my experience shows that a lot can be gained by upgrading the stock B16A cams on a B20VTEC...
even ITR cams are too small IMO, especially with porting and ITB's...
as you will have noticed with your B20, you could move the VTEC point down to under 5000rpm as it pulls harder earlier due to the combination of extra capacity and lower bore/stroke ratio...
Mr_Will,Quote:
Originally Posted by Mr_will
It's not as simple as just increase duration and height.
Think about bore and stroke of each engine. Are they comparable? Is one a stroked version of the other? Think about what gas flow characteristics are getting the best scavenging. Need x-ray specs here. You should checkout the following site that says better scavenging can be had from smaller ports. How does that fit with higher lift/duration?
http://www.mototuneusa.com/break_in_secrets.htm
hey muz, that site you quote, is that about Honda's?Quote:
Originally Posted by honest muz
http://www.mototuneusa.com/PortingAnimation.gif
does that look like a honda port to you?
and then to come up with the astounding comment:Quote:
Originally Posted by http://www.mototuneusa.com/break_in_secrets.htm
Quote:
Originally Posted by http://www.mototuneusa.com/break_in_secrets.htm
i really dont even need to tell you how useless posting that link in this forum, in response to the original question was, do I?
increase capacity means more air is needed to fill cyclinder.. so cams with higher lift and duration would work well even if std compression is used..
Tink is a perfect example.
like i said, not claiming to be an expert at all.Quote:
Originally Posted by honest muz
btw it was me who gave you that little red square :)
Thats right, small engine's with high rod/stroke ratio need cams with more overlap to take advantage of the scavenging effect, since they have low piston speeds. With a good header and exhaust system the exiting exhaust gases will create a low pressure area at the exhaust valve and if the intake valve is open at the same time the vacuum will actually help suck in the next lot of air and increase volumetric efficiency. Bigger engine's with lower rod/stroke ratios have higher piston speeds/acceleration and need cams with less overlap, or you might be able to dial some of the overlap out with a set of adjustable cam gears. If you have a bigger displacement engine with same geometry as the smaller displacement then there shouldnt be a need for a "larger" cam....Quote:
Originally Posted by honest muz
"So here we have a small engine vs. a large engine which have bore / stroke ratios that are identical at 1.14-1, and rod length to stroke ratios which were also equal at 1.75-1, so geometrically they were equal, and the cam (valve timing) identical, but the big engine didn't appear to me to need a cam with more lift or duration." -The Old One (Larry Widmer)
This is my understanding so far, correct me if Im wrong.....
my experience = ITR cams in B20VTEC = more powerQuote:
Originally Posted by ZeForce
Im sure they would and I never said otherwiseQuote:
Originally Posted by tinkerbell
http://en.wikipedia.org/wiki/SuctionQuote:
Originally Posted by claymore
Suction or to "suck" is the creation of a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.
Thanks for trying though....
lol dude your post makes no sense.....Quote:
Originally Posted by claymore
"The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area."
....this is the very definition of "suck", which means I did actually use it in the correct context and didnt need you to correct me.
If you read his post again, you will see it makes perfect sense.Quote:
Originally Posted by ZeForce
Example:
If you are in an aircraft pressurised to 10,000ft, flying at 40,000ft.
Should a hole open in the side of the aircraft,
By your thinking you are sucked from the aircraft.
In reality, you would in fact blown from it. (Greater pressure in the craft)
Though it really is a perspective thing, physics is on Claymore's side.
The same applies from global weather paterns to internal combustion engines...
(Just my 2c worth)
Also... For the previous argument with Tink
Originally Posted by tinkerbell http://www.ozhonda.com/forum/images/...s/viewpost.gif
why did honda not change cams between B16A and B18C?
They did.
Actually they didn't... Only Type R is different (in the Vtec lobe only)
Regarding the B20 with the quads etc...
Regardless of theory,
Reality is a set of larger cams will work & work really well.
No arguing, just friendly discussionQuote:
Originally Posted by TODA AU
Crower seems to disagree.... http://www.crower.com/cat/import/hon...s/b_vtec.shtmlQuote:
Originally Posted by TODA AU
With a similar set up to yours we gained 6Kw by repalcing the standard B18c cams with ITR ones then another 3Kw peak and 10kw in the midrange with a tune:)
Giday ZeForce,Quote:
Originally Posted by ZeForce
Great posts, and that needs to be said!:wave:
I don't know why some of the above posters get so antagonistic when detail gets added to a post. It's got me F^(#&@!:o
Anyway, here's a starting point for you hyper-ventilating knockers....suck it up, it's wiki!!
http://en.wikipedia.org/wiki/Harry_Ricardo
ZeForce,
Quote:
Originally Posted by tinkerbell
hmmm, probably not the same - with an engine with Variable Valve Timing and Lift Electronic Control feature...Quote:
Originally Posted by ZeForce
plus, we are comparing a B20B to a B16A...
these are not identical engines so NO the basic principles are VASTLY different:
B16A bore/stroke = 1.05
B20B bore/stroke = 0.94
B16A rod/stroke = 1.74
B20B rod/stroke = 1.53
one is "oversquare"
one is "undersquare"
simply "uncomparable" in regards to *breathing* requirements...
and since you love wikipedia -
http://en.wikipedia.org/wiki/Stroke_ratio
and regarding your crower stuff - i'd trust TODA AU over the Crower website ;)
Very true and I do actually agree. I was simply trying to point out to the thread starter that its not the increase in displacement which requires a bigger/different cam specs but in fact the change in the engines geometry....Quote:
Originally Posted by tinkerbell
Don't patronise me....Quote:
Originally Posted by tinkerbell
Check this out as well its from a completely different source.Quote:
Originally Posted by tinkerbell
http://www.myfilehut.com/userfiles/5...am%20Specs.gif
[quote=ZeForce;1080536]No arguing, just friendly discussion
Crower seems to disagree.... http://www.crower.com/cat/import/honda/cams/b_vtec.shtml[/quote]
We go by these:
Note:
B16A & B18C use same camshafts.
Also B16B & B18C Type R(00~01) share same camshafts.
Stock Integra VtiR (B18C2) / Civic VtiR 96~98 Spec / USDM Civic Si (B16A)
Int-230 duration @ 1.0mm lift / 10.6mm lift
Exh-227 duration @ 1.0mm lift / 9.4mm lift
Stock Civic EK4 VtiR '99 Spec (B16A2) / USDM DC2 GSR (B18C1)
Int-230 duration @ 1.0mm lift / 10.7mm lift
Exh-227 duration @ 1.0mm lift / 9.4mm lift
Stock Integra DC2 Type-R (1997~1999)
Int-240 duration @ 1.0mm lift / 11.5mm lift
Exh-235 duration @ 1.0mm lift / 10.5mm lift
Stock Civic EK9 Type-R & Stock Integra DC2 Type-R (2000~2001)
Int-243 duration @ 1.0mm lift / 11.5mm lift
Exh-235 duration @ 1.0mm lift / 10.5mm lift
In any case, nit picking over 0.1mm lift aside.
In reality, if you swap std cam to std cam, you will see no gain or loss in power & torque that is measureable.
If you swap to Type R cams as a minimum, you will see a gain - once on Vtec.