why bother going bigger than 264's?

[flubyux2]

Edit: i should have said "bigger than 264's"...

i mean... whats the point?

according to HKS' dyno graphs of their own cams, i dont see much of an appreciable difference between going bigger than 264's. this is all in reference to the 2J, but the 7M is still a 24v, 3.0liter setup. the bore/stroke and rod ratio isnt that relavant of a difference between the two. the only main difference would be the VE of the two. however a stock 7M and a stock 2J (gte) differs only by about 25cfm at the highest flow rating... so whatever the 2jzgte does, the 7m is only a step behind and with a power band shortened by ~1000rpm (stock for stock).

so, that said... the 256's made an improvment, and then the 264's expounded on this improvment. however, the 272's lost low end and didnt yeild an improvment on the top end...

im only worried about TQ since thats a directly correlation to the VE curve of the motors themselves... but check it out:

alot of you are going to cite variables in valve size, intake manifolds, compression ratio, exhaust manifold, turbo size, boost level, fuel type, conditions or anything else... im not focusing on that. im simply talking about how a motor will react to the "benchmark" for aftermarket cams with all other aspects being equal.

 

[Reign_Maker]

Thread title fix'd for you...

 

[flubyux2]

thanks big guy

 

[Poodles]

seemed to actually hurt the power of the engine all across the board...

maybe with more tuning or degreeing it would see larger gains, but you CAN go too big on cams...

 

[flubyux2]

well... sound performance confirmed the testing... ill grab the sheets for you. and the cams WERE shimmed and degreed to eliminate as many variables as possible.

brb

ok, here is the real-world testing. it was actually intended to test the claims that reverse-stagger setups are beneficial. it turns out that reverse stagger setups are lose-lose, no matter how you slice it. but the first run *unlabeled* is the 264/264 run. the other 2 runs *reverse stagger* and then full 272/272 are obviously labeled. This is on Ju-Hon Chan's mkiv.

 

[Poodles]

OUCH

 

[IJ.]

My guess is they're 264 and 272 @ 50 thou NOT 264/272 advertised like the BC cams for the 7M's.....

I run 280 advertised here and they're 226 @ 50 so not all that big.

This confusion in terminology has been a problem with bench racing from the year dot.

 

[tissimo]

go 272s if you rev high.. if not stick to 264s

 

[suprarich]

You guy just need to stop with all the 264 and 272 lingo already. This not how you measure or compare cams as IJ pointed out. That is a measure of a made up advertized duration and has no meaning to how "big" the cams really are.

 

[flubyux2]

justin, the 272 set dropped power just as much as the small cams. revving higher wont uncover a magical, second torque peak at 8000rpm.

and who gives a shit what the numbers mean?

how bout we just call them Small and medium. or cam set A and cam set B. the progressive logic in the past has dictated that if A is good, B must be better, therefore C must be Best and D will probably God-like... but that isnt the case, as proven by the people who have set the bench-mark in off-the-shelf upgrade cams, regardless of useable duration vs. advertised duration.

there is obviously a point of diminishing returns no matter what you want to call those things.

maybe SP will do a test comparing the "272" to the "280".

i already know that advertised duration is merely a selling tactic. i know that anything over 220* @ 0.050" lift is getting into an aggressive range. shit, the cam i have in my trans am is a 308/320 with an LSA of 113*... OMFG! thats Gotta make more power than some HKS 280's right? its actually only a 230*/240* cam... sounds small nothing like the eloquent 272 that we all talk about.

 

[suprarich]

The problem with the test is, the cams are all tested in one motor. That motor may have been best suited for one type of cam and not for a larger set. Thus showing less gain on the bigger set. On a near stock motor, a small cam will show more power gain than larger profile cam. On a highly modded motor moving lots of air, the bigger cam will make more power than the smaller one. The test sp and HKS did is biased. Proven by the graph, as it only shows the test motor making 500 ish hp. The HKS 272 cams should be in a 900+ hp GT motor, not a 500hp. Over cammed. ALL I am saying is, every cam was made to produce power for a certain application. You cannot conduct a flat test for 2 totaly different cam applications.

 

[IJ.]

Chris: My "point" with the advertised Vs @50 "numbers" was you need to choose a cam for the application and a 272@50 is a HUGE set of cams and I'm not surprised it was no better than the 264's (would love to see some EGT #'s on those)

 

[Zazzn]

272 264 280's are all useless numbers nubmers need to be at .50 lift.

 

[logan]

Some numbers

The hks 2j 272 cams are 232 @ 1mm ( which is .0394 ) with 9.3mm lift

BC 7mgte

264 220 @.050 and 8.53mm lift
272 226 @.050 with 8.68 mm lift

Got Hks cam card here
http://www.supraforums.com/forum/showthread.php?t=230466

 

[suprarich]

272 264 280's are all useless numbers nubmers need to be at .050 lift.

Fixed that for you. Pretty big cam to need to measure at a half inch of lift:naughty:

 

[suprarich]

Chris: My "point" with the advertised Vs @50 "numbers" was you need to choose a cam for the application and a 272@50 is a HUGE set of cams and I'm not surprised it was no better than the 264's (would love to see some EGT #'s on those)

Just for grins IJ, the biggest cams I have ever seen are in my drag Harley.

.641 lift, 330 degree duration at zero, 317@.020, 285@.053

They look like a square box more than a lobe.

 

[Sawbladz]

I'm not too knowledgeable about cams so bear with me.

I would like to know if it is possible to determine the entire cam profile from the numbers given @ 0.050. Do all cams for a given motor follow some parabolic formula such that at any given time you can solve for the lift and duration given an initial condition @ 0.050.

Basically I want to know how you will know how a cam behaves based on one single number which represents the behaviour of the cam at only one interval of rotation.

I could draw many very different cam profiles which would all pass through the point of X duration @ 0.050 with Y lift but all of these profiles would look very different and therefore have different properties to go with them.

I'm just curious how this all works.

 

[tissimo]

justin, the 272 set dropped power just as much as the small cams. revving higher wont uncover a magical, second torque peak at 8000rpm.

Then you've over cammed your car. If the car is setup correctly (so it will breath on the top end) it will gain power with 272s over 264s. again... it will have to breath to the 8k range to see good gains with the 272s over 264s from what i've seen in the mkivs

 

[bowsercake]

I would like to know if it is possible to determine the entire cam profile from the numbers given @ 0.050. Do all cams for a given motor follow some parabolic formula such that at any given time you can solve for the lift and duration given an initial condition @ 0.050.

The answer is no. But, the numbers can give you a good idea. However, one cam manufacturer may have developed a more "square" cam profile and another one may have a more "narrow" cam profile. So, the more square cam would spend more time at a higher lift, letting in more air than a narrower cam, even if the lift and duration specifications were the same.

However, knowing the lift and the duration at 50 thou can help you a lot.

 

[IJ.]

Rich: LOL

The Cams Gary runs in his 7M rail are sort of square with rounded corners I'm not sure on the specs but they'd be some of the biggest in a 7M I know of!