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Discussion Starter #1
hi i'm about to get the Hks 272 Camshafts but it seems to me theres 1 for the exhaust and 1 for the intake So which do i buy do i buy Both???
 
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Discussion Starter #3
Get both, not just one, maybe you can get 272 exhaust and 264 intake, but go with 2 272's.
 

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Depends on how much power you are putting out. Don't get 272's if you are making less than 800rwhp. those cams are way to big while 264's will be fine. Plus 264's will idle smoother than the 272's.
 

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Ill say go with 272's, the idle is OVERRATED ! is nice and makes a nice broom broom broom noise ...kinda cool ;)
 
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Jesus said:
Ill say go with 272's, the idle is OVERRATED ! is nice and makes a nice broom broom broom noise ...kinda cool ;)
yup yup, just like the 3037s is overrated. :D

Sweet TJ BJ
go 272's ~!!!!!!!!!!!!!
 

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ok so is it ok to go with the 264 cams or 272 right now i'm building up my supra i'm prolly goin' single t-67 or t-72 so which one would be advisable cuz there seems to be speculation between 264 cams and the 272
 
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Discussion Starter #13
Does anyone on this site have enough knowledge about cams to get into the technical issues of why our motor would perform better with more duration, lift, etc.?

It seems logical that more airflow requires more duration and lift, but as the guy in the Hks post said, this has NOT been proven to be the case in domestic engines. In fact, more often than not, you tend to see turbocharged domestics running a more modest duration profile. Why?

Anyone here with some knowledge in this arena? Right now I would venture to say most Supra owners are doing one of 2 things when buying cams:

1. Assuming (possibly incorrectly) that they need more duration/lift for a bigger turbo.
2. Flat-out guessing.

Neither is really the way you should select a cam/cams.
 

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Yes, it's a HKS HyperTi exhaust.

JoeD said:


nice little video you got there, XCELR8. :)

what kinda exhaust system is that?? looks like HKS Ti....but im not positive.

TIA
 
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Discussion Starter #15
Does anyone on this site have enough knowledge about cams to get into the technical issues of why our motor would perform better with more duration, lift, etc.?

It seems logical that more airflow requires more duration and lift, but as the guy in the Hks post said, this has NOT been proven to be the case in domestic engines. In fact, more often than not, you tend to see turbocharged domestics running a more modest duration profile. Why?

Anyone here with some knowledge in this arena? Right now I would venture to say most Supra owners are doing one of 2 things when buying cams:

1. Assuming (possibly incorrectly) that they need more duration/lift for a bigger turbo.
2. Flat-out guessing.

Neither is really the way you should select a cam/cams.
In general, the valve is the single most restrictive and controlling point in the air pump known as the internal combustion engine. Small changes at this point result in massive changes in engine characteristics. However, a turbo in the system modifies that. Here is the order of restriction on the Supra engine:

1) turbo manifold/turbos @ ~450 rwhp
2) camshafts @ ~600 rwhp
3) head/intake manifold @ ~800 rwhp

I am not saying more power cannot be had above these levels with those stock components, just that's the bottleneck at that point.

After you relieve the huge backpressure restriction of the stock turbo/manifold, the valve becomes the point of bottleneck. At some point, more boost will just spike the torque peak and very little more hp will be gained. Torque will fall off at a greater and greater angle to redline. Boost is just a measure of the engine's inability to injest air, so you can move more air at the same boost level by increasing how much can get through the valve. This is done by changing the profile of the camshafts - allowing more air into the combustion chamber. You have to have more air to make more power.

As you alluded to, a turbocharged vehicle is a balancing act that involves variables not present in an NA vehicle. The hot side of the turbo is still a restriction, so there is pressure there when the exhaust valve opens. If the pressure there is higher than the intake charge pressure, and there is overlap, the obvious happens: not all the exhaust charge exits the combustion chamber and not enough intake charge gets in. So less oxygen is available for combustion, and less than optimal power is made. This is the reason most camshafts for turbo applications have modest duration. Often, this is made up for by higher than normal lift in respect to the duration. For example, I believe the 264 cams have a 8.5mm lift, while the 272s have a 9.2mm. 272 is not much more duration than 264 in comparison to the lift delta. This same pattern is seen often in domestic turbocharged applications as well. Take a stock engine mustang with an aftermarket turbo added - that stock cam is overlarge for a turbo application because it was designed for an NA motor. The stock TT Supra cams would be small for an NA motor because they were designed for a turbo car. Make sense?

A 272 cam may seem huge in comparison to the stock cam, but is still modest when compared to a cam designed for a hi-po NA motor.

So, the reason why some go with bigger cams is:

1) turbo sizing and cam sizing are directly proportional in making power,
2) it's been proven beneficial by others that tried it out before
 
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Discussion Starter #16
Excellent post Darren.

I'm getting the feeling that given our application (turbocharged), in theory we want to choose cams with less overlap, more lift, and the most moderate duration profile we can get away with given that they can flow the desired given output up top. Smaller duration will provide more low end as long as that chosen duration can adequately flow enough air for on the high end. Make sense or no?

So my 2 direct questons to you would the be at what point would it be beneficial to select 272 cams over 264 cams? Is it merely a tradeoff of top-end power vs. low-end power(shifting the power band), or will 272 cams perform better accross the RPM range when we reach (x) power level?

Also, what are you thoughts on 264/272 split duration cams? What is the technical theory behind this and in what scenario, if any, would it be benficial? What are the possible advantages/disadvantages of this in real world MKIV applications?
 
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Discussion Starter #18
So my 2 direct questons to you would the be at what point would it be beneficial to select 272 cams over 264 cams? Is it merely a tradeoff of top-end power vs. low-end power(shifting the power band), or will 272 cams perform better accross the RPM range when we reach (x) power level?

Also, what are you thoughts on 264/272 split duration cams? What is the technical theory behind this and in what scenario, if any, would it be benficial? What are the possible advantages/disadvantages of this in real world MKIV applications?
I personally believe that around 800 rwhp 272s will start to pay off. Keep in mind that I do not have ANY empirical data to support this - only anecdotes. I have noticed that 700-800 rwhp cars equiped with 264 cams make the same power and curves to 272 cars, though the 272s seem to have a slight bit more lag. In addition, noticing the tendency of very large Japanese 3037 turbo-equiped cars running 272 cams seems to support the notion that 272 cams are just BIG TURBO cams.

Along the same lines, I understand why some are starting to run 264s for intake and 272 for exhaust, but it's not proven. I believe that these cams are matched as a pair, and a little cocktail party engineering is probably not going to outdo the engineering effort put together by the tuners. Once again, very powerful Japanese cars use the 272 cams as a set with good success, so in absence of testing to the contrary, I think that's the way to go.
 

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Darren,

Lance W. on the list suggest that one 264 exhaust cam paired with a stock intake cam could be a good option (with the exhaust cam set to center, or maybe advanced a few degrees with a cam gear). He says the intake side of the head flows so much better than the exhaust, that the extra overlap of 2 264s might not be ideal, especially for people wanting to minimize lag and maximize $/hp. Do you have any thoughts on this setup?

I suppose I could try it, and add another 264 if I don't like the results.

The stock exhaust cam is only 236 duration and has 1mm less lift than the 264.
 

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Or maybe someone can go with a 256/264... everyone forgets about the lil old 256 cams.

Grant said:
Darren,

Lance W. on the list suggest that one 264 exhaust cam paired with a stock intake cam could be a good option (with the exhaust cam set to center, or maybe advanced a few degrees with a cam gear). He says the intake side of the head flows so much better than the exhaust, that the extra overlap of 2 264s might not be ideal, especially for people wanting to minimize lag and maximize $/hp. Do you have any thoughts on this setup?

I suppose I could try it, and add another 264 if I don't like the results.

The stock exhaust cam is only 236 duration and has 1mm less lift than the 264.
 
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