Apparently the S1's are on backorder till June.

What there be a big difference in gains between the Tomei Poncam 260 vs Kelfords/S1's?

The Poncam 260 is appealing because of the minimal lope so if the gains are still good in comparison to the S1's I'll get them.

 

I haven't tuned both sorry so I can't tell you how they compare on the same car. The tomei's at 0,0 idle basically stock, and I mean really. No lope at all, just the occasional hint of roughness (unless you increase overlap with cam gears). Sound pretty mean at +1.5, -2.5 though and boost comes on quicker.

 

So they're worth it?

 

For starters, we can't refer to cams as a "272" or a "280" and draw useful comparisons. The Crane '272' cam set in my engine and HKS 272s are apples and oranges, simply because my cam set gives 230+ degrees @1mm, and the HKS set only 110. Duration at 1mm is what you need to consider, because that is the only real measuring stick when it comes to comparing cams based upon duration figures.

Secondly, you need to consider lobe centerlines (LC) and lobe separation angle (LSA) if you don't have a set of adjustable cam gears. The HKS 272s are very docile because they are timed to give better low end vacuum and good top end performance at the expense of some midrange response, midrange torque, and spool characteristics. Conversely, the GSC S1s are timed to improve the very things the HKS set sacrifices, and has quicker ramp rates that translate into better low speed response. Adjustable gears allows one to manipulate this. Not having them means it's important to get a cam set with timing best suited to what you want.

In your case, wanting a smooth idle means you will sacrifice some response and midrange in the heart of your turbo's 'sweet spot' as compared to what's available, although top end should be fine. The sets that will give the smoothest idle in that class when installed straight up are likely the JUN 264, HKS 272, and possibly Tomei Poncam (264).

 

So the GSC S1 is the probably the best all round cam I can get? Provided I'm willing to have some lope.

If I get cam gears, is there any other cams that I should consider based on the fact that I can adjust the timing now?

Thanks.

 

To put things into perspective, I had HKS 272s for quite some time, with both EVO 6.5 TME and 20G turbos. The HKS 272 comes with LCs of 110/110 and an LSA of 110. To get best response and midrange punch, I had to adjust this to 106/110 and an LSA of 108 with cam gears. The idle was choppy, but strong.

The GSC S1s are ground at 107/113, with an LSA of 110, which is very close to what I found to be the optimum HKS settings, except the GSCs should give a bit better idle. Also, the GSCs have better ramp rates and top end potential, and unlike the HKS cams, are built to respond to head porting. In short, the GSC is a more recently designed cam aimed at more serious users, whereas the HKS offerings are more consumer grade items.

You'll have to accept some idle chop to get appreciably better midrange response and top end performance, but this won't be enough to present any issues here.

 

GSC S1's it is then.

Thanks Ted B and everyone for all the great information in this thread

 

Be sure to report back here once you get them installed and tuned.

 

I will.

 

im curious to what the results are, im running HKS 272's but thinking of changing them

 

I'll post VD results when it's all done.

 

Just installed Tomei Poncam Type-R (270) last weekends, didn't have a chance to do some logging, so not sure about the full potential of these cams, but idle lope is good after initial basic adjustment (1000 rpm idle target / BISS / 12 degree ignition timing / less idle stability timing adjustment range / ISCV tables / cam gears set at -2/-1).

One of my friend with JDM EVO 8 has GSC S1 and his idle is much smoother with only about 7~8 degree / 950 rpm idle target / BISS adjustment / AEM cam gears set at -3/-2.

I did not know that I will be a fan of lopy idle until I experience it in my own car. It is far from being unstable.

Definitely engine responds stronger even at part throttle from about 2500rpm compared to stock cams, but I have never had hands-on experience with cammed car, so no comparison with other cam options.

 

Both of you (your friend in particular) are losing valuable spool time with these cam timing settings.

Just FYI.

 

Yes, my friend specifically requested maximum power squeezed out from his 20G turbo. He is very satisfied with his results.

I decided to go this way after consulting the cam gear angle setting with you at another thread. -1/-1 should be similar as S1 and -3/-2 is for -2/-1 S1. So I went for between and I am happy with my result! Thanks for your valuable input, Ted!

 

Tomei 260's / +1.5,-2.5 / BBK Full