4A Tri-flow Camshafts and Stock cam talk

[BigMike]

Hey Bill,

I was doing some research on cams for my GZE and came across this. Have you heard about this? http://www.nonstoptuning.com/pageTriFlowDynos.html

They are taking a dual intake valve camshaft and having one lobe with a lower lift & I believe a staggered duration such that 1) velocities will be higher at both minimum valve angle and also maximum valve angle (so you get better bottom end and top end pwr), and 2) they are inducing a swirl to help with combustion (better MPG, lower emissions, smoother running).

Here is the page from ColtCams, who NST apparently co-developed the cams with: http://www.coltcams.com/html/tri_flow_technology/, and also a price sheet from NST: http://www.nonstoptuning.com/pNSTtriflowCams.html GOOD LORD THEY ARE EXPENSIVE. $800 for a pair of cams, and only the intake has the staggered design.

In other news, I discovered that my GZE does in fact NOT have large port cams. Take a look: http://www.mr2oc.com/showthread.php?t=468414 also posted at reply #71 of my build thread here.

Cam	Lift	Duration	Intake opens	Exhaust opens
4A-GZE cams, AW11/AE92	7.10mm	232°	8° BTDC	47° BBDC
4A-GE cams, AE86 & AW11	7.56mm	240°	9° BTDC	51° BBDC
WebCam grind # 294	8.20mm	244°

So I think I am gonna swap out only my intake cam for a 4A-GE 7.56mm cam. What do ya think? Should I swap in both GE cams?

[Sirdeuce]

The Tri-flow cams are no news here. As for the 7.56 lift cam, I believe you already have them, the lower lift cams are from the small port 4AGE. Verify with a dial indicator.

[yoshimitsuspeed]

The smaller cams were only found in three rib motors. By the time the GZE came out all cams were the same smaller cams, NA, GZE and the SP.

[Sirdeuce]

Sorry Yoshi, but that was a bit confusing. The bigger cams were used on all the T-vis engines, 3 or 7 rib and the smaller cams came in the small port engines. At least in the NA engines. I've not looked into the SC engines cams though.

[yoshimitsuspeed]

I do not believe that to be true but I will admit I have not personally confirmed it. There is also conflicting info out there which doesn't make it easier. For example billzilla does say the smaller cams are SP only however I have seen enough evidence to be pretty confident that around 87-88 they all had the smaller cams.
http://www.hachiroku.net/forums/archive/index.php?t-3709.html

84/85/86 all had the 3-rib blocks with large cams
 87 was a weird year... some 3-rib (mainly early production) and some 7 rib blocks.... i personally bought an 87 with an original 7 rib (not in the car anymore though...)
 88/89 had the 7 rib with the smaller cams, but obviously still bigport head

http://www.mr2oc.com/showthread.php?t=549665

[BigMike]

Wow very interesting. So also less valve overlap with the later model cams. My MR2 is a Jan of '87 but I have no clue what cams were originally in it.