[Supras] Now for a real question

[Hacker J]

this writeup can be found at  http://www.supracentral.com/content.php?article.106 



Camshaft Specification
				

				by Arlene Lanman on Thursday 08 April 2004
				


				
				

7MGTE Stock Turbo Cams: Intake: 200 duration @ 0.050" and lift of 

0.295"; Exhaust: 201 duration @ 0.050" and lift of 0.297; what I 

don't know rated duration or lobe separation angle or amount each 

is advanced or retarded. According the MkIV.com 

(http://mkiv.com/specifications/ncf/ncf93/ncf077.jpg), Intake opens 

at 6 BTDC and Closes 50 ABDC (for a Total Duration of 236); 

Exhaust opens at 53 BBDC and closes 3 ATDC, for a Total 

Duration of 236).



NA Cams: According the MkIV.com 

(http://www.mkiv.com/specifications/ncf/ncf93/ncf033.jpg), Intake 

opens at 6 BTDC and Close 40 ABDC (for a Total Duration of 226); 

Exhaust opens at 53 BBDC and closes 3 ATDC (for a Total 

Duration of 236). Intake Lift = 7.683mm (0.3025"); Exhaust Lift is 

same as Turbo cam: 0.297" (7.5438").  Dan Gyoba (3-Jun-02) 

wrote: Stock NA exhaust cam is the same as the stock turbo exhaust 

cam. The intake cams are different, but I don't know the parameters, 

entirely, but I know that there is a difference in lift of 0.19mm (With 

the NA intake being less than that of the turbo.)  (Source:  1990 

TSRM page EM-48).



Here is a little bit more I have found out, over time, concerning the 

HKS cams that were, at one time, available:  Intake: 218 duration @ 

0.050"/256 rated duration and 0.3208" lift; Exhaust: 218 duration  

@ 0.050"/256 rated duration and 0.3188" lift.  Intake (0.050" point) 

is set 3 deg after TDC; Exhaust (0.050" point) is 9 deg before TDC. 

Thus, valve overlap is very, very minimal.



7M-GTE TurboA cams: 272 (Total Duration), 0.350" (8.9mm) lift.  

Special valve springs (TurboA valve springs) were required to resist 

valve float at high rpm.

 

----- Original Message ----

Hi list:

    Bought a pair of N/A cams on ebay.  All of the lobes are uniformly about .009" to .010" less in height than the turbo cams.  Also, there is only a minimal groove where the front seal lip wears on the front diameter.  So these cams apparently have not seen much use, and apparently are N/A cams.

    I set up each in the lathe with a flat follower attached to a 1" travel dial indicator, and a degree wheel at the tailstock end, held between the front end screw hole and a live center in the tailstock.  A pointer was made out of wire.  I tested both the intake and exhaust cam and could not find any timing differences between the turbo and N/A cams, except for maximum lift, a little less with the N/A cams.  

    In the data below, the exhaust comparison is shown.  The intake comparison is just about the same.  In neither case did I find a 10 degree difference in duration.  I set the degree wheel to read zero at .050 lift on the closing side.  Because the degree wheel was hard to set precisely the estimated error is plus or minus .003" to .005" in lift.  However, a 10 degree difference in duration would have shown up.  I can list the intake data as well, but it is just about the same is exhaust data in each case.  Bear in mind that angles shown are camshaft, not crankshaft degrees.  

Exhaust: open to close, .from top to bottom in table, 050" lift set to 0 degrees closing.

Turbo Lift        Turbo angle    N/A lift    N/A angle

.000                -130               .000        -130
.008                -120               .010        -130
.017                -110                .013        -110
.048                -100                .056        -100
.120                -90                  .122        -90
.193                -80                  .197        -80
.250               -70                  .250        -70
.284                -60                  .279       -60
.296                -50                  .288        -50
.285                -40                  .278        -40
.249                -30                  .247        -30
.192                -20                  .190        -20
.120                -10                  .119       -10
.050                   0                  .050         0
.016                +10                 .015        +10
.009                +20                 .012        +20
.001                +30                 .003        +30

Any information from anyone who has researched this subject would be appreciated.  

Thanks.

        BernieK