Has anyone ever run a GTS intake cam advanced one tooth?
01-23-2008, 01:25 PM
#61
Rennlist Member
What the holbert car has, is the 86 cams. compared to another GT with the exact same mods, it made the same hp and the curves were identical.(my hp was slightly broader up top near 6000rpm possibly due to the air box mod.
The GT has the better computer, and the Holbert car is bone stock S4 computers. Both were 320rwhp.
if you look at S4 curves with stock S4 cams, they are almost the shape, just lower in power all the way around. There are no advantages in the S4 cams in any of the rpm ranges. based on the cam specs , i dont see the dynamic compression ratio lowering, but I may be missing something.
Mk
The GT has the better computer, and the Holbert car is bone stock S4 computers. Both were 320rwhp.
if you look at S4 curves with stock S4 cams, they are almost the shape, just lower in power all the way around. There are no advantages in the S4 cams in any of the rpm ranges. based on the cam specs , i dont see the dynamic compression ratio lowering, but I may be missing something.
Mk
We're looking at doing something similar on my engine w/ the S3 (85/86) cams. Looking at the numbers, the dynamic compression ratio drops when running S3 cams on a stock S4 head/piston combo. How does the midrange feel? When do you think you'll have dyno graphs? Were there any other mods besides the cams? I'll be extremely curious to see how it turns out.
__________________
Dennis
Engine was a 90 gt , we ported the heads , fitted larger 968 intake valves (928 part no,) ported the throttle body , extruder hone the manifold , machine the pistons to allow the valves to fit , has 944 conrods (early 87 32 v) 180 degree crosover exhaust , fully balanced .
On driving the engine has more torque , more mid range & more urge up top I, intend to increase the rpm cutout to 7200 . It is crnaky to drive around the city as you can feel the cams , the fuel economy is better slightly than before until you use the power , it is very difficult to drive the legally , as the urge to use the power is always there . will be very interested to see what the output will be after I sharktune it .
__________________
Dennis
Engine was a 90 gt , we ported the heads , fitted larger 968 intake valves (928 part no,) ported the throttle body , extruder hone the manifold , machine the pistons to allow the valves to fit , has 944 conrods (early 87 32 v) 180 degree crosover exhaust , fully balanced .
On driving the engine has more torque , more mid range & more urge up top I, intend to increase the rpm cutout to 7200 . It is crnaky to drive around the city as you can feel the cams , the fuel economy is better slightly than before until you use the power , it is very difficult to drive the legally , as the urge to use the power is always there . will be very interested to see what the output will be after I sharktune it .
01-23-2008, 02:30 PM
#62
Inventor
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IIRC, the GT cam is ground 8° advanced, so the 86 cam may breathe a little better up top?
01-23-2008, 04:11 PM
#63
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01-23-2008, 04:19 PM
#64
Inventor
Rennlist Member
Rennlist Member
The different lift measurements per the WSM correspond to the grind of the cam lobes for different years.
My tool shows the same initial angle of the cams, in degrees, for 86, and GT (and S4, GTS). IE. measured from the center of the cam key with a cold engine.
You should take up Bill's offer to see how your cams are really set up.
My tool shows the same initial angle of the cams, in degrees, for 86, and GT (and S4, GTS). IE. measured from the center of the cam key with a cold engine.
You should take up Bill's offer to see how your cams are really set up.
01-23-2008, 09:16 PM
#65
Addict
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Thread Starter
Engine was a 90 gt , we ported the heads , fitted larger 968 intake valves (928 part no,) ported the throttle body , extruder hone the manifold , machine the pistons to allow the valves to fit , has 944 conrods (early 87 32 v) 180 degree crosover exhaust , fully balanced .
On driving the engine has more torque , more mid range & more urge up top I, intend to increase the rpm cutout to 7200 . It is crnaky to drive around the city as you can feel the cams , the fuel economy is better slightly than before until you use the power , it is very difficult to drive the legally , as the urge to use the power is always there . will be very interested to see what the output will be after I sharktune it .
On driving the engine has more torque , more mid range & more urge up top I, intend to increase the rpm cutout to 7200 . It is crnaky to drive around the city as you can feel the cams , the fuel economy is better slightly than before until you use the power , it is very difficult to drive the legally , as the urge to use the power is always there . will be very interested to see what the output will be after I sharktune it .
What the holbert car has, is the 86 cams. compared to another GT with the exact same mods, it made the same hp and the curves were identical.(my hp was slightly broader up top near 6000rpm possibly due to the air box mod.
The GT has the better computer, and the Holbert car is bone stock S4 computers. Both were 320rwhp.
if you look at S4 curves with stock S4 cams, they are almost the shape, just lower in power all the way around. There are no advantages in the S4 cams in any of the rpm ranges. based on the cam specs , i dont see the dynamic compression ratio lowering, but I may be missing something.
Mk
The GT has the better computer, and the Holbert car is bone stock S4 computers. Both were 320rwhp.
if you look at S4 curves with stock S4 cams, they are almost the shape, just lower in power all the way around. There are no advantages in the S4 cams in any of the rpm ranges. based on the cam specs , i dont see the dynamic compression ratio lowering, but I may be missing something.
Mk
Do you have the dyno graphs posted online still? 
01-23-2008, 10:46 PM
#66
Rennlist Member
Dennis here are the finished spec from the grinder
the intake cam std vs new = 255vs265@.006 248vs260@.008 233vs239@.020 214vs217.7@.050 153vs156@.200 104vs111@.300 .393"vs.414" gross lift the exh cams= 236vs246@.006 232vs241@.008 218vs226@.020 200vs208@.050 .352vs.369 lobe lift
the intake cam std vs new = 255vs265@.006 248vs260@.008 233vs239@.020 214vs217.7@.050 153vs156@.200 104vs111@.300 .393"vs.414" gross lift the exh cams= 236vs246@.006 232vs241@.008 218vs226@.020 200vs208@.050 .352vs.369 lobe lift
01-23-2008, 11:16 PM
#67
Rennlist Member
All my runs are on the list, but here are the latest runs. the lower one is the last dyno run, where I suspect that the car was clamped down too tight! Ill never know until i do a dyno again, but this time, i am definitely going to test the theory by using a coast down dyno run at the end of the 3 pulls. then, crank the straps down and try a run and a coast down to see if 15-20hp can lurk in the strap down. kind of a variable that is not thought of , but i bet is still a factor.
anyway, here are those last two dynos
mk
anyway, here are those last two dynos
mk
01-23-2008, 11:28 PM
#68
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Louie, Thanks for your suggestions. I'll dyno the GTS as is and then degree the stock cams as you suggest and give it another run on the dyno and see what the numbers say. I will be interested to see the torque figures as i have never felt the car was particularly grunty below 4k rpm.
I should have a set of GT cams in the next few weeks and I think I'll use those as a starting point for this season and then look at some of the other, more exotic options as the year progresses.
Thanks, Charles 93GTS
I should have a set of GT cams in the next few weeks and I think I'll use those as a starting point for this season and then look at some of the other, more exotic options as the year progresses.
Thanks, Charles 93GTS
01-24-2008, 03:44 AM
#69
Charles I hope to dyno my car next week at Alfamotive, it will be during the week as I have commitments on the next two weekends. If you want to run against another 928 that is, maybe others from the Landshark list can join in too?
Greg
Greg
