What Cam Duration?

phatR · Postby **phatR** » Thu Oct 18, 2007 2:14 am

Im working my way up to turboing my 99 NB and will put in cams when I end up installing the turbo

anyway I know Tomei and Toda make good quality cams for the MX5 and lift is more important than duration

But when lifts of Tomei and Toda are the same what duration combination gives more power?

Highest intake and exhaust duration
Same duration for both intake and exhaust
Higher duration for exhaust than intake

Tomei Cams
Lift = 10mm
Duration Intake = 252
Duration Exhaust = 256

Toda Cams
Lift = 10mm
Duration Intake = 264, 272, 288, 304
Duration Exhaust = 264, 272, 288, 304

Has anyone put these on their beauties?

Babalouie · Postby **Babalouie** » Thu Oct 18, 2007 2:25 am

I got the Tomeis. Can't speak for the Todas, but given the powerband on the Tomeis I wouldn't (personally) go any wilder. They are perfect IMHO.

Went from here (before cams):

To here (after cams):

ben wilson · Postby **ben wilson** » Thu Oct 18, 2007 6:02 pm

Tighe 805C at around those specs (254, 9mm of lift), might be a bit cheaper.

Not sure how well a stock head flows at higher lift.

845C have 10mm of lift with the same duration, that extra mm of lift will be harder on the valve train.

sharaleo · Postby **sharaleo** » Wed Oct 24, 2007 2:07 pm

Keep in mind that the cam specs for N/A and turbo applications vary drastically.

Typically with N/A more performance is gained from larger lift and longer durations, maximising the amount of air drawn into the cylinders.

However, long durations often result in overlap between inlet and exhaust valves opening/closing. This would be undesirable in a turbo application due to the positive manifold pressure delivered by the turbo. If the inlet and exhaust openings overlap, the 'boost' will bleed out of the cylinder into the exhaust.

Best advice is to ask for advice from the cam manufacturer.

I have never done a turbo conversions myself, but in most I have read about, there is very rarely cam modifications. The money may very well be better spent elsewhere, ie ECU, Tuning, etc. Maybe those that have done conversions may offer their thoughts...?

Cheers!

AB7 · Postby **AB7** » Wed Oct 24, 2007 3:17 pm

Sorry a bit off topic.

Hei Babs,
Im actually considering putting in Maruha/ tomei Sport VVT cam set (for 2001 NB8B),

Did you get the solid lifter kit as well...or did you add undershim?
How much does it cost to install the cam?

Postby **Okibi** » Wed Oct 24, 2007 3:52 pm

Your cam choice is also limited by the ECU, since you're going to turbo, sounds like a good excuse to put in an ECU as well. :mrgreen:

Perhaps we should get together and begin an NB8A turbo group buy.

ben wilson · Postby **ben wilson** » Wed Oct 24, 2007 9:05 pm

sharaleo wrote:Keep in mind that the cam specs for N/A and turbo applications vary drastically.

Typically with N/A more performance is gained from larger lift and longer durations, maximising the amount of air drawn into the cylinders.

However, long durations often result in overlap between inlet and exhaust valves opening/closing. This would be undesirable in a turbo application due to the positive manifold pressure delivered by the turbo. If the inlet and exhaust openings overlap, the 'boost' will bleed out of the cylinder into the exhaust.

Best advice is to ask for advice from the cam manufacturer.

I have never done a turbo conversions myself, but in most I have read about, there is very rarely cam modifications. The money may very well be better spent elsewhere, ie ECU, Tuning, etc. Maybe those that have done conversions may offer their thoughts...?

Cheers!

Tighe recommend the 805C for both turbo and NA applications, different timing for turbo.

http://www.tighecams.com.au/cars.htm

Fatty · Postby **Fatty** » Wed Oct 24, 2007 9:29 pm

sharaleo wrote:Best advice is to ask for advice from the cam manufacturer.

good advice :mrgreen:

further to that, i'd investigate whether you even need to spend money on cams if you are going turbo. do the se and sp have different cams to the standard nb ? ? i don't know, hence the question. would the cost of the cams be better spent on ecu (as others have mentioned), or other areas ?

how much power are you hoping to get out of your turbo set up? before spending any money, find out what engine / drivetrain mods are needed to reach you power goal. you may find that no mods are needed at all, other than to bolt a turbo kit on. for example, i set my goal at 150rwkw, not just cos of the engine limitations but because it is around the safe limit of the diff and gearbox. i can reach this goal with no internal engine mods at all.

Postby **Okibi** » Wed Oct 24, 2007 9:59 pm

I don't know any turbo NBs in WA with non OEM cams

Babalouie · Postby **Babalouie** » Thu Oct 25, 2007 5:13 am

AB7 wrote:Sorry a bit off topic.

Hei Babs,
Im actually considering putting in Maruha/ tomei Sport VVT cam set (for 2001 NB8B),

Did you get the solid lifter kit as well...or did you add undershim?
How much does it cost to install the cam?

I've got an NA, so it's easy for me. Just bung in the cams and the hydraulic lifters adjust to the new cams. So no need for the lifter kit but you NB guys don't get it quite so easy with the cams.

zoomzoom · Postby **zoomzoom** » Thu Oct 25, 2007 1:24 pm

I was told by crow that for turbo it is better to have more duration rather than lift, but variable cam gears may be neccesary to dial out some of the overlap.

phatR · Postby **phatR** » Thu Oct 25, 2007 10:33 pm

well... i have already bought wiseco forged pistons for my internals

i am also intending to get a stand alone ecu when i turbo my car

so i guess cams is still something to look at...

also considering my engine will have to be taken out when i do my internals it would be a good time to put cams in as well

if anyone wants (i know there is already a group buy master but..) i am willing to organise a group buy for cams

for those who don't believe me when i say it will make a difference, heres a link to something that will make you ponder

http://forum.miata.net/vb/showthread.php?t=243805