cams cams and more cams

[mad_mat1987]

Hi guys and girls.

my name is Mat. i have a mazda 323 astina 1997 ba hardtop. very similar to project.r.racing's 323 hatch except mine is a hardtop/sadan. now i have a series 3 BP motor in my car, which after some research it is the same motor as an NA8 mx5. has no HLA's in the head and a very similar rocket cover.. now my question is, what cams are avalable for these engines.. im doing a turbo converion and i'm looking for a set of cams that will give me as little overlap as possible. in my motor the cams are as follows:

Intake cam duration
233° @ 0.003"
Intake cam opening
3° BTDC
Intake cam closing
50° ABDC
Intake cam lobe height
45.0mm (1.772")
Intake cam base circle
36.0mm (1.418")
Intake valve lift
8.9916mm (0.354")
Exhaust cam duration
241° @ 0.003"
Exhaust cam opening
51° BBDC
Exhaust cam closing
10° ATDC
Exhaust cam lobe height
44.9mm (1.768")
Exhaust cam base circle
36.0mm (1.418")
Exhaust valve lift
8.890mm (0.350")
Valve overlap
13°


and from what i could find the NA8 cams are as follows:

Dur @ intake exhaust
Adv. Dur. (.003")
.010" 257 278
.020" 224 232
.040" 209 215
.050" 204 210
.080" 190 196
.100" 181 187
.150" 158 164
.200" 132 141
.250" 102 114
.300" 59 79
Valve Timing 8° BTDCC 53° BBDC
49° ABDC 9° ATDC
Overlap. 17°
Base circle Diam. 1.418" 1.418"
36 mm 36 mm
Total Lift .326" .350"
8.28 mm 8.89 mm



so basically all im asking is what are my options.

If anyone has any questions please ask me and i'll help you as much as i can.

Mat

[NitroDann]

You do not want as little overlap as possible, Id suggest doing a lot more research before searching or just handing some cash to a cam expert and telling them the rest of the setup and the result you want.

PM 'wozzah1975' on here, also known as warren heath performance, he is THE man for BP mods in aus.

Dann

[mad_mat1987]

You do not want as little overlap as possible, Id suggest doing a lot more research before searching or just handing some cash to a cam expert and telling them the rest of the setup and the result you want.

why dont i want as little overlap as possble?? i thought that the less overlap means less wasted boost or boost leak in otherwords..

PM 'wozzah1975' on here, also known as warren heath performance, he is THE man for BP mods in aus.

i will do that now

[NitroDann]

why dont i want as little overlap as possble?? i thought that the less overlap means less wasted boost or boost leak in otherwords..

This statement is why you need more research.

You have been speaking with honda or subaru drivers havn't you

Ill find the post I made regarding this. It was a long winded thread.

Dann

[NitroDann]

You dont take away overlap to gain power.

110% NO.

Its done to offset the effects an improved volumetric efficiency has on torque curve.

Overlap works when the engine is spinning so fast that the engine cannot possible breath properly, both removing 99% of the exhaust as well as inhaling fuel/air without it.

With no overlap the engine cant breath fully at any RPM above a few dozen RPM. Fact.
Understand this first.

With a lot of overlap the engine wastes air and fuel at low RPM. Fact.
This is because at low rpm the engine CAN breathe fully, there is enough time for the vacuum to equalize pressure inside the cylinder and out, and the overlap results in wasted fuel and lowered dynamic compression.

The more overlap you have the more RPM it takes for the overlap to perfectly time full cylinder filling. Fact.
Because at lower rpm the valves are open too long, this is what you argue about when boosted.

The higher your Volumetric Efficiency (VE) the faster cylinder filling happens. Fact.
This is what Volumetric Efficiency means.

The higher the RPM, the less time there is for cylinder filling to occur, duration and overlap allows for more time per cycle. Fact.
No explanation needed.

So heres the go.

You have an n/a car and some overlap.
The overlap is inefficient at low RPM, open at the same time, and theres enough time for intake to go straight out the exhaust.
At higher RPM, there is less time, the overlap gives the cylinder time to fill, as the extractors pull a vacuum on the exhaust valve.
When you increase VE (with boost, portwork, better exhaust) the cylinder filling is easier, and faster.
Faster filling means it happens in less time.
This suits higher RPM, which of course has less time for each cycle than lower RPM.
So now with increased VE your torque curve moves up the RPM scale.

Are you following now?
The overlap increases rpm at which torque occurs, this in turn INCREASES PEAK HP.

You decrease overlap simply to reduce RPM that the overlap is now timed for with the higher VE and faster cylinder filling.

IT ONLY KEEPS THE TORQUE CURVE THE SAME.

Dann

[NitroDann]

If you still do not follow,

VE means volumetric efficiency, which basically means how well the engine breaths, its measured in a percentage and 100% means that a 2L engine ingests exactly 2L of fresh air every cycle. This doesnt happen because the cycle happens so fast that exhaust cannot make it out fast enough and intake air cannot make it in fast enough.

Long story short, a turbo car or a supercharged car will naturally make more power up the rpm band further, and you can counter this by reducing overlap, however all that does is gives the car a similar shaped (although taller due to boost) torque curve to what you had without the forced induction.

If you run overlap and then boost the motor will just need to rev a fair bit. Just like a honda, it will rev, and it will be much faster than with the smaller overlap cams.

Dann

[mad_mat1987]

why dont i want as little overlap as possble?? i thought that the less overlap means less wasted boost or boost leak in otherwords..

This statement is why you need more research.

You have been speaking with honda or subaru drivers havn't you

Ill find the post I made regarding this. It was a long winded thread.

Dann

BAHAHAHAHAHAHAHAHAHAHAHA

maybe i have been lol

thanks for the info. i will have to do some more research. im just looking at making more touque down low.. most of the cars i see with BPT's are making +200FWKWs but with not much touque.. my car is for track and hill climbs.

thanks again Dann

[NitroDann]

Did I meet you yesterday?

Dann

[mad_mat1987]

Did I meet you yesterday?

Dann

hmmm dont think so.. i live in brisbane qld i was a jamboree tho..

[NitroDann]

There was a guy with a BP astina at Buladehlah hillcimb yesterday, most sideways car of the day and the only FWD haha.

Dann

[mad_mat1987]

There was a guy with a BP astina at Buladehlah hillcimb yesterday, most sideways car of the day and the only FWD haha.

Dann

haha really.. na my suspension isnt quite that well tuned.. my corners quite well with minimal a33 chassing front.. but the rear sway bar has kept it all in play.

anyway off topic.

so ur saying that if i want to increase touque (which i would like to do) i should decrease my overlap. but to to 0%. i understand that if u increase ur overlap the max HP moves heigh up the rpm range. but im only looking at using the 7k red line and max.. ive PM'd wozzah1975 so i'll havea chat to him about what he thinks i would be the right setup.. remember im going to be running a rebuilt, full forged pisston and rod block.. the head and cams is where im worried..

[NitroDann]

I dont think you understand the question you are asking.

Increasing overlap doesnt decrease torque, it moves the torque further up the rev range, increasing power.

What you are saying is that you want as much torque as you can get at low rpm.

The answer is compression, cams with big lift, and E85.

Dann

[stb]

Or find a BP with VVT and put that in... variable overlap is very effective at flattening/fattening the torque curve.

[project.r.racing]

Matt, if you wann decrease overlap, then keep the cams you got, 13d overlap and the biggest lift from stock cams for all BP engines ever built.

but as Dan said, you are adjusting to peak torque to a certain rpm range, which will effect peak power.

as for your question as to what will fit. anything will fit. you have the same base circle as a NB8C MX5. but get some new solid bucket and shims, and anything is possible. hence why i brought new solids for mine. that way i can chase even more lift again at a later date.

[wozzah1975]

Hi guys and girls.

my name is Mat. i have a mazda 323 astina 1997 ba hardtop. very similar to project.r.racing's 323 hatch except mine is a hardtop/sadan. now i have a series 3 BP motor in my car, which after some research it is the same motor as an NA8 mx5. has no HLA's in the head and a very similar rocket cover.. now my question is, what cams are avalable for these engines.. im doing a turbo converion and i'm looking for a set of cams that will give me as little overlap as possible. in my motor the cams are as follows:

Intake cam duration
233° @ 0.003"
Intake cam opening
3° BTDC
Intake cam closing
50° ABDC
Intake cam lobe height
45.0mm (1.772")
Intake cam base circle
36.0mm (1.418")
Intake valve lift
8.9916mm (0.354")
Exhaust cam duration
241° @ 0.003"
Exhaust cam opening
51° BBDC
Exhaust cam closing
10° ATDC
Exhaust cam lobe height
44.9mm (1.768")
Exhaust cam base circle
36.0mm (1.418")
Exhaust valve lift
8.890mm (0.350")
Valve overlap
13°


and from what i could find the NA8 cams are as follows:

Dur @ intake exhaust
Adv. Dur. (.003")
.010" 257 278
.020" 224 232
.040" 209 215
.050" 204 210
.080" 190 196
.100" 181 187
.150" 158 164
.200" 132 141
.250" 102 114
.300" 59 79
Valve Timing 8° BTDCC 53° BBDC
49° ABDC 9° ATDC
Overlap. 17°
Base circle Diam. 1.418" 1.418"
36 mm 36 mm
Total Lift .326" .350"
8.28 mm 8.89 mm



so basically all im asking is what are my options.

If anyone has any questions please ask me and i'll help you as much as i can.

Mat

Hi Mat,

I can regrind you cams if you require bigger.

Specs are
226@ .050"
270deg advertised duration
.363" lift
I can do them in either mechanical or HLA profiles (the mech are slightly bigger).

There will be a small sacrifice in low end power (below 2500-3000rpm) but everything above that is an increase in torque and power. If you carry out cylinder head work at the same time you can bring back the low end power, and also further increase the mid/high power and torque at the same time, so you have the best of both worlds.

I have a car running around on cams similar to those listed above with a good std valve cylinder head package. It is fitted with a TD05-20g turbo with an 8cm exhaust housing on a custom manifold. Good power starts at 2500, and further again at around 3400rpm, peak power at 6500rpm. First tune it made 220rwkw on 14psi, and its going back tonight for another tune to lean on it a bit harder, as the first tune was very conservative. I will post the dyno results on here when I have them so you get an idea of the curve, but I can tell you it's very fat considering the turbo size. The reason you see vehicles with big peaky power numbers and no low end torque is usually because they cram massive amounts of boost in std cylinder heads to get the power. Applying big cams to these cylinder heads makes the power narrower again.

The key to having a broad power curve is to key the right pieces together. An engine with a well thought out cylinder head and cam package with the right hang ons will make more power, much broader power and torque, and less boost to do so.

Picking cams for a turbo engine is the same as picking cams for an NA engine, you need to work out what rpm points you want your power and work around that. Cams for turbo engine generally come back 1-2 profiles to put the power at the same RPM point as an NA engine (so slightly smaller grinds), and the dial in points are different on a turbo application, usually you run 2-4 deg wider phase angle between the 2 cams.

Cheers
Warren