Lobe Separation Effects
Turbo Mini Forums

Haha Robert! That Pumaracing sure likes the word Bazinga a lot though!
All this cam stuff is over my head, but from something i read earlier, the 5 port is better suited to a scatter cam. Are all those graphs somewhat relevant to a 5 port large bore carbed engine Paul?

Edited by Carlzilla on 11th Feb, 2012.

Only 5-ports need scatter. They are designed around the siamese port. If you have one port per cylinder there is no point in having a scatter cam.

Interesting graphs.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

The graphs are interesting but I don't think that they tell us anything that we did not know already.

Those of us who have spent far too much of their spare time on TM over the last 5 years know that the most proven 5-port turbo cams are the MG and the Ph2. I've had good results with the MD274, but it is not widely used yet. The Ph2 gives good power at the top end on a 998, but off-boost torque was down by around 30% - didn't we know that?

Stock cams and any high duration cams do not deliver the goods.

Didn't we know that already?

So, for me, the results tell us more about the accuracy of the simulation process for making comparisons. OK, the dyno will need to confirm the actual numbers, but the relative numbers stack up.

The other thing that I've been doing is looking at scatter cams with varying degrees of scatter. Some with whopping scatter and LSA variations. The results have been disappointing and further investigation has led to an interesting conclusion. I need to generate some graphs to explain it. Stay tuned.

Edited by Paul S on 12th Feb, 2012.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yep, it stack up with a lot of my assumtions, although I was suprised to see the ph2 better the scatter one at the top end,

I'd say high duration cams do not deliver the goods in the way we normally use them, I'd say that with proper exhaust and inlet design and a wide LCA a long scatter cam could come into its own on the 5 port, but thats just a hunch, I havend Simed it, and if I had it wouldnt have been as in depth as what you have access too.

Edited by Paul S on 12th Feb, 2012.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

tried siming anything 300 deg or over yet? assuming a BIG turbo ie low TIP somthing like a GT30.

might be a pig off boost though, lol

getting a bit ot there though...

No, but I've put a GT28 on the Miglia engine and 25psi :) Frightening.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Anyway, scatter pattern cams.

The software allows parametric modelling, so you can select a number of variables, tell it a range of values and it will run all possible combinations. You can them compare the results and select the "best". Normally best for me is the largest area under the power curve, rather than a headline figure.

So, I set it running with up to 104 to 116 degrees LCA on inners and outer cylinder inlets, left it overnight, took the best results and ran it against a similar range of exhaust values.

The "best" result, after all that, was only a nats cock better than the starting point.

Now, my theory is that by separating the inlet events to prevent charge robbing, you actually destroy the momentum in the port at the point of inlet valve overlap. So what you gain in VE on the inner cylinder, you loose on the outers, nett result - zero gain.

You do see a gain with just 2 degrees of scatter but above that the gains flatten out. That probably explains why Viz SP cams just have 2 degrees of scatter.

So I'm parking scatter for now.

Edited by Paul S on 12th Feb, 2012.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Interesting,

its been said that scatter patern cams only come onto their own from 290 upwards (by paul W?) but thats on NA stuff, the different pressures from a turbo set up may well change that totally.

Yes, if you consider the maximum lift during the overlaps on the MD274:

1mm on the inlet/exhaust overlap
2mm on the inner inlet/outer inlet overlap.

The corresponding figures for a standard 286 with 1.5 rockers are 2.5mm and 5mm, so charge robbing will be much more of an issue.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The thing to also consider for this particular 998 Turbo configuration is that it is already running over 100% VE at peak, so it is possibly unrealistic to expect large gains from any further mods.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

thats equal to an rs200 btw

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Paul interesting you wanted to try the 266 with some 1.5's I was thinking the same with mine as its an easy install if you do it the pikey way. Anything make you think it's worth the time and money on a set of 1.5's there is a club rr day at the place I use WI I could see it against last years figures?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Any guess's

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

You'll lose boost through the overlap and make less power ????

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

pisser.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

good read !

Interested regarding the supercharging
I am doing a 1172 sidevalve with Eaton 45
The std cam for this engine has 300deg exhaust duration !
was going to just have the inlet reground for more lift and less BTDC overlap [ std 35deg]

?

You want some overlap to allow a bit of scavenging of the combustion chmber, but with a supercharged setup, too much overlap would be bad for performance.

If you limit overlap so that the valves are open less then 2mm at the cross-over point (exhaust closing, inlet opening, both at same lift), then I would expect it to be OK. That's just a hunch though as I have not tried it myself.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by carl talbot on 15th Feb, 2012.

if I didnt think that the valves would hit the bock I would give the 1.5's a go. I'm thinking that the extra 20% lift will casue the oversized exhaust valves to touch.

looking at some google figures for the 266 I think the overlap would increase to about 1.7mm, which might be worth the risk for the extra lift.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

I can only go on experience in my car, i had a 266 with GT17, drivability by far one of the nicest combinations, no lag, but as explained here, topped out very quickly top end, which is why i wish i had gone for a phase2, i could only ever get over 200 banana's with a little boost from the intake weld blowing nos

If i were to build another, i would definately look at cam options and a modern day turbo, like a gt20/25/28

"Cars are a lifetime of pain"

oh dear oh dear ,oh dear ! no sense of umour !

On 16th Feb, 2012 carl talbot said:

On 11th Feb, 2012 robert said:

On 11th Feb, 2012 stevieturbo said:

There's a lot of talk on camshafts over on PH at the minute, although it's more to do with intake centre line than LSA.


http://www.pistonheads.com/gassing/topic.a...entreline+Angle

just stuck my nonsense in there too...:)

You might have upset someone ?! seems like they don't like your pictures and your Woooosh

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM