Lobe Separation Effects
Turbo Mini Forums

Too cold to go out into the workshop, so have been playing with cams on the simulator.

Using the 998Ti St2 as the baseline, 12G295, GT1752, tuned length inlet and exhaust runners.

I've already got a custom ground scatter cam cut by Kents for this engine, but now I've got the simulation software, it's fun to see what further improvements can be made.

Apart from the MD274, I've only got measured profiles for the MD286 and the MPi camshaft (thanks to Sheridan and Yo-Han). So I've simulated them as measured and then widened the LSA to see what happens:



I've used 1.5 rockers on the MPi as it was lame otherwise.

Interestingly, the higher LSAs give higher power at the top end.

Edited by Paul S on 11th 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."

looks like 112 is a good compromise for a non scatter, thats what I came up with too.

Yes, the MD274 has 112 degrees LSA and it falls just a bit short of the scatter cam that has 112 degrees LSA on the outers.

It's just simulations but it continuously confirms what's been found by years of experimentation.

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."

Here's a comparison of the MD274 and the MG Metro cam:



The MG data has been derived from the timing figures and a default polynomial lift curve which is a little optimistic for factory cams.

Edited by Paul S on 11th 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."

soooo....

gonna do a graph with the ph2?

Ha ha, just thinking the same thing. Wanna make a prediction for a Ph2 on a 998?

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."

Paul do you have the 266 mapped? I'm intrested as I think the 274 would be a big improvement on my 266. Both vmax and ben who makes my kit recommend 112 lca and a 274/5

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

as these graphs are plotted to your engine, is there any general rules that can be used from them across all 998 builds?

one day boost will be mine!

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."

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."

Ok I'll take a punt!

Edited by Joe C on 11th Feb, 2012.

http://www.jbperf.com/

On a boosted setup, inlet and exhaust manifold would need to be horrific to produce really bad results.

You can get away with really terrible exhaust manifolds on turbo cars and they still work great.
There is little reason not to have a good intake manifold though, as it can certainly do no harm. Although whether a carb setup likes a more turbulent manifold is another matter.

As a sweeping generalisation, it seems that engines with poor heads tend to use tighter LSA's, yet those that can achieve good head flow opt for higher LSA's
Whether the latter is also down to those engines usually being newer and having to meet tighter emissions targets I dont know.

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.
A lot of it goes over my head ! lol, I stick to keep it simple.
My current LS camshaft is on 121 LSA ! super smooth idle and no overlap.

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

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

Well done Joe, even better than I expected:



A bit too much cam, but good top end.

Edited by Paul S on 11th 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."

Re13 would be interesting to see, but can you take into account its 50 thou timing.

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,

incoming email

Paul, have you considered the effects of retarding the inlet and advancing the exhaust timings? 115 inlet and 110 exhaust for example.

Out of intrest have you any simulations on the Phase 3 ?

WWW.TURBO-MINI.COM

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

Edited by Paul S on 11th 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."

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."

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."

Haha...wha have you done Robert! I have visions of keyboards smoking with people typing out there replys.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi