M20 B3x Naturally Aspirated Stroker build past, present and future

[digger]

Engine went on dyno to check blowby using a meter i bought.



measured upto 1.5cfm maximum, i think that isnt too bad

[digger]

So how what was the hp difference between the standard manifold vs the pulse tune?


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idk, too many things happened at same time (cam, rebuilt head etc) to determine the gain from pulse tune manifold alone (its all about midrange though). ITB are about same price and work alot better anyway

[DER E30]

Bump, just read the whole thing! Your knowledge is incredible! Can't wait to see where this goes!

One of these days I'm gonna do itbs on my m42 I think.

[JeLani]

So how what was the hp difference between the standard manifold vs the pulse tune?


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[digger]

on paper i would choose the 280 because it has equal intake and exhaust duration. if you have good exhaust port flow compared to intake port flow it makes more sense to have backsplit cam duration, its very common on S14 and S54 which have high exh/int flow ratio.

also with slightly more lift at TDC but slighty later opening suggest quicker ramps (in 29* it reaches 2.3mm vs 32* reaching 2.2mm) maybe more area under curve (slightly) they may be defined abit different though so not always apples vs apples.

284/272 is a good street cam though

[bmwmaster81]

Alternatively i could use asymetric 284°/272° Schrick with these Specs:

Schrick:
284°/272° 111/100 72/32/26/66 lift: 11.40/11,0 2.2/1,7mm @ tdc

Schleicher (for comparison again):
280° 111 71/29/29/71 lift: 11.40 / 2.3mm @ tdc

Which would you prefer?
It's not a daily driver. But i also don't like to rev the hell out of it, just sporty driving sometimes.

Could you maybe explain something about the asymetric point? does it make sense to use this kind of cams? advantages? disadvantages?

Thx

[digger]

280/280 looks good for that compression, id set it up 2-4 degrees advanced though with a vernier cam gear. check piston to valve clearance as this will probably be a limiting factor

personally i wouldn't run a 288 duration on the street without a better intake manifold and ported head and perhaps a slightly higher static compression 11:1 is about ideal. many people have but you just wont get near the capability of the cam without those things but you'll still get the downsides.

[bmwmaster81]

Hi digger,

i read the whole thread and must say that your work is really amazing !!!
I also have built an m20 stroker but am using 272° Schrick cam.

Specs are M52 crank with high compression pistons.
Decked block so CR is 10,5:1

While cranking i have about 210 psi and think with another cam i could optimize my engine little bit.
Here in germany we have an company called schleicher. They offer cams for m20s and i find them quite interesting, but lack of my knowledge i can't realy judge if they will have good caracteristics in my engine. Maybe you could give me some advise ?

They offer 4 different cams with these specs:

270° 112 67/23/23/67 lift: 11.10 / 1.4mm @ tdc
274° 112 69/25/25/69 lift: 11.10 / 1.7mm @ tdc
280° 111 71/29/29/71 lift: 11.40 / 2.3mm @ tdc
288° 110 74/34/34/74 lift: 11.70 / 2.9mm @ tdc


Im thinking about to buy the 280° Schleicher cam to replace my 272° Schrick....what do you think ?

P.S.: Im running standalone ecu without MAF and car is just used on public roads.

[digger]

sorted out why the tacho wouldn't work after wasted spark conversion.

the shop just screwed up the pins when they reassembled the connector. they routed the boost control output to the tacho. i sorted this out after an hr or so crawling around under the dash checking wiring diagrams. this is the second issue i sorted due to something being pinned incorrect and i know SFA about electrons and their pipes.

[digger]

yeah makes sense, main reason i put mine at WOT so flood clear is activated and no fuel is injected

[ForcedFirebird]

with ITB i imagine it may take a few more pulses though if throttle is at idle vs WOT

Same with a single. Just one or two strokes more.

[digger]

presumably with single throttle at manifold entry there is enough volume in the system that it is negligible difference like FF said.
with ITB i imagine it may take a few more pulses though if throttle is at idle vs WOT since the blade is cracked less with ITB as its only feeding 1 cyl ata time instead of 2.5 at a time like the single TB

[ForcedFirebird]

I do compression tests almost daily, and I have never seen any difference with throttle open/closed.

[digger]

pics of what?

[Mfever]

digger can you post some pics in this thread, we need some eye candy man!