M20 B3x Naturally Aspirated Stroker build past, present and future

[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!

[digger]

ive never tried to see what effect closed throttle has

yeah the wires were cheap after doing research which is ok if you actually pay cheap prices. still very pleased with the new wires and i fully recommend for someone looking for a custom set with wasted spark or individual coils to give them a go

[CorvallisBMW]

That sucks about the wires, definitely sounds like they just made some garbage stuff and overcharged you for it.

Regarding the compression testing you did in an earlier post, does having the throttle open (WOT) really affect the numbers?

[digger]

So I pulled the plugs the other week and 3 of the ignition leads pulled out leaving the connectors on the plug what a waffleswaffleswaffleswaffles.

pic of old rubbish wires



The wires were made by a shop when i went to wasted spark and weren’t cheap. i think they are accel wires based on the markings. Found out the fuckers over charged me big time after doing some googling plus they are shit quality.

The 8mm accel wires were supposed to be 500ohm per foot but all the wires 2ft long ohmed at about 15k i know they do break down but within a year? lol

found some cheapo bosch stuff for the interim to get me back on the road

Anyway did some research and seemed like moroso ultra40, MSD 8.5mm superconductor, magnecor & Firecore50 8.5mm were the best for the pushrod folks who have much more demanding applications than mine.

Moroso: were out the window given they made the junk wire set that VAC sell which didnt work when they arrived and the replacement set caused misfires after a year

MSD: well their MSD 6A did absolutely SFA except make the radio interference screw up the AM band so not wanting to try their stuff.

So it was down to magencor or firecore50

Never found a bad thing said about firecore50's i liked the fact that people had said they have put them on and pulled them off dozens and dozens of times and not had any wires pull out and the wires are only 50ohm resistance. They are well reviewed especially on yellow bullet. family owned business not looking to cut manufacturing costs at expense of quality like many others

Custom set of 6 with choice of connectors and length was $145, the guy even rang me up as i screwed up the form and suggested something better, comes with warranty of 12months

As per site the wires ohmed at 50ohm which must be better than 15000? im using resistor BPR6ES plugs not sure whether non resistor plugs would be an issue. boots are nice and long so easier to grab hold of without burning yourself

installed them not long ago and they seem good, like lost performance has been restored. you arent going to gain heaps of power even though it feel like it does go a bit harder, engine seems quite happy and revs more crisply and cleanly than i seem to recall probably just end up with less losses. maybe placebo but some have dynoed and seen gains over other wire sets. im not interested in that too much but just wanted a good set of wires and so far so good.

if you're after a custom set i can recommend based on my initial assessment. same exact wire is used on street cars all the way to top fuel/nascar/promod etc so cant be a bad wire as those guys cant afford to put up with junk.

They also do some 7mm wire which will fit in the OEM plastic moulding if using a stock dizzy but not sure about the connectors at dizzy end if they stock those. Might be best getting an IE set if you a stock setup.

http://www.firecore50.com/

[digger]

Do you have a degree wheel? Sounds like one would make your refinement of your build MUCH easier. For example, you don't think the Cat Cams unit is actually has the specs they claim... you would be able to verify that with a degree wheel, which would aid your pursuit of building the better engine. I haven't read your whole thread, so apologies if you're already using one.

The GM LS community is demonstrating exactly what you describe with regard to cams.

The conventional idea of a "big" cam, and the associated lope at idle comes from the days when cylinder heads flowed for crap, cams were limited to flat tappet lifters and American MFG's just made their engines bigger to compensate... the 1960's.

Modern heads flow so well relative to displacement that medium duration, fast ramp, high lift cams with moderate lobe separation angles make superior torque curves across the entire RPM range compared to longer duration narrower lobe sep cams with more relaxed ramp rates. This is basically undisputed in the LS community and is so widely accepted that most people recognize that selecting a cam that lopes is... umm... ricey and only done for the sound.

The Ferrari 360 is another good example. It makes peak power at 8500 RPM, but because it has 5 valve heads which flow stupid stupid amounts of air for the displacement, it actually has fairly modest duration compared to what "old school" thinking would expect for an 8500 RPM engine.

this is the old engine ive been using with a catcams since 2008, i did not use a degree wheel when setting up the cam but i did roughly set it up based on the relative lift at TDC of inlet and exhaust on the bench which is a bad way of doing it given it assumes the cam is correct. i subsequently dialed it in on the dyno and gave the engine wants etc stopping at 8 degrees advance as the topend would have started reducing had i went further. i could setup a degree wheel and plot it out but i dont think ill get around to that

ive plotted and seen another couple different catcams plotted out they are are often on a wider centres than what the cam card says and as a consequence ive seen about 5 engines 2.7/2.8 strokers make no torque (i.e less than or equal to stock m20b25) below 3500rpm hence my theory. i would never recommend catcam for a street engine there is too much tradeoff for my liking.

i do have degree wheel for the new engine though

[The Dark Side of Will]

Do you have a degree wheel? Sounds like one would make your refinement of your build MUCH easier. For example, you don't think the Cat Cams unit is actually has the specs they claim... you would be able to verify that with a degree wheel, which would aid your pursuit of building the better engine. I haven't read your whole thread, so apologies if you're already using one.

The GM LS community is demonstrating exactly what you describe with regard to cams.

The conventional idea of a "big" cam, and the associated lope at idle comes from the days when cylinder heads flowed for crap, cams were limited to flat tappet lifters and American MFG's just made their engines bigger to compensate... the 1960's.

Modern heads flow so well relative to displacement that medium duration, fast ramp, high lift cams with moderate lobe separation angles make superior torque curves across the entire RPM range compared to longer duration narrower lobe sep cams with more relaxed ramp rates. This is basically undisputed in the LS community and is so widely accepted that most people recognize that selecting a cam that lopes is... umm... ricey and only done for the sound.

The Ferrari 360 is another good example. It makes peak power at 8500 RPM, but because it has 5 valve heads which flow stupid stupid amounts of air for the displacement, it actually has fairly modest duration compared to what "old school" thinking would expect for an 8500 RPM engine.

[digger]

did a hot compression test recently, plugs out, WOT, 7 cranks

1 180
2 180
3 175
4 175
5 175
6 185

compression is not too bad. last time about 2 or 3 years ago i was around 160-165 but have advanced the cam 6 degrees since then that's why the numbers are higher. with the metric mechanic rally cam about 7 or 8 years ago i was 150-155 psi but that was some crazy ass cam they concocted.

advancing the cam moves the inlet valve closing to be earlier which is better for trapping efficiency or DCR (dynamic compression) less reversion from piston pushing charge back out the open valve when there isnt enough "ramming" occurring due to the amplitude in the inlet tuning pressure waves being so small as they are a function of velocity and at low rpm there isnt much velocity

its often said its good to have 195-200 psi cranking compression for a hot street engine as the engine is crisper at part throttle, makes more torque when the engine is not on cam ie 2000-3000rpm. the DCR and cranking compression doesnt mean much for when the engine is on song as other cam specs, inlet and exhaust tuning etc come into it alot more

the recent 180 numbers suggest that i'm using too much duration (i advanced the cam 8 degrees to bandaid it which helped but if i went any further with existing cam i start losing topend at expense of midrange because when you adnce the cam all other valve events move as well (stupid sohc) ) and in turn would probably need to tighten the lobe separation to retain same amount of overlap if duration was reduced. id say 10 degrees less duration would suit my current engine a lot better and 4-6 degrees tighter lsa (from whatever it is as i don't think it is 110 as per catcams claims) to compensate.

new engine with better piston design and setup for proper squish will be using the RHD 292 roller cam on 108 LSA which probably has smaller advertised inlet duration than my 298/285 catcams camshaft (not plotted out my catcam 298/285 but i predict it will) but will have a massively bigger lobe area due to the much higher velocity possible with roller follower.
The lobes will be closer together giving more overlap so it will idle a bit more angry but not any worse than the schrick 288 especially with a big stroke, it has alot more lobe area than the 288 schrick but will have similar street manners because of a seat duration that isn't excessive.

in comparison to schrick it has very similar duration at 1 mm, 12 degrees more at 5 mm lift ,21 degrees more duration at 8 mm and 34 degrees more at 10 mm and the 292 has 50 degrees duration at 12 mm where the schrick stops at 11.5 mm gross....other lift points are nett values

most people over cam their m20 to make up for less than ideal induction system. this is the wrong approach especially for a street engine especially given most have really low compression ratio. once you have a suitable compression, ported head and good flowing correctly sized induction you can use less duration than you think and not suffer the consequences.

[digger]

I've always needed the icv for cold starts. If I run my rhd setup in open loop idle mode (no feedback) it idles stable enough when hot ( but intially you need to spend some time sorting the idle stop after driving so enough heat gets into everything, another important is to have enough pressure on the closed stop so it goes back to same position each and every time. I added extra spring for this). Anytime I've had a problem is because the I screwed something up like the return spring/ coupling for throttles 1-4 need to be working otherwise the throttle are not positively held and can float, so don't bend them lol.
Really the icv in my case is basically for warmup and air con. I zero'd my Tps once I've got the idle speed sorted.