M20 B3x Naturally Aspirated Stroker build past, present and future

[SNEAK413]

Just looking at optimal head design

[ForcedFirebird]

That is part of the angled squish band to match the dome on the pistons.

[digger]

What did they do to the 885 on this part marked by the smiley face? I can't tell if they completely removed it or just polished it.

What did who do ? looks standard to me

the head i got ported still has this, it has been sanded and the sharp edge blended over, some of the the pics don't show it well but some you can still see it

[SkiFree]

Thanks for putting up those vacumm log pictures .... do you think 6mm was plenty big enough?

[digger]

6mm is fine, I would think I can get a idle speed close to 2000rpm or more not that you'd need to

[SNEAK413]

What did who do ? looks standard to me

the head i got ported still has this, it has been sanded and the sharp edge blended over, some of the the pics don't show it well but some you can still see it

Yes that is a stock head with a smiley face. I was curious as to what knight engines did on that part. Thanks Digger

[whodwho]

I designed this vacuum rail to mainly use Closed Loop Idle Control which is important for cold start (mine never starts properly without it, now it starts better than OEM) and fast warmup, the intention was to make things neat and tidy compared to the monstrosity i have been using. Its 20 x 20 x 1.5 mm hollow aluminium tube with a cap at each end. has tapped bosses with M6 threaded 6mm nipple for each runner and another for the FPR which has a t-piece for using a vacuum gauge or running to the ECU internal map sensor (currently T-piece is capped off as im using ALPHA-N).

How are you metering the air from the ICV, just extra fuel with warmup enrichment and built into the VE table for an average position when warmed up?

I think you are running a vac pump now but were you running a check valve on your brake booster vacuum hose?

[digger]

How are you metering the air from the ICV, just extra fuel with warmup enrichment and built into the VE table for an average position when warmed up?

I think you are running a vac pump now but were you running a check valve on your brake booster vacuum hose?

Strictly speaking I don’t meter air at all given I use Alpha-N. I think you are implying that when you open the ICV the engine still reads zero load (0 tps) with a Alpha-N Map even though the airflow has increased due to the icv being open at idle.

When the engine is cold I just add a preset amount of fuel based on engine coolant temp that gives a nice AFR at idle and light load conditions based upon the wideband. This means that when the engine is cold it still ads the correction % regardless of the rpm or load so while not being perfect it works fine within reason.

If I was to set it to idle at 1500+rpm with normal idle still at 950rpm when cold then I’d need to adjust the coolant temp correction a lot at low temp to get it to idle correctly due to much more extra air being added but still being at load site of zero being registered. If you drive at moderate load say 50% then you nolonger need so much correction % as the ICV airflow becomse less significant so the mixture is off and you’ll run rich. Obviously there is no real reason to bump the idle up so much, nor high load on cold engine…..i use upto 1200rpm when its really cold (less than 15C), down to 1100 at about 20C and lower it down to 950 at 70C and above.

i also use a fuel trim that adds a % of fuel based on the ICV absolute position.

Vacuum system has the original check valve. I put a Tee in the hose between the check valve and booster that way the pump is “isolated” from the engine. There is another check valve just before the pump as I don’t think it has an internal one.

[whodwho]

I tried adding an ICV today, I thought I might get away with it as I am running in ITB mode(MS2E) and even with the small amount of ICV needed to add slight amount of air (TB stops set for warm idle) it bumped the load way up. I may try again and see about adjusting it out but not that critical in my climate but I like a start and leave it and not have to baby it.

I found the boost assist ok with a small cam engine but would be a bit concerned on any less efficient vacuum source. I may try a vacuum reservoir and see if will give me a touch more available vacuum if needed.

[digger]

I tried adding an ICV today, I thought I might get away with it as I am running in ITB mode(MS2E) and even with the small amount of ICV needed to add slight amount of air (TB stops set for warm idle) it bumped the load way up. I may try again and see about adjusting it out but not that critical in my climate but I like a start and leave it and not have to baby it.

I found the boost assist ok with a small cam engine but would be a bit concerned on any less efficient vacuum source. I may try a vacuum reservoir and see if will give me a touch more available vacuum if needed.

im not familiar with MS, isnt load the tps value with "ITB" mode? how does the measured load increase in this case? with a MAP setup the ICV opening changes the map reading so it changes with load and compensates better.

to complete my vacuum system i had a reservoir made. hope to install this weekend

edit: oh its a blended mode

[whodwho]

It is a blended mode with a twist, it combines the two tables into one with part for AN and part for SD so that you can use a VE analyzer easier.

So that maybe the issue with trying to run the ICV, I may just switch back to AN as the ITB mode is really not that needed for my driving conditions.

I figured a larger diameter short section of PVC pipe and caps would work for the reservoir

[digger]

I don't like pvc unless it's away from heat. Seems to get soft then gets brittle over time. I used alloy tube

[ForcedFirebird]

I tried adding an ICV today, I thought I might get away with it as I am running in ITB mode(MS2E) and even with the small amount of ICV needed to add slight amount of air (TB stops set for warm idle) it bumped the load way up. I may try again and see about adjusting it out but not that critical in my climate but I like a start and leave it and not have to baby it.

I found the boost assist ok with a small cam engine but would be a bit concerned on any less efficient vacuum source. I may try a vacuum reservoir and see if will give me a touch more available vacuum if needed.

On the green car, (Extrudabody ITB's) I am running AN mode and IAC. I set the throttle stops to have the plates completely closed, then calibrated the TPS there. It starts, idles and drives great like this with very little adjustment ever needed (just as a stock m20 would). I also did this in my green e36 with the Jenvey ITB's (413 red label management). Again, cold starts are good, not any adjustments needed really - ever.

On the white car with the RHD ITB's I nix'd the IAC in favor of warm up crack of the throttle plates. I constantly am adjusting the throttle stop and re-setting the TPS calibration. It starts with no problem (no cold here in FL), and idles well, but the constant finicking with the throttle stop is pain.

[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.

[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.