M20 B3x Naturally Aspirated Stroker build past, present and future

[digger]

We don’t have enough words to thank you all your info and all the time you take to learn and to share this...is priceless

i have arrive to your post looking for a setup for my engine.
is a m52b28 2800cc 6700rpm for street use close to stock in fact, stock cams and stock intérnals.

I need to do a new exhaust for it and if i understand well, in your investigation for street use, the s54b32 exhaust offers a good base for it.


So taking in mid that from OEM m50/m52 uses twins 1,75” ID for the secondary pipes and the s50b30 use twin 2,25” I thing is not bad idea to use twin 2” ID For the new one

with that say your 2th harmonic with s54 base setup with kats sounds that best bet for me.

so for the secondary pipe 2 twins 2”(50mm) pipes with 1600-1700 leght (kats include) looks nice in my mind
giving that I don’t know if is better to use and H pipe or a X pipe because in your setup you use the X pipe but in the s54 setup that you recommend they use H pipe.

about the final pipe at first I was thinking to go twin 2” too with the muffler and twin 2,125” tail pipes, ¿is worth use 2.25” for the final pipe in place of the 2”?

I really appreciate your opinion into my setup

s54 as in configuration not sizes (diameters)

i favour around 1600 mm give or take with a street engine. This is in effect a total length of 2200 mm when primary (assume 600 mm) is accounted. If you use longer primary then retain total length 2200 and shorter the collector a bit and vice versa. E.g. with long tube headers which are like 800mm often then 1400mm will work ok to.

twin 2" is plenty unless its a crappy workmanship i.e. bad bends, misalignment, mismatch etc. A really nice twin 1.875" or 1.75" would also work but need to pay a bit more attention to the details include the muffler, cats, resonator sizes and efficiencies

[Mr Mpower]

We don’t have enough words to thank you all your info and all the time you take to learn and to share this...is priceless

i have arrive to your post looking for a setup for my engine.
is a m52b28 2800cc 6700rpm for street use close to stock in fact, stock cams and stock intérnals.

I need to do a new exhaust for it and if i understand well, in your investigation for street use, the s54b32 exhaust offers a good base for it.


So taking in mid that from OEM m50/m52 uses twins 1,75” ID for the secondary pipes and the s50b30 use twin 2,25” I thing is not bad idea to use twin 2” ID For the new one

with that say your 2th harmonic with s54 base setup with kats sounds that best bet for me.

so for the secondary pipe 2 twins 2”(50mm) pipes with 1600-1700 leght (kats include) looks nice in my mind
giving that I don’t know if is better to use and H pipe or a X pipe because in your setup you use the X pipe but in the s54 setup that you recommend they use H pipe.

about the final pipe at first I was thinking to go twin 2” too with the muffler and twin 2,125” tail pipes, ¿is worth use 2.25” for the final pipe in place of the 2”?

I really appreciate your opinion into my setup

[digger]

I'm still waiting to hear back from ATI, they have been very slack in responding. i have a new OE one on the shelf and a low mileage one but its not going to be particularly well suited to mine. i'm sure it would work well in normal driving and occasional short bursts to 7500 but id like to buzz mine to 8000rpm if the power curve is sufficient to warrant

that dyno above is a flywheel number, its not whp as how most in US or Oz would expect. he hasnt build that other engine with those specs yet it was a basic 2.7. it should easily exceed 230whp with the new spec provided it is executed properly of course

[ForcedFirebird]

Hey Digger, crank hubs have been NLA fore a while. The client with the 12:1 m20b25 that exploded his damper two yr ago ('19) went with a modified ATI unit that was drilled for the m20 crank snout, then modified a v-belt pulley to suit. He is still banging 8500rpm and it's held together for the 2020 season. Pretty sure we will see some more power this 2021 season, he peaked at 208whp/198wtq last year, but when he sent his head in for a refresh in Jan, I was able to get another ~12-14cfm on the intake side from ~.200-.350" valve lift. Will post results in the dyno thread once it's together.

Hi, they use a SuperFlow AutoDyn 30 AWD dyno if that clarifies things for you!?

Short vid of the car on the track:

https://youtu.be/YFAlrWJ0lEk

I'm looking to get a new head, 44-45mm intake valves, cam 292 or up, 12.4 or higher CR pistons and ITB's (tapered 45>42mm) for this year and maybe get another 20-30HP out of it... but posting my wants here is off-topic I guess :D

Yes, it does. At first, I thought your HP number was a little high (hence the comment about W vs B HP). But, then realized today reading back that your numbers are metric. That brings us closer to the SAE 215lbft I have seen many times. After conversions you are making 234whp/215wtq SAE, which is right on par for your upgrades. It seems like getting over the 230whp mark is a bottleneck for these single cams without diving deep into the valve train (oversized seats, custom/roller rockers/cam etc).

No one said the stock manifold "can't", it's just not as easy as using ITB. Just putting RHD ITB's on a bone stock m20 picks up almost 20whp.

[digger]

I'm looking to get a new head, 44-45mm intake valves, cam 292 or up, 12.4 or higher CR pistons and ITB's (tapered 45>42mm) for this year and maybe get another 20-30HP out of it... but posting my wants here is off-topic I guess :D

that should make a big difference to power but it is hard to find good head porters though. if you only gain 30hp with those modifications then there is seriously something wrong

[beemaestro]

stock manifold is good for around 220-230 whp +/- which is around 250-260 bhp+/- so yeah 235 SAE hp at flywheel is achievable.

years ago a guy build a 2.7 whith good CR stock manifold and huge dbilas cam 312 degrees or something crazy and it still fell with this ball park.

It does come down to your definition of proper power

It think with fairly basic components like 81mm crank, 272> cam, headers, anything over 210-215hp is bonus

[beemaestro]

You have to compare apples to apples. Is that a real wheel power number, or that weird calculation of brake power calculated from wheel power?

Hi, they use a SuperFlow AutoDyn 30 AWD dyno if that clarifies things for you!?

Short vid of the car on the track:

https://youtu.be/YFAlrWJ0lEk

I'm looking to get a new head, 44-45mm intake valves, cam 292 or up, 12.4 or higher CR pistons and ITB's (tapered 45>42mm) for this year and maybe get another 20-30HP out of it... but posting my wants here is off-topic I guess :D

[digger]

I've been hearing of more of the stock units exploding with age and they have gone NLA as far as I'm aware, nice to see we have some options in the works.

yeah but it might be spendy enough to keep people away though, like other ATI vibration dampers for BMW's....though when i bought a new OE one it was still a few hundred

[zwill23]

I've been hearing of more of the stock units exploding with age and they have gone NLA as far as I'm aware, nice to see we have some options in the works.

[digger]

Very cool, I assume the damper is going to facilitate higher rpms?

Sounds like big things are on the horizon

yes, the stock damper wouldn't be best for the longer stroke engines as its tuned for different frequency(s) plus they will start to be NLA soon if not already. The catch it is a very tight envelope so some light trimming to the lower timing cover is required but that should be about it.

[zwill23]

Been working on a side project for an ATI vibration damper for the M20 that's essentially plug and play, it is fairly well developed from a design point.

Also got some other non engine things to work on with the car with rear axles, diff etc, plus interior dash, carpet etc so will be on hold for a while longer yet.

Also still a bit to do before i swap engine in as want to get a more modern standalone and new carbon airbox (requires the install of the Massive dual MC booster delete which is ready to trial).

Very cool, I assume the damper is going to facilitate higher rpms?

Sounds like big things are on the horizon

[digger]

How's the car digger? Make any progress on the engine build?

Been working on a side project for an ATI vibration damper for the M20 that's essentially plug and play, it is fairly well developed from a design point.

Also got some other non engine things to work on with the car with rear axles, diff etc, plus interior dash, carpet etc so will be on hold for a while longer yet.

Also still a bit to do before i swap engine in as want to get a more modern standalone and new carbon airbox (requires the install of the Massive dual MC booster delete which is ready to trial).

[zwill23]

How's the car digger? Make any progress on the engine build?

[vehicular]

I have an RHD flywheel on the floor of my shop now. I'll try to make time this weekend to model it.

I have some other parts I need to model anyway.

[digger]

Some hopefully interesting Mass/Inertia data

So first eveyone knows what mass is, its linear or translational inertia. Mass moment of inertia (MMOI) is the rotational equivalent. it tells you the resistance to angular accelearation.

the simplistic formula for a point mass is MMOI = Mr^2

so 1kg at 150mm distance is 1 x 0.15 x 0.15 = 0.0225 kg.m^4

Here are some formulas for simple shapes like cyclinders etc



Here some data for flywheels, essentially the mass is meangless its the MMOI that dictates what the resistance to spinning up.

Stock M20B25 228mm Flywheel (FW) and Pressure plate (PP)
Metric Mechanic 240mm lightweight FW (based on M30 with M20 starter gear) and M5 PP

Mass were weighed data and inertia values were from some CAD approximations. The density were tuned in the CAD to match the weighed values as steel and Cast iron density varies. The bits that are steel are steel so the inertia is fairly accurate.

What it shows is what i suspected the pressure plate has as much MMOI as the flywheel and even though the 240mm FW is lightened the net effect is mostly diminished as the M5 PP is fairly hefty. The point wasnt to have the lighest though as relatively comfortable pedal effort with nice modulaton like OE but a bnuch more torque capacity is what i wanted. This is what i have used since 2007.

Also for interest i showed the crank and rod MMOI as a point of reference. The rod MMOI is based on the big end mass at the centre of the crank pin.

Stock M20


MM 240mm


Results


Anyone that has a 3D CAD of the RHD one i can work out the numbers.....