ForcedFirebird's m20 dyno thread.

[darvo]

He needs the 84mm and has the 89.6 (which is putting his pistons way out of the deck - hence the .100" gasket plan).

The pistons are 12:1 for 89.6 and 135mm rods, but the m54 block disappeared after Hurricane María.

I only got a E block laying so, I was looking for 139mm rods to use with a 81mm to match the deck height but only found 138mm to use with the pistons.

The 0.100 gasket is to lower the compression to 11.2-11.5, I would like that CR with my current cam.

[digger]

He needs the 84mm and has the 89.6 (which is putting his pistons way out of the deck - hence the .100" gasket plan).

His pistons are originally intended for 89.6 so he should get that but he'll need to get the 135 rods to go with it.

[SLEEPYDUB]

Ah my bad

[ForcedFirebird]

I have an 89.6mm S52 crank for sale if you're interested. Can ship to your island if you pay for it. Crank was recently polished within spec, balanced, and even comes with the snout spacer you'll need for the M20. Message me if you're interested in it

He needs the 84mm and has the 89.6 (which is putting his pistons way out of the deck - hence the .100" gasket plan).

[SLEEPYDUB]

Thanks Guys! I'll keep an eye on a 84mm, aint 89.6mm bad for rod/stroke ratio?

I have an 89.6mm S52 crank for sale if you're interested. Can ship to your island if you pay for it. Crank was recently polished within spec, balanced, and even comes with the snout spacer you'll need for the M20. Message me if you're interested in it

[darvo]

Thanks Guys! I'll keep an eye on a 84mm, aint 89.6mm bad for rod/stroke ratio?

[ForcedFirebird]

Yup, the 84 would be perfect my main problem is availability where I live. Live on a little island

Get one sent to your little island. It will be worth it though getting the original crank you had planned is probably better as the bottom end and midrange torque will be a lot better

I agree with Digger. Should be able to get one shipped from the states to PR.

[ForcedFirebird]

my guess is the differences are mostly breathing mods

looks like that cam isn't doing shit

Swapped the diff out, it was smoked. I couldn't even turn the output flanges by hand once it was on the ground. If it was that stuck static, I could only imagine how much it was dragging at top speeds. I wondered why the graph kinda went flat from 5-6000rpm, then dipped, were m20's usually have a smooth curve that peaks at 6k.



Again, not sure that car will go back to the dyno anytime soon, but will see what I can do.

[digger]

Get one sent to your little island. It will be worth it though getting the original crank you had planned is probably better as the bottom end and midrange torque will be a lot better

[darvo]

Yup, the 84 would be perfect my main problem is availability where I live. Live on a little island

[digger]

Why not use 84mm stroke as that works almost spot on or get another 89.6 crank they aren't expensive in the grand scheme of the overall build process

[darvo]

Honestly I have not done much with the adjustable gears on the dyno.


Here's the graphs from Sat.



81mm crank, 130mm rods, b25 pistons, .080" (2.03mm) off the deck, stock cam (and cam gear), in house rebuilt head, .035 quench, bored throttle body, extrude manifold, eBay headers, single 2.5" exhaust through 2 mufflers. MS1 with a smooth elbow pipe, cone filter.


[ATTACH]125591[/ATTACH]


81mm crank, 130mm rods, b25 pistons, .080" (2.03mm) off the deck, IE 272 cam (stock cam gear), in house rebuilt head, .050" quench, stock intake/TB, stock exhaust manifolds, single 2.5" exhaust with a single resonator. Stock ECU re-mapped at the dyno.


I believe this car "should" have made more power, was actually a little disappointed. Later after watching a video sent by a friend, I can hear a lot of diff noise that was impossible for me to hear in the car while tuning (one car bay with a dyno in it). Doubt we will bring it back to the dyno, just rebuild the diff and send it racing.



[ATTACH]125592[/ATTACH]

Nice Dyno #'s! I recently purchased a set of 12:1 85mm Vac 885 head pistons for a 89.6 and 135mm stroker build but the m54 block I had in mind was thrown away before I got to it.

So I found a set of 138mm rods that I'll use with a 81mm eta crank to build my 2.7i. I'mm just have to deck the block 1mm and put a thicker 0.100" gasket to lower compression to 11.5:1.

I'll be using my stock 885 head and 284/272 schrick which made my stock b25 anemic down low.

Looking forward to end results.

[darvo]

Oh yea thats right.

I was thinking about my SuperETA block...

Im really curious what mine will make with the package I am expecting in a week ;)

What will your setup be?

[2mAn]

The added stroke is what bumps the compression - swept volume. The 2mm off the deck is because the crank is 6mm more (3mm up, 3mm down strokes), but the rods are 5mm shorter than b25. Taking the 2mm puts the pistons back up close to the head. If you didn't shave them, you would have an extremely large quench/squish (distance between the head and pistons at TDC).

Oh yea thats right.

I was thinking about my SuperETA block...

Im really curious what mine will make with the package I am expecting in a week ;)

[ForcedFirebird]

Would it matter as much on an FI engine?

That's a whole 'nother conversation. When you pressurize a system, you are no longer relying on the atmosphere to "allow" the air charge to enter an engine, you are "forcing" it in.



I actually prefer to make an engine as strong as I can BEFORE adding above atmo. The old saying "lower the compression, add more boost" is moot in modern days - when generally, if you have a strong engine and add boost, the strong engine will always out perform a low compression over all - just keep in mind when you have a lot of added static compression and add boost, your tuning window gets extremely small - low compression/high boost engines are very forgiving on timing and fuel delivery, and fuel type becomes critical on high comp.

I am not afraid to boost 10:1 engines. The low compression gig is a fallacy IMO.


I like to say N/A all the way! Anyone can throw a big turbo on a car, not many people can pull big numbers from an N/A engine.