Engine Build Opinions

[Bugermass]

My goal is to build a motor for high RPM and high boost levels staying on pump gas. I need a shorter stroke motor to keep the piston speed high, that way theres less time at TDC (increases knock threshold) . Also I want to use a flattop piston 84-85MM bore with as close as possible piston to head clearance to maximise squish (increases knock threshold even more). Also I want a higher static compression for more responce and power with less boost, so I'll want to have minimum combustion chamber volume, IE gsr head possibly milled a bit. With this lower chamber volume and flat top pistons I should also theoretically have a much faster burn rate (also increases knock threshhold). I want a rediculous rod ratio so I can rev to say 12K reliably. I'm thinking of running a B16 crank 77.4mm stroke in a GSR block with a GSR head. The stock B16 deck is 203.25mm and the stock GSR deck is 212.39mm The stock B16 rod is 134.366mm so I figured with the 77.4mm crank I need 212.39-203.25 = 9.14mm so my rod will have to be 134.366+9.14=143.506mm long. That'll give me a R/S of about 1.85. OOoor eagle has off the shelf rods 151.5618mm or 148.8948mm that'll give me a R/S of 1.95 or 1.92 : ))) I can just have weisco move the pin in the piston . . mabey,. . not sure if thats to far to move it or not I'll have to call and ask.. With some serious valvetrain, rollerrockers and some nice high lift low duration cams it should make some really nice power between 8-11,500 RPM. I want to break the typical HP figures on pump gas by increasing the knock threshold as much as possible with geometry and combusting optimizations, and I want to keep the boost levels sane with higher static CRs and higher RPMs. Any ideas, comments, flames, or corrections? By the way I wanna do this for the heck of it to see what happens. And it'll all be tuned with eCtune of course.

[calvin]

one crazy authorized tuner

[Gaskleppie]

Always nice to see someone doing something else! If you want max revs, use long rods to minimize cylinder side wall pressure. Maybe even use a deckplate to maximize rod length. I realy don't know what rods you need but there must be something which will fit. Like the idea!

[Joey Misanthropy]

My goal is to build a motor for high RPM and high boost levels staying on pump gas. I need a shorter stroke motor to keep the piston speed high, that way theres less time at TDC (increases knock threshold) .

Longer stroke with shorter rod is how you keep piston speeds high and cut down on dwell at TDC.

Also I want to use a flattop piston 84-85MM bore with as close as possible piston to head clearance to maximise squish (increases knock threshold even more).

Go 85mm. For peak power on pump gas you need peak displacement. With 85mm you can still get good headgasket seal with a big power setup.

Also I want a higher static compression for more responce and power with less boost, so I'll want to have minimum combustion chamber volume, IE gsr head possibly milled a bit. With this lower chamber volume and flat top pistons I should also theoretically have a much faster burn rate (also increases knock threshhold).

Eh, no thank you. Higher CR is just going to lower your knock limit due to there being a smaller available combustion chamber at TDC. You will reach "critical mass" of intake charge and not be able to control detonation where a lower CR engine's bigger chamber's limit would still be a far ways off.

I want a rediculous rod ratio so I can rev to say 12K reliably.

I've taken 84X89 to 10K reliably, plain jane ungirdled B18A block with Darton flanged (open deck) sleeves and Eagles/Wisecos. I can post pictures of the bearings after 6K miles, they look really good. All your problems will occur in the head at or slightly over 10K rpms. You will need over 100 lb/in valvesprings, and your exhaust cams - aftermarket pieces as mere ITRs will suck - will be changed more often than your oil.

I'm thinking of running a B16 crank 77.4mm stroke

Displacement > Larry Widmer's stupid ideas on rod/stroke ratio that have never worked in the real world. You've contradicted yourself by saying you want to minimise dwell and max piston speed and knock limit, then proposed a high RS low displacement method. Piston speed is piston speed... for iso-octane fuels the burn rate is going to stay proportional to piston speed, but developing actual detonation is a function of time. More later, I am late for class.

[Joey Misanthropy]

Meh, I'm not sure I've stated all my points as eloquently as I should have. Sideload on a small bore engine with lightweight internal is inconsequential, guys, that's what heavy internal bigger bore engines have problems with. Commonly achievable RS is not a problem with Honduh engines. If I were on a budget (I am) I would go 85X89mm (I am) and floss what I could out of the engine on conservative revs - 9-9.5K with 85lb/in valvesprings. If I had cubic dollars I'd probably go 85X92mm and spin to 10-10.5K with 100lb/in valvesprings. The only person I know of spinning a big turbo build to 12K with any reliability was the RLZ car, 84mm B16, and it was making right at 500 on racegas... I never could get an answer on their cam wear or spring selection... probably custom stuff since Brad Z was part of a $2 million contract to R&D valvesprings for NASCAR 6-7 years back. But, that's another subject. Go either GT-series, or one of the Borg-Warner extended tip technology turbos, or Holset - I prefer journal bearings for price and longevity reasons.

[nate]

Thanks for your in-depth insight!

[Gaskleppie]

Low end will suck but it saves your valve train.

[Bugermass]

Your right about the dwell time, I got that backwards.. but as for 85X89 ??? you honestly think that will hold up for long durations @ high HP and 9K ??? How have you been keeping the bearings in the motor on this setup?

[Bugermass]

So do you think a setup like a 85X89 but in a B16 deck height with shorter rods be reliable? thats gotta be a really crappy R/S . . . hmmm I can't decide. . I've had alot of luck with this N/A B16 I built and it holding up well to revs at 10K.. Thats why I\"m kinda leaning twords the 1.95 R/S for even better reliability and high RPMs.. You think its goin to far for what its worth?

[Joey Misanthropy]

The engine in question I was revving 9700-10K was an 84mm LS bottom end with B16 head, T67, RC1100cc, 16-17 psi on pump gas. Blundar rode in, drove, and did a partial tune on the car at one point and might have some insight. All the problems we had were in the head and were primarily with the exhaust cam VTEC lobes stripping out - one B16, one GSR, and a Rocket M21 regrind were munched over the lifespan of the engine before the (stock) intake valves gave up. If you want a high rpm toy to show off a short stroke is the way to go, but if you want as high as possible knock limit on pump gas then you want big displacement first and whatever revs you can afford (cost of valvetrain, longevity of build, etc). Figure out what direction you want to go and call up Brian Crower over cam/valvetrain advice is what I'd do. The set in the BRMS car held torque flat as a strap until 8K+, I have to say I was impressed. Gaskleppie, I have zero experience with aluminum rocker arms, can you offer any insight? I've \"heard\" they require the engine to idle higher, etc.

[Bugermass]

I've spun B20 VTECs to 9500 in our shop race cars when I worked at this one shop, but the motors never lasted very long, always had problems with rod bearings giving out. The motor you were spinning to 10K how long did it run? I've had great luck with GSRs and B16s holding high RPMs with no problems but anything with a 89mm stroke seems to have a pretty short lifespan..

[Civic Tsi]

They call this a valve train stabilizer, or in other word a girdle. I'm waiting on tangible results.

[blown99civicsi]

Pure Sex!! My personal setup would love to rev to 10K as power at 9K is still climbing, but I dont want to push it. Something like this would give me the faith to run her that high, as 30PSI and 9K is kinda scarry as it is. I do know that for the amount of boosted setups I have tuned, and the percentage of them being limited by there knock threshold, I have found that 90% of the short stroke mild compression setups have vary little issues with limitations when it comes to there threshhold being a issue. Thus the reason I went with a B16 sleeved to 84MM, 9:3:1 compression, B18C5 head, are just the basic parts I run. Im a firm believer in running Meth/Alch injection on any street car planning on running 400+WHP on the street. It was a pivitol point in building my setup to acheive 600+WHP on pump gas. I have yet to reach my knock threshold, and I have thrown some pretty high timing numbers at her for shits and giggles..