Stealth97

iTrader: (5)

RPM Limit: 8000
Built engine: yes
Engine Specs: H-beam rods, lightened crank/fly, big valves
Track the car: a little drag
Avg number of times your car sees redline/day: it saw 7k all the time, only 8 on dyno/track. no power up there

going to see if I make more power up top with some DIY porting and SUB conversion, if I can get my head back from the machine shop

midpack

iTrader: (3)

RPM Limit: 7200
Built engine: no
Engine Specs:
Track the car: yes
Avg number of times your car sees redline/day: 2-3 times per lap, depending on track. Often when driven on the street, which isn't much.
~1k miles/year

dasting

RPM Limit: 7,250
Built engine: No
Engine Specs: Stock VVT long block, unopened, ~86k miles, full bolt ons, ecu
Track the car: Almost exclusively, about 10 days per year. TTD/HPDE4
Avg number of times your car sees redline/day: A couple hundred per track day? Depends on track and conditions. Street use is mostly only to and from track. Power really starts dropping off around 7300, and I like to baby the stock head because I don't have time to fix much stuff these days.

18psi

iTrader: (76)

Maybe I'm uber conservative, because I was actually about to post the opposite seeing all these stock-rod and stock head BP's being revved past 7.

Is it not true that nasty things happen like stretching rods and pounding valve seats when you're consistently over the oem rev limit? Aside from the 2 obvious things like floating valves and most of us not making any power up there..

I don't think I've ever revved any of my engines past 7. Stock, built, bp4w, bp6d, all of them.

sixshooter

iTrader: (12)

...And stock oil pumps fail, and possibly throttle body shafts.

There is a dramatic increase in wear at 8000 rpm versus 7000 rpm. Emilio mentioned in another thread about the BP crankshaft being relatively fine at ~7500 and like a limp noodle at ~8500. This would mean that somewhere between those two values very strange things begin to happen. Paraphrasing what I recall, iirc, that the lifespan of the engine goes from being measured in hours to being measured in minutes when spending a lot of time at 7000 vs. 8000. Since I am not a "racer" I have no desire to rebuild my engine every year, I'll keep the lower limits and try to optimize my performance below them. If I was trying to win the HPDE Championship, I might be willing to push things more.

18psi

iTrader: (76)

Yes yes and yes. That was my understanding as well

patsmx5

iTrader: (16)

I reved a stock rod 99 engine with stock, but lightened valves to 7,800 for about a year (ran 100 shot nitrous and MS2E), then bumped it to 8,000 and did that for over a year, 11 months of it were turbocharged. So probably about 2 years total on a stock bottom end. Bearings looked perfect. Rods were bent, but that was from nitrous accident at the drag strip. FWIW, I used the same oil pump that came on my '99 until 2013, it's seen 30 PSI boost, 100 shot nitrous at idle, 8,000 RPM for several years, it never failed. But I kept the factory harmonic damper.

I've broken 5 BPs now (bent rods, cracked piston, rings failed, crankshaft keyway damaged from vibrating damper off, bottom end wore slap out), and the only one I would say had a RPM-related failure is my current engine I reved to 8,800 I need to pull it and tear it down, something is worn out in the bottom end, and it vibrates, but it's vibrated since I built it so I suspect it could be my fault anyways and extra RPM didn't help.

18psi

iTrader: (76)

I'm not sure I agree with your loic. At all. You say "I blew up......but it was due to" over and over, and I'm really curious how you know that the bent rods were from the boost/nitrous only and not overrevving?
Some parts/engines die slowly and some abruptly, but without a serious professional analysis I don't think anyone can ever make a factual claim such as "it broke from ....."
But just my opinion.

If you told me " I ran this engine for 50k miles, revving to 8 every day, and it's still in the car, and still working fine, and here are pictures (or evidence such as comp and l/d tests) that everything is in fact still peachy" I would be thoroughly impressed.

hrk

iTrader: (6)

Mine was at 8000, but had to drop it to 7400 soft 7500 hard after having the issues requiring key cycle to reboot the MS3x.

Engine specs, VVT -01, fully balanced, Belfab Rods, Wiseco pistons 84.5 mm, supertech oversize valves, supertech single springs, hard lifters with manley subs, stock cams BP oil pump, stock damper, light Fidanza flywheel reinforced block.

Max power at 6200 rpm, but there are advantages on some straights to save two gearshifts.

patsmx5

iTrader: (16)

I've posted it before when it happened. My nitrous malfunctioned, it hit 100 shot at idle, blew head gasket, bent rods, motor had a vibration to it afterward. I did a compression test to confirm hg was blown, repaired it, then noticed I still had low compression on 2 cylinders, was 15 lower, one about 30. Dropped a 3/8 extension down the spark plug hole and sure enough, cylinder down 30 PSI, the piston didn't come up as high as the others! So yes, it was confirmed.

patsmx5

iTrader: (16)

And so far I can't keep a BP alive for 50K without breaking it, so don't be looking for that post from me anytime soon!

18psi

iTrader: (76)

I know that's what finally broke the camels back, but you're missing the point.

My 99 had a 5sp at 300whp. I was "fine" on it for 2 years, after I sold it the kid grenaded it in 1 month. I blew my stock 99 engine at 240wtq from a melted ringland, but after I yanked the rods all 4 were bent.

See where I'm going with this?

Anyways, sorry for off topic. I'll shut up now.

DNMakinson

iTrader: (3)

RPM Limit: 7200 hard, 7000 soft
Built engine: No
Engine Specs: BP4W Stock
Track the car: Not yet
Avg number of times your car sees redline/day: Lately only occasionally.

Interesting thing with the soft limit (fuel cut) on MS3. It progressively cuts fuel to the various cylinders (don't remember if it rotates or just kills 1, then 4, then 3; or some such). Regardless, it is truly a soft limit, and if I held it, I'm not sure it would even rev to the hard limit. Last log I have, by the time I feel the falling off of power, I have lifted before I hit 7100 (half way). I think it is a really good cut.

Here is a picture of the soft cut coming in. Got to 7100, and then started down a little. Not bad at all, I don't think.



It did flash check engine light, so I think it went either hard cut or AFR cut, but only for a moment as I let off. I did not get a code flash.

Later, I held it, on a slight downhill, and it did go to hard cut.

TurboTim

iTrader: (9)

I voted what I ran my stock '94 BP at:

RPM Limit: 7400
Built engine: All stock internally
Engine Specs: 14psi GT2560R
Track the car: AutoX rarely
Avg number of times your car sees redline/day: zero

I shift when it stops pulling, which with the 2560/BP was well before 7400.

I have the V6 set at 8500rpm but I never get there either.

BP @ 7400rpm: 4127 ft/min
KL @ 8500: 4137 ft/min

yenadar

6500 soft, 7,000 hard
Built: no
Engine: Stock MSM engine block + internals
Track the car: Several times a year
Limit per day: Not usually.

Since the car is also my DD, it's not worth risking early engine failure to rev it higher, plenty of torque lower for DD (and 3.63 gears to make that wider MPH range) that I only rarely top even 6k on the street. On the track, the reasoning change but the results are the same. Since I drive to and from the track I'd really rather not make a money shift, and grabbing the wrong gear when tired at the end of the weekend from 6,500rpm means i've got a substantial amount of extra time to catch it and abort before I hit really costly rev numbers.

If I was competing I'd have a different opinion, but I'm not.

So yeah, i've left the rev limit at the factory MSM value. Fully aware I could go higher, I just don't feel a need to.

OGRacing

iTrader: (1)

I'll post one just to Give some variety...

RPM Limit: Nasa weekends 6000rpm, street/autocross 7000rpm i bump down the rpm for nasa to kill the peak hp number. in an attempt to be classed lower then TTU.
Built engine: last year no, this year yes. (2015)
Engine Specs: Custom Grind cam 228/237 @.50 .575/.575 lift @112 lsa, Texas speed Cnc ported heads, larger valves "manley" intake and exhaust. double roller timing chain, slp oil pump, Probe pistons, LS2 rods, stock crank.

Track the car: track, street,drift.. it's the car i drive when i feel like doing something stupid.
Avg number of times your car sees redline/day: 90% of it's life.

current state

cyotani

iTrader: (8)

Why not reduce timing in the higher rpm range to reduce TQ/HP and keep you under the limit which would give you a broader powerband? (flat HP curve based on regulations)

OGRacing

iTrader: (1)

that is an option. On ls motors the more timing pulled the hotter the engine runs. so i'm trying to avoid that. also my ecu self learns, so it's constantly tuning. so instead of loading different maps sacrificing the tune it's learned, i just knock the main rpm down. i still have 300ft lbs of tq at 2000 rpm so i'm never waiting for the power.

cyotani

iTrader: (8)

Oh got it. I didn't notice that wasn't a miata engine in that pic. What ECU are you running?

OGRacing

iTrader: (1)

i got a holley hp.efi the thing is sick. i love it.