How many RPMs is the bottom end good for?

[RobDET]

What do you guys think is a reasonable redline with a fully build head?

I'm thinking 8,500 but lots of guys rev DSM motors to 9k once the head is built. I'm thinking of settnig the limiter at 8,500 and just shifting at 8000

[s13sr20chris]

shifting at 7500 you are already well into the 4000's for piston speed.

[RMiller]

Set the limiter at more like 8200 if you're shifting at 8000. Better safety margin.

[RobDET]

shifting at 7500 you are already well into the 4000's for piston speed.

Surely the bottom end good fore more than the stock redline...

[RobDET]

Set the limiter at more like 8200 if you're shifting at 8000. Better safety margin.

I'm going to set up the EMS so that when the clutch is in the limiter is around 5,500 to 6000. That should prevent over reving. The 8,500 was just a guess at the upper limit of the SR bottom end.

[RMiller]

I'm going to set up the EMS so that when the clutch is in the limiter is around 5,500 to 6000. That should prevent over reving. The 8,500 was just a guess at the upper limit of the SR bottom end.

That's good too, but when you break traction in gear you don't want to go someplace you don't need to be. Set it lower than 8500.

[RobDET]

That's sortof what i'm getting at. You guys don't think the SR bottom end can handle those kinds of RPM's? The SR is of course notorious for having RPM problems but that is from the head. Once the head is taken care of i would think the bottom could spin a bit higher. 8,500 is only 1000 past stock. That's only a 12% increase.

[s13sr20chris]

my bad i was taking it from a long term view. couple years=8000 i figure. of course this is so broad. important factors aredriving stylelocationmaintenanceetc.

if you want to spin 8000plus thats fine for the motor but i would reccomend using full synthetic oil with a 3000mile maximum interval. i would also reccomend a FULL warmup before driving hard and using a turbo timer. you know the basics right? i am keeping mine at 7500 as dont need any more revs on the stock turbo. i wont raise the rpms on mine till i have the powerband to do it with.

[RMiller]

That's sortof what i'm getting at. You guys don't think the SR bottom end can handle those kinds of RPM's? The SR is of course notorious for having RPM problems but that is from the head. Once the head is taken care of i would think the bottom could spin a bit higher. 8,500 is only 1000 past stock. That's only a 12% increase.

I think the bottom end can handle it, but it may not last as long. Piston speeds increase exponentially with engine speed, so they're not just going 12% faster. In particular, I'm thinking about the bearings. But maybe it would be better to set it higher, to make sure it doesn't get in the way. I'm sure you'll be fine.

[s13sr20chris]

rev limits suck. keep it high. the stress induced on an engine thats bumping the rev limiter must be huge. i would hate to see that happening from the inside eh? hitting the rev limiter should be a last and i mean last resort.

[s13sr20chris]

I think the bottom end can handle it, but it may not last as long. Piston speeds increase exponentially with engine speed, so they're not just going 12% faster. In particular, I'm thinking about the bearings. But maybe it would be better to set it higher, to make sure it doesn't get in the way. I'm sure you'll be fine.

main bearings work as a team so i dont worry much about them. its the rod bearings that have it rough. if you are building the engine then special attention should be payed to the reciprocating parts.

[RobDET]

Oah yah... i use Mobil 1 full synthetic every 2,500 miles. No joke. I also change my plugs every time i change the oil. AND I'm definatly not saying "What is the highest RPM i can sustain driving down the interstate" This would be just at the strip or for specific sections at the autocross.

I'm going to start with 8000 and see how that does for about a month then i'll creep up from there once i have enough bank to afford a new longblock.

[s13sr20chris]

8000 rpm is only 4520fpm so i would imagine its ok for once in a while.