I went to the track last weekend and found myself pushing my 3rd gear as hard as possible up to nearly 7k limit because it was at the very end of the strip. I haven’t had a chance to dig out my dyno sheet to see where my power ends to see if i was actually losing power. But I was just wondering how unsafe this is to do?
can a b204l head really take this much abuse? and cause no floating valves?
I got really scared because that day a built +400whp integra had a exhaust valve that floated and broke apart his spring and know most of the top end is toast. he was going up to 9k rpm though....
I have been running my head to 7k for a couple of years now, but I recently put in the stiffer valve springs from Nick.
You are definetely not making peak power up there. Even with my gt3071 .64ar and stock cams, I was starting to fall off at 5700rpm in third gear. I went faster in the 1/4 mile by short shifting, shifting at 5700rpm instead of winding it all the way out to 7k.
When you feel the torque and power start to fall off, shift! The nose will even start to drop on you...
Every dyno I have ever had showed my car making peak power right when they shut down at 6500rpm. This is 3 different setups that have all produced pretty much the same result!
I don't know if my car is a fluke or what.
Torque peak always drops off, but hp just keeps going up!
Just remember wear accelerates with higher revs.. The stock pistons dont really like that much speed. On a 2.0 it is not that much of a problem though.. I turn my Vig to 7200 but that same piston speed with the shorter 2.0 crank is like 8500! So it is less of a problem on the 2.0, now that is ignoring power. actually getting enough torque (airflow) up there is the hard part.
I wasnt reving out my engine for power, I know that the trq falls pretty hard around 6k, I was reving it out so that when I shifted id be right back into my trq band.
You want to shift right after the torque falls off and the hp takes over. Lookin at you're dyno sheet will show you exactly where that is in the rpm, but you can also feel it when the torque starts to fall..
Look at my dyno, check where the torque line falls below the hp line and that is right about where you would want to shift and were you will go the fastest.
On my dyno graph with gt3071 .64ar stock cams, I would shift at 5500rpm here where you see the hp take over after the torque has dropped below the hp line...
The only reason I'll rev mine out would be in a situation where shifting would cost me more time than bouncing off the rev limiter. This last weekend's autocross was an excellent example of that for me - very tight, too tight for a 9000.
Yup, that is one time you do want to keep winding it out and if you need to keep winding it another 500rpm so that you drop right back into the sweet spot of you're power band, then that is well worth it...
I wind second as far as I can even though I am just cruising after 6500rpm and that way I fall back to my sweet spot in third gear. If I shift too early, the wait time for spool kills my speed.
bear in mind also that the gear-ratio is a multiplier for torque and the it needs to really fall on its face in the engine if you want to end up in a situation where the wheeltq would be larger in the next gear up.
Look into this tread where you can see the values calucalated http://www.saablink.net/forum/showthread.php?t=28363
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