Raising the Rev Limiter

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Aug 21, 2007 | 03:45 PM

ltborg

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Drifting

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From: San Angelo TX

Raising the Rev Limiter

just wondering why the rev limiter is set to 6000 rpm on the ls1 and what would need to be done to safely raise it (other than reprogramming it)? the only thing ive found is the potential for valve float above 6500 so would replacing the stock springs with dual springs, ti retainers, etc fix that? is there anything else that would prevent you from reving the engine higher? tia

Aug 21, 2007 | 04:49 PM

BlackZ06

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From: San Rafael CA

Here's my thoughts on it ... for what they're worth ...

1) Part of the reason a Z06 has a 6500 redline is because, yes, the valve springs are different from those in an LS1. From a Hib Halverson article on the Idavette website ....

In our interview with Jim Hicks, we learned the LS6 spring is made of different material (chrome/silicon/vanadium steel wire vs LS1’s chrome/silicon steel wire) and has a different wire shape (oval vs. round), as well as, being wound more tightly. These three features make a big difference in valve spring pressure: on the seat, 90 lbs for the LS6 vs. 76lbs for the LS1, and over the nose, 260lbs for the LS6 vs 220lbs for LS1.

So you could probably raise the redline by installing new valve springs.

2) Without changing the camshaft, there'd be no real advantage to an LS1 running to 6500 RPM. Take a look at a dyno of a stock LS1 and you'll see that the engine, at 6000 RPM, is starting to fall out of its "power band". See ....

http://www.corvettemuseum.com/specs/...ages/graph.jpg

Note that Torque for the LS1 starts dropping off at about 4800 RPM, and HP is starting to drop after 6000 RPM.

You'd be better off shifting an LS1 at 6000 RPM to get back into the powerband unless you make a cam change.

Aug 21, 2007 | 09:25 PM

Bink

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St. Jude Donor '09

Major reason for the lower redline of the ls1 -> rod bolts. They were upgraded with the LS6 (2001) and I believe later (post-2001) LS1s.
You can purchase LS6 or Katech rod bolts and have them switched- without dropping the engine.

LS1s were used in the ASA series (Stock car). Hard running proved the rod bolts to be a weak link....which GM fixed and later upgraded. Racing pays off!

Sometimes it better to push the revs than take the time to shift-roadracing and autocrossing.

I looked up the Katech bolts and inf ->>http://www.katechengines.com/street_...etail.php?id=5

Last edited by Bink; Aug 21, 2007 at 09:31 PM.

Aug 21, 2007 | 09:42 PM

ltborg

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Drifting

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From: San Angelo TX

Quote:

Originally Posted by Bink

Sometimes it better to push the revs than take the time to shift-roadracing and autocrossing.

That's exactly why I'm asking about this. I've got the dyno plots from my car and yes the power is falling off slightly. Not sure if the recent addition of headers or the potential intake manifold swap will do anything in terms of shifting the power band, but if so, all the more reason to look into this. I've been getting killed by the gear/rev range at a few of the recent autocrosses I've been to. One of my friends was having the same issues at one of them so he pulled the chip for his rev limiter and just ran it and he shaved a huge amount off his time. That got me thinking that if it wasn't a big deal mechanically, I could set it for 300-500 more than it is and just use it when I need it like that but otherwise shift as normal. I just sold some heads without the Comp 921 springs so while I'm trying to sell the springs, if they end up just sitting much longer, why not use them since I've got them. That's good info on the rod bolts though. I didn't have any idea about that. Any issues with the bearings at higher revs?

Aug 22, 2007 | 08:29 PM

Bink

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St. Jude Donor '09

You don't really need to move it up...just pull back on the throttle a bit. Let it sail along at 5950 for a short distance.

I wouldn't use double springs if you don't have to...921s are doubles?

Definitely put the LS6 intake on ....it's an easy swap. Big improvement in bottom end tq.
See here->http://www.ls1howto.com/index.php?article=5

Aug 22, 2007 | 09:52 PM

ltborg

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Drifting

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From: San Angelo TX

Quote:

Originally Posted by Bink

yeah that's exactly what i do, just lift and wait. the last couple courses just involved a lot of waiting, inconvenient speeds in corners, etc.

comp 921 are doubles, there are pics in my for sale thread.

ive been debating between a mamo lsx and a ls6. if anyone has some dyno plots of the lsx (before and after) id be very interested in seeing them.

Aug 24, 2007 | 12:00 AM

0Tony Mamo @ AFR

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From: Valencia CA

Quote:

Originally Posted by ltborg

You would love the ported 90....more power at every RPM....slightly more at say 3K and building quickly (gapping up over the LS6) peaking some 20-25 RWHP more and carrying better past peak. I take an already superior manifold design (compared to the factory LS6) and make it better.....its not even fair....LOL

Here is a gragh that shows what Im describing above....the only other addition was a larger 85mm MAF but honestly at this power level (low 400's RWHP) it was probably only worth 2-3 if that.

I have seen many results of my ported FAST swap that mimic the gains above (or very close...average gains are probably 22-23 RWHP).

Feel free to PM or call me if you have any questions. My direct line at AFR is (661)775-2647

Thanks,
Tony