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Advanced RPM limit settings for an SR20det

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Hi,

I am running a Link G4+ and wanted to see if anyone has some insight into good rpm limit settings for my SR20 that's kind on the rockers. I've attached what I am currently running and would like some opinions. It has solid lifters, Tomei duel valve springs and Tomei 270deg solid pro cams. Limiter is set as 7800rpm. Was tuned yesterday and is making around 390kw @24psi on 98 octane.

I have thrown a rocker on my last motor with the same specs and destroyed it so that's why I am a little weary now but I'm not 100% sure it was the limiter that caused the problem last time.

Attached Files

Have you logged what happens to the RPMs when you hit the rev limiter (WOT and/or part throttle)? Does it work keeping the revs in control?

Other than that, I'd definitely look into some rocker arm stoppers. They're not the cure, but definitely help.

Try to make it as soft as possible. Log Engine Speed ROC at 100Hz.

If you make the control range bigger, the limiter feels softer. You xan also lower the start cut a bit.

Don't use ign cut in any case on Sr20!

Thanks guys,

I am already running rocker stoppers, which probably did more harm than good on my last motor as it dropped a rocker but it didn't break it jammed under the cam and held the valves open.

I will make the limit range bigger and set up the logging as you said, thanks Adrian.

What rpm does it make peak power at?

Peak power at 7300rpm I’m running a gtx3582r obviously it’s far from a stock engine. It’s 2.3L and has a fair bit of head work.

What does Tomei say about max safe rpm for the parts you bought?

I would rev it much higher than 7800. Otherwise it's likely that rocker arms will wear very quickly. If you really want go above 8000 I would DLC cote cams and rockers. Or much better use a Sr20VET cylinder head.

Not an engine I'm familiar with, so sorry if these are 'granny - eggs' questions and I would appreciate answers that inform for further use.

Usual causes of rocker breakage are overloading and/or fatique failure - is this a known problem due to high lift acc'ns and valve spring pressures on NA engines as well?

Second most common is an uncontrolled valve train due to insufficient spring pressures and/or spring instability resulting in excessive clearances occuring and violent collision of parts, which even if not instantly destructive, can rapidly lead to the above.

Third most common is insufficient coil to coil clearances at full lift causing localised coil bind as the spring oscillates - again, would be a known problem and checked for but...

Fourth, with turbocharged (and supercharged on the intake side) there is a, often very high in the exhaust with smaller hot-sides, manifold pressure that the springs have to seal against that can also increase the chance of valve float, which can lead to severe component damage.

That said, some engines are known to have design features that can compromise high rpm and/or lift camshaft designs - is this one of them?