What RPM limit would you guys run your LNF to? I am curious to what the stock motor could rev up to and will the turbo be able to breath enough air into the motor?

 

Turbo stop making good power at about 5800 rpms

 

Dyno your car and learn.

It's not about what the motor can take, it's about whether it's even necessary. For instance: My rev is set at 7200 so that I can take it all the way to 7000 without risking hitting the limiter. I want to be able to shift at 7000 because I stop making power at ~6500, so when I shift I will be right back in the powerband.

 

7200 seems high anyone know when valve float occurs?

 

well roadrage is SC so it might be different for them mine is set at 6700

 

That only works if the LNF has the same valve train as the LSJ.

 

The LNF peak torque is about 4000 RPM. The stock turbo runs out of steam short of 6000 RPM. I don't see much reason to shift beyond 6k if you have the stock turbo. I haven't been to the drag strip to confirm this yet, but I will soon.

 

i was told by josh from ottp that the lsj can handle 7400 max, and that it wont hurt unless your constantly on the limiter

 

I'm confused, we're in the LNF section and the thread starter asked about LNF RPM limits. Remind me again, why are we discussing the LSJ?

 

After looking at several dynos it seems like it would be good to shift at 6k rpms and stay in the torque band.

 

GM and the FAQ on CED about stage 3 for the LSJ both say that valve float can happen at 7250. Above that you need upgraded valves and springs.

I'm not saying this to insult OTTP. They make good stuff, but they are not perfect either. Nobody is.

However, one thing to consider is that the LSJ is based off the L61 while the LNF is based off the LE5. And, even though the LE5 stock rev limiter is higher than the LNF, you need to consider final drive ratios, tranny gearing, etc. The LSJ final drive is 4.05 while the LNF is 3.82. This allows the LSJ to achieve a higher top speed, but the LNF has the advantage in acceleration. There is a correlation of engine speed with this too. Since I only know the basics I will leave it here and hope that somebody more knowledgable than me will explain more, if there is a need.

Point is, consider your gearing before you try to raise the rev limiter.

 

That is what I want to know. The only reason LNF info would help is if the LNF and LSJ had the same valve train and the guys was upgrading turbos.

 

^ You got that backwards.

 

Peak torque for the LNF according to GM is @2000rpm. Peak power @5300. Current rev limit @6300. It's fairly common for a tune to change the rev limit in the first two gears to 7000. What I get from that is-7000 is a good, reliable rev limit... when the engine doesn't have to spend much time at that range. 63-6500 are good rev limits for longer term durability when the egine has to spend more time up there. Judging from that, you'd PROBABLY start running into valve float at somewhere around 7500, but that's just speculation on my part.

 

If I'm not mistaken, the limit of the LNF comes from the limit of the injectors. They can only squirt up to 6500 or something (IDK exactly what it was). Regardless, the mechanical limits of the motor are not an issue until a faster firing injector can be made or found.

 

You are mistaken, people have revved the lnf past 7000rpm with ease. I personally wouldn't go past that, but some have gone to 7500 already, granted they have bigger turbo's.

 

im lifted to 7200 and I shift around 6600 because on my dno graph I have power till 6800 I hold a steady powerband of tq and hp from 5300 to 6800 then numbers drop

 

I'm looking at my dyno sheet and see power falling off after 6000 RPM, I see no reason to rev past that point with my current setup.

 

In the later gears no, but in first and second it does help because they're over very quickly.

 

LSJ guys, you have your own section.

Your confusing people please we don't care when you shift, no dis-respect.

After seeing the dyno charts and powerbands, 6200-6400 looks like a great place to shift

maybe at 6800 would be a good 1-2 shift because that gets high very quick

 

yeah, I was looking at my sheet, and the power dosnt drop for me it just hold steady but, if I shift I would be in a higher powerband again, my bad! Im gonna start shifting at 6000 in all gears except first cause thats just where evere the rpms are when I hit the clutch lol


Heres my question for some with a tune and some mods or even just a tune
I pin 2nd with traction control on and it hold the tires at a steady grip but rpms stay at 5500 for like 3 seconds while it trys to get grip as then when it does then move up again, bad idea or good idea, or when I turn traction control off and pinn it rpms scream to a 6000 and hold while the tires spin like hell screathing and leaving rubber in the street, then it grips rpms move and I shift

How do you guys go about pulling your 300+hp in low gears lol

 

You are the one who is mistaken. The injection window at 6300 is approx 5 mS (time it takes for the piston make the intake stroke) and the injection time is approx 5mS. If you rev higher than about 6500 your injection window is less than 5mS and your injection time is greater than 5mS. So you injection cycle carries over into the compression stroke. That wets the crap out of the piston and causes the combustion flame propegation to go to hell. Ask BTF or Area47. They will confirm what I just said. That is why those running big turbos power falls off at over 6500 no matter what size turbo it is.

I have mine set to go to 6800 but only to help prevent me from bouncing off the rev limiter in 1st and 2nd. Those gears are over very quickly for me because I get no traction. I think I might put some of the factory torque management back in. I actually spun a little in third at 50 mph when I rolled into it. Whoever said a 3" catback does nothing for these cars is wrong. I could never get it to spin in third before I put the catback on unless it was cold or wet out.

 

Ask btf how high he rev's...
While its true what you're saying about the injection window it doesn't mean the engine wont rev higher past 5ms and 6000rpm, everybody does it.

 

It would depend on what the stock turbo makes. If it runs out of breath at say 6500, there's no point in revving your motor higher because you aren't making any power anymore...However, I will be interested in seeing what someone will be making when they swap to a 50 or 60 trim turbo and get some valves and rev to 7500 or higher...That would prolly be some serious power.

 

Um 4.05:1 will produce less speed per rpm than 3.82:1 and more accelertion. Either you got the numbers backwards (ie lnf = 4.05 and lsj = 3.82) or you are confused.