Increasing rev limit?

[JimX]

I'm wondering if there is any benefit to increasing the rev limit to around say 7500 on a R33 GTS-t with stock internals. I'm mainly asking this because GTS-t VSPEC's car makes its peak power at 7200rpm, so I would have thought that there would be some benefit to increasing the redline if tuned properly. Will it significantly shorten the life of the engine to add on another 500rpm?

[sewid]

I thought the rev limiter was set to around 7200rpm stock. I often see my needle zip past the 7000 mark on my stock ECU'd car.

[Guest RedLineGTR]

usally the stock turbo on a skyline is small since its good for spooling down below it usally runs out of puff when it get to maybe 7000rpm or about less depends on what mods u have etc but get your car on the dyno and see how the power graph turns out. UNless u have a aftermarket turbo it usally dosent do much.

[JimX]

Well, I have the aftermarket turbo already It's an old T04E though, so I'm not sure if that would run like crap past 7000rpm. The only real advantage of it over the stock item is the boost can safely be increase well past 14psi due to the steel wheels. Probably 18psi or so. It supposedly flows 450hp according to the previous owner but without the specs it's impossible to confirm.

I can always experiment with different tuning once my PowerFC arrives, I guess my primary concern was on engine reliability.

[GTS-t VSPEC]

JimX, I have my redline set at 7500, and tend to make peak power around 7200rpm, and don't get much drop off in power after that. Most stock GTS-t's tend to drop off quite alot after about 6900rpm, but after I change a few things to my air-flow setup, including the Greddy plenum (await's Sydneykids flamming) the power doesn't drop off nearly as much.

I've had the 7500 limit for over 6months now and even with 400+rwhp is hasn't killed the pistons. My advice is once you have the PowerFC in then check to see if the power drops off, if it doesn't then you can push the limiter out a bit further.

[JimX]

Thanks for that. Now all I have to do is wait for the PowerFC to arrive. (where the hell is it?!)

[Steve]

JimX, I think Merli has been tuning his with 8000rpm limit and running around like that for a while - he doesnt run out of puff, but has a different turbo (HKS 3040) and cams.

I believe that where a car makes peak power can be influenced by alot of things, cams, turbo, manfold, plenum etc Just depends on your setup and what works well with what you have.

I hope to be tuning my car properly soon (getting bits fitted), and will be trying 7500 and maybe 8000 redline - just for shits and giggles, so I will let you know how it goes then.

[Busky2k]

The increased rev limit should be fine, but I dont recommend holding the car on the rev limiter for any period of time (like during burnouts) as there is a possibility you may get valve bounce >7500rpm.

[JimX]

Busky2k, good point. I'm guessing that a variable rev limit (ie, dropping it back below 7000 if held for more than a second or 2) isn't something a PowerFC is capable of doing? Not that I want to do burnouts

[Duncan]

sewid, I found on the weekend when running with a PFC that my tacho was about 10% high, I thought the stock limit was 7200 as well, but its actually 7000.

As for raising the rev limit, you need to get a dyno graph, convert from speed to revs, and then calculate the range you need for each gear. It would be unusual for a stock gtst to make peak power over 6500rpm, and the important figure is the average power over the rev range you will need to use.

[Steve]

Originally posted by Duncan

....

It would be unusual for a stock gtst to make peak power over 6500rpm, and the important figure is the average power over the rev range you will need to use.

I would have to disagree, a good setup, from what I have seen will make power well past 7000rpm.

My car has 7200 rpm redline (from power fc) and it pulls all the way, torque doenst even drop off - still heaps to come and its only a 'quick' tune until the cams and headgasket get fitted.

[sewid]

Originally posted by Duncan

sewid, I found on the weekend when running with a PFC that my tacho was about 10% high, I thought the stock limit was 7200 as well, but its actually 7000.

Thanks. It figures. 7000 it is then.

[Duncan]

Originally posted by Steve

I would have to disagree, a good setup, from what I have seen will make power well past 7000rpm.  

My car has 7200 rpm redline (from power fc) and it pulls all the way, torque doenst even drop off - still heaps to come and its only a 'quick' tune until the cams and headgasket get fitted.

Sure, to clarify I mean a stock gtst. Changing zorst, intake manifolds, computer would certainly allow you to change the power curve.