Rb26 Rev Limit

[OBES]

Prob sounds a little funny, but unsure of what power its making at the moment as when i picked it up, the workshop had forgot to print out the graph for me. Have to go back once they open again....also, there's still a few little issues i have with the tuning that they have done (runs a little rough, couple of flat spots, etc).

Its already got a Bosch 040 pump in it, and have Sard 700cc injectors, Tomei 260 poncams and an adjustable fuel reg to go in next.

Im looking at getting the bottom end rebuilt also, I know that forged rods and pistons are a must...what other areas should i look at while rebuilding??

[wrxkilla]

My R32 GTR (i just sold it last week)

was revving to 8500rpm. Tomei rods, pistons, cams. stock crank. was fine when i had it.

but with anything.

Big Revs & Big Boost = Big Bangs

hahaha

nah seriously, sustained thrashing, repeated high revs with high boost is bound to cause more wear and tear on a motor and shorten its life.

theres prople running 9000, 10000, 11000 rpms on RB26s...

depends on the exact hardware....

just how often to you want to rebuild it

[bfi.inc]

Revs dont always = more power.A person of moderate intelligence would do a power run on a dyno,see where max.power is made and where it starts to fall away.Then purchase a shift light and then set it to trigger 3-400 rpm below peak power.Generally the majority are suprised to see where peak power is made.Usually well before this 8500 crap.

[wrxkilla]

lol

what you are describing is not always the case either...

i might not be making more power at 8500 than 7500, the more average revs you have your car in the max powerband the faster it would be.

so for example.

4500rpm - 200kw

5500rpm - 250kw

6500rpm - 275kw

7500rpm - 310kw

8500rpm - 295kw

So in this case my average power accross this range is: 266kw

If i change my limiter to 7500rpm it is 258kw

Thats a lame example but proves the point. In my Case it was more extreme and was very helpful to have a higher average power output.

thanks

Michael

[Rolls]

Then purchase a shift light and then set it to trigger 3-400 rpm below peak power.Generally the majority are suprised to see where peak power is made.Usually well before this 8500 crap.

<{POST_SNAPBACK}>

Wouldnt you want to set it 400-500rpm above max power so that when you shift it doesnt dip much below max power?

[bfi.inc]

Wouldnt you want to set it 400-500rpm above max power so that when you shift it doesnt dip much below max power?

<{POST_SNAPBACK}>

no because reaction time.light triggers so by the time you shift,you are at about max Power.

[bfi.inc]

lol

what you are describing is not always the case either...

i might not be making more power at 8500 than 7500, the more average revs you have your car in the max powerband the faster it would be.

so for example.

4500rpm - 200kw

5500rpm - 250kw

6500rpm - 275kw

7500rpm - 310kw

8500rpm - 295kw

So in this case my average power accross this range is: 266kw

If i change my limiter to 7500rpm it is 258kw

Thats a lame example but proves the point. In my Case it was more extreme and was very helpful to have a higher average power output.

thanks

Michael

<{POST_SNAPBACK}>

Average power?? thats for dyno comps.In real world,once u pass max power mark,you are going slower.Revving uselessly for no gain

[Rolls]

no because reaction time.light triggers so by the time you shift,you are at about max Power.

<{POST_SNAPBACK}>

Im talking about on a track, surely you would want to shift slightly above max power, it makes more sense and everyone has always told me to do it as this way you will have more power in the next gear.

eg.

let use the above dyno results and assume a 2k drop in revs.

Shift at 7500rpm 310kw and it drops to 5500rpm at 250kw average power = 278kw

or shift at 8500rpm at 295kw and it drops to 6500rpm at 275kw average power = 293kw

Shifting higher = more power available across the spread.

Yes you are correct you wont be making as much power at the top of the gear but once you change gear you will be making more then if you shift lower and hence your overall average power will be higher. Say once your in a high gear like 4-5th and the revs dont drop as much you could work it out and probably shift much lower then in early gears like 1-3rd

[The Admiral]

Not sure of what exactly needs done to rev high, but probably stronger crank bearings for a start...

As for the change point, you are always going to accelerate faster by revving an engine out, due to the increase in tractive effort (torque applied to the road) in a lower gear - gears are just torque multipliers...

Revs are a very good way to more power - which is just a factor of torque x revs - my T78 spools after 5k (maybe 4.5k in higher gears) and would be a pain to drive if the engine wasn't built for 8500rpm...

Cheers

Rog

[wrxkilla]

Average power?? thats for dyno comps.In real world,once u pass max power mark,you are going slower.Revving uselessly for no gain

<{POST_SNAPBACK}>

BZZZZZZ. WRONG.

have a think about it...

heres one of my first dyno sheets. this wasnt how it currently is but its a great example...

all kw at 4 wheels

http://www.gunnamotorsport.com/wrxkilla/415.GIF

So with a 7500 limiter i change gear and it goes back to 4500rpm and accelerated again..

4500rpm -100kw

5000rpm -140kw

5500rpm - 190kw

6000rpm - 280kw

6500rpm - 330kw

7000rpm - 380kw

7500rpm - 415kw

Average 262kw

With an 8500 limiter i change gear it goes back to 5500rpm (note last 2 are guess as its not plotted obviously)

5500rpm - 190kw

6000rpm - 280kw

6500rpm - 330kw

7000rpm - 380kw

7500rpm - 415kw

8000rpm - 410kw

8500rpm - 400kw

Average 343kw

Now Peak power means nothing. Your telling me that if i have an average of 80kw more accross my rev range (thats used through the gears) it not going to be faster?

your argument makes no sense...

lol

Sure helped me at the track...

michael

[RB30-POWER]

shouldn't you look at torque moreso?

you want a huge torque curve from idle to redline, big and flat!

(haha well your not gunna get torque from idle on a small capacity RB) but the idea remains, huge wide torque band/curve for quick times.

[wrxkilla]

yep but for me a similar scenario applied.

heres an earlier graph again with tractiv effort

http://www.gunnamotorsport.com/wrxkilla/415TE.GIF

mick

[The Admiral]

Tractive effort curves are the best - i.e. torque at the road.

e.g.:

You see how tractive effort decreases in each gear, and you should change up when the lower gear curve drops as low as the next gear's tractive effort...

Cheers

Rog