Turbo

[Derby]

Originally Posted by R33

big ASS turbo + short ratio 6 speed seq = really good lap time!

Sorry r33 but think about the peak torque. it will be at high rpms. in combo with the close ratio it will generate a lot of wheel spin. and that isn't always the fastest...and shifting is breaking the power distribution so no accelaration for some time. (i know it is short but it will get longer if you shift more) on the other hand you get keep it in a thight power band.

try to make the ratios ina way that when you shift on top power you will get down at top torque. so from peak to torque to peak power and again top torque. that is the fastest accelaration.

Derby

[R33]

Derby, that's excellent advice! Never thought about that! Looking at my dyno chart now, my peak torque is at about 6400rpm while my peak power is at around 7400rpm. The car is self limited at 8500rpm. I suppose I could shift at 8000rpm in every gear. With shifting rpm diffrence at around 2000rpm, I will end up at 6000rpm upon upshifting. Just about nice....

[SkylineUSA]

R33,

So, for every shift you have 2000rpm difference? I know you know more about this stuff than I do, but it seems to me, that 8000 would be a litttle out of your power band?

Can you post your dyno sheet?

From looking at your car specs, I would have figured your power band would have been a little higher, shows you what I know

[R33]

Sky, I don't hv a scaner. But here it goes:

4000rpm: 130hp power/23kg-m torque
4500rpm: 190/31
5000rpm: 255/37
5500rpm: 340/41
6000rpm: 410/49
6600rpm: 460/51 (peak torque)
7400rpm: 480 (peak power)/46.5

All figures are on all four wheels using Dynojet at 1.3 bar of boost utilising F Con S. It doesn't look that pretty but is pretty responsive from 4000rpm. It's lovely around the long sweeping corners (turn 3/5/6/7/8/12/13 and of course on the back n front straight at the F1 circuit. (Go here http://news.bbc.co.uk/sport1/hi/moto...de/3517461.stm for a turn to turn guide by Jarno Truli around the circuit.)
But along the tighter corners, the car does bog down a bit especially at the very tight turn 9 (almost 180 degree uphill!).
By the end of the year, thge 2530s will be in place, hopefully!

[Derby]

So that dyno chart looks pretty awesome.

responsive from 4000 is good. for a tuned engine it is.

shifting at 8000 isn't the best strategy. use your boost, so shift a little earlier. torque proppels the cars forward. and the torque is pretty high at low revs (thanks to the boost) and climbs very hard up to 6000 after that it drops very hard a rpm range you don't want to be to long.

In general it is usual to shift late (after peak power) with NA engines and at peak power with charged engines.

I'm looking forward to the charts with the 2530's

Derby

[R33]

Thanks Derby 4 the comment. On the track, I normally stay below 8200rpm, even on the straights. Actually, I am not a "greedy" person! I don't hv much complain about the power range and delivery of my car. Except there are corners which I really struggle (eg turn 9 uphill, which immediately swerve to another right turn! - the Evos always gimme a wave around here! )
The 2530s will prolly be set up by the end of the year. I will prolly use a different set of cams to improve response. Will keep u all posted.

[SkylineUSA]

R33,

What tire size do you use?

Have you talked to anyone about the CAMs selection? If so, what was the outcome?

Cam selection should be based on the heads ability to move air. % wise, from what the intake side can move, compared to what the exhaust side can move. My only problem is I have never seen the actual flow rate of the RB26 heads.

[R33]

Tyres are 275/35/18.
I hv spoken to 2 mechanics about the cams. One says to mix them like my current combo ie 264/272. The larger exhaust cam keeps out the gasses better and should improve response.
Another mech suggests a pair of 264s but with only 8.4 (or is it 8.5?) degrees of lift to ensure good response. I know a guy who uses that cam on his R33 with TO4R...good response...even better than my current 2540s!
Still undecided though. As for the flow rate, well, as I had said b4, I know almost nuts about engines! And it goes without saying that I am unable to help u in that regard!

[SkylineUSA]

The smaller cam will drop your shift point, not by much, but it should drop.

To tell you the truth, you might just want to change out the exhaust cam. I know the is a huge science when it comes to cams, which most of the GTR world is in the dark, but you will not see any major difference in a 9.1 lift, and a 8.5 lift when it comes to throttle response.

I have seen RB26s set up in all ways. The same cams, bigger on the intake, bigger on the exhaust. These are cars set-up by TUNERS. Which is correct, I do not know?

I always revert back to turbo Mustang thinking. Funning thing there is, they do the same thing.

I do know that a wide lobe sep is good, around 114* or higher. That is always the case.

In N/A cars you always run a bigger exhaust lobe, but in turbos the thinking is different. That is why I would be inclined to keep your intake cam, and go with a smaller exhaust. Is it written in stone some where that this is right, no. For the simple fact that no one really talks about it. With my limited knowledge, that how I would set it up.

Actually, if I were setting up your car. I would do a bunch of things that go against the grain of thinking, but I am a novice. So, take what I say with a grain of salt

If you really want to know what I think, PM me.

That one track you mentioned, is that the track you are mainly racing at?

[R33]

Sky, thanks for the advice. You are right, it's like some kind of black magic. Some says small intgake bigger exhaust and some say otherwise. Say go with lower lift and some don't! Just yesterday, I met a mechanic who told me to maintain my current cam set up! However, I value all advices, although I don't really understand what they mean sometimes! I will of course PM you when I am about to finalise the rebuilding later in the year. Thanks for the offer.

That track is the Sepang F1 track, about 40 minute slow drive away from the capital. You can see it on TV this weekend as the F1 race will be held there. It's a highly technical track with 2 straights but with wide track and so it gives a lot of opportunity to overtake even around the some of the long sweeping corners. That makes the track very challenging. And yes, that is where I race.

[SkylineUSA]

That link you posted is awesome.

With so many different opinions on cam set up, I wonder if anyone has really tested all the options. In the US, we have mag articles left and right, of them doing swap out, on the same car, same dyno, same engine, so you can compare each to a given engine set-up. I have never seen or heard of anyone being able to that with the RB26. It probably has been done by many people, but they keep the figures to them selves.

Personnaly, I would look to see how the big guys are doing it, top secret, NISMO, and copy what their set-ups are. They would be the guys that have done the test, but just do not publish the results. At least that is my thinking.

[Derby]

Speaking is silver, saying nothing at all is gold.

Of course they don't tell the cam setup. It is to magical to give that info. It is like putting the ECU tables on the net for download. They have to be better at something then the normal 'tuner'

Gt-power suite is a computer simulation program for intake and exhaust systems.
I have taken a look in the graphs of a friend of mine who is playing with cams for his turbo engine. He was looking for the best overlap. and after doing some simulation runs. (12 degrees 30 and 42) he came to the conclusion that it doesn't make a big difference. the only thing that differ was the VE at high revs. After the top-VE.

He did not play with different opening and closing times. But with the good programs the home-tuner can have the same data as a top secret.

Is there nobody who ever ordered a cam and did some measuring...?

Derby

[flylwsi]

in regards to having a water cooled turbo so you don't have to use a turbo timer, where did that come from?

the oil is still in there for lubrication, and if you just turn the turbo off, without the timer, you're still going to coke the oil in the turbo, and kill it, regardless of whether it's water cooled.

so if that's your only reason, you need to rearrange your priorities.

[SkylineUSA]

Originally Posted by Derby

Speaking is silver, saying nothing at all is gold.

Of course they don't tell the cam setup. It is to magical to give that info. It is like putting the ECU tables on the net for download. They have to be better at something then the normal 'tuner'

Gt-power suite is a computer simulation program for intake and exhaust systems.
I have taken a look in the graphs of a friend of mine who is playing with cams for his turbo engine. He was looking for the best overlap. and after doing some simulation runs. (12 degrees 30 and 42) he came to the conclusion that it doesn't make a big difference. the only thing that differ was the VE at high revs. After the top-VE.

He did not play with different opening and closing times. But with the good programs the home-tuner can have the same data as a top secret.

Is there nobody who ever ordered a cam and did some measuring...?

Derby

Its not the that the lobes have not been checked, its the fact that to get a true comparioson, you need to be able to swap 5 or 6 cams in one day, on the same car, on the same dyno.

You can swap a 302 cam in about 2 hours, but I would imagine it would take a little longer to do a RB26 cam.

[Derby]

oh in that way...sorry misunderstood...

yeah that is pretty hard to do...for sure...

Maybe this is a noob reaction but it is an overhead cam right? chain driven? or belt? then 2 hours should do it right...but you probably have a better view at things...


Derby