Upgrading from Tomei 260's to 270's Solids

[Master Chief]

Steeve - you say : "I suggest you stick with 260 cams or possibly go with 264 HKS solid compatible camshafts for even more mid-range. "

Why would 264 give me mor mid range, and 270's wont ?

Also, i dont really understand - what is the theory about using smaller/bigger pleanums and low end torque on a turbo engine ?

About the Cams - if everything shifts up 500RPM, but i still make power, up top, then it wont be so bad i guess - providing i can rev 500RPM higher, then i do today.

Anyway, any dyno numbers, on the torque/power difrence, of 260 and 270 cams, on the same engine/turbo etc. ???

[Monooxide]

Originally Posted by Master Chief

Steeve - you say : "I suggest you stick with 260 cams or possibly go with 264 HKS solid compatible camshafts for even more mid-range. "

Why would 264 give me mor mid range, and 270's wont ?

Also, i dont really understand - what is the theory about using smaller/bigger pleanums and low end torque on a turbo engine ?

About the Cams - if everything shifts up 500RPM, but i still make power, up top, then it wont be so bad i guess - providing i can rev 500RPM higher, then i do today.

Anyway, any dyno numbers, on the torque/power difrence, of 260 and 270 cams, on the same engine/turbo etc. ???

The different duration cams cause the valves to open and close at different times in relation to the stock cams which causes the engine to act differently as far as volumetric efficiency goes. The change in how the valves open/close causes a different resonance to occur in the intake manifold. This causes the engine to be more efficient in a different RPM range because this resonance lines up at a different time than the lower duaration cam and this happens to be later in RPM. Also the diameter and length of an intake manifold runner plays a role on how fast or slow the resonant wave travels through the runner which also decides when the resonant wave will be in "time" with the valve opening.

The stock cams and intake manifold reach their peak torque near 4000 RPM, this is because the length and diameter of the runner accompanied by the stock cams timing of the closing and opening events give a resonance to achieve this.

The higher the duration, shorter the runner and larger the diameter of the runner, the further into the RPM range your peak torque(or VE) will occur. Also the opposite is true for the opposite of all those attributes. The 264s will allow slightly more top end with less loss of spool-up and mid-range.

If you shift your torque curve 500 RPM to the right you'll run into the same complaint you're talking about at 7300. The curve will be almost identical, just shifted to the right. So you'll have that same loss in torque.

Basically, intake manifold and camshaft duration decide where you're going to make power.

[Master Chief]

Not quite sure what do you refer to when you say "resonance".

In any way, i knew that longer runer manifolds, are especialy good for NA engines, designed in such a way to cause a venturi effect, to speed up the air going into the cylinder.

I can see how that might help in going from VACCUM to BOOST transition.

But after that, building boost, this is not as neccesary, as the air speed is set by the pressure inside the manifold, and longer runners would just cause for more lag.

I dont see how longer runners can help, while your on boost.

Now, since it takes meaby half a second, to go from VACCUM to 1 or 2 PSI, when you floor it, i think runing longer runners, is wrong for a turbo setup, especialy a high boost setup, where the main problem is building boost after you lift off for a second (to change gear or whatever).

There is "Throttle response" and there is "Turbo treshhold" and "Turbo Lag".
Many confuse these in my opinion.
I am mainly concrend with the LAG bit.


Also not sure how a smalle pleanum can help.....The ideal pleanum for any setup, should be bigger or equal to half of the engine displacment.
Thats what i remeber anyway.


Also about shifting the power curve -U R right, it will be baisicly shaped the same, but hopefully - 500 RPM more to the right...that means the 383lbf would be at 7260 instead of 7260 - wich means 566hp, instead of 533.....that 33hp more, for 500RPM - not so bad.

Really hopping it will fall less now, as a higher duration will increase VE accross the board.
The only question is, wheter the TURBO, wont start choaking thing up.

I really hope that this setup has the 580-600hp @ 25PSI, in it.
Well see.

[Monooxide]

Well, as I mentioned previously you can google the topic of intake manifold resonance. Basically the air entering the cylinder comes to a stop when the valve closes this wave will "pool" up on the valve and return the opposite way at the speed of sound and will reach the end of the runner and enter a nodal state( not going to explain this) and return back down the runner. Now, when the wave is just about to hit the valve and the valve opens your air will have a more powerful cylinder filling.

This applies for N/A and turbo. The longer runners will help with spool up because the RPM they resonate at is a lower RPM, this increases your VE more towards your low end making your engine use the thermal energy more efficiently and help spool the turbo. I wasn't stating that it would help up top, I was solely mentioning that it would help response but you'd lose top end.

Originally Posted by Monooxide

Everything has its trade-offs. If you're wanting a little more response out of your car you can get rid of the Greddy intake manifold and return to the stock intake manifold, this will give you better spool up but unfortunately less top end.

You won't gain VE all across the board with higher duration cams, you're going to lose it down low and gain it up top. It's the nature of the beast.

[S14_Kouki]

Toda makes a 304 get that

[Master Chief]

I like and trust TOMEI, and i dont have a use for 304, with my turbo.

Moonoxide - meaby i didnt explain myself right, sying more VE across the board.

Check this out...
I took my dyno plost, and played a bit with the torque curve, to show you what i would like to see, more or less.

The blue line is the torque i got with the 260 HLA's, and the dark red, is the torque curve (more or brobably less) of what iam looking for.
I drew it like it is shifted to the right, but higher duration cams, would probably make for more torque , as well - so i drew it a bit higher.
Also i drew the DECLINE rate of it, as being smaller to the blue line..... basicly this is what iam aiming for - a streighter torqe curve.

I exagerated a bit probably, but this is just to explain my meaning.

[Monooxide]

Ah, I see. Yea, doesn't seem like TOO lofty of a goal. With the Solid lifters maybe you should rev even higher and make ALOT of power.

[Master Chief]

Originally Posted by Monooxide

Ah, I see. Yea, doesn't seem like TOO lofty of a goal. With the Solid lifters maybe you should rev even higher and make ALOT of power.

So you think my goal is realistic for the 270's ?

I really wouldnt like to rev more then i would need, to compensate for the later spool....

The big question is, wheter the Turbo housing, wont start choaking up top - well have to see about that.

[Monooxide]

When I did the calculations without taking into account a better top end efficiency and solely a torque curve shift it was like 55* WHP with guestimated torque values from the curve.

I don't think the .82 A/R housing should give you any problems.

I was just suggesting more Revs because it would mean more power and longer use of it.

[Master Chief]

Yes, i aggree about that - iam just concerned that higher revs, increase the chance of rockers flying/breaking etc...

To tell the truth - i'd be happy with reaching my goals, below 8000 RPM.

We'll see how it goes.
Thanks.

[juggernaut1]

Lol...mine is a street car not a racecar.

[fliprayzin240sx]

Well, Frank from GarageBozo has been out here in Okinawa with Ross Petty, been talking to him about the car and he said that if you want response, throw away the 272s. Its purely for making top end power but makes the GT3582R superlaggy. If you're running a stroker kit, it might be worth it. If still running a stock 86mm or even 87mm bore, 272s will still hurt the setup if you want it to be more responsive. He said 264s for sure.

He's gonna play around with my setting and tune the next couple of days, I dont think I'll get ahold of 260s to swap out my 272s. He said he can tune it and try to get as much response on it, but 260s will be my best bet if I want the car to be more responsive for drifting/gymkhana/auto-x.

[Master Chief]

Let us know how it went - i am curious to meaby see some dynoplots.

[Jake1992]

are there any results of this anyone ? sorry for brining an old thread back alive!