Upgrading from Tomei 260's to 270's Solids

[Master Chief]

Hi all.

I am planing of going to a Tomei Solid lifter cam Setup.
Curently i have 260's.

I have a GT3582 that comes on full boost at about 4900-5000, and power goes up, until about 7000-7200 RPM, before it starts to drop off.
Max torque 435lb/ft, and max power 530hp @ HUBS on Dynapack.

I am trying to decide wheter to go with 260's Solids, for the Solid lifter upgrade, or go for 270's.

I want to be able to make power beyond 7000-7200, but i dont want the turbo to come in later than it does now.

Does anyone have any experience with upgrading from 260's to 270's, and can comment on the difference ?

Better yet, if someone knows of a dyno comperation or something...

Thanks,
Dany.

[Master Chief]

No one with some info on the subject - really need some help...

[jspaeth]

Originally Posted by Master Chief

No one with some info on the subject - really need some help...

I don't have any real experience with this, but my feeling is that the cams are not what is causing the spool to be as late as it is.

Changing from 260's--->270's shouldn't make it spool later I don't think.....but they should help it breathe better up top.

Plus, if it is already taking that long to spool, you might as well throw a greddy intake manifold on there and help it breathe out to much higher RPMS.

With that massive of a turbo, you should build a 9K solid head with some big cams and a Greddy Intake Mani so you can really keep making power out past 8K

[Master Chief]

The engine is fully built, and as said already made 530hp.
I do have a Greddy Intake BTW.

The spool is late, cuz the turbo is big - i can live with it as it is now - i am just concerned of it getting even later with Longer duration cams.

As for a solid head - thats exactly why iam asking, as i am building a solid head now - i just need to decide on the cams to use.

I had 260's hydraulic cams until now - and i want to know what to expect with 270's Solids.

Thanks.

[S13 curtis]

it waill spool it faster as it its moveing more air threw the motor with bigger cams, your power band will be good up top.

[juggernaut1]

I don't have any direct experience with the differences with those cams but bigger duration cams will make it spool later - thats what they do - they shift your boost, torque and power further up the rpm band.

BTW I run the 260 procams hla's and make peak hp at 7700rpm with a FR twinscroll 3071 and Hypertune plenum. I do have headwork though and run bigger ex valves. This setup also makes 24psi by 4000 rpm by retaining the VCT.

[jspaeth]

Originally Posted by juggernaut1

I don't have any direct experience with the differences with those cams but bigger duration cams will make it spool later - thats what they do - they shift your boost, torque and power further up the rpm band.

BTW I run the 260 procams hla's and make peak hp at 7700rpm with a FR twinscroll 3071 and Hypertune plenum. I do have headwork though and run bigger ex valves. This setup also makes 24psi by 4000 rpm by retaining the VCT.

In general I agree with you, but the power is already coming on so late, that I don't think 270s will make it come on later.

If you had a little turbo that made peak tq. by 3500 RPM, then I would agree that the big cams would make it laggier.

I just don't see 270s making this setup even laggier.

[juggernaut1]

For his sake I hope bigger cams don't make it laggier - but I'm just trying to understand the theory how bigger duration cams wouldn't make it laggier irrespective of the turbo.

Although he could use adjustable cam gears to tailor the rpm band of the power curve to some extent which would be dictated by the purpose of the car which we don't know.

[jspaeth]

I will hold off on arguing or insisting I am right, but maybe someone who really knows the answer will chime in.

My intuition says it won't hurt spool up at all.

[brndck]

i vote nos kit to help the turbo spool. sounds like this car is built for drag anyways.

[Master Chief]

juggernaut - what power are you making ? It sounds you have a very wide power band - 24PSI by 4000 sounds great, but what is hapening up top ?

The current setup of the car, serves me well in ocasionaly drives around town, Drag, track days etc..... With my older GT3071, i used to drift it too, but i kind of lost interest in that, for now.

Because loosing rockers a couple of times, i decided to go with a solid lifter conversion - and as i need to get new cams for this, i am trying to decide between the 260's and 270's, meany to get a bit more performance as well as reliability at the same time.

As for the boost comming on at 5000, its not that bad when you in the right gear...
I just woudnt want it to be later, as i am not planing to go past 8000-8500 RPM anyway.

Soo - does anyone have Tomei 270's on there car, and can coment on the behaviour of the engine - i.e. Idle, boost coming on, power up top, etc.

A dyno would be great.

Here is mine, at 25-26 PSI.


Here is a link to some more info on the setup.
http://www.sxoc.com/vbb/showthread.php?t=427381

[juggernaut1]

These are the only dyno's I have re the tune which as you can see were done a while ago. The tune was never completely finished because my tuner was borrowing a dyno on the day and ran out of dyno time. Also need to fix up the boost drop in the top end. Note the ambient temp was around 36 degrees when these were done. I have had it on another dyno since in cooler conditions and it made a couple of more psi across the board at the same rpm - for instance it was making 26 psi by 4000rpm - no printout to show unfortunately.

This dyno done in 4th gear - (5th is 1:1 in my car as I have a 6 speed close ratio Nismo box).....also shows 24psi by around 4000rpm even in 4th....5th gear (1:1) is better still.



Same dyno as above overlaid onto a different s15 with single scroll 3071 ex gate on 6boost manifold 256/256 poncams and stock intake.



This dyno done in 5th gear (1:1) after retarding the ex cam a couple of degrees - picked up more low and mid and lost top end - revved to 8,000rpm although shown in klm/h. Notice how it holds up power reasonably well at this rpm even with the 260 hla's......in any case the power nosing over is more likely attributable to the boost dropping as show in the dyno. Boost curve in general is a little rough

I know the scaling is crap on the horizontal line. One day I will get a better printout.

[juggernaut1]

Master Chief

I read your other thread links to get some background on your setup....from my understanding you are using Tomei Type A springs in this setup....I also read where you through a rocker on the dyno spinning to 8,000.

IMO the springs are no good to turn to 8,000...as evidenced by you throwing a rocker........in fact I think even Tomei only recommends 7500 with these springs. I also have these springs but the springs were shimmed by about 3mm to bring up the spring pressure to spin it to 8000rpm with the 260 HLA's. So high pressure or shimmed up springs will allow you to rev it further to take full advantage of the GT35R without requiring the use of a bigger cam.

Also are you currently taking advantage of the VCT.....if you are and if you move up to the 260 or 270 solids you can kiss that goodby and you will suffer poorer low/mid response as the VCT does help somewhat to spool the turbo and give better low end response.....and no amount of adjusting cam gears will restore the advantage that the low/mid torque the VCT provides.

I also understand you are running a Tial housig on this turbo which is basically T25 in size at the inlet. This could also pose a restriction at higher rpm as it simply won't have the flow capabilities. I only mention this because if you put in 270 cams for high rpm and the ex housing is a restriction at those rpm you may have gone backwards in a sense.

Finally, I see you are using the Greddy plenum on the stock lower runners. The lower runners are still relatively long and will hurt top end torque. Greddy now makes a one piece intake with shorter runners for the blacktop motor which would help your top end but it will also hurt your low/midrange. The lower runners are also quite restrictive as I had my stock intake hand ported and extrude honed and picked up nearly 50 cfm per runner - the lower runners had posed the most restriction and this is where most of the flow gains were made. However, I can't specifically report on the effectiveness of this mod as I ended up fitting the Hypertune intake/plenum.

Anyway these are my thoughts and experiences.

Cheers

[fliprayzin240sx]

I got 270s with Solids but I cant really give you much input. The shitty thing is we have no working dyno on island...cams right now are not dialed in. Full boost at 5k, starts spooling by 4k, redline and tuned up to 9k but I set my redline down to 8k daily and auto-x/HPDEs. Boost is set at 1.4 and 1.8, I'm too pussified to push it to 1.8bar.

[Teambadrun]

I run 260 Degree Tomei Solids

Friends Racing S15 runs 2.2KG/CM2 boost ( 32psi boost) and that is a TD06H-25G 10cm same as mine with NOS
that makes 662ps.........
I dont see why you would want 270 deg cams ... Maybe if it was purely a drag car????????????????

Our's are drift machines.

[Master Chief]

I hear you guys, and really appritiate the time you take to help me out.
I dissagree on the TIAL housing having a "t25" like sized inlet, beeing a restriction.
The inlet of the turbo housing, has no affect on flow - only the turbine A/R does.
If the inlet of the turbine is large enough to accomodate the turbine A/R - there is no restriction.

All turbo housing are constructed to have an equal or larger inlet then the maximum cross section area of the turbo housing. An area wich actualy dictaes the turbo A/R.

Fliprazin - what turbo do you have ? what A/R ?

I will be using SUPERTECH double springs with this setup, and defenetly want to go with the solid lifter setup.

I'll have to make up my mind between the 260 or 270.

If someone has more opinions, i'll be glad to hear them.

Thanks.

[juggernaut1]

Originally Posted by Master Chief

I dissagree on the TIAL housing having a "t25" like sized inlet, beeing a restriction.
The inlet of the turbo housing, has no affect on flow - only the turbine A/R does.
If the inlet of the turbine is large enough to accomodate the turbine A/R - there is no restriction.

All turbo housing are constructed to have an equal or larger inlet then the maximum cross section area of the turbo housing. An area wich actualy dictaes the turbo A/R.

I hear what your saying - but I don't see Garrett or any other turbo manufacturer using t25 inlet size on this size turbo. They are usually T3 and now I see T4 housings are available through ATP for the GT35.

Not a disagreement but just an observation.

Also have you considered staggering your cams i.e. 260 inlet and 270 exhaust is popular.

[Master Chief]

HKS for example use T25 inlet flanges on all but their "PRO" series turbos - including GT35 variations.
Also the Tial housing's flange is larger then a T25 - if speaking from flange area point of view.


I havent considered staggering them - i never really took the time to try to understand the benefith in that.
How would that help me ?

[s15specR]

Originally Posted by Master Chief

How would that help me ?

I'm interested in this explanation as well.

[fliprayzin240sx]

Originally Posted by Master Chief

I hear you guys, and really appritiate the time you take to help me out.
I dissagree on the TIAL housing having a "t25" like sized inlet, beeing a restriction.
The inlet of the turbo housing, has no affect on flow - only the turbine A/R does.
If the inlet of the turbine is large enough to accomodate the turbine A/R - there is no restriction.

All turbo housing are constructed to have an equal or larger inlet then the maximum cross section area of the turbo housing. An area wich actualy dictaes the turbo A/R.

Fliprazin - what turbo do you have ? what A/R ?

I will be using SUPERTECH double springs with this setup, and defenetly want to go with the solid lifter setup.

I'll have to make up my mind between the 260 or 270.

If someone has more opinions, i'll be glad to hear them.

Thanks.

Running the same turbo as you...GT3582R. Fully spooled at 5k with 270s on both intake and exhaust side. Why dont you try to run 260 on the intake side and 270 on the exhaust side?

[juggernaut1]

Originally Posted by Master Chief

HKS for example use T25 inlet flanges on all but their "PRO" series turbos - including GT35 variations.
Also the Tial housing's flange is larger then a T25 - if speaking from flange area point of view.


I havent considered staggering them - i never really took the time to try to understand the benefith in that.
How would that help me ?

Yes, you are right HKS use the T25 size on their 3040 (similar to GT35) and its a laggy thing. All their other turbos are smaller sized which is better suited to the T25 flange size. Having said that even a pair of HKS 2835 twins on an RB26 is slower to spool and makes less power than a GT35 with a T4 1.06 open housing.

I've had a T25 Tial flange housing and based on my calcs the opening is no bigger than a T25 Garrett from an area point of view.

Back on topic .....you gain response with the staggered setup - 256/264 HKS and Greddy Easy Cams for instance are common as well as 264/272 HKS staggered setups.

A few people in OZ initially used the Tomies 270/270 then swapped the inlet back to a 260 and noted an improvement in response for street/circuit duties. Also Camtech cams make a 255/260 combo and with a T3 .63 3071 20 psi is reached by around 3600rpm on an unbuilt SR20.

I think the smaller intake improves the spool which in turn leads to better cylinder filling and therefore torque/power at lower/mid rpm as evidence by numerous dyno's.

[Master Chief]

If i think about it a bit, the difrence between a 260/270 setup, to 270/270 one, would be the OVERLAP time.
260/270 would overlap less, wich i guess is what would help with response.

Interesting though.... I will research this further.

Tanks.

[Teambadrun]

Originally Posted by juggernaut1

These are the only dyno's I have re the tune which as you can see were done a while ago. The tune was never completely finished because my tuner was borrowing a dyno on the day and ran out of dyno time. Also need to fix up the boost drop in the top end. Note the ambient temp was around 36 degrees when these were done. I have had it on another dyno since in cooler conditions and it made a couple of more psi across the board at the same rpm - for instance it was making 26 psi by 4000rpm - no printout to show unfortunately.

This dyno done in 4th gear - (5th is 1:1 in my car as I have a 6 speed close ratio Nismo box).....also shows 24psi by around 4000rpm even in 4th....5th gear (1:1) is better still.



Same dyno as above overlaid onto a different s15 with single scroll 3071 ex gate on 6boost manifold 256/256 poncams and stock intake.



This dyno done in 5th gear (1:1) after retarding the ex cam a couple of degrees - picked up more low and mid and lost top end - revved to 8,000rpm although shown in klm/h. Notice how it holds up power reasonably well at this rpm even with the 260 hla's......in any case the power nosing over is more likely attributable to the boost dropping as show in the dyno. Boost curve in general is a little rough

I know the scaling is crap on the horizontal line. One day I will get a better printout.

That setup seems quite laggy too, you are making sweet fuck all power at 4000rpm and you claim thats full boost.. Who cares what "BOOST" you are making at LOW rpm it's about POWER @ low RPM...


Israel guy, you shouldn't worry about 270DEG cam's unless its purely drag.
Friends racing S15,( also myself) run a TD06H-25G 10cm and we make bucket loads of downlow POWER and super early boost... 260,260 12.0mm solid lifters.
HLA are really really really shit and you should definately just get 12mm 260 camshafts. Cam gear adjustment will depend on your setup, with big big turbos it might help you downlow by 20rwkw(30rwhp or so) but you will sacrifice topend.

[Geno750]

Given that you're using a 35R, and with the rev advantages solids would give you, I'd go with 270's. They would better match that turbo than 260's would.

[Monooxide]

There is a lot of good talk going on in this thread however I don't feel the question of the 260 vs. 270 cams was answered.

The 270 duration cams will cause the turbo to achieve full boost later. The reason this as juggernaut has touched on is that this shifts the peak volumetric efficiency of your engine more towards redline. Even the Greddy intake manifold with larger(diameter) and shorter runners shifts this peak VE further towards redline. However pushing this peak VE higher in the RPM range causes your peak torque to appear later and give you more peak HP.

I noticed in your post with the dyno graph you're saying power is falling off, this is not true. Your torque is falling off but since it is falling off at a slow rate you're still gaining power. Which is the ability to do work. I personally don't think you need anymore cam. The 270s will of course raise this peak HP number because it is giving you more torque up top so...for the sake of it let's say the 270 cams shift your powerband 500 RPM. You would make... 554.3 WHP which is a gain of 21 WHP. This is found by the equation below:

(Torque*RPM)/5252 = HP

I converted the kg/m by multiplying by 2.2 pounds and 3.281 feet...not 100% accurate but close enough.

Anyhow, this shift in power means you're going to lose power in the low-end too. 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.

[Master Chief]

I said power, i was refering to torque - sorry.
I just think of an engine as making torque, not HP, so when i say power, i reffered to the torque.

I belive the 270's will not only shift the power a few 100ed RPM up, bit it will also lower the decent rate of the torque line.
My aim is basicly, to have the torque drop rate, be smaller.....I.E. A streighter torque line, wich will result in more HP acrross the band.

If i wasnt going to SOLIDS, i wouldnt replace my 260's, but since i need new cams anyway, i am exploring the possibility.

Anyway, i'll try the 270/270, and if i dont like it, i'll try a 260/270, and if i still dont like it, i'll try 260/260...... by thay time, someone will have a chance to purches a hardly used set of solid cams......

[steve shadows]

I would stick with 260s if you like where your torque and power band is coming on now.

You will probably raise your top end power up slightly with the 270s but will also shift the power band over to the right slightly I have seen this with almost every cam change up from 260 or 264 to a 270 or 272 the torque band will just shift over to the right more, usually 500 rpms or so.

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

The SR motor likes to make it's peak torque and power in the mid-range and upper mid-range between 5500-6800 rpms. It is not a high rpm motor when using a factory head. The VE heads are much more oriented around high rpm power between 7000-9000 rpms with higher duration cams and larger turbos,some even capable or 10500 on street setups.

I suggest working with the motor the way the motor wants to make power and complimenting this for the best and more smooth and violent power band. Every tuner has different experiences and philosophies though.

Another thing you could do is stick to a smaller plenum with longer runners or stock Intake Manifold design as a compromise to the higher duration cams. This is something that actually works even better for having your cake and eating it too. I am a big proponent of long runner, small plenum IM on SR for a torquey and broader low end range of power

[Monooxide]

Originally Posted by steve shadows

I would stick with 260s if you like where your torque and power band is coming on now....

This is exactly what I said. I'd like to swing by your shop sometime but If I remember right, you're in Cali or something.

[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.