Camshafts For 700hp Rb26/30

[Swiper the Fox]

Hi guys, I've been reading this thread with interest and a lot of questions asked are ones I had myself!

I am also building an RB26/30. I have ordered HKS cams of 264 degree and 10mm lift, so only a smidge bigger than Poncams.

I am thinking of going 707160-5 turbos (same as HKS2530).

I know this will limit my top end to about 600-650 flywheel hp. I don't mind so much as I am sure it will be torquey as in the mid range.

Is there likely any problem with this setup in terms of the internal wastegate for example (will it be able to expel the air from the RB30 to keep boost under control)

I know I could go GT-RS for more power - but I figure 2530's will spool ultra fast on a 3 Litre and this appeals to me.

264/10mm cams will work a treat.

NO turbos are the "same" as HKS2530's

HKS recommend GT-RS turbo's on their 2.8ltr kits for street/circuit and would be a better match for the 3ltr.

Disclaimer: This is only my opinion and may possibly be total bullsh1t.

[Sydneykid]

Hi guys, I've been reading this thread with interest and a lot of questions asked are ones I had myself!

I am also building an RB26/30. I have ordered HKS cams of 264 degree and 10mm lift, so only a smidge bigger than Poncams.

I am thinking of going 707160-5 turbos (same as HKS2530).

I know this will limit my top end to about 600-650 flywheel hp. I don't mind so much as I am sure it will be torquey as in the mid range.

Is there likely any problem with this setup in terms of the internal wastegate for example (will it be able to expel the air from the RB30 to keep boost under control)

I know I could go GT-RS for more power - but I figure 2530's will spool ultra fast on a 3 Litre and this appeals to me.

Here's your problem, with 2530 's on a 3 litre you will hit boost at freeway running speed in 5th gear. That means just a gentle roll onto the throttle at 100 kph will generate plenty of boost. This absolutely kills the fuel economy and actually makes the car hard to drive smoothly. You just want to hold the speed up a slight hill or accelerate gently and bingo it's boost time and away you go. I found it hardly ever ran closed loop and guzzled gas like crazy.

Much better to pick a turbo/turbos sizing that doesn't boost up until 3,000 rpm or so, that works much better for the 100/100 kph speed limits.

Don't confuse response with boost build, you can still get good throttle response from a 3 litre with turbos that don't make boost until after 3,000 rpm. It's all in how you tune it.

cheers

[N I B]

If your ECU can map boost to TPS you can still use the 2530s.

Ive have an RB30 powered GTR in at the moment and love the match.

[R32 TT]

If your ECU can map boost to TPS you can still use the 2530s.

Ive have an RB30 powered GTR in at the moment and love the match.

Yep - I have an ECU capable of that.

But I don't get why you say that would make a difference?

If I understand SK correctly, the turbos being small for the 3litre means that the exhaust wheel gets wound up 'early' even when on light throttle.. this being 'physically' how much air is moved - I don't see how the ECU would be able to stop it happening.. How would I fix using TPS?

Mate! I'll have to come and see you to see what this GTR is like. Is it in your workshop at the moment?

It would be good to know just how this combo goes.. I do like the 'boost anywhere' idea... but don't want to regret doing it either...

[WetGTR]

Hi Shane, the higher lift means the cams have steeper profiles needed to fit the lift (open and close) within the duration (time). This means the valves open and close faster. In addition you have to use higher rate valve springs to make sure that the valves close (follow) the cam lobe’s profile.

So you have faster and harder closing valves. Just like a rapid and heavy hitting hammer, this will eventually wear out the valve seats, pound them flat. In addition you will experience similar wear on the valves themselves. The quickest wear being the seat area where the valve seals on the seat. As this wears, the seat becomes wider and may even leak. Both of these costing noticeable horsepower.

The rapid pounding of the valve heads will eventually fatigue the valve stems around the head mushroom. Given sufficient repetition, the valve head will eventually fall off causing (at the very least) catastrophic damage to the piston and cylinder head.

Also you have faster opening valves with stronger valve springs resisting this opening. This means the cam lobes themselves and the buckets wear out faster. Higher lift also increases the angles on which the lobes affect the buckets. This side loading results in faster wear of the valve stem seals, which will leak oil into the combustion process and cause a loss of power and generally premature detonation.

This rapid wear factor why you don’t see huge horsepower GTR’s making 100’s of ¼ mile passes in a year. This is why you have drag engines that do little real kilometres, able to be built/tuned to make more power than circuit racing engines that have to last a season. An extreme example is a F1 engine, that is very lucky to do 1,000 k’s before a full rebuild is required. Or a top fuel drag engine that does one pass before a full rebuild is required.

So to answer your questions;

1. RB26 valves are already stainless

2. Stronger valve springs actually increase wear, not decrease it. I use valve springs just strong enough to control the valve, make it follow the lobe and resist the targeted boost pressure.

3. Personally in a circuit race engine, I never use cams over 10.3 mm lift to minimise the side loading and the valve seat wear

Hopefully that answered your questions

cheers

If your valve train is a wearing factor, what would be the best way to check and test to make sure everything is in good order. I don't think many people at all look at the valve train as something they have to service. What would the best way of testing the valve train to see if its in good health?

How often should the service intervals be?

I understand there is a leak down test you can do, if so, what should it be displaying?

Edited April 22, 2006 by WetGTR

[rob82]

Yep - I have an ECU capable of that.

But I don't get why you say that would make a difference?

If I understand SK correctly, the turbos being small for the 3litre means that the exhaust wheel gets wound up 'early' even when on light throttle.. this being 'physically' how much air is moved - I don't see how the ECU would be able to stop it happening.. How would I fix using TPS?

If you ECU is capable of TPS based boost control then you can reduce boost at low TPS values by lowering the boost control solenoid duty cycle. I find this a problem with most aftermarket boost controllers as there is no TPS based percentage of boost so as soon as the car can make full boost it will whether your foot is at 30% throttle or 100%. It makes cars very untracatable and hard to drive off the line as even if you take you foot off the throttle you still have the same amount of boost.

I'm sure sydneykid would like to explain to us how he keeps his cars tractable mid corner as the cars transition into full boost? Might be a team secret too..

[R32 TT]

If you ECU is capable of TPS based boost control then you can reduce boost at low TPS values by lowering the boost control solenoid duty cycle. I find this a problem with most aftermarket boost controllers as there is no TPS based percentage of boost so as soon as the car can make full boost it will whether your foot is at 30% throttle or 100%. It makes cars very untracatable and hard to drive off the line as even if you take you foot off the throttle you still have the same amount of boost.

er.. but the boost control solenoid can only "add" boost, not reduce it?

The actuator on the Turbo is factory set to about 8 pounds. So nothing is going to stop the turbos from making at least 8 pounds of boost when the engine shoves enough exhaust gas through the turbine...

? Or have I just missed the point somewhere ? (wouldn't be the first time )

oops! Sorry to ShaneF - we seem to have deviated from the subject of this thread huh...

[rob82]

er.. but the boost control solenoid can only "add" boost, not reduce it?

The actuator on the Turbo is factory set to about 8 pounds. So nothing is going to stop the turbos from making at least 8 pounds of boost when the engine shoves enough exhaust gas through the turbine...

? Or have I just missed the point somewhere ? (wouldn't be the first time )

oops! Sorry to ShaneF - we seem to have deviated from the subject of this thread huh...

I swear theres about three differnet topic in this one thread!!!

Thats correct if there is enough gas flow to spool the turbo to the wastegate pressure then it will go there no matter what, but you can control what happens after that with regards to boost level and spool rate 8 pounds onwards which is usually the case as I dont know too many people with tractablility issues at 8 pound.

[shanef]

Its cool guys, its all very relevant and will need to be discussed sooner or later and why not all in the one thread?

Ok i got a quote back for headwork and block work.

$500 MAX to recondition the head and to assemble it all, i.e. install camshafts, cams, valves, guides, springs etc.

Also $20 per cylinder to bore & hone to 40 thou. Now the place i got this quote from said they can only bore to 38 thou n then they hone the other 2 thou.

Does this all seem about right?

cheers

Shane

[Dash]

Sound very cheap.

Have they done a rb26 head before?

[discopotato03]

Gary do you think its fair to say that in higher gears at highway speeds small differences in throttle openings make for significant changes in manifold pressure and volumetric efficiency so the turbos want to take off ?

Back to the cam situation I thought that the buckets were taking all the side loads so guide and seal wear would have been much lower than say a rocker type valve train . I can understand the more agressive lift rates and spring rates giving the seat and face a hard time though an RB30 may not have to rev as far so possibly get away with less spring rate before valve crash or bounce sets in .

I was reading a while back about cam profiles and opening plus closing ramps for high lift shortish duration cams . I don't suppose anyone has had the Tomei and HKS cams on the Cam Doctor to see how well they were speced ? 260 10mm sounds nice - std base circle ?

Don't want to restart the big'n vs two litlun's debate but I did see somewhere (can't find it now) that the twins favour short stroke motors and singles the longer stroke ones .

Cheers A .

[discopotato03]

Forgot to add , where would be the trade off between big cams and larger valves ?

Dread to think of the cost of cams and valves and springs and guides and shimming .

[R32 TT]

Forgot to add , where would be the trade off between big cams and larger valves ?

Dread to think of the cost of cams and valves and springs and guides and shimming .

Yes well this is what I went through in trying to determine the 'best' cams for my application.

SK recommended to me that for my application I should try to get cam's duration of about 260-264 degrees. That the duration of the cam more or less dictated the useable rev range. I want mine for varied use from street to hill-climbs, motorkhana and circuit. (less so for drags) So 260-264 seems about right.

Then I was going to go "as higher lift" as I could in that duration - and so I found that Tomei did 260degree cams with 10.8mm lift. (there are bigger lift cams, but you also need more duration to be able to get them)

However! Its seems that to do this, Tomei make them to a smaller base circle and you require to get specific buckets (followers, lifters - whatever you call them) as well. Basically going over 10.3mm lift seems to increase the complications somewhat and require these extras.

see here:

http://www.tomei-p.co.jp/_2003web-catalogu...ifter_rset.html

So instead I opted for the HKS cams that have standard base circle, 264 degree duration and 10.0mm lift.

This is all going on an Rb26/RB30 combo - and now I just need to make my mind up about the turbos to suit.

DiscoPotato03 - have you seen/heard of the Garrett 707160-10? Looks like same specs as HKS GT-RS (although HKS may have some advantages?) Far cheaper than the HKS though - and might be just the right choice for an RB30?

[shanef]

Sound very cheap.

Have they done a rb26 head before?

Yeah got a mate who i went to school with that works at Engine Engineering

He said they do rb's now and again. They also do the work for the jack daniels drag car.

[discopotato03]

R32TT I'm not a big fan of the GT2871R series of which HKS's GT-RS is the 52 compressor trim version , with their housings . I know Garrett is now selling a GT2871R 52T which is supposed to be identical to HKS's SR20DET specific GT-RS .

I can't help thinking the 71mm compressors are a little big for the 54mm GT turbine except maybe the 48 trim wheel .

The one that is interesting is HKS's GT2535 and if you can believe the specs at HKS USA it is supposed to use a 69 ? mm compressor so probably about as far as the GT28 turbine could efficiently go .

The real problem with the GT28BB turbos in twin form for the RB26 is the lack of a turbine housing in a slightly larger AR than .64 but not as big as .86 . Something around a .70 - .72 would be better but then again this is with 2960cc's not 2570 . Those turbines really come alive as their map shows with the .86 housings but probably a bit much by two for 3 litres .

I still tend to think the big single have so many advantages over twins and its a pitty some GTR/RB26 owners feel that using a single is like living with only one ball - even a big one . Warm cams should make for sharper induction and exhaust pulses so spooling larger turbos should not be too much of a problem . The multi throttle inlet system is there to breathe and resist reversion .

Cheers A .

[Tommyk]

Hey guys, interesting thread.

First of all, I think the reason why a lot of gtr owners stay low mount twins is the whole defects side of things.

Discopotato03 - Do you honestly think that GT-RS turbos are too big for the rb30/26 ?

I know the garrett 2530 also comes with a 0.86 housing option, but how would this affect ultimate power and output ?

I will be doing a complete head recondition/build with aftermarket parts and will probably only be doing tomei retainers, valve springs and guides. Parts cost should be just under $1000 plus labour. Im also considering 260 @ 10.25mm cams, but also tempted to look into the 10.8mm lift cams, but im not sure whether the lift will be too high for a 2.8 stroked rb26 with highish comp ~ 8.8:1 running 2530 garretts @ 1.6 bar

[discopotato03]

I don't think its so much a case of GT-RS's being too big for an RB26/30 but more to do with the compressors being a little big for the turbines in their case . You really can't separate compressor and turbine performance because they're physically joined at the turbine shaft .

From a legality point of view I was told a while back its not strictly legal to use non genuine windscreen wiper blades so where does it begin and end ?

The subject of high or low mount and single or twins gets bandied round often and how the user goes about it and the attitude/image they project spells how much attention their car attracts .

I want an RB26/31 that looks like an RB20 though it won't fool anyone whos in the know . If I was using an RB26 or GTR it would still use a single preferably low mounted and off a cast manifold because its far easier to work with/on .

Anyhow my preferences aside you get into a grey area with twins because of the gap between the GT28 and GT30 turbine families and turbine housings/AR's . Toyota were among the few in Japan to produce a 3L twin cam turbo motor and at the time I don't suppose Garrett/HKS were breaking their necks to make an in between size to cater for it . Most of the 2JZGTE Supra people end up with GT30R/GT35R/GT40R/GT42R single turbos and in that range you can have mild to very wild performance with many options for trims and housing AR's plus some very interesting hybrids and HKS options .

Your call .

[Tommyk]

Fair enough, i understand your point. I would definitely go a big single if it were possible .... Sydney really sucks for those sorts of things.

I do have one more question remaining. I understand that higher lift cams put greater stress on the valvetrain, as suggested by Gary. Would it, however, be worth going 260 degree 10.8mm lift cams over the 10.25mm tomei cams ?

Im willing to upgrade pretty much the complete valvetrain to compensate, if necessary. Suggestions ?

[discopotato03]

I think 10mm of lift will do me and the 260 odd duration should make up the difference (for road) with the larger cylinders . It sounds like RB26 heads need a fair bit of exhaust port work and this would be more important with 500cc pots venting through them .

Has anyone go a link to HKS RB26 cams in english as I can't find one . I'd like to know if the pair are sold with differences in lift or duration (~260 degree set that is) . Would these be step 2 cams ?

Cheers A .

[Tommyk]

http://www.takakaira.co.jp/performance/hks...sp?index=engine

Have a scroll through. The step 2's have 10 or more mm of lift