Rb26 Cam Choice

[druzilla32]

oh crap, lol

oh well

[SLY33]

Slightly off topic and I aplogise, but the Tomei URL that Pete quoted is interesting.

The specs on the ARMS B9046 GTR kit are interesting - the turbine and compressor wheels sizes are huge compared to other "bolt on" kits! 

Is this the highest power bolt on kit available?

<{POST_SNAPBACK}>

well interestingly the compressor wheel/trim measures EXACTLY the same as a HKS2540. The ARMS has a bigger exhaust wheel tho.

the kit is rated to 700ps, which is the same rating as the GTRS's your running, which i think is also the same rating as the trust T618's. So 700ps seems to be as much as any of these companies claim for their largest low mounts.

but here i get confused:

HKS GT-RS - 400 PS Output

COMPRESSOR:

Wheel = 51.2 Inducer / 71.1 Major

Trim = 52

A/R = 0.60 - Housing- 60 Inlet / 50 Outlet

HKS GT2540 - 350 PS Output

COMPRESSOR:

-Wheel- - 51.7 Inducer / 76.2 Major

Trim = 46

A/R = 0.60 - Housing- 60 Inlet / 50 Outlet

the 2540 compressor wheel- is it not LARGER than the GTRS wheel? yet how can the GTRS make 50ps more? Exhaust dimensions on both are identical. Yes the trim is larger on the GTRS, but SK explained to me that trim measurements arent really that meaningful..

The other thing that i dont get :lol: : how come two 400ps turbos in a kit is only good for 700ps? whereas on singles a 700ps turbo makes 700ps??

cheers

[pnblight]

Only my opinion but the HKS camshafts look alot higher quality and nicer finish compared (yes i have seen both)  to the tomei cams i saw and the 3 cars with HKS cams that i know of average over 600rwhp so yeh my preference is HKS cams but only my opinion. Mine havn't even been dialled in yet at 608rwhp.

<{POST_SNAPBACK}>

Interesting even after you have seen a HKS cam snap in half in one of those 3 cars? I have seen cam studs broke before but the tomei's i have never heard of or seen fail. Just an observation.

[discopotato03]

SLY33 the 46 trim 76.2mm compressor is a TO4E in the HKS GT2540 . I have seen an RB26 specific 2540 in bits and can well understandy why .

1) TO4E wheel older aero tech than BCI-18 series used in the GT-RS (GT2871 52T)

2) 76.2mm wheel way too big for a GT25 compressor cover .

3) Big diametre small trim wheels have more innertia than next size down ie

52T 71mm better than 46T 76.2mm .

Any TO4E size wheel overwhelms a 53.8mm GT turbine . Not enough turbine energy to drive them and not enough exhaust flow ability even if it could .

HKS's GT2540 has been with us for ages and was really a stop gap between the 2530 and 2835 series . It was spec'd early in the days of GT turbines when there was not the full range of GT (BCI-18) compressor wheels available to hang off them . This is why we also get ratshit TO4S compressors on GT turbines , neither these or TO4E wheels are high speed wheels and don't compliment the high speed turbine .

Cheers A .

Edited November 30, 2005 by discopotato03

[SLY33]

thanks for that, good explanation!

back on the topic of cams, would something like the tomei 280 11.5mm lift be a stupid choice for a street car? would it just make the low to midrange zone flat? would using a 2.8 bottom end make this cam passable on the street?

i think ive asked this q'n before, and i cant remember if it was answered, but are there any rules of thumbs when choosing duration and choosing lift? such as 1mm increase in lift gives x amount of peak power increase?

[pnblight]

i think 280deg would be way to much for street personally as i showed tomei dont recomend anything over 260deg for street, there are a number of cars run 270 or 270/260 combinations on street but it really comes down to personal choice and your opinion of what you would tolerate on the street.

From what i have seen you seem to want a package for out right hp more so than responce etc so with that preference high lift 270 should suit you the best.

pete

[SLY33]

hehe, its getting more and more like that. i just want it to go nuts when the turbos hit, and get them hitting as hard as possible

[R32-GTS]

Interesting even after you have seen a HKS cam snap in half in one of those 3 cars? I have seen cam studs broke before but the tomei's i have never heard of or seen fail. Just an observation.

<{POST_SNAPBACK}>

Yes one HKS cam i have seen snap although was through no fault of the cam but a bolt strectching causing it to flex and snap. I have on the other hand seen a Tomei Pon-cam with a 4 thou bend in it that was brand new and needed to be machined back to spec not to mention the casting dags on it that if coming off would make a nice mess of the engine.

[pnblight]

hehe, its getting more and more like that. i just want it to go nuts when the turbos hit, and get them hitting as hard as possible

<{POST_SNAPBACK}>

well then your on the right path 2.8litre with HKS GTRS twins and high lift 270deg cams will make a nasty RB26, you and Gav will have some serious fun with those combos, me i lean more toward bottom end and linear power delivery for a fast car corner to corner, but thats one of the true beautys of the GTR you can tune it just about what ever you want.

pete

[pnblight]

Yes one HKS cam i have seen snap although was through no fault of the cam but a bolt strectching causing it to flex and snap. I have on the other hand seen a Tomei Pon-cam with a 4 thou bend in it that was brand new and  needed to be machined back to spec not to mention the casting dags on it that if coming off would make a nice mess of the engine.

<{POST_SNAPBACK}>

well thats very different to the five sets i have installed and the seven set in total i have handel, to be honest i was and engine machinist for good part of my life and have worked with alot of different brands and the tomei equipment i have seen has been of the high standard. From the sounds of it, it sound more like you recieved some dodgy produces. And dont get me wrong i'm also a big fan of the hks products. But i would be carefull bagging a product like Tomei Poncams that so many people have used around Australia to such great results ie TWO-6L what made 440awkw and 10.38sec 1/4 with a set of bolt in cams.

pete

[R32-GTS]

Maybe it was a faulty set ? Im not bagign just stating what i have seen . I think its more a case of people using them because they are cheap and easy to install.. ie no head machining or upgraded valve springs rather then them been the best camshaft selection. The fastest GTR's in japan use either HKS or APEXI cams of around 280 degree duration and 11.5 + of lift but yes these are drag cars.

[pnblight]

so the JUN 8.2sec gtr700 /tomei 8.5 sec r34/ KW 8.8sec os giken GTR dont qualify as some of the best. I think your very one eyed when it comes to product brands and a little foolish righting off such successfull cars like this.

And i dont think the majority are chasing drag car cam combos, as large % of us want a combo fast/ friendly and low maintains for our street runner as the higher lifter you run the more dollars it cost to install and the more maintain it will take to run it.

[ned]

Hi there,

The poncam combination is something I am interested in for a daily driven GTR with standard turbos, PFC, and boost kit. I am after response rather than all out top end, but am getting conflicting advice on whether with that combo I would need to upspec the injectors.

Do I need 555cc or larger injectors for the poncam 260 intake, 256 exhaust 9.15mm lift combo?

Cheers

Ned

[pnblight]

Hi there,

The poncam combination is something I am interested in for a daily driven GTR with standard turbos, PFC, and boost kit. I am after response rather than all out top end, but am getting conflicting advice on whether with that combo I would need to upspec the injectors.

Do I need 555cc or larger injectors for the poncam 260 intake, 256 exhaust 9.15mm lift combo?

Cheers

Ned

ok injectors you want 700cc sard dont bother with anything smaller the pfc run them perfectly and same cost as 550cc with good headroom.

I wouldnt run poncams on std turbo mainly because your better off buying new turbos long before any cams much better investment and run the 260 inlet and 260 exhaust poncams if you buy any.

Your std injectors will make up to ~high 300s rwhp so it depends on what rwhp your aiming at. If your sticking with std turbos you will not need injectors.

pete

[[WLDCRD]]

pete, your vast knowledge of things is incredible! you are like a machine!

[Tommyk]

I thought I might pop in here and ask a question also.

I understand that tomei recommends 260 degree cams for all of their street bolt in turbos, and 10.25 lift for their 2530 sized combo - the 7660. What difference does the lift really make. I understand that it lets more air in/out without changing the cam overlap, but what does that mean in terms of driving. Lumpier idle, moved power band ? etc?

[OFENSV]

can the JUN 264 9.7 cams be used with standard valve springs? as they are the smallest jun cam nengun list for an rb26

[noone]

I wouldnt run poncams on std turbo mainly because your better off buying new turbos long before any cams much better investment and run the 260 inlet and 260 exhaust poncams if you buy any.

pete

Got highflowed stockee turbos and was considering dropping in cams and cam gears, or just cam gears on the stock cams would it be a waste of time. Just a stop gap move really as plan for a rebuild at the end of the year with new turbo's etc. etc.

Would poncams make it more or less responsive on such a setup if dialled in right?

[rev210]

poncams work on stock GTR turbos very well for the record (260 9mm lift)

[noone]

poncams work on stock GTR turbos very well for the record (260 9mm lift)

Thanx thats what I had thought from what I have been reading on here, will they be a bit laggier or much if a muchness if tuned right (assuming you may have done this at some time so might know), a bit new to TURBO cars so not so sure I suspect tuned right they may even help eliminate some lag due to better/more flow cylinder filling etc. Is that a possibility or have I missed the mark completely