Tomei Poncams Installed ! Hmmm power...

[Gradenko]

On the lift side of things the HKS cams for the RB25det do go as high as 9mm of lift @ 264deg duration, at least on the exhaust side. I put one of these in the old R33 gtst.

Right you are too. Maybe the best combo for a non-vct rb30det is to mix and match - Apexi 260 8.9mm intake with HKS 264 9.0mm exhaust.

Any comments on 250 vs 260 degree duration intake cam on an engine that revs to ~7000rpm?

[rev210]

I have noticed oil temps are slightly higher with the new cams (engine temp the same). I don't have an exhaust gas temp guage but, I assume the exhaust temp would be a little hotter?

[Sydneykid]

Yeah but SK he was talking about an RB30/31DET

what are your thoughts on cams for an RB30/31DET with NO VCT?

It really depends on what head is on the RB31DET and what use the engine is being put to. If its an RB25DET non Neo, then the 256 Tomei Poncams are the go, if its a Neo then the 260's. That's in a road/combo car and I see no reason to dissable the VVT.

If its an RB26 top end on a forged 3.1 litre bottom end for circuit race use, then I like the Jun profiles with a preference for 272/10.8 mm inlet and 280/10.8mm exhaust.

If its an RB26 top end for a road/combo engine I have yet to find much difference between the brands in the 264/9.4 to 9.8 mm lift area. They seem to work pretty much the same, as long as you stick to the standard base circle. I am not a fan of the reduced base circle profiles regardless of the brand.

Hope that answered your question:cheers:

[Bullant47]

Hi rev, can you tell me how you modified the R33 CAS so that it fitted on the R34 Cam CAS. I have a problem with trying to sort something out like that now. Even bought a new R34 CAS and its not working.

Thanks Rev

Ian

[Sydneykid]

Hi rev, can you tell me how you modified the R33 CAS so that it fitted on the R34 Cam CAS. I have a problem with trying to sort something out like that now. Even bought a new R34 CAS and its not working.

Thanks Rev

Ian

Hi Ian, I don't think you can use an R34 CAS with an R32 or R33 ECU; the timing indicators are different, the R34 has many more if I remember rightly.

[The Alchemist]

Hey SK, I've installed Tomei's in my R32 GTR and found that the torque starts to drop off at 4800rpm leaving me changing gears at 5000 to 5500 rpm cause of noticible seat of the pants dyno torque loss. Its very obvious on the dyno runs too. AFR's are all good and the timing is tweaked to get the best out of it, 191 RWKW at 14psi at 6200rpm. Theres also a bit of boost creep over 6000rpm up to 16 psi due to possible restriction in the turbine side

Is it time to try retarding the cams to help bring up the mid range and top end again ? What would you suggest> -2/-2 and see what you get? or increase the lobe centers to try and broaden the torque band with a -2 inlet +2 exhuast? When doing these changes should you take out a couple of degrees timing for safety reasons when experimenting?

Other mods affecting flow incl steel wheeled GTR turboes with larger comp wheel only, HKS super drager exhaust, trust intercooler, std AFM's ( reaching 5V at 6200rpm ) std dumps

Cheers mike

[Trust33]

Hey SK, I've installed Tomei's in my R32 GTR and found that the torque starts to drop off at 4800rpm leaving me changing gears at 5000 to 5500 rpm cause of noticible seat of the pants dyno torque loss.  Its very obvious on the dyno runs too. AFR's are all good and the timing is tweaked to get the best out of it, 191 RWKW at 14psi at 6200rpm. Theres also a bit of boost creep over 6000rpm up to 16 psi due to possible restriction in the turbine side

Is it time to try retarding the cams to help bring up the mid range and top end again ? What would you suggest> -2/-2 and see what you get? or increase the lobe centers to try and broaden the torque band with a -2 inlet +2 exhuast?  When doing these changes should you take out a couple of degrees timing for safety reasons when experimenting?

Other mods affecting flow incl steel wheeled GTR turboes with larger comp wheel only, HKS super drager exhaust, trust intercooler, std AFM's ( reaching 5V at 6200rpm ) std dumps

Cheers  mike

Go a full exhaust with proper dumps unless you are thinking of upgrading turbos soon.

[The Alchemist]

well I have a set of HKS GT-SS plus dumps sitting here in a box but am waiting and saving to do a full engine rebuild first to complement the new turboes.

Its just that I hear SK and many others saying stuff like "250rwkw" on GTR's with similar mods and I'm wondering what I'm doing wrong. Tests were done on a dyno dynamics in Shootout-6 with proper testing protocols and atmo comp set up correctly. The cars makes 5000N by 3600rpm and holds this till 4800rpm where it slowly drops off to around 4300N by 6200rpm. The torque curve looks narrow to me thats all.

Mike

[Sydneykid]

Hey SK, I've installed Tomei's in my R32 GTR and found that the torque starts to drop off at 4800rpm leaving me changing gears at 5000 to 5500 rpm cause of noticible seat of the pants dyno torque loss.  Its very obvious on the dyno runs too. AFR's are all good and the timing is tweaked to get the best out of it, 191 RWKW at 14psi at 6200rpm. Theres also a bit of boost creep over 6000rpm up to 16 psi due to possible restriction in the turbine side

Is it time to try retarding the cams to help bring up the mid range and top end again ? What would you suggest> -2/-2 and see what you get? or increase the lobe centers to try and broaden the torque band with a -2 inlet +2 exhuast?  When doing these changes should you take out a couple of degrees timing for safety reasons when experimenting?

Other mods affecting flow incl steel wheeled GTR turboes with larger comp wheel only, HKS super drager exhaust, trust intercooler, std AFM's ( reaching 5V at 6200rpm ) std dumps

Cheers  mike

Hi Mike, a few suggestions follow;

* A/F ratios need to be 12 to 1, 12.5 is better for power but 12 is safer.

*Try opening up the lobe centres first, +2 Inlet and -4 exhaust and see what happens. Adjust the CAS to get the static timing back where it is now. You should be able to run more timing than you currently have, but watch the knock levels.

*The boost creeep is a sign of mismatched turbine and compressor, I am concerned with "steel wheeled GTR turboes with larger comp wheel only". The turbine upgrade needs to be slightly larger in proportion to the turbine. That will cause boost creep if it is not increased and cost some power at higher airflows (RPM).

*Did you get the wastegate increased in size as well? That will cause boost creep if it is not increased and cost some power at higher airflows (RPM).

*The standard dumps are not your friend, but I don't think they are the limiting factor at the moment. But if you have to remove the turbos to fix the turbine and/or wastegate sizing then I would be changing them.

*I assume it's cat free? I have seen a GTR that couldn't make 200 rwkw with a long list of mods, high flow cat and it made 260 rwkw. It had boost creep as well.

*The AFM's getting to 5V at less than 200 rwkw is most unusual. That indicates the air is getting in, but not out. Can you measure the boost before and after the intercooler? Say straight out of the turbos and at the plenum? That will tell you if you have a restriction there. Unlikely but worht checking.

*I would be looking at 16-17 psi of boost, if the flow job on the turbos is good they will do that nicely.

*What ECU are you using?

*Which Tomei cams did you choose?

That's probably enough to keep you busy, let me know how it goes:cheers:

[The Alchemist]

hey SK thanks for that , just been up at the work shop trying cam settings and got back to find your reply

Cams are tomei 260/260 9.2mm, cat free, wastegate has not been changed according to prior owners knowledge, AFR at 12:1 or close from 4000rpm onwards, PFC with datalogit laptop software primo setup

here's how it went: see attachment

I had read prior to this, other posts suggesting +2 inl and -4 exhuast. I did the exh first but went +4 just to see what happened and promptly lost 35 kw off the top end and got 2nd degree burns for my efforts of the radiator

mmm not good. I then went -4 on the exhaust only and the car immediatley livened up and the torque came in earlier. I then added +2 on the inlet and with a few minor timing changes up the top end acheived this result : see attachment.

I called it a day after that but may add some more on the inlet side tomorrow.

what do you think?

[The Alchemist]

oh , and the boost creep held flatter before creeping up, delayed I guess you could say, this helped my the top end look more respectable.

Could the dyno possibly be set up wrong or in need of recalibration? Given the AFM voltage perhaps the car is making that power and the dyno is out of whack?

I also have a set of HKS dumps sitting at home here with my GT-SS kit, perhaps its worth the experiment to put those in and mill out the wastegate holes while the turboes are off.

The GT-SS kit won't be going on until I rebuild the engine you see.

Mike

[Dash]

You wouldn't happen to know what a std or near std gtr makes on that dyno would you?

or even better a graph to compare yours to.

Then you'll know if its the dyno or your car

[The Alchemist]

well GTR's are pretty scarce around here I do know one one other...wonder if it worth dynoing his car just for the experiment.

[Gilly]

Can someone clear this up for me. the highest lift (hydrolic)for the RB25 is 8.9 advertised and 8.9 actual which is how much the valve itself moves with full oil pressure. then wouldnt this be equivelent to a 9.3 advertised on a GTR with 0.4 valve clearance. On a GTR with say..9.3 advertised lift then the valve will only move 8.9 as the valve wont move until it takes up the clearance between the lifter and the cam. When you read the Tomei cam spec for GTR the actual is always 0.4 lower than advertised and GTST advertised and actual are the same. The valve clearances for GTR inlet are .45 cold or .51 warm so am I also correct in saying the GTR will have even less lift when hot.

This is my understanding please let me know if I am wrong.

[Freebaggin]

Can someone clear this up for me. the highest lift (hydrolic)for the RB25 is 8.9 advertised and 8.9 actual which is how much the valve itself moves with full oil pressure. then wouldnt this be equivelent to a 9.3 advertised on a GTR with 0.4 valve clearance. On a GTR with say..9.3 advertised lift then the valve will only move 8.9 as the valve wont move until it takes up the clearance between the lifter and the cam. When you read the Tomei cam spec for GTR the actual is always 0.4 lower than advertised and GTST advertised and actual are the same. The valve clearances for GTR inlet are .45 cold or .51 warm so am I also correct in saying the GTR will have even less lift when hot.

 

This is my understanding please let me know if I am wrong.

I reckon you are on the money, RB25DET early models cam lift = valve lift but not so for later models and all RB26DETTs due to valve clearance of 0.45-0.51mm (quite a bit really).

[Sydneykid]

Hi Mike, am I right in assuming the dyno runs in 3rd gear? Pretty good result from the cam timimg, 25 rwkw at ~3,000 rpm and 20 rwkw max power. That's as good a result as I have seen.

But, the max is still very low. There is some restriction in there stopping it from making the extra 50 rwkw. Without any better evidence, I'd be looking at the turbos. If the tubines truly are steel wheel but standard size, then that's a problem in making power. If the wastegates are truly standard, then that's a problem in controlling boost and making power.

Some other suggestions;

1. What sort of knock levels are you seeing on the log? I try for less than 40, but I never get zero, ~25 seems average. If you are not seeing the occassional 40, then it could do with some more ignition timing.

2. What do the plugs look like? Mostly interested in the comparison accross the 6.

3. Have you done a leak down test?

4. What fuel?

That's enough for now, this one has got my interest:cheers:

PS: for a power comparison, we have a GTR with N1 spec turbos, great dumps and exhaust, adj cam timing (std cams), Power FC and it makes 275 rwkw at 1.2 bar.

[The Alchemist]

knock levels never go above 20, 96 octane petrol, runs all done in 4th gear not third.....

why third gear ??? I always thought 4th was 1:1 and thats what you used on the dyno???

Haven't done a leak down test ....

plugs all look good across the six except the 2 closest to the PCV valve which are a bit sooty thats all. I haven't got around to installing a catch can yet.....its on my list

thanks again SK.

Mike

[The Alchemist]

went back out to work today and had another go, engine did not like another 2 Deg inlet adv at all> made no axtra power or torque so I set it back to 2 Deg.

tweaked upper end timing, got 207 rwkw now. Also tried a bit more timing in the midrange but achieved no noticable increases so they went back to where they were as well.

Drove the car home tonight and sweet mary! that 10 to 12 % more torque felt like a freight train!!!!!! You'd have thought the car gained another 20 or 40 % if you hadn't have seen it on the Dyno screen !!!!!

I'm very pleased with the results and would highly recommend Cam wheels to anyone

Still very interested SK to hear you comments from my last post, esp the 4th gear vs 3rd gear thing.

regards Mike

[Sydneykid]

Hi Mike, dyno runs in 4th Gear are usual, as you said 1.1. Sometimes people use 3rd because they still have the 180 kph speed limiter, Power FC so you don't have that problem. I just guessed 3rd because of where the dyno graph cut off, I calculated the RPM using 3rd gear ratio.

Since it is in 4th gear, it makes my previous posted rpm (guess) a bit high and just confirms my thoughts on restrictions. GTR's with your mods rev out way better than that, make good power to 7,250 rpm and don't drop off so much. There is something restricting the airflow, I am guessing the turbine/wastegate problem.

Re; the wastegate, you actually have to repace the flap with a larger one as well as port it. The ones we get done have a flap that almost touches the sides of the chamber, they must be 4-5mm bigger in diameter. The flaps themselves are pretty cheap, just drill the rivet out, remove the standard flap and replace it with the larger one and a new rivet. The porting takes longer.

Sorry have to go, I have a set of Bilsteins on the shock dyno:cheers:

[BlueRB240]

Not to go too far off subject, I ordered the 270 Tomei cams intake n exhaust. Didn't get the cam gears yet or the valve springs. Do I need the valve springs if I keep the rev limit at stock? (RB20 btw)