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Rb25/30Det

R32Abuser

By R32Abuser,
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Dale FZ1 Veteran

Dale FZ1

Posted
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Search on topics by Cubes regarding cams. He played with factory grinds for a while and shared the results. I've not heard much/any negative reporting on the 25DE cams regarding a tendency to promote/induce knock simply because of their spec.

Reduced overlap effectively increases trapping capacity of the inlet charge within the cylinder. That will improve general fuel consumption, but also reduces scavenging of the cylinder. ie. less of the residual exhaust gases will be pushed out with the assistance of the incoming boost charge. Therefore reduced overlap can ultimately have a negative approach towards torque production at high boost + rpm. But it's not a direct comparison with only valve overlap changed, since those factory cams are very different even if they are very mild specification. The 25DE cams were designed for use in a naturally aspirated application, so I wouldn't be at all surprised that the 20DET spec is better suited when phased as per factory setup.

Are you running adjustable cam gears? That's the optimal approach to changing your cam timing/phasing and alter overlap. Gears are readily available and not super expensive. By changing your phasing this way, you may well get the best of both worlds. The 25DE exhaust cam has slightly less lift, but the lobe holds the valve open marginally longer (yes?) so there might be a benefit there if you trial it with adjustable gears.

Depending on engine spec, the sputtering idle can result from a lean condition. Ignition will also have a significant contribution here. Spark events that are too late (retarded) in the compression stroke simply results in a poor running engine, doughy response, and elevated EGT. That includes cruise (low load) conditions. I had interpreted the use of new CAS and smoother running as probably giving an improved/accurate timing signal for sparking, which is not unknown considering the gear we are using has got some age on it by now.

Either way, you've got some changes being made which will hopefully solve the problem. I'm interested to see the outcomes.

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R32Abuser Mentor

R32Abuser

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Dale, cheers for the response.

I've spoken to Cubes directly and he mentioned that the 25DE cams did make the motor more prone to pinging when placed in comparison to his set of R32 GTR RB26 regrind cams. But by no means did he experience this phenomena to the extent which I have. This makes me think its not a single issue, but part of a bigger collection of problems. What exactly, I dont know though?! rant.gif

What you said makes sense in my head, but either way I guess the end result is what is important. Hopefully something positive results from next week's dyno worship.gif

With regards to adjustable cam gears, no, I do not have a set on the motor. I have been looking into getting a set recently, but never made it in time before the builder put the new camshaft set-up back together. Guess if we take the head off, it will be the time to chuck a set at the car.

Cubes Grand Master

Cubes

Posted
Posted

I've spoken to Cubes directly and he mentioned that the 25DE cams did make the motor more prone to pinging when placed in comparison to his set of R32 GTR RB26 regrind cams. But by no means did he experience this phenomena to the extent which I have. This makes me think its not a single issue, but part of a bigger collection of problems. What exactly, I dont know though?! rant.gif

What you said makes sense in my head, but either way I guess the end result is what is important. Hopefully something positive results from next week's dyno worship.gif

Thats correct.

Mine hit a bit of a wall with the stock rb25de cams and gt30 at around 270rwkw. Dropped the cams in and on pump fuel she sucked up the timing to make ~300rwkw on the same boost.

After the cams from memory peak torque was running around 18 degree's with near peak power up around 21degree's.

R32Abuser Mentor

R32Abuser

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Ok....long time since an update!

Sooooo good news and bad news

Good news is the detonation issue has been fixed. The appropriate amount of timing can be wound into the motor with little to no detonation what so ever (~20-22 deg). The only items we changed were the CAS, camshafts, and re-timed the motor. So one of these items fixed the issue. Which one...I'm guessing CAS & Re-timing the motor would have fixed the issue. Plenty of guys running standard camshafts with no issues with pinging.

Bad news is now it wont make the power this setup should.

Running 17PSI, 20-22 degrees worth of timing and the setup listed in the original post, it won't make over 210-220 RWKW.

This setup (almost identical to Cubes) made 250-260RWKW so my result is well short of what I was expecting.

For a kickoff, the cooler piping has been complete checked etc. for a rogue oily rag or debris etc. Next move will be to drop the exhaust and removed the airbox to see if there is a restriction on either the intake or exhaust end. I HIGHLY doubt there being a restriction on either of these items as plenty of others have run these with no issues at these power levels.

Anyone else got any experience/ideas?

God this car is driving me crazy!

R32Abuser Mentor

R32Abuser

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Are you a drag racer?

Forget what the dyno says and take it for a strap down the black top.Dyno's are a tuning tool and should not be used to compare setups. There are to many variables that can sway dyno figures

Nope. Here in Adelaide we do not have a drag strip even if I wanted to take my car down the 1/4 Mile.

60kw is too big a variance for a dyno.

10-20kW, even 30kW maybe at a BIG stretch...but not 60kW. From what I've been told, its definitely down on power compared to what it should be by the "Seat of the pants" dyno.

Edited by R32Abuser
ido09s Mentor

ido09s

Posted
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I lost about 40rwkw going from BP 98 to E85.... i gained a very easy 10mph down the black top so dyno's are nothing but tuning tools.

Isnt this also a fresh engine? Get it run in and then see how it goes

If your worried about the final figure get the car your comparing it to and go for a lesiurely cruise with him to compare performance :D

Edited by ido09s
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Running 17PSI, 20-22 degrees worth of timing and the setup listed in the original post, it won't make over 210-220 RWKW.

This setup (almost identical to Cubes) made 250-260RWKW so my result is well short of what I was expecting.

For a kickoff, the cooler piping has been complete checked etc. for a rogue oily rag or debris etc. Next move will be to drop the exhaust and removed the airbox to see if there is a restriction on either the intake or exhaust end. I HIGHLY doubt there being a restriction on either of these items as plenty of others have run these with no issues at these power levels.

Anyone else got any experience/ideas?

God this car is driving me crazy!

My RB30/25 has just been fired up and makes 225awkw on a hub dyno at 9 psi. A few things to tidy up and will go back to the tuner to up boost to 18psi and hopefuly exceed 300awkw. (Stock head with VCT Gt3540 with Sinco high rise manifold (like 6boost) ffp with stock throttle body stock fpr Link ecu).Dropping the exhaust may be interesting - have you got a functioning or possibly collapsed cat converter?

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Brand new cat converter. 300 cell rings a bell. Been used before by others to make more power than I have shot for.

True but in combination with other mufflers/resonators etc may still contribute to exhaust restriction. I have a Venom 100 cell metal cat (because I plan to leave it in permanently - some take their cat out once they have their wof/ low volume certificate etc).

R32Abuser Mentor

R32Abuser

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Posted (edited)

True but in combination with other mufflers/resonators etc may still contribute to exhaust restriction. I have a Venom 100 cell metal cat (because I plan to leave it in permanently - some take their cat out once they have their wof/ low volume certificate etc).

I have no mufflers besides the cannon at the rear of the car.

Its a full 3" from the turbo back (custom dump/front pipe) to the 200/300 cell cat. then its straight back to the cannon besides an Apexi ECV (exhaust valve for noise). This item has been checked and assured that the "butterfly" valve is in the full open position.

I still reckon its a restriction on the intake side somewhere. Just a hunch tho...

Edited by R32Abuser
ido09s Mentor

ido09s

Posted
Posted

I call bullshit on the valve in the exhaust and i wouldnt believe them till its removed.

We had this issue on a VL once and it took us ages to find it. Didnt find it till we dropped the ehaust off and suddenly it made power. We ended up finding out that it was installed backwards and was blowing closed.

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