Rb25/30Det

[R32Abuser]

Negative

[Rolls]

Has the builder ever built rb30s before?

[R32Abuser]

Plenty of 26/25/20. First forklift motor though. The machinist has built countless RB30's before.

[Rolls]

Well that's good. What has he said about squish ?

[R32Abuser]

Doesnt work weekends...

[ido09s]

Sounds like he should be workign weekends as he may need to strip an engine down.....

[Rolls]

Yeah if the issue is a combination of too high comp, incorrect squish etc as an engine builder he should be checking these things and not expecting the customer to have checked everything 100% before, should at least give a discount on any work that has to be done as it is as much his fault as anyone elses. Assuming that is the issue though.

I still personally think it is something completely different, eg exhaust restriction, intercooler full of oil, massive blow by or something along those lines.

[R32Abuser]

Since we are going to chuck RB20DET turbo cams in, I am going to see if i can get him to take the head off aswell whilst most of it is off.

Once that is done, majority of the stuff listed previously can be checked. Also the condition of the pistons after the detonation can also be checked.

[Bl4cK32]

Id be tracking down the issue first before throwing other items into the mix. Your running the same cams as I am and cubes did to start, which worked fine.

Not sure if we mentioned it, but Cubes looked around and picked our engine builder at the time we did ours. The builder was also the machinist, who was used to do v8s. No special knowledge of RB motors, only going off the information Cubes gave him. Its an almost proven setup, you just need to find that gremlin.

If you get stuck finding cams, ive got 2 sets here and cam gears I can lend you.

[Cubes]

I really hope it pans out well.

How did the leak down end up?

No boost leaks? (turbo to tb boost comparison turned out ok?)

Piston ring gap all ok?

What else really is there. :S

RBMAN had a similar issue with his RB30. It really struggled to make decent power.

[R32Abuser]

I really hope it pans out well.

How did the leak down end up?

No boost leaks? (turbo to tb boost comparison turned out ok?)

Piston ring gap all ok?

What else really is there. :S

RBMAN had a similar issue with his RB30. It really struggled to make decent power.

Hey cubes,

Haven't done a leak down test yet - Ive been to flat out with work to get anything done on the car plus its at the builders.

Borrowed and bought one exhaust and intake set of RB20DET camshafts to try. Probably won't work, but its worth a shot.

Trying new ignitor aswell just in case.

As far as the ring gaps are concerned, Ill get these off the builder on Monday as Im curious aswell. I would say they would be in the region on 0.02"-0.04". Judging by the piston slap when cold I would say around 0.04". Either way I don't think they're excessive.

Boost leaks - not sure of either. From driving it, it didn't seem like it had any boost leaks. But I guess I cant be too sure. Next time it jumps on the dyno, I'm going to be there so I will be more in the loop.

Failing all this, the head is coming off...

Then pending what is found from that, E85 may be the only option.

Got any contact details for RBMAN or know of what he did to fix it. Did he ever track down the problem?

Cheers,

David

[DVS JEZ]

Any updates David

[Rolls]

Think he is waiting for the builder to put the cams (rb20) in still, pretty busy by the sounds of it.

[R32Abuser]

Think he is waiting for the builder to put the cams (rb20) in still, pretty busy by the sounds of it.

Yup

Cams should be in the motor at the moment. Awaiting dyno time (for free)...

Will update as soon as I know more!

[Bl4cK32]

do you have the car, or has it been sitting in their workshop?

Id be telling them to f**k off by now for wasting your time. Surely the engine would be covered somehow, if someone stuffed the build, much the same as if you had a std engine built that went pop.

Engines not running right, looks like its our f**kup so we'll shift it aside and deal with it later.

[R32Abuser]

UPDATE

Engine has had the following changed and is sitting waiting for dyno time:

Another CAS sensor (builder just wanted to make sure it wasn't the issue by trying a 100% working item)

Removed RB25DE (R32) camshafts and Installed RB20DET camshafts

Re-timed (using timing light)

Dump will be dropped if the motor pings on the next dyno run to rule out back pressure

I believe he has changed the ignitor pack

Builder said from his initial impression after the above parts where installed:

"Previously, on idle and throughout the rev range, the car would "pop/putter" alot instead of a nice clean flow of exhaust. Now since we have changed the items (listed above), the note is a lot cleaner and significantly less "poppy/puttery". Also, from an initial drive, the car feels alot more doughier than before. This doughier would reflect the feeling you would expect considering the level of timing (~8 degrees advanced max!) the motor has wound into it compared to how it previously felt."

The above I guess is nothing to be overly excited about, but I'd say at a guess its a step in the right direction.

The fact that the car feels a bit more doughier could reflect that originally the car may have been incorrectly timed. But it could also reflect many other things as well! So I'm not getting my hopes up...

At present, Im waiting for dyno time early to mid next week, where Ill find out if any of these changes have helped.

If not, I think the only option is to go to E85.

Even if we do take off the head, and find it is the head which is the problem (which I 100% doubt it is), then there isn't a whole lot else to do but go to E85. Im not going to a 26 head as there is too much to change, far too much expense, and defeating the original purpose of the build to keep it looking stock.

If its not the head, and pistons are all as I've measured and calculated, then there's not a whole heap else to try except changing the ancillaries to the ECU - ignitor, ECU itself etc. etc. I'll be validating all the calculations I've done if we take the head off but guess I'll cross that bridge when I come to it.

Either way, I'm going to stick with the current direction of getting the head taken off if the above fails to change the problem. Then I'll address what I will do from there on in regarding workshop time, dyno etc.

Why aren't things ever simple

Edited August 26, 2011 by R32Abuser

[Dale FZ1]

I'm unsure how you'd base-time the thing without using a timing light.

That aside, if the signal is not looking scattered after a change of CAS, sounds like a step in the right direction.

Better/more accurate ignition timing could well account for the different sound, and if it's running bugger all timing in the whole map then of course it will feel doughy. Sounds like a bit of mapping will help immensely. All being good it should take somewhere in the vicinity of at least 17-18 degrees at full load, which will make it stand up.

I don't recall the exact spec difference between the 25DE and 20DET cams, however neither are anything other than mild. So they should both work ok and give a fairly quiet engine note. At least he's considering that as an issue too.

Keep us posted

[R32Abuser]

I'm unsure how you'd base-time the thing without using a timing light.

That aside, if the signal is not looking scattered after a change of CAS, sounds like a step in the right direction.

Better/more accurate ignition timing could well account for the different sound, and if it's running bugger all timing in the whole map then of course it will feel doughy. Sounds like a bit of mapping will help immensely. All being good it should take somewhere in the vicinity of at least 17-18 degrees at full load, which will make it stand up.

I don't recall the exact spec difference between the 25DE and 20DET cams, however neither are anything other than mild. So they should both work ok and give a fairly quiet engine note. At least he's considering that as an issue too.

Keep us posted

Refering to the RB30DOHC pdf:

HCR32 RB20DET Camshafts

Duration IN 240 deg

EX 240 deg

Lift IN 7.8mm

EX 7.8mm

LCA IN 115 deg

EX 120 deg

HCR32 RB25DE Camshafts

Duration IN 240 deg

EX 232 deg

Lift IN 7.8mm

EX 7.3mm

LCA IN 111 deg

EX 118 deg

Red is obviously the variations between the two camshafts. The main difference is between the Lobe centre angle (LCA) which, from what I have read, a larger LCA value creates less valve overlap. If I think about it, having more valve overlap would allow more intake charge to enter the motor during the exhaust stroke which would allow more fuel to sit in the chamber for a given duration of time. Not 100% sure on the effect of this but one would think this would create a greater tendencey to pre-ignite on any hot surface. Could be VERY wrong in this regard however!

Yeh Im pretty sure he timed it before using a timing light. You would ASSUME!

From what I was told, the timing wasn't scattered before hand, or at least it wasn't horribly bad.

The problem was last time they tried to wind timing into it, it would ping...So he left it with bugger all timing to make sure it would ping as least as possible.

Edited August 26, 2011 by R32Abuser

[Rolls]

pre ignition isn't detonation, different problems different causes.

[R32Abuser]

Agreed

But with that in mind, why will cams with a wider LCA have a lesser tendencey to knock/ping etc.?

Fair few blokes on here have reported that the 25DE cams have caused the motor to be more prone to pinging.

Any further ideas on what I have said above or new theories?

Like I said I'm simply hypothesizing