Poncam B Out By A Tooth ? What Does It Mean ?

[cobrAA]

I'm having a very lumpy idle, way more than before, I thought it was the nistune, but i just got back from the tuning with new haltech ecu. Is it better ? Yes, but still lumpy.

I also made serious lost of power than 2 yr ago ( about 15% less), my tuner think it could be that my Poncam is missing a tooth. But to be honest, I'm unsure what it means and.. what can I do to correct it ? do i need to start thinking about buying a new set of cams ?

thanks!

[GTRPSI]

It means your cam timing is out 1 tooth.

Take off the front cover, rotate the engine to top dead center, cam gear marks should line up with rear cover marks exactly.

If the gears are out 180 degrees, rotate the engine one more revolution, 1 crank rotation = 180 degrees of cam rotation.

If its wrong, your out X amount of teeth, you need to loosen the cam belt and reposition your cams the right way.

[blind_elk]

If you install high lift, large overlap cams, then the idle is going to be lumpy. Not a lot you can do about it.

[Ben C34]

If you install high lift, large overlap cams, then the idle is going to be lumpy. Not a lot you can do about it.

That's true.

But type b are hardly high lift or large overlap.

[GTRPSI]

Could be lumpy because of the tune, a lot of lump can be pulled out by tuning.

[portaz]

Type bs are lumpy enough though if your used to stock idle anyway

[Sinista32]

2cents worth

- Type B's sound lumpy.

- Dyno results vary allot

however, if you have slipped a tooth then get it fixed now

if your tuner thought it had slipped a tooth then he shouldn't let you drive away without warning you of the potential consequences

[cobrAA]

That's true.

But type b are hardly high lift or large overlap.

Exactly, I dont consider these camshafts too aggressive, not to mention, I'v ebeen runing these for 3 summers now. so I know how they should sound.. i just always thought it was my tune with nistune who wasnt good hence why i went with the haltech.

It means your cam timing is out 1 tooth.

Take off the front cover, rotate the engine to top dead center, cam gear marks should line up with rear cover marks exactly.

If the gears are out 180 degrees, rotate the engine one more revolution, 1 crank rotation = 180 degrees of cam rotation.

If its wrong, your out X amount of teeth, you need to loosen the cam belt and reposition your cams the right way.

So basicly.. if it's off, it's not like I have to buy a new set of camshaft or go for a ''head'' rebuilt ?

Type bs are lumpy enough though if your used to stock idle anyway

2cents worth

- Type B's sound lumpy.

- Dyno results vary allot

however, if you have slipped a tooth then get it fixed now

if your tuner thought it had slipped a tooth then he shouldn't let you drive away without warning you of the potential consequences

I have great respect for my tuner but he is not a mechanic ( nor I am, I believe in '' if you don't know what to do, don't try and do it, but that doesnt means I don't have the right to understand whats going on with my car ) and i left the dyno at 2h am, so at this point we couldn't diagnotic the problem. The car run great with the new tune, it just that it don't make the low-end power i was used to and the top-end theres a lost of 75 whp, but mid-range sound ''about right'' compared to last year tune.

[cobrAA]

btw, thanks for the reply

[Ben C34]

It is very easy to check

http://img.photobucket.com/albums/v688/Isijappanisi/timingrb26.jpg

You will need to reset the ignition timing with a timing light once done.

[Kinkstaah]

For what its worth, I have type B's and a haltech (on a rb28).

After a tune, I have idles which can be described as uh, REAL LUMPY. I mean, car-shakingly lumpy. In every instance it was actually due to it simply running very lean on idle (~17:1 AFR). I was able to add a little to get this to 14.7-15:1 and the lumpiness effectively disappeared.

If all that happened was you got your tune, it may simply be a bit lean at idle.

[Gramps32]

That's interesting to me, cheers

I run type B's and Haltech PnP on my 26 and it's also noticeably lumpier at idle

- thanks will ask my tuner next time

[Ben C34]

That's interesting to me, cheers

I run type B's and Haltech PnP on my 26 and it's also noticeably lumpier at idle

- thanks will ask my tuner next time

I don't think we can compare a 25 to a 26 because of vct.

If you activate vct at idle the 25 will also be heaps lumpy.

[Gramps32]

Thanks Ben it's good to distinguish so we don't get confused and lumpy them all into one block - lol

not in my Signature but I also own a GTR which I was referring to in the above post

[andre_gtr]

My car also idles lumpy with b's but compression very low maybe test compression to see if its low mine sits at 100psi

[cobrAA]

Compression test came out to 145-150-155-160-160 so its OK and was rebuilt less than 15k kms.

My mechanic did the timing test and here's the result: Exhaust is spot on. However intake was a bit less than a teeth.. maybe 80% of a teeth. I was told.. if it would be off, BOTH cam should be, not just one.

whats your take on this ?

[Ben C34]

If the crank pulley was off then of course both cams would be off. But surely it's pretty obvious that only one cam could still have been one tooth out.

WTF is 80% of a tooth?

Why isn't he talking in degrees? Did he even use a degree wheel or just eyeball?

[cobrAA]

If the crank pulley was off then of course both cams would be off. But surely it's pretty obvious that only one cam could still have been one tooth out.

WTF is 80% of a tooth?

Why isn't he talking in degrees? Did he even use a degree wheel or just eyeball?

we used eyeball since we were in a driveway. while the exhaust was 100% spot on, the intake was a bit off.

[Ben C34]

Ok. I misunderstood when you said "mechanic did the timing test"

As the 100 percent correct way to check is with a degree wheel and dial indicator . I assumed that's what the mechanic did.

Are they adjustable gears?

[cobrAA]

Ok. I misunderstood when you said "mechanic did the timing test"

As the 100 percent correct way to check is with a degree wheel and dial indicator . I assumed that's what the mechanic did.

Are they adjustable gears?

yup tomei's one. I will be bringing the car at the shop next year but i wanted to do some backyard testing to have a ''feel'' of whats going on with my car.

Edited June 19, 2014 by cobrAA