Adjusted Stock RB26 Cams

Hi all!

I recently had my R32 GTR MOT'd here in the UK and had a wee look into its service history. Luckily I have everything single piece of it, although all in Japanese. With the help of google translate I was able to cipher out that a pair of adjustable cam gears had been installed and the cam timing adjusted.

The stated figures are: IN +4, EX -12.

Am I correct in believing that the lobe separation angel has now decreased creating more overlap? I am a little confused to why they have done this as from what I have learned, the inlet cam makes more of a difference? Can I also confirm that a large overlap can also be detrimental in a turbo charged engine?

The car is running the stock ECU, MAF's, injectors, fuel pump etc but is running stock R34 GTR turbos. I have an AEM wideband gauge to monitor the AFR - all seems good right now.

Many thanks in advance!

Nick

I would read that as the inlet being advanced and the exhaust retarded, which would increase the lobe separation angle and decrease overlap - the period both valves are open. This may have been done to improve low to mid range, especially with a camshaft upgrade - anyone more knowledgable to comment?

That said, I'd suggest before taking that as gospel, you verify the camshafts are actually stock - can't really see the point of verniers if they are - and what the actual timings are - the notation may refer to the vernier markings required to have them on the 'true' OEM timing, rather than a change from the OEM.

We used to get great gains in response and mid range on stock cam rb26's with adjustable gears.

But I used to advance the inlet cam around 12 crank degress, and retard the exhaust 1-4 crank degrees. If you had larger turbos, you could run the turbos into surge and get a bit of "shuffling" if they were any bigger than n1 turbos.

You sure its a stock ecu with a stock tune, and not a chipped or nistuned car?