Jump to content
SAU Community

Recommended Posts

Hi,

Just installed new rb25 engine (after rebuild) with rb26 bottom end, wiseco forgies and HKS 256/8.8 in/ex camshafts.

The car idles with vacuum gauge reading ~ -0.43...-0.45 kpa which seems a bit low (usually ~0.6). I know that aftermarket cams can bring the vacuum down -- is this figures ok?

The second problem was that after initial ignition and fuel pressure tuning the car idles quite lean 17-18 AFR. Vacuum leakes where not found... Can cams cause this?

Have the cams been dialled in, that vacuum isnt too bad, as it sounds like it hasnt been tuned yet. When you say ignition and fuel pressure tuning, what do you mean exactly? Stock ecu?

the cams was installed with stock camgears -- so they have not been dialed in with a special procedures. as i read in this forums tomei poncams give the best result in default position. hks have very similar to tomei figures so i assumed it`s true for hks too.

ignition tuning is rotating the CAS with a ignition light to get 15 degrees on the crank pulley at idle.

fuel pressure tuning was setting the base fuel pressure at sard fpr (it was brand new and was set to 4 bar instead of 3bar -- but with 4 bar the idle was better).

ecu is power fc.

Tomei grind their cams at a lobe centre angle that is optimum for their bigger duration to give the right amount of overlap, this allows you to use stock cam pulleys. The HKS cams are ground to standard lobe centre angles, with increased duration the HKS items will be causing too much overlap hence the worse vacuum and the need to dial them in with adjustable cam pulleys.

ok, i understand how to dial in exhaust cam as it is possible to install adjustable cam gear on it, but what to do with intake camshaft -- it has nvcs gear so it can not be adjusted...

intake is adjustable fron the factory . take it out and look at the back of the cam gear or get one of these

http://www.trademe.co.nz/Trade-Me-Motors/C...n-293718049.htm

i read somewhere years ago it can be difficult to set mixtures at idle with big cams.

however, ur cams arent too aggressive, it may need further checking with the afr's u mentioned.

if its a stock computer ur kidding urself expecting it to run like this :thumbsup:

rb26 bottom end? changed stroke/cc etc? this will also not help the poor old stock ecu if thats whats still running(trying to run) it.

if its a stock computer ur kidding urself expecting it to run like this :thumbsup:

rb26 bottom end? changed stroke/cc etc? this will also not help the poor old stock ecu if thats whats still running(trying to run) it.

it`s not stock, it`s power fc as i mentioned before, so it`s not a big problem.

Tomei grind their cams at a lobe centre angle that is optimum for their bigger duration to give the right amount of overlap, this allows you to use stock cam pulleys. The HKS cams are ground to standard lobe centre angles, with increased duration the HKS items will be causing too much overlap hence the worse vacuum and the need to dial them in with adjustable cam pulleys.

this is not true, please see the follwoing links for comparison:

Tomei Factory Camshaft Specs

HKS Camshaft Specs

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I got back to Japan in January and was keen to get back on track as quickly as possible. Europe is god-awful for track accessibility (by comparison), so I picked up a first-gen GT86 in December just to have something I could jump into right away. The Skyline came over in a container this time and landed in early January. It was a bit battered after Europe, though—I refused to do anything beyond essential upkeep while it was over there. The clutch master cylinder gave out, and so did the power steering. I didn’t even bother changing the oil; it was the same stuff that went in just before I left Japan the first time. Naughty. Power steering parts would’ve cost double with shipping and taxes, so knowing I’d be heading back to Japan, I just postponed it and powered through the arm workout. It took a solid three months to get the car back on the road. Registration was a nightmare this time around. There were a bunch of BS fees to navigate, and sourcing parts was a headache. I needed stock seats for shaken, mistakenly blew 34k JPY on some ENR34 seats—which, of course, didn’t fit—then ended up having the car’s technical sheet amended to register it as a two-seater with the Brides. Then there’s the GT86. Amazing car. Does everything I want it to do. Parts are cheap, easy to find, and I don’t care what anyone says—it’s super rewarding to drive. I’ve done a few basic mods: diff ratio, coilovers, discs, pads, seat, etc. It already had a new exhaust manifold and the 180kph limiter removed, so I assume it’s running some kind of map. I’ve just been thrashing it at the track non-stop—mostly Fuji Speedway now, since I need something with higher speed after all that autobahn time. The wheels on the R34 always pissed me off—too big, and it was a nightmare getting tires to fit properly under the arches. So I threw in the towel and bought something that fits better. Looks way cleaner too (at least to me)—less hotboy, less attention-seeking. Still an R34, though. Now for future plans. There are a few things still outstanding with the car. First up, the rear subframe needs an overhaul—that’s priority one. Next, I need to figure out an engine rebuild plan. No timeline yet, but I want to keep it economical—not cutting corners, just not throwing tens of thousands at a mechanic I can barely communicate with. And finally, paint. Plus a bit of tidying up here and there.  
    • Nope, needed to clearance under the bar a little with a heat gun, a 1/2" extension as the "clearancer", and big hammer, I was aware of this from the onset, they fit a 2.0 with this intake no problems, but, the 2.5 is around 15mm taller than a 2.0, so "clearancing" was required  It "just" touched when test fitting, now, I have about 10mm of clearance  You cannot see where it was done, and so far, there's no contact when giving it the beans Happy days
    • It's been a while since I've updated this thread. The last year (and some) has been very hectic. In the second-half of 2024 I took the R34 on a trip through Germany, Italy, France and Switzerland - it was f*cking great. I got a little annoyed with the attention the car was getting around Europe and really didn't drive it that much. I could barely work on the car since I was living in an inner-city apartment (with underground parking). During the trip, the car lost power steering in France - split hose - and I ended up driving around 4,000kms with no power steering.  There were a few Nurburgring trips here and there, but in total the R34 amassed just shy of 7,000kms on European roads. Long story short, I broke up with the reason I was transferred to Europe for and requested to be moved back to Japan. The E90, loved it. It was a sunk cost of around EUR 10,000 and I sold it to a friend for EUR 1,500 just to get rid of it quickly. Trust me, moving countries f*cking sucks and I could not be bothered to be as methodical as I was the first time around.
    • I assume clearances were all a-okay?
    • Shock tower brace is in +5Kw....LOL  
×
×
  • Create New...