Jump to content
SAU Community

Recommended Posts

Hi again, I'm getting ready to have the cams I bought installed into the head (motors being built up as we speak) and I'm wanting some suggestions...

I bought a pair used from a member that were suppose to be 264 9.7 cams, but he sent me a 264 and a 256, 9.7, saying the other 264 was rust pitted.

So now I have a 264 and a 256. QUESTION: considering I'll be using my Electramotive TEC2 standalone, the CAS drive is not important to me, so which would you install where? (I forget which one has the CAS drive gear in it)

Like I said, I will not be installing the CAS mechanism, so either cam can go into either side... so which would be better where??

Thanks for the help

joel

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/
Share on other sites

Hi Joel, I would go with 256 inlet and 264 exhaust, I have seen this (longer duration exhaust) work on a number of GTR's. What's the lift on each cam? My RB31DET has 268 inlet and 272 exhaust, both at 10.5mm lift.

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-932662
Share on other sites

Hi Joel, I would go with 256 inlet and 264 exhaust, I have seen this (longer duration exhaust) work on a number of GTR's.  What's the lift on each cam?  My RB31DET has 268 inlet and 272 exhaust, both at 10.5mm lift.

Thank You Sydneykid for the responce. The cams are both only 9.7 on the lift. I had the head set up on a end mill (for the lobe clearnce needed), and the notchs came out sweet ....

I also have the Tomie adj cam wheels to go with the cam upgrade, so if you would, please give me some advice on where to start with the placement of the cams.

thanks again

joel

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-932685
Share on other sites

Duration is the amount of the time the valves are open for.

Lift is how far the valves open. Consider it as the washer in your tap; as you turn the tap on further, the washer lifts higher to let more water through. With the higher lift cams, the valves travel further into the the combustion chamber, thus the modification to the head is required for clearences.

As with longer duration cams, higher lift cams have their advantage in the higher rpm and hurt low rpm response. However, how much this rule effect the forced induction engines always puzzled me. Ben is running a huge turbo with crazy cams and has amazing response, does 400cc make that much difference...?

Back to you SK.

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-933140
Share on other sites

Thank You Sydneykid for the responce. The cams are both only 9.7 on the lift. I had the head set up on a end mill (for the lobe clearnce needed), and the notchs came out sweet ....

I also have the Tomie adj cam wheels to go with the cam upgrade, so if you would, please give me some advice on where to start with the placement of the cams.

thanks again

joel

Hi Joel, 256 @ 9.7mm and 264 @ 9.7mm is a good combination, if tuned properly it will make power and run very nice with that combo.

As for cam timing all engines are different, I start at 1-2 degrees advanced on the inlet timing and 3-4 degrees retarded on the exhaust. The exhaust timing makes the most obvious difference to the power, but don't ignore the inlet. It helps the response as well.

Hope that helps :thumbsup:

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-933161
Share on other sites

SK,

Interesting that you've found that shorter duration inlet cam works better than the reverse!

Tomei sell two PONCAM setups for the RB26:

Type A - 260 degree, 9.15mm lift intake / 252 degree, 9.15mm lift exhaust

Type B - 260 degree, 9.15mm lift intake / 260 degree, 9.15mm lift exhaust

I went for the Type B set for my car, but was wondering what the theory behind running a larger duration exhaust cam was?

Wouldn't it be best to have a longer duration intake cam to fill the cylinder and push out the gasses out of the exhaust valves as opposed to having a longer duration exhaust cam and relying on scavenging vacuum to suck out the gasses?

Hmmmm...

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-933302
Share on other sites

SK, Interesting that you've found that shorter duration inlet cam works better than the reverse!

Tomei sell two PONCAM setups for the RB26:

Type A - 260 degree, 9.15mm lift intake / 252 degree, 9.15mm lift exhaust

Type B - 260 degree, 9.15mm lift intake / 260 degree, 9.15mm lift exhaust

I went for the Type B set for my car, but was wondering what the theory behind running a larger duration exhaust cam was?

Wouldn't it be best to have a longer duration intake cam to fill the cylinder and push out the gasses out of the exhaust valves as opposed to having a longer duration exhaust cam and relying on scavenging vacuum to suck out the gasses?

Hmmmm...

Hi Merli, I didn't really specifically choose the cams, they were available at the time at right price. I was really more interested in the higher lift (and lower price), than the small diff in duration. :cooldance

I have heard and read that longer duration inlet is better for the reasons you put. And they certainly sound valid. I have also heard and read that longer duration exhaust is better, based on the fact that the inlet is under direct boost and the exhaust isn't. So you have to run longer duration on the exhaust to match. I have also heard and read that a longer duration inlet cam makes the engine lumpy, so its not a matter of running a LONGER exhaust duration, but in fact running a SHORTER inlet duration. :confused:

There are plenty of arguments either way, I really have no idea which is correct as I haven't done or seen a proper comparison. I suspect that there may be a boost threshold where the longer inlet duration argument has substance. But I have no proof, it's just a suspicion. :headspin:

Most of the engines I am involved with, I suggest the same duration for both inlet and exhaust cams. Maybe that's the right answer. ;)

Link to comment
https://www.sau.com.au/forums/topic/45784-cam-question-rb26/#findComment-934655
Share on other sites

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

    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
    • But first....while I was there, I also swapped across the centre console box for the other style where the AV inputs don't intrude into the (very limited !) space.  Part# was 96926-4GA0A, 284H3-4GA0B, 284H3-4GA0A. (I've already swapped the top 12v socket for a USB bulkhead in this pic, it fit the hole without modification:) Comparison of the 2: Basically to do the console you need to remove the DS and PS side console trim (they slide up and back, held in by clips only) Then remove the back half of the console top trim with the cupholders, pops up, all clips again but be careful at the front as it is pretty flimsy. Then slide the shifter boot down, remove the spring clip, loose it forever somewhere in the car the pull the shift knob off. Remove the tiny plastic piece on DS near "P" and use something thin and long (most screwdrivers won't fit) to push down the interlock and put the shifter down in D for space. There is one screw at the front, then the shifter surround and ashtray lift up. There are 3 or 4 plugs underneath and it is off. Next is the rear cover of the centre console; you need to open the console lid, pop off the trim covering the lid hinge and undo the 2rd screw from the driver's side (the rest all need to come out later so you can do them all now and remove the lid) Then the rear cover unclips (6 clips), start at the top with a trim tool pulling backwards. Once it is off there are 2 screws facing rearwards to remove (need a short phillips for these) and you are done with the rear of the console. There are 4 plugs at the A/V box to unclip Then there are 2 screws at the front of the console, and 2 clips (pull up and back) and the console will come out.
    • So, a bit of a side trip, but one that might be interesting for people with JDM cars and japanese head units. I know @Pac previously posted about a carplay/android auto adapter he installed which used the AUX input, and @V35_Paul put in one of the Tesla style units that replace both screens. The option I went with was a Lsait LLT-YF-VER5.87_2 (https://www.alibaba.com/product-detail/Lsailt-8GB-Android-Multimedia-Interface-for_1601187633672.html). Price was $1,150 for a single unit although they are much cheaper if you are willing to buy 2....$857ea. Make you you get the version 2 not version 1, it is faster and has a better UI - this is the manufacturer listing: http://www.lsailt.com/product/348.html. BTW if you've never bought from Alibaba before, don't be concerned....these guys can't stay in business unless they are responsive, ship fast etc, they were excellent (probably faster shipping than most local places) So, this was my task for a lazy Sat afternoon....looks complex but was all done in a few hours (it probably helps that I had some of it apart before so it was a bit familiar). I also decided to add a HD USB drive recorded at the same time and the unit also supports an aftermarket reverse cam (if you don't want to retain factory) and also AV in and HDMI out It looks much worse than it is, in fact in was genuinely all plug and play (no custom wiring at all). This video was pretty good (skipped a few steps), unfortunately they are an Aussie seller but no longer sell this unit (I guess Carplay/AA adapters are easier to install and much cheaper) https://www.youtube.com/watch?v=T5hJfYOB8Dg
×
×
  • Create New...