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Leroy Peterson    1,197
Stock camshafts on built motor

This isnt for an RB engine, but I thought it might help others who could be curious or for future reference.

Does anyone have an experience with built motors running OEM-spec cams?

My SR20 has had a lot of porting work done, plus Ti retainers/upgraded valve springs, aftermarket exhaust manifold, bigger turbo etc. Has been running big cams in the past and I'm really curious to see how much more "driveable" and how much low-down can be improved by going back to stock cams.

I am looking for some ideas or feedback before I commit money to OEM cams + installation + re-tune.

For reference: current cams are 272 duration, 11/12mm lift. OEM are supposedly 248 duration, 10mm lift.

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Dale FZ1    120

Bit of a loaded question without disclosing turbo size/spec and static CR, and even fuel type + ignition mapping "down low".  All those things will play a part.

Without committing too much $$ you could try a dyno session and adjust the current cam phasing to see if it will build better torque at lower rpm.

Otherwise on topic, there's plenty of SR (and RB) owners running more basic engine upgrades with just a turbo change and OEM cams who are very happy and don't need to rev the tits off them to get satisfactory performance. Turbo spec will have a massive impact on how the engine performs over its whole rpm range.

 

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Leroy Peterson    1,197
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  • GTX2867. +0.2 comp ratio. 98 fuel. FWD/AWD SR, so not really comparable to RWD for power figures

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    Dale FZ1    120

    Not thinking about rwd vs awd or the actual power number.

    Turbo "should" perform ok. What turbine A/R did you go with?

    Also whatever your tuner has done with ignition timing low-mid range has a massive influence.

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    Leroy Peterson    1,197
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  • 0.86

    The engine specs have been through 3 different tuners, one leaned it out pretty heavy at 2500rpm and it was better but still not nice. Cams were dialled in by engine builders as per spec sheet provided.
    Not sure on timing.

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    Dale FZ1    120

    Tuners and engine builders are not always operating on the same plane.  Or even a high plane.  And it's no good if they don't understand what you're trying to achieve when recommending specs.  So lots of opportunity to miss the mark.

    Making an engine run lean where you're trying to make it "come on" is counter productive IMO.  And ignition timing is very important, so if you can, you should look at the ignition map and learn.  There's a lot of easy to access net resources, try hp tuners for a look.

    Suggest a change to 0.6 turbine housing will help with the mid range boost response, at the expense of some top end revs

    If you're running a 4wd Bluebird or Pulsar (guessing from earlier post?) you probably want (ie definitely need) bulk mid range anyway.

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    Skepticism    16

    272 cams are too big for an SR on a gtx28... as in, many many sizes too big. If this was a drag car or you wanted to win WTAC, and you had a GT35 to spool up then it's a different story.

    On the other hand, with your setup OEM cams are too extreme in the other direction. Given the GTX2867 with (as Dale pointed out) quite a large turbine housing for a 2L, which entails spooling up a bit later anyway.

    Unless you're revving much higher than standard, 256 (poncams etc) are likely the best option, especially if you want to retain better driveability for street duties. If you're concerned about power, check out this build log - 264s were switched out for 256 duration poncams to get a better powerband. The end result was still 351kW on a GTX3071r  http://www.trak-life.com/trak180-redemption/

    bear in mind that this is an unregistered track car, so streetability wouldn't have been a concern in any way.

     

    Edited by Skepticism

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    Leroy Peterson    1,197
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  • On 08/07/2017 at 0:13 PM, Dale FZ1 said:

    Suggest a change to 0.6 turbine housing will help with the mid range boost response, at the expense of some top end revs

    If you're running a 4wd Bluebird or Pulsar (guessing from earlier post?) you probably want (ie definitely need) bulk mid range anyway.

     

    1 hour ago, Skepticism said:

    On the other hand, with your setup OEM cams are too extreme in the other direction. Given the GTX2867 with (as Dale pointed out) quite a large turbine housing for a 2L, which entails spooling up a bit later anyway.

    Unless you're revving much higher than standard, 256 (poncams etc) are likely the best option, especially if you want to retain better driveability for street duties. If you're concerned about power, check out this build log - 264s were switched out for 256 duration poncams to get a better powerband. The end result was still 351kW on a GTX3071r  http://www.trak-life.com/trak180-redemption/

    bear in mind that this is an unregistered track car, so streetability wouldn't have been a concern in any way.

     

    I appreciate the input guys, but I think you're misunderstanding my question and why I'm asking.

    I'm not chasing better turbo response, or to reduce lag. This is simply sub-3000rpm driveability and lower idle is what I'm trying to improve. I dont care about peak power, and I'm aware smaller cams will shift the power band. I'm looking for input running OEM cams on a built valve train.

    The GTiR head is mechanical/solid (not lash/hydraulic like regular SR heads) so camshaft choices are generally aggressive. The car was previously running Tomei 260 Procams and it wasn't any friendlier to drive. This is a track-focused car, but I do drive it on the street. And you're right Dale, I should speak to my tuner about  the setup and potential improvements.

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    Komdotkom    5

    It will be fine. You have lower ramp rates and a lower overall lift so the only effect it will have on the valve train is a positive one. The upside to OEM cams is they are generally ground to a very high standard unlike a lot of aftermarket cams and therefore are likely to not chew up your rocker arms. It's worth checking your spray bars while its apart as SR's have a tendency to clog up.

    270 is a big cam on a low comp engine, remember that you are lowering your dynamic comp with large cams that have a longer period of overlap and relying on positive pressure in the manifold to generate any real efficiency. Furthermore the effects of camshaft duration are magnified on smaller displacement engines.

    You will end up with higher cylinder pressures and peak torque will shift, so your tune will need to be adjusted. 

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    Dale FZ1    120
    37 minutes ago, Leroy Peterson said:

    I'm not chasing better turbo response, or to reduce lag. This is simply sub-3000rpm driveability and lower idle is what I'm trying to improve. I dont care about peak power, and I'm aware smaller cams will shift the power band. I'm looking for input running OEM cams on a built valve train.

    Understood.

    By way of a recent experience that may help: We've shaken down the Emo after a prolonged upgrade/build period.  I appreciate that a 4G63 - SR20 comparison is not apples-apples, but it is a 4wd platform that counts for heaps.

    No porting, but lightweight retainers, upgraded springs, and (against my advice) some Jap cams advertised specs around 270.  Actual cam doctor measurements showed significant variance from advertised, and staggered/unequal between inlet - exhaust.

    Turbo choice budget Kinugawa TDO6SL2-20G split pulse 10.5cm.

    Result on 24psi bleeding to 22psi by 7000rpm was 380awhp, monster mid range torque from 4000rpm.  Idles good and smooth at 900rpm. Doughy sub 3000rpm. We have assessed that OEM cams would probably have brought the useable torque floor down 500rpm, and manipulating boost control probably seen no loss at higher rpm.

    Car was second quickest in its category (behind a modified R35 GTR) even though we were just shaking it down.  So it had "enough", and we aren't focused on hp numbers either, just a quick/reliable track car.

    SR with big duration cams really requires revs, and those things have a deserved reputation for spitting lash pads when using the revs.  Talk to the people doing your work, but I agree with komdotcom, OEM cams will only make the cam train work with much less stress for probably as good a result. 

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    I think people should look at all the valve timing evens which means more than just cam lift and valve seat to seat duration . Quite a few aftermarket cams are compromised so that they drop in with few or no modifications . Obviously priority no 1 is not killing the standard valve train .

    I'll see if I can link the Tomei USA page where you can look at all the numbers ie lobe center lines and overlap timing for their cams . 

    https://www.tomeiusa.com/cam_spec/cam_spec_list-e.html

    I've never looked at aftermarket SR20 cams but if they are anything like RB25 Poncams they'll have a lot more overlap than the factory standard cams .

    Cheers A . 

    Edited by discopotato03

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    Leroy Peterson    1,197
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  • Yeah, i know advertised cam specs are to be used as a guide only. Most cam manufacturers specify if springs and retainers are recommended with the cam, so i dont think the top shelf camshafts compromise performance for the sake of stock valvetrain.

    With the GTiR head being lash type rockers, tomei poncams are not compatible, only Procams can be used. And with most GTiR builds being wannabe GTRs with 600hp good for about 2 launches, mot available cams are aggressive. I did find a mild cam but it was even less duration and lift than OEM!

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    Komdotkom    5

    If you want to have an informed conversation about a good cam package for your car and its specific use(s), I suggest that you go and see Clive at Clive Cams in Ferntree Gully. 

    There are quite a few decent grinds from smaller players (not big jap tuning companies) for the SR which are quite good, a mate has one of the old Super Tourer grinds in his IPRA 1600 and it's fairly decent at low RPM for a 306 duration (advertised) cam.

    I still reckon you are better off with stock cams though, you turbo isn't big enough to make it worthwhile. I'd much rather have a punchy 230kw car than a laggy 270kw car.

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    Leroy Peterson    1,197
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  • I've been to Clive cams before for replicating a grind and their machines were limited to 10mm lift I think.
    But yeah, I will speak to tuner and then hunt down a set of OEM cams. If I'm not happy with the outcome, I'll probably revert back.
    Thanks for contributions.

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